HTB

Vitamin D deficiencies in HIV management

Nathan Geffen, TAC

HTB has run several articles on vitamin D deficiencies in previous issues in relation to bone problems, tenofovir and efavirenz.

There is increasing concern and research about vitamin D deficiency in people with HIV, especially with regard to African immigrants and people of African descent living in the cold climates of North America and Europe.

There were several posters on this topic at CROI 2010 and so a themed discussion on it was held, chaired by discussants Peter Reiss of the University of Amsterdam and Michael Yin of Columbia University. Reiss started the session by giving a clear explanation of the basic science of vitamin D. [1-3]

Background

Vitamin D is a group of fat soluble prohormones that mainly originate in the skin where ultraviolet radiation interacts with 7-dehydrocholesterol to form pre-vitamin D3 and then vitamin D3. This process is harder in people with darker skins. Some vitamin D3 is also consumed from diet and supplements. The main purpose of vitamin D is to increase the flow of calcium in the bloodstream.

Vitamin D3 is hydroxylated by the enzyme 25-hydroxylase into hydroxylated vitamin D, 25(OH)D, in the liver.  An alternative pathway to hydroxylated
vitamin D is via vitamin D2 acquired from diet, but this is considered a less important source.

The hydroxylated vitamin D, 25(OH)D is then further hydroxylated in the kidneys to one-alpha-hydroxylated-vitamin D (1a-25(OH)2D) which is the active metabolite. The enzymes involved in this process belong to the cytochrome p450 family, which is a catalyst for some antiretrovirals. There is also speculation that HIV itself affects the production of vitamin D (discussed further below).

Even though 1a-25(OH)2D is the active metabolite, for diagnostic purposes the amount of its precursor, 25(OH)D is  measured. This is because if there is a deficiency in 25(OH)D, an auto-regulatory mechanism upregulates the manufacture of 1a-25(OH)2D. So a person can have sufficient amount of the active metabolite, but still have a deficiency of vitamin D.

Clinical consequences of vitamin D deficiency

Widely accepted criteria for clinically sufficient, insufficient and deficient levels of vitamin D are given in Table 1. However, as Reiss pointed out, by this definition, 40 to 100% of elderly people are deficient in vitamin D and the criteria do not account for ethnic differences. Moreover optimum levels of vitamin D for skeletal and extra-skeletal health have not been established neither in the general population nor for specific ethnic groups.  As is clear from the presentations described in Table 1 below, these criteria are not standardised.

Julian Falutz of McGill University has compiled a table of studies examining vitamin D levels in people with HIV (Table 2). They cover a wide range of countries, seasons, CD4 count ranges and levels of ARV uptake, giving a diverse range of proportions of people categorised as sufficient, insufficient or deficient.

Table 1: Criteria for clinical definitions of 25(OH)D3 in blood (Reiss [3])

European (SI)
measurement (nanomoles/L)
US measurement (nanograms/mL)
Sufficient >=75 nmol/L >=30 ng/mL
Insufficient 0–75 nmol/L 20-30 ng/mL
Deficient <50 nmol/L <20 ng/mL

Table 2: Vitamin D studies in people with HIV (Falutz)

Study N Sex/race Age CD4 ARV (%) Season 25(OH)D Low (%) 25(OH)D Insufficient (%) 25(OH)D Normal (%)
Stephensen (US) 2000 238(+) 121(-) 72%F, 75%B 20 ? ? 86% Spring-Summer ? 87 ?
Seminari (Italy) 2002 68 80%M, all W 41 150 100 Nov-Jun ? 81 ?
Bang (Sweden) 2004 115 M, all white 44 480 62 Autumn-Winter 23 36 40
Rubin (NYC) 2005 62 M, 34% white 48 540 92 Autumn-Winter 42 34 24
Rodriguez (Boston) 2005 57 77% M, 60% W 46 430 81 Winter-Spring 48 ? ?
V. der Ven (Holland) 2006 254 75% M, 73% W 41 420 79 Jan-Aug 29 ? 71
Wetz (London) 2008 47 60% M, 60% B 41 455 88 30% Autumn-Winter 74 17 9
Garcia-Aperico (Spain) 2008 30 100% M and W 38 550 56 Oct-Jun 86 ? ?
Falutz 41 83% M 54 549 100 Autumn 5 55 40

