Liver Pathology - MAFLD - PDF

Liver Pathology Part III MAFLD – e-learning P1 BMS 200 Week 1 Non-Alcoholic Fatty Liver Disease (NAFLD) – Recall from BMS 150 Steatosis in the absence of significant alcohol consumption ▪ Most common cause of liver disease in US ▪ Estimated prevalence of up to 4...

Liver Pathology Part III MAFLD – e-learning P1 BMS 200 Week 1 Non-Alcoholic Fatty Liver Disease (NAFLD) – Recall from BMS 150 Steatosis in the absence of significant alcohol consumption ▪ Most common cause of liver disease in US ▪ Estimated prevalence of up to 40% of the population Forms include: ▪ Simple hepatic steatosis and steatosis complicated by inflammation These show fewer long-term complications unless they progress to NASH ▪ Progression to NASH is uncommon, and it is unclear why some progress ▪ Non-alcoholic steatohepatitis (NASH) Progresses to cirrhosis in 10 – 20% of cases In those that progress to cirrhosis, the incidence of liver cancer can be as high as 1-2% per year Non-Alcoholic Fatty Liver Disease (NAFLD) – Recall from BMS 150 Pathologic findings: ▪ Initially hepatocyte ballooning, lobular inflammation, and steatosis (fat accumulation in hepatocytes) ▪ With progressive disease there is steadily more fibrosis, eventually leading to cirrhosis ▪ Strongly associated with obesity and the metabolic syndrome Pathophysiology: ▪ “two-hit” model, involving 1) hepatic fat accumulation and 2) increased oxidative stress Free radicals cause lipid peroxidation of the accumulated intracellular fat ▪ Obesity seems to be associated with reduced intestinal barrier function 🡪 increased inflammation in the liver Movement of microbes from the gut into the portal circulation  General cirrhosis pathogenesis – Recall from BMS 150 Cirrhosis definition: Diffuse remodeling of the liver into parenchymal nodules surrounded by fibrous bands and variable degree of vascular shunting Pathogenesis (most likely theory): Stellate cells become activated & differentiate into highly fibrogenic myofibroblasts ▪ Activated by inflammatory cytokines (eg. TNF-alpha), toxins, reactive oxygen species ▪ Signals implicated include PDGF, TGF-beta, IL-17 ▪ Deposit ECM into the space of Disse 🡪 fibrous septae formation in regions of hepatocyte loss ▪ Hepatocytes regenerate in nodules, but the architecture of the acinus is disrupted due to fibrosis Kumar et. al., Robbins and Cotran Pathologic Basis of Disease 9th ed.  Non-Alcoholic Fatty Liver Disease (NAFLD) – Recall from BMS 150 > 80% < 20% ~ 11% of NASH (2%?) NAFLD – a dynamic spectrum of liver pathology: A. Healthy liver. B. Simple steatosis (arrow shows fatty hepatocyte) C. Nonalcoholic steatohepatitis (NASH); ballooned hepatocyte (arrow) near central vein with adjacent blue-stained pericellular fibrosis (arrowheads). D. Cirrhosis with blue-stained bridging fibrosis surrounding micronodules of liver parenchyma Non-Alcoholic Fatty Liver Disease (NAFLD) – Recall from BMS 150 Clinical features: ▪ Usually asymptomatic until hepatic failure (due to cirrhosis) clinical findings usually due to accompanying atherosclerotic disease/diabetes Cardiovascular disease a frequent cause of death ▪ Fatigue and right-sided abdominal pain can occur in some ▪ Increased risk of hepatocellular carcinoma Diagnosis: ▪ Liver enzymes alone are poorly reliable ▪ Scores calculated from age, BMI, fasting glucose, AST, ALT are helpful for gauging degree of inflammation and fibrosis ▪ Detection of fibrosis via imaging or biopsy for definitive diagnosis Kumar et. al., Robbins and Cotran Pathologic Basis of Disease 9th ed. MAFLD vs NAFLD MAFLD = “metabolic dysfunction associated fatty liver disease” How does MAFLD differ from NAFLD in terms of diagnostic criteria? Both require a 5% “level” of hepatic steatosis ▪ How is this diagnosed? For discussion later NAFLD diagnosis requires exclusion of other causes of liver disease (i.e. significant alcohol use, hemochromatosis, etc.) ▪ negative criterion