Is There A Genetic Test For Diabetes

Genetic Linkage Studies On Type 2 Diabetes

Linkage is a genetic tendency where genetic markers are inherited together as a result of being near to one another on the same chromosome. Genetic linkage analysis, one of the old study approaches, focuses on genomic regions with large genetic effect that can influence the development of a disease . Genome-wide linkage scans have proved that some genes are associated with Type 2 diabetes on specific chromosomes such as 4q, 12q, and 22q in AA, 6p in EA, 2p in AI and 13q in African American , 3p at marker D3S2406 in Mexicans Americans and 2p and 13p of Chinese increase the risk of developing the disease. Linkage studies have been used to identify genes associated with different chronic disorders with unknown pathogenesis such as Type 2 diabetes, but they are considered to be unsuccessful by many researchers because they have only identified a few genes . Many studies, including one review reported that these studies were only successful in reviewing two genes associated with Type 2 diabetes although this differs from what was reported earlier where three more genes HNF4A, ENPP1, ADIPOQ were included .

Calculating Risk Of Type 2 Diabetes

As my family sat down to a carbohydrate-rich dinner of pasta, my famous pesto pizza rolls and a salad, I explained how this direct-to-consumer testing service was calculating the risk of this complex disease that is caused by the interaction of diet, environment and thousands of genes.

The piece of the puzzle that 23andMe is calculating is called the polygenic risk score, which is the likelihood we were born with of developing certain diseases or conditions.

Polygenic risk scores are not based on single genes or mutations. Instead, these calculations look at the cumulative effect of thousands of small variations scattered throughout our genomes. Not all variations cause harmful effects, some are beneficial and boost health, decreasing the odds of developing diabetes. Each one of these variations alone may not have a significant impact on our health, but together they add up to increased risk of developing certain types of disease. According to 23andMe, the polygenic risk score for Type 2 diabetes was based on research using the shared DNA of their consumers.

The DNA data the company is collecting is not just to report results back to the consumer some 2.5 million 23andMe customers have consented to allow the company to use their DNA for research. So can this polygenic risk score tell us our increased likelihood or susceptibility to developing diseases such as diabetes?

The short answer is yes.

Is There A Genetic Test For Type 1 Diabetes

Type 1 Diabetes is a chronic condition that impacts the ability of a personâs pancreas to create sufficient insulin. Without insulin, blood sugar canât get into the cells and stays in the bloodstream. Whether you have a family member with Type 1 Diabetes or youâre curious about what the latest science has to offer, letâs understand whatâs currently possible to detect through genetic testing.

Orchid offers advanced genetic testing for couples who want their child to have the best shot of a healthy life. âGenetics for Humansâ is where we unpack how genetics impacts our everyday lives and the latest tools to help you build a healthier family.

What is Type 1 Diabetes and how does it impact individuals?

âDiabetesâ is a term thrown around a lot, and what most people are referring to is Type 2 Diabetes, which often develops later in life. Type 1 Diabetes , however, typically impacts individuals in their early childhood to young adulthood years. It is thought to be an autoimmune disease in which the body attacks its pancreatic cells that produce insulin by mistake.

How common is Type 1 Diabetes?

In the United States, about 1.6 million people are living with T1D. Many individuals develop symptoms during childhood or adolescence. 64,000 Americans are newly diagnosed each year.

Is Type 1 Diabetes genetically inherited?

Evidence that there is a strong genetic component to T1D comes from studies of identical twins since they share 100% of their DNA.

Resources

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New Genetic Discoveries May Hold Clues To Predict Prevent Type 1 Diabetes

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The etiology of type 1 diabetes continues to be debated, although experts agree it is likely a mix of genetic and environmental causes. Today, more than 50 regions of the human genome are implicated in type 1 diabetes.

Within each region, researchers are identifying new genes, biological pathways and potential therapeutic targets for intervention, but a cure or a way to prevent progression to type 1 diabetes remains elusive.

At the same time, cases of type 1 diabetes are surging in the U.S. According to the CDCs National Diabetes Statistics Report released in February, the number of people diagnosed with type 1 diabetes rose by nearly 30% since 2017, with the greatest increases observed among minority children.

The big mystery in type 1 diabetes is, why does it happen?Louis H. Philipson, MD, PhD, FACP, professor of medicine, director of the Kovler Diabetes Center at the University of Chicago School of Medicine, and former president of medicine and science for the American Diabetes Association, told Endocrine Today. Is there an environmental cause or a genetic cause? Autoimmune diseases, as a group, tend to be not all that inheritable. That is sometimes a surprise to people.

Family diabetes history

Type 1 diabetes in twins can also develop at different times, Philipson said.

