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Obesity Linked to Inflammation, cIMT, Low Vitamin D in US HIV Group
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XIX International AIDS Conference, July 22-27, 2012, Washington, DC
Mark Mascolini
Obese people in the ongoing US SUN Study had significantly higher levels of inflammatory markers, significantly greater carotid artery intima-media thickness (cIMT), and significantly lower vitamin D levels than normal-weight people, although everyone in the analysis had a viral load below 400 copies [1]. In overweight cohort members, vitamin D levels dropped significantly over 2 years of follow-up.
Obesity affects a growing proportion of the US population, including people with HIV. But associations between obesity and markers of inflammation in HIV-positive people responding to antiretroviral therapy had not been addressed until this analysis in the Study to Understand the Natural History of HIV/AIDS in the Era of Effective Therapy--the SUN Study. Researchers also examined associations between obesity and cIMT, an atherosclerosis marker, and vitamin D.
The SUN Study prospectively tracks 700 HIV-positive adults seen at seven HIV clinics in 4 US cities. This analysis focused on 494 SUN participants with a viral load below 400 copies who were obese (body mass index [BMI] at or above 30 kg/m2), overweight (BMI 25 to 29.9 kg/m2), normal weight (BMI 18.5 to 24.9 kg/m2), or underweight (BMI below 18.5 kg/m2) at their baseline visit. At that visit, 23% of study participants were obese, 38% overweight, 38% normal weight, and 2% underweight.
Median age was 41 at the baseline visit, and 22% of cohort members were women; 61% were white, 27% black, and 10% Hispanic. Only 12% had ever injected drugs, but 41% were current smokers and 66% ever smokers.
At the baseline visit, factors associated with a higher BMI category in univariate analysis were female gender, black race, and higher total cholesterol, apolipoprotein E (ApoE), insulin, HOMA-determined insulin resistance, leptin, interleukin 6, high-sensitivity C-reactive protein (hsCRP), TNF-alpha, D-dimer, and cIMT. Current and ever smoking and higher vitamin D were associated with lower BMI.
Median cIMT was 0.74 mm (interquartile range [IQR] 0.65 to 0.82) in obese people, 0.73 mm (IQR 0.65 to 0.82) in overweight people, and 0.70 mm (IQR 0.64 to 0.78) in normal-weight people (P = 0.048). Vitamin D levels were significantly lower in obese people (median 19.9 ng/mL, IQR 13.2 to 27.1) than in overweight people (median 24.4 ng/mL, IQR 18.0 to 31.7) and normal-weight people (median 24.2 ng/mL, IQR 17.7 to 34.7) (P < 0.001).
Follow-up analysis 2 years later showed that 16% of 351 participants had changed their BMI category. Of those 16%, 33% went from normal weight to overweight, 25% went from overweight to obese, and 2% went from normal weight to obese. Overall, 10% of participants followed for 2 years moved to a higher BMI category.
Among 256 SUN participants who had inflammatory markers measured at the 2-year follow-up point, no marker levels changed significantly, but vitamin D levels dropped significantly among overweight people (P = 0.045).
"In this contemporary virologically suppressed HIV cohort," the researchers concluded, "obese participants exhibited higher levels of markers of inflammation and atherosclerosis as well as lower vitamin D levels, despite a similar degree of immunosuppression compared with normal weight participants."
Reference
1. Conley L, Bush T, Patel P, et al. Obese HIV-positive persons have higher levels of select inflammatory markers and co-morbid illnesses. XIX International AIDS Conference. July 22-27, 2012. Washington, DC. Abstract WEPE096.
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