NONALCOHOLIC FATTY LIVER DISEASE

Transcription

1 NONALCOHOLIC FATTY LIVER DISEASE Kiran Bambha, MD, MSc Hepatology and Liver Transplantation University of Colorado Denver April 13, 2012 Non-Alcoholic Fatty Liver Disease (NAFLD) Terminology Pathogenesis Epidemiology Prevalence Natural History Age/Race-Ethnicity Approach to the patient with suspected NAFLD Diagnosis/ Disease Severity Treatment NAFLD Alcohol-like liver disease in individuals who do not consume excessive alcohol Women 1 drink/day (on average) Men 2 drinks/day (on average) Fatty liver associated with metabolic derangements Obesity Insulin resistance Diabetes mellitus Dyslipidemia Hypertension Metabolic Syndrome

2 Non-Alcoholic Fatty Liver Disease NAFLD Pathogenesis

3 NAFLD Pathogenesis: Old, but still entrenched, Concept There is a linear progression in disease severity Simple Steatosis NASH Cirrhosis NAFLD Pathogenesis: Old, but still entrenched, Concept There is a linear progression in disease severity Simple Steatosis NASH Cirrhosis NAFLD Pathogenesis: Old, but still entrenched, Concept Day and James, Gastroenterology 1998

4 NAFLD Pathogenesis: Old, but still entrenched, Concept Day and James, Gastroenterology 1998 Lipotoxicity Model of Pathogenesis the cause of steatosis, and not the fat accumulation by itself, produces cirrhosis. - Heribert Thaler, 1975 Clin Gastro 1975;4: Hepatology 2010;52: Lipotoxicity Model of Pathogenesis the cause of steatosis, and not the fat accumulation by itself, produces cirrhosis. - Heribert Thaler, 1975 Triglyceride accumulation in the form of lipid droplets in the liver is likely an innocent bystander Clin Gastro 1975;4: Hepatology 2010;52:774-88

5 Lipotoxicity Model of Pathogenesis Our understanding of what causes NASH at the molecular level is still nascent Lipotoxicity Model of Pathogenesis Evidence now points to free fatty acids and their metabolites as the more substantial culprits in NASH pathogenesis Free fatty acids and their metabolites are highly toxic to cells Inflammation, Apoptosis, Necrosis, ER Stress Triglyceride accumulation as lipid droplets in the liver is a parallel phenomenon May serve as a non-toxic, safer form of storage for lipids in the liver Lipotoxicity Model of NAFLD Supply Disposal Neuschwander-Tetri, Hepatology 2010

6 Lipotoxicity Model of NAFLD Supply RED ARROWS indicate processes that contribute to the flux of FFA to the hepatocytes. Disposal Promote lipotoxic injury. Lipotoxicity Model of NAFLD Supply RED ARROWS indicate processes that contribute to the flux of FFA to the hepatocytes. Disposal Promote lipotoxic injury. Lipotoxicity Model of NAFLD Supply Disposal GREEN ARROWS indicate processes that eliminate FFA. Reduce lipotoxic injury.

7 Lipotoxicity Model of NAFLD Supply Disposal GREEN ARROWS indicate processes that eliminate FFA. Reduce lipotoxic injury. Lipotoxicity Model of NAFLD Supply Disposal No direct pathway from Steatosis to NASH Neuschwander-Tetri, Hepatology 2010 Lipotoxicity Model of NAFLD Free Fatty Acids and their metabolites are highly toxic to tissues Accumulation of TG is not needed for the development of NASH TG accumulation may, in fact, be protective Supply Steatosis does not progress to NASH Disposal Neuschwander-Tetri, Hepatology 2010

8 Magnitude of the Problem: NAFLD Prevalence Study cohort (~1100 African Americans, 700 Caucasians, 400 Hispanics) No risk factors (n = 375) H 1 -NMR spectroscopy Assess risk factors for NAFLD Define normal liver fat content 5.5% Assess prevalence of increased liver fat (steatosis) in entire population & ethnic subgroups Hepatology 2004;40:1387 NAFLD Prevalence: Dallas Heart Study Liver fat < 5.5% Liver fat > 5.5% Steatosis = 34% Hepatology 2004;40:1387 NAFLD Prevalence: Dallas Heart Study Liver enzymes NORMAL in most (79%) with steatosis Liver fat < 5.5% Liver fat > 5.5% Steatosis = 34% Hepatology 2004;40:1387

