Exercise-induced GH secretion is enhanced by the oral ingestion of melatonin in healthy adult male subjects

There is evidence that melatonin may play a role in modulating pituitary secretion, although the mechanisms are unclear.We examined the effects of a single dose of oral melatonin (5 mg) on exerciseinduced GH secretion. In a randomised, double-blind, placebo-controlled study, seven healthy male subjects undertook an initial period of graded bicycle ergometric exercise to determine maximum workload and oxygen uptake (VO2 max). Subjects were subsequently studied on two further occasions, receiving either melatonin or placebo in random order at the onset of each study (¹60 min). At 0 min a period of bicycle exercise was performed for 8 min at a workload corresponding to 70% of that achieved at VO2 max. Serum GH and IGF-binding protein-1 (IGFBP-1) concentration was measured at 15-min intervals from the onset of the study until 120 min post-exercise. Blood was also sampled for the measurement of plasma glucose, insulin, non-esterified fatty acids, IGFBP-3, melatonin and vasopressin concentration. There was an exercise-induced increase in GH concentration following melatonin which was greater compared with placebo as assessed by both area under the curve (

Forearm vasoconstrictor response in uncomplicated type 1 diabetes mellitus.

Contains fulltext : 50283.pdf (publisher's version ) (Closed access)BACKGROUND: According to the 'haemodynamic hypothesis', increased tissue perfusion predisposes to microangiopathy in diabetic patients. We hypothesized that the typical haemodynamic changes underlying the increased tissue perfusion can be explained by a decreased sympathetic nerve activity caused by chronic hyperglycaemia. In this study we investigated sympathetic activity in patients with uncomplicated type 1 diabetes mellitus (DM). MATERIALS AND METHODS: In 15 DM patients (DM duration 6.3 +/- 3.8 year; HbA1c 7.9 +/- 1.3%) and 16 age- and sex-matched healthy volunteers (Control), sympathetic nervous system activity was measured at rest (baseline) and during sympathoneural stimulation (lower body negative pressure (LBNP)) by means of interstitial and plasma noradrenaline (NA) sampling and power spectral analysis. Muscle sympathetic nerve activity (MSNA) was measured before (baseline) and during a cold pressure test. Forearm blood flow was measured during forearm vascular alpha- and beta-adrenergic receptor blockade. RESULTS: At baseline, forearm vascular resistance (FVR), plasma NA concentrations, MSNA and heart rate variability were similar in both groups. LBNP-induced vasoconstriction was significantly attenuated in the DM group compared with the Control group (DeltaFVR: 12 +/- 4 vs. 19 +/- 3 arbitrary units, P < 0.05). The responses of plasma NA and heart rate variability did not differ. CONCLUSIONS: Baseline FVR and sympathetic nerve activity are normal in patients with uncomplicated type 1 diabetes. However, the forearm vasoconstrictor response to sympathetic stimulation is attenuated, which cannot be attributed to an impaired sympathetic responsiveness

Extra-adrenal glucocorticoid synthesis in the intestinal epithelium: more than a drop in the ocean?

Glucocorticoids (GC) are lipophilic hormones commonly used as therapeutics in acute and chronic inflammatory disorders such as inflammatory bowel disease due to their attributed anti-inflammatory and immunosuppressive actions. Although the adrenal glands are the major source of endogenous GC, there is increasing evidence for the production of extra-adrenal GC in the brain, thymus, skin, vasculature, and the intestine. However, the physiological relevance of extra-adrenal-produced GC remains still ambiguous. Therefore, this review attracts attention to discuss possible biological benefits of extra-adrenal-synthesized GC, especially focusing on the impact of locally synthesized GC in the regulation of intestinal immune responses