Combined effects of sleep and objectively-measured daily physical activity on arterial stiffness in middle-aged and older adults.

Although sleep quality and physical activity (PA) may influence on arterial stiffness, the combined effects of these two factors on arterial stiffness remain unknown. A total of 103 healthy middle-aged and older men and women (aged 50-83 years) with no history of cardiovascular disease and depression were included in this study. Arterial stiffness was measured using carotid-femoral pulse wave velocity (cfPWV), brachial-ankle PWV (baPWV), and femoral-ankle PWV (faPWV). Poor sleepers were defined as those with a Pittsburgh Sleep Quality Index score of >5.5. Using an accelerometer for seven consecutive days, low levels of PA were defined as low moderate-to-vigorous-intensity PA (MVPA) <19.0 min/day and low step counts <7100 steps/day, respectively. Poor sleepers with low PA levels, as determined by MVPA and daily steps, showed higher cfPWV, but not faPWV or baPWV, in middle-aged and older adults. Furthermore, in the analysis of covariance (ANCOVA) analyses adjusted for age, obesity, dyslipidemia, and sedentary behavior, the cfPWV result remained significant. Our study revealed that the coexistence of poor sleep quality and decreased PA (low MVPA or daily steps) might increase central arterial stiffness in middle-aged and older adults. Therefore, adequate sleep (good and sufficient sleep quality) and regular PA, especially at appropriate levels of MVPA (i.e., at least of 7100 steps/day), should be encouraged to decrease central arterial stiffness in middle-aged and older adults.

Sugar-Rich Food Intake Is Negatively Associated with Plasma Pentraxin 3 Levels.

Background: Levels of pentraxin 3 (PTX3), an anti-inflammatory cardioprotective protein, increase after weight loss in obese men and aerobic exercise in non-obese adults. However, the effect of nutritional characteristics on PTX3 levels remains unclear. This population-based, cross-sectional study investigated the association between circulating PTX3 levels and food intake in Japanese adults. Methods: We hypothesized that the consumption of high amounts of high-sugar foods would lead to low plasma PTX3 levels, resulting in obesity. This study included 327 participants categorized depending on the consumption of the recommended amount of confectionary and sugar-sweetened beverages (CSSB) into high and low groups. Results: PTX3 levels were significantly lower in the high CSSB group than in the low CSSB group. Biological sex was the strongest effector of PTX3 levels. Moreover, the intake of Tsukudani and CSSB, as well as some metabolic syndrome factors, also affect PTX3 levels. In the groups categorized by sex and age, the determinants of PTX3 levels differed. Body mass index, waist circumference (WC), and high-density lipoprotein cholesterol (HDL-C) were significantly associated with PTX3 levels in women. Tsukudani, HDL-C, heart rate, saturated fatty acids, systolic blood pressure, and CSSB were associated with PTX3 levels in individuals aged >65 years. Conclusion: Our results show that circulating PTX3 levels are affected by sex, sugar-rich foods, and metabolic syndrome characteristics (WC, HDL-C).

Associations of circulating xanthine oxidoreductase activity with cardiometabolic risk markers in overweight and obese Japanese men: a cross-sectional pilot study.

Circulating xanthine oxidoreductase (XOR) activity may contribute to the pathogenesis of obesity-related adverse cardiometabolic profiles. This pilot study aimed to examine the cross-sectional associations between plasma XOR activity and cardiometabolic risk (CMR) markers in overweight and obese men. In 64 overweight and obese Japanese men (aged 31-63 years), plasma XOR activity and several CMR markers, such as homeostasis model assessment of insulin resistance (HOMA-IR), and clustered CMR score were measured in each participant. Clustered CMR score was constructed based on waist circumference, triglyceride, blood pressure, fasting plasma glucose, and high-density lipoprotein cholesterol. Plasma XOR activity in overweight and obese men was positively associated with the body mass index, waist circumference, visceral fat area, body fat mass, hemoglobin A1c, serum 8-hydroxy-2'-deoxyguanosine, HOMA-IR, and clustered CMR score and was inversely associated with handgrip strength and high-density lipoprotein cholesterol. Multiple linear regression analysis further demonstrated that the associations of plasma XOR activity with HOMA-IR and the clustered CMR score remained significant after adjustment for covariates including uric acid. Our data demonstrate that circulating XOR activity was independently associated, albeit modestly, with HOMA-IR and the clustered CMR score. These preliminary findings suggest that circulating XOR activity can potentially be one of the preventive targets and biomarkers of cardiometabolic disorders in over-weight and obese men.

