title: The effects of caloric restriction and a high-fat diet on ovarian lifespan and the expression of SIRT1 and SIRT6 proteins in rats.
abstract: OBJECTIVE
  Caloric restriction (CR) extends mammals' lifespans and suppresses ovary development. Sirtuins are involved in these mechanisms. If, and to what extent CR affects ovarian lifespan and follicle development is largely unknown. We investigated the effects of moderate and severe caloric restriction compared with a high-fat dietary regimen on ovarian follicle reserves in rats.
  
  
  METHODS
  Female Sprague-Dawley rats (n=48) randomly divided into four groups including normal control (NC), 25% caloric restriction (MCR), 45% CR (SCR) and high-fat diet (HF) were maintained on these regimens for 2 months.
  
  
  RESULTS
  Histological analysis showed that both the 25 and 45% CR rats had a significantly higher percentage of primordial follicles and a larger number of healthy follicles than the NC rats, whereas the HF rats did not differ significantly from the NC rats. Immunohistochemical analysis revealed that SIRT1 and SIRT6 proteins were present in the nucleus and cytoplasm of the oocytes. The 25% CR diet increased the expression of both SIRT1 and SIRT6 in the ovary, whereas the 45% CR and HF diets caused a decrease in SIRT1 expression. The level of SIRT6 protein did not change with the 45% CR diet, and it appeared slightly lower in the HF than in the NC groups.
  
  
  CONCLUSIONS
  Caloric restriction may inhibit the transition from primordial to developing follicles and extend the entire growth phase of a follicle to preserve the reserve of germ cells. SIRT1 and SIRT6 are both associated with these effects.
authors.affiliation: Department of Gynecology and Obstetrics, The First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong 515041, PR China. luolili6606@yahoo.com
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Luo
authors.forename: Xiao-Chun
authors.initials: XC
authors.lastname: Chen
authors.forename: Yu-Cai
authors.initials: YC
authors.lastname: Fu
authors.forename: Jin-Jie
authors.initials: JJ
authors.lastname: Xu
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Xuan-Hao
authors.initials: XH
authors.lastname: Lin
authors.forename: Yan-Fang
authors.initials: YF
authors.lastname: Xiang
authors.forename: Xing-Mei
authors.initials: XM
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology; D031204:Caloric Restriction; D002784:Cholesterol / Q000097:blood; D059305:Diet, High-Fat; D002149:Energy Intake / Q000502:physiology; D005260:Female; D006080:Ovarian Follicle / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D056564:Sirtuin 1 / Q000096:biosynthesis* / Q000378:metabolism; D037761:Sirtuins / Q000096:biosynthesis* / Q000378:metabolism; D014280:Triglycerides / Q000097:blood
chemical_list: D014280:Triglycerides; D002784:Cholesterol; C488368:Sirt1 protein, rat; D056564:Sirtuin 1; D037761:Sirtuins; C560607:sirtuin 6, rat