The role of HIV and its treatment in vitamin D regulation is speculative and complex. HIV might affect dietary intake in sick people which in turn might affect levels of vitamin D. HIV might also affect the 1-alpha hydroxylation step and thereby inhibit synthesis of the active metabolite. Vitamin D might also be used by maturing and proliferating T-cells. With their increased production during HIV infection, there might be greater utilisation of vitamin D. The utilisation of cytochrome p450 enzymes by NNRTIs and protease inhibitors might also affect levels of vitamin D.  The hydroxylation step in the kidney takes place in the proximal tubular cells, which are also affected by tenofovir, and this might impact on vitamin D levels. On the other hand ritonavir inhibits 1a-hydroxylase and consequently this might lead to an accumulation of unconverted 25(OH)D in the kidneys.

Vitamin D receptors are found on nearly all cells and deficiency of it is associated with many diseases such as osteomalacia (softening of bones), inflammatory conditions, hypertension, cardiovascular disease, insulin resistance, renal disease, prostate and colon cancer, greater risk of bacterial infection, cognitive dysfunction and frailty.

The SUN study

Christine Dao of the CDC presented results of the SUN study. This study assessed levels of vitamin D (measured by 25(OH)D, as with all other studies presented here) from 2004 to 2006 in the United States in 672 adults with HIV. Insufficiency was defined as less than 30 ng/mL. The study found 72% of participants were vitamin D insufficient. Black race, Hispanic ethnicity, lower ultraviolet exposure, hypertension, lack of exercise and efavirenz exposure were independently associated with insufficiency. On the other hand renal insufficiency (GFR<90) and ritonavir exposure were independently associated with lower odds of insufficiency. In question time, Dao stated that 9% of participants were deficient, defined in this study as a 25(OH)D less than 10 ng/mL (which is different from the definition of deficiency given above). [4]

Italian cohort

Antonella d’ Arminio Monforte from the University of Milan presented the results of an observational cohort with retrospective analysis in vitamin D in stored plasma samples of 852 patients contributing 1,498 measurements. Of these, 262 measurements were taken before and 1,236 after ART initiation. Insufficiency was defined the same way as the European measurement in Table 1, but deficiency was defined as less than 30 nmol/L. [5]

Insufficiency was found in 804 measurements (54%), while deficiency was found in 98 (7%). In 116 patients measured pre- and post-ART initiation in the same season, there was a non-significant drop of vitamin D levels (average of 7.57 nmol/L per year; p=0.11).

The following were significantly associated with deficiency versus normal values (adjusted odds ratios):

  • • Age (per 10 years older) (OR 1.53; 95%CI 1.11–2.09;  p=0.009)
  • Non-Caucasian origin  (OR: Caucasians were 0.17 times as likely to have deficiency; 95%CI 0.07–0.42; p=0.0001)
  • Lower CD4 count (per 100 cells/mm3) (OR: Higher CD4 count was 0.9 times as likely to have deficiency; 95%CI 0.82–0.99; p=0.04)
  • Lower BMI (OR: for each unit higher, 0.9 times as likely to have deficiency; 95%CI 0.83–0.98; p=0.01)
  • NNRTI vs PI use (OR: participants on PI regimens were 0.47 times as likely to have deficiency; 95%CI 0.27–0.84; p=0.01)
  • Season:  (with summer as reference: OR of autumn: 1.24; 95%CI  0.51–3.05; p=0.64; winter: 4.84; 95%CI 2.07–11.33; p=0.0003; spring: 8.3; 95%CI 3.61–19.09; p=0.0001)

During questions, d’Arminio Monforte stated that they had found that deficiency was associated with clinical events, in particular cardiovascular ones, but the direction of any causal effect, if any, was unclear. She also pointed out that in the HIV-negative population obesity is associated with deficiency, while in this cohort the opposite occurred: lower BMI was associated with deficiency.

Swiss cohort

Christoph Fux of University Hospital, Bern presented data on vitamin D deficiency in 211 patients in the Swiss HIV cohort, half of whom were measured in spring and half in autumn. As with the Italian cohort, insufficiency was defined the same way as the European measurement in Table 1, but deficiency was defined as less than 30 nmol/L. [6]

At baseline, before ART initiation, there was 14% deficiency in autumn and 42% deficiency in spring. After 12 months of ART – at which point all patients were virologically suppressed – this was virtually unchanged (47% in spring, NS). White race was associated with significantly higher vitamin D levels than Asian, Hispanic and black race.

