Serum xanthophyll carotenoids are associated with estimated glomerular filtration rate in an aged cohort

The Effect of Randomized Beta-Carotene Supplementation on CKD in Men

Introduction

Beta-carotene (BC) protects the body against free radicals that may damage the kidney and lead to the development of acute kidney injury and chronic kidney disease (CKD). Previous studies in animal models have demonstrated a potential protective effect of 30 mg/kg BC supplementation on renal ischemia or reperfusion injury and subsequently improved kidney function. The extension of these findings to humans, however, remains unclear.

Methods

Our study leverages previously collected data from the Physicians' Health Study I (PHS I), a large-scale, long-term, randomized trial of middle-aged and older US male physicians testing 50 mg BC every other day for primary prevention of cardiovascular disease and cancer. We examined the impact of randomized BC supplementation on self-reported incident CKD identified by self-reports stating "yes" to kidney disease from annual follow-up questionnaires from randomization in 1982 through the end of the randomized BC intervention at the end of 1995, and on CKD defined as an estimated glomerular filtration rate (eGFR) < 60 ml/min per 1.73 m2 at the end of 1995. Analyses compared incident CKD between BC supplementation and placebo using Cox proportional hazards regression models and logistic regression. We also examined whether smoking status (current vs. former or never smoker) or other factors modified the effect of randomized BC supplementation on CKD.

Results

A total of 10,966 participants were randomized to BC, and 10,952 participants were randomized to a placebo group. Baseline characteristics between randomized BC groups were similar. There was no significant benefit between BC supplementation and self-reported incident CKD after adjusting for age and randomized aspirin treatment (hazard ratio [HR] = 0.97, 95% confidence interval [CI]: 0.86-1.08, P-value = 0.56). Stratified by smoking status, there was no significant benefit of BC supplementation and self-reported incident CKD either among former or never smokers (HR = 0.95, 95% CI: 0.84-1.07, P-value = 0.41) or current smokers (HR = 1.08, 95% CI: 0.78-1.50, P-value = 0.64). Smoking status did not modify the association between BC supplementation and incident CKD (P-interaction = 0.47). In subgroup analysis among those with available serum creatinine at the study end (5480 with BC and 5496 with placebo), there was no significant benefit between BC supplementation and CKD based on eGFR < 60 ml/min per 1.73 m2 (odds ratio [OR] = 0.96, 95% CI: 0.85-1.08, P-value = 0.49).

Conclusion

Long-term randomized BC supplementation did not affect the risk of incident CKD in middle-aged and older male physicians.

Chronic Kidney Disease Diets for Kidney Failure Prevention: Insights from the IL-11 Paradigm

Nearly every fifth adult in the United States and many older adults worldwide are affected by chronic kidney disease (CKD), which can progress to kidney failure requiring invasive kidney replacement therapy. In this review, we briefly examine the pathophysiology of CKD and discuss emerging mechanisms involving the physiological resolution of kidney injury by transforming growth factor beta 1 (TGFβ1) and interleukin-11 (IL-11), as well as the pathological consequences of IL-11 overproduction, which misguides repair processes, ultimately culminating in CKD. Taking these mechanisms into account, we offer an overview of the efficacy of plant-dominant dietary patterns in preventing and managing CKD, while also addressing their limitations in terms of restoring kidney function or preventing kidney failure. In conclusion, this paper outlines novel regeneration strategies aimed at developing a reno-regenerative diet to inhibit IL-11 and promote repair mechanisms in kidneys affected by CKD.

Association of low plasma antioxidant levels with all-cause mortality and coronary events in healthy middle-aged men from France and Northern Ireland in the PRIME study

BACKGROUND

The main underlying risk factors associated with coronary heart disease (CHD) are modifiable and oxidative injury and systemic inflammatory damage represent key aetiological factors associated with the development and progression of CHD and premature mortality.

OBJECTIVE

To examine associations of plasma antioxidant status with all-cause mortality and fatal or non-fatal cardiovascular events.

DESIGN

The PRIME study prospectively evaluated 9709 men aged 50-59 years between 1991 and 1993 in Northern Ireland and France who were free of CHD at recruitment and followed annually for deaths and cardiovascular events for 10 years. Serum concentrations of vitamin C, retinol, two forms of vitamin E (α- and γ-tocopherol) and six carotenoids were quantified by high-performance liquid chromatography. Baseline conventional risk factors were considered, as well as socioeconomic differences and lifestyle behaviours including diet, smoking habit, physical activity, and alcohol consumption through Cox regression analyses.

