Effects of exhaustive exercise on biochemical characteristics of sarcoplasmic reticulum from rat soleus muscle

This study examined the effects of acute high-intensity and moderate-intensity exercise on Ca2+-stimulated adenosine triphosphatase (ATPase) activity and the Ca2+ and ATP dependence of Ca2+-ATPase of the sarcoplasmic reticulum (SR) in the soleus muscle. The rats were run on 10% grade at 50 m min(-1) or 25 m min(-1) until fatigued (avg. time to exhaustion 2.8 and 87.7 min, respectively). The catalytic activities of SR Ca2+-ATPase were significantly depressed immediately after both types of exercise. Kinetic analyses demonstrated that the Ca2+ affinity of Ca2+-ATPase was elevated by both types of exercise adopted in the present investigation whereas the increase in the ATP affinity was brought about by only high-intensity exercise. These results suggest that exhaustive exercise may induce in slow-twitch muscle fibre the environmental changes, which adversely affect SR Ca2+-ATPase activity and can overcome the positive influence arising from the increase in the Ca2+ and/or ATP affinities of SR Ca2+-ATPase.     

A digest of the Evidence-Based Clinical Practice Guideline for Nephrotic Syndrome 2020

Clinical and Experimental Nephrology -     

An autopsy-proven case of myeloperoxidase-antineutrophil cytoplasmic antibody-positive polyarteritis nodosa with acute renal failure and alveolar hemorrhage

An 80-year-old woman positive for myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) was admitted with a 3-month history of fever, general malaise, and weight loss, after unsuccessful treatment with antibiotics. Upon admission, her fever persisted, and there was concomitant deterioration of renal function without active urine sediments. Furthermore, she developed hemoptysis, and chest computed tomography (CT) scan revealed bilateral diffuse alveolar hemorrhage. Although a renal biopsy was not performed because of her dementia, we initially suspected microscopic polyangiitis (MPA) on the basis of her clinical course. Because of her poor general condition, she was administered a low dose of prednisolone. Although her fever subsided, she suffered from intractable alveolar hemorrhage and eventually died from respiratory failure. During the autopsy, fibrinoid necrosis was restricted to medium-sized arteries, including the arcuate arteries of the kidneys and the bronchial arteries, without necrotizing crescentic glomerulonephritis and alveolar capillaritis. Therefore, polyarteritis nodosa (PAN) was diagnosed. It is important to distinguish between MPA and PAN because they can lead to life-threatening complications, and their treatment strategies and prognosis are different. When a patient presents with MPO-ANCA, alveolar hemorrhage, and acute renal failure with little evidence of glomerulonephritis, a differential diagnosis of PAN should be made; however, it is difficult to do so without pathological findings. Therefore, pathological examination should be carried out whenever possible.     

Hypomagnesemia in type 2 diabetic nephropathy: a novel predictor of end-stage renal disease

OBJECTIVE

There is now growing evidence that magnesium (Mg) deficiency is implicated in type 2 diabetes and its complications. However, it has not been fully elucidated whether hypomagnesemia is a predictor of end-stage renal disease (ESRD) in type 2 diabetic nephropathy.

RESEARCH DESIGN AND METHODS

This retrospective cohort study included 455 chronic kidney disease (CKD) patients (144 with type 2 diabetic nephropathy and 311 with nondiabetic CKD) who were hospitalized at Osaka General Medical Center for a CKD educational program between April 2001 and December 2007. The primary outcome was progression to renal replacement therapy. Participants were categorized based on serum Mg level into Low-Mg (serum Mg level ≤1.8 mg/dL) and High-Mg (serum Mg level >1.8 mg/dL) groups with the previously published normal lower limit chosen as the cutoff point.

RESULTS

Of the subjects with type 2 diabetic nephropathy, 102 progressed to ESRD during follow-up (median, 23 months). A multivariate Cox proportional hazards model showed that after adjustment for various demographic factors and laboratory data, the Low-Mg group had a 2.12-fold higher risk of ESRD than the High-Mg group (95% CI 1.28–3.51; P = 0.004). In contrast, 135 of the nondiabetic CKD subjects progressed to ESRD during follow-up (median, 44 months). No significant difference in outcome was found between the Low- and High-Mg groups of this population (adjusted hazard ratio, 1.15; 95% CI 0.70–1.90; P = 0.57).

