Effects of Cyclocarya paliurus Aqueous and Ethanol Extracts on Glucolipid Metabolism and the Underlying Mechanisms: A Meta-Analysis and Systematic Review

Abstract

Background and Aims: Cyclocarya paliurus (CP) has been used as an herbal tea to treat diabetes mellitus and obesity for hundreds of years. Previous research suggests that CP specifically restores glucolipid metabolic homeostasis, and the two most studied preparations are aqueous and ethanol extracts. In order to verify the effect of CP on glucolipid metabolism in animal models with metabolic syndrome, a meta-analysis was performed, and the active components and underlying mechanisms were systematically reviewed. Methods: Four databases: PubMed, Web of Science, Embase, and Cochrane Library were searched to identify potential literature. Data of blood glucose (BG) level, area under curve (AUC) of oral glucose tolerance test (OGTT), total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) levels were extracted as indicators of the assessment of CP's effects. Follow-up analyses including subgroup analysis, meta-regressions, and publication bias were also conducted. Results: A total of 96 papers were identified from the databases and 11 papers including 31 data reports were involved in the meta-analysis. CP had a positive effect in down-regulating BG, AUC of OGTT, TC, TG, and LDL, and up-regulating HDL (P < 0.001, 95% confidence interval of standard mean difference did not incorporate the null value 0). Conclusion: CP showed definite activity of regulating glucolipid metabolism in animal models, and it exerted its function through multiple mechanisms including but not limited to: (1) improving insulin resistance; (2) protecting pancreatic β cells; (3) decreasing inflammatory infiltration; and (4) anti-oxidative stress.

Keywords: Cyclocarya paliurus; dyslipidemia; glucolipid metabolism; hyperglycemia; insulin resistance; metabolic syndrome.

Figure 1

Flow diagram for article selection for the meta-analysis. CP, Cyclocarya paliurus.

Figure 2

Risk of bias of 11 studies included in the meta-analysis. Yellow dots, unclear risk; green dots, low risk.

Figure 3

Forest plot for the effect of Cyclocarya paliurus (CP) on blood glucose levels in animal models. Subgroup analysis was performed according to doses.

Figure 4

Forest plot for the effect of Cyclocarya paliurus (CP) on area under curve of oral glucose tolerance tests in animal models. Subgroup analysis was performed according to doses.

Figure 5

Effect size of CPAE and CPEE on included parameters. CPAE, Cyclocarya paliurus aqueous extract; CPEE, Cyclocarya paliurus ethanol extract; BG, blood glucose level; OGTT, oral glucose tolerance test; TC, total cholesterol; TG, triglyceride; HDL, high-density lipoprotein; LDL, low-density lipoprotein.

Figure 6

Forest plot for the effect of Cyclocarya paliurus (CP) on total cholesterol levels in animal models. Subgroup analysis was performed according to doses.

Figure 7

Forest plot for the effect of Cyclocarya paliurus (CP) on triglyceride levels in animal models. Subgroup analysis was performed according to doses.

Figure 8

Forest plot for the effect of Cyclocarya paliurus (CP) on high-density lipoprotein levels in animal models. Subgroup analysis was performed according to doses.

Figure 9

Forest plot for the effect of Cyclocarya paliurus (CP) on low-density lipoprotein levels in animal models. Subgroup analysis was performed according to doses.

Figure 10

Funnel plot for publication bias in the meta-analysis.

Figure 11

Diagram of the mechanisms investigated for the effect of Cyclocarya paliurus (CP) on glucolipid metabolism (created with BioRender.com).