Molecular scanning for mutations in the melanocortin‐4 receptor gene in obese/diabetic Japanese

Decreased function of the melanocortin‐4 receptor (MC4R) was reported to cause late‐onset obesity and insulin resistance in rodents. Thus mutations in the MC4R gene drew strong attention as a possible cause of obesity and diabetes. We screened for mutations in the MC4R gene in extremely obese [body mass index (BMI) ≥ 35 kg/m2] Japanese with diabetes by direct sequencing. A heterozygous mutation (V103I) was detected in one case (2.0 %), however the frequency was not significantly different from that in non‐obese (BMI ≤ 24 kg/m2) and non‐diabetic subjects (2.7 %). No other mutations were detected. These results suggest that mutations including V103I in the MC4R gene are not a major cause of obesity or diabetes in Japanese.