Insulin resistance, endocrine function and adipokines in type 2 diabetes patients at different glycaemic levels: potential impact for glucotoxicity in vivo.

OBJECTIVE: To evaluate the interplay between hyperglycaemia, insulin resistance, hormones and adipokines in patients with type 2 diabetes mellitus (T2DM). DESIGN AND METHODS: Ten patients with T2DM with good glycaemic control (G), 10 with poor control (P) and 10 nondiabetic control subjects (C) were matched for sex (M/F 6/4), age and body mass index. A hyperinsulinaemic, euglycaemic clamp was performed and cytokines and endocrine functions, including cortisol axis activity were assessed.
RESULTS: Patients with diabetes were more insulin resistant than group C, and group P exhibited the highest degree of insulin resistance (P = 0.01, P vs C). Tumour necrosis factor (TNF)-alpha levels were elevated in patients with diabetes (P = 0.05) and group P had the highest levels of fasting serum cortisol (P = 0.05), nonesterified fatty acids (NEFA; P = 0.06) and C-reactive protein (CRP; P = 0.01). Adiponectin levels were lower in the P group. In partial correlation analyses, significant associations were found: glycaemic level (HbA1c) with insulin resistance, TNF-alpha, CRP and basal and ACTH-stimulated cortisol levels, insulin resistance with plasma NEFA, TNF-alpha and stimulated cortisol levels.
CONCLUSION: Poor glycaemic control in patients with T2DM was associated with insulin resistance and with elevated TNF-alpha, CRP and basal as well as stimulated cortisol levels. Inflammatory mediators, e.g. TNF-alpha, may contribute to insulin resistance in hyperglycaemic patients with T2DM and this might be a partial explanation for glucotoxicity.