Association of low aerobic fitness with hyperfiltration and albuminuria in men

Association of Fitness With Racial Differences in Chronic Kidney Disease

INTRODUCTION

Non-white minorities are at higher risk for chronic kidney disease than non-Hispanic whites. Better cardiorespiratory fitness is associated with slower declines in estimated glomerular filtration rate and a lower incidence of chronic kidney disease. Little is known regarding associations of fitness with racial disparities in chronic kidney disease.

METHODS

A prospective cohort of 3,842 young adults without chronic kidney disease completed a maximal treadmill test at baseline in 1985-1986. Chronic kidney disease status was defined as estimated glomerular filtration rate of <60 mL/min/1.73 m² during 10-, 15-, 20-, 25-, and 30-year follow-up assessments (through 2006). Analyses were completed in 2019. Multivariable Cox models were used to determine hazard ratios and 95% CI for incidence of chronic kidney disease. Multivariable models included race, gender, age, field center, education, baseline estimated glomerular filtration rate, and time-varying covariates of healthy diet index, smoking status, alcohol intake, BMI, systolic blood pressure, and fasting glucose. Percent attenuation quantified the association of fitness to racial disparities in chronic kidney disease.

RESULTS

Chronic kidney disease incidence was higher among blacks (n=83/1,941, 1.61 per 1,000 person years) than whites (43/1,901, 0.82 per 1,000 person years). Every 1-minute shorter treadmill duration was associated with 1.14 (95% CI=1.04, 1.25) times higher risk of chronic kidney disease. Blacks were 1.72 (95% CI=1.13, 2.63) times more likely to develop chronic kidney disease compared with whites. The risk was reduced to 1.54 (95% CI=1.01, 2.39) with fitness added. This suggests that fitness is associated with 20.4% (95% CI=5.8, 43.0%) of the excess risk of chronic kidney disease attributable to race.

CONCLUSIONS

Low fitness is a modifiable factor that may contribute to the racial disparity in chronic kidney disease.

Exercise effects on physiological function during aging

The decrease in cognitive/motor functions and physical abilities severely affects the aging population in carrying out daily activities. These disabilities become a burden on individuals, families and society in general. It is known that aging conditions are ameliorated with regular exercise, which attenuates the age-associated decline in maximal oxygen uptake (VO2max), production of reactive oxygen species (ROS), decreases in oxidative damage to molecules, and functional impairment in various organs. While benefits of physical exercise are well-documented, the molecular mechanisms responsible for functional improvement and increases in health span are not well understood. Recent findings imply that exercise training attenuates the age-related deterioration in the cellular housekeeping system, which includes the proteasome, Lon protease, autophagy, mitophagy, and DNA repair systems, which beneficially impacts multiple organ functions. Accumulating evidence suggests that exercise lessens the deleterious effects of aging. However, it seems unlikely that systemic effects are mediated through a specific biomarker. Rather, complex multifactorial mechanisms are involved to maintain homeostatic functions that tend to decline with age.

Association of renal hyperfiltration with incident proteinuria - A nationwide registry study

To elucidate the association between renal hyperfiltration (RHF) and incident proteinuria, the data from 11,559,520 Korean adults who had undergone health screenings ≥ 3 times between 2009 and 2014 and had glomerular filtration rate (GFR) ≥60 mL/min/1.73m2 and negative dipstick test for proteinuria at baseline, were retrospectively analyzed. GFR was estimated with the Chronic Kidney Disease Epidemiology Collaboration equation based on serum creatinine, and RHF was defined as GFR >95th percentile adjusted for sex, age, body size, and diabetes and/or hypertension medication. The adjusted hazard ratio (aHR) of incident proteinuria in the RHF was 1.083 (95% CI, 1.069~1.097) compared to that of the non-RHF with Cox regression model. The association between RHF and incident proteinuria was not only in diabetic but also in non-diabetic subjects. This association was not observed in women (p for interaction <0.001). A reverse J-shaped association was found between the adjusted GFR slope and aHR of incident proteinuria. Both lower and higher GFR were associated with incident proteinuria in men. In conclusion, RHF was associated with incident proteinuria in men. Clinical studies are necessary to study whether the alleviation of RHF can prevent incident proteinuria.