9 NAFLD AND NASH PREVALENCE IN US COHORT HIGHER THAN PREVIOUSLY ESTIMATED Williams CD, Stengel J, Asike MI, et al. Prevalence of NAFLD and NASH in a Largely Middle-aged Population Utilizing Ultrasound and Liver Biopsy: A Prospective Study Gastroenterology. 2011;140: Summary of Study Design Primary Care outpatients (18-70 yo) at Brooke Army Medical Center, January March 2010 Excluded patients with known liver disease and alcohol use Right upper quadrant ultrasound reviewed for presence of steatosis based on echogenic features Laboratory analyses and percutaneous liver biopsy for patients identified as having fatty liver by ultrasound Williams CD, et al. Gastroenterology. 2011;140: Steatosis and NASH are Prevalent 46% of patients had NAFLD according to evidence from ultrasound and liver biopsy (if performed) Highest prevalence of NAFLD observed in Hispanics (58%), followed by Caucasians (44%) and lowest prevalence in African Americans (35%) 12% of all patients had NASH on liver biopsy All individuals with NASH were obese and hypertensive 74% of diabetics had NAFLD and 22% had NASH Several studies have documented a high prevalence of NAFLD with DM: 40-70% DM have 80% more hepatic fat compared with age-, weight- and sex-matched controls Williams CD, et al. Gastroenterology. 2011;140:

10 NASH is associated with the Number of Metabolic Derangements Dixon et al, Gastroenterology, 2001; 121: NAFLD High-Risk: Bariatric Surgery Patients Liver disease often unsuspected pre-operatively Intraoperative liver biopsy typically shows NAFLD (84-96%) Steatosis: 30-90% Steatohepatitis: 33-42% Fibrosis: Mild-to-Moderate Fibrosis: 33% Advanced Fibrosis: 12% Cirrhosis: 1-2% NAFLD High-Risk: Bariatric Surgery Patients Liver disease often unsuspected pre-operatively Intraoperative liver biopsy typically shows NAFLD (84-96%) Steatosis: 30-90% Steatohepatitis: 33-42% Fibrosis: Mild-to-Moderate Fibrosis: 33% Advanced Fibrosis: 12% Cirrhosis: 1-2% Advanced fibrosis ~14%

11 Hypercholesterolemia (55%) NAFLD High-Risk: Hyperlipidemia Adult Lipid Clinic Patients (n= 95) Hypertriglyceridemia (30%) Mixed dyslipidemia (15%) Dig Dis Sci 2000;45: Hypercholesterolemia (55%) NAFLD High-Risk: Hyperlipidemia Adult Lipid Clinic Patients (n= 95) Hypertriglyceridemia (30%) Mixed dyslipidemia (15%) Prevalence of NAFLD of = 50% Hypertriglyceridemia, mixed dyslipidemia risk 5-fold Dig Dis Sci 2000;45: NAFLD Increases with Increasing Age NAFLD occurs in all age groups Among adults, the prevalence of NAFLD increases with increasing age Prevalence of biopsy-proven NAFLD in traffic accident victims: 1% : < 20 years old 18% : years old 35% : 60 + years old Hilden et al. Scan J Gastro 1977; 12:593

12 NAFLD and Ethnicity/Race Different groups of individuals appear to be differentially affected by NAFLD NAFLD and Ethnicity/Race Different groups of individuals appear to be differentially affected by NAFLD Given the high prevalence of obesity and DM among African Americans NAFLD and Ethnicity/Race Different groups of individuals appear to be differentially affected by NAFLD Given the high prevalence of obesity and DM among African Americans Postulate that NAFLD should be more prevalent among this population

