title: Radioimmunoassay for the detection of leptin in human serum.
abstract: Human leptin, which is encoded by the obese (ob) gene, is secreted specifically from adipocytes and is involved in the regulation of satiety and energy consumption. We developed a radioimmunoassay for the determination of leptin in human serum using polyclonal antibodies generated in rabbits against a C-terminal fragment of leptin, leptin(126-140), coupled to hemocyanin. The sensitivity of the assay was app. 5 pmol/l leptin(126-140) equivalent to 0.5 fmol/tube. The intra-assay variation at 100 pmol/l was less than 4.8% and the interassay variation less than 8.3%. Dilution curves of serum samples containing high levels of leptin(126-140) were parallel to the standard curve. Following G-50 Sephadex chromatography a single specific peak was detected at app. 16 kd. The assay procedure compared well to a commercially available assay (Linco, St. Louis, USA) using polyclonal antibodies directed against the intact recombinant protein (R = 0.96; p < 0.0001). Serum levels were significantly higher than plasma levels (app.20%) over a wide range of the standard curve. Levels of serum leptin126-140 immunoreactivity were not altered by meals and no day-to-day variation was found. In a group of 148 healthy female and 108 healthy male subjects with a BMI between 18.2 and 40 kg/m2 there was a significant difference between sexes with higher circulating serum levels in female than in male subjects when tested for identical BMI (p < 0.001). Serum leptin levels in both male and female subjects were positively related to BMI (p < 0.001) when analysed for lean and obese subjects whereas in lean subjects this relation was not apparent. No relation of serum leptin levels and age was detectable in subjects with a BMI up to 30 kg/m2. These data support an important role of leptin in the regulation of body fat stores and BMI which is modulated by gender specific factors.
authors.affiliation: Department of Clinical Endocrinology, Medizinische Hochschule Hannover, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Horn
authors.forename: R
authors.initials: R
authors.lastname: Geldszus
authors.forename: E
authors.initials: E
authors.lastname: Pötter
authors.forename: A
authors.initials: A
authors.lastname: von zur Mühlen
authors.forename: G
authors.initials: G
authors.lastname: Brabant
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002850:Chromatography, Gel; D005260:Female; D005615:Freezing; D006358:Hot Temperature; D006801:Humans; D020738:Leptin; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D010446:Peptide Fragments / Q000276:immunology; D011506:Proteins / Q000032:analysis* / Q000276:immunology; D011863:Radioimmunoassay / Q000379:methods*; D012016:Reference Values; D012680:Sensitivity and Specificity; D012727:Sex Characteristics
chemical_list: D020738:Leptin; D010446:Peptide Fragments; D011506:Proteins