Plasma leptin concentrations in lean and obese human subjects and Prader-Willi syndrome: Comparison of RIA and ELISA methods

Abstract

Immunoassays for circulating leptin are important research tools for examining the role and regulation of leptin expression in human obesity. However, uncertainty exists regarding the comparability between studies of reported plasma or serum leptin concentrations. The purpose of the present study was to directly compare plasma leptin concentrations by using two of the most widely reported immunoassay methods-namely, a commercially available radioimmunoassay (RIA) and a proprietary enzyme-linked immunosorbent assay (ELISA). Plasma leptin concentrations were measured in healthy lean and obese volunteers and in patients with Prader-Willi syndrome (PWS). Over a wide range of plasma concentrations (2 to 70 ng/mL), leptin measurements obtained with the RIA and ELISA methods were highly correlated (r = 0.957, P<.0001) and were essentially indistinguishable. Leptin levels measured by RIA and ELISA were highly correlated with body mass index (BMI) overall (r = 0.784, P<.0001 and r = 0.732, P<.0001, respectively) and in the lean and obese subgroups. When compared with the results in the lean individuals (mean +/- SEM, 11.6+/-3.2 ng/mL), plasma leptin was significantly higher in both the obese (35.5+/-4.0 ng/mL, P<.0001) and the PWS subjects (30.7+/-6.9 ng/mL, P<.05). However, after we controlled for differences in BMI, the leptin levels were similar in all three groups. In conclusion, we found that the RIA and ELISA used in the present study yield plasma leptin concentrations that are essentially indistinguishable. Our findings should facilitate comparisons of leptin levels measured by these two widely used immunoassays in previous and future studies that examine the role of leptin in body weight regulation.

A meta-analysis of leptin reference ranges in the healthy paediatric prepubertal population

“…The ELISA methodology resulted in wider study leptin concentration ranges, higher means and greater deviations. This is in contrast to the study by Carlson et al 49 [6] yr, BMI ¼ 28 [4], n ¼ 4) participants. Plasma leptin concentrations for all participants were not significantly different when comparing the RIA and ELISA methodologies (25.9 [15.9] ng/mL and 24.7 [16.9] ng/ml, respectively) and the two methodologies were highly correlated (r ¼ 0.957, P , 0.0001).…”

“…49 A larger sample size, as found in this meta-analysis, enables for narrower confidence intervals and provides a more powerful clinical applicability of the results. In addition, Carlson et al 49 did not clarify if the EDTA-anticoagulant tubes were tested for any crossreactivity with leptin or if the EDTA interfered with the specificity of the antibody. Although the present meta-analysis only had two ELISA studies, the overall participant sample size (n ¼ 322) is large and should not be discounted.…”

“…Plasma leptin concentrations for all participants were not significantly different when comparing the RIA and ELISA methodologies (25.9 [15.9] ng/mL and 24.7 [16.9] ng/ml, respectively) and the two methodologies were highly correlated (r ¼ 0.957, P , 0.0001). This study by Carlson et al 49 had a small sample size, which could play a significant role when comparing the ELISA vs. RIA results relative to the current meta-analysis. 49 A larger sample size, as found in this meta-analysis, enables for narrower confidence intervals and provides a more powerful clinical applicability of the results.…”

“…This study by Carlson et al 49 had a small sample size, which could play a significant role when comparing the ELISA vs. RIA results relative to the current meta-analysis. 49 A larger sample size, as found in this meta-analysis, enables for narrower confidence intervals and provides a more powerful clinical applicability of the results. In addition, Carlson et al 49 did not clarify if the EDTA-anticoagulant tubes were tested for any crossreactivity with leptin or if the EDTA interfered with the specificity of the antibody.…”

Adipocyte, Adipose Tissue, and Infectious Disease

“…During malnutrition or starvation, circulating leptin levels decline and serve as a signal to the host to conserve energy by reducing energy metabolism (3). Although leptin has been more strongly associated with an increase in metabolic rate and reduction of adipose mass by suppressing appetite and stimulating the sympathetic nervous system (16,17,22,23), it is also implicated in negative feedback of the hypothalamic-pituitary-adrenal axis. Leptin receptors are found in the central nervous system and in peripheral tissues.…”