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Article: Alina Gavrila, Jean L. Chan, Lisa C. Miller, Kathleen Heist, Nikos Yiannakouris, and Christos S. Mantzoros Circulating melanin-concentrating hormone (MCH), agouti-related protein (AGRP), and alpha melanocyte-stimulating hormone (-MSH) levels in relation to body composition; alterations in response to food deprivation and recombinant human leptin administration J Clin Endocrinol Metab 2004; 0: jc.2004-1124v1 [Abstract]

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Letter re: Melanin-Concentrating Hormone and a RIA kit

Kazuhiro Takahashi   (19 December 2005)

Letter re: Melanin-Concentrating Hormone and a RIA kit 19 December 2005
Kazuhiro Takahashi, Professor Dept. of Analytical Medical Technology, Tohoku Univ. Sch. of Health Sci., Sendai 980-8575, Japan Send letter to journal: Re: Letter re: Melanin-Concentrating Hormone and a RIA kit ktaka-md{at}mail.tains.tohoku.ac.jp Kazuhiro Takahashi	I have read with great interest the recent Letter to the Editor (1) and Authors' Response (2) concerning Gavrila et al. paper regarding melanin-concentrating hormone (MCH) and energy balance (3). More than 10 years ago, we reported that MCH was undetectable in human or rat plasma by a RIA established in our laboratory, with a detection limit of 0.25 pmol/l, or 0.6 pg/ml (4). Consequently, the presence of MCH in human plasma at concentrations of 97.8 ± 22.8 pg/ml (mean ± SD) or about 20 pg/ml, as reported by Gavrila et al. (3), seems unlikely. Most of MCH-like immunoreactivity shown in plasma may well be a cross-reacting substance(s). The only way to demonstrate the presence of MCH in plasma or serum is to do reverse-phase high performance liquid chromatography (HPLC) or fast protein liquid chromatography (FPLC) coupled with RIA, which was not reported by the authors (3), and is not found online at http://www.phoenixpeptide.com/qcdata/RIK/QCK7047.html. Furthermore, the authors did not describe the serum extraction method, because one ml of unextracted plasma is unlikely to be measurable in one assay tube by RIA (3). The mean ± SD serum concentrations of MCH were 97.8 ± 22.8 pg/ml in the cross-sectional study, whereas serum MCH concentrations were about 20 pg/ml in the interventional studies (3). The authors did not explain such discrepant results in the Discussion. These concerns raise serious questions about the validation of data measured by commercial kits, particularly for novel peptide hormones such as MCH. I believe that the Journal of Clinical Endocrinology and Metabolism should not accept papers on novel peptide hormones in which the data developed from commercial kits are not validated by appropriate analyses, such as HPLC or FPLC. References 1. Waters SM, Krause JE 2005 Letter re: circulating melanin-concentrating hormone, agouti-related protein, and a-melanocyte-stimulating hormone levels in relation to body composition: alterations in response to food deprivation and recombinant human leptin administration. J Clin Endocrinol Metab 90:6337 2. Mantzoros C 2005 Authors' Response: circulating melanin-concentrating hormone, agouti-related protein, and a-melanocyte-stimulating hormone levels in relation to body composition: alterations in response to food deprivation and recombinant human leptin administration. J Clin Endocrinol Metab 90:6337 3. Gavrila A, Chan JL, Miller LC, Heist K, Yiannakouris N, Mantzoros CS 2005 Circulating melanin-concentrating hormone, agouti-related protein, and a-melanocyte-stimulating hormone levels in relation to body composition: alterations in response to food deprivation and recombinant human leptin administration. J Clin Endocrinol Metab 90:1047-1054 4. Takahashi K, Suzuki H, Totsune K, Murakami O, Satoh F, Sone M, Sasano H, Mouri T, Shibahara S 1995 Melanin-concentrating hormone in human and rat. Neuroendocrinology 61:493-498.