Abstract
The factors regulating leptin mRNA under physiological conditions have not been fully
elucidated, although both insulin and glucose have been implicated. Since, in male
mice, plasma glucose decreases with age without a change in body weight or insulin,
aging mice constitute a model to examine effects of glucose independent of effects
of insulin or body weight. Therefore, we measured leptin mRNA in adipose tissue of
6-, 15- and 24-month-old C57BL/6J male mice, sacrificed either after a 48 h fast (nutritional
deprivation) or 15 min after an intraperitoneal injection of glucose (2 mg/g body
weight) (nutritional stimulation). There was a significant effect of both age and
nutritional status on leptin mRNA, correlated with effects of age and nutritional
status on plasma glucose. Leptin mRNA correlated with body weight, plasma glucose
and plasma insulin. After statistically removing effects of plasma glucose, the remaining
effects of age, nutritional status, and plasma insulin on leptin mRNA were no longer
significant. However, after statistically removing effects of plasma insulin, the
remaining effects of age, nutritional status, and plasma glucose continued to be significant.
When nutrition-deprived and nutrition-stimulated mice were analyzed separately, plasma
glucose significantly correlated with leptin mRNA in both groups, but body weight
and plasma insulin correlated with leptin mRNA only in nutrition-deprived mice. When
mice at each age were analyzed separately, glucose correlated with leptin mRNA at
every age, and after statistical removal of the effects of glucose, the remaining
effects of insulin on leptin mRNA were no longer significant at any age. These results
support the hypothesis that plasma glucose is important in the regulation of leptin
gene expression.
Key words
Obesity - Obese Gene - Insulin - Fasting - mRNA
