Role of Insulin & Glucagon in Cellular Metabolism (PDF)

Role of Insulin & Glucagon in Regulation of Cellular Metabolism & Metabolic Homeostasis Learning Module Developed & Presented by: Anamika Sengupta, PhD, M.Ed. Associate Pr...

Role of Insulin & Glucagon in Regulation of Cellular Metabolism & Metabolic Homeostasis Learning Module Developed & Presented by: Anamika Sengupta, PhD, M.Ed. Associate Professor –Biochemistry Dept. of Health Sciences Education & Pathology University of Illinois College of Medicine, Peoria campus LEARNING OBJECTIVES & READING 1. Define metabolic homeostasis and summarize the role of specific organs in the maintenance of metabolic homeostasis. 2. Contrast the sources, broad functions, cell signaling cascades activated by the two pancreatic hormones insulin & glucagon. 3. Briefly summarize the synthesis & maturation process of insulin & glucagon. 3. Compare the role of insulin and glucagon in the maintenance of blood glucose homeostasis. 4. Diagram the mechanisms by which insulin & glucagon regulate different metabolic cycles for the maintenance of metabolic homeostasis RECOMMENDED READINGS: Scholar Rx module entitled “Role of Insulin , glucagon in regulation of fuel metabolism & metabolic homeostasis” Lippincott® Illustrated Reviews: Biochemistry, 8e; Chapter 23; Metabolic effects of insulin and glucagon; available on LWW health library; https://meded-lwwhealthlibrary- com.proxy.cc.uic.edu/content.aspx?sectionid=250324745&bookid=3073 Diagrams used in the presentation are mostly obtained from the recommended reading.  Metabolic Homeostasis: A balance between fuel availability, cellular usage & storage Organs involved in the maintenance of metabolic homeostasis Liver- Storage site for glycogen Adipose- Storage site for triglycerides Muscles- Characterized by high energy demand; utilizes fuels rapidly when active Brain: Regulates communication between tissue types through nerve impulses Endocrine organs: Produces hormones that initiate actions at target organs  Blood Glucose homeostasis Primary cellular fuel: Glucose Blood glucose homeostasis: Maintenance of glucose level between 80-100 mg/dL in the blood at all time. The Liver plays the most important role Insulin, Glucagon, Epinephrine & cortisol: Important hormonal role players in the process Insulin & glucagon: Antagonistic; Maintains blood glucose homeostasis during fed & fasting High blood glucose: Stimulus for insulin secretion; helps to store excess glucose from blood into tissues. High insulin production also shuts off glucagon secretion Low blood glucose: Stimulus for glucagon secretion; helps to release glucose from stored sites for maintenance of glucose homeostasis Insulin-The Anabolic Hormone Protein hormone; produced by the β cells of the pancreatic islets of Langerhans Composed of 51 amino acids arranged in as A & B chains, linked by disulphide bridges Made from inactive precursors called Prepro & proinsulin Insulin acts on target cells through membrane bound receptor tyrosine kinase. Increases glucose absorption by peripheral tissues namely muscle & adipose Anabolic hormone; Promotes cellular synthesis of fatty acids, cholesterol, proteins & glycogen and oxidation of glucose to pyruvate Glucagon-The Catabolic Hormone Preproglucagon Glucagon Proglucagon (Ribosomes of RER of (29AA, secreted after (Lumen of ER) proteolytic cleavage) α cells; 160AA) Protein hormone compose of 29 amino acids; produced by the α cells of the pancreatic islets of Langerhans. Prepro & pro forms are the inactive precursors Acts on target cells through G-protein coupled receptors (GPCRs); target organs are the liver & adipose; muscles lack glucagon receptors Increases glucose secretion in the blood by inducing hepatic glycogenolysis & gluconeogenesis for maintenance of blood glucose homeostasis during fasting & starvation. Catabolic hormone; promotes lipolysis, fatty acid oxidation, gluconeogenesis, glycogenolysis & proteolysis NUTSHELL: Insulin & glucagon are antagonistic  Glucagon regulates catabolic cycles by two mechanisms Transcriptional regulation Enzyme activation by phosphorylation ACTIVATES INDUCES transcription of Glycogen phosphorylase (Glycogenolysis) PEP-CK (Gluconeogenesis) F 1,6 bisphosphatase (Gluconeogenesis) Hormone Sensitive Lipase (Lipolysis) REPRESSES transcription of Glucokinase (Liver) INHIBITS PFK-1 (Glycolysis) PFK-1 via PFK-2 (Glycolysis) Pyruvate kinase (Glycolysis) Glycogen Synthase (Glycogenesis) Pyruvate kinase (Glycolysis) Acetyl CoA Carboxylase (Fatty acid synthesis) Insulin regulates anabolic cycles by activating the specific rate limiting enzymes via dephosphorylation Insulin indirectly reduces the levels of cellular cAMP Low cAMP inhibits activation of cellular PKA (downstream cascade of GPCR) Phosphorylation cascades are turned off Insulin activates cellular protein phosphatases which, dephosphorylate rate limiting enzymes of catabolic cycles turning them OFF dephosphorylate rate limiting enzymes of anabolic cycles turning them ON  INSULIN Vs GLUCAGON INSULIN GLUCAGON 1. Produced from pancreatic beta cells 1. Produced from pancreatic alpha cells 2. Released in response to HIGH blood glucose 2. Released in response to LOW blood glucose ( during (in FED state) FASTING & STARVATION) 3. ANABOLIC hormone 3. CATABOLIC hormone 4. INDUCES storage of excess fuels available in 4. INDUCES mobilization & oxidation of fuels (glycogenolysis, lipolysis, fatty acid oxidation, blood by inducing glycogenesis, fatty acid gluconeogenesis, proteolysis) synthesis, protein synthesis, glycolysis 5. Acts on target cells through G-protein coupled 5. Acts on target cells through receptor receptors tyrosine kinase 6. Acts by increasing cellular cAMP levels which 6. Acts by decreasing cellular cAMP levels and activates downstream phosphorylation cascade via increasing cellular phosphatases activating PKA 7. Activates anabolic cycles by 7. Activates catabolic cycles by phosphorylation of the dephosphorylation of the rate limiting rate limiting enzymes enzymes Let’s apply the concepts learnt: Tina, a 7-year-old girl missed breakfast at school this morning. It is 11am now. Tina is sitting in her classroom dreaming about lunch! She is very hungry! Tina’s blood glucose level: slightly below homeostasis (80-100 mg/dL) Tina’s blood insulin levels: Low Tina’s blood glucagon levels: High (stimulated by her low blood glucose levels & low insulin levels) Function of glucagon: High glucagon is breaking down liver glycogen to release glucose into her blood to prevent further fall of her blood glucose level Glucose released into blood is being utilized by RBCs & neurons (exclusively glucose dependent) as well as other peripheral tissues Glucagon would also initiate mobilization of fats from adipose tissue into blood & fatty acid oxidation in other cells types for ATP production (under limited blood glucose availability)  Tina’s wait is finally over. It is lunch time. She runs to the school cafeteria and serves herself some pizza and a piece of cake. She is happy as she eats her lunch! Tina’s blood glucose level: shoots up as she begins eating Blood glucose above the homeostatic