Purpose: Cathepsin L (CTSL) and B (CTSB) were lysosomal proteases, and their expression and activity contribute to the progression of inflammation in obese rodents. Our aim was to investigate CTSB and CTSL expression in omental adipose tissue (AT) of patients with obesity and to correlate CTSB and CTSL expression with proinflammatory cytokines (CCL-2, IL-6 and IL-1β).
Patients and Methods: A total of 12 patients without obesity (NOB) and 51 patients with obesity (OB) were involved in this study. Omental AT was collected from all the participants for RNA extraction. Expressions of CTSB, CTSL and proinflammatory cytokines (CCL-2, IL-6 and IL-1β) were qualified with qRT-PCR. BMI (body mass index) and metabolic parameters were measured.
Results: The mRNA expression levels of both CTSB and CTSL were upregulated in the OB group (t = 2.693, P < 0.05; t = 2.849, P < 0.01) and were related to TC levels (Std.β=0.443, P < 0.05; Std.β=0.439, P < 0.05). However, only the CTSB level was related to BMI (Std.β=0.261, P < 0.05). In multiple regression analysis, CTSL was independently associated with CCL-2, IL-6 and IL-1β levels (Std.β=0.352– 0.462, P < 0.05).
Conclusion: CTSB and CTSL gene expressions were elevated in the omental AT of OB group. CTSL, but not CTSB, was positively correlated with proinflammatory cytokines independently, suggesting that the dysregulation of CTSL may play a significant role in the inflammatory process.
Keywords: adipose tissue, cathepsin, cytokines, obesity, inflammation