Metabolic, hormonal, oxidative, and inflammatory factors in pediatric obesity-related liver disease

Correlation of serum TNF-alpha levels and histologic liver injury scores in pediatric nonalcoholic fatty liver disease

We tested the power of tumor necrosis factor (TNF)-alpha and/or leptin in predicting the degree of liver involvement in children with nonalcoholic fatty liver disease (NAFLD). We measured serum levels of TNF-alpha and leptin and computed NAFLD activity score (NAS) (NAS >or= 5, diagnostic of nonalcoholic steatohepatitis [NASH]) in 72 consecutive biopsy-proven NAFLD cases (training and validation sets, 36 cases each). Univariate analysis evaluated variables significantly associated with a diagnostic NAS. Receiver operating characteristic (ROC) curve analysis assessed the diagnostic value of selected variables in predicting a NAS of 5 or more.TNF-alpha (P < .0001), leptin (P = .001); triglycerides (P = .013), and alkaline phosphatase (P = .046) levels were significantly associated with a NAS of 5 or more. TNF-alpha and leptin levels predicted the risk of NAS of 5 or more. ROC analyses defined cutoff values for TNF-alpha, leptin, and risk score. They identified 90%, 83%, and 83% of the cases, respectively, with a NAS of 5 or more (true-positive cases) from the validation set.TNF-alpha alone or combined with leptin in a simple risk score can accurately predict a NAS of 5 or more. TNF-alpha seems to be a specific laboratory marker of NASH.

MRI and ultrasound for hepatic fat quantification:relationships to clinical and metabolic characteristics of pediatric nonalcoholic fatty liver disease

OBJECTIVE

The aims of this study were to evaluate hepatic steatosis severity in a series of obese children through both magnetic resonance imaging (MRI) and ultrasound, and to correlate imaging findings to clinical and metabolic characteristics of the study population.

METHODS

Fifty obese children presenting hepatomegaly and/or elevated aminotransferases were candidates for assessment of hepatic fat fraction (HFF) by MRI. All subjects underwent dual energy X-ray absorptiometry scan measurement, and liver ultrasound scanning. Fasting blood samples were taken for the estimation of serum concentrations of glucose, insulin, leptin, aminotransferases and serum lipid profile.

RESULTS

A diagnosis of fatty liver was established by MRI in 20 (40%) children; of these, 12 had HFF of 9-18%, while the remaining ones had HFF of 19% or higher. HFF was not correlated to age, SDS-BMI, pubertal status and fat mass. HFF was positively associated with serum concentrations of alanine aminotransferase (ALT; r=0.62; p<0.0001) and AST (r=0.39; p=0.006), as well as with insulin (r=0.44; p=0.001) and insulin resistance (r=0.49; p<0.0001). Overall, ultrasound correlated well with MRI (p<0.0001). However, HFF ranged greatly in subjects with moderate (2-37%) as well as with severe (11-25%) degree of ultrasound hepatic steatosis. In fact, the mean hepatic fat fraction in children with severe steatosis was not statistically different from that found in patients with moderate steatosis (p=0.98). In multiple regression analysis, the most powerful predictors of elevated ALT, after correction for age, gender, BMI and pubertal status, were insulin resistance (p<0.01) and MRI HFF (p<0.0001).

CONCLUSIONS

Unlike sonography, an operator-dependent procedure, MRI is not subject to interpretation or inter-observer variation, and may be more useful than ultrasound for the monitoring of young patients with hepatic steatosis.

Risk for nonalcoholic fatty liver disease in Hispanic youth with BMI > or =95th percentile

OBJECTIVES

To characterize children at risk for nonalcoholic fatty liver disease (NAFLD) and to explore possible mechanisms underlying the development of NAFLD in Hispanic youth with a body mass index > or =95th percentile.

PATIENTS AND METHODS

Hispanic nonoverweight (n = 475) and overweight (n = 517) children, ages 4 to 19 y, were characterized in terms of body composition (dual-energy x-ray absorptiometry), maturation (Tanner stage), diet (24-h recall), physical activity (accelerometry), fitness (maximal oxygen uptake), and biochemical profile (fasting alanine aminotransferase [ALT], glucose, insulin, and lipids; inflammation markers such as adiponectin, leptin, C-reactive protein, and soluble intercellular adhesion molecule-1; and total antioxidants) using standard laboratory techniques. Risk for NAFLD was defined by fasting serum ALT values >97.5th percentile for age- and sex-specific reference values.

RESULTS

Fasting serum ALT was elevated in 24% of overweight children and in only 4% of nonoverweight children. Therefore, to identify risk factors associated with elevated ALT, the remaining statistical analysis was restricted to the overweight group. The percentage of overweight children with elevated ALT did not differ by sex, age, or Tanner stage. Weight, body mass index, z score, waist-to-hip ratio, fat-free mass, fat mass, and percent truncal fat mass were higher in the overweight children with elevated ALT. Fasting insulin, glucose, and homeostasis model-insulin resistance were higher in the overweight children with elevated ALT, as were triglycerides, total cholesterol, low-density lipoprotein, thyroid-stimulating hormone, and triiodothyronine. Fasting serum leptin, C-reactive protein, and soluble intercellular adhesion molecule-1 were significantly higher and adiponectin was lower in the overweight children with elevated ALT.

