ODP010 Relaxin Receptor RXFP1 Knockout in Adipose Tissue Progenitor Cells Results in Resistance to High Fat Diet-Induced Weigh Gain

Abstract Relaxin is a polypeptide hormone that signals through its cognate receptor RXFP1. Previous work demonstrated that global RXFP1-knockout mice developed age-related adipose tissue fibrosis and dysfunction. Our preliminary data suggested that adipose tissue progenitor cells (APC) express RXFP1 in the white adipose tissue in mice. To determine the role of APC in relaxin signaling, we crossed floxed RXFP1 mice (RXFP1-fl/fl) with mice expressing tamoxifen-inducible CRE recombinase under control of the platelet-derived growth factor receptor-β (PDGFRβ) promoter to produce conditional RXFP1 knockout in adipose tissue progenitor cells and fibroblasts (RXFP1-PKO). After tamoxifen treatment, both RXFP1-fl/fl and RXFP1-PKO mice were placed on a high fat diet (58% calories from fat) supplemented with sucrose and fructose in the drinking water, or chow diet for 16 weeks. At the end of the study, body mass composition was measured using an Echo-MRI instrument. Adipose tissue fibrosis was assessed histologically by Sirius red staining. In response to the HFD, the control (fl/fl) mice reached an average weight of 48.3 ± 0.6g, while the RXFP1-PKO mice were resistant to weight gain, reaching only 40.3 ±3g (p<. 05). The body mass composition changed in the RXFP1-fl/fl mice on HFD (34. 0% fat/55.2% lean) compared to chow (14.7% fat/68.9% lean). The RXFP1-PKO mice had a significantly lower gain in fat mass on HFD (29.7% fat/59.1% lean on HFD; 12.6% fat/71. 0% lean on chow) compared to the RXFP-fl/fl mice. Histological analysis of the inguinal white adipose tissue (iWAT) revealed that while RXFP1-fl/fl mice developed adipocyte hypertrophy in response to the HFD, the RXFP1-PKO mice had smaller adipocyte size. This was accompanied by increased pericellular and perivascular fibrosis in the iWAT as determined by Sirius red staining. To determine if differentiation of APC was altered by loss of RXFP1, the stromal-vascular fraction of iWAT was extracted by collagenase treatment, and the APC isolated using antibody-coated magnetic beads (Miltenyi Biotec). The purified cells were cultured to confluence, treated with or without tamoxifen to induce CRE expression, then treated with differentiation cocktail. The APC from the RXFP1-PKO mice had a marked impairment in the ability differentiate to mature adipocytes after treatment with tamoxifen compared to untreated cells. In summary, the loss of RXFP1 in PDGFRβ-expressing cells resulted in resistance to HFD-induced weight and adipose tissue mass gain. This was accompanied by increased fibrosis in the iWAT and decreased adipocyte size. The APC had decreased adipogenic potential after loss of RXFP1. Taken together, the findings support a role for RXFP1 in the differentiation of adipose tissue progenitor cells, and in adipose tissue expansion after exposure to an obesogenic diet. Presentation: No date and time listed