Aims/hypothesis Serum stearic acid (C18:0) is elevated in individuals with hyperlipidaemia and type 2 diabetes. However, the lipotoxicity induced by increased stearic acid in beta cells has not been well described. This study aimed to examine the adverse effects of stearic acid on beta cells and the potential mechanisms through which these are mediated. Methods Three groups of C57BL/6 mice were fed a normal diet or a high-stearic-acid/high-palmitic-acid diet for 24 weeks, respectively. The microRNA (miR) profiles of islets were determined by microarray screening. Islet injury was detected with co-staining using the TUNEL assay and insulin labelling. A lentiviral vector expressing anti-miRNA-34a-5p oligonucleotide (AMO-34a-5p) was injected into mice via an intraductal pancreatic route. Results In both mouse islets and cultured rat insulinoma INS-1 cells, stearic acid exhibited a stronger lipotoxic role than other fatty acids, owing to repression of B cell CLL/ lymphoma 2 (BCL-2) and BCL-2-like 2 (BCL-W) by stearic acid stimulation of miR-34a-5p. The stearic-acid-induced lipotoxicity and reduction in insulin secretion were alleviated by AMO-34a-5p. Further investigations in INS-1 cells revealed that p53 was involved in stearic-acid-induced elevation of miR-34a-5p, owing in part to activation of protein kinaselike endoplasmic reticulum kinase (PERK). Conversely, silencing PERK alleviated stearic-acid-induced p53, miR-34a-5p and lipotoxicity. Conclusions/interpretation These findings provide new insight for understanding the molecular mechanisms underlying not only the deleterious impact of stearic-acid-induced lipotoxicity but also apoptosis in beta cells and progression to type 2 diabetes.

Background & Aim-Abundantly expressed in the metabolically active cells including hepatocytes, N-nicotinamide methyltransferase (NNMT) catalyzes S-adenosylmethionine (SAM)dependent methylation/degradation of nicotinamide, the predominant precursor for intracellular nicotinamide adenine dinucleotide (NAD + ) regeneration via the salvage pathway. The enzyme is emerging to play an important role in regulating metabolism, however, the exact regulatory mechanism(s) underlying NNMT expression remains unclear and its potential implication in alcoholic liver disease (ALD) is completely unknown.Methods-Both traditional Lieber-De Carli and the NIAAA mouse model of ALD were employed. A small scale of chemical screening and ChIP assay were performed. NNMT inhibition was achieved via both genetic (adenoviral shRNA delivery) and pharmacological approach.Results-Chronic alcohol consumption induces liver endoplasmic reticulum (ER) stress and upregulates hepatic NNMT expression. ER stress inducers upregulated NNMT expression in both AML-12 hepatocytes and mice. PERK-ATF4 pathway activation is the main contributor in ER

Background and Aims Microbial dysbiosis is associated with alcohol‐related hepatitis (AH), with the mechanisms yet to be elucidated. The present study aimed to determine the effects of alcohol and zinc deficiency on Paneth cell (PC) antimicrobial peptides, α‐defensins, and to define the link between PC dysfunction and AH. Approach and Results Translocation of pathogen‐associated molecular patterns (PAMPs) was determined in patients with severe AH and in a mouse model of alcoholic steatohepatitis. Microbial composition and PC function were examined in mice. The link between α‐defensin dysfunction and AH was investigated in α‐defensin‐deficient mice. Synthetic human α‐defensin 5 (HD5) was orally given to alcohol‐fed mice to test the therapeutic potential. The role of zinc deficiency in α‐defensin was evaluated in acute and chronic mouse models of zinc deprivation. Hepatic inflammation was associated with PAMP translocation and lipocalin‐2 (LCN2) and chemokine (C‐X‐C motif) ligand 1 (CXCL1) elevation in patients with AH. Antibiotic treatment, lipopolysaccharide injection to mice, and in vitro experiments showed that PAMPs, but not alcohol, directly induced LCN2 and CXCL1. Chronic alcohol feeding caused systemic dysbiosis and PC α‐defensin reduction in mice. Knockout of functional α‐defensins synergistically affected alcohol‐perturbed bacterial composition and the gut barrier and exaggerated PAMP translocation and liver damage. Administration of HD5 effectively altered cecal microbial composition, especially increased Akkermansia muciniphila, and reversed the alcohol‐induced deleterious effects. Zinc‐regulated PC homeostasis and α‐defensins function at multiple levels, and dietary zinc deficiency exaggerated the deleterious effect of alcohol on PC bactericidal activity. Conclusions Taken together, the study suggests that alcohol‐induced PC α‐defensin dysfunction is mediated by zinc deficiency and involved in the pathogenesis of AH. HD5 administration may represent a promising therapeutic approach for treating AH.

Alcohol metabolism in the liver generates highly toxic acetaldehyde. Breakdown of acetaldehyde by aldehyde dehydrogenase 2 (ALDH2) in the mitochondria consumes NAD+ and generates reactive oxygen/nitrogen species, which represents a fundamental mechanism in the pathogenesis of alcoholic liver disease (ALD). A mitochondria-targeted lipophilic ubiquinone (MitoQ) has been shown to confer greater protection against oxidative damage in the mitochondria compared to untargeted antioxidants. The present study aimed to investigate if MitoQ could preserve mitochondrial ALDH2 activity and speed up acetaldehyde clearance, thereby protects against ALD. Male C57BL/6 J mice were exposed to alcohol for 8 weeks with MitoQ supplementation (5 mg/kg/d) for the last 4 weeks. MitoQ ameliorated alcohol-induced oxidative/nitrosative stress and glutathione deficiency. It also reversed alcohol-reduced hepatic ALDH activity and accelerated acetaldehyde clearance through modulating ALDH2 cysteine S-nitrosylation, tyrosine nitration and 4-hydroxynonenol adducts formation. MitoQ ameliorated nitric oxide (NO) donor-mediated ADLH2 S-nitrosylation and nitration in Hepa-1c1c7 cells under glutathion depletion condition. In addition, alcohol-increased circulating acetaldehyde levels were accompanied by reduced intestinal ALDH activity and impaired intestinal barrier. In accordance, MitoQ reversed alcohol-increased plasma endotoxin levels and hepatic toll-like receptor 4 (TLR4)-NF-κB signaling along with subsequent inhibition of inflammatory cell infiltration. MitoQ also reversed alcohol-induced hepatic lipid accumulation through enhancing fatty acid β-oxidation. Alcohol-induced ER stress and apoptotic cell death signaling were reversed by MitoQ. This study demonstrated that speeding up acetaldehyde clearance by preserving ALDH2 activity critically mediates the beneficial effect of MitoQ on alcohol-induced pathogenesis at the gut-liver axis.

Vitamin D deficiency is associated with the increase of circulating cholesterol in the people of northern China by enhancing hepatic cholesterol biosynthesis, which was linked to the reduction of transcriptional activity of VDR.