Jeffrey B. Schwimmer

Prevalence of fatty liver in children and adolescents.

OBJECTIVE. Fatty liver disease is diagnosed increasingly in children, but the prevalence remains unknown. We sought to determine the prevalence of pediatric fatty liver as diagnosed by histology in a population-based sample. METHODS. We conducted a retrospective review of 742 children between the ages of 2 and 19 years who had an autopsy performed by a county medical examiner from 1993 to 2003. Fatty liver was defined as ≥5% of hepatocytes containing macrovesicular fat. RESULTS. Fatty liver was present in 13% of subjects. For children and adolescents age 2 to 19 years, the prevalence of fatty liver adjusted for age, gender, race, and ethnicity is estimated to be 9.6%. Fatty liver prevalence increases with age, ranging from 0.7% for ages 2 to 4 up to 17.3% for ages 15 to 19 years. Fatty liver prevalence differs significantly by race and ethnicity (Asian: 10.2%; black: 1.5%; Hispanic: 11.8%; white: 8.6%). The highest rate of fatty liver was seen in obese children (38%). CONCLUSIONS. Fatty liver is the most common liver abnormality in children age 2 to 19 years. The presence of macrovesicular hepatic steatosis in ∼1 of every 10 children has important ramifications for the long-term health of children and young adults. The influence of the risk factors identified should be taken into consideration in the development of protocols designed to screen at-risk children and adolescents.

Effect of Vitamin E or Metformin for Treatment of Nonalcoholic Fatty Liver Disease in Children and Adolescents: The TONIC Randomized Controlled Trial

CONTEXT Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in US children and adolescents and can present with advanced fibrosis or nonalcoholic steatohepatitis (NASH). No treatment has been established. OBJECTIVE To determine whether children with NAFLD would improve from therapeutic intervention with vitamin E or metformin. DESIGN, SETTING, AND PATIENTS Randomized, double-blind, double-dummy, placebo-controlled clinical trial conducted at 10 university clinical research centers in 173 patients (aged 8-17 years) with biopsy-confirmed NAFLD conducted between September 2005 and March 2010. Interventions Daily dosing of 800 IU of vitamin E (58 patients), 1000 mg of metformin (57 patients), or placebo (58 patients) for 96 weeks. MAIN OUTCOME MEASURES The primary outcome was sustained reduction in alanine aminotransferase (ALT) defined as 50% or less of the baseline level or 40 U/L or less at visits every 12 weeks from 48 to 96 weeks of treatment. Improvements in histological features of NAFLD and resolution of NASH were secondary outcome measures. RESULTS Sustained reduction in ALT level was similar to placebo (10/58; 17%; 95% CI, 9% to 29%) in both the vitamin E (15/58; 26%; 95% CI, 15% to 39%; P = .26) and metformin treatment groups (9/57; 16%; 95% CI, 7% to 28%; P = .83). The mean change in ALT level from baseline to 96 weeks was -35.2 U/L (95% CI, -56.9 to -13.5) with placebo vs -48.3 U/L (95% CI, -66.8 to -29.8) with vitamin E (P = .07) and -41.7 U/L (95% CI, -62.9 to -20.5) with metformin (P = .40). The mean change at 96 weeks in hepatocellular ballooning scores was 0.1 with placebo (95% CI, -0.2 to 0.3) vs -0.5 with vitamin E (95% CI, -0.8 to -0.3; P = .006) and -0.3 with metformin (95% CI, -0.6 to -0.0; P = .04); and in NAFLD activity score, -0.7 with placebo (95% CI, -1.3 to -0.2) vs -1.8 with vitamin E (95% CI, -2.4 to -1.2; P = .02) and -1.1 with metformin (95% CI, -1.7 to -0.5; P = .25). Among children with NASH, the proportion who resolved at 96 weeks was 28% with placebo (95% CI, 15% to 45%; 11/39) vs 58% with vitamin E (95% CI, 42% to 73%; 25/43; P = .006) and 41% with metformin (95% CI, 26% to 58%; 16/39; P = .23). Compared with placebo, neither therapy demonstrated significant improvements in other histological features. CONCLUSION Neither vitamin E nor metformin was superior to placebo in attaining the primary outcome of sustained reduction in ALT level in patients with pediatric NAFLD. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00063635.