Interestingly, measurements of 1a-25(OH)2D were also taken and it was found that there was some compensation, ie when 25(OH)D levels were lower, there was a higher ratio of the active metabolite to 25(OH)D.

In multivariate analysis, white race (14.1 umol/L higher; p=0.001) and, surprisingly, duration of HIV by 10 years (6.4; p=0.02) were associated with higher 25(OH)D levels. While BMI (-0.7; p=0.05), active IDU (-11.2; p=0.02), spring (-17.7; p<0.001) and NNRTI use (-8.2; p=0.002) were associated with lower levels. Sex, age, HCV positivity, cGFR <60mL/min, previous AIDS, CD4 count and tenofovir use were not significantly related to lower levels.

Interestingly, for 1a-25(OH)2D levels, the results were different. Neither race nor season were significant. BMI was positively associated with vitamin D levels (1.7; p<0.001), as was tenofovir use (7.8; p=0.02).  HCV positivity was negatively associated  (-9.1; p=0.04) as was previous AIDS (-11.6; p=0.007) and CD4 count by 100 cells (-2.6; p=0.003).

Tanzanian cohort

Saurabh Mehta of Harvard Medical School presented data from Tanzania on the association between vitamin D levels and wasting, acute respiratory infections and thrush. They defined low vitamin D level as less than 32 ng/mL. Vitamin D levels were measured in 884 pregnant Tanzanian women who were followed up for a median of 70 months.

In January, this research group published an article in PloS One showing that low vitamin D levels are associated with increased HIV disease progression (RR 1.25; 95%CI 1.05–1.5)
and anemia (RR 1.46; 95%CI 1.09–1.96). Women in the highest vitamin D quartile had a 42% lower risk of all-cause mortality (RR 0.58; 95%CI 0.4–0.84). This group has also previously published a widely cited study showing that a vitamin supplement delayed disease progression and mortality in this cohort, but the supplement did not contain vitamin D  [7-9].

In this study, low vitamin D was associated with a 45% higher risk of wasting (BMI <18kg/m2; p=0.03), a higher incidence of acute respiratory infections (RR 1.28; 95%CI 1.05–1.55) and a much higher incidence of thrush (RR 2.92; 95%CI 1.43–5.96). They also found a linear relationship between any vitamin D level and wasting.

During questions, Mehta pointed out that no association was found with seasonal factors (Tanzania is near the equator). He also said that they found no association between vitamin D and TB, but did find an association between children born to mothers with deficiency and TB. When asked to comment on which way the association between wasting and vitamin D went, Mehta explained that the vitamin D level was measured at baseline when women with wasting were excluded from analysis and that the wasting in this cohort came subsequent to the vitamin D measure.

WIHS cohort

Audrey French of Rush University Medical Centre presented data from a cross-sectional sub-study of the Womens’ Interagency HIV Study (WIHS), whose objective was to see
if there was an association between vitamin D deficiency and bacterial vaginosis. WIHS is a longitudinal multi-site study of about 3,000 women with and without HIV. The substudy is from Chicago and New York City and includes 480 HIV-positive and 122 HIV-negative participants.

Bacterial vaginosis was diagnosed using the Amsel criteria. Vitamin D insufficiency was defined as 20-30ng/mL and deficiency as less than 20ng/mL. Prevalence of deficiency was 60% and insufficiency was 24%. Black race was the only predictor of deficiency in an analysis using demographics, socioeconomic status and HIV associated variables including HIV status. Factors associated with bacterial vaginosis in multivariate analysis were black race (OR 6.08; 95%CI 2.66–13.9), number of recent sexual partners (OR 2.3; 95%CI 1.12–5.06) and vitamin D deficiency (OR 2.3; 95%CI 1.02–5.19). The correlation co-efficient between vitamin D and bacterial vaginosis was -0.14 (p<0.001).

During question time, it was stated that vitamin D status was not associated with bone mineral density. Two researchers indicated that in their US cohorts of HIV-positive and HIV-negative people, they had not found an association between HIV status and vitamin D status. But another researcher indicated that a Swiss study had found a difference.

