**6. Genotype**

328 Type 1 Diabetes – Complications, Pathogenesis, and Alternative Treatments

Fig. 3. Ratio of males and females in relation to year of diagnosis (at 2-yr intervals).

concerned [34].

**Period at Diagnosis** 

Autumn and Winter months could support the hypothesis that infections may act as participating factors in the clinical onset of the disease, possibly accelerating an autoimmune process that may have been initiated months or years before [33]. Based on the average temperature record in our island, the newly diagnosed cased were grouped according to the month of diagnosis as follow: November, December, January, and February were defined as cold months, October, March, April and May as neutral months and, June, July , August and September, as warm months. More children were significantly diagnosed with T1DM during the cold months compared to those who manifested the disease during the warm months (p<0.001), whereas no difference was observed in the incidence between neutral and cold months ((p>0.05) throughout the study period (1990-2009) as depicted in Table 2. A recent study on seasonal variation in DM in 53 countries has suggested that seasonality in the diagnosis of T1DM occurs and that the pattern of seasonality appears to be related to the geographical position, at least as far as the northern/southern hemisphere dichotomy is

> **Month at Diagnosis Cold Months Neutral Months Warm Months n % n % n %**

> > 31.3)\*\*\*\*

*31.2)\*\*\*\** 

1990-1999 64 38.6 (31.2-46.0) 61 36.7 (29.4-44.0)\* 41 24.7 (18.1-

Table 2. Percentage of children diagnosed with T1DM at cold months, neutral months and warm months. Binomial test performed to compare proportions compared to "Cold

Months" group: \* NS (p>0.05), \*\* p<0.05, \*\*\* p<0.01, \*\*\*\*p<0.001

2000-2009 82 39.4 (32.8-46.0) 67 32.2 (25.9-38.5)\*\* 59 28.4 (22.3-34.5)\*\*\* *1990-2009 146 39.0 (34.1-43.9) 128 34.2 (29.4-39.0)\* 100 26.7 (22.2-* The genetics of T1DM cannot be classified according to a specific model of inheritance. Susceptibility to autoimmune T1DM is determined by multiple genes with HLA genes having the strongest known association. HLA antigens are present on the surface of the leucocytes and participate in some immune reactions. The genes coding for these antigens are located on chromosome 6. The class II sub region of HLA consists of the DR, DQ, and DP loci. These class II molecules are involved to the immune destruction of the pancreatic beta cells because they participate in the presentation of the antigen to the helper T cell, which initiates the immune reaction.

Inheritance of HLA-DR3 and HLA-DR4 appears to confer a 2 to 3 fold increased risk for the development of T1DM. When both HLA-DR3 and HLA-DR4 are inherited the relative risk for the development of T1DM is increased by 7-10 folds. It is estimated that 48 percent of the familial aggregation can now be ascribed to known loci, and the Major Histocompatibility Complex (MHC) contributes 41 percent [41]. As an example, siblings with the highest risk HLA DR and DQ alleles, who inherit both HLA regions identical by descent to their diabetic sibling, may have a risk of developing anti-islet autoimmunity as high as 80 percent and a similar long-term risk of diabetes[42]. Moreover HLA DR2 and HLA DR5 are both protective in most studies. Furthermore, stronger associations of DM1 have been reported with other MHC loci: HLA-DQA1 and DQB1 antigens[43].

In our effort to detect the genetic susceptibility of Greek Cypriot population to DM1, we studied 101 DM1 patients with age of onset less than 15 years through HLA serological typing for the DR and DQ1 alleles and compared them to 209 healthy controls. Our findings support the strong association of HLA-DR4 and DR3 with DM1. The most frequent allelic combination was that of HLA-DR3/DR4 (27%) followed by that of DR2/DR4 (21.6%). The percentage of HLA antigens in patients with DM1 and controls are shown in figure 4. The protective role of HLA-DR5 was shown, whereas the presence of HLA-DR2 is neutral, in contrast with most findings among Caucasian population where DR2 is protective. In addition, high resolution testing of the DR4 and DR3 alleles revealed the predominant presence of the DRB1\*0403 (0% vs 36%), similar frequency of the DRB1\*0402 in both groups (19% vs 14%) and that the DRB1\*301 was the only DR3 allele detected. The DQB1 alleles present in our T1DM patients as shown in figure 5 were nearly exclusively DQB1\*0201 and DQB1\*0302 [44]. The relative risk of developing T1DM in children carrying the DQB1\*0201 and the DQB1\*0302 alleles is 5.05 and 2.56 respectively whereas the protective role of DQB1\*0301 is documented.

