Absence of Seasonal Variation in the Occurrence of IDDM. A study from southern India

Abstract

Lettersfor the mutation tended to have an earlier age of onset of NIDDM than those with other genotypes, as well as Pima Indians (3) and Finns (4). Although the reason for the discrepancy between these studies is unclear, differences in subjects examined or in the methodology may account for them; that is, the estimation of age at onset of NIDDM was the time of the first symptoms of NIDDM or the time of first detection of glucosuria by Fujisawa et al.(2), but it was not shown by Awata et al.(1). To clarify this point, we studied the frequency of this mutation by restrictionenzyme digestion with Mval (3,5), the age at onset of NIDDM based on the results of a 75-g oral glucose tolerance test with World Health Organization diagnostic criteria (6), the current BMI, and the maximal BMI in 368 Japanese NIDDM subjects (mean age 54.6 ± 9 . 1 years; BMI 22.2 ± 3.3 kg/m 2 ) and 200 nondiabetic subjects (mean age 48.3 ± 9.6 years; BMI 22.0 ± 1 . 5 kg/m 2 ). There was no significant difference between NIDDM subjects and nondiabetic subjects in the distribution of the Trp 64 /Trp 64 , Trp 64 /Arg 64 , and Arg 64 /Arg 64 genotypes (251, 100, and 17 in NIDDM patients vs. 137, 59, and 4 in nondiabetic subjects, respectively) or in the frequency of the Arg 64 allele (18% in NIDDM subjects vs. 17% in nondiabetic subjects) in agreement with the results of the previous studies (1,2,5). Among NIDDM subjects, those with the mutation had an earlier onset of NIDDM (mean ± SD: Trp 64 /Trp 64 ; 43.0 ± 9.4, Trp 64 /Arg 64 ; 40.3 ± 9.6 [P < 0.05]; Arg 64 /Arg b4 ; 36.9 ± 7.5 years [P < 0.01 vs. Trp /Trp 64 ]), and the homozygous patients had a higher maximal BMI compared with those without the mutation (27.6 ± 2.7 vs. 25.1 ± 4.2 kg/m 2 ; P < 0.05), although there were no differences in the current BMI (Trp 64 /Trp 64 ; 22.3 ± 4.0, Trp 64 /Arg 64 ; 22.7 ± 3.3, Arg 64 /Arg 64 ; 21.3 ± 1.3 kg/m 2 ). Our findings show that this mutation accelerates the onset of NIDDM in Japanese subjects, as well as the results of Fujisawa et al.(2). Second-generation Japanese-Americans (Nisei) are more prone to develop the insulin resistance syndrome and NIDDM compared with Americans and native Japanese (7). Although both genetic and environmental factors appear to influence the development of NIDDM, this mutation may explain susceptibility to NIDDM in Japanese-Americans. Among obese Japanese women, this mu-tation is associated with abdominal and visceral fat deposition (5), which may in turn result in insulin resistance and the earlier onset of NIDDM. Careful attention should be paid to the management of obesity in people with this mutation. Shuman WP, Stolov WC, Wahl PW: Prevalence of diabetes mellitus and impaired glucose tolerance among second-generation Japanese-American men.

Trends of seasonality and age of onset in T1DM: A snapshot from Eastern India

“…The onset of T1DM concerning “season of onset” was not significantly different from that reported by Ramachandran et al . [ 4 ] The study concluded that in tropical countries like India impact of seasonal variation is less marked. Incidentally, it has been reported that several births in India in autumn are higher than in another season.…”