Effect of Obesity on the Preovulatory Follicle and Lipid Fingerprint of Equine Oocytes.

This study explored the effects of obesity on the reproductive system of mares, particularly the genes within follicle cells and lipid content within the oocytes. The research revealed that obesity can lead to differences in the expression of genes in follicle cells related to various cellular functions and affect insulin sensitivity as well as lipid composition within oocytes.

Research Methodology

• The study involved mares aged between 9 and 13 years. These were divided into two groups: controls (n = 8, normal weight, body condition score [BCS] 5.1, 10.4% body fat) and obese subjects (n = 9, BCS 7.9, 16.2% body fat).
• The researchers evaluated gene expression from granulosa cells (GC) and cumulus cells (CC) using RT-PCR, focusing on genes related to carbohydrate metabolism, inflammatory cytokines, lipid homeostasis, endoplasmic reticulum stress, and mitochondrial function.
• Serum and follicular fluid from the mares were assessed for insulin, leptin, adiponectin, and metabolite profiling.
• Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was used to acquire the lipid fingerprints of the oocytes from both groups.

Research Findings

• There were differences between the two groups concerning the expression of certain genes in GC and CC. In particular, genes for lipid homeostasis, endoplasmic reticulum stress, and mitochondrial function differed between the control and obese groups.
• Obese mares displayed lower insulin sensitivity and higher insulin and leptin levels in both serum and follicular fluid, with a noticeable difference to the control group.
• Several metabolites differed between control and obese subjects in serum and/or follicular fluid, showing correlations with the BCS and/or insulin sensitivity.
• Oocytes from control mares had greater concentrations of lipids consistent with phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins, while lipids that matched triglycerides were higher in obese mares.

Conclusions

• The findings suggest that obesity causes alterations in the follicle and oocyte in mares.
• It is still uncertain how these alterations may affect the conceptus (the product of conception at any point between fertilization and birth) and offspring, indicating this as a direction for future research in understanding the reproductive impact of maternal obesity.