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Obesity Doubles Chances of More Inflammation
and Monocyte Activation With HIV
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20th International AIDS Conference, July 20-25, 2014, Melbourne
Mark Mascolini
Obesity affected 21% of HIV-positive people in a multisite US cohort and doubled chances of higher markers of inflammation and immune activation [1]. Insulin resistance had only a slight impact on these associations.
Research links obesity to higher levels of inflammatory markers in the general population, noted the SUN Study investigators who conducted this analysis. And nearly 25% of HIV-positive people in the United States were obese in a 2013 nationwide CDC analysis [2]. Lofty levels of inflammation and immune activation may contribute to premature cardiovascular disease, other illnesses, and mortality in people with HIV. But little is known about whether obesity has ties to inflammation and immune activation in HIV-positive people.
Sponsored by the CDC, the SUN Study had multiple sites in 5 states. To assess the impact of obesity on inflammation and activation markers, SUN Study investigators focused on 452 antiretroviral-treated people with a viral load below 50 copies. They measured IL-6 (an inflammation marker) and sCD14 and sCD163 (monocyte-activation markers) at a baseline visit. The researchers also determined two monocyte immunophenotypes: CD14+/CD16+ and CD14dim/CD16+ (activation markers).
The investigators divided results into tertiles (highest, middle, and lowest one third) and used logistic regression analysis to identify factors predicting values in the highest tertile. They also measured insulin resistance (by HOMA-IR) and leptin (which helps control how much fat the body stores).
Three quarters of study participants (78%) were men, and median age stood at 41 years (interquartile range [IQR] 36 to 48); 62% of participants were white, 26% black, and 9% Hispanic. Median current CD4 count stood at 475 (IQR 308 to 697), 11% of participants had diabetes, 33% had hypertension, 13% were taking a lipid-lowering drugs, and 42% currently smoked. While 43% of cohort members had a normal body mass index, 36% were overweight and 21% obese.
Compared with normal-weight and overweight people, obese participants had significantly higher levels of sCD163 (P = 0.040), CD14+/CD16+ (P = 0.003), and CD14dim/CD16+ (P = 0.010), with trends toward higher levels of IL-6 (P = 0.053).
Univariate analysis linked obesity to elevated (highest tertile versus lower two tertiles) IL-6 (odds ratio [OR] 1.82, P = 0.017), sCD163 (OR 2.05, P = 0.005), CD14+/CD16+ (OR 1.87, P = 0.008), and CD14dim/CD16+ (OR 2.06, P = 0.002). In the same analysis, every unit higher HOMA-IR was associated with elevated IL-6, sCD163, CD14+/CD16+, and CD14dim/CD16+. Hypertension was associated with higher IL-6 and sCD163 but not with the other markers.
Logistic regression analysis adjusted for age, gender, race/ethnicity, smoking, hypertension, and CD4 count determined that obesity independently raised odds of higher IL-6 (OR 1.96, 95% confidence interval [CI] 1.11 to 3.47), sCD163 (OR 1.94, 95% CI 1.12 to 3.37), CD14+/CD16+ (OR 1.78, 95% CI 1.05 to 3.00), and CD14dim/CD16+. Further adjustment for HOMA-IR modestly attenuated these associations. Additional adjustment for leptin had no impact.
Sun Study investigators concluded that obesity is prevalent in this middle-aged HIV group with antiretroviral-induced viral suppression. And obesity was associated with greater systemic inflammation and monocyte activation. They proposed that "the potential contribution of obesity (ie, adipose tissue) to persistent inflammation in treated HIV disease warrants further study."
References
1. Baker J, Conley L, Bush T, et al. Obesity is associated with greater inflammation and monocyte activation among persons with effectively treated HIV infection in the SUN study. 20th International AIDS Conference. July 20-25, 2014. Melbourne. Abstract THPE051.
2. Thompson-Paul A, Wei S, Mattson C, Skarbinski J. Prevalence of obesity in a nationally representative sample of HIV+ adults receiving medical care in the US: Medical Monitoring Project, 2009. 20th Conference on Retroviruses and Opportunistic Infections. March 3-6, 2013. Atlanta. Abstract 777. http://www.natap.org/2013/CROI/croi_76.htm
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