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Obesity is associated with vitamin D (VD) deficiency and arterial stiffness. This randomized control trial assessed the effects of VD supplementation during a weight-loss program on carotid intima-media thickness (IMT) and carotid compliance in obese adolescents. Participants were randomly assigned to receive either a 12-week lifestyle program with VD supplementation (n = 13), a lifestyle program without VD supplementation (n = 13) or a control group composed of normal-weight adolescents (n = 18). Serum total and free 25-hydroxyvitamin D (25(OH)D), IMT and carotid compliance were measured before and after the trial. Insufficiency in 25(OH)D concentration was found in 73% of obese participants compared to 22% among controls. Obese adolescents had lower free 25(OH)D and displayed higher IMT but lower carotid compliance than controls. Free 25(OH)D and IMT were negatively correlated in adolescents displaying VD insufficiency at baseline. After three months, total and free 25(OH)D increased in both groups. The changes of IMT and carotid compliance were similar between groups. The changes in IMT were correlated with the changes in total 25(OH)D in obese adolescents with VD insufficiency at baseline (r = −0.59, p = 0.03). While the lifestyle program with VD supplementation did not affect carotid compliance, IMT reduction was improved in obese adolescents.

The aim of this study is to investigate the underlying mechanisms of the venoarteriolar reflex (VAR) in type 2 diabetes mellitus (T2DM), with and without peripheral neuropathy. Laser Doppler flowmetry (LDF) recordings were performed on the medial malleus and dorsal foot skin, before and during leg dependency in healthy controls, in persons with obesity, in those with T2DM, in those with T2DM and subclinical neuropathy, and in those with T2DM and confirmed neuropathy. LDF recordings were analyzed with the wavelet transform to evaluate the mechanisms controlling the flowmotion (i.e., endothelial nitric oxide-independent and -dependent, neurogenic, myogenic, respiratory and cardiac mechanisms). Skin blood perfusion decreased throughout leg dependency at both sites. The decrease was blunted in persons with confirmed neuropathy compared to those with T2DM alone and the controls. During leg dependency, total spectral power increased in all groups compared to rest. The relative contribution of the endothelial bands increased and of the myogenic band decreased, without differences between groups. Neurogenic contribution decreased in controls, in persons with obesity and in those with T2DM, whereas it increased in subclinical- and confirmed neuropathy. In conclusion, this study provides evidence that confirmed diabetic neuropathy alters the VAR through the neurogenic response to leg dependency.