Association of polymorphisms in the leptin and leptin receptor genes with inflammatory mediators in patients with osteoporosis.

Bone mass and inflammation are implicated in the pathogenesis of osteoporosis. We hypothesized that leptin and leptin receptor gene might be associated with osteoporosis by activating the inflammatory pathway. Therefore, we analyzed polymorphisms of the leptin (gene symbol, LEP) and leptin receptor (gene symbol, LEPR) genes and determined their associations with proinflammatory cytokine levels in patients with osteoporosis. We assessed polymorphisms in LEP (-2548G > A) and LEPR (Lys109Arg, Gln223Arg, and Lys656Asn) and calculated odds ratios for the genotype and allele distributions between patients and controls. Serum leptin, soluble leptin receptor, interleukin (IL)-1, IL-6, IL-7, and tumor necrosis factor (TNF) levels were measured by enzyme-linked immunosorbent assays (ELISA) and were verified by in vitro lymphocyte proliferation assays and ELISAs. We found a higher frequency of the A allele for LEP at -2548 in patients with osteoporosis compared with the control group. The A allele was associated with differences in serum leptin, soluble leptin receptor, IL-1, IL-6, and TNF levels compared with the wild-type G allele (p < 0.05). The G allele in Lys109Arg and Gln223Arg was associated with increased risk of osteoporosis and with differences in serum leptin, soluble leptin receptor, IL-1, IL-6, and TNF levels compared with the wild-type A allele (p < 0.05). The Lys656Asn genotype was not associated with the risk of osteoporosis. In vitro lymphocyte proliferation assays and ELISAs confirmed these results. Polymorphisms in LEP and LEPR are associated with increased risk of osteoporosis, possibly by increasing the expression of proinflammatory cytokines.