Aims
Lower testosterone concentrations in older men are associated with poorer health outcomes, but underlying mechanisms, including possible links to the ageing process, remain unclear. We tested the hypothesis that testosterone treatment modulates leucocyte telomere length, a postulated marker of biological ageing, in overweight men with elevated blood glucose concentrations.
Methods
This was a pre-specified secondary analysis of Testosterone for the Prevention of Type 2 Diabetes Mellitus (T4DM), a randomised, placebo-controlled trial in 50-74-year-old men with waist circumference ≥95 cm and impaired glucose tolerance or newly diagnosed type 2 diabetes mellitus. Men received intramuscular testosterone undecanoate (1000 mg) every three months, or placebo, for two years with a background lifestyle program. Whole blood samples were collected at baseline and two years, and stored frozen at -80oC until retrieval for extraction of DNA and measurement of telomere length. Leucocyte telomere length was assayed by multiplex quantitative polymerase chain reaction and expressed as relative telomere length (rTL), a ratio of telomeric DNA to β-globin, a single-copy control gene (T/S ratio).
Results
Participants were 60±6 years-old (mean±SD), 38% had BMI 30-34.99 kg/m2 and 44% ≥35 kg/m2. Mean rTL at baseline was 1.63±0.27 in testosterone-treated men (N=375) and 1.61±0.28 in placebo-treated men (N=345). At two years, mean rTL were 1.61±0.28 and 1.58±0.29, respectively. Change in rTL after 2 years treatment was -0.02±0.15 in testosterone-treated, and -0.03±0.12 in placebo-treated men. Adjusting for baseline values there was no effect of testosterone treatment on rTL at two years (mean difference 0.01 [95% CI, -0.01 to 0.03], P=0.24). Results were similar for rTL change at two years from baseline.
Conclusion
These rTL results in overweight middle-aged to older men do not support the hypothesis that testosterone modulates biological ageing. Larger studies with longer treatment durations might provide further information.