Histopathology of pediatric nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are common in children and adolescents. However, standard histological criteria for pediatric NAFLD and NASH are undeveloped. We reviewed consecutive patients ages 2 to 18 years with biopsy‐proven NAFLD diagnosed between 1997 and 2003. Biopsies were evaluated by two pathologists for individual features of steatohepatitis. Agglomerative hierarchical cluster analysis demonstrated two different forms of steatohepatitis. Type 1 was characterized by steatosis, ballooning degeneration, and perisinusoidal fibrosis; type 2 was characterized by steatosis, portal inflammation, and portal fibrosis. The study included 100 children with NAFLD. Simple steatosis was present in 16% of subjects, and advanced fibrosis was present in 8%. Type 1 NASH was present in 17% of subjects, and type 2 NASH was present in 51%. Boys were significantly (P < .01) more likely to have type 2 NASH and less likely to have type 1 NASH than girls. The NASH type differed significantly (P < .001) by race and ethnicity. Type 1 NASH was more common in white children, whereas type 2 NASH was more common in children of Asian, Native American, and Hispanic ethnicity. In cases of advanced fibrosis, the pattern was generally that of type 2 NASH. In conclusion, type 1 and type 2 NASH are distinct subtypes of pediatric NAFLD, and type 2 is the most common pattern in children. NASH subtypes should be considered when interpreting liver biopsies and planning studies of the pathophysiology, genetics, natural history, or response to treatment in pediatric NAFLD. (HEPATOLOGY 2005;42:641–649.)

Obesity, insulin resistance, and other clinicopathological correlates of pediatric nonalcoholic fatty liver disease.

OBJECTIVE To describe the clinical characteristics of nonalcoholic fatty liver disease (NAFLD) in children, including insulin resistance, and to test for correlation with liver pathology. STUDY DESIGN A retrospective review of children with biopsy-proven NAFLD at Childrens Hospital San Diego from 1999 to 2002. Liver biopsy specimens were independently reviewed by two pathologists. RESULTS Children with NAFLD (n=43) were mostly male (70%), Hispanic American (53%) and obese (88%). The criteria for insulin resistance were met by 95% of subjects. Steatosis was predicted by the combination of quantitative insulin sensitivity check index, age, and ethnicity (P<.0001). Portal inflammation was predicted by the combination of ALT and fasting insulin (P=.0009). Perisinusoidal fibrosis was predicted by the combination of AST, fasting insulin, and BMI Z score (P<.0001). Portal fibrosis was predicted by the combination of right upper quadrant pain and homeostasis model assessment of insulin resistance (P=.0028). CONCLUSIONS We identified significant predictors of liver pathology in children with NAFLD. Children being evaluated for NAFLD should be screened for insulin resistance, which is nearly universal and correlates with liver histology.

Influence of Gender, Race, and Ethnicity on Suspected Fatty Liver in Obese Adolescents

Objectives. Fatty liver is a common cause of liver disease in children. However, the epidemiology of pediatric fatty liver is limited to single-center case series of nonalcoholic fatty liver disease (NAFLD). Obesity and insulin resistance are major established risk factors for NAFLD. The role of gender, race, and ethnicity on the prevalence of fatty liver in obese children is unknown. Methods. We recruited obese 12th-grade participants from the Child and Adolescent Trial for Cardiovascular Health in California, Louisiana, Minnesota, and Texas. Serum samples were collected at school when the participants were well. Alanine aminotransferase (ALT) was measured by kinetic enzymatic assay, and ALT >40 U/L was defined as abnormal. Causes of abnormal ALT other than NAFLD were excluded by serum testing. Results. A total of 127 obese students (73 female, 54 male) had a mean BMI of 35.2 kg/m2. Unexplained ALT elevation was present in 23% of participants overall. The mean ALT for participants with normal values was 28 U/L and for participants with an abnormal ALT was 56 U/L. Abnormal ALT was significantly more prevalent in boys (44%) than in girls (7%). The prevalence of abnormal ALT differed significantly by race and ethnicity (Hispanic: 36%; white: 22%; black: 14%). Serum ALT value was significantly predicted by the combination of gender, race/ethnicity, and BMI. After controlling for gender and BMI, Hispanic ethnicity significantly predicted greater ALT than black race. Conclusions. In a national, school-based sample of obese adolescents, boys were 6 times more likely than girls to have an unexplained elevated ALT. Given that participants were well and causes of chronic liver disease were excluded, we speculate that obese adolescent boys have an increased prevalence of fatty liver compared with obese adolescent girls. This population-based study also supports the hypothesis that NAFLD is more common in Hispanic adolescents. These findings have implications for both disease screening and studies of fatty liver pathophysiology.

