Significant relationships between the serum leptin concentration and the conventional fat reserve indices in a wildlife species, Hokkaido sika deer (Cervus nippon yesoensis)

Abstract

We assayed the serum leptin concentration and determined its correlation with the kidney fat mass (KFM), kidney fat index (KFI), and femur marrow fat (FMF) indices in 12 Hokkaido sika deer (Cervus nippon yesoensis Heude, 1884) collected in April, June, and October 2000. The KFM and KFI in April and June were both significantly lower than those in October. The leptin concentrations in April and June and in October were 1.222–1.521 ng mL^–1 HE (Human Equivalent) units and 1.676–2.63 ng mL^–1 HE, respectively, without overlapping. The relationships between the leptin concentration and the KFM, KFI, and FMF were all significant. Therefore, we conclude that the serum leptin concentration can be used as a new index for fat reserves in Hokkaido sika deer. However, reliable results could not be obtained from four samples collected in April and June when the deer were in a lower nutritional status. This may be due to the limited sensitivity of the antisera in the commercial multi-species leptin RIA kit used. For practical use in wildlife biology, species-specific leptin assays should be developed to eliminate this problem.