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 =
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.”