Song SO, et al. Diabetes Metab J. 2014 Oct;38(5):395-403. http://dx.doi.org/10.4093/dmj.2014.38.5.395

Sodium–glucose cotransporter 2 (SGLT2) inhibitors reduce cardiovascular events in humans with type 2 diabetes (T2D); however, the underlying mechanism remains unclear. Activation of the NLR family, pyrin domain-containing 3 (NLRP3) inflammasome and subsequent interleukin (IL)-1β release induces atherosclerosis and heart failure. Here we show the effect of SGLT2 inhibitor empagliflozin on NLRP3 inflammasome activity. Patients with T2D and high cardiovascular risk receive SGLT2 inhibitor or sulfonylurea for 30 days, with NLRP3 inflammasome activation analyzed in macrophages. While the SGLT2 inhibitor’s glucose-lowering capacity is similar to sulfonylurea, it shows a greater reduction in IL-1β secretion compared to sulfonylurea accompanied by increased serum β-hydroxybutyrate (BHB) and decreased serum insulin. Ex vivo experiments with macrophages verify the inhibitory effects of high BHB and low insulin levels on NLRP3 inflammasome activation. In conclusion, SGLT2 inhibitor attenuates NLRP3 inflammasome activation, which might help to explain its cardioprotective effects.

Metformin activates both PRKA and SIRT1. Furthermore, autophagy is induced by either the PRKA-MTOR-ULK1 or SIRT1-FOXO signaling pathways. We aimed to elucidate the mechanism by which metformin alleviates hepatosteatosis by examining the molecular interplay between SIRT1, PRKA, and autophagy. ob/ob mice were divided into 3 groups: one with ad libitum feeding of a standard chow diet, one with 300 mg/kg intraperitoneal metformin injections, and one with 3 g/d caloric restriction (CR) for a period of 4 wk. Primary hepatocytes or HepG2 cells were treated with oleic acid (OA) plus high glucose in the absence or presence of metformin. Both CR and metformin significantly improved body weight and glucose homeostasis, along with hepatic steatosis, in ob/ob mice. Furthermore, CR and metformin both upregulated SIRT1 expression and also stimulated autophagy induction and flux in vivo. Metformin also prevented OA with high glucose-induced suppression of both SIRT1 expression and SIRT1-dependent activation of autophagy machinery, thereby alleviating intracellular lipid accumulation in vitro. Interestingly, metformin treatment upregulated SIRT1 expression and activated PRKA even after siRNA-mediated knockdown of PRKAA1/2 and SIRT1, respectively. Taken together, these results suggest that metformin alleviates hepatic steatosis through PRKA-independent, SIRT1-mediated effects on the autophagy machinery.

Sarcopenia is associated with nonalcoholic fatty liver disease (NAFLD). This study investigated whether sarcopenia is associated with significant liver fibrosis in subjects with NAFLD. Data from the Korean National Health and Nutrition Examination Surveys 2008‐2011 database were analyzed. NALFD was defined by NAFLD liver fat score, comprehensive NAFLD score, or hepatic steatosis index. Degree of liver fibrosis was assessed by NAFLD fibrosis score (NFS), FIB‐4, and Forns index. Significant liver fibrosis was defined as FIB‐4 ≥2.67 and the highest quartile values of NFS and Forns index. Sarcopenia index (= total appendicular skeletal muscle mass [kg]/body mass index (kg/m²]) was calculated using dual‐energy X‐ray absorptiometry. Using the NAFLD liver fat score, NAFLD was identified in 2761 (28.5%) of 9676 subjects. Of subjects with NAFLD, sarcopenia was identified in 337 (12.2%). Sarcopenia was significantly associated with significant liver fibrosis assessed in fibrosis prediction models (all P < 0.05). In subgroups stratified according to body mass index and homeostasis model assessment of insulin resistance, a significant association between sarcopenia and significant liver fibrosis by NFS was consistently present (odds ratio = 1.76‐2.68 depending on the subgroup, all P < 0.05). Multivariate logistic regression analysis demonstrated an independent association between SI and significant liver fibrosis by NFS after adjusting for other confounders (odds ratio = 0.52‐0.67, all P < 0.01). Other NAFLD (comprehensive NAFLD score, hepatic steatosis index) and fibrosis prediction models (FIB‐4 and Forns index) produced similar results. Conclusion: Sarcopenia is associated with significant liver fibrosis in subjects with NAFLD, and the association is independent of obesity and insulin resistance. (Hepatology 2016;63:776–786)

Impairment in macroautophagy/autophagy flux and inflammasome activation are common characteristics of nonalcoholic steatohepatitis (NASH). Considering the lack of approved agents for treating NASH, drugs that can enhance autophagy and modulate inflammasome pathways may be beneficial. Here, we investigated the novel mechanism of ezetimibe, a widely prescribed drug for hypercholesterolemia, as a therapeutic option for ameliorating NASH. Human liver samples with steatosis and NASH were analyzed. For in vitro studies of autophagy and inflammasomes, primary mouse hepatocytes, human hepatoma cells, mouse embryonic fibroblasts with Ampk or Tsc2 knockout, and human or primary mouse macrophages were treated with ezetimibe and palmitate. Steatohepatitis and fibrosis were induced by feeding Atg7 wild-type, haploinsufficient, and knockout mice a methionine- and choline-deficient diet with ezetimibe (10 mg/kg) for 4 wk. Human livers with steatosis or NASH presented impaired autophagy with decreased nuclear TFEB and increased SQSTM1, MAP1LC3-II, and NLRP3 expression. Ezetimibe increased autophagy flux and concomitantly ameliorated lipid accumulation and apoptosis in palmitate-exposed hepatocytes. Ezetimibe induced AMPK phosphorylation and subsequent TFEB nuclear translocation, related to MAPK/ERK. In macrophages, ezetimibe blocked the NLRP3 inflammasome-IL1B pathway in an autophagy-dependent manner and modulated hepatocyte-macrophage interaction via extracellular vesicles. Ezetimibe attenuated lipid accumulation, inflammation, and fibrosis in liver-specific Atg7 wild-type and haploinsufficient mice, but not in knockout mice. Ezetimibe ameliorates steatohepatitis by autophagy induction through AMPK activation and TFEB nuclear translocation, related to an independent MTOR ameliorative effect and the MAPK/ERK pathway. Ezetimibe dampens NLRP3 inflammasome activation in macrophages by modulating autophagy and a hepatocyte-driven exosome pathway.