Effects of aerobic exercise training on mental health and arterial stiffness in middle-aged and older adults.

BACKGROUND: Aging is associated with deterioration of arterial function and mental health, which are known as cardiovascular risk factors. The present study investigated the effect of aerobic exercise training on mental health and arterial stiffness in middle-aged and older adults. METHODS: Twenty-nine healthy middle-aged and older adults were assigned to either the aerobic exercise training (N.=14) or the control groups (N.=15). The aerobic exercise training group completed 12 weeks of moderate aerobic exercise training for 3-4 session per week (30-60 minutes). The control group did not change their levels of physical activity. Before and after the 12-week period, the General Health Questionnaire (GHQ) and carotid ß-stiffness index, peak oxygen uptake were measured. RESULTS: At the onset of the 12-week period, the GHQ score, Carotid Β-Stiffness Index, and other key variables did not differ significantly between the aerobic exercise and control groups. The 12-week of aerobic exercise training increased peak oxygen uptake. The GHQ score and Carotid Β-Stiffness Index were decreased after the 12-week period in the aerobic exercise training group; however, no significant improvements were observed in the control group. CONCLUSIONS: We conclude that 12 weeks of aerobic exercise enhance mental health and decrease arterial stiffness in healthy middle-aged and older adults.

Renal hemodynamics across the adult lifespan: Relevance of flow pulsatility to chronic kidney disease.

BACKGROUND: Elevated renal flow pulsatility may contribute to the pathogenesis of chronic kidney disease (CKD). The purpose of this study was to investigate the associations among age, renal flow pulsatility, and CKD biomarkers in non-CKD adults and CKD patients. METHODS: Non-CKD adults (n = 415) and CKD patients (n = 136) aged between 22 and 83 years underwent the renal blood flow measurement using duplex ultrasonography. Pulsatility index (PI) and resistive index (RI) were calculated to assess renal flow pulsatility. The CKD biomarkers such as urinary liver-type fatty acid-binding protein (L-FABP) and serum fibroblast growth factor 23 (FGF23) were measured from each participant. Aortic hemodynamic parameters were measured by applanation tonometry. RESULTS: In non-CKD adults, advancing age was associated with elevations of renal PI and RI which slowly increased during middle-aged (PI: ß = 0.14, RI: ß = 0.17) and accelerated in older adults (PI: ß = 0.34, RI: ß = 0.33). In CKD patients, age-related increases in renal PI and RI were observed only in the middle age group (PI: ß = 0.23, RI: ß = 0.26). Multivariate analysis demonstrated that renal PI and RI were independently associated with CKD biomarkers, including urinary L-FABP and serum FGF23, and aortic pulse pressure. CONCLUSIONS: Advancing age is associated with a progressive elevation of renal flow pulsatility which manifests during middle age and accelerates in later life. Moreover, elevated renal flow pulsatility is associated with the presence of CKD in each age group and also with biomarker levels that reflect CKD progression.

Relationship between physical activity and circulating fibroblast growth factor 21 in middle-aged and older adults.

OBJECTIVE: Circulating levels of fibroblast growth factor 21 (FGF21) increase with advancing age and may lead to the development of cardiometabolic diseases via impaired lipid and glucose metabolism. While physical activity can reduce these risks of cardiometabolic dysfunction, it remains obscure whether circulation FGF21 levels are influenced by physical activity. The purpose of this study was to investigate the relations between daily physical activities and circulating FGF21 levels in middle-aged and older adults. METHODS: In this cross-sectional study with 110 middle-aged and 102 older adults, circulating (serum) FGF21 levels were evaluated by enzyme-linked immunosorbent assay, and the time spent in light-intensity physical activity (LPA) and moderate-to-vigorous-intensity physical activity (MVPA) was assessed using a uniaxial accelerometer. RESULTS: Serum FGF21 levels in the older group (158 pg/mL) were significantly higher than those in the middle-aged group (117 pg/mL). When we examined the joint association of age (middle-aged or older) and MVPA (lower or higher than the median) groups, serum FGF21 levels in the older and higher MVPA group (116 pg/mL) were significantly lower than those in the older and lower MVPA group (176 pg/mL). However, there was no difference in serum FGF21 levels between the lower and higher MVPA groups in the middle-aged group. In multivariable liner regression analysis, serum FGF21 levels were independently determined by MVPA time after adjusting for potential covariates in older adults (ß = -0.209). CONCLUSIONS: These cross-sectional study findings indicate that the time spent in MVPA is an independent determinant of circulating FGF21 levels, and that an age-related increase in serum FGF21 levels may be attenuated by habitually performing MVPA. (250/250 words).

