© JAPI • VOL. 54 • JUNE 2006 www.japi.org 441 * Molecular Biology Research Laboratory, Department of Zoology; ** Department of Statistics; *** Institute of Bioinformatics and Biotechology; University of Pune, Pune, India. Received : 16.8.2005; Accepted : 3.4.2006 Original Article Study of Inheritance of Diabetes Mellitus in Western Indian Population by Pedigree Analysis Sonali S Deo*, SD Gore** , DN Deobagkar*,*** , Deepti D Deobagkar*,*** Abstract Objectives : To study the inheritance pattern of diabetes mellitus in Western Indian population by analysing the pedigree of diabetes patients. Methods : 3,921 individuals from 300 families were interviewed for family history in this study, out of which 770 were diabetic individuals. Statistical analysis of the data was carried out using T-test and Chi-square test. Results : 37% cases of Type 1 DM and 58% cases of Type 2 DM showed family history of the disease. Of the cases showing family history for diabetes, 92% in case of Type 1 DM and 59% in case of Type 2 DM showed family history of Type 2 DM with a decrease in age of onset in the successive generations. Both the parents, when diabetic conferred equal risk of inheriting diabetes in offspring. The sex ratio of offspring suffering from diabetes was not influenced when only one of the parents was diabetic. However it was observed that the male offspring were highly susceptible when both parents were diabetic (Chi-square value=4.55 with 1 d.f.). The age of onset of diabetes did not show significant correlation with whether one or both the parents were diabetic. However, it was noteworthy that in case of familial history of diabetes there was a decrease in the age of onset in successive generations. Conclusion : This study suggests that family history of diabetes results in predisposition to early onset of the disease in successive generations and a cluster of genes involved in Type 2 DM may show a parental effect for predisposition to Type 1 DM in the offspring in this set of Indian population. © INTRODUCTION D iabetes mellitus is a multifactorial disease resulting from interaction of both genetic and environmental factors. 1,2 Type 2 DM is the commonest form of diabetes (90-95% of the diabetes population) resulting from insulin resistance combined with relative insulin deficiency. Type 1 DM is an autoimmune disease, which accounts for 5-10% of diabetic cases. In the year 2000, ~171 million people were estimated to be diabetic worldwide, which is projected to rise to 366 million in 2030 3 . India was estimated to have the highest number of diabetes cases in 2000 – 31.7 million and by 2030 it is estimated to rise to 79.4 million. 3 There is an increase in the percentage of population being exposed to diabetes in addition to the decrease in age of onset. It therefore becomes important to analyse the epidemiology of the disease. Diabetes is known to have a strong genetic component. There is a familial influence on the frequency of diabetes. 4 In Framingham population study maternal and paternal diabetes conferred equivalent risk for occurrence of Type 2 DM in offspring 5 while existence of excess of maternal transmission of Type 2 DM was observed in the analysis carried out in Northern California. 6 Familial clustering of diabetes and a significant maternal influence as well as a male sex-specific paternal effect was reported in a Chinese population study. 7 In this study we have examined a population in Maharashtra, India from the point of view of familial background and disease occurrence as well as pattern of inheritance of diabetes with respect to maternal or paternal transmission, age of onset etc. MATERIALS AND METHODS This study was carried out with the help of Diabetic Association of India, Pune branch. Diabetic patients diagnosed according to the WHO criteria 8 were interviewed for family history and age of onset of the disease, in addition to the study of medical records of the patients. Written consent was obtained from all the patients participating in the study. 3,921 individuals from 300 families were considered for this study, out of which 770 were diabetic individuals. Analysis of the pedigree data was carried out with help of previously