title: Acute dietary restriction in heifers alters expression of genes regulating exposure and response to gonadotrophins and IGF in dominant follicles.
abstract: Dietary restriction in growing cattle and severe negative energy balance in lactating cows have been associated with altered gonadotropin secretion, reduced follicle diameter, reduced circulating oestradiol concentrations and anovulation. Therefore, we hypothesised that acute dietary restriction would influence the fate and function of the dominant follicle by altering the expression for genes regulating gonadotrophin and IGF response in ovarian follicles. Newly selected dominant follicles were collected 7-8 days after prostaglandin F(2α) (PGF) administration from heifers (n=25) that were individually fed a diet supplying 1.2 maintenance (M; control, n=8) or 0.4 M (restricted, n=17) for a total duration of 18-19 days. Heifers within 0.4 M were ovulatory (n=11) or anovulatory (n=6) depending on whether the dominant follicle present at PGF ovulated or became atretic following luteolysis. Control animals were all ovulatory. Acute dietary restriction decreased IGF-I (P<0.001) and insulin (P<0.05) in circulation; oestradiol (P<0.01) and IGF-I (P<0.01) in follicular fluid; and mRNA for FSHR (P<0.01) in granulosa cells but increased mRNA for IGFBP2 (P<0.05) in theca cells of the newly selected dominant follicle. However, this only led to anovulation when dietary restriction also decreased mRNA for CYP19A1 (P<0.05), IGF2 (P<0.01) and IGF1R (P<0.05) in granulosa cells and LHCGR (P<0.05) in theca cells of follicles collected from heifers fed 0.4 M. These results suggest that the catabolic environment induced by dietary restriction may ultimately cause anovulation by reducing oestradiol synthesis, FSH-responsiveness and IGF signaling in granulosa, and LH-responsiveness in theca cells of dominant follicles.
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Ireland.
authors: S W
authors: SW
authors: Walsh
authors: D
authors: D
authors: Matthews
authors: J A
authors: JA
authors: Browne
authors: N
authors: N
authors: Forde
authors: M A
authors: MA
authors: Crowe
authors: M
authors: M
authors: Mihm
authors: M
authors: M
authors: Diskin
authors: A C O
authors: AC
authors: Evans
mesh_terms: D000818:Animals; D000858:Anovulation / Q000235:genetics / Q000378:metabolism / Q000662:veterinary; D031204:Caloric Restriction / Q000662:veterinary; D002417:Cattle / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D005260:Female; D015571:Follicular Fluid / Q000187:drug effects / Q000378:metabolism; D005508:Food Deprivation / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006062:Gonadotropins / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D006080:Ovarian Follicle / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D010060:Ovulation / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010949:Plasma / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
chemical_list: D006062:Gonadotropins; D007334:Insulin-Like Growth Factor I