Association between circulating levels of C1q/TNF-Related Protein-9 and type 2 diabetes mellitus: a systematic review and meta-analysis.

CONTEXT: C1q/TNF-Related Protein-9 (CTRP9) appears to be linked to type 2 diabetes mellitus (T2DM), according to growing research. But the literature on circulating levels of CTRP9 in patients with T2DM has been contradictory.

OBJECTIVE: This is a systematic review and meta-analysis to reassess the circulating level of CTRP9 in patients with T2DM, with and without complications.

DATA SOURCE: Relevant studies published until October 31 2021, were identified from the PubMed, Embase, Web of Science, The Cochrane Library, WanFang, CNKI, VIP, and CBM databases.

STUDY SELECTION: Participants with age ≥ 18 years with clinically diagnosed T2DM. Sex and diabetes complication type were not restricted.

DATA EXTRACTION: The data were extracted by 2 reviewers independently using a standard data collection form.

DATA SYNTHESIS: Analysis demonstrated significantly lower circulating levels of CTRP9 in patients with T2DM in comparison to patients without diabetes [(SMD=-1.36; 95%CI (-1.78 to -0.93); P<0.001), I2=97.5%, P<0.001]. Furthermore, the circulating level of CTRP9 in patients with T2DM related complications is lower than that in patients with T2DM without complications, regardless of macrovascular complications or microvascular complications [(SMD=-1.062; 95%CI (-1.466 to -0.658); P<0.001), I2=91.3%, P<0.001]. Subgroup analyses revealed that factors such as body mass index (BMI), T2DM duration, and fasting glucose (FBS) were the sources of heterogeneity (P=0.047, P=0.034, and P=0.07, respectively).

CONCLUSIONS: The present systematic review and meta-analysis found CTRP9 levels were lower in T2DM patients with or without complications. However, since it is a meta-analysis of most observational studies, these findings still need to be verified by further studies with a large sample size.