Type 2 diabetes mellitus (T2DM) is a metabolic disorder of multiple etiologies characterized by chronic
hyperglycemia with disturbances of fat and protein metabolism resulting from defects in insulin secretion,
insulin action or both, and mediated in large part by the alteration in adaptive immunity. This study aimed to
evaluate the role of programmed cell death protein – 1 (PD-1) gene polymorphism and serum level of soluble
PD-1 in development of T2DM in Iraqi patients. Forty-five T2DM patients were recruited for this study.
Other 45 apparently healthy subjects matched for age, gender and ethnic background for patients were also
included as control group. Blood samples were collected from each participant, and DNA was extracted from
leukocytes. The gene fragment corresponding the PD-1-538 G/A polymorphism was amplified with
conventional PCR using specific primers. The genotyping was performed through restriction fragment length
gene polymorphism (RFLP). Serum level of soluble PD-1 (sPD-1) was measured by enzyme linked immune
sorbent assay (ELISA). There was no significant association between different genotypes of PD-1-538 G/A
polymorphism. However, at allelic level, G allele was less frequent among patients than controls (28.89%
versus 44.44%) with a significant difference. The median concentration of sPD-1 in patients was 53.12 pg/ml
(range 18.24-312.89 pg/ml) compared to 63.83pg//ml (range 16.89-508.65 pg/ml) in controls with no
significant difference. Median levels of sPD-1 in patients carrying GG, GA and AA genotypes were 51.67
pg/ml (range 18.24-160.41 pg/mL), 52.77 pg/ml (range 19.32-154.18 pg/mL) and 220.97 pg/ml (range
129.05-312.89 pg/mL) respectively. The GG genotype carriers differed significantly from AA genotype
carriers, while there was no significant between AA genotype carriers and AG genotype carriers. These data
suggest that A allele of PD-1-538 G/A might be a risk factor for development of T2DM. The GG genotype of
this polymorphism associates with higher serum level of sPD-1 than other genotypes.
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