Introduction:
Matrix metalloproteinase-9 (MMP-9) plays an imperative role in smoking related illnesses including cardiovascular diseases. The health hazard is basically due to presence of nicotine content in tobacco. Cotinine is the major degradable product of nicotine metabolism and is regarded as a sensitive marker for tobacco exposure.

Objectives:
This study was designed to assess and compare the level of serum MMP-9 and urinary cotinine (UC) in smokeless tobacco chewers (STC) and healthy tobacco non-users (controls).

Methods:
A Community-based comparative cross-sectional study was conducted in Dharan Sub-Metropolitan City from August 2017 to July 2018. A total of 102 STC and the same number of healthy controls, 18-44 years of age were enrolled in the study. A structured questionnaire was introduced to subjects after informed consent and biochemical tests for lipid profile, MMP-9 and UC were done. Snowball technique was used to enroll tobacco chewers. Ethical clearance was obtained from the Institutional Review Committee of BPKIHS, Nepal.

Results:
The findings from the present study revealed that UC was significantly higher in the STC group (1259.20±244.20 pg/ml) compared to the control group (8.86±2.45 pg/ml) (p<0.001). Serum MMP-9 was significantly higher in the STC group (1528.28±544.41 ng/L) compared to the control group (87.77±25.83 ng/L) (p<0.001). A Strong positive correlation was found between MMP-9 and UC in the STC group (p<0.001), while MMP-9 and UC were not significantly different with duration of tobacco use. The STC group had significantly higher MMP-9, UC, Lipid parameters (TC, TG, LDL-C) and lower HDL-C than the control group.

Conclusion(s):
Habitual tobacco chewers were confirmed by the measurement of cotinine in urine which was significantly higher in STC. This finding highlights the importance of cotinine which can be used as a biomarker for tobacco exposure. Significantly raised MMP-9 with UC might be responsible for the increased risk of CVDs as compared to risk in healthy controls.