Neuroendocrine Correlates of Leptin

Glucose and Insulin Increase the Transport of Leptin through the Blood-Brain Barrier in Normal Mice but Not in Streptozotocin-Diabetic Mice
Abba J. Kastin, Victoria Akerstrom

VA Medical Center and Tulane University School of Medicine, New Orleans, La., USA

Address of Corresponding Author

Neuroendocrinology 2001;73:237-242 (DOI: 10.1159/000054640)

  Key Words

• Leptin
• Insulin
• Glucose
• Blood-brain barrier
• Streptozotocin
• Diabetes

  Abstract

Since fasting is one of the few factors found to change the rate of entry of leptin into brain, we used multiple-time regression analysis to study the effects of pretreatment with glucose or insulin on leptin transport across the blood-brain barrier (BBB). Two hours after intraperitoneal injection of glucose (3 g/kg), there was a statistically significant increase in the entry rate (K_i) of leptin in fasted (from 4.91 ± 0.70 × 10^-4 ml/g min to 9.03 ± 1.00 × 10^-4 ml/g min) but not (p = 0.15) in nonfasted normal (from 4.90 ± 1.21 × 10^-4 ml/g min to 6.42 ± 1.79 × 10^-4 ml/g min) or fasted streptozotocin (STZ)-treated diabetic mice (from 4.043 ± 0.959 × 10^-4 ml/g min to 5.395 ± 1.355 × 10^-4 ml/g min). Insulin (10 U/kg) increased leptin influx in fasted (from 4.77 ± 0.26 × 10^-4 ml/g min to 10.6 ± 0.15 × 10^-4 ml/g min at 0.5 h) and nonfasted (from 4.64 ± 0.75 × 10^-4 ml/g min to 7.46 ± 1.48 × 10^-4 ml/g min at 0.5 h) normal mice, but not in STZ-diabetic mice deficient in insulin (and leptin), even though basal concentrations of glucose were similarly increased in the nonfasted normal and STZ-treated mice. Moreover, the basal rate of leptin influx was the same in overnight fasted normal mice, nonfasted normal mice and STZ-diabetic mice. The results indicate that glucose and insulin can increase leptin transport, but they probably are not the principal factors responsible for the regulatory effect of the BBB on leptin entry into the brain.

Copyright © 2001 S. Karger AG, Basel

  Author Contacts

Abba J. Kastin, MD
VA Med Ctr/Tulane Med
1601 Perdido Street
New Orleans, LA 70112-1262 (USA)
Tel. +1 504 568 0811, ext. 5884, Fax +1 504 522 8559

  Article Information

Received: Received: June 29, 2000
Accepted after revision: October 19, 2000
Number of Print Pages : 6
Number of Figures : 3, Number of Tables : 0, Number of References : 33