MAFLD diagnosis requires the presence of metabolic drivers of hepatic steatosis and inflammation, which can be any one of the following positive criteria: ▪ T2DM ▪ Obesity (this can be a tricky thing to define) ▪ A “metabolic dysfunction” composite score (see next slide) Gofton et. Al., “MAFLD: How is it different from NAFLD?”, Clin Mol Hepatol, 2023; 29 (Supp) S17 – S31 MAFLD and NAFLD Diagnostic Criteria * Metabolic risk abnormalities for MAFLD – 2 out of 7 (these are FYI) Elevated waist circumference Blood pressure > 130/85 (or BP meds) Elevated plasma triglycerides (> 1.7 mmol/L) Decreased HDL cholesterol MAFL Prediabetes (to cover in future D diabetes lecture) Elevated HOMA insulin resistance score (to cover in future diabetes lecture) Elevation in CRP Looks a lot like the metabolic syndrome criteria NAFL D Adapted from Gofton et. Al., “MAFLD: How is it different from NAFLD?”, Clin Mol Hepatol, 2023; 29 (Supp) S17 – S31 Why do the diagnostic differences between NAFLD and MAFLD matter? Clearer diagnoses: Patients could have non-alcoholic steatohepatitis AND have a chronic viral hepatitis… with the viral hepatitis complicating NASH ▪ What do you call that? Someone with MAFLD who also has hep B or hep C just has MAFLD complicated with a viral hepatitis ▪ No negative criteria 🡪 diagnostic clarity Better identification of patients who need more aggressive/targeted management Studies seem to indicate that a MAFLD diagnosis is more closely linked to the development of worsened liver fibrosis Gofton et. Al., “MAFLD: How is it different from NAFLD?”, Clin Mol Hepatol, 2023; 29 (Supp) S17 – S31 Why do the diagnostic differences between NAFLD and MAFLD matter? Identification of those with higher “wear and tear” due to “metabolic dysregulation” A MAFLD diagnosis increases the risk of the following conditions over a NAFLD diagnosis (although sometimes only slightly) ▪ Subsequent development of diabetes (in those who are not already diabetics) ▪ Chronic kidney disease ▪ Worsened lung function (and worsened complications after COVID infection) Gofton et. Al., “MAFLD: How is it different from NAFLD?”, Clin Mol Hepatol, 2023; 29 (Supp) S17 – S31 Why do the diagnostic differences between NAFLD and MAFLD matter? Under-reporting of alcohol ingestion It is estimated in some cohorts that up to 30% of those diagnosed with NAFLD actually do consume alcohol regularly and in clinically significant quantities (as assessed with fancy biochemistry tests) ▪ There can be serious stigma in some cultures about frequent alcohol consumption (and a regular stigma in most cultures) ▪ This leads to patient under-reporting Not an issue with MAFLD diagnostic criteria A small caveat: A small proportion of those with a fatty liver do not fulfill ANY of the other criteria for MAFLD… and therefore would have NAFLD, but not MAFLD ▪ Approximately 5% of those with fatty livers Gofton et. Al., “MAFLD: How is it different from NAFLD?”, Clin Mol Hepatol, 2023; 29 (Supp) S17 – S31 Is a MAFLD diagnosis “redundant”? There is little argument that MAFLD results in worsened mortality compared to NAFLD… but is that just because those with MAFLD also have metabolic syndrome, obesity, or diabetes on top of steatosis? ▪ Why not just say someone has NAFLD as well as metabolic syndrome or obesity or diabetes? This is a good question, but perhaps not a very clinically-relevant one ▪ Simply put, MAFLD is a more straightforward diagnosis that helps guide the clinician to more comprehensive treatment sooner ▪ Studies will likely address this question in the future Gofton et. Al., “MAFLD: How is it different from NAFLD?”, Clin Mol Hepatol, 2023; MAFLD – some extra pathophysiology Why do obesity, insulin resistance, and fatty liver tend to cluster together? Insulin resistance 🡪 increased FFA liberation from adipocytes 🡪 conversion into triglycerides and storage in hepatocytes Elevated glucose and insulin levels 🡪 hepatic triglyceride