New US research has shown that vitamin D levels are associated with a number of important outcomes and markers in patients taking HIV treatment. Published in the online edition of Antiviral Therapy, investigators found that vitamin D was associated with CD4 cell count after starting antiretroviral therapy, markers of inflammation, and an important indicator of increased cardiovascular risk.
“Many of the emerging complications related to chronic HIV infection represent disease processes where vitamin D is known to play an important role,” comment the investigators.
They believe that their results are of such importance that “a randomized placebo-controlled interventional trial is crucial to determine what effect vitamin D may have on surrogate markers of CVD [cardiovascular disease], as well as on immune function and reconstitution, and to determine what vitamin D level is optimal in HIV-positive patients.”
Earlier research has already shown that vitamin D deficiency is common in patients with HIV. In addition, studies conducted in the general population have shown that low levels of this vitamin are associated with an increased risk of cardiovascular disease.
In particular, deficient levels of the vitamin have been associated with increased carotid intima-media thickness (IMT), an important indicator of hardening of the arteries, a major risk factor for cardiovascular disease. It has been suggested that this could be because the vitamin plays an important role in the inflammatory process. Furthermore, Vitamin D is also known to be involved in immune function.
Because of these findings, investigators in Atlanta undertook a study involving HIV-positive patients. It had three main aims:
To see if vitamin D was related to makers of inflammation in HIV infection.
To evaluate the association between the vitamin and carotid IMT.
To examine the relationship between vitamin D and immune function.
A secondary aim was to compare these outcomes with an HIV-negative control population.
All the HIV-positive patients were aged over 18 years and had been taking antiretroviral therapy for at least six months. The study was conducted in the modern HIV treatment era – between 2005 and 2009.
A total of 149 HIV-infected patients and 34 controls were recruited. There were important differences between these two populations. Patients with HIV were older (49 vs. 38 years); were more likely to be male (85% vs. 62%); and were also more likely to be smokers (49% vs. 18%).
Patients with HIV had been living with the infection for an average of twelve years. Most (82%) had an undetectable viral load, and the average CD4 cell count was 572 cells/mm3.
Vitamin D levels were significantly higher in the HIV-negative controls (p = 0.02).
In the patients with HIV, low vitamin D levels were associated with increased inflammation (p = 0.02) and lower CD4 cell count (p = 0.04).
Vitamin D levels were also associated with the degree of CD4 cell increase since starting antiretroviral treatment, noted the investigators. They add, “the clinical implications of this finding warrants further investigation to see whether vitamin D supplementation given at the same time as initiation of ART would offer a safe and effective means of augmenting the immune restoration response to treatment.”
Low levels of the vitamin were also associated with thickening of the carotid artery (p = 0.001).
“Patients with [carotid artery] IMT levels above the median were >10 times more likely to have the lowest levels of [vitamin] D,” write the authors, “these data suggest that a high [vitamin] D level may be protective against CVD development in HIV-positive people. Studies in the general population support this finding.”
The investigators acknowledge that a limitation of their research was the small sample sizes. Nevertheless, they conclude: “our results show that vitamin D is associated with immune restoration, as well as IMT, which supports the fact that vitamin D may play a role in both HIV-related CVD and immune restoration.”
Ross AC et al. Vitamin D is linked to carotid intima-media thickness and immune reconstitution in HIV-positive individuals. Antiviral Therapy, online edition: doi: 10.3851/IMP1784, 2011.