Human leptin receptor gene in obese Japanese subjects: evidence against either obesity-causing mutations or association of sequence variants with obesity

Abstract

Leptin is an adipocyte-derived blood-borne satiety factor that acts on its cognate leptin receptor (Ob-R) in the hypothalamus, thereby regulating food intake and energy expenditure. To explore whether mutations in the Ob-R gene cause obesity in humans, we have searched for mutations in the gene for Ob-Rb, a biologically active receptor isoform, in obese Japanese subjects. We have also examined associations between such mutants and obesity in the Japanese. Genomic DNAs were used as templates in polymerase chain reaction (PCR) with primers selected to amplify exons 2 to 20 of the human Ob-Rb gene. Direct sequence analysis of the PCR products revealed 7 nucleotide sequence variants (Lys109Arg, Gln223Arg, Ser343Ser, Ser492Thr, Lys656Asn, Ala976Asp, and Pro1019Pro) in the Ob-Rb coding region from 17 obese Japanese subjects with a family history of obesity (BMI 39.3 +/- 8.4 kg/m2). No missense and nonsense mutations were found such as those in Zucker fatty (fa/fa) rats and Koletsky (fa[k]/ fa[k]) rats. Nucleotide substitutions occurred at relatively high frequencies at codons 109, 223, 976, and 1019 (79, 91, 100, and 85%, respectively). Allele frequency of each variant determined by PCR-RFLP and PCR-single strand conformation polymorphism analyses showed no significant differences between 47 obese (BMI 35.1 +/- 6.5 kg/m2) and 68 non-obese (BMI 21.6 +/- 2.2 kg/m2) subjects. The present study represents the first report of sequence variants of the Ob-Rb gene in the Japanese and provides evidence against either obesity-causing mutations or association of sequence variants with obesity in obese Japanese subjects.

Association of Trp64Arg polymorphism of the β3-adrenergic receptor gene and no association of Gln223Arg polymorphism of the leptin receptor gene in Japanese schoolchildren with obesity

“…Previous reports have suggested that allele frequency of the Arg223 of the Ob-R gene was higher in Japanese (0.838 ± 0.872) than in Caucasians (0.421 ± 0.440) and in Pima Indians (0.750). 29,30,33,51,52 These studies showed that allele frequency varies among ethnic groups and that the polymorphism is not associated with obesity. In this study, we observed an allele frequency similar to that reported by Matsuoka et al 30 Our data suggest that the Gln223Arg polymorphism of the Ob-R gene is not associated with obesity.…”

“…Several other polymorphisms have been found for the Ob-R gene. 30 Further studies are needed to determine association between the polymorphisms of the Ob-R gene and obesity.…”

“…27 This polymorphism is also common in Japanese. 30 However, it is not clear whether leptin activity is in¯uenced by this polymorphism.…”

Maternal leptin receptor gene variant Gln223Arg is not associated with variation in birth weight or maternal body mass index in UK and South Asian populations

“…PCR primers to amplify the Gln223Arg variant analysed have been reported. 13 PCR ampli®cation was performed, with an initial denaturation (94 C, 5 min) then 94 C, 30 s, annealing at 60 C, 30 s, extension at 72 C, 30 s for 35 cycles followed by an additional extension (72 C, 5 min) with 1.5 mM MgCl 2 . PCR products were digested with MspI (Promega) to detect the Arg variant, which creates an MspI restriction site and analysed by gel electrophoresis (2.5% agarose gel).…”

Linkages and associations between the leptin receptor (LEPR) gene and human body composition in the Québec Family Study

“…34 No signi®cant differences in allele frequencies between non-obese (BMI 21.6AE 2.2 kgam 2 ) and obese (BMI 35.1 AE 6.5 kgam 2 ) Japanese subjects were observed for the K109R, Q223R, A976D and P1019P polymorphisms. 35 No differences in allele or genotype distributions of the 45 bp insertionadeletion polymorphism in the 3 H -UTS region of LEPR were observed between normal weight and morbidly obese (BMI ! 40 kgam 2 ) subjects.…”