synthesis Greenberger’s Current Diagnosis & Treatment in Gastroenterology, Hepatology, & th  MAFLD – some extra pathophysiology Why do obesity, insulin resistance, and fatty liver tend to cluster together? As intra-abdominal fat increases, adiponectin levels tend to decrease ▪ Adiponectin is an adipokine released by visceral fat ▪ It increases glucose utilization and fatty acid oxidation ▪ Studies show adiponectin levels tend to be lower in patients with fatty liver and steatohepatitis Greenberger’s Current Diagnosis & Treatment in Gastroenterology, Hepatology, & th  MAFLD – counteracting pathophysiology What works in MAFLD? ▪ Weight loss through lifestyle modification – the best therapeutic option so far! Those that are obese or have type II diabetes can reduce steatosis with weight reduction Exercise and weight loss can improve fibrosis and steatosis ▪ No approved meds yet, though some do improve inflammation and steatosis in patients Thiazolidenedione medications (i.e. pioglitazone) improve insulin sensitivity and seem to increase adiponectin secretion Incretin agonists improve insulin secretion and help with weight loss in diabetes ▪ Vitamin E seems to reduce oxidative stress in hepatocytes, and is linked to reduced steatosis and inflammation in patients with steatohepatitis Greenberger’s Current Diagnosis & Treatment in Gastroenterology, Hepatology, & th An Approach to Hepatic Investigations Blood Labs: Liver Enzymes, Liver Function Tests, and others Application of Selected Tests to Liver Pathology E-learning P2 BMS 200 Laboratory Analysis of the Liver Learning outcome: Compare and contrast how the different transaminases (ALT, AST), ALP, bilirubin, albumin, and PT/iNR can be used to assess etiology and extent of liver damage Liver enzyme tests: ▪ ALT & AST ▪ GGT, ALP, & 5’ nucleotidase Liver function tests: ▪ Albumin & PT/iNR ▪ Bilirubin Direct (conjugated) and indirect (unconjugated) Selected disease-specific tests General Patterns and Concepts Damage to hepatocytes or to the biliary tree causes enzymes that are normally found within the cell or attached to cell membranes to “leak” into the bloodstream ▪ When serum levels of these enzymes increase (liver enzyme tests), it indicates damage, but says nothing about liver function The function of the liver can be crudely evaluated by considering three major parameters in the blood: ▪ Serum albumin (maintains oncotic pressure, helps transport hydrophobic substances) – decreases as hepatic function is impaired ▪ Bilirubin (breakdown product of heme, excreted into the biliary tree) – increases as hepatocytes are damaged or sometimes when hepatic function is impaired ▪ “Time to clot”, known as the PT/INR (the liver produces coagulation proteins) – increases as hepatic function is impaired Elevated PT/INR = longer time to form a clot = less coagulation proteins General Patterns and Concepts In situations where hepatocytes suffer damage but the biliary tree does not experience obstruction or damage: ▪ ↑↑ AST and ALT ▪ normal or mildly elevated ALP or GGT ▪ Known as a hepatocellular pattern In situations where the primary problem is obstruction/inflammation of the biliary tree (intrahepatic or extrahepatic bile ducts or the wall of the gallbladder): ▪ ↑↑ ALP and GGT ▪ Normal or ↑ AST and ALT ▪ Known as a cholestatic pattern Liver Enzyme tests - ALT ALT = alanine aminotransferase Found mostly in the cytosol of hepatocytes ▪ few other cells express significant amounts, main other source is the kidney (but far more in hepatocytes) ▪ Therefore elevations in ALT are relatively specific for hepatocyte damage Small amounts of ALT are released into the bloodstream in healthy individuals, but significant elevations usually indicate hepatocyte damage ▪ FYI – normal level varies from lab to lab, but usually ranges from 10 to no more than 40 IU (a little higher for men) ▪ Half life of a few days Liver Enzyme tests - AST AST = aspartate