Improving prediction

Clues from monogenic diabetes

The Play Of Genes And Non

• Department of Nutrition and Food Hygiene, School of Public Health, China Medical University, Shenyang, China

Diabetes has been a disease of public health concern for a number of decades. It was in the 1930s when scientists made an interesting discovery that the disease is actually divided into two types as some patients were insensitive to insulin treatment then. Type 2 Diabetes which happens to be the non-insulin dependent one is the most common form of the disease and is caused by the interaction between genetic and non-genetic factors. Despite conflicting results, numerous studies have identified genetic and non-genetic factors associated with this common type of diabetes. This review has summarized literature on some genes and non-genetic factors which have been identified to be associated with Type 2 diabetes. It has sourced literature from PubMed, Web of Science and Medline without any limitation to regions, publication types, or languages. The paper has started with the introduction, the play of non-genetic factors, the impact of genes in general, and ended with the interaction between some genes and environmental factors.

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Identifying The Genes Responsible For Type 2 Diabetes

Studies of twins suggest that type 2 diabetes might be linked to genetics. These studies were complicated by the environmental influences that also affect type 2 diabetes risk.

To date, numerous mutations have been shown to affect type 2 diabetes risk. The contribution of each gene is generally small. However, each additional mutation you have seems to increase your risk.

In general, mutations in any gene involved in controlling glucose levels can increase your risk for type 2 diabetes. These include genes that control:

• the production of glucose
• the production and regulation of insulin
• how glucose levels are sensed in the body

Genes associated with type 2 diabetes risk include:

• TCF7L2, which affects insulin secretion and glucose production
• ABCC8, which helps regulate insulin
• CAPN10, which is associated with type 2 diabetes risk in Mexican Americans
• GLUT2, which helps move glucose into the pancreas
• GCGR, a glucagon hormone involved in glucose regulation

The interactions between genetics and the environment make it difficult to identify a definite cause of type 2 diabetes. However, that doesnt mean you cant reduce your risk through modifying your habits.

The Diabetes Intervention Accentuating Diet and Enhancing Metabolism study a large, 2020 randomized clinical trial of people with type 2 diabetes, suggests that weight loss and increased physical activity can prevent or reverse early type 2 diabetes.

An Interview With Dr Toni Pollin

Jeanette McCarthy, MPH, PhD

Diabetes is a chronic condition characterized by elevated levels of blood glucose and the inability to properly process food for use as energy. Diabetes is a heterogeneous disease, with several different types and a mostly complex genetic etiology.

Up to 4% of cases of diabetes are Mendelian , where a mutation in a single gene is sufficient to cause disease. These Mendelian subtypes include neonatal diabetes, maturity-onset diabetes of the young , and syndromic forms. Genetics also plays a role in Type 1 and 2 diabetes, the most common types of diabetes, but the etiology is polygenic, with variants in dozens of genes, each with a small effect, collectively increasing a persons risk of disease.

Genetic testing in diabetes is important because its estimated that 80% of patients with MODY are misdiagnosed as having Type 1 or 2 diabetes and would benefit from alternative treatments.

We sat down with Dr. Toni Pollin, an Associate Professor of Medicine and Epidemiology & Public Health from the University of Maryland School of Medicine to ask her about the benefits of genetic testing in diabetes patients.

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Genetic Prediction Models For Type 2 Diabetes: Evidence From Cross

Several studies have indicated that different genetic variants are associated with type 2 diabetes. Genetic risk models for type 2 diabetes, based on both cross-sectional and longitudinal studies, are summarized in .

Cross-sectional studies.

In cross-sectional studies including 3,0009,000 individuals with and without type 2 diabetes, the discriminatory ability of the combined SNP information has been assessed by grouping individuals based on the number of risk alleles and determining relative odds of type 2 diabetes, as well as by calculating the area under the receiver operating characteristic curve . As shown in , the AUC of the genetic risk score , which combines the information from all risk variants included in the study, has ranged from 0.54 to 0.63, indicating that genetic factors have limited use in predicting an individuals risk of the disease. In contrast, the AUC has been considerably larger for clinical models including different combinations of clinical and laboratory parameters predicting the risk of type 2 diabetes. Adding the GRS in the same model shows that in addition to clinical and laboratory parameters, risk variants increase only minimally the predictive value at the population level, although the model improvement could be statistically significant in some cases.

Longitudinal studies.