Furthermore, although most T1D cases occur in individuals without a family history of the disease, T1D is strongly influenced by genetic factors. The lifelong risk of T1DM is markedly

Altering Trends in the Epidemiology of Type 1 Diabetes Mellitus in Children and Adolescents 331

and in association with the decreased age at onset of T1DM are consisted with a major

T1DM is associated with other autoimmune diseases such as thyroiditis, celiac disease, autoimmune gastritis and Addison disease [52]. The coexistence of these autoimmune

The variations in the incidence of T1DM in different countries its rising in rich and developed countries have raised questions about changes in environmental risk factors that may either initiate or accelerate the autoimmune process leading to pancreatic β-pancreatic

Reports have linked several environmental factors to an increased risk of T1DM; however, none of these have associations have verified and many have been contradicted by other studies. They include: viral infections in infancy and early childhood, maternal viral infection during pregnancy [53], early exposure to cow's milk and other nutritional factors [54], chemical contamination of food and water [55], high birth weight and an increase in

Viruses that have been associated with T1DM as environmental triggers include enteroviruses, mumps, rubella, cytomegalovirus, rotavirus and Epstein-Barr virus. The one proven environmental virus trigger T1DM is congenital rubella [57]. Many epidemiological studies have been supported the involvement of enteroviruses, especially the Coxsackie B viruses in the aetiology which appears to trigger β cell autoimmunity [58-59]. Furthermore it has been hypothesized that excessive weight gain and increase in insulin resistance in early childhood is trigger event which initiates the autoimmunity leading to β cell destruction and this Accelerator Hypothesis has been supported by several epidemiological studies [56, 60-61]. A number of dietary factors may influence the development of T1DM in infants at high risk for T1DM. Early introduction to the infant diet of cattle proteins, lack or short lasting breast feeding might be reasons for development of immunological reaction leading to the destruction of pancreatic beta cells [62]. In two large prospective cohort studies of newborns at high risk for T1DM diabetes (either a first degree relative [63-64] or a high risk HLA genotype) [63], first exposure to cereal before age three months [63-64] or after seven months [63] was associated with an increased risk of developing autoantibodies (IA) compared to infants whose first exposure was between ages four to six months. The increased risk was associated with gluten-containing cereals in one study [64], but with

On the other hand Vitamin D and omega-3 fatty acids may have a protective role. A case control study in seven European countries suggested that supplementation with vitamin D in early infancy can protect against development of T1DM [65]. A similar protective effect was found in a birth-cohort study of over 10,000 children [66]. Moreover preliminary studies in animals sustain a protective role of omega-3 fatty acids in the inflammatory

In conclusion there is no doubt that the incidence of T1DM is increasing dramatically. Data from large epidemiological studies worldwide indicate that the incidence of T1DM has been increasing by 2% to 5% worldwide [69] and this is of concern because of its health and resource implications. This rising incidence of T1DM in young children has been confirmed

environmental effect on the development of the disease [48-51].

diseases is associated to genes within the MHC complex [52].

either gluten or rice-containing cereals in the other [63].

reaction associated with autoimmune islet cell damage [67-68].

**7. Other risk factors** 

cell destruction.

body mass index [56].

Fig. 4. HLA antigens in DM1 patients and controls.

Fig. 5. HLA DQ B1 alleles in DM1 patients and controls.

increased in close relatives of a patient with T1DM, averaging about 6 percent in offspring, 5 percent in siblings and 50 percent in identical twins (versus 0.4 percent in subjects with no family history) [45-46]. T1DM is 2-3 times more common in the offspring of diabetic men (3.6-8.5%) compared with diabetic woman (1.3-3.6%) [1]. A monozygotic twin of a patient with type 1 diabetes has a higher risk of diabetes than a dizygotic twin, and the risk in a dizygotic twin sibling is similar to that in non-twin siblings [46].

Additionally age at onset is inversely related to the proportion of HLA haplotypes, and young children with T1DM show the greatest HLA-associated genetic risk. Siblings of children with onset of T1D before the age of 5 years have a 3- to 5-fold greater cumulative risk of diabetes by age 20 years compared with siblings of children diagnosed between 5 and 15 years of age [47]. Several reports suggest a higher proportion of lower risk haplotypes and in association with the decreased age at onset of T1DM are consisted with a major environmental effect on the development of the disease [48-51].

