Elevated CTSL Gene Expression Correlated with Proinflammatory Cytokines in Omental Adipose Tissue of Patients with Obesity

Abstract

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

Abbreviations

BMI, body mass index; IL-6, interleukin-6; IL-1β, interleukin-1β; CCL-2, C-C motif chemokine 2; MCP-1, monocyte chemoattractant protein-1; CTSD, cathepsin D; SCAT, subcutaneous adipose tissue; TG, triglycerides; LDL, low-density lipoproteins; HDL, high-density lipoproteins; TC, total cholesterol; HOMA-IR, Homeostatic Model Assessment of Insulin Resistance; HbA1c, glycosylated hemoglobin; NLRP3, NLR family pyrin domain containing 3.

Acknowledgments

We are grateful to all the authors for their contributions to this study.

Disclosure

All the authors declared no conflicts of interest in this work.

Additional information

Funding

This work is supported by grants from the Science and TechnologyDepartment of Yunnan Province (Nos. 202003AC100014) and the Health Science and Technology Fund of Yunnan Province (2018NS0206) in China.