Does Methadone Affect TERT Expression and Telomere Length?

Telomeres are repetitive DNA sequences at the ends of linear eukaryotic chromosomes. In humans, they consist of TTAGGG repeats. Telomere length is an important biomarker of cellular aging and is also associated with disease risk and life expectancy.^{1, 2, 3, 4, 5} Although many factors can affect telomere length, genetic factors play a major role.⁶

Many studies have shown that telomere length is shorter in people who use drugs, particularly heroin, than in the general population.^{7, 8} This shorter telomere length is associated with a higher risk of age-related diseases and premature death among people who use heroin and other opioids.^{9, 10, 11, 12} Because many of these patients receive methadone for detoxification or maintenance therapy, an important question arises: Is telomere shortening caused by direct exposure to heroin (morphine), or could methadone used during treatment also play a role in this process?

To address this question, a small preliminary experiment was conducted using the human SH-SY5Y cell line. SH-SY5Y cells were treated with methadone at a concentration of 10 µM for 24 hours. The expression level of the telomerase reverse transcriptase gene (TERT, MIM: 187270) was then measured in three biological replicates, as described elsewhere.¹³ This gene is important because it encodes the catalytic subunit of the telomerase enzyme. The mean relative expression level (± standard error) of the gene in methadone-treated cells was 1.002 (± 0.010), with no significant difference between the treated and untreated cells (t = 0.34, df = 2, p = 0.774).

This finding is noteworthy because earlier studies have clearly shown that morphine, the active form of heroin in cells, decreases TERT gene expression. In addition, after longer exposure (60 days), morphine can significantly shorten telomere length.⁸ Thus, if methadone affected telomere length, it could act as an independent contributing factor (or potential mediator), which would be important to consider when interpreting clinical results. However, based on this small preliminary study, methadone does not appear to affect TERT expression or contribute to telomere shortening.

Notably, our finding is further supported by a recent study conducted by Dwivedi et al.¹⁴, in which human cortical organoids derived from two distinct induced pluripotent stem cell lines (A and B) were used to investigate the effects of methadone on early human brain development. The organoids were treated with 1 µM methadone for 50 days (from day 9 to day 60 of culture), a concentration within the range typically found in the plasma of pregnant women undergoing methadone maintenance therapy. To assess methadone-induced transcriptional changes, bulk mRNA sequencing was performed on control and treated samples, including three control and three treated samples from line A and four control and four treated samples from line B (a total of seven control and seven treated samples). Differential expression analysis was then performed, with baseline differences between the two cell lines incorporated as a covariate in the linear model to account for interindividual variability. Importantly, TERT expression remained unchanged in response to methadone treatment and was not among the differentially expressed genes identified in their analysis,¹⁴ consistent with our observations.

We acknowledge that our study has several limitations. First, only one methadone concentration (10 µM), one time point (24 hours), and one cell line (SH-SY5Y) were tested, which may limit the generalizability of our findings. Second, and more importantly, a major limitation is the indirect assessment of telomere length based on TERT gene expression. Although TERT encodes the catalytic subunit of telomerase, the relationship between TERT expression, telomerase activity, and eventual telomere length is complex and may vary across different tissues and biological contexts.^{15, 16} Therefore, our conclusion that methadone does not affect telomere length is based on indirect evidence and should be interpreted with caution. Definitive confirmation of this finding will require direct measurements of telomere length in subsequent cellular and human studies.

Overall, methadone does not appear to affect TERT expression. Therefore, the shorter telomere length observed in patients with heroin dependence is more likely caused by heroin (morphine) itself than by methadone maintenance therapy. This finding is encouraging from a clinical perspective because it suggests that methadone alone does not accelerate cellular aging through telomere shortening. However, further studies involving longer treatment periods and different doses are required.