level is stimulating insulin release from her pancreatic beta cells High blood insulin levels would accelerate glucose absorption by adipose & skeletal muscles via increasing GLUT 4 translocation to the cell membrane. Insulin would also activate glycogen synthesis (via dephosphorylation of glycogen synthase) in the liver and muscles enabling storage of excess glucose from the blood into these tissues as glycogen. This would bring Tina’s blood glucose back to homeostatic levels ( 80- 100mg/dL) Insulin would also activate glycolysis for utilization of glucose for ATP production in most cell types; Insulin would inhibit break down of fats and proteins for energy production during the fed state When Tina was Hungry In a Nutshell After TINA eats lunch Low blood glucose Blood glucose peaks stimulates stimulated Glucagon release Primary secondary Insulin release pathway Activates enzymes pathway Stores excess blood Excess hepatic via phosphorylation glucose stored as glucose as Activates enzymes Liver glycogenolysis Lipolysis via dephosphorylation (from adipose) Glycogen (in muscle & liver) Lipid (adipose, liver) Releases Enzymes activated Glucagon Both pathways remove excess mediated glucose from blood glucose in by phosphorylation the blood Maintenance of Tissue specific Glucose Glucose oxidation of fats homeostasis homeostasis  THANK YOU Please reach out with any questions to me at [email protected] OR Stop by my office (B202) for a clarification chat Introduction to Body Systems and Homeostasis Block 1 Michael Caffrey, PhD Radhika Sreedhar, MD, MS  Conflict of Interest Statement The presenters do not have a financial interest, arrangement, or affiliation with any organization that could be perceived as a real or apparent conflict of interest in the context of the subject of this presentation. Land Acknowledgement We recognize and acknowledge that University of Illinois sits on the land of multiple native nations. We acknowledge and honor the original peoples of the Chicagoland area – the Three Fires Confederacy, Potawatomi, Odawa and Ojibwe Nations, as well as other Tribal Nations that know this area as their ancestral homeland, including the Menominee, Ho-Chunk, Miami, Peoria, and Sac and Fox. These lands were the traditional birthright of indigenous peoples who were forcibly removed and who have faced two centuries of struggle for survival and identity in the wake of dispossession. Let us acknowledge the ground on which we stand so that all who come here know that we recognize our responsibilities to the peoples of that land and that we strive to address that history so that it guides our work in the present and the future. We further acknowledge that this land is the current home to one of the largest urban Native American communities in the United States. Native people are part of Chicago’s past, present, and future, and it is our responsibility to acknowledge these Nations and to work with them as we move forward as a more inclusive institution. https://www.uillinois.edu/about/land_acknowledgement 3  Content Outline Introduction Block overview Discussion Structure and content Engaging with curriculum Assessments Program Evaluation Introduction Michael Caffrey Course Director [email protected] Radhika Sreedhar Course Director [email protected] Chad McCoy Course Coordinator [email protected]  Communication with faculty Office Hours- posted on calendar Feel free to drop by, but email in advance as we may be teaching or in clinic! Block 1: Body Systems and Homeostasis I Open Forum Review: https://docs.google.com/document/d/1MeKaEHSRPzk3Cev-OXQONwtlcKwVg6_4yA5GLkY4DrY/edit#heading=h.19vqgd1a1md7 https://docs.google.com/document/d/1MeKaEHSRPzk3Cev- https://docs.google.com/document/d/1MeKaEHSRPzk3Cev-OXQONwtlcKwVg6_4yA5GLkY4DrY/edit#heading=h.19vqgd1a1md7 OXQONwtlcKwVg6_4yA5GLkY4DrY/edit#heading=h.19vqgd1a1md7 Calendar: https://calendar.google.com/calendar/u/0/r/week/2024/8/19?pli=1 https://calendar.google.com/calendar/u/0/r/week/2024 https://calendar.google.com/calendar/u/0/r/week/2024/8/19?pli=1 /8/19?pli=1 Websites you Block 1: Body Systems and Homeostasis I Open Forum Review: should know https://docs.google.com/document/d/1MeKaEHSRPzk3Cev-OXQONwtlcKwVg6_4yA5GLkY4DrY/edit?usp=sharing https://docs.google.com/document/d/1MeKaEHSRPzk3C https://docs.google.com/document/d/1MeKaEHSRPzk3Cev-OXQONwtlcKwVg6_4yA5GLkY4DrY/edit?usp=sharing ev- https://docs.google.com/document/d/1MeKaEHSRPzk3Cev-OXQONwtlcKwVg6_4yA5GLkY4DrY/edit?usp=sharing OXQONwtlcKwVg6_4yA5GLkY4DrY/edit?usp=sharing Blackboard: http://uic.blackboard.com Syllabus: https://uofi.box.com/s/n2fmykix8gdxte9fwwef6f1wsn4hltim Syllabus: https://uofi.box.com/s/n2fmykix8gdxte9fwwef6f1wsn4hlti https://uofi.box.com/s/n2fmykix8gdxte9fwwef6f1wsn4hltim m  Poll You are not sure where the session is going to take place. What is the best way to get this information? A.Ask your neighbor B.Email Chad C.Check the calendar D.Use Slack channel Block Structure Block 0: Basic Week 2: Blood, Week 1: Basics of information that Fluids, Week 3: Genetics, Biochemistry, Intro your MCAT prep Homeostasis and Development and to the Profession should have introduction to Histology and EBM covered Pharmacology Week 4: Introduction to Week 5: Week 6: Week 7: Review Microbiology, Immunology and Introduction to and Block Exam Immunology and Microbiology II Nervous System Pharmacology ll  Biochemistry - Energy production Components of blood, movement of fluids and ions across membranes Genetics, transmission, consequences of abnormalities and the diagnostic assays used to identify them. Infectious agents and ways to administer pharmacological agents to fight them. Fundamental pharmacokinetic and pharmacodynamic principles and how Block content to apply them. Components of the immune system how they fight pathogens. Divisions of the nervous system, with a focus on the autonomic system and how therapeutics manipulate cellular communication. Interpret novel clinical research studies and learn how to apply results to patients. Responsibilities and ethics of being a physician, the role of the physician in the healthcare system of the United States, and ways to mitigate bias. Population health, equity, and inclusion; and your effect on your local community. Engaging with the Curriculum https://docs.google.com/spreadsheets/d/1oscisbdKh4ucIsljfY_HiMu 2XpKJR8fqN5OdWxoQxNs/edit?gid =0#gid=0  Attendance MANDATORY sessions You have 5 mins to sign into BenWare to log your attendance at an Attendance MANDATORY session You have one ‘failure to sign in’ for Block 1. You may request to use this if you are physically present in class before the attendance exam expires, but forget to sign in. The second instance of failing to sign in will be counted as an unexcused absence. You will fail the course based on Professional Engagement if you have >2 unexcused days Session Terminology Type Description Flipped Classroom Reverses the traditional learning environment by incorporating preparatory work that students are expected to complete in advance of the session Interactive Lecture Content presented in a mixture of typical lecture format and application