RESULTS

At 10 years, there were 538 deaths from any cause and 440 fatal or non-fatal cardiovascular events. After adjustment for country, age, systolic blood pressure, diabetes, body mass index, cholesterol, high density lipoprotein cholesterol, triglycerides, height, total physical activity, alcohol consumption and smoking habit, higher levels of all antioxidants were associated with significantly lower risk of all-cause mortality, with the exception of γ-tocopherol. Only retinol was significantly associated with decreased risk of cardiovascular events in a fully adjusted model.

CONCLUSIONS

Low antioxidant levels contribute to the gradient of all-cause mortality and cardiovascular incidence independent of lifestyle behaviours and traditional cardiovascular and socioeconomic risk factors.

Dietary patterns associated with renal impairment in the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA)

Background

Dietary-based primary prevention guidelines for chronic kidney disease (CKD) treatment are lacking due to limited evidence. Single nutrient intake studies do not account for complex dietary interactions. We assessed associations between dietary patterns and renal function in the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA).

Design

A cross-sectional observational study used NICOLA baseline dietary data collected between February 2014 and March 2016 via a food frequency questionnaire for 2590 participants aged ≥ 50 years. Principal component analysis identified a posteriori dietary patterns. Renal function was characterised by estimated glomerular filtration rate (eGFR) using serum creatinine and cystatin-C. Associations were assessed according to quintiles of dietary pattern adherence and multivariable regression analysis examined associations with eGFR.

Results

Variation in three dietary patterns was significantly associated with eGFR. After adjustment for potential confounders, participants with least adherence to the ‘healthy’ dietary pattern 1 had a mean eGFR 3.4 ml/min/1.73m² (95% confidence interval, [CI] − 5.0, − 1.7, p < 0.001) lower than the most adherent. Those with lowest adherence to the ‘unhealthy’ dietary pattern 2 had a mean eGFR 1.9 ml/min/1.73m² (CI 0.2, 3.5, p = 0.03) higher than those with highest adherence. Participants with lowest adherence to dietary pattern 3, characterised by a high consumption of alcohol and coffee, had a mean eGFR 1.8 ml/min/1.73m² (− 3.5, − 0.01, p = 0.05) lower than those with greatest adherence.

Conclusions

Our findings identify independent associations between dietary patterns and eGFR. These findings can inform the development of diet-related primary prevention advice for CKD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02579-z.

Fecal Metabolomics Reveals Distinct Profiles of Kidney Transplant Recipients and Healthy Controls

Monitoring graft recipients remains dependent on traditional biomarkers and old technologies lacking specificity, sensitivity, or accuracy. Recently, metabolomics is becoming a promising approach that may offer to kidney transplants a more effective and specific monitoring. Furthermore, emerging evidence suggested a fundamental role of gut microbiota as an important determinant of patients’ metabolomes. In the current study, we enrolled forty stable renal allografts recipients compared to twenty healthy individuals. Samples were taken at different time points from patient to patient following transplantation surgery, which varied from 3 months to 22 years post-graft. All patients started the immunosuppression therapy immediately following kidney graft (Day 0). Gas chromatography–mass spectrometry (GC–MS) was employed to perform untargeted analysis of fecal metabolites. Globally, the fecal metabolic signature was significantly different between kidney transplants and the control group. Fecal metabolome was dominated by lipids (sterols and fatty acids) in the stable transplant group compared to the controls (p < 0.05). Overall, 18 metabolites were significantly altered within kidney transplant recipients. Furthermore, the most notable altered metabolic pathways in kidney transplants include ubiquinone and other terpenoid-quinone biosynthesis, tyrosine metabolism, tryptophan biosynthesis, and primary bile acid biosynthesis. Fecal metabolites could effectively distinguish stable transplant recipients from controls, supporting the potential utility of metabolomics in rapid and non-invasive diagnosis to produce relevant biomarkers and to help clinicians in monitoring kidney transplants. Further investigations are needed to clarify the physiological relevance of fecal metabolome and to assess the impact of microbiota modulation.