13 NAFLD and Ethnicity/Race Different groups of individuals appear to be differentially affected by NAFLD Given the high prevalence of obesity and DM among African Americans Postulate that NAFLD should be more prevalent among this population However, several studies have demonstrated the contrary Prevalence of Hepatic Steatosis Varies with Ethnicity and Race Fatty liver Prevalence (%) Dallas Heart Study Use of NMR to assess hepatic triglyceride content Population-based sample Hepatic Steatosis and Race/Ethnicity Fatty liver Prevalence (%) 45% Latino

14 Hepatic Steatosis and Race/Ethnicity Fatty liver Prevalence (%) 45% Latino 33% Caucasian Hepatic Steatosis and Race/Ethnicity Fatty liver Prevalence (%) 45% 33% 24% Latino Caucasian African American Hepatic Steatosis and Race/Ethnicity Fatty liver Prevalence (%) Median Hepatic Triglyceride Content 4.6% 45% Latino 3.6% 33% Caucasian 3.2% 24% African American

15 Hepatic Steatosis and Race/Ethnicity Fatty liver Prevalence (%) Median Hepatic Triglyceride Content 4.6% 45% Latino 3.6% 33% Caucasian 3.2% 24% African American Hepatic Steatosis and Race/Ethnicity Differences in hepatic triglyceride content were not explained by total, subcutaneous abdominal or lower extremity fat Intraperitoneal fat accounted for the majority of variation in hepatic triglyceride content among race/ethnic groups Hepatology 2009;49:791 Hepatic Steatosis and Race/Ethnicity Differences in hepatic triglyceride content were not explained by total, subcutaneous abdominal or lower extremity fat Intraperitoneal fat accounted for the majority of variation in hepatic triglyceride content among race/ethnic groups Very close association between intraperitoneal fat and liver fat, regardless of race/ethnicity Hepatology 2009;49:791

16 Genetics of NAFLD GWAS of NAFLD patients Identified rs738409, a SNP within PNPLA3 gene (patatin-like phopholipase domain-containing) Adiponutrin: highly expressed in liver and adipose, but exact role not fully understood Strongly associated with hepatic fat content Romeo, S. et al. Nat. Genet. 40, (2008) PNPLA3 SNP Hepatic fat content highest for GG homozygotes (2x higher than non-carriers) G allele: Most common in Hispanic individuals Intermediate frequency in Caucasians Lowest frequency in African Americans PNPLA3 SNP is also associated with increased necroinflammation and fibrosis in NASH Romeo, S. et al. Nat. Genet. 40, (2008) Natural History of NAFLD: Dependent on Histology Natural history depends upon the histologic subtype of NAFLD Simple Steatosis generally benign prognosis NASH may develop fibrosis leading to cirrhosis

17 Natural History of NAFLD Study of NAFLD outcomes in a community-based, outpatient population in Olmsted County, MN Diagnosis of NAFLD (n=435) Liver biopsy Hepatic imaging consistent with fatty liver Exclusion of other causes of liver disease and excessive alcohol use Median follow-up time = 7.6 years Adams et al. Gastro 2005;129:113 NAFLD Increases Mortality Significantly lower survival in NAFLD compared with general population NASH Histology Increases Mortality Risk No patients with simple steatosis died during follow-up 35% of patients with NASH died during follow-up Adams et al. Gastro 2005;129:113

18 Adams et al. Gastro # 1 # 2 # 3 Adams et al. Gastro Risk Factors for Fibrosis/Cirrhosis Obesity Age > Diabetes Hypertension Smoking Fructose Intake Fast Food Consumption Sedentary Lifestyle

19 Risk Factors for Fibrosis/Cirrhosis Obesity Age > Diabetes Hypertension Smoking Fructose Intake Fast Food Consumption Sedentary Lifestyle 66% prevalence of advanced hepatic fibrosis if: Age > 50 and Obese and DM NASH-Cirrhosis: Increases Mortality and HCC Risk Child Class A Cirrhosis Sanyal et al, Hepatology 2006, 43: NAFLD and Cardiovascular Disease Overall, the available evidence demonstrates: Patients with NAFLD have multiple risk factors for CVD Patients with NASH (compared with simple steatosis): 3-fold increased incidence of cardiovascular disease 2-fold increase in cardiovascular mortality

