Aspergillus oryzae CsyB catalyzes the condensation of two ß-ketoacyl-CoAs to form 3-acetyl-4-hydroxy-6-alkyl-α-pyrone.

The type III polyketide synthases from fungi produce a variety of secondary metabolites including pyrones, resorcinols, and resorcylic acids. We previously reported that CsyB from Aspergillus oryzae forms α-pyrone csypyrone B compounds when expressed in A. oryzae. Feeding experiments of labeled acetates indicated that a fatty acyl starter is involved in the reaction catalyzed by CsyB. Here we report the in vivo and in vitro reconstitution analysis of CsyB. When CsyB was expressed in Escherichia coli, we observed the production of 3-acetyl-4-hydroxy-α-pyrones with saturated or unsaturated straight aliphatic chains of C9-C17 in length at the 6 position. Subsequent in vitro analysis using recombinant CsyB revealed that CsyB could accept butyryl-CoA as a starter substrate and malonyl-CoA and acetoacetyl-CoA as extender substrates to form 3-acetyl-4-hydroxy-6-propyl-α-pyrone. CsyB also afforded dehydroacetic acid from two molecules of acetoacetyl-CoA. Furthermore, synthetic N-acetylcysteamine thioester of ß-ketohexanoic acid was converted to 3-butanoyl-4-hydroxy-6-propyl-α-pyrone by CsyB. These results therefore confirmed that CsyB catalyzed the synthesis of ß-ketoacyl-CoA from the reaction of the starter fatty acyl CoA thioesters with malonyl-CoA as the extender through decarboxylative condensation and further coupling with acetoacetyl-CoA to form 3-acetyl-4-hydroxy-6-alkyl-α-pyrone. CsyB is the first type III polyketide synthase that synthesizes 3-acetyl-4-hydroxy-6-alkyl-α-pyrone by catalyzed the coupling of two ß-ketoacyl-CoAs.

Effects of exercise training on nitric oxide synthase in the kidney of spontaneously hypertensive rats.

Exercise training is known to have antihypertensive effects in humans and animals with hypertension, as well as to exhibit renal protective effects in animal models of hypertension and chronic renal failure. However, the mechanisms regulating these effects of exercise training remain unclear. The present study examined the effects of exercise training on nitric oxide synthase (NOS) in the kidneys of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. Male SHR and WKY rats were randomly divided into a sedentary group and a treadmill exercise group for 8 weeks. Systolic blood pressure (SBP) was measured every 2 weeks by the tail-cuff method and urine and blood samples were collected after the exercise protocol. Nitric oxide synthase activity and protein expression and endothelial (e) NOS phosphorylation in the kidney were examined. Exercise training significantly lowered SBP, decreased urinary albumin excretion, thiobarbituric acid-reactive substances levels and renal NADPH oxidase activity, and increased creatinine clearance in SHR. Exercise training significantly increased plasma and urinary nitrate/nitrite, NOS activity and eNOS and neuronal NOS expression, but decreased eNOS phosphorylation at Ser(1177) and Thr(495) in kidneys of SHR and WKY rats. Renal NOS may be involved in the antihypertensive and renal protective effects of exercise training in SHR.

Exercise training upregulates nitric oxide synthases in the kidney of rats with chronic heart failure.

There is an interaction between heart and kidney diseases, which is a condition termed cardiorenal syndrome. Exercise training has cardioprotective effects, involving upregulation of endothelial (e) nitric oxide synthase (NOS) in the cardiovascular system. However, the effects of exercise training on NOS in the kidney with heart disease are unknown. The aim of the present study was to investigate whether exercise training upregulates NOS in the kidney, left ventricle and aorta of rats with chronic heart failure (CHF). Male Sprague-Dawley rats underwent left coronary artery ligation (LCAL) to induce CHF and were randomly assigned to sedentary or treadmill exercise groups 4 weeks after LCAL. Three days after exercising for 4 weeks, urine samples were collected for 24 h and blood samples were collected following decapitation. Nitric oxide synthase activity and protein expression were examined. Significant interactions between CHF and exercise training were observed on parameters of cardiac and renal function. Exercise training improved cardiac function, decreased plasma B-type natriuretic peptide levels, decreased urinary albumin excretion and increased creatinine clearance in CHF rats. Nitric oxide synthase activity, eNOS expression and neuronal (n) NOS expression were significantly decreased in the left ventricle and kidney of CHF rats. Exercise training significantly increased NOS activity and eNOS and nNOS expression. Upregulation of NOS in the kidney and left ventricle may contribute, in part, to the renal and cardiac protective effects of exercise training in cardiorenal syndrome in CHF rats.

