Postnatal surge of adipose-secreted leptin is a robust predictor of fat mass trajectory in mice.

The transient postnatal increase in circulating leptin levels, known as leptin surge, may increase later susceptibility to diet-induced obesity in rodents. However, the source of leptin during the surge needs to be better characterized, and the long-term effects of leptin are contradictory. Characterization of the interaction of leptin with the genetic background, sex, and other factors is required. Here, we focused on the impact of circulating leptin levels and several related variables, measured in 2- and 4-week-old (i) obesity-prone C57BL/6 (B6) and (ii) obesity-resistant A/J mice. In total, 264 mice of both sexes were used. Posttranscriptionally controlled leptin secretion from subcutaneous white adipose tissue, the largest adipose tissue depot in mice pups, was the primary determinant of plasma leptin levels. When the animals were randomly assigned standard chow or high-fat diet (HFD) between 12 - 24 weeks of age, the obesogenic effect of HFD-feeding was observed in B6 but not A/J mice. Only leptin levels at 2 weeks, i.e., close to the maximum in the postnatal leptin surge, correlated with both body weight (BW) trajectory throughout the life and adiposity of the 24-week-old mice. Leptin surge explained 13 and 7 % of the variance in BW and adiposity of B6 mice and 9 and 35 % of the variance in these parameters in A/J mice, with a minor role of sex. Our results prove the positive correlation between the leptin surge and adiposity in adulthood, reflecting the fundamental biological role of leptin. This role could be compromised in obese subjects.