The pancreatic β-cell incretin response is modulated by mitochondrial transaminase GPT2

The effect of the incretin hormones GLP-1 and GIP to promote pancreatic β-cell function is exploited by an expansive menu of incretin mimetics for the treatment of type 2 diabetes (T2D); however, the incretin effect is well known to diminish as T2D progresses. Here, we show that silencing of stress-inducible mitochondrial protein glutamic pyruvate transaminase 2 (GPT2) enhances the β-cell incretin response. Mice with β-cell specific Gpt2 deficiency (Gpt2βKO) have improved oral glucose tolerance and insulin secretion due to enhanced β-cell incretin sensitivity. In the diet induced obesity (DIO) model of T2D, Gpt2βKO mice maintained lower non-fasting glucose and improved oral glucose tolerance and insulin secretion. The effect of GLP-1 receptor (GLP-1R) agonism on β-cell survival was also enhanced in Gpt2βKO islets. GPT2 was markedly induced in human islets from donors with type 2 diabetes and in non-diabetic donor islets exposed to glucolipotoxicity. Silencing GPT2 in human β-cells enhanced β-cell incretin sensitivity and survival, and it reversed incretin unresponsiveness in T2D islets. These findings raise GPT2 as a therapeutic target to mitigate β-cell dysfunction in T2D.