Sanderson, Schuyler O.

Objective: Allelic variation (rs738409C→G) in adiponutrin (patatin‐like phospholipase domain‐containing protein 3, PNPLA3) has been associated with hepatic steatosis and liver fibrosis. The physiologic impact of the PNPLA3 G allele may be exacerbated in patients with severe obesity. In this study, we investigated the interactions of PNPLA3 rs738409 with a broad panel of metabolic and histologic characteristics of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH) in patients with medically complicated obesity.Design and Methods: Consecutive patients undergoing bariatric surgery were selected for a prospective study. They underwent extensive laboratory and histologic (liver biopsy) assessment, as well as evaluation of rs738409 polymorphism by TaqMan assay.Results: Only 12 (8.3%) of the 144 patients had normal liver histology, with 72 (50%) NASH, of whom 15 (10.4% of total patients) had fibrosis stage 2‐3. PNPLA3 GG genotype correlated positively (P < 0.05) with serum levels of alanine aminotransferase (ALT), asparate aminotransferase (AST), glucose, fibrinogen, and insulin‐dependent diabetes mellitus, homeostasis model assessment—insulin resistance, and presence of NASH. Multivariate analysis indicated that PNPLA3 rs738409 G versus C allele remained an (independent) risk factor for NASH, in addition to CK‐18 >145 IU/l, glucose >100 mg/dl, and C‐reactive protein (CRP) >0.8 mg/dl. The probability of NASH increased from 9% (no risk factor) to 82% if all four risk factors were present.Conclusions: In this cohort of patients with medically complicated obesity, PNPLA3 rs738409 G allelic expression is associated with hepatic (NASH) and nonhepatic complications of obesity, such as insulin resistance. These novel findings may be related to a greater impact of PNPLA3 variant in magnitude and scope in patients with severe obesity than in less obese populations. Further studies are needed to characterize the nature of these associations.

AbstractBackground and AimsLiver‐related clinical consequences of non‐alcoholic fatty liver disease (NAFLD) are seen only in the minority of patients with advanced fibrosis. The aim of our study was to generate insight into a potential endocrine basis of steatohepatitis with advanced fibrosis in NAFLD.MethodsBiopsy and blood samples were prospectively collected from patients with medically complicated obesity. Patients were categorized, according to liver histology, into: (i) normal, (ii) simple steatosis (SS), (iii) non‐alcoholic steatohepatitis (NASH) with fibrosis stage (FS) 0–1 and (iv) NASH with FS ≥ 2. A broad panel of potential biomarkers included DHEA‐S, growth hormone (GH), homeostasis model assessment‐insulin resistance (HOMA‐IR), leptin, resistin, adiponectin and cytokeratin 18 (CK‐18) fragments.ResultsWe studied 160 patients (mean BMI 46.8 ± 8.2 kg/m2). Liver biopsies demonstrated normal histology in 10%, SS in 45%, NASH with FS 0–1 in 37.5% and NASH with FS ≥ 2 in 7.5%. C‐reactive protein, IL‐6, GH, CK‐18, adiponectin, HOMA‐IR and quantitative insulin sensitivity check index (QUICKI) were significantly associated with NASH in univariate analysis, but overall predictivity of these parameters was low (AUC ROC = 0.62–0.68). In contrast, all patients with NASH with FS ≥ 2 had insulin resistance, as measured by QUICKI, and GH levels <0.45 ng/ml and all but one patient with NASH FS 2–3 had low DHEA levels (<123 μg/dl).ConclusionsLow serum levels of GH and DHEA are very common in patients with NASH with more advanced fibrosis. Other biomarkers, including CK‐18 fragment levels, have predictivity characteristics that would be of low clinical utility for distinguishing patients with normal histology or SS from those with NASH. These findings demonstrate an endocrine profile associated with advanced fibrosis.

Although there are small animal platforms that recapitulate some of the histological features of nonalcoholic fatty liver disease, there are no small animal models of nonalcoholic steatohepatitis (NASH) with consistent hepatocellular ballooning and progressive fibrosis that also exhibit fidelity to the human condition physiologically. We examined the metabolic and histological effects of a diet on the basis of the composition of “fast food” (high saturated fats, cholesterol, and fructose). Mice ( n = 8 in each group) were assigned to diets as follows: 1) standard chow (SC), i.e., 13% energy as fat [1% saturated fatty acids (SFA)], 2) high fat (HF), i.e., 60% energy as fat (1% SFA), and 3) fast food (FF), i.e., 40% energy as fat (12% SFA, 2% cholesterol). All three diets were supplemented with high fructose. All diets produced obesity. The HF and FF diets produced insulin resistance. Liver histology was normal in animals fed the SC diet. Steatohepatitis with pronounced ballooning and progressive fibrosis (stage 2) was observed in mice fed the FF diet. Although the HF diet produced obesity, insulin resistance, and some steatosis; inflammation was minimal, and there was no increase in fibrosis. The FF diet produced a gene expression signature of increased fibrosis, inflammation, and endoplasmic reticulum stress and lipoapoptosis. A diet based on high cholesterol, high saturated fat, and high fructose recapitulates features of the metabolic syndrome and NASH with progressive fibrosis. This represents a novel small animal model of fibrosing NASH with high fidelity to the human condition. These results highlight the contribution of dietary composition to the development of nonalcoholic fatty liver disease and NASH.