The impact of aerobic fitness on arterial stiffness and adrenal cortex hormones in middle-aged and older adults.

An increase in arterial stiffness with advance aging is a risk for cardiovascular disease. Cardiovascular dysfunction is associated with the imbalance of adrenal cortex hormones, especially with the cortisol/dehydroepiandrosterone sulfate (DHEAs) ratio. However, the impact of aerobic fitness on arterial stiffness and cortisol/DHEAs ratio is unclear. The aim of this study was to investigate the relationship between aerobic fitness, arterial stiffness, and cortisol/DHEAs ratio. A total of 198 middle-aged and older adults (aged 50-79 years old) participated in this study. The aerobic fitness evaluated by peak oxygen consumption (VO2peak), carotid-femoral pulse wave velocity (cfPWV) as an indicator of arterial stiffness, and serum cortisol and DHEAs and their ratio were measured. The subjects were divided into the lower (n = 100) and the higher (n = 98) aerobic fitness groups based on the median value of VO2peak. There were no significant differences in serum cortisol and DHEAs concentration alone between the lower and higher fitness groups. However, the cortisol/DEHAs ratio and cfPWV in the higher fitness group was smaller than in the lower fitness group (p < 0.05). The cortisol/DHEAs ratio was significantly correlated with cfPWV (r = 0.159, p < 0.05). These findings suggest that the cortisol/DHEAs ratio is associated with aerobic fitness and arterial stiffness in middle-aged and older adults.

Sedentary behaviour, physical activity, and renal function in older adults: isotemporal substitution modelling.

BACKGROUND: Physical inactivity and sedentary behaviour (too much sitting) can contribute to renal dysfunction. However, the potential benefits of behavioural change (e.g. replacing sedentary behaviour with physical activity) on renal function are not well understood. We used isotemporal substitution to model potential impacts of behaviours on renal function by replacing time spent in one behaviour to another. METHODS: In 174 older Japanese adults (age, 50-83 years; females, 76%), the time spent in sedentary behaviour, light-intensity physical activity (LPA), and moderate- to vigorous-intensity physical activity (MVPA) were assessed using an uniaxial accelerometer. Renal function was evaluated by the estimated glomerular filtration rate (eGFR) from serum creatinine and cystatin C levels. RESULTS: In univariate analyses, eGFR was significantly, albeit weakly, correlated with time spent in sedentary behaviour (rs = - 0.229), LPA (rs = 0.265), and MVPA (rs = 0.353). In the isotemporal substitution models, replacement of 30 min/day of sedentary behaviour with an equivalent LPA time was not significantly associated with eGFR (ß = 2.26, p = 0.112); however, replacement with an equivalent time of MVPA was beneficially associated with eGFR (ß = 5.49, p < 0.05). CONCLUSIONS: These cross-sectional findings suggest that sedentary behaviour (detrimentally) and physical activity (beneficially) may affect renal function and that replacing sedentary behaviour with MVPA may benefit renal health in older adults.

Association between duration of excessive weight and arterial stiffness in middle-aged and older adults.

This study aims to evaluate the association between duration of overweight/obesity and arterial stiffness. In total, 103 men and women aged 45-68 years with a body mass index (BMI) of ≥25 kg/m2 were enrolled in this study. Duration of overweight/obesity was calculated for individuals with at least two consecutive BMI occurrences of ≥25 kg/m2 in the previous (5-year intervals from 20 years old) and present BMI information. Multiple regression analysis showed that carotid-femoral pulse wave velocity, an index of arterial stiffness, was independently associated with the duration of overweight/obesity, but not with current degree of overweight/obesity.

Incremental short maximal exercise increases urinary liver-type fatty acid-binding protein in adults without CKD.