CONCLUSIONS

The risk for developing NAFLD was high in the overweight Hispanic children. The proportion of "at risk" children was not influenced by gender, age, or maturation. The risk for elevated ALT was predicted by the severity of obesity, central adiposity, hyperinsulinemia, hypertriglyceridemia, elevated thyroid-stimulating hormone, and systemic inflammation.

Predictors of non-alcoholic fatty liver disease in obese children

OBJECTIVE

To evaluate predictors of non-alcoholic fatty liver disease (NAFLD) in obese children.

DESIGN

Cross-sectional study.

SUBJECTS

Two hundred and sixty-eight obese children not consuming alcohol and without hepatitis B or C were consecutively studied at an auxology clinic.

MEASUREMENTS

Alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl-transferase (GGT), cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, triglycerides, uric acid, glucose, glucose during oral glucose tolerance testing (OGTT), insulin, insulin during OGTT, insulin resistance as estimated by homeostasis model assessment (HOMA), C-reactive protein (CRP), and systolic and diastolic blood pressure were measured. Fatty liver was diagnosed by ultrasonography using standard criteria. Univariable and multivariable logistic regression was used to evaluate predictors of NAFLD. All predictors except gender and pubertal status were modeled as continuous variables.

RESULTS

NAFLD was detected in 44% of obese children. At univariable analysis, male gender, Z-score of body mass index (BMI) (Z-BMI), ALT, AST, GGT, triglycerides, uric acid, glucose, glucose during OGTT, insulin, insulin during OGTT, HOMA, CRP and systolic blood pressure were predictors of NAFLD, whereas HDL-cholesterol and late-pubertal status were predictors of the normal liver. At multivariable analysis, however, only Z-BMI, ALT, uric acid, glucose during OGTT and insulin during OGTT were independent predictors of NAFLD.

CONCLUSION

Z-BMI, ALT, uric acid, glucose during OGTT and insulin during OGTT are independent predictors of NAFLD in Italian obese children, with most of the prediction explained by ALT and Z-BMI.

Obesity and inflammation in children

Systemic inflammation is present in children and adults with obesity. Inflammation associated with obesity appears to be central to the development of insulin resistance and atherosclerosis and may be important in the pathogenesis of other comorbid conditions. Although generally considered an inert energy storage tissue, white adipose tissue is a metabolically active organ. It produces a number of inflammatory cytokines and acute-phase reactants. Inflammation associated with obesity declines after weight loss and with exercise. It may also be possible to modify obesity-associated inflammation with medications, reducing comorbidities without weight loss. The study of inflammation in the context of excessive adipose tissue is central to understanding obesity and modifying its impact on patients.

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.

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Association of elevated serum ferritin levels and the risk of gestational diabetes mellitus in pregnant women: The Camden study

OBJECTIVE- We examined the influence of a moderately elevated serum ferritin level at entry to care on the risk of gestational diabetes mellitus (GDM) and a possible mechanism (increased iron stores versus inflammation). RESEARCH DESIGN AND METHODS- In a prospective observational study with 1,456 healthy pregnant women in Camden, New Jersey, serum ferritin and anthropometric measurements were determined. Serum C-reactive protein (CRP) concentration was measured in a nested case-control study of 172 subjects. RESULTS- Women who developed GDM had a higher concentration of serum ferritin than women who did not develop GDM (P < 0.001). Elevated serum ferritin level (highest quintile) was significantly and positively correlated with prepregnant BMI and skinfold measurements. Women in the highest quintile of serum ferritin had a twofold increased risk of developing GDM adjusted for several known risk factors (adjusted odds ratio, 2.02 [95% CI 1.04-3.92], P < 0.05). Similar results were obtained with a nested case-control study, in which women in the highest tertile of serum ferritin (2.35 [1.06-5.22], P < 0.05) or CRP (2.67 [1.16-6.17], P < 0.001) had a greater than twofold increased risk of GDM. However, these effects were modified and became nonstatistically significant after additional adjustment for prepregnant BMI. CONCLUSIONS- Elevated serum ferritin concentrations early in gestation are associated with an increased risk of GDM. The association, at least in part, is mediated by the maternal fat mass and obesity. These data suggest a possible link between elevated serum ferritin and low-grade inflammation.

Nonalcoholic fatty liver disease

NAFLD likely is the most common liver disease in children and is responsible for significant progression to cirrhosis, portal hypertension, and the need for liver transplantation in adults and even in some adolescents. Early diagnosis and lifestyle interventions appear to be our best hope for controlling progression of disease. The pediatrician is responsible for screening all obese children with measurement of aminotransferases. Those with elevated enzymes (particularly ALT) for longer than 3 months, in the absence of markers of hepatitis B or C, autoimmune chronic active hepatitis, Wilson's disease, hemochromatosis, or alpha-1-antitrypsin deficiency, should follow up with an abdominal ultrasound. In patients with a BMI in the morbidly obese range, an ultrasound to search for a diffusely echogenic liver should be performed even if the liver enzymes are normal. Findings suggestive of NAFLD should prompt the institution of appropriate dietary and exercise regimens. If these are unsuccessful after a 3-month trial, the patient should be referred to a pediatric gastroenterologist and hepatologist for further work-up and treatment, preferably in the context of a controlled therapeutic trial. Only by aggressively engaging this current epidemic will we be able to decrease the mounting human cost of NAFLD.