Tumor necrosis factor alpha receptor 1 deficiency in hepatocytes does not protect from non-alcoholic steatohepatitis, but attenuates insulin resistance in mice

BACKGROUND End-stage liver disease caused by non-alcoholic steatohepatitis(NASH)is the second leading indication for liver transplantation.To date,only moderately effective pharmacotherapies exist to treat NASH.Understanding the pathogenesis of NASH is therefore crucial for the development of new therapies.The inflammatory cytokine tumor necrosis factor alpha(TNF-α)is important for the progression of liver disease.TNF signaling via TNF receptor 1(TNFR1)has been hypothesized to be important for the development of NASH and hepatocellular carcinoma in whole-body knockout animal models.AIM To investigate the role of TNFR1 signaling in hepatocytes for steatohepatitis development in a mouse model of diet-induced NASH.METHODS NASH was induced by a western-style fast-food diet in mice deficient for TNFR1 in hepatocytes(TNFR1ΔHEP)and their wild-type littermates(TNFR1fl/fl).Glucose tolerance was assessed after 18 wk and insulin resistance after 19 wk of feeding.After 20 wk mice were assessed for features of NASH and the metabolic syndrome such as liver weight,liver steatosis,liver fibrosis and markers of liver inflammation.RESULTS Obesity,liver injury,inflammation,steatosis and fibrosis was not different between TNFR1ΔHEP and TNFR1fl/fl mice.However,Tnfr1 deficiency in hepatocytes protected against glucose intolerance and insulin resistance.CONCLUSION Our results indicate that deficiency of TNFR1 signaling in hepatocytes does not protect from diet-induced NASH.However,improved insulin resistance in this model strengthens the role of the liver in glucose homeostasis.

Gut region-specific TNFR expression:TNFR2 is more affected than TNFR1 in duodenal myenteric ganglia of diabetic rats

BACKGROUND Cytokines are essential in autoimmune inflammatory processes that accompany type 1 diabetes.Tumor necrosis factor alpha plays a key role among others in modulating enteric neuroinflammation,however,it has a dual role in cell degeneration or survival depending on different TNFRs.In general,TNFR1 is believed to trigger apoptosis,while TNFR2 promotes cell regeneration.The importance of the neuronal microenvironment has been recently highlighted in gut region-specific diabetic enteric neuropathy,however,the expression and alterations of different TNFRs in the gastrointestinal tract has not been reported.AIM To investigate the TNFR1 and TNFR2 expression in myenteric ganglia and their environment in different intestinal segments of diabetic rats.METHODS Ten weeks after the onset of hyperglycemia,gut segments were taken from the duodenum,ileum and colon of streptozotocin-induced(60 mg/body weight kg i.p.)diabetic(n=17),insulin-treated diabetic(n=15)and sex-and age-matched control(n=15)rats.Myenteric plexus whole-mount preparations were prepared from different gut regions for TNFR1/HuCD or TNFR2/HuCD double-labeling fluorescent immunohistochemistry.TNFR1 and TNFR2 expression was evaluated by post-embedding immunogold electron microscopy on ultrathin sections of myenteric ganglia.TNFRs levels were measured by enzyme-linked immunosorbent assay in muscle/myenteric plexus-containing(MUSCLE-MP)tissue homogenates from different gut segments and experimental conditions.RESULTS A distinct region-dependent TNFRs expression was detected in controls.The density of TNFR1-labeling gold particles was lowest,while TNFR2 density was highest in duodenal ganglia and a decreased TNFRs expression from proximal to distal segments was observed in MUSCLE-MP homogenates.In diabetics,the TNFR2 density was only significantly altered in the duodenum with decrease in the ganglia(0.32±0.02 vs 0.45±0.04,P<0.05),while no significant changes in TNFR1 density was observed.In diabetic MUSCLE-MP homogenates,both TNFRs levels significantly decreased in the duodenum(TNFR1:4.06±0.65 vs 20.32±3.1,P<0.001;TNFR2:11.72±0.39 vs 15.91±1.04,P<0.01),which markedly influenced the TNFR2/TNFR1 proportion in both the ganglia and their muscular environment.Insulin treatment had controversial effects on TNFR expression.CONCLUSION Our findings show diabetes-related region-dependent changes in TNFR expression and suggest that TNFR2 is more affected than TNFR1 in myenteric ganglia in the duodenum of type 1 diabetic rats.