tofacitinib and Obesity

Breast cancer resistance protein (BCRP) is a member of ATP-binding cassette (ABC) transporter proteins whose primary function is to efflux substrates bound to the plasma membrane. Impaired intestinal barrier functions play a major role in chronic low-grade inflammation (CLGI)-associated obesity, but the regulation of BCRP during obesity and its role in maintaining the intestinal barrier function during CLGI-associated obesity are unknown. In the present study, using several approaches, including efflux assays, immunoprecipitation, immunoblotting, immunohistochemistry, paracellular permeability assay, FACS, cytokine assay, and immunofluorescence microscopy, we report that obese individuals have compromised intestinal BCRP functions and that diet-induced obese mice recapitulate these outcomes. We demonstrate that the compromised BCRP functions during obesity are because of loss of Janus kinase 3 (JAK3)-mediated tyrosine phosphorylation of BCRP. Our results indicate that JAK3-mediated phosphorylation of BCRP promotes its interactions with membrane-localized β-catenin essential not only for BCRP expression and surface localization, but also for the maintenance of BCRP-mediated intestinal drug efflux and barrier functions. We observed that reduced intestinal JAK3 expression during human obesity or JAK3 knockout in mouse or siRNA-mediated β-catenin knockdown in human intestinal epithelial cells all result in significant loss of intestinal BCRP expression and compromised colonic drug efflux and barrier functions. Our results uncover a mechanism of BCRP-mediated intestinal drug efflux and barrier functions and establish a role for BCRP in preventing CLGI-associated obesity both in humans and in mice.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily G, Member 2; beta Catenin; Biological Transport; Colon; Epithelial Cells; HT29 Cells; Humans; Insulin; Intestinal Mucosa; Janus Kinase 3; Mice; Mice, Knockout; Neoplasm Proteins; Obesity; Phosphorylation; Piperidines; Pyrimidines; Pyrroles; Tissue Inhibitor of Metalloproteinase-1

The rising incidence of obesity and related disorders such as diabetes and heart disease has focused considerable attention on the discovery of new therapeutics. One promising approach has been to increase the number or activity of brown-like adipocytes in white adipose depots, as this has been shown to prevent diet-induced obesity and reduce the incidence and severity of type 2 diabetes. Thus, the conversion of fat-storing cells into metabolically active thermogenic cells has become an appealing therapeutic strategy to combat obesity. Here, we report a screening platform for the identification of small molecules capable of promoting a white-to-brown metabolic conversion in human adipocytes. We identified two inhibitors of Janus kinase (JAK) activity with no precedent in adipose tissue biology that stably confer brown-like metabolic activity to white adipocytes. Importantly, these metabolically converted adipocytes exhibit elevated UCP1 expression and increased mitochondrial activity. We further found that repression of interferon signalling and activation of hedgehog signalling in JAK-inactivated adipocytes contributes to the metabolic conversion observed in these cells. Our findings highlight a previously unknown role for the JAK-STAT pathway in the control of adipocyte function and establish a platform to identify compounds for the treatment of obesity.

Topics: Adipocytes, Brown; Adipocytes, White; Animals; Bone Morphogenetic Protein 7; Cell Differentiation; Cells, Cultured; Gene Expression Profiling; Hedgehog Proteins; Humans; Interferon-gamma; Ion Channels; Janus Kinase 1; Janus Kinase 3; Male; Mice; Mice, Inbred C57BL; Mitochondria; Mitochondrial Proteins; Obesity; Oxazines; Phosphorylation; Piperidines; Protein Kinase Inhibitors; Pyridines; Pyrimidines; Pyrroles; STAT1 Transcription Factor; STAT3 Transcription Factor; Tumor Necrosis Factor-alpha; Uncoupling Protein 1; Veratrum Alkaloids

Obesity, a worldwide epidemic, is a major risk factor for the development of metabolic syndrome (MetS) including diabetes and associated health complications. Recent studies indicate that chronic low-grade inflammation (CLGI) plays a key role in metabolic deterioration in the obese population. Previously, we reported that Jak3 was essential for mucosal differentiation and enhanced colonic barrier functions and its loss in mice resulted in basal CLGI and predisposition to DSS induced colitis. Since CLGI is associated with diabetes, obesity, and metabolic syndrome, present studies determined the role of Jak3 in development of such conditions. Our data show that loss of Jak3 resulted in increased body weight, basal systemic CLGI, compromised glycemic homeostasis, hyperinsulinemia, and early symptoms of liver steatosis. Lack of Jak3 also resulted in exaggerated symptoms of metabolic syndrome by western high-fat diet. Mechanistically, Jak3 was essential for reduced expression and activation of Toll-like receptors (TLRs) in murine intestinal mucosa and human intestinal epithelial cells where Jak3 interacted with and activated p85, the regulatory subunit of the PI3K, through tyrosine phosphorylation of adapter protein insulin receptor substrate (IRS1). These interactions resulted in activation of PI3K-Akt axis, which was essential for reduced TLR expression and TLR associated NFκB activation. Collectively, these results demonstrate the essential role of Jak3 in promoting mucosal tolerance through suppressed expression and limiting activation of TLRs thereby preventing intestinal and systemic CLGI and associated obesity and MetS.

Topics: Animals; Body Weight; Caco-2 Cells; Cytokines; Diet, High-Fat; Disease Models, Animal; Genetic Predisposition to Disease; Glucose Tolerance Test; Humans; Immunity, Innate; Inflammation; Insulin; Janus Kinase 3; Liver; Male; Metabolic Syndrome; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Fluorescence; Obesity; Organ Size; Piperidines; Pyrimidines; Pyrroles; Risk Factors; Signal Transduction; Toll-Like Receptors