The Association of Excess Body Weight with Risk of ESKD Is Mediated Through Insulin Resistance, Hypertension, and Hyperuricemia

Josef Fritz; Wolfgang Brozek; Hans Concin; Gabriele Nagel; Julia Kerschbaum; Karl Lhotta; Hanno Ulmer; Emanuel Zitt

doi:10.1681/ASN.2021091263

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Significance Statement

Insulin resistance, hypertension, hyperuricemia, and hypercholesterolemia are candidates for mediating the effect of BMI on ESKD. However, the independent contributions of these factors have not been quantified in prospective studies to date. Applying a model of mediation, the authors quantified the contribution of these four metabolic factors to the association of BMI with ESKD in a population-based cohort of 100,269 predominantly healthy Austrian individuals. They found that the association of BMI with ESKD was mediated through TyG index (a measure of insulin resistance), mean arterial pressure, and uric acid, but not through total cholesterol. The findings suggest that in addition to weight reduction, the control of metabolic risk factors is important in mitigating the adverse effects of BMI on kidney function.

Abstract

Background Insulin resistance, hypertension, hyperuricemia, and hypercholesterolemia are hypothesized to be important intermediates in the relationship between excess body weight and CKD risk. However, the magnitude of the total effect of excess body weight on ESKD mediated through these four pathways remains to be quantified.

Methods We applied a model for analysis of correlated mediators to population-based data from 100,269 Austrian individuals (mean age 46.4 years). Association of body mass index (BMI) was coalesced with ESKD risk into direct association. Indirect associations were mediated through the triglyceride-glucose (TyG) index (as an indicator of insulin resistance), mean arterial pressure (MAP), uric acid (UA), and total cholesterol (TC).

Results Mean follow-up was 23.1 years with 463 (0.5%) incident ESKD cases. An unhealthy metabolic profile (prevalence 32.4%) was associated with a markedly increased ESKD risk (multivariably adjusted hazard ratio (aHR), 3.57; 95% CI, 2.89 to 4.40), independent of BMI. A 5-kg/m² higher BMI was associated with a 57% increased ESKD risk (aHR_{total association}, 1.57; 1.38 to 1.77). Of this association, 99% (76% to 140%) arose from all mediators jointly; 33% (22% to 49%) through TyG index; 34% (24% to 50%) through MAP; 30% (21% to 45%) through UA; and 2% (−1% to 4%) through TC. The remaining direct association was nonsignificant (aHR_{direct association}, 1.01; 0.88 to 1.14).

Conclusions TyG index, MAP, and UA, but not TC, mediate the association of BMI with ESKD in middle-aged adults. Our findings highlight that in addition to weight reduction, the control of metabolic risk factors might be essential in mitigating the adverse effects of BMI on kidney function.

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