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Articles by L Kang
Total Records ( 2 ) for L Kang
  E. D Berglund , L Kang , R. S Lee Young , C. M Hasenour , D. G Lustig , S. E Lynes , E. P Donahue , L. L Swift , M. J Charron and D. H. Wasserman

Hepatic glucagon action increases in response to accelerated metabolic demands and is associated with increased whole body substrate availability, including circulating lipids. The hypothesis that increases in hepatic glucagon action stimulate AMP-activated protein kinase (AMPK) signaling and peroxisome proliferator-activated receptor- (PPAR) and fibroblast growth factor 21 (FGF21) expression in a manner modulated by fatty acids was tested in vivo. Wild-type (gcgr+/+) and glucagon receptor-null (gcgr–/–) littermate mice were studied using an 18-h fast, exercise, and hyperglucagonemic-euglycemic clamps plus or minus increased circulating lipids. Fasting and exercise in gcgr+/+, but not gcgr–/– mice, increased hepatic phosphorylated AMPK at threonine 172 (p-AMPKThr172) and PPAR and FGF21 mRNA. Clamp results in gcgr+/+ mice demonstrate that hyperlipidemia does not independently impact or modify glucagon-stimulated increases in hepatic AMP/ATP, p-AMPKThr172, or PPAR and FGF21 mRNA. It blunted glucagon-stimulated acetyl-CoA carboxylase phosphorylation, a downstream target of AMPK, and accentuated PPAR and FGF21 expression. All effects were absent in gcgr–/– mice. These findings demonstrate that glucagon exerts a critical regulatory role in liver to stimulate pathways linked to lipid metabolism in vivo and shows for the first time that effects of glucagon on PPAR and FGF21 expression are amplified by a physiological increase in circulating lipids.

  L Kang , X Zhang , Y Xie , Y Tu , D Wang , Z Liu and Z. Y. Wang

Accumulating evidence suggested that an orphan G protein-coupled receptor (GPR)30, mediates nongenomic responses to estrogen. The present study was performed to investigate the molecular mechanisms underlying GPR30 function. We found that knockdown of GPR30 expression in breast cancer SK-BR-3 cells down-regulated the expression levels of estrogen receptor (ER)-36, a variant of ER-. Introduction of a GPR30 expression vector into GPR30 nonexpressing cells induced endogenous ER-36 expression, and cotransfection assay demonstrated that GPR30 activated the promoter activity of ER-36 via an activator protein 1 binding site. Both 17β-estradiol (E2) and G1, a compound reported to be a selective GPR30 agonist, increased the phosphorylation levels of the MAPK/ERK1/2 in SK-BR-3 cells, which could be blocked by an anti-ER-36-specific antibody against its ligand-binding domain. G1 induced activities mediated by ER-36, such as transcription activation activity of a VP16-ER-36 fusion protein and activation of the MAPK/ERK1/2 in ER-36-expressing cells. ER-36-expressing cells, but not the nonexpressing cells, displayed high-affinity, specific E2 and G1 binding, and E2- and G1-induced intracellular Ca2+ mobilization only in ER-36 expressing cells. Taken together, our results demonstrated that previously reported activities of GPR30 in response to estrogen were through its ability to induce ER-36 expression. The selective G protein-coupled receptor (GPR)30 agonist G1 actually interacts with ER-36. Thus, the ER- variant ER-36, not GPR30, is involved in nongenomic estrogen signaling.

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