The effect of a direct arterial infusion of insulin and glucose on the ovarian secretion rates of androstenedione and oestradiol in ewes with an autotransplanted ovary

Abstract

Improving ewe nutrition even for short periods will increase ovulation rate. The increased nutrients must in some way affect the number of follicles that develop to the pre-ovulatory stage. One possible mechanism is that a nutrient or a metabolic hormone that responds to nutrition might act directly on the ovary to influence follicle development and/or follicle selection. In the study described here, insulin and glucose, alone or together, were infused directly into the ovarian artery of ewes with an autotransplanted ovary, for 13·5 h on day 11 of the oestrous cycle. The pattern of androstenedione and oestradiol secretion in response to a GnRH-stimulated LH pulse was measured 2·5 h before and 12·5 h and 24·5 h after the start of the infusion. Glucose or insulin infused alone had no effect on the secretion of androstenedione and oestradiol. However, when infused together, they decreased significantly the secretion of androstenedione and, to a lesser extent, oestradiol. We suggest that the sudden availability of additional glucose and insulin increases insulin-stimulated glucose uptake by the follicle. This leads to an inhibition of LH-stimulated steroidogenesis by the ovarian follicle which occurs in the absence of any detectable changes in circulating plasma concentrations of FSH. These results show that insulin and glucose act together to influence ovarian function directly and suggest that the effects of short-term nutrition on ovulation rate may be mediated by a direct ovarian action of insulin and glucose.

The effect of systemic and ovarian infusion of glucose, galactose and fructose on ovarian function in sheep

“…We have shown that both SLC2A1 (GLUT1; the facultative glucose transporter) and SLC2A4 (GLUT4; the inducible insulin-dependent glucose transporter) are present in granulosa and theca cells (Williams et al 2001) and that glucose downregulates both SLC2A1 and SLC2A4 expression in cultured granulosa cells . Further, we have shown that there is a significant uptake of glucose by the ovary in both the follicular and luteal phases of the oestrous cycle and that the administration of gluconeogenic amino acids to ewes will increase insulin concentrations and stimulate folliculogenesis (Downing et al 1999). Conversely, more recent data have shown that systemic infusion of high doses of glucose (10 mM/h) results in an acute increase in peripheral insulin concentrations, a decline in ovarian oestradiol secretion, a marked stimulation in the number of small antral follicles and a depression in aromatase and phosphorylated AKT and AMPK expression in granulosa cells (C Gallet, J Dupont, BK Campbell, D Monniaux & R Scaramuzzi 2010, unpublished observations).…”

Effect of different levels of short-term feed intake on folliculogenesis and follicular fluid and plasma concentrations of lactate dehydrogenase, glucose, and hormones in Hu sheep during the luteal phase

“…The effect of short-term supplementation on concentration of E 2 during luteal phase is equivocal, with reports for (Downing et al 1999, Munoz-Gutierrez et al 2005 and against (Viñ oles et al 2005, Somchit et al 2007) the induction of a change. In accordance with a previous study (Somchit et al 2007), the follicular fluid concentration of E 2 was not affected by supplementation (Fig.…”

“…Insulin was a nutritional mediator regulating folliculogenesis (Downing & Scaramuzzi 1995, Downing et al 1999. Glucagon is a key hormone in glucose homeostasis acting to promote gluconeogenesis and increase glucose output from liver by increasing hepatic glycogenolysis and gluconeogenesis and by promoting ketogenesis and might improve reproductive performance indirectly by increasing concentrations of plasma glucose and insulin (Bobe et al 2007).…”

“…The nutritional signals were speculated to directly regulate folliculogenesis at the ovarian level by affecting follicular atresia (Downing et al 1999, Munoz-Gutierrez et al 2002, Viñoles et al 2005, Somchit et al 2007, thereby increasing the pool of ovulatory follicles. To our knowledge, this is the first study investigating the association between folliculogenesis and intrafollicular metabolic and endocrine milieu, when being in the short-term different nutritional status.…”

The effect of monosaccharide sugars and pyruvate on the differentiation and metabolism of sheep granulosa cells in vitro

“…Evidence of glucose transporter expression (SLC2A1 and SLC2A4) on granulosa and theca cells of ovine antral follicles (Williams et al 2001) and ovarian arteriovenous difference studies both suggest that significant amounts of glucose can be taken up by the ovary (Rabiee et al 1997). In addition, glucose infused in combination with insulin into the ovarian artery of ewes with ovarian autotransplants directly suppressed androstenedione and oestradiol (E 2 ) production from the dominant follicle without affecting peripheral gonadotrophin concentrations (Downing et al 1999).…”