Cardiovascular Risk Factors and the Metabolic Syndrome in Pediatric Nonalcoholic Fatty Liver Disease

Background— Nonalcoholic fatty liver disease (NAFLD), the most common cause of liver disease in children, is associated with obesity and insulin resistance. However, the relationship between NAFLD and cardiovascular risk factors in children is not fully understood. The objective of this study was to determine the association between NAFLD and the presence of metabolic syndrome in overweight and obese children. Methods and Results— This case-control study of 150 overweight children with biopsy-proven NAFLD and 150 overweight children without NAFLD compared rates of metabolic syndrome using Adult Treatment Panel III criteria. Cases and controls were well matched in age, sex, and severity of obesity. Children with NAFLD had significantly higher fasting glucose, insulin, total cholesterol, low-density lipoprotein cholesterol, triglycerides, systolic blood pressure, and diastolic blood pressure than overweight and obese children without NAFLD. Subjects with NAFLD also had significantly lower high-density lipoprotein cholesterol than controls. After adjustment for age, sex, race, ethnicity, body mass index, and hyperinsulinemia, children with metabolic syndrome had 5.0 (95% confidence interval, 2.6 to 9.7) times the odds of having NAFLD as overweight and obese children without metabolic syndrome. Conclusions— NAFLD in overweight and obese children is strongly associated with multiple cardiovascular risk factors. The identification of NAFLD in a child should prompt global counseling to address nutrition, physical activity, and avoidance of smoking to prevent the development of cardiovascular disease and type 2 diabetes.

Heritability of Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the United States. The etiology is believed to be multifactorial with a substantial genetic component; however, the heritability of NAFLD is undetermined. Therefore, a familial aggregation study was performed to test the hypothesis that NAFLD is highly heritable. METHODS Overweight children with biopsy-proven NAFLD and overweight children without NAFLD served as probands. Family members were studied, including the use of magnetic resonance imaging to quantify liver fat fraction. Fatty liver was defined as a liver fat fraction of 5% or higher. Etiologies for fatty liver other than NAFLD were excluded. Narrow-sense heritability estimates for fatty liver (dichotomous) and fat fraction (continuous) were calculated using variance components analysis adjusted for covariate effects. RESULTS Fatty liver was present in 17% of siblings and 37% of parents of overweight children without NAFLD. Fatty liver was significantly more common in siblings (59%) and parents (78%) of children with NAFLD. Liver fat fraction was correlated with body mass index, although the correlation was significantly stronger for families of children with NAFLD than those without NAFLD. Adjusted for age, sex, race, and body mass index, the heritability of fatty liver was 1.000 and of liver fat fraction was 0.386. CONCLUSIONS Family members of children with NAFLD should be considered at high risk for NAFLD. These data suggest that familial factors are a major determinant of whether an individual has NAFLD. Studies examining the complex relations between genes and environment in the development and progression of NAFLD are warranted.

Suspected Nonalcoholic Fatty Liver Disease and Mortality Risk in a Population-based Cohort Study

OBJECTIVE:Case series suggest that nonalcoholic fatty liver disease (NAFLD) is associated with increased all-cause and cardiovascular mortality. The current study compared the survival of subjects with and without suspected NAFLD in a population-based cohort, and placed the finding in the context of previously published case series.METHODS:Primary analysis assessed mortality for NHANES-III participants with and without suspected NAFLD using the National Death Index. Suspected NAFLD was based upon unexplained ALT elevation. The Olmsted County and Cleveland Clinic case series were also used for comparison. Survivals were compared using Proportional Hazards Model and direct age standardization.RESULTS:The NHANES cohort included 980 with and 6,594 subjects without suspected NAFLD. Over a mean of 8.7 yr, suspected NAFLD had a hazards ratio of 1.37 (95% CI 0.98–1.91) for all-cause mortality. In the 45–54 age group, suspected NAFLD had significantly higher all-cause (4.40 95% CI 1.27–13.23) and cardiovascular mortality (8.15, 95% CI 2.00–33.20) after adjusting for conventional cardiovascular risk factors. The age-standardized rate per 10,000 per year was 129 (95% CI 118–140) for the NHANES non-NAFLD cohort, 154 (95% CI 116–198) for the NHANES suspected NAFLD cohort, 214 (95% CI 157–279) for the Olmsted County series, and 426 (95% CI 298–573) for the Cleveland Clinic series.CONCLUSION:The magnitude of mortality risk in NAFLD depends on the setting and method of ascertainment. Suspected NAFLD in the 45–54 age group is a strong independent risk factor for cardiovascular death and warrants further cardiovascular risk management guidelines.

