Plasma cortisol levels are associated with the first-phase insulin secretion in type 2 diabetes

Background Relationship between plasma cortisol levels and insulin secretion in patients with type 2 diabetes (T2DM) has not been clarified. This study investigated the correlation between them, especially the first-phase insulin secretion of islet β cells in patients with T2DM. Methods Cross-sectional analyses of baseline information were conducted on a cohort of 484 T2DM patients treated in Xiamen, China. All patients tested negative for GAD antibodies. Plasma cortisol levels were measured at 8am, 4pm, and 0am on the same day as cortisol rhythm. An overnight dexamethasone suppression test (1mg DST) was performed for patients with plasma cortisol levels > 50 nmol/L at 0am. Seventeen patients were excluded after 1mg DST. The first-phase insulin secretion of other 467 patients was calculated by the acute insulin response (AIR) through the arginine test. Multivariable linear regression models were used to examine the association of AIR with plasma cortisol levels. Results Among these 467 patients with T2DM (56 ± 12 years, 57% male), patients with higher AIR had higher levels of plasma uric acid, triglycerides, HOMA-β, and HOMA-IR (all P < 0.001), as well as shorter diabetes duration (P = 0.032), lower 8am plasma cortisol levels (P = 0.043), high-density lipoprotein cholesterol, glycosylated hemoglobin, and 0am plasma cortisol levels (all P < 0.001). After adjusting for confounding factors, AIR remained negatively correlated with plasma cortisol levels at 0am (β=-0.03, P = 0.003). Conclusion AIR was negatively correlated with plasma cortisol levels at 0am and 8am in T2DM. 0am plasma cortisol level was an independent risk factor for first-phase insulin secretion in T2DM patients.