The molecular genetics of diabetes mellitus

Importance of maternal history of non-insulin dependent diabetic patients

OBJECTIVE

To assess the family history of diabetes in non-insulin dependent diabetes mellitus with particular emphasis on parental phenotype.

DESIGN

Family histories were obtained from an existing computerised database and supplemented by postal questionnaires.

SETTING

Diabetic service of a provincial teaching hospital.

SUBJECTS

A total of 1326 patients with non-insulin dependent diabetes who had been referred to diabetic clinics over the past 10 years and from whom data had been collected for inclusion in the database, of whom 347 had affected first degree relatives. Nineteen non-white patients were excluded because of the differential hereditability of the disease, and 230 (70%) patients with an affected first degree relative responded to the postal questionnaire.

RESULTS

Mothers were implicated in significantly more cases than fathers in patients with a single affected parent: 125 mothers and 48 fathers from database; 82 mothers and 34 fathers from postal questionnaire; p less than 0.001 in both cases.

CONCLUSIONS

Maternal influences seem to have an important role in the inheritance of non-insulin dependent diabetes.

Similar frequencies of renin gene restriction fragment length polymorphisms in hypertensive and normotensive subjects

A prospective study was conducted to compare the frequency of renin gene polymorphisms in normotensive and hypertensive subjects. Hypertensive (n = 102, blood pressure 168 +/- 17/103 +/- 9 mm Hg) and normotensive (n = 120, blood pressure 122 +/- 10/75 +/- 9 mm Hg) subjects were white, had similar age and sex distributions (hypertensive group, 45 +/- 10 years old and 52% female; normotensive group, 44 +/- 9 years old and 55% female) and similar body mass index (hypertensive group, 23.2 +/- 2.6; normotensive group, 22.5 +/- 2.4 kg/m2, p = 0.048). The familial susceptibility to hypertension was defined as at least one parent and one sibling who were hypertensive before age 65; subjects in the normotensive group had no familial history of hypertension. Renin gene polymorphisms located throughout the renin gene were identified by using three restriction enzymes (Taq I, HinfI, HindIII). For each polymorphic restriction site, allele frequencies were similar in the hypertensive and the normotensive groups. In the absence of parental genotypes, the haplotype frequencies combining the three restriction fragment length polymorphisms were estimated by using maximum likelihood techniques and were similar in both groups (hypertensive group, 0.429, 0.277, and 0.177; normotensive group, 0.453, 0.245, and 0.195 for the three most common haplotypes). A rare haplotype detected by Taq I/Hind III was apparently more frequent in the hypertensive than in the normotensive group (hypertensive group, tH 0.086, th 0.022; normotensive group, tH 0.038, th 0.050), but the difference was not statistically significant. In conclusion, no association between renin gene polymorphisms and essential hypertension was demonstrated in the present study.