Dataset Information

Depletion of B cell-activating factor attenuates hepatic fat accumulation in a murine model of nonalcoholic fatty liver disease.

ABSTRACT: Obesity-induced adipose-tissue dysfunction is a critical contributor to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). B cell-activating factor (BAFF) is an adipokine related to impaired insulin sensitivity, and the serum BAFF concentration is associated with NAFLD severity. In this study, we aimed to determine the direct in vivo role of BAFF in the development of insulin resistance, adipocyte dysfunction, and hepatic steatosis using BAFF-/- mice fed a high-fat diet (HFD). HFD-fed BAFF-/- mice exhibited significantly improved insulin sensitivity despite their increased weight gain and adiposity relative to HFD-fed wild-type mice. Moreover, inflammation, especially the accumulation of CD11c+ adipose-tissue macrophages, and fibrosis of epididymal adipose tissue were reduced, contributing to healthy adipose-tissue expansion in obese BAFF-/- mice. In line with metabolically healthy obesity, hepatic steatosis also decreased, and we observed attenuated de novo lipogenesis in both the livers and hepatocytes of BAFF-/- mice. Our data revealed that BAFF serves as a potential stimulator of unhealthy adipose-tissue expansion by triggering inflammation and fibrosis and ultimately leading to enhanced insulin resistance and NAFLD. Therefore, these results suggest that BAFF is a promising target for diabetes and NAFLD treatment.

SUBMITTER: Nakamura Y

PROVIDER: S-EPMC6353938 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Depletion of B cell-activating factor attenuates hepatic fat accumulation in a murine model of nonalcoholic fatty liver disease.

Nakamura Yoshiko Y Abe Masanori M Kawasaki Keitarou K Miyake Teruki T Watanabe Takao T Yoshida Osamu O Hirooka Masashi M Matsuura Bunzo B Hiasa Yoichi Y

Scientific reports 20190130 1

Obesity-induced adipose-tissue dysfunction is a critical contributor to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). B cell-activating factor (BAFF) is an adipokine related to impaired insulin sensitivity, and the serum BAFF concentration is associated with NAFLD severity. In this study, we aimed to determine the direct in vivo role of BAFF in the development of insulin resistance, adipocyte dysfunction, and hepatic steatosis using BAFF<sup>-/-</sup> mice fed a high-fat diet (HF ...[more]

PMID: 30700810

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Project description:BackgroundIn the past 30 years, incidences of non-alcoholic fatty liver disease (NAFLD) has risen by 30%. However, there is still no clear mechanism or accurate method of anticipating liver failure. Here we reveal the phase transitions of liquid crystalline qualities in hepatic lipid droplets (HLDs) as a novel method of anticipating prognosis.MethodsNAFLD was induced by feeding C57BL/6J mice on a high-fat (HiF) diet. These NAFLD livers were then evaluated under polarized microscopy, X-ray diffraction and small-angle scattering, lipid component chromatography analysis and protein expression analysis. Optically active HLDs from mouse model and patient samples were both then confirmed to have liquid crystal characteristics. Liver MAP1LC3A expression was then evaluated to determine the role of autophagy in liquid crystal HLD (LC-HLD) formation.ResultsUnlike the normal diet cohort, HiF diet mice developed NAFLD livers containing HLDs exhibiting Maltese cross birefringence, phase transition, and fluidity signature to liquid crystals. These LC-HLDs transitioned to anisotropic crystal at 0 °C and remain crystalline. Temperature increase to 42 °C causes both liquid crystal and crystal HLDs to convert to isotropic droplet form. These isotropic HLDs successfully transition to anisotropic LC with fast temperature decrease and anisotropic crystal with slow temperature decrease. These findings were duplicated in patient liver. Patient LC-HLDs with no inner optical activity were discovered, hinting at lipid saturation as the mechanism through which HLD acquire LC characteristics. Downregulation of MAP1LC3A in conjunction with increased LC-HLD also implicated autophagy in NAFLD LC-HLD formation.ConclusionsIncreasing concentrations of amphiphilic lipids in HLDs favors organization into alternating hydrophilic and hydrophobic layers, which present as LC-HLDs. Thus, evaluating the extent of liquid crystallization with phase transition in HLDs of NAFLD patients may reveal disease severity and predict impending liver damage.

Project description:CYP7B1 catalyzes mitochondria-derived cholesterol metabolites such as (25R)26-hydroxycholesterol (26HC) and 3β-hydroxy-5-cholesten-(25R)26-oic acid (3βHCA) and facilitates their conversion to bile acids. Disruption of 26HC/3βHCA metabolism in the absence of CYP7B1 leads to neonatal liver failure. Disrupted 26HC/3βHCA metabolism with reduced hepatic CYP7B1 expression is also found in nonalcoholic steatohepatitis (NASH). The current study aimed to understand the regulatory mechanism of mitochondrial cholesterol metabolites and their contribution to onset of NASH. We used Cyp7b1-/- mice fed a normal diet (ND), Western diet (WD), or high-cholesterol diet (HCD). Serum and liver cholesterol metabolites as well as hepatic gene expressions were comprehensively analyzed. Interestingly, 26HC/3βHCA levels were maintained at basal levels in ND-fed Cyp7b1-/- mice livers by the reduced cholesterol transport to mitochondria, and the upregulated glucuronidation and sulfation. However, WD-fed Cyp7b1-/- mice developed insulin resistance (IR) with subsequent 26HC/3βHCA accumulation due to overwhelmed glucuronidation/sulfation with facilitated mitochondrial cholesterol transport. Meanwhile, Cyp7b1-/- mice fed an HCD did not develop IR or subsequent evidence of liver toxicity. HCD-fed mice livers revealed marked cholesterol accumulation but no 26HC/3βHCA accumulation. The results suggest 26HC/3βHCA-induced cytotoxicity occurs when increased cholesterol transport into mitochondria is coupled to decreased 26HC/3βHCA metabolism driven with IR. Supportive evidence for cholesterol metabolite-driven hepatotoxicity is provided in a diet-induced nonalcoholic fatty liver mouse model and by human specimen analyses. This study uncovers an insulin-mediated regulatory pathway that drives the formation and accumulation of toxic cholesterol metabolites within the hepatocyte mitochondria, mechanistically connecting IR to cholesterol metabolite-induced hepatocyte toxicity which drives nonalcoholic fatty liver disease.

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Dataset Information

Depletion of B cell-activating factor attenuates hepatic fat accumulation in a murine model of nonalcoholic fatty liver disease.

Publications

Depletion of B cell-activating factor attenuates hepatic fat accumulation in a murine model of nonalcoholic fatty liver disease.

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