Association between the level of circulating adiponectin and prediabetes: A meta-analysis

Abstract

Aims/introduction: Adiponectin has been proposed to have an essential role in the regulation of insulin sensitivity and metabolism, but previous studies on levels of adiponectin in prediabetes remain inconsistent. The present study aimed to assess the differences of adiponectin levels between prediabetes patients and healthy controls by carrying out a meta-analysis.

Materials and methods: We carried out a systematic literature search of PubMed, EMBASE, and other databases for case-control studies and cohort studies measuring adiponectin levels in serum or plasma from prediabetes patients and healthy controls. The pooled weighted mean difference (WMD) and 95% confidence interval (CI) were used to estimate the association between adiponectin levels and prediabetes.

Results: Three cohort studies and 15 case-control studies with a total of 41,841 participants were included in the meta-analysis. The results showed that circulating adiponectin levels in prediabetes patients were significantly lower than that of healthy controls (WMD -1.694 μg/mL; 95% CI -2.151, -1.237; P < 0.001). Subgroup analysis showed more significant differences between prediabetes patients and healthy controls when the ratio of the homeostatic model assessment of insulin resistance was >2.12 (WMD -2.95 μg/mL; 95% CI -4.103, -1.806; P < 0.001) and average age was >60 years (WMD -2.20 μg/mL; 95% CI -3.207, -1.201; P < 0.001). Additionally, WMD in adiponectin showed a trend of direct correlation in subgroups of homeostatic model assessment of insulin resistance ratio, body mass index and age.

Conclusions: The present meta-analysis supports adiponectin levels in prediabetes patients being lower than that of healthy controls,indicating that the level of circulating adiponectin decreases before the onset of diabetes.

Keywords: Adiponectin; Meta-analysis; Prediabetes.

Figure 1

Flow chart of study selection. After careful discussion among the investigators, a total of 18 studies were included to carry out the meta-analysis.

Figure 2

Forest plot for adiponectin levels in prediabetes patients and healthy controls in included studies. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI). The result showed that the adiponectin levels in prediabetes patients were significantly lower than healthy controls (WMD –1.694 μg/mL; 95% CI –2.151, –1.237; P < 0.001).

Figure 3

Subgroup meta-analysis for adiponectin levels in prediabetes patients and healthy controls by geographic region. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI). Significant decrease of adiponectin levels was observed between prediabetes patients and healthy controls in the included studies carried out in Asia (WMD –1.412 μg/mL; 95% CI –1.770, –1.053; P < 0.001) and Europe (WMD –1.937 μg/mL; 95% CI –2.745, –1.128; P < 0.001).

Figure 4

Subgroup meta-analysis for adiponectin levels in prediabetes patients and healthy controls by homeostasis model assessment of insulin resistance ratio (HOMA-IR) ratio. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI). The total WMD in the included studies with homeostasis model assessment of insulin resistance ratio is significant and it showed a trend of a direct correlation except homeostasis model assessment of insulin resistance ratio <1.36.

Figure 5

Subgroup meta-analysis for adiponectin levels in prediabetes patients and healthy controls by age. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI). The total WMD in the included studies with age is significant and it showed a trend of a direct correlation with age.

Figure 6

Subgroup meta-analysis for adiponectin levels in prediabetes patients and healthy controls by body mass index. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI). The total WMD in the included studies with body mass index is significant and it showed a trend of a direct correlation with body mass index.

Figure 7

Subgroup meta-analysis for adiponectin levels in prediabetes patients and healthy controls by sex. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI). The total WMD in the included studies with sex is significant, and it showed that the decrease of adiponectin levels between prediabetes patients and healthy controls in female participants is more significant than that in male participants.

Figure 8

Publication bias for adiponectin levels in prediabetes patients and healthy controls in the included studies. No publication bias was observed in Begg's funnel plots and Egger's tests (t = –1.42, P = 0.173). SE, standard error.