MOLECULAR SCREENING OF UNCOUPLING PROTEIN-2 GENE IN PATIENTS WITH NONINSULIN-DEPENDENT DIABETES-MELLITUS OR OBESITY

Uncoupling protein 2 (UCP2), a member of the family of mitochondrial c arrier proteins, has been implicated in the control of whole-body ener gy balance. The coding region of the human UCP2 gene has now been show n to comprise six exons, and the sequences of the exon-intron boundari es were determined. With the use of this sequence information, 25 Japa nese patients with obesity and noninsulin-dependent diabetes mellitus (NIDDM) and 25 subjects with simple obesity were screened for mutation s in the entire coding region of UCP2 by PCR and single-strand conform ation polymorphism analysis. Two nucleotide polymorphisms resulting in Ala55 --> Val and Ala232 --> Thr substitutions were detected. With th e use of PCR and restriction fragment length polymorphism analysis, th e allele frequencies for each of these polymorphisms were determined i n 210 Japanese patients with NIDDM, 42 obese individuals, and 218 norm al control subjects. The frequency of the Val55 allele did not differ significantly among the NIDDM group (46.0%), the obesity group (48.8%) , and the normal control group (48.4%). The Thr232 allele was detected in only three subjects, who were heterozygotes and in the NIDDM group (allele frequency, 0.7%). However, expression in yeast;of the human w ild-type UCP2 protein and UCP2 containing Thr232 revealed no differenc e in functional activity. These results indicate that the Ala55 --> Va l and Ala232 --> Thr variants of UCP2 do not play an important role in the pathogenesis of NIDDM or obesity in the Japanese population.