T1DM is associated with other autoimmune diseases such as thyroiditis, celiac disease, autoimmune gastritis and Addison disease [52]. The coexistence of these autoimmune diseases is associated to genes within the MHC complex [52].

#### **7. Other risk factors**

330 Type 1 Diabetes – Complications, Pathogenesis, and Alternative Treatments

Fig. 4. HLA antigens in DM1 patients and controls.

Fig. 5. HLA DQ B1 alleles in DM1 patients and controls.

dizygotic twin sibling is similar to that in non-twin siblings [46].

increased in close relatives of a patient with T1DM, averaging about 6 percent in offspring, 5 percent in siblings and 50 percent in identical twins (versus 0.4 percent in subjects with no family history) [45-46]. T1DM is 2-3 times more common in the offspring of diabetic men (3.6-8.5%) compared with diabetic woman (1.3-3.6%) [1]. A monozygotic twin of a patient with type 1 diabetes has a higher risk of diabetes than a dizygotic twin, and the risk in a

Additionally age at onset is inversely related to the proportion of HLA haplotypes, and young children with T1DM show the greatest HLA-associated genetic risk. Siblings of children with onset of T1D before the age of 5 years have a 3- to 5-fold greater cumulative risk of diabetes by age 20 years compared with siblings of children diagnosed between 5 and 15 years of age [47]. Several reports suggest a higher proportion of lower risk haplotypes The variations in the incidence of T1DM in different countries its rising in rich and developed countries have raised questions about changes in environmental risk factors that may either initiate or accelerate the autoimmune process leading to pancreatic β-pancreatic cell destruction.

Reports have linked several environmental factors to an increased risk of T1DM; however, none of these have associations have verified and many have been contradicted by other studies. They include: viral infections in infancy and early childhood, maternal viral infection during pregnancy [53], early exposure to cow's milk and other nutritional factors [54], chemical contamination of food and water [55], high birth weight and an increase in body mass index [56].

Viruses that have been associated with T1DM as environmental triggers include enteroviruses, mumps, rubella, cytomegalovirus, rotavirus and Epstein-Barr virus. The one proven environmental virus trigger T1DM is congenital rubella [57]. Many epidemiological studies have been supported the involvement of enteroviruses, especially the Coxsackie B viruses in the aetiology which appears to trigger β cell autoimmunity [58-59]. Furthermore it has been hypothesized that excessive weight gain and increase in insulin resistance in early childhood is trigger event which initiates the autoimmunity leading to β cell destruction and this Accelerator Hypothesis has been supported by several epidemiological studies [56, 60-61].

A number of dietary factors may influence the development of T1DM in infants at high risk for T1DM. Early introduction to the infant diet of cattle proteins, lack or short lasting breast feeding might be reasons for development of immunological reaction leading to the destruction of pancreatic beta cells [62]. In two large prospective cohort studies of newborns at high risk for T1DM diabetes (either a first degree relative [63-64] or a high risk HLA genotype) [63], first exposure to cereal before age three months [63-64] or after seven months [63] was associated with an increased risk of developing autoantibodies (IA) compared to infants whose first exposure was between ages four to six months. The increased risk was associated with gluten-containing cereals in one study [64], but with either gluten or rice-containing cereals in the other [63].

On the other hand Vitamin D and omega-3 fatty acids may have a protective role. A case control study in seven European countries suggested that supplementation with vitamin D in early infancy can protect against development of T1DM [65]. A similar protective effect was found in a birth-cohort study of over 10,000 children [66]. Moreover preliminary studies in animals sustain a protective role of omega-3 fatty acids in the inflammatory reaction associated with autoimmune islet cell damage [67-68].

In conclusion there is no doubt that the incidence of T1DM is increasing dramatically. Data from large epidemiological studies worldwide indicate that the incidence of T1DM has been increasing by 2% to 5% worldwide [69] and this is of concern because of its health and resource implications. This rising incidence of T1DM in young children has been confirmed

Altering Trends in the Epidemiology of Type 1 Diabetes Mellitus in Children and Adolescents 333

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to a genetically susceptible subgroup of the population (48). The heightened proportion of lower risk hapltotypes and decreased median age at onset of T1DM within the subgroup are consistent with a major environmental effect on Diabetes development (50).