content in the form of questions or some other interactivity Learning Module Curricular content that students are expected to complete on their own outside of class without an instructor present Team Based Learning prep work for students to complete so they can actively participate, TBL Individual readiness assurance test (IRAT timed and graded 10 questions Team readiness assurance test (TRAT) timed and graded. teams work on the same 10 questions. Attendance Required Core Case Longer interactive sessions (typically 2-3 hours) where students are taken through one or more clinical cases. Attendance Required Lab Hands-on interactive sessions for anatomy, histology, or pathology topics  Session Terminology on Blackboard Learning Goals Learning Objectives Estimated Prep Time The over-arching educational Specific knowledge targeted by Approximate estimate of time concept(s) of the session the session that a student should required to finish prep know or be able to do by the end Use this to plan out your weekly of the class session study schedule ScholarRx Your go to for preparatory You are expected to know this Learning Modules will be on material for sessions content prior to coming to class Scholar Rx  Poll: Word Cloud As you create the study plan, how will you use the following? A. Learning Objectives B. Estimated Prep time The course calendar is your guide to planning Blackboard materials for class sessions are posted several days in advance. Study Plan Go through the upcoming week Example and write your study plan. Schedule some time each week to review old content.  Block 1 Assessments Grading Component Date Proposed weights for AY 24-25 TBL Week 1 (Hunger Strike) Week of August 19, 2024 3.75% Week 1 Quiz August 23, 2024 3.75% Week 2 Checkpoint Assessment August 30, 2024 5.00% TBL Week 3 (Chromosomal Week of September 2, 2024 3.75% Abnormalities) Week 3 Quiz September 6, 2024 3.75% Week 4 Quiz September 13, 2024 7.50% Week 5 Checkpoint Assessment September 20, 2024 5.00% Week 6 Quiz September 27, 2024 7.50% Final Exam October 03, 2024 50.00% Professional Engagement Across Course 10.00% Total 100% Grading Breakdown Item MPL Grade How does it affect me? Contribution Professional 0.80 10% non-compensatory(must pass to pass the block) Engagement Each unexcused absence results in a 10% deduction Weekly Quizzes 0.67 MPL is used only as a guide for you to gauge your progress and proficiency with the material 30% TBLs Based on faculty review of compensatory the exam CPAs Based on faculty review of 10% compensatory the exam Block Final Based on faculty review of 50% non-compensatory (must pass to pass the block) the exam Course MPL Weighted average of above 100% Course grade - weighted average of other components components which must be reached to pass the course. A pass level is also needed in each of the noncompensatory components to pass the course  Poll Which of the following must you pass to pass the course? A. Professionalism B. TBL C. Check Point Assessment D. Weekly Quiz This Photo by Unknown Author is licensed under CC BY-NC Professional Engagement This Photo by Unknown Author is licensed under CC BY-SA  Block 1 Assessments Quiz Quiz Quiz Quiz Exam Exam week Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 (Exam Thurs) TBL TBL CPA CPA Week 2: 20 items Week 5: 20 items Week 1: 10 items Week 4: 5 items Week 3: 5 items Assessments Final Block Exam : Thursday, October 3, 2024 All content covered during the block Includes themes/subthemes and online learning modules ~100 questions 1.5 minutes per question  Assessments Check Point Assessment: Friday of Week 2 and Week 5 10% of the block grade 30 items - 20 from the week prior and 10 from weeks before that within the block Administered unproctored over the weekend Learning Lab Optional session: Offered twice during the block In the checkpoint week Faculty partner with learning specialists Go over concepts which are frequently not clear Specifically discuss approach to answering questions  Individual Readiness Assurance Test (IRAT) Based on pre-work materials Taken individually Worth 60% of the TBL grade Team Readiness Assurance Test (TRAT) TBL Sessions Taken after the IRAT Group work on the same questions from the IRAT Worth 40% of the TBL grade IRAT/TRAT: Part of weekly assessments MANDATORY Released on Friday at noon Weekly Quizzes 50% of grade -for completion ≈20 questions 50% of grade is received for quiz review 85% of quiz - must be answered 3 min per question for Quiz review review period Average of 30 seconds must be spent per question during quiz Access once Max 1.5 minutes per question Provide constructive Quiz commentary feedback on questions  Question Where can you find reliable questions and answers for practice during the block? Supplemental Questions Practice Items on BenWare USMLE Rx and Qmax on Scholar Rx Brainteasers  Brainteasers Brainteaser! A three-year-old with pyruvate kinase deficiency is admitted to the pediatric emergency department with new onset jaundice. His mother informs you that he received his first blood transfusion at the age of three months and has needed transfusions every month since then. His mother states he has been fatigued. The physical exam is notable for yellowing of the white of the eyes and skin and pale conjunctiva. Lab test shows low blood count with “burr cells” and high bilirubin. 1. What will explain the patient’s fatigue and jaundice? List 1 2. Why is the conjunctiva pale and the conjunctiva yellow? 3. How does pyruvate kinase deficiency cause this patient's condition?  Supplemental Resources Your primary resources are your professors and the provided class materials & textbooks First Aid – Summarizes important information, can be used as an organizational system Anki, Firecracker, Adaptive study resources with question banks and flashcards Pathoma – Study aid focused on pathology Sketchy Medical Memory mnemonic videos for various disciplines (microbiology, pharmacology, pathology) This Photo by Unknown Author is licensed under CC BY-SA Poll: Word Cloud How can you make your voice heard to improve the block? This Photo by Unknown Author is licensed under CC BY-SA  Program Evaluation Your feedback is very important to improve the curriculum – Student comments on ambiguous assessment items – Post quiz survey on Program Evaluation (class sessions) – End of block questionnaire – Focus group with students or town halls – Others… Changes Made Based on Student Feedback Changes to prep materials – use of ScholarRx Embryology session moved to week 6 Added more time for pharmacology sessions The introduction to histology lab will be in the active learning classrooms (Chicago) HIS: Population Health Structural Competency and Health Equity and Measurements of Health and Disease lecture has been made in person for this year (Chicago)  Tips For Success Engage! Best predictor of success Plan out your week Stay on top of content Take care of yourself Schedule some down time Ask for help Faculty and staff are always willing to help This Photo by Unknown Author is licensed under CC BY-NC Questions?  