Human Nutrition PDF

Learning Domains: 1. Biochemical and chemical nature of nutrients 2. Processing of nutrients from the diet 3. Importance of gene function in the processing of nutrients 4. Regulation and dysregulation of nutrient metabolism 5. Inherited and acquired metabolic syndromes 6. Mechanisms by which nutrien...

Learning Domains: 1. Biochemical and chemical nature of nutrients 2. Processing of nutrients from the diet 3. Importance of gene function in the processing of nutrients 4. Regulation and dysregulation of nutrient metabolism 5. Inherited and acquired metabolic syndromes 6. Mechanisms by which nutrients regulate gene expression and function 7. Strategies used to study problems in human nutrition and metabolism 8. Integration of metabolism from the cellular to whole body level 9. Nutrition research processes and experiences to inform nutrition knowledge and practice Competencies 1. Food and Nutrition Expertise Dietitians integrate their food and nutrition expertise to support the health of individuals, communities, and populations 1.01 Apply understanding of food composition and food science f g 1.03 Apply understanding of human nutrition and metabolism a b c 1.04 Demonstrate understanding of the role of nutrients and other food components Demonstrate understanding of the processes of ingestion, digestion, absorption, and excretion Demonstrate understanding of metabolism Apply understanding of dietary requirements and guidelines a b 1.06 Identify sources of micronutrients and macronutrients in food Identify sources of non-nutrient functional components in food Demonstrate understanding of dietary requirements across the lifespan, in health and disease Demonstrate understanding of factors affecting energy balance in determining dietary requirements Integrate nutrition care principles and practices a b Demonstrate knowledge of human physiological systems in health and disease Demonstrate knowledge of the etiology and pathophysiology of nutrition-related diseases Module 3: Protein Nutrition and Metabolism Module 3 Protein Nutrition and Metabolism (Prof. L. Wykes) Concept of a Turnover of Protein Dietary Requirement of Amino Acids: Transformational Methodology Dietary Requirement of Protein: New Foundations of Policy mTOR, Nutrient Sensing and Cellular Regulation of Protein Synthesis and Proteolysis Inborn Errors of Metabolism and Special Functions of Amino Acids Metabolic Adaptations to Protein Energy Undernutrition Metabolic Adaptations to Metabolic Stress: Cancer Cachexia, Critical Illness and Surgery Iron Metabolism, Inherited and Acquired Anemias. Integration of Metabolism of the Erythrocyte Foundational Science Every metabolites in the body originated from a nutrient (diet extremely important) Gene expression control Nutrition Biochemistry molecular biology of metabolites Physiology how the systems in the body work Nobel Prizes in “Nutrition” Foundational Science: Human condition and the universe we live in Improve https://www.nobelprize.org/prizes/themes/the-nobelprize-and-the-discovery-of-vitamins/ Vital amines …vitamins A lot of them is for discovery of vitamins Vital amines —> amino groups Isolated chemically and define their structure —> association with function and role of deficiency in diseases Vitamins have chemical name and a letter name —> A, 12 B (bc we thought that the B complex was just 1 macronutrient and then we realized vitamin B1, B2, etc., no B4 bc the compound isolated at B4 was subsequently ID like not a vitamin bc not an essential nutrient) Cholesterol: not essential bc we can make it Thiamine deficiency prevalent in population that didn’t have a diverse diet —> deficiency diseases Cobalamin: the only one with cobalt in it Don’t need to know the names, just need to know that really relevant to the science of nutrition Nobel Prize in Physiology or Medicine Discovery of vitamins Christiaan Eijkman (1929) Vitamin B1 Sir Frederick Gowland Hopkins (1929) Growth Stimulating Vitamins George Hoyt Whipple (1934)* Vitamin B12 George Richards Minot (1934)* Vitamin B12 William Parry Murphy (1934)* Vitamin B12 Henrik Carl Peter Dam (1943) Vitamin K thiamine cobalamin Isolation of vitamins Nobel Laureates and their work