Development of a model for inducing transient insulin resistance in the mare: preliminary implications regarding the estrous cycle.

The research article discusses the development of a model to induce temporary insulin resistance in horses for testing its effects on their reproductive cycle. The study revealed that insulin resistance could potentially modify the characteristics of the estrous cycle in mares.

Objective of Research

• The main aim of this research was to develop a model that can induce transient insulin resistance (IR) form of metabolic disease, in mares (female horses).
• This model was then used to investigate if such conditions can disrupt their reproductive or estrous cycle, thus impacting their fertility.

Research Methodology

• Two experiments were conducted in this research. In the first experiment, a procedure known as hyperinsulinemic-euglycemic clamp (HEC) was conducted on seven mares to measure their insulin sensitivity levels.
• After the initial HEC, the mares were infused with a lipid solution containing heparin, which was expected to induce insulin resistance.
• After a week, the HEC procedure was repeated to measure changes in insulin sensitivity levels.
• In the second experiment, the effects of induced insulin resistance on the reproductive cycle of the mares were studied by measuring changes in hormones and the duration of different phases of the estrous cycle.

Research Findings

• The research found that the administration of the lipid solution resulted in the mares developing insulin resistance which some maintained for a week.
• The induced insulin resistance did not affect the circulating concentrations of luteinizing hormone, nor the duration of the luteal phase of the estrous cycle.
• However, the insulin resistance did lengthen the interovulatory period (time between ovulations), and increased the peak concentrations of progesterone during the treated luteal phases of the estrous cycle.
• These results indicate the insulin resistance brought about by the lipid infusion could alter the characteristics of the estrous cycle in mares and possibly impact reproductive function.

Implications of the Research

• This study helps in better understanding the link between metabolic diseases like insulin resistance and reproductive health not only in horses but potentially in other mammals as well.
• These findings may also prove valuable in the study and treatment of fertility issues related to metabolic diseases in humans, like the polycystic ovarian syndrome.