Diabetes, Vol 49, Issue 7 1203-1208, Copyright © 2000 by American Diabetes Association
Transient effects of long-term leptin supplementation in the prevention of diet-induced obesity in mice
RS Surwit, CL Edwards, S Murthy and AE Petro
Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, North Carolina 27710, USA. richard.surwit@duke.edu
Low plasma leptin levels have been shown to be associated with the
development of obesity in mice as well as in humans. The present study was
undertaken to determine if raising plasma leptin levels of obesity-prone
C57BL/6J (B6) mice to those seen in obesity-resistant A/J mice would
prevent the development of diet-induced obesity. Four-week-old B6 (n = 40)
and A/J (n = 10) male mice were weaned onto a low-fat (11% kcal) diet. When
the animals weighed 20 g, their diets were changed to a high-fat (HF) diet
(58% kcal), and a continuous infusion of leptin (0.4 mg x kg(-1) x day(-1))
or phosphate-buffered saline (control) was started using Alzet minipumps.
The A/J mice were not treated but were included to monitor the efficacy of
the minipumps in raising plasma leptin in B6 mice. The mice were followed
for 12 weeks. Chronic treatment with leptin for 4 weeks raised plasma
levels in B6 mice to that of A/J mice. Plasma leptin in B6 control mice
remained significantly lower than A/J mice through week 4. By week 8,
leptin levels in the B6 control group had risen and were similar to A/J
mice. Although there were significant weight differences between B6 treated
and B6 control groups for 2-3 weeks after pump implantation, these
differences were transient. Ultimately, there were no weight differences
between the B6 treated and B6 control groups. There were no differences in
plasma glucose between B6 treated and control groups. Plasma insulin values
were also not different between the 2 groups. There was no effect of leptin
supplementation on locomotor activity or food intake in B6 mice. In
summary, this study demonstrates that leptin supplementation in animals
that show low plasma leptin levels in response to fat feeding may slow but
does not prevent the subsequent development of diet-induced obesity.