Glycolysis Block 1, Week 1 Presenter: Jalees Rehman, MD [email protected] Developed by Drs. Caffrey, Chastain, Regan, Rehman and Sengupta Includes material originally authored by David McPheeters Conflict of Interest Statement The presenters do not have a financial interest, arrangement, or affiliation with any organization that could be perceived as a real or apparent conflict of interest in the context of the subject of this presentation.  Glycolysis Learning Objectives 1. Apply the concept of Km and substrate affinity in relation to the function of facilitated glucose transporters (SGLT1, GLUT1 – GLUT5). 2. Compare and contrast the enzyme kinetics of hexokinase and glucokinase in the first step of glycolysis and their different tissue distributions. 3. Relate how the regulation of glycolysis (including hormonal, PFK2) and the 3 irreversible steps impacts the production and consumption of ATP. 4. Discuss tissue dependence on aerobic glycolysis. 5. Identify conditions under which glycolysis is switched to the anaerobic mode (lactic acid production) and justify this switch in specific cell/tissue types. 6. Explain the metabolic and physiological consequences of deficiencies that affect glycolysis (Pyruvate kinase deficiency, Phosphofructokinase deficiency, GLUT1 Deficiency). 7. Explain the basis of the Warburg effect in cancerous tissues and how this can be used to image cancers.. Glycolysis What to not to focus on What to focus on You will not be tested on The overall goal of the pathway (liver, muscle, – Intermediate Structures rbcs) – Catalytic Triads Committed Steps & Control points (transporters, hormonal, metabolite activators/inhibitors) What are the consequences if an enzyme (GLUT1, PFK1, PK) is deficient How would another metabolic pathway (defect) alter glycolysis? How do we detect cancer by understanding how glycolysis works? Develop an intuitive sense for what it means for cells to undergo excessive and prolonged glycolysis Outline of fuel Metabolism L 8:2 Your First Patient  LO 6 What could be the potential medical condition or diagnosis for a 3-year-old individual brought to the office by their parents with the following symptoms: anemia (low blood cell count), yellowish tint to the skin and mucous membranes, yellowish tint to the white part of the eyes, pale skin, persistent tiredness (lethargy), easy fatigue, and an enlarged spleen?“ Labs: Sugar: Normal Lactate (serum): Low end of normal Hemoglobin, Hemocrit: Low What enzyme does he have a deficiency in ? A. Erythrocyte pyruvate kinase B. PFK-1 deficiency C. Triosephosphate ? isomerase D. Pyruvate dehydrogenase complex E. Pyruvate carboxylase Write down your answer on a piece of paper or the whiteboard. We will revisit this question after gaining knowledge to be able to choose the solution with confidence.  Utilizing the glucose that comes from your diet. LO 1 A 22-year-old male medical student volunteers for a nutrition study. A baseline blood sample is obtained. The student is then given a large bowl of rice to consume over 30 minutes. After eating the rice, a second blood sample is drawn. Which of the following substances will increase most significantly in the second blood sample compared to baseline? A. Fatty acids B. Disaccharides C. Glucose D. Lactose E. Triglycerides F. Sucrose BB  LO 1 A 22-year-old male medical student volunteers for a nutrition study. A baseline blood sample is obtained. The student is then given a large bowl of rice to consume over 30 minutes. After eating the rice, a second blood sample is drawn. Which of the following substances will increase most significantly in the second blood sample compared to baseline? A. Fatty acids B. Disaccharides C. Glucose D. Lactose E. Triglycerides F. Sucrose BB LO 1 Rice - Rationale Answer C (correct answer): Rice contains large amounts of glucose polymers called starch. In the gut, starch is broken down and absorbed as the monosaccharide, glucose. Answer B (incorrect answer): Disaccharides include sucrose, lactose and maltose. These substances are not directly absorbed. They are broken down into glucose which is taken up by enterocytes. Answers A and E (incorrect answers): Only a very small portion of rice consists of fats such as fatty acids and triglycerides. Answers D and F (incorrect answers): The only sugars absorbed from the GI tract are the monosaccharides, glucose, fructose, and galactose. Other sugar structures like starch, lactose, glycogen, or sucrose are not absorbed into the bloodstream. These substances are metabolized to monosaccharides for absorption. What about 1 – 2 hours after a meal? BB  Sugar Indicators in the body LO 3 Your body uses insulin to let it know to A. take away from your energy reserves (glucose is gone) B. add to your energy reserves as your body has lots of excess energy (insulate your energy needs)  LO 3 Sensing Sugar Levels (FYI, Discussed in Block 2,7) How does glucose enter the blood stream and into the various cells?  LO 1 GLUT Transporters Glucose Tissue Function Km Value Substrate Affinity Comments Transporter Distribution Transport glucose with Small Efficient at low Low (High Allows glucose from the diet to enter SGLT1 sodium ions (co- intestine, renal glucose affinity) enterocytes. transport) tubules concentrations Efficient at low Essential for glucose supply to erythrocytes Widely Low (High GLUT1 Basal glucose uptake glucose and cell types with barrier functions (blood- expressed, affinity) concentrations brain). Liver, Efficient at A high-capacity, low-affinity transporter. Transport glucose in High (Lower GLUT2 pancreas, higher glucose Important for glucose storage and release liver, pancreas, intestine affinity) small intestine concentrations in liver and pancreas. Transport glucose in Efficient at low Very low (High Major transporter in the central nervous GLUT3 brain and glucose- Brain, neurons glucose affinity) system demanding tissues concentrations Responsive to Insulin-dependent (Insulin sensitive) Insulin-regulated glucose Moderate Muscle, changes in blood transporter. In the presence of insulin, the GLUT4 uptake in muscle and (Moderate adipose glucose and number of GLUT 4 transporters increases on adipose tissue affinity) insulin signaling the cell surface. Efficient at Transport fructose (a High (Lower Facilitates fructose uptake from the diet in GLUT5 Small intestine higher fructose sugar found in fruits) affinity) the small intestine. concentrations LO 1 While ubiquitous in many tissues, this GLUT transporter is very important in red blood cells and the blood-brain barrier. blood A. SGLT1 B. GLUT1 blood brain barrier blood brain barrier C. GLUT2 D. GLUT3 blood E. GLUT5  LO 1 While ubiquitous in many tissues, this GLUT transporter is very important in red blood cells and the blood-brain barrier. blood A. SGLT1 B. GLUT1 blood brain barrier blood brain barrier C. GLUT2 D. GLUT3 blood E. GLUT5 Glucose is in the cell. Now What? What can happen to glucose once it is inside a liver cell? A. Gets polymerized and stored as glycogen. B. Is utilized to make NADPH & pentose sugars. C. Is activated to oxidize to two molecules of pyruvic acid. D. Is transported right back out of the cell. What can happen to glucose once it is inside a liver cell? A. Gets polymerized and stored as glycogen. B. Is utilized to make NADPH & pentose sugars. C. Is activated to oxidize to two molecules of pyruvate. D. Is transported right back out of the cell. What helps the cell know when to do A and C. How about B?  