Difference between diabetic and nondiabetic smokers in the pituitary response to physical exercise.

The growth hormone (GH), cortisol, and arginine vasopressin (AVP) responses to bicycle ergometry (with increasing workload until exhaustion) were measured in 20 patients affected by insulin-dependent diabetes mellitus (IDDM) (10 habitual smokers and 10 nonsmokers) and 20 nondiabetic subjects (normal controls) (10 habitual smokers and 10 nonsmokers). Cardiorespiratory parameters such as heart rate, blood pressure, ventilation, frequency of breathing, tidal volume, oxygen consumption (Vo(2)), carbondioxide production (Vco(2)), and respiratory exchange ratio (R) were monitored before and during exercise tests. No significant differences between groups were observed; furthermore, there were no differences in circulating somatomedin-C (SM-C) and free fatty acids (FFA) levels between groups. Blood glucose levels were similar before exercise and followed a similar pattern during tests in diabetic smokers and nonsmokers. Basal GH, cortisol, and AVP levels were similar in diabetic smokers, diabetic nonsmokers, normal smokers, and normal nonsmokers. In all groups, exercise induced a significant increase in the serum concentrations of all examined hormones. Increments were significantly higher in diabetic than in nondiabetic groups. No significant differences were observed between diabetic smokers and nonsmokers for all examined hormones. AVP responses during tests were similar in normal smokers and nonsmokers. In contrast, exercise-induced GH and cortisol increments were significantly lower in normal smokers than in normal nonsmokers. These data support the hypothesis that in normal subjects habitual nicotine consumption may attenuate both GH and cortisol responses to a releasing stimulation, such as physical exercise. This phenomenon may represent an expression of adaptation of nicotinic neurotransmission to chronic stimulation. Furthermore, the data show that the effect induced by habitual smoking is absent in diabetics, probably because of diabetes-induced neuroendocrine alterations in the central nervous system.

Evidence for early impairment of glucagon-like peptide 1-induced insulin secretion in human type 2 (non insulin-dependent) diabetes.

UNLABELLED: To investigate a possible role of an enteroinsular axis involvement in the pathogenesis of type 2 diabetes, plasma glucagon-like peptide 1 (GLP-1) 7-36 amide response to nutrient ingestion was evaluated in type 2 diabetics affected by different degrees of beta-cell dysfunction. METHODS: 14 patients on oral hypoglycaemic treatment (group A: HbA1C = 8.1 +/- 1.8 %) and 11 age-matched diabetic patients on diet only (group B: HbA1C = 6.4 +/- 0.9) participated in the study. 10 healthy volunteers were studied as controls. In the postabsorptive state, a mixed meal (700 kCal) was administered to all subjects, and blood samples were regularly collected up to 180' for plasma glucose, insulin, glucagon, and GLP-1 determination. RESULTS: In the control group, the test meal induced a significant increase in plasma GLP-1 at 30' and 60' (p < 0.01); the peptide concentrations then returning toward basal levels. beta-cell function estimation by HOMA score confirmed a more advanced involvement in group A than in group B (p < 0.01). In contrast, the insulin resistance degree showed a similar result in the two groups (HOMA-R). In group A, first-phase postprandial insulin secretion (0 - 60') resulted, as expected, in being significantly reduced compared to healthy subjects (p < 0.001). In the same patients the mean fasting GLP-1 value was similar to controls, but the meal failed to increase plasma peptide levels, which even tended to decrease during the test (p < 0.01). In group B, food-mediated early insulin secretion was higher than in group A (p < 0.001), although significantly reduced when compared to controls (p < 0.01). Like group A, no GLP-1 response to food ingestion occurred in group B patients in spite of maintained basal peptide secretion. Whereas the test-meal did not significantly modify plasma glucagon levels in the control group, glucagon concentrations increased at 30' and 60' in both diabetic groups (p < 0.01). CONCLUSIONS: 1) The functional integrity of GLP-1 cells results as being seriously impaired even in the condition of mild diabetes; 2) the early peptide failure could contribute to the development of beta-cell deterioration which characterizes overt type 2 diabetes.