Insulin gene expression pattern in rat pancreas during the estrous cycle

Area of Science:

• Endocrinology
• Reproductive Biology
• Metabolic Research

Background:

• Sex steroid hormones, including estradiol (E2) and progesterone (P4), are known to affect insulin homeostasis and glucose metabolism.
• Previous research indicates E2 and P4 influence fasting and postprandial insulin levels in rodents.
• The specific pattern of insulin gene expression during the rodent estrous cycle remains largely uncharacterized.

Purpose of the Study:

• To investigate and define the pattern of insulin gene expression throughout the estrous cycle in rats.
• To correlate insulin gene expression with circulating levels of key sex hormones and serum insulin concentrations.

Main Methods:

• Adult rats were studied daily throughout their estrous cycle (n=6 per day).
• Serum concentrations of progesterone (P4), estradiol (E2), testosterone (T), and insulin were quantified using radioimmunoassay (RIA).
• Insulin gene expression in pancreatic tissue was assessed via Northern blot analysis.

Main Results:

• A significant variation in insulin gene expression was observed across the estrous cycle.
• The highest insulin gene expression levels were detected on the proestrus day.
• Insulin mRNA levels positively correlated with circulating E2 and P4 concentrations, but not testosterone (T).
• Variations in serum insulin levels throughout the cycle mirrored the observed changes in pancreatic insulin mRNA content.

Conclusions:

• Insulin gene expression in rats exhibits distinct fluctuations during the estrous cycle.
• Circulating levels of estradiol (E2) and progesterone (P4) are key regulators of insulin gene expression and serum insulin levels during the estrous cycle.
• These findings highlight a direct link between reproductive hormone status and pancreatic insulin regulation.