Glucose in Cell Rationale A and C. Occur due to a high Insulin to Glucagon ratio B. NADPH is used as a reducing agent in lipid and nucleic acid synthesis anabolic reactions. It is always active. D. Does not occur due to the first step in the processing of glucose when it enters the cell Glycolysis  General Overview of Glycolysis Universal Pathway, only fuel used by every tissue Ten Steps – each catalyzed by an enzyme A catabolic pathway Intermediates – all phosphorylated – Traps sugar inside cell - Handle for enzymes - Need phosphorylated sugar to make ATP -Stages of glycolysis -Preparatory phase (energy investment) -Payoff phase (energy generation) Relate how the regulation of glycolysis (including hormonal, PFK2) and the 3 irreversible LO 3 steps impacts the production and consumption of ATP.(HK/GK, PFK-1, PK). * * Irreversible reactions of glycolysis are indicated by red boxes *committed step of glycolysis  LO 3 Step 1: 1st Priming Step: Phosphorylation of Glucose This process uses the energy of ATP ATP-bound Mg++ facilitates this process by shielding the negative charges on ATP Highly thermodynamically favorable/irreversible Two isozymes: Hexokinase (muscle cells, adipose, RBC, most cells) and glucokinase (liver, pancreatic beta-cells) Differ by Km, Vmax, inhibition LO 2 Phosphorylation of glucose to yield glucose-6-phosphate serves as the 1st committed step of glycolysis (also serves as the 1st step of glycogen synthesis in the liver). Reaction is catalyzed by either hexokinase or glucokinase, depending on the tissue. Hexokinase Glucokinase Location Most tissues, except for Liver, Beta cells of liver and pancreatic B cells pancreas Km Lower (↑ affinity) Higher (↓affinity) Vmax Lower (↓ capacity) Higher (↑ capacity) Induced by insulin No Yes (hormonal control) Feedback-inhibited by Yes No glucose-6-phosphate (allosteric control) Hexokinase versus glucokinase  LO 2 Hexokinase Glucokinase Its low Km allows glucose to enter cells, Glucokinase has kinetic properties (High Vmax, especially brain cells and RBCs, under all induced by insulin) that allow it to capture conditions. This is important when under much of the dietary glucose that enters the fasting conditions. liver from the intestines via the portal Excess removal of glucose from the blood into circulation. This high-capacity uptake provides tissues is prevented by the allosteric inhibition glucose for conversion to glycogen or fatty of hexokinase by its product, G6P, and its low acids. Purpose Vmax. The high Km also minimizes the uptake of glucose by the liver during fasting, thereby preventing unnecessary synthesis of glycogen and the development of hypoglycemia. Hexokinase versus In a nutshell: At low glucose concentrations, hexokinase sequesters glucose in the tissues. glucokinase At high glucose concentrations, glucokinase allows excess glucose to be stored in the liver. If a person has a fasting blood glucose level of 5 mmol/L (90 mg/dL), will it affect a red blood cell’s ability to phosphorylate glucose? A. Yes B. No Fed state If a person has a fasting blood glucose level of 5 mmol/L (90 mg/dL), will it affect a red blood cell’s ability to phosphorylate glucose? A. Yes B. No Fed state FYI: The minimum concentration of glucose in which red blood cells cannot obtain sufficient glucose is known as the critical glucose concentration. The critical glucose concentration varies among individuals, but it typically falls between 1-3 millimolar (mM) (18 – 54 mg/dL). LO 3 2nd Priming Phosphorylation Further activation of “glucose.” Phosphofructokinase-1(PFK) phosphorylates Fructose 6-phosphate at position 1 to make Fructose 1,6-bisphosphate. Committed step in glycolysis Uses the energy of ATP Highly thermodynamically favorable; irreversible step Phosphofructokinase-1 is highly regulated Inhibited by ATP Do not burn glucose if there is plenty of ATP Inhibited by Citrate Let TCA catch up Activated by AMP We need energy! Fructose by F2,6-bisphosphate Insulin/Glucagon level is high  Regulation by fructose 2,6-bisphosphate LO 3 During the Well-Fed State: Decreased levels of glucagon and elevated insulin levels (such as following a carbohydrate- rich meal) cause an increase in hepatic fructose 2,6-bisphosphate and, thus, in the rate of glycolysis. Fructose 2,6-bisphosphate acts as an intracellular signal of glucose abundance. During fasting: By contrast, the elevated levels of glucagon and low levels of insulin that occur during fasting cause a decrease in hepatic fructose 2,6-bisphosphate (PFK-2 is phosphorylated). This results in inhibition of glycolysis and activation of gluconeogenesis. Is synthesized by a bifunctional enzyme with 2,6-bisphosphate a kinase domain (PFK-2) and a phosphatase domain (FBPase 2). Insulin activates the kinase domain (PFK2) of the bifunctional enzyme PFK2 phosphorylates F 6-P to create F 2,6- BP (which activates PFK1) phosphofructokinase 2/fructose-2,6-bisphosphatase (PFK-2/FBPase-2). Insulin causes the kinase domain (Phosphofructokinase,PFK2) of the bifunctional enzyme to be activated which phosphorylates F 6-P to create F 2,6-BP (which activates PFK1) The bifunctional enzyme: Phosphorylated – PFK2 inactive, FBPase-2 inactive; Dephosphorylated – PFK2 active, FBPase-2 inactive. Insulin Insulin activates a phosphoprotein phosphatase which Dephosphorylates the bifunctional enzyme. The kinase activity of the bifunctional enzyme, PFK2, favors the production of Fructose 2,6-bisphosphate. Fructose 2,6-bisphosphate activates PFK1, which leads to an increase in glycolysis. Relate how the regulation of glycolysis (including hormonal, PFK2) and the 3 irreversible LO 3 steps impacts the production and consumption of ATP.(HK/GK, PFK-1, PK). * Irreversible reactions of glycolysis are indicated by red boxes *Committed step of glycolysis 1 glucose + 2ADP + 2NAD+ → 2 pyruvate + 2ATP +2NADH LO3 D. McPheeters Pyruvate Kinase Inhibited by ATP (we have all the energy needed!) Activated by F-1-6bisP (lots of sugar is coming down glycolysis!)  