Diabetes has a genetic susceptibility(Genetic factors)
A considerable number of epidemiological investigations have found that certain cases of diabetes occur with a certain genetic background. This means that diabetes is more likely to occur in individuals with genetic susceptibility. Foreign reports indicate that the prevalence of diabetes in relatives of diabetes patients is 4 to 10 times higher than in non-diabetes relatives, and the prevalence rate of diabetes in children of diabetic parents can reach up to 25%. In our country, a survey was conducted on the prevalence of diabetes in 100 first-degree relatives of diabetes patients, and the incidence rate of diabetes in relatives was 17 times higher than in non-diabetes individuals.
Research on the concordance of diabetes in twins has found that the concordance rate for twins with double-ovulation is 3% to 37%, while the rate for twins with single-ovulation is 45% to 96%, which is significantly higher than the former. The genetic makeup of twins with single-ovulation is completely identical, while only 50% of twins with double-ovulation are completely identical. Additionally, the study found that among twins with single-ovulation who develop type 1 diabetes before the age of 40, the concordance rate is only 50%, whereas the concordance rate for those who develop type 1 diabetes after the age of 40 is 95% to 100%.
This indicates that diabetes has a genetic tendency, but the specific genetic characteristics are still not fully understood. Currently, it is widely believed that the genetic tendency of diabetes is determined by “multifactor-multigen”. Genetics play a crucial role in the onset of both type 1 and type 2 diabetes, but environmental factors are relatively more important in the pathogenesis of type 1 diabetes. Only a few young patients with type 1 diabetes (MODY) have been confirmed to have autosomal dominant inheritance.
Diabetes has racial differences in incidence
The incidence of type 1 diabetes is significantly higher in white people in Europe and America than in regions such as China and Japan. For example, the incidence of type 1 diabetes in American children is 15.8/100,000, while in China it is only 0.7/100,000, indicating that white people are more susceptible to type 1 diabetes than yellow-skinned people. There are also racial differences in the incidence of type 1 diabetes. Among Americans, the prevalence of white people is 6% to 8%, while the prevalence of Indians (Pima) reaches 30% to 50%. These facts also support the relationship between diabetes and genetics.
Human leukocyte antigen and susceptibility to diabetes
Human leukocyte antigens, also known as tissue compatibility antigens (HLA), are the most important genetic structure known so far, and their gene distribution varies among races. Scientists have found that the HLA gene is located on the short arm of chromosome 6, containing four gene loci: A, B, C, and D/DR. Some of these loci are associated with the incidence of type 1 diabetes.
An increase in the frequency of certain gene loci may make individuals more susceptible to type 1 diabetes. For example, HLAB8, B15, DW3, DR3, DW4, DR3, DR4, DRW4, and A9 are susceptible to diabetes; while other loci, such as A11, B5, DR2, and DR5, have anti-diabetic properties. However, no relationship between HLA and the incidence of type 2 diabetes has been found until now. This is the cutting-edge field of diabetes research examining the relationship between diabetes and genetics, and it holds the promise of elucidating the detailed genetic basis of diabetes.
