The study of different ethnic groups living in the same physical environment provides the opportunity to examine interaction of genetic and environmental factors in the aetiology of diabetes mellitus. In rural New Caledonia, the prevalence of diabetes was higher in part-Polynesians than in Melanesians: males - 6.6 versus 0.5%; females - 6.3 versus 3.5% respectively. The prevalence of abnormal glucose tolerance (impaired glucose tolerance and diabetes) was 11.5 and 15.7% in part-Polynesian males and females, respectively, and 4.7 and 9.2% in Melanesian males and females. Mean age and degree of obesity in these ethnic groups were sufficiently similar to suggest that these factors played no significant role in the difference in diabetes prevalence. Furthermore, adjustment of relative risk of impaired glucose tolerance and diabetes for age and obesity indicated that the modest differences between groups were not responsible for the observed variation in diabetes prevalence. The differences in prevalence of impaired glucose tolerance and diabetes between Melanesians and part-Polynesians may be genetically determined, although the role of certain environmental factors other than obesity, e.g. differences in physical activity or qualitative aspects of diet, cannot be excluded.
HLA antigen distributions in persons with normal and abnormal glucose tolerance were compared in four Pacific populations. The populations included Melanesians from the Fijian Islands, Loyalty Islands and mainland New Caledonia and Polynesians from the Wallis Islands. HLA-DR results are provided for the first time for Pacific groups. In Polynesians, HLA-B22 was increased in frequency in patients with non-insulin-dependent diabetes mellitus and also in persons with impaired glucose tolerance. However, the association was not statistically significant when corrected for the number of antigens tested. A similar increase in HLA-B22, although not significant, was seen in each of the three Melanesian populations with abnormal glucose tolerance. No other consistent increase in any HLA antigen occurred in persons with abnormal plasma glucose concentrations.
The prevalence of diabetes mellitus in the traditional-living population of Wallis Island was low and comparable with that found in other rural Polynesian societies. The diabetes prevalence was 1.9% in men and 3.5% in women; impaired glucose tolerance occurred in 5.0% of men and 8.4% of women. The prevalence of obesity was significantly greater in women than in men (37.4% versus 12%, respectively, were equal to or greater than 140% ideal weight). Subjects with diabetes tended to be more obese and less active than normal subjects, but these differences, although appreciable, were not usually statistically significant. The population engages in considerable physical activity, and this, along with the traditional diet, may be responsible for the relatively low diabetes prevalence.
Chronic treatment of rats with the naturally occurring androgen, testosterone, leads to hypertension and cardiovascular disease. This effect is believed to be mediated through the adrenal gland and in particular by action on the steroid 11/J-hydroxylase enzyme system. To study the possible mechanism of this effect, the enzyme system was examined at several time periods up to the time that hypertension develops. Rats were treated with testosterone (10 mg/day) for 3, 7, 21, and 42 days. Levels of cytochrome P-450 up enzyme and messenger RNA (mRNA) were determined as well as 11/3-hydroxylase enzyme activity. A significant decrease in enzyme activity was observed after 3 days of treatment This correlates with a profound decrease in the level of cytochrome P-450 U p enzyme as determined by Western blot analysis. A large decrease in cytochrome P-450 n p mRNA was also observed after 3 days of treatment All three parameters remained low throughout the treatment period. The decrease in 11/Jhydroxylase enzyme activity appears to result from a lower enzyme level brought about by decreased concentrations of mRNA transcripts. (Hypertension 1991;18:523-528)
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