Relationship between Decreased Serum Superoxide Dismutase Activity and Metabolic Syndrome: Synergistic Mediating Role of Insulin Resistance and β-Cell Dysfunction

Figure 4

Mediation model analysis of the association among SOD activity, ISIM, ISSI-2, and MS as well as MS-related metabolic abnormalities. represents independent variable (SOD activity); represents dependent variable ((a) MS; (b): log(TG); (c) BMI; (d) WC; (e) log(PG120)); M1 and M2 represent mediating variables 1 (log10(ISIM)) and 2 (sqrt(ISSI-2)); indirect effects 1, 2, and 3 represent the indirect effect of , , and , respectively. The effect was presented as (95% CI). The absence of “0” in the 95% CI represents the statistical significance of the effect. The indirect effects 1, 2, and 3 and the direct effect are significant in (a). The indirect effect 1 is significant in (b–d) whereas the indirect effects 2 and 3 are significant in (e). Abbreviations: : β-coefficient; 95% CI: 95% confidence intervals; SOD: superoxide dismutase; ISIM: Matsuda insulin sensitivity index; ISSI-2: insulin secretion-sensitivity index-2; MS: metabolic syndrome; TG: triglyceride; BMI: body mass index; WC: waist circumference; PG120: postload plasma glucose at 120 min during OGTT.

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