The HIV, Adipose Tissue Immunology, and Metabolism Study

Overview

With the introduction of effective anti-retroviral therapy (ART), HIV-infected persons can now survive for decades, but this success has been accompanied by an increased risk of developing metabolic disease and diabetes in HIV-infected persons compared to the general population. Recent studies from HIV-negative subjects have identified several associations between circulating immune cell populations and impaired glucose tolerance, including increased activated CD4+ and CD8+ T cells, and reduced regulatory T cells. Of note, these same changes in peripheral T cell subsets are frequently observed in patients with chronic HIV infection. The goal of this study is to assess whether the circulating T cell distribution is reflective of the adipose tissue T cell distribution, and to understand whether chronic adipose tissue T cell activation may impair adipocyte (i.e., fat cell) function and insulin sensitivity. If the investigators' hypotheses are correct, this will demonstrate that chronic peripheral immune activation (i.e., high memory T cells, low naïve cells, and increased expression of activation surface markers) is associated with greater adipose-resident CD4+ and CD8+ T cell expression of activation markers, adipose tissue inflammation, and insulin resistance.

With the introduction of effective antiretroviral therapy (ART), HIV-infected persons can now survive for decades, but this success has been accompanied by an increased risk of developing metabolic disease compared HIV-negative persons. In the Multicenter AIDS Cohort Study, HIV-infected men had a greater than 4-fold increased incidence of a new diabetes diagnosis compared to HIV-negative men after adjusting for age and body mass index (BMI). Prevalence studies of diabetes in HIV-infected individuals on ART have reported incidence rates of 3.1 to 14 per 1000 patient-years. Furthermore, treated HIV infection appears to act synergistically with other risk factors, and diabetes prevalence is especially high among HIV-infected individuals with high BMI and advanced age. Recent studies from HIV-negative subjects identified several associations between adaptive immune cell populations and impaired glucose tolerance. Peripheral T regulatory (Treg) cells are significantly lower in patients with type-2 diabetes , while the numbers activated T cells, CD4+ TH1 (pro-inflammatory) cells, and memory CD4+ T cells are higher in diabetics. Immune cells translocate from the circulation into adipose tissue in a dynamic process, and T cells are present in the stromal fraction of adipose tissue and affect adipocyte function. The striking increase in adipose tissue CD4+ TH1 cells and CD8+ T cells, and a decrease in Treg cells, observed in obesity may have an important role in the development of insulin resistance. Secretion of the proinflammatory cytokines interferon-γ and interleukin (IL)-17 by TH1 and TH17 cells are implicated in the induction of proinflammatory M1 macrophages, which express IL-6 and tumor necrosis factor alpha, and inhibit adipocyte insulin signaling by promoting phosphorylation of insulin receptor substrate 1. The investigators hypothesize that the chronic, HIV-related activation of circulating CD4+ and CD8+ T cells may be accompanied by the accumulation of activated T cells in adipose tissue with adverse effects on metabolic activity. In this study, the investigators will test the hypothesis that the oligoclonal expansion of chronically activated peripheral T cells in adipose tissue is a primary driver of macrophage inflammation and reduced adipocyte insulin sensitivity. Furthermore, the investigators propose that this represents a central mechanistic linkage underlying the association between circulating T cell activation and incident diabetes risk observed in HIV-infected and HIV-negative individuals.