analysis of bacterial metabolism of glutamate and GABA in the gut in a rat model of obesity and type 2 diabetes.

Dysbiosis of gut microbiota has adverse effects on host health. This study aimed to determine the effects of changes of faecal microbiota in obese and diabetic rats on the imputed production of enzymes involved in the metabolism of glutamate, gamma-aminobutyric acid (GABA), and succinate. The levels of glutamate decarboxylase, GABA transaminase, succinate-semialdehyde dehydrogenase, and methylisocitrate lyase were reduced or absent in diabetic rats compared with controls and obese rats. Glutamate decarboxylase (GAD) was significantly reduced in obese rats compared with control rats, while the other enzymes were unaltered; different bacterial taxa are suggested to be involved. Levels of bacterial enzymes were inversely correlated with the blood glucose level. These findings suggest that the absence of GABA and reduced succinate metabolism from gut microbiota contribute to the diabetic state in rats.