Diabetes is associated with increased risk for kidney and liver diseases, congestive heart failure, and mortality. Urinary glucose excretion using sodiumglucose cotransporter 2 (SGLT2) inhibitors prevents these adverse outcomes, however the mechanisms involved are not clear. Herein, we generated a roadmap of the metabolic alterations that occur in the kidney, liver, and heart in diabetes and in response to SGLT2 inhibition. We performed in vivo metabolic labeling with 13 C-glucose in normoglycemic and diabetic mice treated with or without the SGLT2 inhibitor dapagliflozin, followed by simultaneous metabolomics and metabolic flux analyses in different organs and the plasma.We found that in diabetes, glycolysis and glucose oxidation are impaired in the kidney, liver, and heart. Treatment with dapagliflozin failed to rescue glycolysis and further inhibited pyruvate kinase activity in the liver. SGLT2 inhibition increased glucose oxidation in all organs; in the kidney, this effect was associated with modulation of the redox state, which may protect against oxidative stress. In addition, diabetes was associated with altered methionine cycle metabolism, evident by decreased betaine and methionine levels, whereas treatment with SGLT2i increased hepatic betaine along with decreased homocysteine levels. mTORC1 activity was inhibited by SGLT2i along with stimulation of AMPK in both normoglycemic and diabetic animals, possibly explaining the protective effects against kidney, liver, and heart diseases. Collectively, our findings suggest that SGLT2i induces metabolic reprogramming orchestrated by AMPK-mTORC1 signaling with common and distinct effects in various tissues with implications for diabetes and aging.
The prevalence of obesity and non-alcoholic fatty liver (NAFL) is steadily increasing. Weight loss can lead to improvement in NAFL in patients and in model organisms. Weight loss can be achieved through either dietary and lifestyle interventions, pharmacotherapy, and bariatric surgery. Some interventions, such as intermittent fasting, have been purported to have benefits beyond those conferred by weight loss alone. In this study, rats were provided a high-fat, high-sucrose diet for 7 weeks and then were assigned to strict caloric restriction with intermittent fasting (IF-CR) or to sleeve gastrectomy (SG) bariatric surgery, achieving equivalent weight loss. The two interventions were compared to ad-libitum fed controls. The metabolome of the blood entering the liver was analyzed in the three experimental groups, as well as the metabolome and transcriptome of the liver under fasting conditions, to test how different means of weight loss affect the input of the liver and hepatic metabolism. Surprisingly, the two interventions had different and often opposite effects on the composition of portal blood and liver metabolites. IF-CR resulted in sweeping changes across multiple central metabolic pathways, including an increase in de novo lipogenesis and triglyceride export, and upregulation of glycolysis, citric acid cycle, and the pentose phosphate pathway, as well as an increase in glycogen storage. Meanwhile, the effects of SG concentrated on one-carbon metabolic pathways, with changes in metabolite and transcript levels pointing to decreased transmethylation and methionine cycle activity, with downstream effects on levels of glutathione and the hepatic oxidative state. In conclusion, our study highlights how different means of weight loss affect distinct metabolic pathways and demonstrates a unique effect of bariatric surgery on hepatic one-carbon and redox pathways.
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