with vitamins. Adolf Otto Reinhold Windaus (1928)* Vitamin D Albert von Szent-Györgyi Nagyrapolt (1937) Vitamin C Richard Kuhn (1938) Vitamin B2 and B6 Edward Adelbert Doisy (1943) Vitamin K Nobel Prize in Chemistry Synthesis of vitamins 1929: discovery of insulin by 2 ppl from University of Toronto —> protein hormone transcribed and translated into the polypeptide chain —> posttranslational processing —> insulin Walter Norman Haworth (1937) Vitamin C Paul Karrer (1937) Vitamin E Robert Burns Woodward (1965)* Vitamin B12 Structure of vitamins only women, ID structure of insulin and B12 Paul Karrer (1937) Vitamin A and B Richard Kuhn (1938) Vitamin B2 Lord (Alexander R.) Todd (1957)* Vitamin B12 Dorothy Crowfoot Hodgkin (1964)* Vitamin B12 Nobels • • • • • • • • • • Heat Production in Musclecalorimetry: energy expenditure Insulin (several) Krebs Cycle Cori Cycle Proteolysis (4) Cholesterol/fatty acid regulation Familial hypercholesterolemia Lac operon lactase deficiency —> not in lactase producing gene Crystallography / protein structure Electron transport Nobels - recent insulin stored in vesicles in beta cells so it can be release quickly when glucose concentration rises GLUT4 in muscles and other cells Cholesterol: LDLR imported in liver cells in vesicles Vesicles allow a rapid response after a change —> way to achieve homeostasis • Vesicles in metabolic regulation • Nuclear Magnetic Resonance • Helicobacter pylori can survive in low pH condition of the stomach • Autophagy • CRISPR-cas9 gene editing Nobels – next… • Theme…foundational science that enables the future • 2023 mRNA • https://www.nature.com/articles/d41586023-03046-x • The gender gap in Science awards • Rita Colwell Adversarial Collaboration • Adversarial collaboration is a framework intended to resolve scientific debates by calling on scholars with opposing views to make good faith efforts to articulate each other's positions; work together to design methods that both sides agree constitute a fair test and that they agree have the potential to change their minds; and publish the results, regardless of "who wins, loses or draws." SGLT1: in enterocytes SGLT2: in renal tubule (reabsorption of glucose) —> works until 10 mmol —> if more, glucose spills in urine bc SGLT2 overwhelmed Hyperglycemia —> trying to develop a drug that inhibits SGLT2 so more glucose is spilled in urine to lower blood glucose (no reabsorption of glucose) —> flozin —> helps reduce weight too, but frequent infection —> now prescribed for kidney functions Now ozampic Metabolic Homeostasis • Metabolic condition that is the result of dynamic processes to maintain a constant internal environment despite a changing external environment • Achieved by … • Examples… • 2 dogs go to the arboretum… • Use this as an example of learning Why do we measure concentrations of metabolites in plasma? concentration not a good measure bc we need to think abt dynamic processes it assumes that plasma is representative of the rest of the body (in diabetes, not representative bc disease of glucose excess in plasma, but in cell types that don’t require GLUT4 are deficient in glucose while some of them have hyperglycemia) What do they mean anyway? The “plasma pool” Homogeneity of pools? No, it’s not homogenous • Plasma… • Interstitial fluid? • Cerebrospinal fluid? • Intracellular fluid in different organs? Diabetes: continuous glucose monitors of interstitial fluid concentration much or less plasma concentration —> dynamic measure Immediate feedback of glucose monitors: helps make a person make decision in diet intake Flux of Metabolites: Glucose • Where does glucose come from, where does it go? If 5 mM/L of glucose in plasma: is that maintained by a really fast input and removal or slowly ? can’t know if just 1 reading of concentration Metabolic: flux (flow of metabolites in the system) Dietary sugar intake = changing external environment (~4 g) Measure metabolic rate —> should be done in clinical medicine too to see how to appropriately feed the patients in critical conditions Indirect calorimetry way to measure energy expenditure be able to measure which substrates are predominately used in the body flow of air through the hood and out