Systemic but Not Intraovarian Concentrations of Insulin-Like Growth Factor-I are Affected by Short-Term Fasting1

Abstract

To determine whether systemic and/or intraovarian concentrations of insulin-like growth factor-I (IGF-I) are affected by short-term fasting, 24 heifers were blocked by weight and, within block, were assigned to one of three treatments: fasted for 0 h (controls; n = 8), fasted for 24 h (n = 8), or fasted for 48 h (n = 8). Blood plasma was collected every 8 h from -64 h to 0 h before ovariectomy (OVEX). OVEX was performed per vagina under local anesthesia during the follicular phase of an estrous cycle (36-42 h after synchronization with prostaglandin-F2 alpha). Follicular fluid (FFL) and granulosa cells were collected individually from follicles greater than or equal to 6 mm (large), and FFL was pooled from follicles 1.0-5.9 mm (small) in diameter. Fasting did not affect (p greater than 0.20) the number (mean +/- SE) of small (52 +/- 7) or large (1.5 +/- 0.4) follicles per heifer, specific binding of 125I-hCG to granulosa cells of follicles greater than or equal to 8 mm in diameter, or concentrations of progesterone in FFL of small follicles. At OVEX, body weight was less (p less than 0.01) for 24 h- and 48 h-fasted heifers (412 +/- 7 kg and 399 +/- 7 kg, respectively) than for 0 h-fasted heifers (442 +/- 7 kg). At OVEX, plasma concentrations of IGF-I were lower (p less than 0.05) in the 48 h-fasted group (105 +/- 8 ng/ml) than in the 0 h-fasted group (140 +/- 8 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of IGF1 in the in vivo production of bovine embryos from superovulated donors

“…Although plasma IGF1 was not associated with impaired oocyte competence during over-nutrition (Adamiak et al 2005), it cannot be completely ruled out, as a direct effect of liverproduced IGF1 on ovarian activity will depend on how much circulating bioactive IGF1 impacts on the ovaries. IGF1 in follicular fluid has been found to be either lower (Echternkamp et al 1990, Spicer et al 1991, equal (Spicer et al 1992) or greater than peripheral IGF1 (Spicer et al 1992, Ortega et al 2008. This emphasizes the importance of measuring both IGF1 and IGFBPs concentrations in reproductive tracts in experimental trials.…”

Effect of the dry matter intake level on the sanguine profile of glucose, insulin, urea, estrogen and progesterone and concentration of IGF-I in the follicular liquid of crossbred heifers

“…The IGF-I is a potent regulator of the bovine folicullargenesys (O'Callaghan et al, 2000) related to the increase in the answer of the follicles to the gonadotrophins (Webb et al, 1999). Spicer et al (1992) also didn't find difference in the concentration of IGF-I of the follicular fluid in heifers after 24 to 48 hours of fast, in spite of having found difference in the sanguine concentrations of this hormone. Thus, it seemed that the concentrations of intrafollicular IGF-I were more resistant to the effects of the dietary manipulations than the systemic concentrations (O'Callaghan et al, 2000).…”

“…The ovaries were maintained at 37º C and taken to the laboratory, where the liquid of the medium sized follicles (5-9 mm) and big sized (>10 mm) were aspirated and later stored in Eppendorf flasks at -20º C, for the IGF-I analyses (ELISA) (Spicer et al, 1992). Data were subjected to statistical analysis using the SAS program (SAS, 1998).…”

Effect of exogenous insulin and fasting on growth hormone receptor and IGF-I expression in the pre-ovulatory follicle of ewes

“…However, there is conflicting evidence that ovarian IGF-I production is regulated by GH, as it is in the liver (Lucy, 2000), and therefore the intrafollicular IGF-I origin remains unclear. In addition to that, a systemic decrease of IGF-I is not followed by intrafollicular decrease of its levels in large follicles (Spicer et al, 1992), as observed in medium follicles (Schoppee et al, 1996). These data indicate that systemic and ovarian IGF-I production in large follicles is not subjected to the same regulatory factors and that it is important to uncover which factors can alter ovarian expression of IGF-I.…”

“…In this regard, ovarian follicular growth can be compromised, since it is controlled by several systemic and local intraovarian factors (Spicer et al, 1992). Physiologically, various metabolic messengers, including insulin and glucose, function to convey nutritional status to other systems within the body (Whitley et al, 2000).…”