Exercise-induced redistribution of tissue blood flow decreases the renal blood flow in an exercise intensity-dependent manner. However, the acute effects of incremental short maximal exercise on renal tubular conditions remain unknown. The purpose of this study was to investigate the acute effects of incremental short maximal exercise on the urinary liver-type fatty acid-binding protein, which is a highly sensitive tubular biomarker that correlates excellently with peritubular capillary blood flow. A total of 116 adults (aged 24-83 years) without chronic kidney disease performed the incremental short maximal exercise using a cycling ergometer, wherein the exercise sequence consisted of commencing with a 2-min workout period at 20 W (as a warm-up period) and then followed by a 10-20 W increase every 1 minute until termination criteria were reached. Urinary samples were gathered before and immediately after the exercise to evaluate the concentrations of urinary creatinine, albumin, and liver-type fatty acid-binding protein. Urinary excretion levels of albumin and liver-type fatty acid-binding protein were significantly increased post-exercise (P < .001 and P = .008, respectively). Furthermore, the % change in urinary liver-type fatty acid-binding protein levels after exercise was found to correlate independently with age, estimated glomerular filtration rate at baseline, and the % change in urinary albumin (Model R2  = 0.451, P < .001). Our findings suggest that incremental short maximal exercise may lead to acute slightly adverse effects on tubular conditions, especially in young adults or adults with lower renal function, even without chronic kidney disease.

Role of High Physical Fitness in Deterioration of Male Sexual Function in Japanese Adult Men.

Male sexual function is regulated by vascular function and impaired vascular function is closely related with erectile dysfunction (ED). Vascular functions are positively influenced by physical fitness (i.e., aerobic capacity, muscle strength, and flexibility). The detailed associations between physical fitness and male sexual function remain poorly understood. The present study aimed to clarify the influence of physical fitness on male sexual function. In 177 adult men, peak oxygen consumption (VO2 peak), handgrip strength (HGS), and sit and reach were measured as indices of physical fitness. Arterial stiffness and erectile function were assessed by carotid-femoral pulse wave velocity (cfPWV) and the International Index of Erectile Function 5 (IIEF5) questionnaire, respectively. IIEF5 score was significantly correlated with VO2 peak ( rs = 0.52), HGS ( rs = 0.37), and cfPWV ( rs = -0.44); and multivariate linear regression analyses showed that VO2 peak, HGS, and cfPWV were significantly associated with IIEF5 score after considering confounders. The receiver operator characteristic curve analysis suggested that the cutoff values for predicting ED were 29.0 ml/min/kg for VO2 peak and 39.3 kg for HGS. The IIEF5 score was the highest in the subjects with the values of both VO2 peak and HGS were higher than their respective cutoff values, while the IIEF5 score was the lowest in the subjects with the values of both VO2 peak and HGS were lower than their respective cutoff values. These results suggest that the maintenance of high aerobic capacity and muscular strength may offset deterioration of male sexual function.

Combined effects of lactotripeptide and aerobic exercise on cognitive function and cerebral oxygenation in middle-aged and older adults.

Background: Age-related declines in cognitive function and cerebral perfusion increase the risk of dementia. Although nutrition and exercise may be effective in reducing cognitive decline, the effect of lactotripeptide (LTP) on cerebral oxygenation and hemodynamics remains unclear. Objectives: The aim of this study was to investigate the effects of LTP ingestion on cerebral oxygenation, cognitive function, and vascular function in middle-aged and older adults with or without an exercise intervention. Methods: We recruited 2 separate groups of participants, one with and one without an exercise intervention. Each group was then randomly assigned into a placebo group and an LTP group. The participants ingested a placebo or LTP every day. The exercise group performed aerobic exercises 4-6 d/wk. Before and after the 8-wk intervention, we measured oxygenated hemoglobin (oxy-Hb) concentration (oxy-Hb change) in the prefrontal cortex during the Stroop task (primary outcome), Stroop interference time, and carotid artery ß-stiffness (both secondary outcomes). Results: Sixty-four participants completed the study. Changes in oxy-Hb signal in the prefrontal cortex were greater in the LTP group than in the placebo group under both the exercise and nonexercise conditions (P < 0.05). In addition, the magnitude of improvement in the oxy-Hb change in the left prefrontal cortex was correlated with Stroop interference (r = -0.39, P < 0.05) and carotid ß-stiffness (r = -0.41, P < 0.05). Conclusions: An 8-wk intake of LTP increased cerebral oxygenation in the prefrontal cortex region in middle-aged and older adults, with and without exercise. The intervention-induced improvements in brain neural activation were associated with cognitive and vascular function. This trial was registered at www.umin.ac.jp as UMIN000022313.

Habitual exercise decreases plasma xanthine oxidoreductase activity in middle-aged and older women.