to calorimeter that measures the CO2 from the air of the hood —> O2 lower bc he is consuming it, CO2 higher bc he’S producing it —> measures the change in relation to room air + flow air —> can measure the nbr of calorie he burns per minute —> burning more glucose or fat Glucose Homeostasis: How big is the plasma glucose pool? 5 mM/L x volume = mmol of glucose g/glucose 1 pool of a free metabolite and want to measure the flow: exogenous glucose from the diet, endogenous glucose from glycogen, gluconeogenesis through the Cori cycle or from aa glucose goes through glycolysis, TCA cycle, FA oxidation (lipogenesis), can go to glycogen, aa synthesis, glycosylation of protein —> many influx and outputs Interstitiel fluid: pretty close to plasma use it clinically to monitors glucose in the fluid between cells Normal fasting glucose: 5 mmol/l —> 180 grams/mol How much plasma do we have circulating: 8% of bodyweight = blood volume —> 5L of blood (3 and a half liters of plasma) Sugar cube of glucose Flux of Metabolites: Amino Acids • Where to AA’s come from, where do they go? Where do we get aa from ? muscles, protein breakdown, glucose Where do aa go ? protein, break them down, serotonin, melatonin, carnitine, creatine, Hb, histamine, etc. Aa coming out of stores can’t go back in bc there’s no aa stores (key difference from glucose and other macronutrients) If protein is broken down, it’s bc we need it for energy If we break down too much protein —> fragility, etc. We don’t want too much aa bc some aa are toxic (imbalance can be toxic in the brain) If we have a huge protein meal, eating more protein will not stimulate muscle protein synthesis High diet intake = high catabolism Catabolism is the way to regulate aa concentration Distribution of nutrient requirement in a population EAR: average requirement (some ppl need more than others) RDA: EAR + 2 SD change in response of a specific condition: adequate —> inadequate = requirement Individual variability: half of the ppl will have requirement higher than EAR and half of the subjects below the mean RDA: needs of almost all of them mean of all the subjects + 2 SD = propose RDA, so all the ppl below the RDA will have their needs satisfied if they consume it (99% of population) Should aim for RDA to lower risk of deficiency Studies propose mean requirement from data and propose a safe level Protein requirement EAR = 0.66 g/kg/d x 70 kg = 46 g/d RDA= 0.8 g/kg/d x 70 kg = 56 g/d Usual intake = 80-100 g/d Moving towards: RDA should be around 1.2 g/kg —> 84 g of 70 kg (fits in typical intake of american, but big deal for other countries) For ppl in critical illness 2.5 g/kg a day If question in exam: RDA is 0.8 g/kg Important Principles of Protein Metabolism Sarcoplenia: muscle wasting happens in aging —> fragility, problem with balance, etc. Not enough prot synthesis for prot breakdown • AAs are not “saved” as proteins i.e. there is no storage form of proteins • All proteins are synthesized to perform a function • The size of each free amino acid pool is regulated to achieve metabolic homeostasis • Excess amino acids are not synthesized into proteins, they are not stored, they are catabolized Imbalance in aa leads to toxicity Eating more protein does not drive protein synthesis —> metabolically control Different then the other macronutrients: excess glucose stored in glycogen and if still excess, FA and excess fat is stored as adipose The concept of nitrogen balance is that the difference between nitrogen intake and loss reflects gain or loss of total body protein. If more nitrogen (protein) is given to the patient than lost, the patient is considered to be anabolic or “in positive nitrogen balance”. Nitrogen Balance Intake 100 g if +: period of growth, pregnancy, etc. —> increase in protein pool if -: fasting, diseases, etc. —> protein pool decreasing of protein Special Products De novo synthesis Nitrogen in - nitrogen out Black Box 16 grams of nitrogen for 100 grams of protein bc 16% If homeostasis = 0 16 1 300 g 15 small number= 0.5 Synthesis Nitrogen Balance = N Intake – fecal N – urinary N (– misc losses) Body Protein skin, finger nails and hair, sweat, etc. Free AA Pool 95% absorb and 5% excreted Breakdown