Effects of exercise training on renal interstitial fibrosis and renin-angiotensin system in rats with chronic renal failure.

OBJECTIVE: To clarify the mechanisms of the renal protective effects of exercise training, we examined the effects of exercise training on the renal interstitial fibrosis and renin-angiotensin system (RAS) in rats with chronic renal failure. METHODS: Six-week-old male Sprague-Dawley rats were divided into three groups: sham operation; 5/6 nephrectomy + sedentary; 5/6 nephrectomy + exercise training. The 5/6 nephrectomy + exercise training group underwent treadmill running (20 m/min, 60 min/day, 5 days/week). After 12 weeks, renal function, histology and protein expression of collagen type I, transforming growth factor-ß1 (TGF-ß1), matrix metalloproteinase (MMP), tissue inhibitors of metalloproteinase (TIMP) and RAS components in the renal cortex were examined. RESULTS: Exercise training ameliorated the 5/6 nephrectomy-induced hypertension, proteinuria, renal dysfunction, glomerular sclerosis and renal interstitial fibrosis. 5/6 Nephrectomy increased the expression of collagen type I, TGF-ß1, MMP-2, MMP-9, TIMP-1, angiotensinogen, angiotensin-converting enzyme (ACE), (pro)renin receptor and angiotensin II type 1 receptor, and exercise training inhibited the 5/6 nephrectomy-increased expression of collagen type I, TGF-ß1, TIMP-1, angiotensinogen and ACE expressions. 5/6 Nephrectomy decreased the expression of renin, ACE2, angiotensin II type 2 receptor and Mas receptor, and exercise training inhibited the 5/6 nephrectomy-decreased expressions. CONCLUSION: These results indicated that exercise training attenuates the progression of glomerular sclerosis and renal interstitial fibrosis in chronic renal failure rats. The renal protective effects of exercise training may be mediated by ameliorating the renal collagen turnover and the exacerbation of renal RAS.

Chronic Running Exercise Alleviates Early Progression of Nephropathy with Upregulation of Nitric Oxide Synthases and Suppression of Glycation in Zucker Diabetic Rats.

Exercise training is known to exert multiple beneficial effects including renal protection in type 2 diabetes mellitus and obesity. However, the mechanisms regulating these actions remain unclear. The present study evaluated the effects of chronic running exercise on the early stage of diabetic nephropathy, focusing on nitric oxide synthase (NOS), oxidative stress and glycation in the kidneys of Zucker diabetic fatty (ZDF) rats. Male ZDF rats (6 weeks old) underwent forced treadmill exercise for 8 weeks (Ex-ZDF). Sedentary ZDF (Sed-ZDF) and Zucker lean (Sed-ZL) rats served as controls. Exercise attenuated hyperglycemia (plasma glucose; 242 ± 43 mg/dL in Sed-ZDF and 115 ± 5 mg/dL in Ex-ZDF) with increased insulin secretion (plasma insulin; 2.3 ± 0.7 and 5.3 ± 0.9 ng/mL), reduced albumin excretion (urine albumin; 492 ± 70 and 176 ± 11 mg/g creatinine) and normalized creatinine clearance (9.7 ± 1.4 and 4.5 ± 0.8 mL/min per body weight) in ZDF rats. Endothelial (e) and neuronal (n) NOS expression in kidneys of Sed-ZDF rats were lower compared with Sed-ZL rats (p<0.01), while both eNOS and nNOS expression were upregulated by exercise (p<0.01). Furthermore, exercise decreased NADPH oxidase activity, p47phox expression (p<0.01) and α-oxoaldehydes (the precursors for advanced glycation end products) (p<0.01) in the kidneys of ZDF rats. Additionally, morphometric evidence indicated renal damage was reduced in response to exercise. These data suggest that upregulation of NOS expression, suppression of NADPH oxidase and α-oxoaldehydes in the kidneys may, at least in part, contribute to the renal protective effects of exercise in the early progression of diabetic nephropathy in ZDF rats. Moreover, this study supports the theory that chronic aerobic exercise could be recommended as an effective non-pharmacological therapy for renoprotection in the early stages of type 2 diabetes mellitus and obesity.

