Intestinal gluconeogenesis prevents obesity-linked liver steatosis and non-alcoholic fatty liver disease.

OBJECTIVE: Hepatic steatosis accompanying obesity is a major health concern, since it may initiate non-alcoholic fatty liver disease (NAFLD) and associated complications like cirrhosis or cancer. Intestinal gluconeogenesis (IGN) is a recently described function that contributes to the metabolic benefits of specific macronutrients as protein or soluble fibre, via the initiation of a gut-brain nervous signal triggering brain-dependent regulations of peripheral metabolism. Here, we investigate the effects of IGN on liver metabolism, independently of its induction by the aforementioned macronutrients. DESIGN: To study the specific effects of IGN on hepatic metabolism, we used two transgenic mouse lines: one is knocked down for and the other overexpresses glucose-6-phosphatase, the key enzyme of endogenous glucose production, specifically in the intestine. RESULTS: We report that mice with a genetic overexpression of IGN are notably protected from the development of hepatic steatosis and the initiation of NAFLD on a hypercaloric diet. The protection relates to a diminution of de novo lipogenesis and lipid import, associated with benefits at the level of inflammation and fibrosis and linked to autonomous nervous system. Conversely, mice with genetic suppression of IGN spontaneously exhibit increased hepatic triglyceride storage associated with activated lipogenesis pathway, in the context of standard starch-enriched diet. The latter is corrected by portal glucose infusion mimicking IGN. CONCLUSION: We conclude that IGN per se has the capacity of preventing hepatic steatosis and its eventual evolution toward NAFLD.

Antiobesity effects of intestinal gluconeogenesis are mediated by the brown adipose tissue sympathetic nervous system.

OBJECTIVE: Intestinal gluconeogenesis (IGN), via the initiation of a gut-brain nervous circuit, accounts for the metabolic benefits linked to dietary proteins or fermentable fiber in rodents and has been positively correlated with the rapid amelioration of body weight after gastric bypass surgery in humans with obesity. In particular, the activation of IGN moderates the development of hepatic steatosis accompanying obesity. In this study, we investigated the specific effects of IGN on adipose tissue metabolism, independent of its induction by nutritional manipulation. METHODS: We used two transgenic mouse models of suppression or overexpression of G6pc1, the catalytic subunit of glucose-6 phosphatase, which is the key enzyme of endogenous glucose production specifically in the intestine. RESULTS: Under a hypercaloric diet, mice overexpressing IGN showed lower adiposity and higher thermogenic capacities than wild-type mice, featuring marked browning of white adipose tissue (WAT) and prevention of the whitening of brown adipose tissue (BAT). Sympathetic denervation restricted to BAT caused the loss of the antiobesity effects associated with IGN. Conversely, IGN-deficient mice exhibited an increase in adiposity under a standard diet, which was associated with decreased expression of markers of thermogenesis in both BAT and WAT. CONCLUSIONS: IGN is sufficient to activate the sympathetic nervous system and prevent the expansion and the metabolic alterations of BAT and WAT metabolism under a high-calorie diet, thereby preventing the development of obesity. These data increase knowledge of the mechanisms of weight reduction in gastric bypass surgery and pave the way for new approaches to prevent or cure obesity.