Acute dietary restriction in heifers alters expression of genes regulating exposure and response to gonadotrophins and IGF in dominant follicles

Walsh, S.W., Matthews, D., Browne, J.A., Forde, N., Crowe, M.A., Mihm Carmichael, M., Diskin, M. and Evans, A.C.O. (2012) Acute dietary restriction in heifers alters expression of genes regulating exposure and response to gonadotrophins and IGF in dominant follicles. Animal Reproduction Science, 133(1-2), pp. 43-51. (doi: 10.1016/j.anireprosci.2012.06.012)

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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 F2α (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.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Mihm Carmichael, Dr Monika
Authors: Walsh, S.W., Matthews, D., Browne, J.A., Forde, N., Crowe, M.A., Mihm Carmichael, M., Diskin, M., and Evans, A.C.O.
Subjects:S Agriculture > SF Animal culture > SF600 Veterinary Medicine
College/School:College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
Journal Name:Animal Reproduction Science
Publisher:Elsevier BV
ISSN:0378-4320
Published Online:23 June 2012

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