Human skeletalmuscle expresses leptin receptor mRNA; however, it remains un-known whether leptin receptors (OB-R) are also expressed at theprotein level. Fourteen healthy men (age 33.1 2.0 yr, height 175.9 1.7 cm, body mass 81.2 3.8 kg, body fat 22.5 1.9%; means SE) participated in this investigation. The expressionof OB-R protein was determined in skeletal muscle, subcutaneousadipose tissue, and hypothalamus using a polyclonal rabbit anti-human leptin receptor. Three bands with a molecular mass close to170, 128, and 98 kDa were identified by Western blot with theanti-OB-R antibody. All three bands were identified in skeletal muscle:the 98-kDa and 170-kDa bands were detected in hypothalamus, and the98-kDa and 128-kDa bands were detected in thigh subcutaneous adiposetissue. The 128-kDa isoform was not detected in four subjects,whereas in the rest its occurrence was fully explained by the presenceof intermuscular adipose tissue, as demonstrated using an anti-perili-pin A antibody. No relationship was observed between the basalconcentration of leptin in serum and the 170-kDa band density. Inconclusion, a long isoform of the leptin receptor with a molecularmass close to 170 kDa is expressed at the protein level in humanskeletal muscle. The amount of 170-kDa protein appears to beindependent of the basal concentration of leptin in serum.
