title: Niacin receptor GPR109A inhibits insulin secretion and is down-regulated in type 2 diabetic islet beta-cells.
abstract: We previously found niacin receptor GPR109A was expressed in murine islet beta-cells, and signaling through GPR109A inhibited glucose stimulated insulin secretion (GSIS). However, the expression of GPR109A in human islets and its functional relevance is still not known.
  
  
  
  The expression of GPR109A was examined by antibody staining and in situ hybridization on pancreatic paraffin sections. GPR109A was cloned and expressed in INS-1 islet beta-cells. Intracellular cAMP and GSIS were determined using enzyme-linked immunosorbent assay (ELISA).
  
  
  
  The expression of GPR109A was confirmed in murine islet beta-cells and further detected in human counterparts by using commercially available polyclonal antibodies. In situ hybridization study detected the transcripts of GPR109A, but not that of closely related GPR109B. Furthermore, GPR109A was significantly reduced in islets from diabetic individuals and animal model of db/db mice as compared to their respective controls. Further, GPR109A levels in insulinoma were also reduced dramatically as compared to islets found in corresponding non-tumor normal tissues. Quantitative RT-PCR analysis demonstrated that GPR109A transcripts were severely down-regulated in rodent insulinoma cell lines as compared to that of freshly isolated islets from mice. Finally, human and murine GPR109A expression cassettes were transfected into INS-1 cells, which resulted in reduced accumulation of cAMP and insulin secretion after incubation with niacin. The effect could be completely abrogated by pretreatment with pertussis toxin.
  
  
  
  These results demonstrate that GPR109A is functionally expressed in both human and murine islet beta-cells. However, the role of GPR109A in the prevention of diabetes or insulinoma needs further study.
authors: Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, China.
authors: Na
authors: N
authors: Wang
authors: Department of Pathology, Xinan Hospital of Chongqing, Chongqing 400038, China.
authors: De-Yu
authors: DY
authors: Guo
authors: Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, China.
authors: Xiong
authors: X
authors: Tian
authors: Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, China.
authors: Hao-Peng
authors: HP
authors: Lin
authors: Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, China.
authors: Yun-Pan
authors: YP
authors: Li
authors: Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, China.
authors: Shao-Jun
authors: SJ
authors: Chen
authors: Laboratory of Cell Senescence, Shantou University Medical College, Shantou, Guangdong 515041, China.
authors: Yu-Cai
authors: YC
authors: Fu
authors: Department of Endocrinology, The First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong 515041, China. Electronic address: xuwcan@163.com.
authors: Wen-Can
authors: WC
authors: Xu
authors: Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, China. Electronic address: chijuwei@stu.edu.cn.
authors: Chi-Ju
authors: CJ
authors: Wei
mesh_terms: D000368:Aged; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D007340:Insulinoma / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: C530636:HCAR2 protein, human; C473652:Hcar2 protein, mouse; D007328:Insulin; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D011978:Receptors, Nicotinic; D000242:Cyclic AMP; D005947:Glucose
keywords: Diabetes; GPR109A; Insulin secretion; Insulinoma; Niacin