CONCLUSIONS

Hypomagnesemia is a novel predictor of ESRD in patients with type 2 diabetic nephropathy.Magnesium (Mg) is the fourth most abundant cation in the human body and plays a key role in many fundamental biological processes, including energy metabolism and DNA synthesis. Mg deficiency has been shown to cause endothelial cell dysfunction, inflammation, and oxidative stress, which are major contributors to atherosclerosis (1–3). Some epidemiologic studies have reported associations between low Mg intake or serum Mg level and hypertension, coronary artery disease, and ischemic stroke (4–6).Mg and type 2 diabetes have a close relationship. Approximately one-third of patients with type 2 diabetes have hypomagnesemia, mainly caused by enhanced renal excretion (7). Mg deficiency is associated with poor glycemic control, and Mg supplementation improves insulin sensitivity (8). Moreover, there is substantial evidence of associations between hypomagnesemia and various complications of type 2 diabetes, including neuropathy, retinopathy, foot ulcers, and albuminuria (9–12). The relationship between Mg deficiency and advanced type 2 diabetic nephropathy, however, remains to be fully elucidated. Pham et al. (13) reported that serum Mg level was significantly associated with the slope of inverse serum creatinine (SCr) in type 2 diabetes with near-normal renal function. However, they failed to show a significant association between hypomagnesemia and hard renal outcome (doubling of SCr and initiation of renal replacement therapy [RRT]), probably due to low statistical power (14). Therefore, the aim of the current study was to determine whether hypomagnesemia is a predictor of end-stage renal disease (ESRD) in patients with advanced type 2 diabetic nephropathy. We also compared the impact of hypomagnesemia on renal outcome in type 2 diabetic nephropathy with that in nondiabetic chronic kidney disease (CKD).     

Both low and high serum ferritin levels predict mortality risk in hemodialysis patients without inflammation

Background

Serum ferritin concentration >100 ng/mL was associated with a higher risk of death in hemodialysis patients in Japan, whereas such an association was less clear in hemodialysis patients in Western countries. Since Japanese dialysis patients are generally less inflamed than those in Western countries, inflammation may modify the association between serum ferritin and the adverse outcomes.

Methods

We performed an observational cohort study using data from 2606 Japanese hemodialysis patients who participated in the Dialysis Outcomes and Practice Patterns Study (DOPPS) III (2005–2008) or DOPPS IV (2009–2012). The predictor was serum ferritin category (<50, 50–99.9, 100–199.9, and ≥200 ng/mL), and the primary and secondary outcomes were all-cause mortality and cardiovascular hospitalization, respectively. C-reactive protein (CRP, cut-off by 0.3 mg/dL) and serum albumin (cut-off by 3.8 g/dL) were stratification factors related to systemic inflammation.

Results

After adjustment for relevant confounding factors, a U-shaped association was observed between serum ferritin and all-cause mortality in the group with low CRP levels, whereas such relationship was not significant in the high CRP counterparts. In contrast, we found a linear association between serum ferritin and cardiovascular hospitalization in the low CRP and high CRP groups commonly. Similar results were obtained when the total cohort was stratified by serum albumin.

Conclusions

Serum ferritin showed different patterns of association with all-cause mortality in hemodialysis patients with versus without inflammation, whereas its association with cardiovascular hospitalization was similar regardless of inflammatory conditions.

     

High Prevalence of Obstructive Sleep Apnea and Its Association with Renal Function among Nondialysis Chronic Kidney Disease Patients in Japan: A Cross-Sectional Study

Summary

Background and objectives

Obstructive sleep apnea (OSA) affects one of five adults in the general population. Although a high prevalence of OSA has been reported among dialysis patients, the association between nondialysis chronic kidney disease (CKD) and OSA has not been fully investigated. This cross-sectional study aimed to investigate the prevalence of OSA among nondialysis CKD patients in Japan and the association between renal function and OSA.

Design, setting, participants, & measurements

Consecutive nondialysis CKD patients hospitalized mainly for CKD educational program, regardless of their sleep complaints, were enrolled. The diagnosis of OSA and its severity were measured using a type 3 portable monitor.

Results

Overall (n = 100, 68.0% male, median age 66.5 years, body mass index [BMI] 23.1 kg/m², estimated GFR [eGFR] 28.5 ml/min per 1.73 m²), 65% were diagnosed as OSA: mild OSA (apnea-hypopnea index [AHI] 5.0 to 14.9) in 32%, moderate OSA (AHI 15.0 to 29.9) in 25%, and severe OSA (AHI ≥ 30.0) in 8%. Multivariate logistic regression analysis revealed that a 10-ml/min per 1.73 m² decrease in eGFR was associated with a 42% increased odds of OSA after adjustment for age, BMI, and diabetes mellitus. Moreover, in a generalized linear model, eGFR was inversely correlated with AHI after adjustment for covariates.

Conclusions

This study demonstrated a high prevalence of OSA among nondialysis CKD patients in Japan and that the increased risk of OSA was significantly associated with decreased GFR among these patients. Further investigations are warranted to determine OSA''s direct influence on cardiovascular disease.     