Unobtrusive Estimation of Cardiorespiratory Fitness with Daily Activity in Healthy Young Men

Despite the importance of cardiorespiratory fitness, no practical method exists to estimate maximal oxygen consumption (VO₂max) without a specific exercise protocol. We developed an estimation model of VO₂max, using maximal activity energy expenditure (aEEmax) as a new feature to represent the level of physical activity. Electrocardiogram (ECG) and acceleration data were recorded for 4 days in 24 healthy young men, and reference VO₂max levels were measured using the maximal exercise test. aEE was calculated using the measured acceleration data and body weight, while heart rate (HR) was extracted from the ECG signal. aEEmax was obtained using linear regression, with aEE and HR as input parameters. The VO₂max was estimated from the aEEmax using multiple linear regression modeling in the training group (n = 16) and was verified in the test group (n = 8). High correlations between the estimated VO₂max and the measured VO₂max were identified in both groups, with a 15-hour recording being sufficient to produce a highly accurate VO₂max estimate. Additional recording time did not significantly improve the accuracy of the estimation. Our VO₂max estimation method provides a robust alternative to traditional approaches while only requiring minimal data acquisition time in daily life.

Renal function and attributable risk of death and cardiovascular hospitalization in patients with cardiovascular risk factors from a registry-based cohort: the Estudio Cardiovascular Valencia-risk study

BACKGROUND

Information about the attributable risk associated with renal dysfunction in patients with cardiovascular risk factors is lacking.

OBJECTIVE

We aimed to estimate the attributable risk associated with chronic kidney disease Epidemiology Collaboration-estimated glomerular filtration rate (eGFR), for all-cause mortality, and cardiovascular hospitalization.

DESIGN, SETTING, AND PARTICIPANTS

Prospective study of study participants with cardiovascular risk factors in 2008-2012. We included 52 007 cardiovascular disease-free men and women aged 30 years or older with hypertension, diabetes, or dyslipidemia, who underwent routine health examinations in primary care.

RESULTS

A total of 6639 (12.8%) patients had eGFR below 60 ml/min per 1.73 m and among them 1782 (3.4%) had 45 ml/min per 1.73 m or lower. During an average follow-up time of 3.2 years, 54.12 deaths, 99.98 coronary heart disease (CHD) hospitalizations, and 90.64 stroke hospitalizations/10 000 person-years were recorded. The population attributable risks associated with having a GFR lower than 60 ml/min per 1.73 m were 6.9% (95% confidence interval = 2.07, 10.65) for all-cause mortality, 6.8% (4.3, 9.4) for CHD hospitalization, and 4.1% (1.02, 7.00) for stroke hospitalization. Participants with increasing number of cardiovascular risk factors displayed increasing population attributable risks associated to a GFR less than 60 ml/min per 1.73 m for all-cause mortality and CHD (P heterogeneity 0.002 and 0.05, respectively).

CONCLUSION

In a large general practice cohort of patients with cardiovascular disease risk factors, decreasing eGFR levels were associated with additional attributed risk of mortality and cardiovascular disease. Our findings underscore that intensified efforts are needed to reduce the cardiovascular disease burden associated to chronic kidney disease.

The Association between Renal Hyperfiltration and the Sources of Habitual Protein Intake and Dietary Acid Load in a General Population with Preserved Renal Function: The KoGES Study

Although the differential response of the kidney to the acute load of various sources of dietary protein in subjects with normal renal function is well known, the influence of habitual dietary protein intake and dietary acid load on renal function has not been tested well. The association between renal hyperfiltration (RHF), the earlier and possibly reversible stage of chronic kidney disease, and the sources of habitual dietary protein and dietary acid load was analyzed with the baseline data of 123,169 middle-aged healthy Koreans of a large prospective cohort study, who had a baseline estimated glomerular filtration rate (eGFR) >60 mL/min/m2 and no known history of diabetes and/or hypertension. eGFR was calculated with the Chronic Kidney Disease Epidemiology Collaboration equation using serum creatinine and RHF was defined as eGFR >95th percentile after adjustment for age, sex, height, and body weight. Dietary acid load was calculated with estimated net endogenous acid production (eNEAP). Although the level of habitual intake of animal protein was positively and vegetable protein was negatively associated with RHF, this association was significant only in women and younger participants (younger than sex-specific median age). The odds for RHF increased as the percentile rank of eNEAP increased until about the 50th percentile and then leveled off. The positive association between eNEAP and RHF was significant in both sexes and age groups. Dietary acid load was associated with RHF regardless of sex and age and rather than the amount of the total or the individual sources of habitual dietary protein, may be a better target for the dietary intervention of chronic kidney disease.