The aim of present study was to investigate the association between plasma xanthine oxidoreductase activity, which has gained attention as a novel preventive target of cardiovascular disease, and various physiological parameters and was to determine the effects of habitual exercise on plasma xanthine oxidoreductase activity in middle-aged and older women. In the cross-sectional study, we investigated the association between plasma xanthine oxidoreductase activity and various physiological parameters in 94 middle-aged and older women. In the interventional study, subjects (n = 22) were divided into two groups: exercise (n = 12) or the control group (n = 10), whereby we examined the effect of 12-week aerobic exercise training on plasma xanthine oxidoreductase activity in middle-aged and older women. The cross-sectional study demonstrated that plasma xanthine oxidoreductase activity was significantly associated with various physiological parameters, including visceral fat and daily step counts. In the interventional study, the plasma xanthine oxidoreductase activity significantly decreased after the 12-week aerobic exercise training, its changes were inversely associated with the changes in daily step counts. Our results revealed that the plasma xanthine oxidoreductase activity was associated with visceral fat accumulation and lack of exercise, and it was decreased by the aerobic exercise training.

Lactotripeptide ingestion increases cerebral blood flow velocity in middle-aged and older adults.

The age-related decrease in cerebral blood flow velocity increases the risk of cerebrovascular disease. Milk protein-derived bioactive peptides, e.g., lactotripeptide (LTP), have been shown to inhibit angiotensin converting enzyme activities and increase vasodilator production. We hypothesized that LTP ingestion increases cerebral blood flow velocity in middle-aged and older adults. In a randomized, placebo-controlled, double-blind design, 15 healthy middle-aged and older adults were assigned to either a LTP group or a placebo group. The subjects ingested LTP or placebo orally for 8 weeks. Before and after intervention, middle cerebral blood flow velocity was measured using transcranial Doppler ultrasonography. The baseline middle cerebral blood flow velocity and most other key dependent variables did not differ between the groups. LTP ingestion significantly increased middle cerebral blood flow velocity, but there was no such improvement in the placebo groups. We concluded that 8 weeks of LTP ingestion increased middle cerebral blood flow velocity in middle-aged and older adults.

Aerobic exercise training enhances cerebrovascular pulsatility response to acute aerobic exercise in older adults.

The brain's low resistance ensures a robust blood flow throughout systole and diastole and is susceptible to flow pulsatility. Increased cerebral pulsatility contributes to the progression of cerebrovascular disease. Although aerobic exercise affects vascular function, little is known about the effect of exercise on the cerebral pulsatility index in older adults. The aim of this study was to investigate the effect of exercise training on the post-exercise cerebral pulsatility response in older adults. Ten healthy older adults participated in a 12-week exercise training intervention. Before and after the intervention, we measured the pulsatility index of the middle cerebral artery by means of transcranial Doppler method at baseline and following a cycling exercise bout performed at an intensity corresponding to the ventilatory threshold. Before exercise training, there was no significant change in the cerebral pulsatility response to an acute bout of cycling exercise. However, after the intervention, cerebral pulsatility decreased significantly following 30 min of an acute cycling exercise (P < 0.05). This study demonstrated that cerebral pulsatility index did not change following an acute bout of cycling exercise at an intensity corresponding to ventilatory threshold, but that, after 12 weeks of exercise training, cerebral pulsatility index was reduced at 30 min after a single bout of cycling exercise. These results suggest that long-term aerobic exercise training may enhance the post-exercise reduction in pulsatility index in older adults.

Urinary liver-type fatty acid-binding protein is associated with subendocardial viability ratio in middle- and older-aged adults.

BACKGROUND: To identify one of the physiological underlying mechanisms of the predictive effects of urinary liver-type fatty acid-binding protein (L-FABP) for the onset of cardiovascular disease (CVD), we investigated the relationship between urinary L-FABP levels and subendocardial viability ratio (SEVR), a marker of myocardial perfusion, in middle- and older-aged adults. METHODS: This was a cross-sectional study of 249 middle- and older-aged adults (aged 46-83 years). We measured urinary L-FABP levels and central hemodynamic parameters, including SEVR, calculated by pulse wave analysis using an applanation tonometry. RESULTS: In the participants stratified in accordance with the tertiles of urinary L-FABP levels, SEVR decreased in a stepwise fashion with increasing tertiles (p < 0.001). Furthermore, this association remains significant after the consideration of various confounders. On the contrary, urinary albumin levels were not independently related with SEVR. CONCLUSION: Our results demonstrated that urinary L-FABP levels were independently associated with the SEVR of the middle- and older-aged adults. This result suggests that the increase in urinary L-FABP levels even within the normal range might be related to the decrease in myocardial perfusion (SEVR).

