Comparison of Serum Prolidase Activity in Smokers and Non-Smokers.

Objective: To investigate the effect of smoking on serum prolidase enzyme activity and proline/hydroxyproline levels.

Study design: A case control study. Place and Duration of the Study: Department of Family Medicine, Ankara Bilkent City Hospital, Family Medicine, Ankara, Turkiye, from June 2022 to May 2023.

Methodology: A total of 150 participants were included in the study, including 54 smokers, 43 ex-smokers, and 53 non-smokers. Proline and hydroxyproline concentrations were analysed using a liquid chromatography-mass spectrometre (Sciex QTrap 4500-Foster City-CA). Serum prolidase enzyme activity was determined with the Chinard reagent according to the spectrophotometric test. Multinomial logistic regression analysis compared prolidase activity and amino acid levels among smokers, ex-smokers, and non-smokers.

Results: The median values of prolidase enzyme activity were statistically lower in the smoker group 734.2 (643.8-799.6) than in the non-smoker group 836.8 (755.2-884.2, β = 0.003, OR = 0.997, 95% CI = 0.994-1,000, p = 0.025. In multiple comparisons, the median values of hydroxyproline were significantly higher in the non-smoker group 8.99 (5.76-11.22) than in the ex-smoker 6.05 (4.37-8.21, p = 0.008). Still, no significant difference was found in the multinomial logistic regression analysis (β = -0.051, OR = 0.951, CI 95% = 0.848-1.066, p = 0.384).

Conclusion: Serum prolidase enzyme activity was significantly lower in smokers than in non-smokers. The prolidase activity may be a fruitful area of ​​study to understand the pathophysiology of smoking-related diseases better.

Key words: Smoking, Prolidase, Proline, Hydroxyproline, Collagen synthesis, COPD, Malignancy.