Lack of Association of the Trp64Arg Polymorphism of β<sub>3</sub>-Adrenergic Receptor Gene with Energy Expenditure in Response to Caffeine Among Young Healthy Women

Lack of Association of the Trp64Arg Polymorphism of β₃-Adrenergic Receptor Gene with Energy Expenditure in Response to Caffeine Among Young Healthy Women

TAKU HAMADA,¹ KAZUHIKO KOTANI,^1,2 AKANE HIGASHI,³ JUNKO IKEDA,⁴ EMI TAGAKI,³ AIKO IGARASHI,³ CHIKANOBU MATSUBARA,³ TOSHIHIDE YOSHIDA⁵ and NAOKI SAKANE¹

¹Division of Preventive Medicine and Diabetes Education, Clinical Research Institute for Endocrine and Metabolic Disease, National Hospital Organization Kyoto Medical Center, Kyoto, Japan
²Division of Health Administration and Promotion, Faculty of Medicine, Tottori University, Yonago, Japan
³Faculty of Human Environment, Kyoto Prefectural University, Kyoto, Japan
⁴Department of Home Economics, Kyoto Bunkyo Junior College, Tokyo, Japan
⁵Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan

A close relationship between coffee intake and certain metabolic disorders is known. Caffeine, one of coffee components, can increase energy expenditure (EE), but there are considerable individual differences in the caffeine effects on EE, and the causes have not been fully established in humans. The Arg allele in the β₃-adrenergic receptor gene (β₃-AR), a marker for obesity-related traits, may be a contributor to individual variations in EE. This study investigated the effect of the Arg allele of β₃-AR on caffeine-induced increases in EE. In 44 healthy young women (21 ± 1 years), physical characteristics, blood pressure, biochemical profiles and dietary nutritional intake were measured. A caffeine-loading test was conducted at a dosage of 4 mg per body weight (kg). EE was measured using an indirect open-circuit calorimeter for a 10-min period before, and at 30 min and 60 min after the caffeine-loading test. The β₃-AR Trp64Arg polymorphism was detected with a PCR-restriction fragment length polymorphism method. The frequency of the Arg allele was 24%. The distribution of the Trp/Trp, Trp/Arg, and Arg/Arg genotypes was 58%, 36%, and 6%, respectively. At the baseline, subjects with the Arg/Arg genotype had a significantly lower EE level than those with the Trp/Trp or Trp/Arg genotype. After the caffeine-loading test, there were caffeine-induced increases in EE in all genotypes, but there were no differences in the levels of increase among the genotypes. These findings suggest that the genotypes of β₃-AR Trp64Arg polymorphism might be not associated with caffeine-induced increases in EE levels.

keywords —— β₃-adrenergic receptor; polymorphism; caffeine; energy expenditure; genotype.

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Tohoku J. Exp. Med., 2008, 214, 365-370

Correspondence: Naoki Sakane, M.D., Division of Preventive Medicine and Diabetes Education, Clinical Research Institute for Endocrine and Metabolic Disease, National Hospital Organization Kyoto Medical Center, 1-1, Mukaihata-cho, Fusumi-ku, Kyoto 612-8555, Japan.

e-mail: nsakane@kyotolan.hosp.go.jp