Thus, we consider that the effects of hSeP- and AE2 administration on insulin resistance and insulin secretion, at least in part, might be related to differences in basal blood glucose in this experimental model
Thus, we consider that the effects of hSeP- and AE2 administration on insulin resistance and insulin secretion, at least in part, might be related to differences in basal blood glucose in this experimental model. mapping reveals that AE2 HJC0152 recognizes a region of human SeP adjacent to the first histidine-rich region (FHR). A polyclonal antibody against the mouse SeP FHR improves glucose intolerance and insulin secretion in a mouse model of diabetes. This report describes a novel molecular strategy for the development of type 2 diabetes therapeutics targeting SeP. Selenoprotein P is secreted by the liver and when present in excess it promotes development of type 2 diabetes. Here the authors develop neutralizing antibodies to target human and mouse selenoprotein P, and show that they improve insulin secretion and glucose tolerance in mouse models. Introduction Selenoprotein P (SeP; encoded by were used (Supplementary Fig.?1a). In preliminary experiments using undifferentiated C2C12 cells, significant binding of hSeP was detected (Fig.?1a). We next incubated undifferentiated C2C12 cells with hSeP and each monoclonal antibody (mAb). We found that mAbs such as AE2 and BD1 significantly inhibited the binding of hSeP to C2C12 cells (Fig.?1a). We also observed significant binding of hSeP and inhibitory effects of several mAbs in Jurkat cells (Supplementary Figs.?1b and 1c). Open in a separate window Fig. 1 Identification of antibodies inhibiting the binding and HJC0152 selenium supply of SeP. a Inhibitory effects of monoclonal antibodies on the interaction between undifferentiated C2C12 cells and human SeP. C2C12 cells were incubated with purified human SeP (hSeP) protein (0.5?g/mL) in the absence (left panel) or the presence (right panel) of each mAb (10?g/mL) at 4?C, and then SeP binding was analysed (was observed in MIN6 cells, and the level of expression of was higher than that of others (Supplementary Fig.?6d). Treatment of MIN6 cells with expression is regulated via an AMPKCFoxOs axis, and metformin, a drug widely used for the treatment of type 2 diabetes, suppresses SeP expression via an AMPKCFoxO3a HJC0152 pathway18, HJC0152 43, 44. Because conditions of high glucose and high lipid culture inhibit AMPK activity, these nutritional factors are thought to up-regulate SeP expression in hepatocytes. Production of SeP by hepatocytes plays a central role in Se homoeostasis and distribution of Se from the liver to peripheral tissues45, 46. As with other Sec-containing proteins, the synthesis of SeP is greatly influenced by Sec incorporation, which is significantly affected by Se status, the availability of sec-tRNA[ser]sec and post-transcriptional factors45C47. Dietary Se incorporated into the liver is converted to sec-tRNA[ser]sec or excretory metabolites such as selenosugars, and the syntheses of these seleno-metabolites compete with each other48. sec-tRNA[ser]sec in the liver is used for the synthesis of cellular selenoproteins or SeP. Therefore, it is considered that adequate Se supply to maintain sec-tRNA[ser]sec levels alone does not fully explain the high levels of serum SeP protein seen in mouse models of diabetic and in patients with type 2 diabetes. These results and previous reports suggest that both sufficient Se and an increase of SeP mRNA levels might be the key to the increase in serum SeP levels observed in diabetes. The results of the present study showed clear changes in the levels of endogenous mSeP in the presence of exogenous hSeP (Supplementary Fig.?5a), and this phenomenon has also been suggested in a previous study17. These observations lead us to speculate that injection with hSeP reduced production of endogenous mSeP in the liver and/or increased excretion of mSeP into urine in mice. These speculations suggest that an unknown sensor-like system of SeP might be Rabbit Polyclonal to GRP94 present to maintain whole-body Se homoeostasis, and that SeP receptors might be related to this system. The elucidation of this sensor-like system of SeP might be noteworthy for understanding not only the physiological control of SeP levels in blood but also the pathological change of SeP levels including type 2 diabetes. The epitope of neutralizing Abs indicates the site in SeP that is important for the interaction with the cell surface27, 49. Heparin-binding properties of SeP have been known to HJC0152 mediate endocytosis of SeP, and lipoprotein receptors such as ApoER2, megalin and LRP1 have been identified as receptors for SeP8C10, 15, 50. The YWTD -propeller domain of ApoER2 has been identified as an SeP-binding site, while the C-terminal domain of SeP alone can bind to.