endogenous nitrogen too 15 grams catabolized and excreted 5g Feces 1 grams 95 g Urinary Nitrogen catabolize aa 300 g In adult in homeostasis: equilibrium (do not gain weight/lose weight, make or lose muscles) CO2, H2O Nitrogen Balance Measure the misc loss Protein Turnover Intake 100 g For essential aa: flux/flow (Q)=rate of intake+aa coming from protein breakdown = outflow = rate of protein synthesis + rate of oxidation/catabolism —> no de novo synthesis and special products really low Special Products De novo synthesis 300 g Synthesis Free AA Pool Breakdown 300 g 5g Feces 95 g Urinary Nitrogen No recycling program is 100% : need protein from the diet to keep the turnover going —> dietary requirement CO2, H2O Body Protein Nitrogen Balance More prot does not increase synthesis if it’s over the requirement Supplement: 200 grams a day instead of 100 g 200 g what drives protein synthesis: exercise (gain lean body mass), pregnancy, recovering from a disease, or metabolism condition in the body, BUT NOT THE DIET —> nitrogen balance + it’s always 300 grams remove more from the pool increase in catabolism 10 g 190 g If you are losing weight: need to maintain protein intake at the RDA level or else breakdown from your muscles AA degradation AA Degradation Energy production CO2 H2O Urea Conversion to other products Other amino acids phenylaline —> tyrosine —> multistage degradation Other N compounds neurotransmitter AA degradation • Glucogenic AAs • Their C skeleton can be converted to glucose • ALA, ARG, ASP, ASN, CYS, GLU, GLN, GLY, HIS, MET, PRO, SER, VAL • Ketogenic AAs • Their C skeleton can be converted to acetyl CoA or acetoacetate • LEU, LYS can’t produce glucose • ILE, THR, PHE, TRP, TYR: glucogenic & ketogenic intermediate fasting: not a good approach for maintain lean body mass bc you don’t eat protein and turnover is 24/7 breakfast: getting 30 grams of protein to have maximum insulin response post-exercise: remodelling of muscles, recovery window to eat protein Classification of AAs essential: if removed from the diet, function is comprised and when it is added again, will fix it Indispensable Conditionally Indispensable Dispensable some stages of life/ metabolic circonstance Phenylalanine aromatic aa Methionine sulfuric aa Leucine Isoleucine Valine Lysine Threonine Tryptophan Histidine want to determine the minimal aa intake to maintain function Tyrosine Cysteine Arginine Glutamine Glycine Proline key function in urea cycle Alanine Aspartate Asparagine Glutamate Serine DRI Report 2006 AA requirements (EAR mg/kg/d) FAO/WHO 1985 14 12 10 14 10 7 3 13 -- is abt twice DRI Report FNB/IOM 2005 Phenylalanine+Tyrosine Lysine Valine Leucine Isoleucine Threonine Tryptophan Methionine + Cysteine Histidine 27 31 19 34 15 16 4 15 11 Key difference: flux turnover + oxidation rate of aa Optimal AA profile 120 Minimizes AA catabolism % of requirement 100 Maximizes protein synthesis 80 60 40 20 0 At Reqt Limiting AA profile 120 % of requirement 100 Some aa are not stable and not soluble (tyrosine) Human diet: want a lot of diversity of aa Agriculture: diet with supplement in lysine Couple of conditions that compromised transport of aa: lysine, phenylkotenuria: can’t produce phenylalanine and tyrosine 80 60 40 20 0 lysine At Reqt Limiting Limiting AA Intake Special Products De novo synthesis Synthesis Free AA Pool Breakdown - nitrogen balance Feces Urinary Nitrogen CO2, H2O Body Protein Metabolic response to intake of an essential AA: Nitrogen balance Limiting Reqt Excess lysine intake in excess = nitrogen balance, so will not change won’t put it in + nitrogen balance 0 nitrogen balance negative nitrogen balance Nitrogen balance really low when no lysine in the diet Adapted from Ann. Rev. Nutr. (2003) 23:101 Measuring N Balance Diet with a known protein intake: crystallize and pure aa (tastes disgusting and really expensive) precise knowledge of losses: need to collect everything —> if something is lost, all the study doesn’t work • Intake – losses (fecal and urine) • Adaptation period • E.g.: Urea pool: turns over really slowly Need to do it over several days to reach homeostasis • Total N intake = 15 g • Fecal losses = 1 g • Urinary excretion = 14 g • But