In type 1, the risk factors that may lead to diabetes are not completely clear. However, there are several risk factors that may enhance the development of type 1 diabetes (T1D). People with the genetic marker are more susceptible to diabetes. That gene is located on chromosome 6, and it’s an HLA (human leukocyte antigen) complex. Various HLA complex have been linked to type 1. Individuals who have one or more of those genes are more likely to develop T1D.The prime T1D susceptibility locus maps to HLA class II alleles, but recently it has been found that HLA class I also affect the possibility for T1D.
People with family history of diabetes are at higher risk for T1D. Although more than 85% of patients with T1D showed a negative family history for the disease, individuals with the HLA-risk who have family history of TD1 have a 1 in 5 risk for developing the disease while individuals with the same HLA-risk but no family history have nearly a 1 in 20. Having a family member with T1D increases the chances for having T1D. If both parents have the disease, that increases the risk than if just one parent has diabetes.
Studies have reported that certain viral infections may play a role in the development of T1D. A number of viruses have been connected to T1D, promoting autoimmune response which cause the immune system to attack the body’s health cells. Viruses that are believed to lead to type 1 includes enteroviruses such as coxsackievirus B (CVB), also rotavirus, mumps virus, and cytomegalovirus.
center0Figure 4: Interplay between virus- and host-intrinsic properties dictates whether enhancement or abrogation of type 1 diabetes occurs. ? = ? cells. Teff, effector (autoreactive) T-cells.
00Figure 4: Interplay between virus- and host-intrinsic properties dictates whether enhancement or abrogation of type 1 diabetes occurs. ? = ? cells. Teff, effector (autoreactive) T-cells.
Dietary factors have been explored as a risk factor for T1D. Researches shows that early introduction to cows’ milk during childhood is associated with both an increased risk of islet autoimmunity, and T1D. A higher consumption of cows’ milk may enhance the progression to T1D, and this is due to the presence of certain fatty acids in the cows’ milk such as myristic, penta-decanoic, monounsaturated palmitoleic acid isomers 16:1 omega-7 and 16:1 omega-9, and conjugated linoleic acid. Also the early (before 4 months) or late (after 7 months) dietary introduction of cereal and gluten might be associated with an increased risk of islet autoimmunity. This association may be as a result of immature immune and digestive systems.
Some studies show that children with low blood levels of vitamin D are more likely to have T1D than those with higher levels. Vitamin D has an important role in the regulation of the immune system and metabolic pathways relevant to diabetes. For the past years, there has been controversy about whether vitamin D deficiency increases the risk for having diabetes or not, and so Further studies are needed. Having other autoimmune disorders as Graves’ disease, multiple sclerosis, and pernicious anemia may also increase the risk for type 1.
In type 2, many factors have been found to increase the individual’s probability for developing type 2 diabetes (T2D). This includes genetic, environmental, and behavioral agents. It is believed that T2D is related to genetic component (table 1). Some studies among twins have shown higher rates in monozygotic than dizygotic twins. Having a genetic susceptibility increases the risk greatly, and so having a family member with type 2 also increases the possibility for T2D.40%of Individuals with first degree relatives of T2D have the chance for developing the disease.
8128008255Table 1 : some important susceptibility loci linked to T2D explored by genome-wide association studies (GWAS) in in different countries since 2007
00Table 1 : some important susceptibility loci linked to T2D explored by genome-wide association studies (GWAS) in in different countries since 2007
Prospective studies have mostly identified age as a strong risk factor for T2D. According to NHANES data, the incidence for T2D increases with ageing (Figure 1). In most communities, the susceptibility is low before age 30 while in older age the chance increases rapidly. Scientists assumes that as we age the pancreas does not pump enough insulin comparing with younger age, as well as the body’s cells become more resistant to insulin.
center671Figure 1: Median Age at Diagnosis of Diabetes Among Adult Incident Cases, (Data are self-reported from adults age 18–79 years). by Race/Ethnicity, U.S., 1997–2011
00Figure 1: Median Age at Diagnosis of Diabetes Among Adult Incident Cases, (Data are self-reported from adults age 18–79 years). by Race/Ethnicity, U.S., 1997–2011
Obesity and high fat distribution are the largest risk factor for T2D. That is because fat increases insulin resistance by interfering with the body’s cells ability to use insulin. Studies have reported that the longer the duration of having high body weight the higher the susceptibility for T2D. In most countries, the number of obese children has raised, and thus, the number of children with T2D has also increased.