Nonalcoholic Fatty Liver Disease: Diagnostic and Fat-Grading Accuracy of Low-Flip-Angle Multiecho Gradient-Recalled-Echo MR Imaging at 1.5 T

PURPOSE To assess the accuracy of four fat quantification methods at low-flip-angle multiecho gradient-recalled-echo (GRE) magnetic resonance (MR) imaging in nonalcoholic fatty liver disease (NAFLD) by using MR spectroscopy as the reference standard. MATERIALS AND METHODS In this institutional review board-approved, HIPAA-compliant prospective study, 110 subjects (29 with biopsy-confirmed NAFLD, 50 overweight and at risk for NAFLD, and 31 healthy volunteers) (mean age, 32.6 years +/- 15.6 [standard deviation]; range, 8-66 years) gave informed consent and underwent MR spectroscopy and GRE MR imaging of the liver. Spectroscopy involved a long repetition time (to suppress T1 effects) and multiple echo times (to estimate T2 effects); the reference fat fraction (FF) was calculated from T2-corrected fat and water spectral peak areas. Imaging involved a low flip angle (to suppress T1 effects) and multiple echo times (to estimate T2* effects); imaging FF was calculated by using four analysis methods of progressive complexity: dual echo, triple echo, multiecho, and multiinterference. All methods except dual echo corrected for T2* effects. The multiinterference method corrected for multiple spectral interference effects of fat. For each method, the accuracy for diagnosis of fatty liver, as defined with a spectroscopic threshold, was assessed by estimating sensitivity and specificity; fat-grading accuracy was assessed by comparing imaging and spectroscopic FF values by using linear regression. RESULTS Dual-echo, triple-echo, multiecho, and multiinterference methods had a sensitivity of 0.817, 0.967, 0.950, and 0.983 and a specificity of 1.000, 0.880, 1.000, and 0.880, respectively. On the basis of regression slope and intercept, the multiinterference (slope, 0.98; intercept, 0.91%) method had high fat-grading accuracy without statistically significant error (P > .05). Dual-echo (slope, 0.98; intercept, -2.90%), triple-echo (slope, 0.94; intercept, 1.42%), and multiecho (slope, 0.85; intercept, -0.15%) methods had statistically significant error (P < .05). CONCLUSION Relaxation- and interference-corrected fat quantification at low-flip-angle multiecho GRE MR imaging provides high diagnostic and fat-grading accuracy in NAFLD.

Pediatric nonalcoholic fatty liver disease: a critical appraisal of current data and implications for future research.

Although population prevalence is very difficult to establish, nonalcoholic fatty liver disease (NAFLD) is probably the most common cause of liver disease in the preadolescent and adolescent age groups. There seems to be an increase in the prevalence of NAFLD, likely related to the dramatic rise in the incidence of obesity during the past 3 decades. Despite an increase in public awareness, overweight/obesity and related conditions, such as NAFLD, remain underdiagnosed by health care providers. Accurate diagnosis and staging of nonalcoholic steatohepatitis (NASH) requires liver biopsy. The development of noninvasive surrogate markers and the advancements in imaging technology will aid in the screening of large populations at risk for NAFLD. Two distinct histological patterns of NASH have been identified in the pediatric population, and discrete clinical and demographic features are observed in children with these 2 patterns. The propensity for NASH to develop in obese, insulin-resistant pubertal boys of Hispanic ethnicity or a non-Hispanic white race may provide clues to the pathogenesis of NAFLD in children. The natural history of pediatric NASH has yet to be defined, but most biopsies in this age group demonstrate some degree of fibrosis. In addition, cirrhosis can be observed in children as young as 10 years. While the optimal treatment of pediatric NAFLD has yet to be determined, lifestyle modification through diet and exercise should be attempted in children diagnosed with NAFLD. A large, multicenter trial of vitamin E and metformin is underway as part of the NASH clinical research network.