Changes in insulin sensitivity from stress during repetitive sampling in anesthetized rats

Area of Science:

• Endocrinology
• Physiology
• Metabolic Research

Background:

• Insulin sensitivity and glucose turnover are critical metabolic parameters.
• Accurate assessment of these parameters is vital for understanding metabolic diseases.
• Stress responses can significantly influence endocrine and metabolic functions.

Purpose of the Study:

• To investigate the impact of repetitive blood sampling on insulin sensitivity and glucose metabolism in rats.
• To determine the threshold of blood loss that induces a significant stress response affecting metabolic measurements.
• To identify potential sources of error in glucose clamp experiments due to physiological stress.

Main Methods:

• Anesthetized rats underwent glucose clamp studies.
• Cumulative blood loss was induced through repetitive sampling.
• Plasma levels of glucose, insulin, adrenocorticotropic hormone (ACTH), and corticosterone were measured.
• Hepatic glucose output (HGO) and glucose disposal were assessed.

Main Results:

• Glucose disposal decreased significantly with cumulative blood loss (9 ml/kg).
• Hepatic glucose output (HGO) increased significantly with blood loss (9 ml/kg and 15 ml/kg).
• Plasma ACTH and insulin levels rose significantly with blood loss (8-10 ml/kg), indicating a stress response.
• Plasma corticosterone levels mirrored ACTH, confirming adrenal activation due to stress.

Conclusions:

• Stress induced by cumulative blood loss exceeding 7 ml/kg can significantly alter glucose turnover and insulin sensitivity.
• Repetitive blood sampling in rats can elicit a stress response that confounds the interpretation of glucose clamp data.
• Researchers should consider the impact of blood loss volume on physiological stress when designing and interpreting clamp experiments in rats.