Perception of urge-to-cough and dyspnea in healthy smokers with decreased cough reflex sensitivity.

BACKGROUND: Although cigarette smoking has been implicated as an important risk factor for the development of respiratory symptoms, the perceptional aspects of two symptoms in smokers have not been fully elucidated. Therefore, we simultaneously evaluated the cough reflex sensitivity, the cognition of urge-to-cough and perception of dyspnea in both healthy smokers and non-smokers. METHODS: Fourteen male healthy never-smokers and 14 age-matched male healthy current-smokers were recruited via public postings. The cough reflex sensitivity and the urge-to-cough were evaluated by the inhalation of citric acid. The perception of dyspnea was evaluated by Borg scores during applications of external inspiratory resistive loads. RESULTS: The cough reflex threshold to citric acid, as expressed by the lowest concentration of citric acid that elicited two or more coughs (C2) and the lowest concentration of citric acid that elicited five or more coughs (C5) in smokers was significantly higher than in non-smokers. The urge-to-cough log-log slope in smokers was significantly milder than that of non-smokers. There were no significant differences in the urge-to-cough threshold between non-smokers and smokers. There were no significant differences in perceptions of dyspnea between non-smokers and smokers. CONCLUSIONS: The study showed that decreased cough reflex sensitivity in healthy smokers was accompanied by a decreased cognition of urge-to-cough whereas it was not accompanied by the alternation of perception of dyspnea. Physicians should pay attention to the perceptual alterations of cough in smokers.

Gender differences in perceptions of urge to cough and dyspnea induced by citric acid in healthy never smokers.

BACKGROUND: The mechanism of the gender difference in cough reflex threshold has not been clearly elucidated. In the present study, we evaluated gender differences in the cough reflex threshold along with the perceptions of respiratory sensations, urge to cough, and dyspnea. METHODS: Nineteen male and 20 female healthy never smokers were recruited through public postings. The cough reflex threshold and the urge to cough were evaluated by inhalation of citric acid. The perception of dyspnea was evaluated by Borg scores during applications of external inspiratory resistive loads. RESULTS: The cough reflex threshold and suprathreshold to citric acid in women, as expressed by the log transformation of the lowest concentration of citric acid that elicited two or more and five or more coughs, was significantly lower than that in men. The urge-to-cough log-log slope in women (1.47 ± 0.81 point × L/g) was significantly steeper than in men (0.96 ± 0.28 point × L/g; P < .03). There were no significant differences in the urge-to-cough threshold estimated between men and women. The slope of the dyspnea Borg score change during the external inspiratory resistive loads is steeper in women (0.17 ± 0.04 point/cm H2O/L/s) than that in men (0.13 ± 0.05 point/cm H2O/L/s; P < .01). The urge-to-cough slope significantly correlated with the perception of dyspnea slope (r = 0.537; P < .01). CONCLUSIONS: The gender difference in cough reflex threshold accompanied the gender difference in amplification rate of respiratory sensations in the same direction. The higher central gain for common pathways for respiratory sensations may play a role in lower cough reflex threshold in women. Further studies are needed to elucidate this issue.