Selective capacity of metreleptin administration to reconstitute CD4+ T-cell number in females with acquired hypoleptinemia

Abstract

Leptin is an adipocyte-derived hormone that controls food intake and reproductive and immune functions in rodents. In uncontrolled human studies, low leptin levels are associated with impaired immune responses and reduced T-cell counts; however, the effects of leptin replacement on the adaptive immune system have not yet been reported in the context of randomized, controlled studies and/or in conditions of chronic acquired leptin deficiency. To address these questions, we performed a randomized, double-blinded, placebo-controlled trial of recombinant methionyl-human leptin (metreleptin) administration in replacement doses in women experiencing the female triad (hypothalamic amenorrhea) with acquired chronic hypoleptinemia induced by negative energy balance. Metreleptin restored both CD4(+) T-cell counts and their in vitro proliferative responses in these women. These changes were accompanied by a transcriptional signature in which genes relevant to cell survival and hormonal response were up-regulated, and apoptosis genes were down-regulated in circulating immune cells. We also observed that signaling pathways involved in cell growth/survival/proliferation, such as the STAT3, AMPK, mTOR, ERK1/2, and Akt pathways, were activated directly by acute in vivo metreleptin administration in peripheral blood mononuclear cells and CD4(+) T-cells both from subjects with chronic hypoleptinemia and from normoleptinemic, lean female subjects. Our data show that metreleptin administration, in doses that normalize circulating leptin levels, induces transcriptional changes, activates intracellular signaling pathways, and restores CD4(+) T-cell counts. Thus, metreleptin may prove to be a safe and effective therapy for selective CD4(+) T-cell immune reconstitution in hypoleptinemic states such as tuberculosis and HIV infection in which CD4(+) T cells are reduced.

Trial registration: ClinicalTrials.gov NCT00130117 NCT01275053.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Effects of metreleptin on immune phenotype. Administration of metreleptin for 36 wk in replacement doses induced a significant increase in terms of Δ change in the number of cells over time [calculated as the absolute number of cells/mm3 at week of treatment minus the number of cells/mm3 at baseline (time 0)] in total lymphocytes and CD3+, CD4+, CD4+CD45RA+ naive, and CD4+CD45RO+ memory cells. *P < 0.05 in A, B, and D–F. No significant effect was observed on CD8+ (C), B (G), and NK cells (H) respectively.

Fig. 2.

Effects of metreleptin on PBMC proliferation. After 36 wk of metreleptin administration in replacement doses, the proliferative response to T-cell–specific OKT3 (polyclonal) (A) and PPD (antigen-specific) (D) stimulation was increased significantly in metreleptin-treated patients vs. placebo-treated patients in terms of Δ change in proliferation over time [calculated as the cpm at week of treatment minus the number cpm at baseline (time 0)]. *P < 0.05. This effect was not observed during strong unspecific stimulations such as PHA (B) and PMA/Iono (C).

Fig. 3.

Transcriptional signature induced by metreleptin in PBMCs from HA subjects. Diagram of gene-expression profile at weeks 12, 24, and 36 of treatment with metreleptin vs. baseline. The total number of genes analyzed was 17,131. There were more differentially expressed genes at week 12 (308) than at week 24 (22) or week 36 (74) of treatment. L12 -24-36, Leptin treatment week 12, 24, and 36 respectively; BL0, base line week 0.

Fig. 4.

Acute in vivo metreleptin-induced signaling in PBMCs and in vitro in CD4+ T cells from lean, normoleptinemic subjects. (A–F) Ex vivo Western blotting analyses of PBMCs from lean females upon in vivo metreleptin stimulation. (G–L) The same analyses were performed on isolated, highly purified CD4+ T cells stimulated in vitro with metreleptin for 1 h. Similar results were obtained with PBMCs in vivo and isolated CD4+ T cells in vitro. All data were analyzed using the Student t test. Values are means ± SD; n = 3.

Fig. P1.

Metreleptin treatment for 36 wk selectively restores CD4+ T-cell number and function in hypoleptinemic women with HA. These results were supported at the biochemical and transcriptional levels by the specific up-regulation of survival genes and down-regulation of genes involved in cell death.