The Prevalence of Vitamin D Deficiency and Effects of Vitamin D Supplementation in HIV-1 Infected Patients

Vitamin D deficiency is common in, especially black, HIV-seropositive patients. Vitamin D deficiency can be caused by lack of sunlight and/or insufficient vitamin D intake via diet. The HIV infection itself and antiretroviral therapy (ART) may also cause vitamin D deficiency. ART interferes with cytochrome p450 activity and as such might affect vitamin D metabolism.

Vitamin D has several important physiological functions such as 1. regulation of calcium and phosphate homeostasis, 2. immunomodulatory properties and 3. effects on adipocyte differentiation. Low vitamin D levels lead to decreased bone mineralization, eventually resulting in rachitis(children) or osteomalacia (in adults). In addition vitamin D deficiency leads to secondary hyperparathyroidism, which leads to even more bone matrix demineralization. In HIV infected persons the overall prevalence of osteopenia and osteoporoses is 14-84% and 0-45% respectively. Vitamin D has been suggested to play a role in HIV-associated bone disorders. The vitamin D status also affects the host defence in HIV patients; a significantly lower CD4 cell count has been found in patients with 1,25(OH)vitamin D deficiency. Furthermore, the influence of vitamin D on adipocyte differentiation and the effect of HAART on vitamin D levels might be relevant for changes in fat distribution and the development of insulin resistance as is seen days after initiation of HAART.

Vitamin D is metabolized in the body trough cytochrome P450 enzymes. HAART might interact with vitamin D metabolism on basis of CYP3A4, which plays an important role in clearance of most antiretroviral agents and also showed to be a vitamin D 24 and 25-hydroxylase in vitro. We hypothesize that PI's lead to lower 1a,25(OH)2D3 by suppressing 1a- and 25-hydroxylase activity.

The results of our pilot showed that 25(OH)D deficiency is common among HIV patients. Seen the diversity of functions of vitamin D, we hypothesize that it's beneficial for the patients to have a normal vitamin D status. Therefore, supplementation of vitamin D is warranted.

In this study we want to investigate if, despite the complex interaction between HAART/ HIV and vitamin D metabolism, supplementation of colecalciferol (2000 IU daily) will lead to normalization of the vitamin D levels. Furthermore, we want to study the effects of normalization of vitamin D levels on bone mineral density, immune and adipocyte function. Therefore we will do a prospective, randomized, double-blind, placebo-controlled vitamin D intervention study in vitamin D deficient HIV1-seropositive patients.