The need for a clinical trial

Michael Yin summarised the session, emphasising the many unanswered questions, lack of data and need for clinical trials of vitamin D. Study participants to consider include people initiating ART especially efavirenz, people who are ageing and people in resource limited high TB prevalence areas. Study endpoints to consider are bone density, muscle mass, fall risk, insulin resistance, cardiovascular disease, CD4 count, HIV progression, opportunistic infections and other measures of innate and adaptive immunity.
He suggested a vitamin D supplement dose of 1000–-2000 IU per day was reasonable. [10]

He also described unanswered questions about screening. He asked if there should be universal screening (adopted by European AIDS Clinical Society) or targeted screening aimed at older people, black race people, people with previous fractures or low bone mass density, people who are frail or have sarcopenia and patients on efavirenz. He suggested that a target in patients of 40–60 ng/mL or 100–150 nmol/L should be aimed for.

During questions, Yin was asked about the risk of high dosages. He described a study that looked at vitamin D and its correlation with calcium levels. Hypercalcaemia was only seen at levels of 200-240 nmol/L, which was far higher than could be reached with the doses he was proposing. Another questioner asked whether clinical or surrogate end point markers should be the endpoint of a vitamin D trial. Reiss responded that a trial looking at clinical
endpoints would have to be too large and consequently surrogate endpoints would have to be used.

comment

These studies contribute to our understanding of vitamin D deficiency in people with HIV. However, there remain many unanswered questions relating to the clinical implications of vitamin D deficiency, how and what to measure and appropriate target levels in different populations, if supplementation is
indicated.

In the absence of data from clinical trials, most HIV guidelines defer to national protocols for management of bone disease, recommending supplementation for patients with deficient levels.

While a Cochrane review found statistically significant evidence for prescribing vitamin D to patients taking systemic corticosteroids, other reviews found insufficient evidence to show supplementation prevents fractures in older people, or during pregnancy or to treat chronic kidney diseases or
children with cystic fibrosis.

Peter Reiss noted that the size and cost of an adequately powered randomised trial probably makes this unlikely.  Management should therefore also include lifestyle changes, such as greater exposure to sun and improved diet and that this may be sufficient for some patients.

References

Unless stated otherwise, all references are to the Programme and Abstracts of the 17th Conference on Retroviruses and Opportunistic Infections. 16-10
February 2010, San Francisco. All oral abstracts are available as webcasts.
http://www.retroconference.org

  1. Reduced levels of vitamin D in patients taking efavirenz. HTB, November/December 2009.
    http://i-base.info/htb/6127
  2. Vitamin D deficiency, supplementation and tenofovir. HTB, May/June 2009.
    http://i-base.info/htb/1688
  3. Got Milk? Vitamin D deficiency prevalence and associations. CROI 2010. Webcast session Feb 17 2010.
  4. Dao C et al. Assessment of vitamin D levels among HIV-infected persons in the study to understand the natural history of HIV/AIDS in the era of effective therapy (SUN study). 17th CROI, 2010. Poster abstract 750.
    http://www.retroconference.org/2010/Abstracts/36819.htm
  5. Borderi M et al. Prevalence of hypovitaminosis D among HIV+ patients enrolled in a large Italian cohort. 17th CROI, 2010. Poster 751.
    http://www.retroconference.org/2010/Abstracts/39276.htm
  6. Mueller N et al. High Prevalence of severe vitamin D deficiency in cART naive and successfully treated Swiss HIV patients. 17th CROI, 2010. Poster
    http://www.retroconference.org/2010/Abstracts/38991.htm
  7. Mehta S et al. Vitamin D and HIV-related complications and HIV disease progression in women in Tanzania. 17th CROI, 2010. Poster 753.
    http://www.retroconference.org/2010/Abstracts/39115.htm
  8. Mehta S et al. Vitamin D status of HIV-infected women and its association with HIV disease progression, anemia, and mortality. PLoS One 2010 Jan 19;5(1).
    http://www.ncbi.nlm.nih.gov/pubmed/20098738
  9. Fawzi WW et al. A randomised trial of multivitamin supplements and HIV disease progression and mortality. N Engl J Med. 2004 Jul 1;351(1):23-32.
  10. French A et al.  Vitamin D deficiency and bacterial vaginosis among HIV-infected and -uninfected women in the United States. 17th CROI, 2010. Poster 754.
    http://www.retroconference.org/2010/Abstracts/37539.htm

Links to other websites are current at date of posting but not maintained.