20 NAFLD and Cardiovascular Disease Overall, the available evidence demonstrates: Patients with NAFLD have multiple risk factors for CVD Patients with NASH (compared with simple steatosis): 3-fold increased incidence of cardiovascular disease 2-fold increase in cardiovascular mortality CVD is much more common than liver disease as a cause of death, especially with NASH The association between NAFLD and CVD is independent of diabetes status Who are NAFLD Suspects? Who are NAFLD Suspects?

21 Who are NAFLD Suspects? Who are NAFLD Suspects? Lab Evaluation for NAFLD No specific, widely available serologic markers for distinguishing NASH from Simple Steatosis

22 Promising Biochemical Marker for NASH: CK 18 Cytokeratin 18 (CK 18) Fragments Measure of apoptosis Hepatocyte apoptosis is a key pathway of liver injury and cell death in NASH Hepatocyte apoptosis NASH >> Simple Steatosis Promising Biochemical Marker for NASH: CK 18 Cytokeratin 18 (CK 18) Fragments Measure of apoptosis Hepatocyte apoptosis is a key pathway of liver injury and cell death in NASH Hepatocyte apoptosis NASH >> Simple Steatosis CK 18 fragments NASH >> Simple Steatosis Very promising test, but not yet routinely available Assess Severity of Liver Disease: Looking for NASH and Fibrosis Liver Biopsy = Gold standard Important component of the evaluation for NAFLD Necessary to definitively diagnose NASH Limitations: Sampling error Invasive Expense

23 Assess Severity of Liver Disease: Fibrosis To restrict the large number of potential candidates with suspected NAFLD for liver biopsy, several non-invasive surrogate markers of fibrosis have been investigated NASH Fibrosis Score FIB 4 AST/ALT BARD In clinical practice these scores may reduce the proportion of patients undergoing liver biopsy to diagnose mild disease Management Options: Targeting Metabolic Derangements NAFLD severity is associated with metabolic comorbidities Manage (prevent) metabolic derangements Typical therapies for metabolic disorders are generally safe in patients with NAFLD Rationale for Therapeutics for NASH Insulin sensitizers Insulin resistance FFA + insulin+ cytokines metabolic dysregulation ER stress Oxidative stress Mitochondrial injury Anti oxidants Nuclear Transcription Factors and AMP-activated protein kinase (AMPK) represent novel targets for NAFLD Inflammatory signaling Stellate cell activation fibrosis Apoptosis Cell death Vitamin E: Lipophylic anti-oxidant; blocks propagation of lipid peroxidation

24 Management Options: Therapy Specific for NAFLD BENEFICIAL Insulin sensitizers : TZDs Vitamin E : PIVENS Trial Weight Loss (+/- Bariatric Surgery) Management Options: Therapy Specific for NAFLD BENEFICIAL Insulin sensitizers : TZDs Vitamin E : PIVENS Trial Weight Loss (+/- Bariatric Surgery) STILL UNPROVEN Lipid lowering agents: Statins, fibrates Metformin Other Antioxidants: Betaine, SAMe Probiotics Insulin secretagogues TNF-alpha inhibitors (Pentoxifylline) Milk Thistle Management Options: Therapy Specific for NAFLD BENEFICIAL Insulin sensitizers : TZDs Vitamin E : PIVENS Trial Weight Loss (+/- Bariatric Surgery) STILL UNPROVEN Lipid lowering agents: Statins, fibrates Metformin Other Antioxidants: Betaine, SAMe Probiotics Insulin secretagogues TNF-alpha inhibitors (Pentoxifylline) Milk Thistle NOT BENEFICIAL Ursodeoxycholic acid

