Ns of ATP and ADP. In pancreatic cells, KATP channels are inhibited or activated in response for the rise or fall in blood glucose levels, top to changes in membrane excitability and insulin secretion (two, 3). Therefore, KATP channel gating has been considered a vital mechanism in coupling blood glucose levels to insulin secretion. Lately, trafficking of KATP channels for the plasma membrane was highlighted as another significant mechanism for regulating KATP channel activity (four). AMPactivated protein kinase (AMPK) is really a important enzyme regulating energy homeostasis (7). We lately demonstrated that KATP channels are recruited towards the plasma membrane in glucosedeprived conditions via AMPK signaling in pancreatic cells (six). Inhibition of AMPK signaling significantly reduces KATP currents, even after comprehensive washout of intracellular ATP (six). Provided these benefits, we proposed a model that recruitment of KATP channels to the plasma membrane by way of AMPK signaling is vital for KATP channel activation in lowglucose situations. On the other hand, the physiological relevance of this model remains unclear since pancreatic cells had to be incubated in media containing much less than 3 mM glucose to recruit a adequate quantity of KATP channels towards the plasma membrane (six). We thus hypothesized that there ought to be an endogenous ligand in vivo that promotes AMPKdependent KATP channel trafficking sufficiently to stabilize pancreatic cells at physiological fasting glucose levels. Leptin is an adipocytederived hormone that regulates meals intake, physique weight, and glucose homeostasis (eight, 9). In additionTAuthor contributions: S.H.P., S.H.L., P.O.B., J.H.J., and W.K.H. developed research; S.H.P., S.Y.R., W.J.Y., Y.E.H., Y.S.J., K.O., J.P.J., and H.L. performed study; S.H.P., S.Y.R., Y.S.J., K.H.L., and W.K.H. analyzed information; and S.H.P., S.Y.R., J.W.S., A.L., P.O.B., J.H.J., and W.K.H. wrote the paper. The authors declare no conflict of interest. This article can be a PNAS Direct Submission.To whom correspondence might be addressed.3,3,3-Triethoxyprop-1-yne Order Email: wonkyung@snu.Cryptand 2.2.2 uses ac.PMID:23074147 kr or jhjeon2@ snu.ac.kr.This short article contains supporting info on the web at www.pnas.org/lookup/suppl/doi:ten. 1073/pnas.1216351110//DCSupplemental.www.pnas.org/cgi/doi/10.1073/pnas.PNAS | July 30, 2013 | vol. 110 | no. 31 | 12673CELL BIOLOGYIn our earlier in vitro study using the insulinsecreting cell line INS1, glucose concentration less than three mM was essential to induce maximal AMPK activation and KATP channel trafficking (6). Nevertheless, the imply blood glucose level in the WT fed mice was 244 14 mg/dL (13.5 mM, n = ten), and that inside the WT fasted mice was 138 11 mg/dL (7.7 mM, n = 10), which may not be sufficient to completely activate AMPK activity. Consequently, we supposed the presence of an endogenous ligand in vivo that induces AMPK activation and KATP channel trafficking and tested the concept that leptin plays this function making use of ob/ob mice lacking this hormone. In contrast to observations in WT mice, a distinct staining pattern indicating surface translocation of SUR1 and Kir6.two was lost in islet cells of ob/ob mice obtained following a 12h fasting period (Fig. 1B and Fig. S1). Interestingly, this pattern was restored when ob/ob mice were treated with leptin for four d (two g/d) (15) (Fig. 1B and Fig. S1), indicating that leptin is crucial for the surface translocation of Kir6.2 throughout fasting in vivo. Intracellular localization of KATP channels has been studied by quite a few groups, but outcomes are controversial (4, 16). For the reason that endosomal recycl.