Changes in EMG characteristics and metabolic energy cost during 90-min prolonged running

This study quantified the interaction of integrated electromyography (iEMG) obtained from the vastus lateralis and the metabolic energy cost of running (C_r), an index to assess running economy, during 90-min prolonged running. The iEMG during running was divided into eccentric (ECC) and concentric (CON) phases using a force platform and a knee-joint goniometer. The ratio of ECC to CON (ECC/CON ratio) significantly decreased during 90-min prolonged running in novice distance runners, which would be explained by an increase in muscle activity during the CON phase of running. The average C_r value significantly increased during 90-min prolonged running. The individual's C_r values significantly correlated with the ECC/CON ratio (r = −0.702, P < 0.05). These results suggest that changes in the ECC/CON ratio and C_r value during prolonged running are associated.     

Critical determinants of endurance performance in middle-aged and elderly endurance runners with heterogeneous training habits

Summary The current investigation was designed to determine which factor or what combination of factors would best account for distance running performance in middle-aged and elderly runners (mean age 57.5 years SD±9.7) with heterogeneous training habits. Among 35 independent variables which were arbitrarily selected as possible prerequisites in the distance running performance of these runners, oxygen uptake at lactate threshold (LT) (r=0.781∼0.889), maximal oxygen uptake (r=0.751∼0.886), and chronological age (r=−0.736∼−0.886) were found to be the 3 predictor variables showing the highest correlations with the mean running velocity at 5 km (V _{5 km}), 10 km (V _{10 km}), and marathon (V _M). When all independent variables were used in a multiple regression analysis, any 3 or 4 variables selected from among at LT, chronological age, systolic blood pressure (SBP), atherogenic index (AI), and Katsura index (KI) were found to give the best explanation ofV _{5 km},V _{10 km}, orV _M in a combined linear model. Linear multiple regression equations constructed for predicting the running performances were:V _{5 km}=0.046X ₁−0.026X ₂−0.0056X ₃+5.17,V _{10 km}=0.028X ₁−0.028X ₂−0.190X ₄−1.34X ₅+6.45, andV _M=−0.0400X ₂−0.324X ₄−1.16X ₅+7.36, where at LT (ml·min⁻¹·kg⁻¹),X ₂ = chronological age,X ₃=SBP,X ₄=AI, andX ₅=KI. We suggest that distance running performance of middle-aged and elderly runners could be predicted with a relatively high accuracy by a single predictor of at LT or , or by a combination of either of these predictors with more easily measurable indices such as age, AI, KI, or SBP. The prediction equations which have been developed can be applied to a larger population of middle-aged and elderly runners. Data were collected at the Human Performance Laboratory, Hiroshima University     

Assessment of Short-Distance Breaststroke Swimming Performance with Critical Velocity

For high-velocity running or swimming, the relationship between velocity (v) and its sustainable duration (t) can be described by a hyperbolic relationship: (v - V_crit)·t = D’, where V_crit is termed critical velocity, and D’ is defined as a curvature constant of the hyperbolic curve. The purposes of this study were to examine whether the V_crit could be applied to evaluate short-distance breaststroke swimming performance and to evaluate the relative contribution of D’ in short-distance swimming performance. Eleven male swimmers performed a series of time trials corresponding to 75, 100, and 150-m in an indoor 50-m swimming pool. The observed records were calculated into average velocities of each event to determine V_crit and D’. After the determination of V_crit and D’, all subjects performed 50-m time trial on another day. A maximal anaerobic power test using cycle ergometer was also performed in the laboratory. The average velocity of the 50-m time trial significantly correlated with the obtained V_crit, but not with D’. D’ was significantly correlated with the residual error, calculated from the regression analysis for the relationship between V_crit and the average velocities of 50-m time trial. A cluster analysis showed that most of the subjects were classified as V_crit dependency when performing 50-m time trial. Those results indicated that V_crit could be applied to evaluate short-distance swimming performance, and it determined around 80% of the short-distance breaststroke swimming performance.

Key Points

• For high-velocity running or swimming, the relationship between velocity (v) and its sustainable duration (t) can be described by a hyperbolic relationship: (v - V_crit)·t = D’, where V_crit is termed critical velocity, and D’ is defined as a curvature constant of the hyperbolic curve. The D’ contributed only around 20% of the breaststroke swimming performance even in a short-distance event.
• Critical velocity determined around 80% of 50-m breaststroke swimming performance, and it could be a useful tool for evaluating short-distance swimming performance.
• Most of the swimmers showed characteristics for critical velocity dependent physical fitness even in short-distance swimming event.

Key words: Critical swimming velocity, D’, hyperbolic curve, cluster analysis     

Association Between Accumulation of Advanced Glycation End-Products and Hearing Impairment in Community-Dwelling Older People: A Cross-Sectional Sukagawa Study

Objectives

The experimental studies suggested the hypothesis that the accumulation of advanced glycation end-products (AGEs) could induce hearing impairment. The purpose of this study is to examine the hypothesis among elderly people using an epidemiologic approach.