Summary of Glycolysis LO 3,5 Glucose + 2 NAD+ + 2 ADP + 2 Pi à 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP Used: – 1 glucose; 2 ATP; 2 NAD+ Made: – 2 pyruvate Various different fates – 4 ATP Used for energy-requiring processes within the cell – 2 NADH Must be reoxidized to NAD+ in order for glycolysis to continue Glycolysis is heavily regulated – Ensure proper use of nutrients – Ensure production of ATP only when needed LO4 Many tissues rely on glycolysis for a portion of their ATP requirements Tissues/cells dependent on glycolysis may feature: - Need for rapid ATP - High levels of glycolytic enzymes - Few capillaries (oxygen must diffuse over greater distance) - Lack of mitochondria or increased rate of glycolysis often related to cell function Tissue/Cell Notes Red blood cells Lack mitochondria Type II skeletal muscle Involved in high intensity short duration exercise ( Sprinting) where availability is O2 is limited due to low fibers myoglobin content and less mitochondria Eye Cells that transmit or focus light cannot be filled with mitochondria or dense capillaries  Control of Glycolysis 1. Hormonal 2. Metabolites Hormonal Control Metabolite Control Glycolysis Conditions ↑insulin ↓glucagon Promote Glycolysis, Shut down Gluconeogenesis Major Sites of regulation in the glycolytic pathway Allosteric and hormonal control influence same Remember that Glucokinase (liver, beta cells of the glycolytic enzymes Remember that Hexokinase (the enzyme that phosphorylates glucose in most other cells) is not pancreas) is hormonally controlled. activated by insulin but is feedback-inhibited by glucose-6-phosphate. A 32-year-old Type 1 diabetic patient checks their serum glucose levels and it is at 300 mg/dL. They administer insulin to themselves, and their glucose levels go down to 110 mg/dL. The decrease in serum glucose is mediated through which of the following? A. Decreased synthesis of phosphoenolpyruvate to pyruvate. B. Decreased levels of fructose 2,6-bisphosphate C. Increased activity of phosphofructokinase-1 D. Inhibition of tyrosine kinase receptors E. Activation of adenyl cyclase activity LO3 Type 1 Diabetic Patient - Rationale A. Decreased synthesis of phosphoenolpyruvate to pyruvate. – Insulin Increases synthesis B. Decreased levels of fructose 2,6-bisphosphate – Hepatic levels of fructose-2,6-bisphosphate are increased when insulin is high. F26BP favors glycolysis. Its levels fall in settings where gluconeogenesis occurs. C. Increased activity of phosphofructokinase-1 – Phosphofructokinase-1 is the rate-limiting enzyme of glycolysis. Its activity will increase after insulin administration as glycolysis is activated. D. Inhibition of tyrosine kinase receptors – Insulin activates the insulin receptor which is a tyrosine kinase E. Activation of adenyl cyclase activity – Glucagon activates adenyl cyclase activity not insulin.  LO 4,5 What is the best answer as to why red blood cells (and other cells that rely on glycolysis) produce lactate? A. Because lactate B. Generates an is a better acid additional 2.5 ATPs than pyruvic acid in Ox Phosph D. Without this C. Lactate can be step anerobic converted into glycolysis would glucose eventually stop Write down on a piece of paper what you think the correct answer is. LO 4,5 What is the best answer as to why red blood cells (and other cells that rely on glycolysis) produce lactate? A. Because lactate B. Generates an is a better acid additional 2.5 ATPs than pyruvic acid in Ox Phosph D. Without this C. Lactate can be converted into step anerobic glycolysis would Why? glucose eventually stop  LO 4,5 LO 4,5 Build up in muscle At rest ~1.2 mM/L lactate – exercise transient 17 mM/L lactate LO 4,5 What are the physiological benefits or advantages that the body gains from producing lactate, making it a desirable process despite its acidifying effect on the blood? B. In red blood A. It can be used to cells, it generates make fatty acids in an additional 2.5 the liver. ATPs in Ox Phosph. C. In the liver, D. Without this lactate can be step anerobic converted into glycolysis would glucose. eventually stop Write down on a piece of paper what you think the correct answer is.  LO 4,5 What are the physiological benefits or advantages that the body gains from producing lactate, making it a desirable process despite its acidifying effect on the blood? B. In red blood A. It can be used to cells, it generates make fatty acids in an additional 2.5 the liver. ATPs in Ox Phosph. C. In the liver, D. Without this lactate can be step anerobic converted into glycolysis would glucose. eventually stop The Cori Cycle LO 4,5  LO 4,5 Lactate Formation Reduction of pyruvate to lactate, reversible During strenuous exercise, lactate builds up in the muscle – Generally, takes less than 1 minute The acidification of muscle prevents its continuous strenuous work The lactate can be transported to the liver and converted to glucose there (Cori cycle) Requires a recovery time – Recovery from strenuous exercise involves several processes, including the clearance of lactate, replenishment of muscle glycogen stores, and restoration of cellular homeostasis. LO4,5 Why do errors in glycolysis become most pronounced in RBC and Muscles?  LO4,5 Red Blood Cells Anaerobic glycolysis due to them not having mitochondria. Due to [glucose] always being above the Km for GLUT1 (its glucose transporter) and Hexokinase being Feedback- inhibited by glucose-6-phosphate, RBCs are always at their maximum rate of getting glucose inside and phosphorylating it. Therefore, when there is a defect in their glycolysis, they cannot increase the flux of glucose coming into them. This means that processes such as those that help maintain membrane integrity are inhibited, causing red blood cells to lyse prematurely (causing jaundice and anemia). LO4,5 Type II Fast Twitch Muscle Cells Skeletal muscles contain both Fast Twitch (rapid movements) and Slow Twitch (endurance) muscle fibers. Ratios of Fast Twitch to Slow Twitch can differ depending on various factors, including muscle function, age, and training. Fast Twitch Muscle Cells rely on glycolysis to produce ATP When in use, fast twitch muscle fibers can only be used for a limited time (to keep them from excessively depleting ATP and incurring damage because of lack of energy). Glycolysis defects in fast twitch muscle cells cause the fibers to run out of energy prematurely, causing over-exertion and muscle damage (rhabdomyolysis).  LO 6 Diseases Associated with Glycolysis Pyruvate PFK1 GLUT 1 Kinase Deficiency Deficiency Deficiency PFK-1 Deficiency – Muscles (and RBCs) LO 6 Key features and symptoms : Exercise intolerance: Individuals with PFK1 deficiency often experience muscle cramps, weakness, and fatigue during physical activity due to the impaired ability to generate ATP from glycolysis. Myopathy: Muscle weakness and wasting are common features of the condition, and the muscles may be particularly affected after exercise. Rhabdomyolysis occurs (which causes urine to turn Coca-Cola colored). Hemolytic anemia: PFK1 deficiency can lead to the breakdown of red blood cells (hemolysis), which results in anemia. Enlarged liver (hepatomegaly): Some individuals with PFK1 deficiency may have an enlarged liver due to glycogen accumulation. Elevated creatine kinase (CK) levels: CK is an enzyme released from damaged muscle tissue, and its levels are often elevated in individuals with PFK1 deficiency.  Pyruvate Kinase Deficiency LO 6 (Red Blood Cells) Pyruvate kinase deficiency (PKD) is a rare genetic disorder that affects the red blood cells' ability to produce enough energy to maintain their normal shape and function. It is the most common cause of chronic non-spherocytic hemolytic anemia, which is a type of anemia characterized by the destruction of red blood cells at a faster rate than they can be produced. Here's how pyruvate kinase deficiency affects red blood cells: Key features and symptoms of GLUT1 deficiency include: 1. Anemia (low blood cell count): Pyruvate kinase deficiency leads to the destruction of red blood cells (hemolysis), resulting in anemia, as the red blood cells have a reduced lifespan. 