Genome Wide Association Studies On Type 2 Diabetes

Until the early 2000s, so many candidate genes and linkage studies have been done but only succeeded in identifying very few susceptibility loci and the coming of genome wide association studies which focuses on searching single nucleotide polymorphisms that happen more frequent in people having a certain disease brought an interesting twist and is thought to be a breakthrough concerning the genetic research on Type 2 diabetes . Genes such KLF14, ENPP1, ADAMTS9, ADIPOQ, IRS, GCKR, SREBF1, FTO HNF4A, NOTCH2, IGF2BP2, CDKAL1, JAZF1, SCL30A8, HHEX, TCF7L2, EXT2, FTO and many others have been identified by this approach. By 2009 GWAS had identified 19 more SNPs associated with the Type 2 diabetes and this number increased to more than 60 SNPs by 2016 in Asian and European ancestry alone with researchers not only identified the variants and the genes involved but also validated the effects conferred by these reported common variants in different populations as conferred impacts may differ or might be the same but with substantial differences in allele frequencies as it is the evident with Chinese and European populations on variants in IGF2BP2, CDKAL1, JAZF1, SCL30A8, HHEX, TCF7L2, EXT2, and FTO and Europeans and North African Arabs in variants in TCF7L2 and other genes which made it possible to conclude that biological actions and activities of common variants may be similar in different ethnic groups.

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Role Of Socioeconomic Status On Type 2 Diabetes

The public health of population groups links with socioeconomic status inextricably in different ways. SES is composed of many dimensions and is often measured by several index, such as income, education and occupation. SES has been recognized as an important determinate factor of population’s health in both industrialized and developing countries . And the association between SES and Type 2 diabetes, which depends on the stage of economic and social development, differs worldwide . The relationship between SES and Type 2 diabetes was positive several decades ago but is now negative in developed countries while in developing societies the relationship remains positive . What’s more, a systematic review from Wu et al. found that low education is probably associated with an increased prevalence of Type 2 diabetes in China . And education in men and the measure of income in both genders is positively related to self-reported and total diabetes prevalence and awareness of diabetes in a Chinese population aged 45 years or older . Also, a latest finding from Tang et al. found economic development, income and gender differences also played a critical role in Type 2 diabetes .

Are Genetic Prediction Models For Type 2 Diabetes Worthless

Both cross-sectional and longitudinal studies published thus far demonstrate that genetic screening for the prediction of type 2 diabetes in high-risk individuals is currently of little value in clinical practice. lists several limitations of GRSs published .

Small effect size of genetic loci.

Effect sizes of common genetic variants for type 2 diabetes identified to date are rather modest, ranging from 10 to 35% . An attempt to compose a GRS combining several genetic variants has shown only a 1012% increased risk of disease with increasing number of the risk alleles. In the Malmö Preventive Project study , the effect was approximately twofold increased when carriers of the highest and the lowest number of risk alleles were compared . Increasing the number of novel genetic variants up to 40 did not seem to largely improve the risk prediction . The observed modest effect sizes could be partially attributed to the fact that low frequency or rare variants have not yet been reported. Also, it is worth mentioning that the majority of the identified loci from GWAS are not, in fact, genes. The type 2 diabetesassociated loci represent an associated SNP, and there are still no data on whether the top associated signal represents the causal genemuch less the causal variant.

Low discriminative ability of the GRS.

Small added value of GRS compared with clinical risk factors.

Questionable clinical relevance of some genetic variants in disease prediction.

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Tests To Diagnose Diabetes

Blood Glucose Measurements. The diagnosis of diabetes is based on one of three methods of blood glucose measurement .1 Diabetes can be diagnosed if the patient has a fasting blood glucose level of 126 mg per dL or greater on two separate occasions. The limitations of this test include the need for an eight-hour fast before the blood draw, a 12 to 15 percent day-to-day variance in fasting blood glucose values, and a slightly lower sensitivity for predicting microvascular complications.15,16

Diagnostic Criteria for Diabetes Mellitus

Categories of increased risk

Information from reference 1.

Diagnostic Criteria for Diabetes Mellitus

Categories of increased risk

Information from reference 1.

More Information On Genetics

If you would like to learn more about the genetics of all forms of diabetes, the National Institutes of Health has published The Genetic Landscape of Diabetes. This free online book provides an overview of the current knowledge about the genetics of type 1 and type 2 diabetes, as well other less common forms of diabetes. The book is written for health care professionals and for people with diabetes interested in learning more about the disease.

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Diagnostic Criteria And Testing

• References

The 1997 ADA consensus guidelines lowered the blood glucose thresholds for the diagnosis of diabetes.5 This increased the number of patients diagnosed at an earlier stage, although no studies have demonstrated a reduction in long-term complications. Data suggest that as many as 5.7 million persons in the United States have undiagnosed diabetes.6 Table 1 compares specific diagnostic tests for diabetes.1114

Comparison of Diagnostic Tests for Diabetes

NPV = negative predictive value OGTT = oral glucose tolerance test PPV = positive predictive value.

*Calculated based on prevalence of 6 percent.

Based on 2009 rates.

Information from references 11 through 14.

Comparison of Diagnostic Tests for Diabetes

NPV = negative predictive value OGTT = oral glucose tolerance test PPV = positive predictive value.

*Calculated based on prevalence of 6 percent.

Based on 2009 rates.

Information from references 11 through 14.