One of the causes of diabetes: Genetic factors

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.

One of the causes of diabetes: Genetic factors
One of the causes of diabetes: Genetic factors

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.

The disparity in the incidence of type 1 diabetes (T1D) between Western countries and China can be attributed to a variety of factors, including genetic predisposition, environmental triggers, and healthcare access. A number of authoritative studies have explored these factors in depth.

One such study, published in the journal “Diabetes Care” in 2017, titled “Global Trends in the Incidence of Type 1 Diabetes in Children: A Global Collaborative Study of Childhood Type 1 Diabetes” by Patterson et al., highlighted that the incidence of T1D is significantly higher in Western countries compared to many Asian countries, including China. The study analyzed data from 200 registries across 5 continents and found that the incidence rates were highest in Europe and North America, with a lower incidence in Asia.

Another study, published in “The Lancet Diabetes & Endocrinology” in 2018, titled “Changing incidence of type 1 diabetes in Chinese children: a nationwide study from 1998 to 2012” by Yang et al., reported that while the incidence of T1D in Chinese children has been increasing, it remains lower than in Western countries. The study suggested that genetic factors, which are more prevalent in Western populations, play a significant role in the higher incidence of T1D in those regions.

Environmental factors, such as exposure to certain viruses or dietary patterns, have also been proposed as potential contributors to the higher incidence of T1D in Western countries. A review article in “Nature Reviews Endocrinology” in 2015, titled “Environmental factors in type 1 diabetes” by Ziegler et al., discussed how environmental exposures in early life could influence the development of T1D, and these factors may differ between Western and Asian populations.

Furthermore, the availability and quality of healthcare services, including early diagnosis and access to specialized care, can influence the reported incidence of T1D. Western countries generally have more robust healthcare systems that facilitate early detection and reporting of T1D cases.

In summary, the higher incidence of type 1 diabetes in Western countries compared to China is likely due to a combination of genetic susceptibility, differing environmental exposures, and healthcare system capabilities. These factors contribute to the observed differences in disease prevalence across different geographical regions.

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.

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