Case Control Study
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World J Diabetes. Aug 15, 2014; 5(4): 557-561
Published online Aug 15, 2014. doi: 10.4239/wjd.v5.i4.557
Study of factors influencing susceptibility and age at onset of type 1 diabetes: A review of data from Continental Italy and Sardinia
Fulvia Gloria-Bottini, Patrizia Saccucci, Gian Franco Meloni, Maria Luisa Manca-Bitti, Luca Coppeta, Anna Neri, Andrea Magrini, Bottini Egidio
Fulvia Gloria-Bottini, Patrizia Saccucci, Luca Coppeta, Anna Neri, Andrea Magrini, Bottini Egidio, Department of Biomedicine and Prevention, School of Medicine, University of Rome Tor Vergata, 00133 Rome, Italy
Gian Franco Meloni, Department of Pediatrics, University of Sassari Medical School, 07010 Sassari, Italy
Maria Luisa Manca-Bitti, Pediatric Diabetology and Endocrinology Unit, Policlinico Tor Vergata, University Hospital, 00144 Rome, Italy
Author contributions: Gloria-Bottini F, Meloni GF, Magrini A and Egidio B designed the study and contributed to write the manuscript; Saccucci P and Manca-Bitti ML performed the majority of experiments. Meloni GF, Coppeta L and Neri A provided the collection of human material and clinical data; Gloria-Bottini F and Egidio B performed statistical analyses; all authors read and approved the manuscript.
Correspondence to: Fulvia Gloria-Bottini, MD, Department of Biomedicine and Prevention, School of Medicine, University of Rome Tor Vergata, Via Montpellier, 1, 00133 Rome, Italy. gloria@med.uniroma2.it
Telephone: +39-06-30889514
Received: November 27, 2013
Revised: June 9, 2014
Accepted: June 20, 2014
Published online: August 15, 2014
Abstract

AIM: To investigate the role of protein tyrosin phosphatase 22 (PTPN22), maternal age at conception and sex on susceptibility and age at onset of type 1 diabetes (T1D) in Continental Italy and Sardinian populations.

METHODS: Three hundred seventy six subjects admitted consecutively to the hospital for T1D and 1032 healthy subjects as controls were studied in Continental Italy and 284 subjects admitted consecutively to the hospital for T1D and 5460 healthy newborns were studied in Sardinia. PTPN22 genotype was determined by DNA analysis. Maternal age at conception and age at onset of disease were obtained from clinical records. χ2 test of independence, student t test for differences between means and odds ratio analysis were carried out by SPSS programs. Three way contingency table analysis was carried out according to Sokal and Rohlf.

RESULTS: The pattern of association between PTPN22 and T1D is similar in Continental Italy and Sardinia: the proportion of *T allele carriers is 13.6% in T1D vs 6.7% in controls in Continental Italy while in Sardinia is 7.3% in T1D vs 4.4% in controls. The association between T1D and maternal age at conception is much stronger in Sardinia than in Italy: the proportion of newborn from mother aging more than 32 years is 89.3% in T1D vs 32.7% in consecutive newborn in Sardinia (P < 10-6) while in Continental Italy is 32.2% in T1D vs 19.1% in consecutive newborns (P = 0.005). This points to an important role of ethnicity. A slight prevalence of T1D males on T1D females is observed both in Continental Italy and Sardinia. PTPN22 genotype does not exert significant effect on the age at onset neither in Continental Italy nor and Sardinia. Maternal age does not influence significantly age at onset in Italy (8.2 years in T1D infants from mothers aging 32 years or less vs 7.89 years in T1D infants from mothers aging more than 32 years: P = 0.824) while in Sardinia a border line effect is observed (5.75 years in T1D infants from mothers aging 32 years or less vs 7.54 years in T1D infants from mothers aging more than 32 years: P = 0.062). No effect of sex on age at onset is observed in Continental Italy while in Sardinia female show a lower age at onset of T1D as compared to males (8.07 years in males vs 6.3 years in females: P = 0.002).

CONCLUSION: The present data confirm the importance of ethnicity on susceptibility and on the age at onset of T1D.

Keywords: Type 1 diabetes, Continental Italy, Sardinia, Protein tyrosin phosphatase 22, Maternal age, Age of onset, Sex

Core tip: It is known that the incidence of type 1 diabetes (T1D) is greater in Sardinian than in Italian population. Among the factors considered in this review maternal age only has shown a significant difference between the two populations. Although in both Sardinia and Continental Italy the proportion of mothers aging more than 32 years is higher in children with T1D than in consecutive newborns from the same population, the risk of having a child with T1D in younger women is much greater in Sardinia than in Continental Italy (OR = 17.191 vs 2.018).