Possible association of the TERT promoter polymorphisms rs2735940, rs7712562 and rs2853669 with diabetes mellitus in obese elderly Polish population: results from the national PolSenior study

One of the markers of aging is lymphocyte telomere length (LTL), which is affected by genetic constitution of the organism and environmental conditions, such as development and diseases, including diabetes. The relationship of the later seems to be bilateral. The enzyme responsible for the maintenance of telomere length is a subunit of telomerase—telomerase reverse transcriptase (TERT). The aims of the present study were to (1) determine the influence of the TERT promoter sequence SNP variants on relative telomere length (RTL) in an elderly Polish population and (2) explore the potential associations of the SNPs with the type 2 diabetes mellitus (T2DM) in the obese individuals. Two highly homogenous subgroups of PolSenior participants were investigated, the first constituted 70 relatively healthy respondents and the second 70 individuals with T2DM. Telomere length ratio (T/S value) was measured; 1.5 kb part upstream of the transcription start site of the TERT promoter was sequenced, and the frequencies of polymorphisms were calculated and compared against analysed data. Low-frequency SNPs were evaluated but excluded from further comparative analyses to RTL and glucose metabolism markers. No significant difference in telomere length was found between the two studied subgroups. Univariate statistical analyses showed only a weak association of environmental or genetic factors altering this marker of aging. Approximate frequency of four SNPs in TERT promoter sequence was assessed in Polish population aged 65–95 years, but three of them (rs2735940, rs7712562 and rs2853669) were selected for further analyses. The SNP selection was based on their minor allele frequencies in general population and on published data. The univariate analysis has revealed that carriers of CC SNP (rs2853669) have had the shortest RTL in the T2DM group. Multivariate analysis has also revealed that the genetic effect of TERT promoter CC SNP was strengthened by the incidence of T2DM. The additional variation in RTL in paired groups indicates that in addition to T2DM and genetics, there are other factors contributing to development of the age-related diseases.