Association between lower serum bicarbonate and renal hyperfiltration in the general population with preserved renal function: a cross-sectional study

Background

Lower serum bicarbonate, mainly due to the modern Western-style diet, and renal hyperfiltration (RHF) are both independently associated with higher mortality in the general population with preserved renal function. The objective of this study was to evaluate the association between serum bicarbonate and RHF.

Methods

The health data of 41,886 adults with an estimated glomerular filtration rate (eGFR) ≥60 mL/min per 1.73 m² were analyzed. The eGFR was calculated with the Chronic Kidney Disease Epidemiology Collaboration creatinine equation and RHF was defined as eGFR with adjusted residuals > sex-specific 95^th percentile.

Results

The adjusted mean of eGFR was lower in the highest quintile of serum bicarbonate than in other quintiles, after adjusting for confounders. A lower percentile rank of serum bicarbonate was associated with higher odds of RHF. The odds ratio (OR) for RHF in the lowest quintile of serum bicarbonate was 1.39 (95 % confidence interval, 95 % CI, 1.11–1.75) compared to the highest, after adjusting for confounders. With subgroup analysis, the association was prominent in participants with a body mass index >25 kg/m² (OR 1.98, 95 % CI 1.32–2.95 in the lowest quintile compared to the highest), compared to those with a body mass index ≤25 kg/m² (OR 1.18, 95 % CI 0.89–1.56 in the lowest quintile compared to the highest).

Conclusions

This study observed an association between lower serum bicarbonate and higher odds of RHF and the possible differential effect of obesity in this association. It is necessary to confirm the association between lower serum bicarbonate and RHF and its causality.

Renal hyperfiltration as a novel marker of all-cause mortality

Although renal hyperfiltration (RHF) or an abnormal increase in GFR has been associated with many lifestyles and clinical conditions, including diabetes, its clinical consequence is not clear. RHF is frequently considered to be the result of overestimating true GFR in subjects with muscle wasting. To evaluate the association between RHF and mortality, 43,503 adult Koreans who underwent voluntary health screening at Seoul National University Hospital between March of 1995 and May of 2006 with baseline GFR≥60 ml/min per 1.73 m(2) were followed up for mortality until December 31, 2012. GFR was estimated with the Chronic Kidney Disease Epidemiology Collaboration creatinine equation, and RHF was defined as GFR>95th percentile after adjustment for age, sex, muscle mass, and history of diabetes and/or hypertension medication. Muscle mass was measured with bioimpedance analysis at baseline. During the median follow-up of 12.4 years, 1743 deaths occurred. The odds ratio of RHF in participants with the highest quartile of muscle mass was 1.31 (95% confidence interval [95% CI], 1.11 to 1.54) compared with the lowest quartile after adjusting for confounding factors, including body mass index. The hazard ratio of all-cause mortality for RHF was 1.37 (95% CI, 1.11 to 1.70) by Cox proportional hazards model with adjustment for known risk factors, including smoking. These data suggest RHF may be associated with increased all-cause mortality in an apparently healthy population. The possibility of RHF as a novel marker of all-cause mortality should be confirmed.

Aerobic endurance capacity affects spatial memory and SIRT1 is a potent modulator of 8-oxoguanine repair

Regular exercise promotes brain function via a wide range of adaptive responses, including the increased expression of antioxidant and oxidative DNA damage-repairing systems. Accumulation of oxidized DNA base lesions and strand breaks is etiologically linked to for example aging processes and age-associated diseases. Here we tested whether exercise training has an impact on brain function, extent of neurogenesis, and expression of 8-oxoguanine DNA glycosylase-1 (Ogg1) and SIRT1 (silent mating-type information regulation 2 homolog). To do so, we utilized strains of rats with low- and high-running capacity (LCR and HCR) and examined learning and memory, DNA synthesis, expression, and post-translational modification of Ogg1 hippocampal cells. Our results showed that rats with higher aerobic/running capacity had better spatial memory, and expressed less Ogg1, when compared to LCR rats. Furthermore, exercise increased SIRT1 expression and decreased acetylated Ogg1 (AcOgg1) levels, a post-translational modification important for efficient repair of 8-oxo-7,8-dihydroguanine (8-oxoG). Our data on cell cultures revealed that nicotinamide, a SIRT1-specific inhibitor, caused the greatest increase in the acetylation of Ogg1, a finding further supported by our other observations that silencing SIRT1 also markedly increased the levels of AcOgg1. These findings imply that high-running capacity is associated with increased hippocampal function, and SIRT1 level/activity and inversely correlates with AcOgg1 levels and thereby the repair of genomic 8-oxoG.