2. Yellow color of the skin, mucous membranes, and white part of the eyes (jaundice): The increased destruction of red blood cells releases a compound called bilirubin, which is responsible for the yellow discoloration of the skin and eyes. 3. Pale skin: Anemia causes a decrease in the number of red blood cells, which are responsible for carrying oxygen. Reduced oxygen-carrying capacity leads to paleness of the skin. 4. Lethargy and easy fatigue: Anemia results in reduced oxygen delivery to the body's tissues, leading to fatigue and lethargy. 5. Enlarged spleen (splenomegaly): The spleen plays a role in filtering and removing damaged or abnormal red blood cells from circulation. In PKD, the increased destruction of red blood cells can lead to an enlarged spleen as it works harder to clear the damaged cells. GLUT1 Deficiency (Brain, RBCs) LO 6 Key features and symptoms of GLUT1 deficiency include: Seizures: Seizures are one of the most prominent and characteristic symptoms of GLUT1 deficiency. Headaches and neurological symptoms: Some individuals with GLUT1 deficiency may experience frequent headaches, migraines, and other neurological symptoms. Microcephaly: In some cases, the head circumference may be smaller than normal due to impaired brain growth. Anemia: The exact mechanisms underlying the development of hemolytic anemia are not fully understood, but it is thought to be related to metabolic dysfunction and energy deficiency in red blood cells.  LO 6 Glycolysis Enzyme Deficiencies Muscle Red Blood Cell Elevated Enzyme Anemia Notes Symptoms Characteristics Intermediates No specific Spiculated Red PEP, 2-PG, and Pyruvate kinase Anemia muscle symptoms Blood Cells 3PG Rhabdomyolysis, Sometimes F-6-P and PFK-1 deficiency Normal shape muscle damage anemia above This deficiency results in impaired glucose transport No specific Sometimes GLUT 1 Normal shape - across the blood-brain barrier, muscle symptoms anemia reducing glucose supply to the brain. Explain the basis of the Warburg effect in cancerous tissues and how this can be used to locate cancer  Otto Heinrich Warburg (1883-1970) § Warburg was a student of Nobel Prize laureate Emil Fischer § Warburg received Nobel prize in 1931 for discovering cytochrome c oxidase § Warburg hypothesis “aerobic glycolysis” in cancer cells § Warburg developed numerous methods to study metabolism, nominated for a second Nobel Prize but did not win it Image from Koppenol et al., Nature Reviews Cancer 2011 § Warburg’s student Hans Krebs won a Nobel Prize § Controversy about his personality (arrogance) and lack of political resistance LO 7 Warburg Effect In contrast to normal differentiated cells, which rely primarily on mitochondrial oxidative phosphorylation to generate the energy needed for cellular processes, most cancer cells instead rely on aerobic glycolysis, a phenomenon termed “the Warburg effect.” Most cancer cells produce large amounts of lactate regardless of the availability of oxygen and hence their metabolism is often referred to as “aerobic glycolysis.”  Glycolysis and Cancer: The Warburg Effect In the first half of the 20th century, Otto Warburg observed that most cancer cells predominantly produce energy using glycolysis followed by lactic acid fermentation rather than by a comparatively low rate of glycolysis followed by oxidative phosphorylation as in most normal cells. Effect is sometimes attributed to cancer growth outpacing formation of blood vessels AND/OR increased needs for biosynthetic precursors. In cancerous tissues, the increase in glycolysis is achieved at least in part by increased synthesis of hexokinase (and other glycolytic enzymes thru HIF-1) and of the plasma membrane transporters PKD and GLUT3. The Warburg Effect is exploited to look for potentially cancerous, high glucose 61metabolizing tissues by the intravenous administration of [18F]2-Fluorodeoxyglucose ([ F]FdG). 18 LO 7 A PET scan for cancer requires the action of which glycolytic enzyme? 1. Hexokinase 2. Phosphofructokinase 3. Pyruvate kinase 4. Triosephosphate isomerase 5. Lactate dehydrogenase  LO 7 A PET scan for cancer requires the action of which glycolytic enzyme? 1. Hexokinase 2. Phosphofructokinase 3. Pyruvate kinase 4. Triosephosphate isomerase 5. Lactate dehydrogenase LO 7 F18is a positron emitter- positron collides With electrons producing gamma rays Which are captured by detectors t1/2 110 minutes Can’t undergo next step in glycolysis, i.e. Can’t be isomerized to fructose  LO7 The Warburg Effect underlies the basis for PET scans. False color, CT scan Fused image Phosphorylation traps [F18]FDG-6-Phosphate in the cell PET scan 18F has a half-life of 110 minutes and emits a positron upon decay Example here shows a patient with primary malignant melanoma (surgically removed) and metastasis has occurred. Dark spots in the PET scan indicate regions of high glucose utilization. The brain and bladder are most heavily labeled. Brain because, unlike other tissues that may consume fats, the brain can only use glucose for energy under normal circumstances. 18F-labeled 6-phospho-FdG accumulates in the bladder because it is excreted in the urine. When the intensity of the label in the PET scan is translated into false color (intensity increases from green ➝ yellow ➝ red) and the image is superimposed on the CT scan, the fused image (right) reveals cancer in the bones of the upper spine, in the liver, and in some regions of the muscle. 65 D. McPheeters CLINICAL VIGNETTES Glycolysis Defects  LO 6 What could be the potential medical condition or diagnosis for a 3-year-old individual brought to the office by their parents with the following symptoms: anemia (low blood cell count), yellowish tint to the skin and mucous membranes, yellowish tint to the white part of the eyes, pale skin, persistent tiredness (lethargy), easy fatigue, and an enlarged spleen?“ Labs: Sugar: Normal Lactate (serum): Low end of normal Hemoglobin, Hemocrit: Low LO 6 What enzyme does he have a deficiency in? For those of us who are A. Pyruvate kinase struggling to answer this. Would this help? B. PFK-1 deficiency Metabolic Intermediates: markedly elevated C. Glucose-6-phosphate concentrations of 1,3 bisphosphoglycerate, 3- dehydrogenase phosphoglycerate, 2- phosphoglycerate, and D. Pyruvate dehydrogenase phosphoenolpyruvate complex E. Pyruvate carboxylase  LO 6 What enzyme does he have a deficiency in? A. Pyruvate kinase B. PFK-1 deficiency C. Glucose-6-phosphate dehydrogenase D. Pyruvate dehydrogenase complex E. Pyruvate carboxylase LO 6 What enzyme does he have a deficiency in? Muscle Red Blood Cell Elevated Anemia Notes Enzyme Symptoms Characteristics Intermediates No specific Spiculated Red PEP, 2-PG, and Normal Glucose Pyruvate kinase muscle Anemia Blood Cells 3PG Levels symptoms Rhabdomyolysis, Sometimes Normal Glucose PFK-1 deficiency - F-6-P and above muscle damage anemia Levels Glucose-6- No specific Red blood cells Activated by - phosphate muscle Anemia have Heinz external agents dehydrogenase symptoms Bodies (food, drugs) Pyruvate Elevated Lactic acidosis, Normal Glucose dehydrogenase No Anemia - Pyruvate, muscle weakness Levels complex Lactate, alanine Elevated Hypoglycemia No specific Pyruvate Pyruvate, that only resolves muscle No Anemia - carboxylase Lactate, alanine, when carbs are symptoms Ammonia consumed  PK - Rational for Patient’s Presentation Based on the symptoms described, it is highly suggestive of a possible diagnosis of pyruvate kinase deficiency (PKD). Let's break down the symptoms and how they relate to the condition: 1. Anemia (low blood cell count): Pyruvate kinase deficiency leads to the destruction of red blood cells (hemolysis), resulting in anemia, as the red blood cells have a reduced lifespan. 