Increased levels of YKL-40 in patients with diabetes mellitus: a systematic review and meta-analysis

BACKGROUND: Diabetes mellitus (DM) could be classified as type 1 diabetes mellitus (T1DM), type 2 diabetes mellitus (T2DM), gestational diabetes mellitus (GDM) and others according to etiology and pathology. Diabetic nephropathy (DN) is one of the most serious complications of DM. YKL-40 is a marker of inflammation and some studies have indicated that DM was related with inflammation. The objective of our study is to perform a systematic review and meta-analysis to confirm the relationship between YKL-40 and DM as well as DN. METHODS: Pubmed, Embase, CNKI and Chinese wanfang databases were searched for eligible studies by two independent authors. Studies were included in this meta-analysis if they fulfilled the following inclusion criteria: (1) a study involving the role of YKL-40 in DM (or DN) designed as a case–control study or cohort study; (2) the data of serum YKL-40 levels were available; (3) studies were published in English or Chinese. Finally, twenty-five studies were included in this meta-analysis. RESULTS: Compared with healthy controls, DM patients had significantly higher levels of YKL-40 (DM: SMD = 1.62, 95% CI 1.08 to 2.25, P = 0.000; GDM: SMD = 2.85, 95% CI 1.01 to 4.70, P = 0.002). Additionally, DM patients with different degree of albuminuria had significantly higher levels of YKL-40 compared with healthy controls (normoalbuminuria: SMD = 1.58, 95% CI 0.59 to 2.56, P = 0.002; microalbuminuria: SMD = 2.57, 95% CI 0.92 to 4.22, P = 0.002; macroalbuminuria: SMD = 2.69, 95% CI 1.40 to 3.98, P = 0.000) and serum YKL-40 levels increased with increasing severity of albuminuria among DM patients (microalbuminuria vs normoalbuminuria: SMD = 1.49, 95% CI 0.28 to 2.71, P = 0.016; macroalbuminuria vs microalbuminuria: SMD = 0.93, 95% CI 0.34 to 1.52, P = 0.002). CONCLUSIONS: Our current meta-analysis demonstrates that serum level of YKL-40 is increased in DM and positively associated with the severe degree of albuminuria. Therefore, we suggest that YKL-40 could be considered to be detected, along with other inflammatory markers, if DM, especially DN, is suspected.