The effect of short-term nutritional supplementation of ewes with lupin grain (Lupinus luteus) on folliculogenesis, the concentrations of hormones and glucose in plasma and follicular fluid and the follicular levels of P450 aromatase and IRS-1, -2 and -4

A Somchit-Assavacheep,R J Scaramuzzi,M Khalid,N R Kendall,B K Campbell

doi:10.1530/rep-12-0135

Abstract

An experiment was conducted on 48 ewes during follicular and luteal phases of the oestrous cycle to determine the effect of a 5-day lupin grain supplementation (500 g/day) on folliculogenesis, plasma concentrations of glucose, insulin, FSH and oestradiol-17β (E2), follicular fluid concentrations of glucose, E2, androstenedione and progesterone and the levels of P450 aromatase and insulin receptor substrate 1 (IRS-1), -2 and -4 in theca and granulosa cells. Average weight did not differ between lupin-fed and control groups. The numbers of follicles were increased (P<0.05; χ(2)) in the lupin-fed group. The plasma concentrations of glucose (P<0.05; ANOVA) and insulin (P<0.001; ANOVA) were higher in lupin-fed ewes. The plasma concentrations of FSH were not different but those of E2 were decreased (P<0.001) in the lupin-fed group. Both the follicular fluid concentration of E2 (P<0.05) and the level of P450 aromatase in granulosa cells (P<0.05; ANOVA) were decreased in the lupin-fed group, but only during the follicular phase. The level of P450 aromatase in granulosa cells was positively correlated with the concentration of E2 in follicular fluid (r=0.820; P<0.001; ANOVA). The levels of IRS-1 and -2 in theca and granulosa cell lysates were increased in the lupin-fed group. These data suggest that insulin has a local role in the control of folliculogenesis and is likely to be a mediator of the effects of dietary energy intake on ovulation rate. We suggest that insulin acting through IRS proteins mediates the reproductive actions of insulin in the follicle and that IRS-1 and -2 are nutritionally regulated mediators of the action of insulin in the follicle.

Highlights

The effects of nutrition on reproduction are well known and widely reported, and of the environmental factors influencing ovulation rate nutrition is one of the most important (Downing & Scaramuzzi 1991, Scaramuzzi et al 2006)
The results of this study confirm that short-term dietary supplementation with lupin grain increased the number of follicles in ewes (Table 1)
Many papers have reported that short-term nutritional supplementation increased the plasma concentrations of insulin in ewes (Downing & Scaramuzzi 1991, Downing et al 1995b, Williams et al 2001, Vinoles et al 2005, Somchit et al 2007), cows (Gutierrez et al 1997, Landau et al 2000, Gong et al 2002) and gilts (Ferguson et al 2003)

Summary

Introduction

The effects of nutrition on reproduction are well known and widely reported, and of the environmental factors influencing ovulation rate nutrition is one of the most important (Downing & Scaramuzzi 1991, Scaramuzzi et al 2006). An example of the short-term effect q 2013 Society for Reproduction and Fertility ISSN 1470–1626 (paper) 1741–7899 (online) of nutrition on ovulation rate is supplementation with lupin grain for 4–6 days before ovulation (Teleni et al 1989). This treatment increases the number of small follicles (Haresign 1981), ovulation rate (Oldham & Lindsay 1984) and prevents atresia of large follicles (Haresign 1981).

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