Another large lifestyle risk factor is nutrition. Researchers have theorized that, diet with low fiber contents, too much of simple carbohydrate, and high fat intake increases the risk for T2D. Specific fatty acids contribute directly to diabetes by stimulating insulin resistance, and indirectly by leading to obesity. Sugar-Sweetened Beverages such as soft drinks and energy drinks. Studies have found high fiber diet with low average glycemic index may reduce the risk for diabetes. In addition to, alcohol consumption and smoking. Although the underlying mechanism of smoking in influencing T2D is not clear, it has been reported increasing incidence in active smokers compared with non-smokers.
Physical inactivity and sedentary lifestyle are a risk factors for type 2. It has been observed that doing regular exercises reduce the risk for the disease. This is because muscles cells have more insulin receptor than fat cells, and thus, enhance decreasing insulin resistance.
People with high blood pressure and high cholesterol levels are at higher risk for diabetes. These two components are key components in the metabolic syndrome, a cluster, or co-occurrence of conditions include obesity (usually around the waist circumference), high fasting glucose, hypertension, high triglycerides, or low HDL cholesterol levels. The metabolic syndrome is strongly linked to insulin resistance and so increase the probability for T2D.
center117786Figure 2: Pathophysiology of metabolic syndrome
00Figure 2: Pathophysiology of metabolic syndrome
Being in “prediabetic” state is a risk factor for developing T2D, which means glycemic levels in the blood are higher than normal but not enough to be diagnosed as diabetes. Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are “prediabetes” states. IFG means that during fasting person’s blood surge level is between 100 mg/dL and 125 mg/dL while IGT defined as glucose 2 hours after a standard 75 g oral glucose tolerance test (OGTT) between 140 mg/dL and 199 mg/dL. Unfortunately, it has been reported that many people are not aware of their prediabetes status.
One of the important risk factors is gestational diabetes mellitus. About 4% of all pregnant women get gestational diabetes. Studies show that women who develop gestational diabetes during their pregnancy are at a greater risk for diabetes. This is because during pregnancy the hormones from the placenta increases the mother’s insulin resistance. The progression for T2D is noticeably increased within the first five years after giving birth and then appears to level off.
Low birth weight ;2500 g or high birth weight ;4000 g was associated with increased risk of diabetes. A low birth weight due to undernutrition during pregnancy could lead to structural and physiological adaptations and higher future risk for T2D. Similarly, high birth weight due to overnutrition is also biologically plausible.
The fetus in the environment of maternal diabetes is exposed to high levels of glucose as it travels freely through the placenta to the fetus. In turn to elevated glucose the fetus will increase its own production of insulin which may lead to excessive birth weight known as macrosomia, and may develop glucose intolerance in later years (Figure 3).
center2813446Figure 3: Maternal Diabetes and Perinatal Programming
00Figure 3: Maternal Diabetes and Perinatal Programming
Other factors may influence the possibility for T2D are demographic risk factors such as sex, race, and ethnicity. In addition to other behavioral and lifestyle factors such as socioeconomic status, obstructive sleep apnea, depression, and antidepressant medications. Furthermore, some diseases may lead to diabetes like polycystic ovary syndrome (PCOS). It is a condition in which woman’s ovaries or adrenal glands produce more male hormones than normal. 70 % of women with PCOS have insulin resistance and so increases the risk for diabetes.