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Reduced adiponectin signaling due to weight gain results in nonalcoholic steatohepatitis through impaired mitochondrial biogenesis.

ABSTRACT: Obesity and adiponectin depletion have been associated with the occurrence of nonalcoholic fatty liver disease (NAFLD). The goal of this study was to identify the relationship between weight gain, adiponectin signaling, and development of nonalcoholic steatohepatitis (NASH) in an obese, diabetic mouse model. Leptin-receptor deficient (Lepr(db/db) ) and C57BL/6 mice were administered a diet high in unsaturated fat (HF) (61%) or normal chow for 5 or 10 weeks. Liver histology was evaluated using steatosis, inflammation, and ballooning scores. Serum, adipose tissue, and liver were analyzed for changes in metabolic parameters, messenger RNA (mRNA), and protein levels. Lepr(db/db) HF mice developed marked obesity, hepatic steatosis, and more than 50% progressed to NASH at each timepoint. Serum adiponectin level demonstrated a strong inverse relationship with body mass (r =?-0.82; P < 0.0001) and adiponectin level was an independent predictor of NASH (13.6 ?g/mL; P < 0.05; area under the receiver operating curve (AUROC)?= 0.84). White adipose tissue of NASH mice was characterized by increased expression of genes linked to oxidative stress, macrophage infiltration, reduced adiponectin, and impaired lipid metabolism. HF lepr (db/db) NASH mice exhibited diminished hepatic adiponectin signaling evidenced by reduced levels of adiponectin receptor-2, inactivation of adenosine monophosphate activated protein kinase (AMPK), and decreased expression of genes involved in mitochondrial biogenesis and ?-oxidation (Cox4, Nrf1, Pgc1?, Pgc1? and Tfam). In contrast, recombinant adiponectin administration up-regulated the expression of mitochondrial genes in AML-12 hepatocytes, with or without lipid-loading.Lepr(db/db) mice fed a diet high in unsaturated fat develop weight gain and NASH through adiponectin depletion, which is associated with adipose tissue inflammation and hepatic mitochondrial dysfunction. We propose that this murine model of NASH may provide novel insights into the mechanism for development of human NASH.

SUBMITTER: Handa P

PROVIDER: S-EPMC5993561 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Reduced adiponectin signaling due to weight gain results in nonalcoholic steatohepatitis through impaired mitochondrial biogenesis.

Handa Priya P Maliken Bryan D BD Nelson James E JE Morgan-Stevenson Vicki V Messner Donald J DJ Dhillon Barjinderjit K BK Klintworth Heather M HM Beauchamp Mary M Yeh Matthew M MM Elfers Clinton T CT Roth Christian L CL Kowdley Kris V KV

Hepatology (Baltimore, Md.) 20140527 1

<h4>Unlabelled</h4>Obesity and adiponectin depletion have been associated with the occurrence of nonalcoholic fatty liver disease (NAFLD). The goal of this study was to identify the relationship between weight gain, adiponectin signaling, and development of nonalcoholic steatohepatitis (NASH) in an obese, diabetic mouse model. Leptin-receptor deficient (Lepr(db/db) ) and C57BL/6 mice were administered a diet high in unsaturated fat (HF) (61%) or normal chow for 5 or 10 weeks. Liver histology was ...[more]

PMID: 24464605

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Project description:Adiponectin exerts beneficial effects by reducing inflammation and improving lipid metabolism and insulin sensitivity. Although the adiponectin level is lower in obese individuals, whether weight gain reduces adiponectin expression in humans is controversial. We sought to investigate the role of weight gain, and consequent changes in leptin, on altering adiponectin expression in humans.Forty-four normal-weight healthy subjects were recruited (mean age 29 years; 14 women) and randomized to either gain 5% of body weight by 8 weeks of overfeeding (n=34) or maintain weight (n=10). Modest weight gain of 3.8±1.2?kg resulted in increased adiponectin level (P=0.03), whereas weight maintenance resulted in no changes in adiponectin. Further, changes in adiponectin correlated positively with changes in leptin (P=0.0085). In-vitro experiments using differentiated human white preadipocytes showed that leptin increased adiponectin mRNA and protein expression, whereas a leptin antagonist had opposite effects. To understand the role of leptin in established obesity, we compared adipose tissue samples obtained from normal-weight versus obese subjects. We noted, first, that leptin activated cellular signaling pathways and increased adiponectin mRNA in the adipose tissue from normal-weight participants, but did not do so in the adipose tissue from obese participants. Second, we noted that obese subjects had increased caveolin-1 expression, which attenuates leptin-dependent increases in adiponectin.Modest weight gain in healthy individuals is associated with increases in adiponectin levels, which correlate positively with changes in leptin. In vitro, leptin induces adiponectin expression, which is attenuated by increased caveolin-1 expression. In addition, the adipose tissue from obese subjects shows increased caveolin-1 expression and impaired leptin signaling. This leptin signal impairment may prevent concordant increases in adiponectin levels in obese subjects despite their high levels of leptin. Therefore, impaired leptin signaling may contribute to low adiponectin expression in obesity and may provide a target for increasing adiponectin expression, hence improving insulin sensitivity and cardio-metabolic profile in obesity.

Project description:Hepatocellular injury and inflammation are believed to be the primary drivers of fibrogenesis that ultimately lead to cirrhosis in patients with nonalcoholic steatohepatitis (NASH). This study sought associations between observed improvements in fibrosis with improvement in specific histologic features, nonalcoholic fatty liver disease activity score (NAS) ≥2, diagnostic category, and primary histologically based outcomes of two adult NASH treatment trials. The primary outcome for the study was fibrosis improvement from baseline to end of treatment, defined as a 1-point or more improvement in fibrosis stage. This is a retrospective analysis of biopsy data collected from the NASH Clinical Research Network Pathology Committee of Pioglitazone versus Vitamin E versus Placebo for the Treatment of Nondiabetic Patients with NASH Trial (PIVENS) and Farnesoid X Receptor Ligand Obeticholic Acid in NASH Treatment Trial (FLINT) baseline and final biopsies. Treatment group-adjusted univariable and multivariable logistic regression models related improvement in fibrosis to improvements in other histologic variables, resolution of steatohepatitis, and improvement in the NAS ≥2. In PIVENS 221 subjects had baseline and 96-week biopsies, and in FLINT 200 subjects had baseline and 72-week biopsies. Improvement in fibrosis was found in 38% of PIVENS and 29% of FLINT biopsies; fibrosis improvement was more likely in treated than placebo subjects in both studies. Controlling for treatment group, fibrosis improvement was associated most strongly with resolution of NASH (PIVENS, odds ratio [OR], 3.9; 95% confidence interval [CI] 2.0-7.6; P < 0.001; FLINT, OR, 8.0; 95% CI 3.1-20.9; P < 0.001), and improved NAS by ≥2 (PIVENS, OR, 2.4; 95% CI 1.3-4.3; P = 0.003; FLINT, OR, 4.2; 95% CI 2.1-8.3; P < 0.001). Improvement in histologic features associated with improved fibrosis for both studies included steatosis, ballooning, Mallory-Denk bodies, and portal, but not lobular, inflammation. Conclusion: These findings support a strong link between histologic resolution of steatohepatitis with improvement in fibrosis in NASH.

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Reduced adiponectin signaling due to weight gain results in nonalcoholic steatohepatitis through impaired mitochondrial biogenesis.

Publications

Reduced adiponectin signaling due to weight gain results in nonalcoholic steatohepatitis through impaired mitochondrial biogenesis.

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