Recurrent, Moderate Hypoglycemia Ameliorates Brain Damage and Cognitive Dysfunction Induced By Severe Hypoglycemia

  1. Erwin C Puente1,
  2. Julie Silverstein, MD1,
  3. Adam J. Bree1,
  4. Daniel R. Musikantow1,
  5. David F. Wozniak, PhD2,
  6. Susan Maloney2,
  7. Dorit Daphna-Iken, PhD1 and
  8. Simon J. Fisher, MD, PhD (sfisher{at}dom.wustl.edu)1,3
  1. 1Division of Endocrinology, Metabolism, & Lipid Research, Department of Medicine
  2. 2Department of Psychiatry
  3. 3Department of Cell Biology and Physiology, Washington University, St. Louis, MO

Abstract

Objective: Although intensive glycemic control achieved with insulin therapy increases the incidence of both moderate and severe hypoglycemia, clinical reports of cognitive impairment due to severe hypoglycemia have been highly variable. It was hypothesized that recurrent moderate hypoglycemia “preconditions” the brain and protect against damage caused by severe hypoglycemia.

Research Design and Methods: Nine-week old male Sprague-Dawley rats were subjected to either three consecutive days of recurrent, moderate (25-40 mg/dl) hypoglycemia (RH) or saline injections. On the fourth day, rats were subjected to a hyperinsulinemic (0.2 U/kg/min) severe hypoglycemic (∼11 mg/dl) clamp for 60 or 90 minutes. Neuronal damage was subsequently assessed by H&E and Fluoro-Jade B staining. The functional significance of severe hypoglycemia induced brain damage was evaluated by motor and cognitive testing.

Results: Severe hypoglycemia induced brain damage and striking deficits in spatial learning and memory. Recurrent moderate hypoglycemia pretreated rats had 62-74% less brain cell death and were protected from most of these cognitive disturbances.

Conclusions: Antecedent recurrent moderate hypoglycemia “preconditioned” the brain and markedly limited both the extent of severe hypoglycemia induced neuronal damage and associated cognitive impairment. In conclusion, changes brought about by recurrent moderate hypoglycemia can be viewed, paradoxically, as providing a beneficial adaptive response in that there is mitigation against severe hypoglycemia induced brain damage and cognitive dysfunction.

Footnotes

    • Received October 8, 2009.
    • Accepted January 6, 2010.