Contributing Factors Of Type 2 Diabetes Mellitus

Associated Complications

A persistent hyperglycemic state can lead to serious damage in many parts of the body. As it is mentioned earlier that DM is one of the leading causes of cardiovascular disease (CVD), diabetic eye disease, and kidney disease. In this section, each of the complications will briefly be discussed. Cardiovascular disease is the major cause of morbidity and mortality in the USA. People with DM are 2-3 times more likely to have CVD than people without DM. Furthermore, patients with T2DM generally develop CVD 14. 6 years earlier, and with greater severity than patients without DM. Diabetic eye disease (DED) arises as a direct result of persistent hyperglycemia causing damage to the retinal capillaries, resulting in capillary leakage and capillary blockage. Among all other DEDs, diabetic retinopathy is most prevalent, and about 35% of the diabetic population suffer from it. Kidney disease, DM and hypertension are highly interconnected. T2DM is one of the major causes of renal failure which contributes to the progression of hypertension, however, hypertension often precedes chronic kidney disease and helps the development of kidney disease. A recent study claimed that renal failure causes approximately 10% of deaths in people with T2DM. In the USA, DM causes end-stage renal disease (ESRD) in approximately 44% of patients. Major Determinants of T2DMWith advancement in epidemiological research on T2DM, our understanding has also improved on a broad range of risk factors associated for the development of T2DM. The major determinants of T2DM consist of genetic predisposition, obesity, unhealthy diet, sedentary lifestyle, cigarette smoking, older age, psychosocial stress and depression, and some other lifestyle factors.

Genetic predisposition

Twin and family studies have provided substantial evidences of a genetic link with T2DM. During the last 10 years, T2DM genome-wide association studies have recognized more than 100 strong association signals, representing the complex polygenic nature of T2DM. These genetic associations have also revealed that these loci mostly affect T2DM risk by decreasing insulin secretion, and only a minority affect through reducing insulin action. Evidences from both observational studies and clinical trials suggest that lifestyle interventions influence the genetic effects on T2DM risk. On the other side, changes in genetic makeup might also stimulate the individual’s response to lifestyle factors.

Obesity

The prevalence of T2DM is rising simultaneously with the increase of obesity in most developed countries, like the USA, as well as in developing countries, for instance, China. However, treatment of obesity with weight loss surgery has justified effective in the prevention of T2DM. Likewise, during the early 1990s in Cuba due to an economic crisis, a significant decline in the incidence of DM was observed after a population-wide reduction of body weight. Ethnic variations have a profound impact on body weight and obesity, such as in the USA; people of Asian descent are 30-50% more susceptible to develop DM at a much lower body mass index (BMI) comparing to white people. It is because Asian people normally have a higher total body fat and visceral adiposity percentage at a given BMI than white people.

Diet and Lifestyle factors

Modification of diet and lifestyle is a crucial aspect of T2DM prevention. Leading clinical trials have presented that intensive lifestyle modifications can lower the risk of DM by 58% than control groups, and the trails have also demonstrated that these interventions are more effective than pharmacological treatments. Major clinical trials, for example, the Da Qing IGT and Diabetes Study in China and Diabetes Prevention Program in multi-ethnic Americans, have suggested that many incidences of T2DM could be prevented through increasing physical activity and adopting a healthy diet. A diet including high-quality fats and carbohydrates (low in trans fatty acids, high in polyunsaturated fatty acids and containing low glycemic index and glycemic load) is more important than low quality fats and carbohydrates to prevent T2DM. A diet containing high in refined grains, sugar-sweetened beverages, and red meat are directly associated with an increased risk of T2DM; conversely, diets enriched with whole grains, fruits, vegetables, nut and legumes reduce the risk of T2DM. Mediterranean diet is highly recommended to decrease the risk of T2DM.

A sedentary lifestyle is linked with a high risk of T2DM. On the other hand, evidence suggested that both aerobic exercise and resistance training independently exhibited positive effects on preventing T2DM. Spending more time on moderate to vigorous-intensity physical activity is beneficial for preventing insulin resistance.

Smoking

Smokers have higher chances to accumulate central fat than non-smokers, and smoking affects both insulin secretion and sensitivity. A meta-analysis revealed a dose-response relationship between the amount of smoking and threat of T2DM, and smokers were at 45% higher risk than non-smokers.