Neeti Agarwal

Human adipose tissue as a reservoir for memory CD4+ T cells and HIV

Objective:The objective of this study is to determine whether adipose tissue functions as a reservoir for HIV-1. Design:We examined memory CD4+ T cells and HIV DNA in adipose tissue–stromal vascular fraction (AT-SVF) of five patients [four antiretroviral therapy (ART)-treated and one untreated]. To determine whether adipocytes stimulate CD4+ T cells and regulate HIV production, primary human adipose cells were cocultured with HIV-infected CD4+ T cells. Methods:AT-SVF T cells were studied by flow cytometry, and AT-SVF HIV DNA (Gag and Env) was examined by nested PCR and sequence analyses. CD4+ T-cell activation and HIV production were measured by flow cytometry and ELISA. Results:AT-SVF CD3+ T cells were activated (>60% CD69+) memory CD4+ and CD8+ T cells in uninfected and HIV-infected persons, but the AT-SVF CD4+/CD8+ ratio was lower in HIV patients. HIV DNA (Gag and Env) was detected in AT-SVF of all five patients examined by nested PCR, comparably to other tissues [peripheral blood mononuclear cell (PBMC), lymph node or thymus]. In coculture experiments, adipocytes increased CD4+ T-cell activation and HIV production approximately two to three-fold in synergy with gamma-chain cytokines interleukin (IL)-2, IL7 or IL15. These effects were mitigated by neutralizing antibodies against IL6 and integrin-&agr;1&bgr;1. Adipocytes also enhanced T-cell viability. Conclusion:Adipose tissues of ART-treated patients harbour activated memory CD4+ T cells and HIV DNA. Adipocytes promote CD4+ T-cell activation and HIV production in concert with intrinsic adipose factors. Adipose tissue may be an important reservoir for HIV.

Neurogenesis in colorectal cancer is a marker of aggressive tumor behavior and poor outcomes

Colorectal cancer staging criteria do not rely on examination of neuronal tissue. The authors previously demonstrated that perineural invasion is an independent prognostic factor of outcomes in colorectal cancer. For the current study, they hypothesized that neurogenesis occurs in colorectal cancer and portends an aggressive tumor phenotype.

HIV-1 Vpr Induces Adipose Dysfunction in Vivo Through Reciprocal Effects on PPAR/GR Co-Regulation

HIV-1 Vpr induces the cardinal metabolic defects of HIV-associated lipodystrophy and hepatosteatosis in vivo. Chewing the Fat with HIV Protein HIV infection is infamously known for its devastating immunosuppressive effects; however, immunosuppression is not the whole story. Patients whose viral load is well controlled with antiretroviral therapy (ART) are still at risk for a variety of chronic metabolic complications, including adipose dysfunction. ART drugs have been implicated in some of these chronic complications, but others, such as decreased body fat and altered fat distribution, occur in even untreated patients. Now, Agarwal et al. demonstrate that, at least in mice, the HIV protein viral protein R (Vpr) may directly contribute to adipose dysfunction. The authors began with the observation that Vpr circulates in the blood of HIV-infected patients on ART, even those with no detectable viral load. Paired with the knowledge that Vpr can coactivate the glucocorticoid receptor (GR) and co-repress peroxisome proliferator–activated receptor γ (PPARγ), both of which are involved in metabolic regulation, they hypothesized the Vpr itself may play a pathogenic role in adipose dysfunction in these individuals. They took their studies into two mouse models of Vpr expression that lacked HIV infection: transgenic and pharmacologic. Vpr alone could disrupt PPAR/GR co-regulation and cell cycle control in adipose depots and liver to produce adipose dysfunction and hepatosteatosis. If these mechanisms hold true in humans, they could lead to targeted treatment of these metabolic complications with Vpr inhibitors, GR antagonists, or PPARγ/PPARα agonists. Viral infections, such as HIV, have been linked to obesity, but mechanistic evidence that they cause adipose dysfunction in vivo is lacking. We investigated a pathogenic role for the HIV-1 accessory protein viral protein R (Vpr), which can coactivate the glucocorticoid receptor (GR) and co-repress peroxisome proliferator–activated receptor γ (PPARγ) in vitro, in HIV-associated adipose dysfunction. Vpr circulated in the blood of most HIV-infected patients tested, including those on antiretroviral therapy (ART) with undetectable viral load. Vpr-mediated mechanisms were dissected in vivo using mouse models expressing the Vpr transgene in adipose tissues and liver (Vpr-Tg) or infused with synthetic Vpr. Both models demonstrated accelerated whole-body lipolysis, hyperglycemia and hypertriglyceridemia, and tissue-specific findings. Fat depots in these mice had diminished mass, macrophage infiltration, and blunted PPARγ target gene expression but increased GR target gene expression. In liver, we observed blunted PPARα target gene expression, steatosis with decreased adenosine monophosphate–activated protein kinase activity, and insulin resistance. Similar to human HIV-infected patients, Vpr circulated in the serum of Vpr-Tg mice. Vpr blocked differentiation in preadipocytes through cell cycle arrest, whereas in mature adipocytes, it increased lipolysis with reciprocally altered association of PPARγ and GR with their target promoters. These results delineate a distinct pathogenic sequence: Vpr, released from HIV-1 in tissue reservoirs after ART, can disrupt PPAR/GR co-regulation and cell cycle control to produce adipose dysfunction and hepatosteatosis. Confirmation of these mechanisms in HIV patients could lead to targeted treatment of the metabolic complications with Vpr inhibitors, GR antagonists, or PPARγ/PPARα agonists.