aminotransferase Found in the cytosol and mitochondria of hepatocytes ▪ Many other cells containg AST – elevations in the serum could be due to hepatic, skeletal myocyte, cardiomyocyte, renal, or pancreatic injury ▪ Therefore elevations in AST are less specific for hepatocyte damage As with ALT, low levels of AST are present in the blood of healthy individuals, but significant elevations usually indicate hepatocyte damage FYI factoids: ▪ Normal level similar to ALT, 10 to no more than 40 IU, half life is a few days ▪ Less AST than ALT in the cytosol 🡪 if hepatocyte membrane is disrupted, usually more ALT is released than AST Liver Enzyme tests - ALP ALP = alkaline phosphatase Found at/around the canalicular membrane of hepatocytes ▪ ALP is also expressed by bone (during growth or fracture or other changes to bone) and by the placenta Therefore, levels are increased during pregnancy or childhood/adolescence ▪ During damage to the biliary apparatus ALP is released to the bloodstream Includes cholestasis in the intra- and extrahepatic biliary tree, and sometimes during cholecystitis (25%) Assorted ALP FYI info ▪ Normal level ranges between 35 – 100 IU (varies widely in normal population) Liver Enzyme tests – GGT & 5’ nucleotidase GGT = gamma-glutamyl transpeptidase GGT is found in the cell membranes of a wide variety of cells (hepatocytes & cholangiocytes, kidney, pancreas, spleen, heart… many) ▪ Although sensitive, it is not specific – many people have an isolated elevated GGT and no significant pathology ▪ Alcohol-use disorder can result in disproportionate increases in GGT vs ALP… one has to be aware of the non-specific nature of GGT, though, before stigmatizing the patient 5-NT is also found in a wide variety of cells, but increases usually mean hepatobiliary disease (more specific than GGT) Both of these labs are meant to “double-check” whether an elevation of ALP means hepatobiliary disease 🡪 this is the ▪ GGT normal levels: 9 – 85 U/L preferred “double check” test for ALP elevations ▪ 5’ NT normal levels: 0 – 18 U/L (varies with age) Liver Function tests - bilirubin Where does bilirubin come from? (preview for hematology) : Hemoglobin is degraded to the “heme” portion and the “globin” portion ▪ “globin” portion is just a protein – it gets metabolized by macrophages ▪ “heme” portion is a porphyrin ring structure… tougher to break down Macrophage degrades heme to biliverdin 🡪 unconjugated bilirubin (hydrophobic) ▪ Unconjugated bilirubin is carried (via albumin) to the hepatocyte… The hepatocyte conjugates bilirubin to a soluble form (bilirubin glucuronide) Rubin’s Pathology: Mechanisms of Human Disease 8th ed., fig. 20-5 Liver Function tests - bilirubin Two forms of bilirubin measured: ▪ Unconjugated bilirubin (indirect) – bilirubin in the serum that has not yet been complexed to glucuronide Due to large hematomas, disorders where large numbers of RBCs are damaged Due to disorders that affect bilirubin conjugation Some increase can be seen with hepatocyte damage ▪ Conjugated bilirubin (direct) – the hepatocyte has conjugated bilirubin, but it has “leaked back” into the bloodstream because of: Blockage within the biliary system Inability to transport conjugated bilirubin into canaliculi (rare) Damage to hepatocytes Liver Function tests - bilirubin Assorted bilirubin facts: Texts/papers differ on whether this is a “function” test or an “enzyme” test ▪ Most of the time, an elevation in serum bilirubin is due to hepatocyte damage or impaired bile flow… so it’s similar to AST/ALT/GGT/ALP in that way ▪ However, sometimes elevated serum bilirubin is a deficit in liver function (i.e. Gilbert’s syndrome) ▪ Most texts group bilirubin with the “function” tests or group it independently from “function” or “enzyme” tests Hepatocytes are able to rapidly conjugate bilirubin – the rate-limiting step is transport of bilirubin into the canaliculi ▪ This means when a hepatocyte is damaged, conjugated