An altered expression of components of the IGF system could contribute to follicular persistence in Holstein cows.

In dairy cows, reproductive diseases such as cystic ovarian disease (COD) represent a major problem that impacts on dairy production. It has been postulated that the insulin-like growth factor (IGF) system may contribute to follicular persistence and development of COD. Thus, the aim of the present study was to analyze relevant members of the IGF system in a critical period immediately after the expected time of ovulation, to obtain information about their role in follicular persistence in dairy cows. Proteins of the IGF system were evaluated at 0 (expected day of ovulation), 5, 10 and 15 days of follicular persistence to determine whether the changes previously detected in cows with COD occur early in COD pathogenesis. The serum concentration of IGF1 was higher in cows with 10 and 15 days of follicular persistence than in control cows. IGF1 expression in granulosa cells was similar in the follicles analyzed. In contrast, in theca cells, persistent follicles of days 5 and 10 showed the lowest IGF1 expression. IGF binding protein (IGFBP) 2 and 3 expression was lower in persistent follicles than in dominant follicles of the control group. Although IGF receptor (IGFR) 1 expression was similar in the groups analyzed, p-IGFR1 expression was significantly higher in dominant follicles of the control group than in persistent follicles. These data suggest alterations in the IGF system at the early stages of follicular persistence. The evidences obtained allow supporting that the IGF system could plays a key role in dairy cattle reproduction.

Alterations in the insulin signaling pathway in bovine ovaries with experimentally induced follicular persistence.

Reproductive diseases in dairy cows as cystic ovarian disease (COD) represent a major problem that impacts on dairy production. COD is characterized by anovulation, persistence of the dominant follicle, and interruption of normal estrous cycles. Anovulation is attributable to a failure in the LH surge, due to endocrine imbalances and alterations in local factors, such as the insulin signaling pathway. Thus, the aim of this study was to examine the expression of critical nodes of the insulin pathway, including insulin receptor (IR), IR substrate (IRS), phosphatidylinositol-3-kinase (PI3K), and protein kinase B (also known as Akt or pan-Akt), in ovarian follicular structures of cows during the development of follicular persistence induced by long-term progesterone administration. Immunoexpression of IR, p-IR, IRS1, p-IRS1, PI3K, pan-Akt and p-pan-Akt was evaluated in situ by immunohistochemistry and the concentration of insulin in serum and follicular fluid was determined by radioimmunoassay. p-IR, p-IRS1, PI3K and p-pan-Akt expression was decreased in follicles at different times of persistence in relation to the control dominant follicles, in both granulosa and theca cells, whereas IR and IRS1 immunoexpression was decreased in persistent follicles at 5 and 15 days of persistence in granulosa cells. Serum and follicular fluid insulin concentration was higher in cows with persistent follicles than in control cows. These results show that decreased expression and/or activation of the receptors and other intermediates of the insulin signaling pathway in persistent follicles indicates that reduced response/resistance to insulin rather than the concentration of insulin per se may be one of the important molecular mechanisms in the development of persistent follicles in dairy cows.

Liver fatty acid metabolism associations with reproductive performance of dairy cattle.

The peri-calving period is characterized by a negative energy balance, which leads to lipid mobilization. Thus, during this period, the liver has important functions related to optimizing milk yield, preventing metabolic and infectious diseases, and improving fertility. To clarify the relationship between liver fatty acid metabolism and reproductive performance, the present study was conducted to assess the abundance of specific hepatic proteins related to lipid metabolism in both plasma and follicular fluid in dairy cattle with different days to conception (DC). Sixteen animals were grouped according to DC, as more and fewer DC (MDC and FDC, respectively). Blood and liver biopsies were sampled 14 days before the expected calving date and 4, 14 and 28 days after calving. The plasma beta-hydroxybutyric acid (BHBA) concentrations and the liver triacylglycerol (TAG) content were greater in the MDC group (P <  0.05), whereas the protein abundance of carnitine palmitoyl transferase 1 was greater in the FDC group (P < 0.05). Additionally, total bilirubin (TBil) concentration was less in the FDC than MDC group on day 28 (P < 0.05). These results indicate lipid mobilization and liver fatty acid oxidation capacity in dairy cows could contribute to the adaptations and reproductive performance.