Impact of Age and Aerobic Exercise Training on Conduit Artery Wall Thickness: Role of the Shear Pattern.

Hemodynamic shear stress is the frictional force of blood on the arterial wall. The shear pattern in the conduit artery affects the endothelium and may participate in the development and progression of atherosclerosis. We investigated the role of the shear pattern in age- and aerobic exercise-induced changes in conduit artery wall thickness via cross-sectional and interventional studies. In a cross-sectional study, we found that brachial shear rate patterns and brachial artery intima-media thickness (IMT) correlated with age. Additionally, brachial artery shear rate patterns were associated with brachial artery IMT in 102 middle-aged and older individuals. In an interventional study, 39 middle-aged and older subjects were divided into 2 groups: control and exercise. The exercise group completed 12 weeks of aerobic exercise training. Aerobic exercise training significantly increased the antegrade shear rate and decreased the retrograde shear rate and brachial artery IMT. Moreover, changes in the brachial artery antegrade shear rate and the retrograde shear rate correlated with the change in brachial artery IMT. The results of the present study indicate that changes in brachial artery shear rate patterns may contribute to age- and aerobic exercise training-induced changes in brachial artery wall thickness.

Association between muscular strength and intrarenal vascular resistance in middle-aged and older individuals.

A strategy for the preservation of intrarenal vasculature conditions remains obscure in middle-aged and older individuals without the renal disease. In the present study, we sought to identify whether the maintenance of muscular strength is an effective method of preserving the intrarenal vasculature condition of middle-aged and older individuals. Therefore, we applied a cross-sectional approach for investigating the relationship between muscular strength and the condition of the intrarenal vasculature. In 169 middle-aged and older individuals without renal disease, handgrip strength (HGS) and the renal resistive index (RRI) were measured as the parameters of muscular strength and intrarenal vascular resistance, respectively. The RRI was elevated with aging (rs=0.499, P<0.001) and was inversely correlated with HGS (rs=-0.370, P<0.001). The relationship between RRI and HGS remained significant after the consideration of confounders, including age and various central hemodynamic parameters. Furthermore, when the individuals were divided into four groups according to age (middle-aged or older) and the median HGS values, the RRI exhibited the highest values in the older group with lower HGS values (P<0.001). Our findings indicate that muscular strength as assessed by HGS is independently associated with the RRI (i.e. intrarenal vascular resistance) in middle-aged and older individuals. This finding suggests that the muscular strength may be one of the key factors to preserve the intrarenal vasculature condition.

Relationship between exercise capacity and urinary liver-type fatty acid-binding protein in middle-aged and older individuals.

BACKGROUND: The underlying mechanism linking the decline in exercise capacity with renal dysfunction remains unclear. Urinary liver-type fatty acid-binding protein (L-FABP) levels reflect the degree of peritubular capillary blood flow, an important factor for renal dysfunction with aging. The aim of this study was to examine the relationship between exercise capacity and urinary L-FABP levels. METHODS: This was a cross-sectional study of 187 middle-aged and older individuals (aged 50-83 years) without chronic kidney disease (CKD). We assessed urinary L-FABP levels, peak oxygen consumption ([Formula: see text]), and grip strength. RESULTS: Urinary L-FABP levels inversely correlated with both [Formula: see text] (r s = -0.349) and grip strength (r s = -0.485). When the participants were divided into four groups according to the median values of aerobic fitness and muscular strength ([Formula: see text] and grip strength), urinary L-FABP levels were the highest in participants with lower levels of aerobic fitness and muscular strength (2.95 ± 1.43 µg/g creatinine) and the lowest in the participants with higher levels of aerobic fitness and muscular strength (1.33 ± 0.76 µg/g creatinine). The difference between the two groups was significant (P < 0.001). CONCLUSION: Our results demonstrate that both [Formula: see text] and grip strength were inversely associated with urinary L-FABP levels in middle-aged and older individuals without CKD. This suggests that a decline in exercise capacity is associated with a reduction in peritubular capillary blood flow, providing a novel insight into the underlying mechanism linking the decline in exercise capacity to the development of renal dysfunction.