bilirubin increases in the serum more than unconjugated bilirubin ▪ Elevations in only unconjugated bilirubin is almost always an RBC problem or an enzyme deficit in conjugation Liver Function tests - albumin Albumin is a protein synthesized by the liver – major functions include: ▪ Carrier for hydrophobic molecules (like bilirubin) ▪ Establishes oncotic pressure in the capillary Decreases in serum albumin are usually caused by: ▪ Long-term deficiency in production – chronic liver diseases or serious protein malnutrition (can’t build protein if you don’t eat it) ▪ Loss of albumin from a variety of organs (usually the kidney, but there are others) ▪ Accumulation of more extracellular fluid than usual – “dilutes” albumin in the blood Albumin has a pretty long half life (almost 3 weeks), so liver dysfunction has to be present for a while before it drops Liver function tests – PT/INR Why such a weird name? ▪ PT refers to the prothrombin time – the time it takes to clot using a specific “branch” of the coagulation cascade (you’ll learn about this in hematology) ▪ INR = international normalized ratio… it’s a mathematical correction that standardizes the result between labs (often this test is just known as the INR) Increased PT/INR means that it takes longer to form a clot due to a deficiency of coagulation factors in the blood ▪ Ratio value – the normal PT/INR is 1 ▪ 1.5 roughly means it takes 50% longer for blood to clot than the lab’s reference “normal” The liver is the source of almost all serum coagulation factors, and many depend on the presence of vitamin K ▪ Therefore liver dysfunction or vitamin K deficiency can increase clotting times Liver function tests – PT/INR PT/INR FYI factoids INR increases fairly quickly after the liver’s synthetic capabilities are compromised ▪ Half life of most coagulation factors range from hours to a few days ▪ Therefore a better way to assess liver function acutely than albumin Bringing it all together – liver labs *Most types of acute hepatocellular injury: ▪ Both ALT and AST are very elevated, but ALT more than AST ▪ ALP and GGT may be normal, but often modestly increased (elevated less than 3X normal) ▪ Not enough time for albumin to change, but both direct and indirect bilirubin are often increased If PT/INR increased, indicates severe damage *Most types of chronic hepatocellular injury: ▪ ALT and AST modestly increased, usually ALT > AST ▪ ALP and GGT normal or modestly increased ▪ Albumin often decreased, PT/INR and both unconjugated/conjugated bilirubin increased Decreased liver function is often a result of late-stage disease – early disease often exhibits normal bilirubin, PT/INR, and albumin Bringing it all together – liver labs *Cholestasis: ▪ AST and ALT are normal to moderately elevated ▪ ALP and GGT are very elevated ▪ Usually large increase in serum bilirubin, especially conjugated, but PT/INR and albumin are normal Other liver test patterns (FYI): ▪ Cirrhosis – looks like chronic hepatocellular injury, except the AST:ALT ratio is often 2 or greater ▪ Alcoholic liver disease – can resemble acute or chronic hepatocellular injury (depending on stage and situation, except AST:ALT ratio is often 2 or greater and often GGT is very elevated ▪ Hepatocellular carcinoma, liver metastases – most tests are normal, but ALP is very elevated ▪ Gilbert’s syndrome – all liver tests are normal except for an elevated unconjugated bilirubin (conjugated normal) Bringing it all together – liver labs Assorted tests beyond general liver labs that are useful in diagnosing hepatobiliary disease covered in BMS thus far Disorder Liver Lab Pattern *Other labs Hepatitis A Acute hepatocellular Anti-HepA IgM Hepatitis B Acute or chronic HBeAg, HBV DNA, HBsAg hepatocellular 🡪 cirrhosis Anti-HBe, anti-HBs, anti-HBc Hepatitis C Chronic hepatocellular 🡪 HCV RNA cirrhosis Autoimmune Usually chronic Anti-smooth muscle antibodies, hepatitis hepatocellular, sometimes