Insulin-like growth factor I, growth hormone, and insulin sensitivity: the effects of a one-year cholecalciferol supplementation in middle-aged overweight and obese subjects.
Endocrine. 2012 Oct 30.
Kamycheva E, Berg V, Jorde R.
Department of Medicine, University Hospital of North Norway, 9038, Tromsø, Norway, elena.kamycheva at unn.no.
Both altered GH-IGF-I axis and low serum levels of 25-hydroxyvitamin D (25(OH)D) are linked to measures of metabolic syndrome. Our hypothesis was that there is a relation between GH, IGF-I, and 25(OH)D; and that vitamin D supplementation may have an effect on the levels of GH, IGF-I, and IGF-I/IGFBP-3 ratio.
318 overweight and obese subjects completed a one-year randomized intervention with either 40,000 or 20,000 IU cholecalciferol per week or placebo. GH, IGF-I, IGFBP-3 and measures of insulin resistance were evaluated at baseline and at the end of study. There was a significant relation between entities of GH-IGF-I axis and insulin resistance.
Subjects with severe obesity had significantly lower serum 25(OH)D and had a significant linear decline in IGF-I/IGFBP-3 ratio with increasing serum 25(OH)D quartiles.
Vitamin D status was an independent predictor of GH-IGF-I axis and supplementation with vitamin D decreased IGF-I/IGFBP-3 ratio in subjects without severe obesity.
No corresponding effect of vitamin D supplementation on BMI or insulin resistance was observed. Adverse effects of GH-IGF-I axis on glucose metabolism and the development of metabolic syndrome may be in part associated with the changes in vitamin D status.
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