25 PIVENS CLINICAL TRIAL: PIOGLITAZONE, VITAMIN E, OR PLACEBO FOR NASH Sanyal AJ, Chalasani N, Kowdley KV, et al. For the NASH Clinical Research Network Vitamin E is Superior to Placebo for Improving NASH in Nondiabetic Patients NEJM 2010; 362: 1675 PIVENS Vitamin E vs. Pioglitazone vs. Placebo Wk 96 Nondiabetic patients with NASH (N = 247) Vitamin E 800 IU QD + Pioglitazone-like Placebo (n = 84) Pioglitazone 30 mg QD + Vitamin E-like Placebo (n = 80) Pioglitazone- + Vitamin E-like Placebos QD (n = 83) Sanyal AJ, et al. N Engl J Med. 2010;362: Vitamin E Improves NASH Vitamin E, but not pioglitazone, resulted in significant overall histologic improvement in NASH at Wk 96 when compared with placebo (p <.025) NNT with vitamin E to achieve histologic improvement in 1 patient: % of patients showed histologic improvement with Vitamin E 57% non-responders Sanyal AJ, et al. N Engl J Med. 2010;362:

26 Vitamin E and Pioglitazone Improve Steatosis and Inflammation Significantly higher rates of improved steatosis and lobular inflammation with vitamin E and pioglitazone vs placebo Patients With Improvement (%) P = P < Steatosis P = P < Lobular Inflammation P = P = Hepatocellular Ballooning P =.24 P = Fibrosis Vitamin E Pioglitazone Placebo Sanyal AJ, et al. N Engl J Med. 2010;362: PIVENS Pioglitazone associated with significant improvement in insulin resistance but also significant weight gain (5.5kg) Changes observed by Wk 24 Weight gain progressed out to Wk 96 After cessation of Pioglitazone: Insulin resistance returned to baseline Weight gain persisted Sanyal AJ, et al. N Engl J Med. 2010;362: Vitamin E: Caveats High Dose Vitamin E Supplementation May Increase All- Cause Mortality Significant association between dose of Vitamin E and all-cause mortality Vitamin E is associated with HR 1.17 for prostate cancer (p=0.008) Annals of Internal Medicine 2005 JAMA 2011

27 Additional Management Options for NAFLD Weight loss (at least 7%) Gastric Bypass Surgery Reduce steatosis, generally beneficial for steatohepatitis, inconsistent in fibrosis Dietary Changes Decrease fructose consumption, saturated fats, simple carbohydrates and trans fats Increased fructose consumption (>7 servings/week) is associated with increased fibrosis, inflammation and ballooning in NAFLD patients Increase PUFAs and Omega 3 FA Additional Management Options for NAFLD Increase physical activity Improvement in cardiorespiratory fitness, even in absence of weight loss, has been shown to improve NASH histology Abnormal Liver Tests or Liver Imaging, metabolic features Assess clinical risk factors for having NASH +/- fibrosis to categorize the degree of risk Consider Vitamin E Clinical Trials

28 Key Concepts for NAFLD 1. NAFLD is very prevalent among U.S. adults, affecting up to 46% of individuals Especially prevalent among patients with diabetes, affecting 40-70% 2. NASH is the more aggressive form of NAFLD 6-13% of the U.S. adult population 3. Liver biopsy is still necessary to distinguish between simple steatosis and NASH 4. NASH can, and does, occur in the setting of normal aminotransferases (~20% of cases) 5. Risk factors for fibrosis in NAFLD include: Age > years, Diabetes, Obesity, HTN, Smoking, Fructose consumption, Fast Food Consumption, Sedentary lifestyle Key Concepts for NAFLD 6. NASH is associated with reduced survival compared with the general population (top 3 causes of death with NAFLD: #1: Malignancy; #2: Ischemic Heart Disease; #3: Liver Disease) 7. Aerobic activity, dietary modification and weight loss are associated with improvements in NASH. Vitamin E is a therapeutic option for selected patients with NASH 8. Though commonly used, metformin has not been shown to consistently improve NASH histology. Though patients frequently ask about it, there is no data suggesting that milk thistle is beneficial for NASH 9. No FDA approved specific medications for NASH, but numerous clinical trials utilizing novel agents are in progress, capitalizing on the emerging data on NAFLD pathogenesis