ANA flares with acute Rarely anti-cytochrome antibodies hepatocellular, LFTs often N Primary biliary ALP, GGT most elevated 🡪 Anti-mitochondrial antibodies cirrhosis/cholangitis cirrhosis pattern Primary sclerosing ALP, GGT and AST most p-ANCA (associated with cholagnitis elevated early (looks like ulcerative colitis) cirrhosis due to cholestasis) Other labs FYI Liver imaging – FYI review Simple ultrasound is the best way to examine the larger biliary ducts, gallbladder initially MRI/CT can assess masses and MRI can give some information about fibrosis ▪ MRI can also provide more detailed views of the biliary system (known as MRCP) Liver biopsy is necessary to evaluate and stage fibrosis or cirrhosis, and is the definitive test for liver disease that is difficult to diagnose non-invasively Liver investigations in MAFLD - FYI Most common liver disease – but expensive to diagnose definitively How is steatosis > 5% diagnosed? Tough question ▪ Elastography assesses fibrosis well, but can have false positives can be done via ultrasound (cheaper, accurate) and MRI (not as much data, emerging) ▪ MRI is best at diagnosing steatosis precisely ▪ Rarely biopsy – biopsy definitively diagnosis steatosis and fibrosis Since we can’t screen everyone using ultrasound elastography (Fibroscan) or MRI, patients are referred for imaging when: ▪ Fulfill the metabolic criteria of MAFLD ▪ Elevation in liver enzymes – elevations in ALT most common, early chronic hepatocellular pattern ▪ They are scored using (usually simple) blood tests and other clinical data – the scoring systems are used to predict presence of fibrosis MAFLD screening tests (FYI) FIB-4 score – use the following to calculate: ▪ Patient age, AST, ALT, platelet count NAFLD fibrosis score ▪ Patient age, BMI, presence of insulin resistance/diabetes ▪ AST, ALT, platelet count There are others ▪ Some, such as the ELF, assess molecular markers that are not part of the “typical” blood tests that most labs run frequently (but Lifelabs carries it) Etiology of Eating Disorders Anorexia nervosa and bulimia are complex eating disorders with multiple factors contributing to their etiology Psychological factors: OCD traits, cognitive rigidity, emotion sensitivity and impulsivity as well as history of developmental stressors/ trauma and challenging interpersonal relationships Body dissatisfaction is important as well as some behavioural factors like engaging in diets, and particular athletics Accurso 2019 Etiology of Eating Disorders Anorexia nervosa and bulimia are complex eating disorders with multiple factors contributing to their etiology Biological factors: 50% due to multiple genetic effects Dysfunction in serotonin, dopamine, norepinephrine, opioid and cholecystokinin systems Hypothalamic regulation (amenorrhea can precede weight loss!) Some research suggests changes within peripheral satiety network Vicious cycle as malnourishment can exacerbate the comorbid psychiatric conditions and further the behaviours Accurso 2019 Etiology of Eating Disorders Anorexia nervosa and bulimia are complex eating disorders with multiple factors contributing to their etiology Sociocultural factors: Idealization of thinness Triggers: Dieting is often a precipitating factor for triggering ED Illness leading to weight loss – especially true for AN Accurso 2019 Complications of Eating Disorders All-cause mortality 2-10x higher then general population Independent of weight: Vitamin and mineral deficiencies Stunted growth (if across lifespan) Reduced gastric motility (more discomfort and more food avoidance) Consequences of malnutrition: Bradycardia, hypotension, orthostasis, hypothermia, Metabolic alkalosis, hypochloremia, increased bicarbonate Osteopenia Myopathies Consequences of purging: Esophageal tears, intractable vomiting, hematemesis Metabolic acidosis (abuse of laxatives), hypokalemia cardiomyopathies (d/t specific vomit inducers) Accurso 2019