Hepatocyte TMEM16A Deletion Retards NAFLD Progression by Ameliorating Hepatic Glucose Metabolic Disorder.

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent form of chronic liver disease, and the mechanisms underpinning its pathogenesis have not been completely established. Transmembrane member 16A (TMEM16A), a component of the Ca2+-activated chloride channel (CaCC), has recently been implicated in metabolic events. Herein, TMEM16A is shown to be responsible for CaCC activation in hepatocytes and is increased in liver tissues of mice and patients with NAFLD. Hepatocyte-specific ablation of TMEM16A in mice ameliorates high-fat diet-induced obesity, hepatic glucose metabolic disorder, steatosis, insulin resistance, and inflammation. In contrast, hepatocyte-specific TMEM16A transgenic mice exhibit the opposite phenotype. Mechanistically, hepatocyte TMEM16A interacts with vesicle-associated membrane protein 3 (VAMP3) to induce its degradation, suppressing the formation of the VAMP3/syntaxin 4 and VAMP3/synaptosome-associated protein 23 complexes. This leads to the impairment of hepatic glucose transporter 2 (GLUT2) translocation and glucose uptake. Notably, VAMP3 overexpression restrains the functions of hepatocyte TMEM16A in blocking GLUT2 translocation and promoting lipid deposition, insulin resistance, and inflammation. In contrast, VAMP3 knockdown reverses the beneficial effects of TMEM16A downregulation. This study demonstrates a role for TMEM16A in NAFLD and suggests that inhibition of hepatic TMEM16A or disruption of TMEM16A/VAMP3 interaction may provide a new potential therapeutic strategy for NAFLD.

Accumulating pathways of γ-aminobutyric acid during anaerobic and aerobic sequential incubations in fresh tea leaves.

The roles of the γ-aminobutyric acid (GABA) shunt and polyamine (PA) degradation pathway on GABA accumulation were investigated in fresh tea leaves under anaerobic and aerobic sequential incubations. The GABA accumulation was mainly completed in the first anaerobic incubation through the interaction of the GABA shunt with the PA degradation pathway. When treated with aminoguanidine, the diamine oxidase and polyamine oxidase activities were almost completely inhibited, and the GABA contents decreased by 40.7%, 46.4%, 41.0% and 37.5% in the tea leaves of the four cultivars 'Fuyun No. 6', 'Fudingdabai', 'Longjing No. 43' and 'Pingyangtezao', respectively. The glutamate decarboxylase activity decreased significantly, and the accumulation of GABA may increase or decrease because of varietal differences, which occurred mainly relying on the PA degradation pathway during the second anaerobic incubation. Thus, approximately 37%-47% of the GABA formed in fresh tea leaves under hypoxia was supplied by the PA pathway.

ClC-3 chloride channel/antiporter defect contributes to inflammatory bowel disease in humans and mice.

BACKGROUND: ClC-3 channel/antiporter plays a critical role in a variety of cellular activities. ClC-3 has been detected in the ileum and colon. OBJECTIVE: To determine the functions of ClC-3 in the gastrointestinal tract. DESIGN: After administration of dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzenesulfonic acid (TNBS), intestines from ClC-3-/- and wild-type mice were examined by histological, cellular, molecular and biochemical approaches. ClC-3 expression was determined by western blot and immunostaining. RESULTS: ClC-3 expression was reduced in intestinal tissues from patients with UC or Crohn's disease and from mice treated with DSS. Genetic deletion of ClC-3 increased the susceptibility of mice to DSS- or TNBS-induced experimental colitis and prevented intestinal recovery. ClC-3 deficiency promoted DSS-induced apoptosis of intestinal epithelial cells through the mitochondria pathway. ClC-3 interacts with voltage-dependent anion channel 1, a key player in regulation of mitochondria cytochrome c release, but DSS treatment decreased this interaction. In addition, lack of ClC-3 reduced the numbers of Paneth cells and impaired the expression of antimicrobial peptides. These alterations led to dysfunction of the epithelial barrier and invasion of commensal bacteria into the mucosa. CONCLUSIONS: A defect in ClC-3 may contribute to the pathogenesis of IBD by promoting intestinal epithelial cell apoptosis and Paneth cell loss, suggesting that modulation of ClC-3 expression might be a new strategy for the treatment of IBD.