what about miscellaneous losses? • 0.5 mg Studying Nitrogen Balance • 1950’s, 1960’s • Crystalline amino acids – pure, synthetic, expensive • Cutting edge for the time • Subjects consume purified diets for days at each AA intake level Studying Nitrogen Balance Clinical/Metabolic • COMPLETE intake and collections • Adaptation of urea pool several days Analytical the sample and measuring the ammonia produced • Routine analysis of total Nitrogen digesting —> not expensive, routine Modelling • Misc losses would increase reqt • Sensitivity: small number calculated from 2 large and similar numbers • Curvilinear response as balance approaches zero aa • Between-subject variance is high therefore repeated different requirement measurements on each subject needed…but adaptation issue New approach: measure flow from Hoffer 2000 Simplified version of real life Tracer Dilution Principles Steady state: constant level of water —> nibbling, not fasting/eating rollercoaster Constant level of water in the bathtub: drain is opened bc water is going in Masless tracer: the infusion of the tracer is not upsetting the steady state or magnitude Behaves like a tracee (Doesn’t stick to the side of the bathtub) Assumptions: 1. System at steady state in plasma and 2. Homogeneity of pool Mixes cells 3. Massless tracer, = tracee 4. No tracer recycling Tracer infusion rate depends that there is no recycling pump and it does not come back in the water water in the pool will get darker with the : equilibrium If the water is a light colour: diluted by a large flow of water If the water is dark: flow is slow —> inverse relationship Flow/Flux/Q=tracer infusion rate/tracer concentration in pool that we measure Flow = tracer infusion rate tracer conc in pool Rate of appearance (Ra) = Rate of disappearance (Rd) Ra=I+B (appearance from protein breakdown) Rd=S (synthesis)+O (oxidation/catabolism) Summing up… • • • • AAs are not “saved” as proteins. There is no storage form of proteins All proteins are synthesized to perform a function The size of each free amino acid pool is regulated to achieve metabolic homeostasis • Excess amino acids are catabolized • Metabolic flux of AAs can be determined by following “tracers”. Cash Flow Income $$$$ Expenditures Cash Flow “Marked Bill$” Tracer Income $$$$ Expenditures AA Flux Diet Intake Proteolysis AA Pool Protein Syn AA Oxidation AA Flux heavier than regular C13 1-13C-leucine Tracer usually infused IV Diet Intake Proteolysis AA Pool Protein Syn AA Oxidation Stable Isotope Tracers (non-radioactive) Element Carbon Hydrogen Nitrogen Oxygen Sulfur Radioactive —> decomposition when too much neutrons vs protons Isotopes can be used to trace their regular atom (13C and 14C can be used to trace 12C) Isotopes has a mass of 13 6 protons protons and 8 12C C 14C 6neutrons 12 and have 6 (makes it C) and C protons and 6 7 neutrons —> neutrons 1H 2H stable 3H 14N 15N 16O 180 32S 34S 35S regular ones Isotopomers regular mass + 1 13 [1- C] leucine; m+1 [5,5,5-2H3] leucine; m+3 Gas Chromatograph Mass Spectrometer (GCMS) measures mass of the amino acids Gas Chromatograph Mass Spectrometer (GCMS) bombarded by high energy electron: explodes the molecule into a very distinct powder of fragments —> ions that can travel in the electrical field through a series of lenses and then comes to the quadrupole mass analyzer : voltages slowly changed in the rod so that the ions spiraled down and hit the electron multiplier molecule being separated: no air molecules not very common in the field of nutrition bc really expensive Mass Spectrum = fingerprint of different ions how we ID pesticides, etc. Fingerprints used in metabolomics bc really specific If 120 is the water of the regular leucine, 121 would be the labeled leucine —> need to look at the ratio (how much the labeled leucine is diluted in the whole leucine pool) If 121 is low compared to 120: labeled leucine has been diluted so the flow is fast ions with a mass of 120 and charge 1 Tracer Dilution Principles Assumptions: 1. System at steady state 2. Homogeneity of pool 3. Massless tracer, = tracee 4. No tracer recycling Flow = tracer infusion rate tracer conc in pool Rate of appearance (Ra) = Rate of disappearance (Rd)