2. Yellow color of the skin, mucous membranes, and white part of the eyes (jaundice): The increased destruction of red blood cells releases a compound called bilirubin, which is responsible for the yellow discoloration of the skin and eyes. 3. Pale skin: Anemia causes a decrease in the number of red blood cells, which are responsible for carrying oxygen. Reduced oxygen-carrying capacity leads to paleness of the skin. 4. Lethargy and easy fatigue: Anemia results in reduced oxygen delivery to the body's tissues, leading to fatigue and lethargy. 5. Enlarged spleen (splenomegaly): The spleen plays a role in filtering and removing damaged or abnormal red blood cells from circulation. In PKD, the increased destruction of red blood cells can lead to an enlarged spleen as it works harder to clear the damaged cells. Pyruvate Kinase Deficiency ? A. Increase Lactate Production in Red Blood Cells B. Has No Effect on Lactate Production in Red Blood Cells C. Decreases Lactate Production in Red Blood Cells  LO 6 A 65-years-old female because of intolerance to exercise and chronic fatigue. From youth she suffered from spasms of random occurrence associated with muscle weakness, painful intolerance to small efforts, and intermittent dark urines, especially after exercise due to myoglobinuria, as revealed by urinalysis. Physical examination showed no weakness or muscle atrophy and only a moderate splenomegaly without hepatomegaly or lymphadenopathy. Labs: Sugar: Normal Lactate (serum): Not determined Glycolytic Intermediates levels: Not determine Hemoglobin, Hemocrit: Slightly below normal. Uric acid elevated LO 6 What enzyme does she have a deficiency in ? A. Pyruvate kinase B. PFK-1 deficiency C. Glucose-6-phosphate dehydrogenase D. Pyruvate dehydrogenase complex E. Pyruvate carboxylase  LO 6 What enzyme does he have a deficiency in? Muscle Red Blood Cell Elevated Anemia Notes Enzyme Symptoms Characteristics Intermediates No specific Spiculated Red PEP, 2-PG, and Normal Glucose Pyruvate kinase muscle Anemia Blood Cells 3PG Levels symptoms Rhabdomyolysis, Sometimes Normal Glucose PFK-1 deficiency - F-6-P and above muscle damage anemia Levels Glucose-6- No specific Red blood cells Activated by - phosphate muscle Anemia have Heinz external agents dehydrogenase symptoms Bodies (food, drugs) Pyruvate Elevated Lactic acidosis, Normal Glucose dehydrogenase No Anemia - Pyruvate, muscle weakness Levels complex Lactate, alanine Elevated Hypoglycemia No specific Pyruvate Pyruvate, that only resolves muscle No Anemia - carboxylase Lactate, alanine, when carbs are symptoms Ammonia consumed Glycolysis Overview and Regulation Summary Overall Goal of Glycolysis Consequences of Enzyme Deficiencies: – Liver: Aerobic - Pyruvate for TCA cycle and ATP – GLUT1 Deficiency: GLUT1 Deficiency Syndrome production. - Neurological issues. Anemia. – Muscle (Type 2): Anaerobic - Lactate production – PFK1 Deficiency: Glycogen Storage Disease Type for ATP during exercise. Cori Cycle. VII - Muscle injury. – RBCs: Anaerobic - Lactate production for energy – PK Deficiency: Hemolytic Anemia - Fragile RBCs. due to lack of mitochondria. Cori Cycle. Impact of Metabolic Pathway Defects: Control Points: – Mitochondrial Dysfunction: Increases glycolysis – Hexokinase/Glucokinase: (aerobic glycolysis). Glucose entry into glycolysis. – Hormonal Imbalances: Alters glycolytic control Glucokinase: Activated by insulin, inhibited by glucagon. (e.g., diabetes). Hexokinase: Allosterically regulated by G-6-P – Pyruvate Metabolism Disorders (Pyruvate – PFK-1: Carboxylase, Pyruvate Dehydrogenase Main regulatory step of glycolysis. Complex): Affects pyruvate fate, causing lactic Allosterically regulated by ATP,F-2-6-bisP, citrate, and acidosis. hormonal signals. – Pyruvate Kinase (PK): Cancer and Glycolysis: Final ATP production step. – Cancer cells exhibit the "Warburg effect." Allosterically regulated by ATP levels, F-1,6bisP, and – Detect cancer with PET scans using radioactive hormonally. glucose analogs (FDG).  Additional Practice Questions Carbohydrate Catabolism - Glycolysis 1. A newborn presents with severe acidosis, vomiting, hypotonia, and neurologic deficits. Laboratory analysis reveals elevated levels of lactate and alanine. These observations suggest a deficiency of which of the following enzymes? (A) Alanine aminotransferase (B) Glutamate dehydrogenase (C) Lactate dehydrogenase (D) Phenylethanolamine N-methyltransferase (E) Pyruvate dehydrogenase 2. Following the ingestion of glyburide (an antidiabetic drug in a class of medications known as sulfonylureas), a type 2 diabetic patient begins to experience anxiety, diaphoresis, and hunger. The patient subsequently ingests a health food bar containing glucose. The glycolytic degradation of the ingested glucose commences with the action of which of the following enzymes? (A) Aldolase (B) Hexokinase (C) Phosphofructokinase (D) Phosphoglucose isomerase (E) Pyruvate kinase QUESTIONS FROM: USMLE® Step 1 Qbook, Sixth Edition, KAPLAN PUBLISHING, New York  Carbohydrate Catabolism – Glycolysis (cont’d) 3. An infant receives an exchange blood transfusion due to severe neonatal jaundice. Red blood cell transfusion is required monthly, and at 6 months of age, a splenectomy is performed. Histologic examination of the spleen reveals marked hemosiderosis. Laboratory studies show: Patient Normal RBC 2.54 X 106/mm3 3.5-5.5 x 106/mm3 Hemoglobin 8.3 g/dL 12-16 g/dL Hematocrit 23.4% 34-46% Reticulocytes 27% 0.5-1.5% Indirect bilirubin 6.1 mg/dL 0.4-3.4 mg/dL (conjugated) Analysis of red cell glycolytic intermediates indicates markedly elevated concentrations of 2,3 bisphosphoglycerate, 3- phosphoglycerate, 2-phosphoglycerate, and phosphoenolpyruvate. Which of the following is the most likely diagnosis? (A) Glucose-6-phosphate dehydrogenase (G6PD) deficiency (B) Lead poisoning (C) Pyruvate kinase (PK) deficiency (D) Sickle cell anemia (E) !-Thalassemia QUESTIONS FROM: USMLE® Step 1 Qbook, Sixth Edition, KAPLAN PUBLISHING, New York Carbohydrate Catabolism – Glycolysis (cont’d) 4. A 25-year-old woman with type 1 diabetes mellitus has maintained good glycemic control for several years. Recently she has gained 10 pounds and joined a group exercise program. By the end of her first 1-hour aerobics session, she is dizzy, nauseated, and feels faint. Which underlying mechanism is the most likely explanation for this episode? (A) Inadequate delivery o