Mediterranean diet as a strategy for preserving kidney function in patients with coronary heart disease with type 2 diabetes and obesity: a secondary analysis of CORDIOPREV randomized controlled trial

Abstract

Background: Type 2 diabetes mellitus (T2DM) is recognized an independent risk factor for chronic kidney disease (CKD). The precise contribution and differential response to treatment strategies to reduce kidney dysfunction, depending on whether obesity is present alongside T2DM or not, remain to be fully clarified. Our objective was to improve our understanding of how obesity contributes to kidney function in patients with T2DM and coronary heart disease (CHD), who are highly predisposed to CKD, to assign the most effective dietary approach to preserve kidney function.

Methods: 1002 patients with CHD and estimated glomerular filtration rate (eGFR)≥30 ml/min/1.73m², were randomized to consume a Mediterranean diet (35% fat, 22% MUFA, < 50% carbohydrates) or a low-fat diet (28% fat, 12% MUFA, > 55% carbohydrates). Patients were classified into four groups according to the presence of T2DM and/or obesity at baseline: Non-Obesity/Non-T2DM, Obesity/Non-T2DM, Non-Obesity/T2DM and Obesity/T2DM. We evaluated kidney function using serum creatinine-based estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (uACR) before and after 5-years of dietary intervention.

Results: Patients with Obesity/T2DM had the lowest baseline eGFR and the highest baseline uACR compared to non-diabetics (p < 0.05). After dietary intervention, the Mediterranean diet induced a lower eGFR decline in patients with Obesity/T2DM, compared to a low-fat diet but not in the other groups (p = 0.014). The Mediterranean diet, but not the low-fat diet, also reduced uACR only in patients with Obesity/T2DM (p = 0.024).

Conclusions: Obesity provided an additive effect to T2DM resulting in a more pronounced decline in kidney function compared to T2DM alone when compared to non-diabetics. In patients with concomitant presence of T2DM and obesity, with more metabolic complications, consumption of a Mediterranean diet seemed more beneficial than a low-fat diet in terms of preserving kidney function. These findings provide valuable insights for tailoring personalized lifestyle modifications in secondary prevention of cardiovascular disease.

Trial registration: URL, http://www.cordioprev.es/index.php/en .

Clinicaltrials: gov number, NCT00924937.

Fig. 1. Effect of the presence of T2DM and/or obesity at baseline on eGFR in patients with CHD.

Data are presented as mean ± standard error of the mean. Variables were compared using the analysis of variance (univariate ANOVA) adjusted by hypertension, smoking and drinking habits and use of lipid-lowering drugs. Differences were significant when p < 0.05. Different common letter denote significant differences between groups (p < 0.05). Test of linear trends across the groups were performed assigning the median value of eGFR and uACR to each group and treating the variable as continuous (p_trend). Non-obesity/Non-T2DM (n = 233), Obesity/Non-T2DM (n = 229), Non-obesity/T2DM (n = 208) and Obesity/T2DM (n = 332). CHD coronary heart disease; T2DM, type 2 diabetes mellitus; eGFR, estimated glomerular filtration rate; uACR, urine albumin-creatinine ratio.

Fig. 2. Effect of dietary intervention on eGFR in patients with CHD according to the presence or absence of obesity and/or T2DM.

A After both dietary patterns and (B) After each dietary pattern independently. Non-obesity/Non-T2DM (n = 203), Obesity/Non-T2DM (n = 197), Non-Obesity/T2DM (n = 178) and Obesity/T2DM (n = 275). Data are presented as Δ changes in eGFR (mL/min/1.73 m²) produced between post- and preintervention ± standard error of the mean. Variables were compared using the analysis of variance (univariate ANOVA) adjusted by age, sex, baseline hypertension, baseline eGFR categories, anti-diabetic drugs and changes in energy intake. Differences were significant when p < 0.05. * Significant differences between post and pre-intervention.^#Significant differences between Mediterranean diet and low-fat diet. Global p-values: p (group): presence in obesity and/or T2DM group effect and p (diet): diet effect. eGFR, estimated glomerular filtration rate; CHD, coronary heart disease; T2DM, type 2 diabetes mellitus.