The mechanistic target of rapamycin (mTOR) promotes HIV transcription. In line, we demonstrated that HIV preferentially targets gut-homing CCR6+Th17 cells for replication/persistence via mTOR-dependent mechanisms. Thus, mTOR inhibitors may limit residual HIV transcription during ART and subsequently reduce immune activation/inflammation. Here, we report results from a clinical trial conceived to evaluate the effect of 12 weeks of metformin (mTOR inhibitor) therapy on the size of HIV reservoirs (primary objective) and immune activation (secondary objective) in ART-treated HIV-infected adults (HIV+ART).
Metformin (850 mg bid) was administered orally for 12 weeks in n=22 HIV+ART. Participants were non-diabetic, on ART for >3 years, with <40 HIV-RNA copies/ml plasma for >3 months, and CD4/CD8 ratios ≤0.7. Blood was collected at baseline (Visit 1), after 12 weeks of metformin (Visit 2), and 12 weeks after metformin discontinuation (Visit 3). Sigmoid colon biopsies (≈32 biopsies/participant) were collected at Visits 1-2 from n=13 participants. HIV-DNA was quantified by real-time nested PCR. Replication-competent HIV was quantified by viral outgrowth assay (VOA). Matched blood/colon memory CD4+ T-cells were analyzed for surface/intracellular molecule expression and simultaneously sorted by flow cytometry (BD AriaIII). Plasma soluble factors were quantified using R&D Systems Multiplex Assay and ELISA.
Metformin was well tolerated. Total HIV-DNA levels in blood/colon CD4+ T-cells and the frequency of blood CD4+ T-cells carrying replication-competent HIV was stable between Visits 1-3. However, investigations on matched blood/colon samples revealed a positive effect of metformin as reflected by i) decreased infiltration of CD4+ T-cells in the colon (median: 7.3% vs. 4.7%, Visit 1 vs. 2; p=0.019), indicative of reduced colon inflammation; ii) decreased mTOR phosphorylation in colon CCR6+CD4+ T-cells (median: 13.0% vs. 7.9%, Visit 1 vs. 2; p=0.0087); iii) a tendency for decreased expression of the HIV co-receptors CCR5 and integrin β7, and increased expression of the HIV restriction factor SAMHD1 in colon CCR6+CD4+ T-cells; and iv) decreased sCD14 plasma levels (mean: 1,893 vs. 1,519 ng/ml; Visit 1 vs. 3; p=0.02).
This pilot study reveals metformin-mediated benefits in controlling inflammation, in part via mTOR regulation, and prompts us to further investigate the immunological/virological benefits of long-term metformin supplementation in HIV+ART individuals.