Protective effect of Nicotinamide on High glucose (HG)/Palmitate (PA)-induced Glucolipotoxicity to INS-1 beta cells

Prolonged exposure of pancreatic beta cells to excessive levels of glucose and fatty acids is postulated to contribute to beta cell dysfunction and beta cell death in type 2 diabetes. Nicotinamide, via its major metabolite NAD+, is involved in a wide range of biological processes, including the production of energy. Nicotinamide (NAM) significantly protected the cells against the HG/PA-induced cell death. The aim of this study is to determine which mechanism of protective effect of nicotinamide on high glucose/palmitate (HG/PA)―induced INS-1 beta cell death. Protective effect of NAM was due to its role as an anti-oxidant, NAD+ precursor, or inhibitor of NAD+-consuming enzyme. first, Anti-oxidant activity of NAM was investigated whether other anti-oxidant have a protective effect on HG/PA-induced INS-1 cell death. Anti-oxidant such as NAD or GSH, or Mito-TEMPOL were not protective against HG/PA-induced cell death. Second, NAM had a restorative effect on NAD+ depletion was determined whether replenishment of NAD+ prevented HG/PA-induced cell death. Treatment with exogenous nicotinamide mononucleotide (NMN) or L-Kynurenin (Kyn), or nicotinamide adenine dinucleotide (NAD+) prevented HG/PA-induced viability reduction. but replenishment of NAD+ precursor did not have a protective effect against HG/PA-induced cell death. We have investigated whether NAD salvage pathway is involved in the protective effect of NAM on HG/PA-induced cell death. Inhibition of NAD salvage pathway by Nampt inhibitor FK866 or knocking down the Nampt or knocking down the Nmnat did not protect against HG/PA-induced cell death. Furthermore, FK866 did not reduced NAM-induced protective effects. Third, We have investigated whether NAM has protective effect against HG/PA-induced cell death through role of poly(ADP-ribose) polymerase (PARP), cADP-ribose synthase (CD38) or SIRT inhibitors in HG/PA-induced cell death. Pharmacologic inhibitors of PARP such as 3-AB and INH2BP or reduction of PARP using siRNA did not protect HG/PA-induced viability reduction and HG/PA-induced DNA fragmentation. Knock down or overexpression of CD38 did not protect HG/PA-induced viability reduction and HG/PA-induced Caspase3 induction. Resveratrol, SIRT activator, slightly augmented HG/PA-induced cell death. But Sirtinol, SIRT inhibitor slightly reduced HG/PA-induced cell death. Knockdown of Sirt3 or Sirt4 protected HG/PA-induced viability reduction and HG/PA-induced DNA fragmentation. In contrast, overexpression of Sirt3 or Sirt4 augmented HG/PA-induced cell death. NAM reduced the level of HG/PA-induced ER stress maker such as phospho-JNK, CHOP or calnexin, but increased the level of survival signal such as P-Akt. Collectively these data suggest that nicotinamide has protective effect through inhibition of mitochondrial Sirt3 and Sirt4 in HG/PA-induced INS-1 beta cell death.

Author dc:creator

• 이, 수진

Contributors dc:contributor

• 강, 엽
• 대학원 의생명과학과
• 105644

• Glucolipotoxicity
• Nicotinamide
• NAD+
• Mitochondrial Sirtuins

Language dc:language

ko

Identifier

http://dcoll.ajou.ac.kr:9080/dcollection/jsp/common/DcLoOrgPer.jsp?sItemId=000000014958
000000014958

OAI identifier oai:identifier

oai:repository.ajou.ac.kr:201003/8602