HIV-1 viral protein R (Vpr) induces fatty liver in mice via LXRα and PPARα dysregulation: implications for HIV-specific pathogenesis of NAFLD

HIV patients develop hepatic steatosis. We investigated hepatic steatosis in transgenic mice expressing the HIV-1 accessory protein Vpr (Vpr-Tg) in liver and adipose tissues, and WT mice infused with synthetic Vpr. Vpr-Tg mice developed increased liver triglyceride content and elevated ALT, bilirubin and alkaline phosphatase due to three hepatic defects: 1.6-fold accelerated de novo lipogenesis (DNL), 45% slower fatty acid ß-oxidation, and 40% decreased VLDL-triglyceride export. Accelerated hepatic DNL was due to coactivation by Vpr of liver X receptor-α (LXRα) with increased expression of its lipogenic targets Srebp1c, Chrebp, Lpk, Dgat, Fasn and Scd1, and intranuclear SREBP1c and ChREBP. Vpr enhanced association of LXRα with Lxrα and Srebp1c promoters, increased LXRE-LXRα binding, and broadly altered hepatic expression of LXRα-regulated lipid metabolic genes. Diminished hepatic fatty acid ß-oxidation was associated with decreased mRNA expression of Pparα and its targets Cpt1, Aox, Lcad, Ehhadh, Hsd10 and Acaa2, and blunted VLDL export with decreased expression of Mttp and its product microsomal triglyceride transfer protein. With our previous findings that Vpr circulates in HIV patients (including those with undetectable plasma HIV-1 RNA), co-regulates the glucocorticoid receptor and PPARγ and transduces hepatocytes, these data indicate a potential role for Vpr in HIV-associated fatty liver disease.

Adipocytes impair efficacy of antiretroviral therapy

ABSTRACT Adequate distribution of antiretroviral drugs to infected cells in HIV patients is critical for viral suppression. In humans and primates, HIV‐ and SIV‐infected CD4 T cells in adipose tissues have recently been identified as reservoirs for infectious virus. To better characterize adipose tissue as a pharmacological sanctuary for HIV‐infected cells, in vitro experiments were conducted to assess antiretroviral drug efficacy in the presence of adipocytes, and drug penetration in adipose tissue cells (stromal‐vascular‐fraction cells and mature adipocytes) was examined in treated humans and monkeys. Co‐culture experiments between HIV‐1‐infected CD4 T cells and primary human adipocytes showed that adipocytes consistently reduced the antiviral efficacy of the nucleotide reverse transcriptase inhibitor tenofovir and its prodrug forms tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF). In HIV‐infected persons, LC‐MS/MS analysis of intracellular lysates derived from adipose tissue stromal‐vascular‐fraction cells or mature adipocytes suggested that integrase inhibitors penetrate adipose tissue, whereas penetration of nucleoside/nucleotide reverse transcriptase inhibitors such as TDF, emtricitabine, abacavir, and lamivudine is restricted. The limited distribution and functions of key antiretroviral drugs within fat depots may contribute to viral persistence in adipose tissue. HIGHLIGHTSHuman adipocytes increase CD4 T cell activation and HIV replication.Human adipocytes sequester substantial amounts of antiretroviral drugs.Integrase inhibitors penetrate adipose tissue of HIV patients.