Kiyohiko Kato

Oxidative muscular injury and its relevance to hyperthyroidism.

In experimental hyperthyroidism, acceleration of lipid peroxidation occurs in heart and slow-oxidative muscles, suggesting the contribution of reactive oxygen species to the muscular injury caused by thyroid hormones. This article reviews various models of oxidative muscular injury and considers the relevance of the accompanying metabolic derangements to thyrotoxic myopathy and cardiomyopathy, which are the major complications of hyperthyroidism. The muscular injury models in which reactive oxygen species are supposed to play a role are ischemia/reperfusion syndrome, exercise-induced myopathy, heart and skeletal muscle diseases related to the nutritional deficiency of selenium and vitamin E and related disorders, and genetic muscular dystrophies. These models provide evidence that mitochondrial function and the glutathione-dependent antioxidant system are important for the maintenance of the structural and functional integrity of muscular tissues. Thyroid hormones have a profound effect on mitochondrial oxidative activity, synthesis and degradation of proteins and vitamin E, the sensitivity of the tissues to catecholamine, the differentiation of muscle fibers, and the levels of antioxidant enzymes. The large volume of circumstantial evidence presented here indicates that hyperthyroid muscular tissues undergo several biochemical changes that predispose them to free radical-mediated injury.

Antioxidants in the serum of children with insulin-dependent diabetes mellitus

To determine whether alteration in serum antioxidant status is related to the increased oxidative stress as a cause of diabetic angiopathy, we measured both the antioxidant activity (AOA) and total peroxyl radical-trapping antioxidant parameter (TRAP), and their component individual antioxidants in serum of children with insulin-dependent diabetes mellitus (IDDM). The AOA was measured as the ability to inhibit lipid autoxidation in brain homogenates. TRAP was assayed as the ability to delay lipid peroxidation induced by an azo initiator. Antioxidants measured were ceruloplasmin, transferrin, and albumin as components of AOA; and ascorbic acid, uric acid, protein sulfhydryl, and alpha-tocopherol as components of TRAP. Serum AOA appeared to be decreased in the diabetics in relation to poor glycemic control, corresponding to the decrease in transferrin and albumin. Serum haptoglobin level was also decreased in the diabetics. Similarly, the directly measured TRAP value was decreased in the diabetic serum mainly due to the decreased contribution of unidentified chain-breaking antioxidants, despite the increase in ascorbic acid and alpha-tocopherol. The decrease in both types of antioxidant activity in the diabetic serum, as new findings, suggests that a defective serum antioxidant status contributes to the increased oxidative stress in IDDM.

Prenatal development of antioxidant enzymes in rat lung, kidney, and heart: Marked increase in immunoreactive superoxide dismutases, glutathione peroxidase, and catalase in the kidney

ABSTRACT: The immaturity of antioxidant capacity in the lung in preterm newborn infants is postulated to contribute to the development of hyperoxic lung injury. Antioxidant enzymes in fetal lung, comprised of copper-zinc (cytosolic) and manganese (mitochondrial) superoxide dismutases, glutathione peroxidase, and catalase, have been reported to increase during the late gestational period. To determine whether such maturation of antioxidant capacity occurs in other tissues, we have evaluated the development of these four enzymes from d 18 to 22 of gestation in rat lung, kidney, and heart. To resolve the confusion in the reported levels of lung superoxide dismutases, the two isoenymes were assayed separately by specific RIA. The growth of the kidney exceeded that of the whole body during this period, while the growth of the lung and heart did not. The concentrations of the four antioxidant enzymes in lung and kidney increased in a stepwise manner during this period, and the magnitude of the change for each enzyme was greater in the kidney than in the lung. On the other hand, the only significant change in the concentrations of heart antioxidant enzymes observed was a mild increase in the glutathione peroxidase concentration from d 20 to 22. These results suggest that the prenatal maturation of antioxidant capacity occurs earlier in the heart and later in the kidney than in the lung, and that the immaturity of antioxidant capacity could make the fetal rat kidney vulnerable to free radical-mediated injury.

Growth-hormone-induced changes in postheparin plasma lipoprotein lipase and hepatic triglyceride lipase activities.

A comparison of treated and untreated patients with growth hormone deficiency revealed that administration of growth hormone reduced lipoprotein lipase and hepatic lipase activities, total cholesterol, and high-density lipoprotein cholesterol concentrations. The possible significance of these results is discussed.

Antioxidant enzymes and lipoperoxide in blood in uremic children and adolescents

To determine whether oxidant-antioxidant balance is altered in chronic renal failure, antioxidant enzymes and lipid peroxide in peripheral blood cells and lipid peroxide in plasma were measured. Nine children and adolescents maintained on hemodialysis (HD), 9 on continuous ambulatory peritoneal dialysis (CAPD), and 14 controls were studied. Lipid peroxide was assayed fluorimetrically as thiobarbituric acid-reactive substances, superoxide dismutases by radioimmunoassays. Both manganese and copper-zinc superoxide dismutases in lymphocytes and monocytes in the HD and CAPD patients, and manganese superoxide dismutase in polymorphs in the HD patients were higher than in the controls. Copper-zinc superoxide dismutase, glutathione peroxidase, and catalase in erythrocytes were unaltered. The lipid peroxide level in plasma in the dialyzed patients was increased, whereas those in polymorphs and lymphocytes were unaltered. Triglyceride and total cholesterol in plasma in the dialyzed patients were also increased. The plasma lipid peroxide in the patients correlated with the triglyceride and total cholesterol level. This is the first study in which manganese superoxide dismutase is measured in nucleated cells of the patients with chronic renal failure. The present results suggest that increased superoxide dismutases protect against oxidative stress induced by chronic renal failure in nucleated cells but in neither erythrocytes nor plasma.

Effect of diabetes mellitus induced by streptozotocin on renal Superoxide dismutases in the rat: A radioimmunoassay and immunohistochemical study

SummaryTwo forms of Superoxide dismutase, CuZnSOD and MnSOD, have been investigated in the kidneys of streptozotocin-induced diabetic rats using both radioimmunoassay and immunoenzyme staining. The rats were killed 2, 8 and 12 weeks after the induction of diabetes mellitus and the kidneys excised. Two weeks after the induction of diabetes, the kidneys were hypertrophied because of the proliferation of renal tubular epithelium. However, the total CuZnSOD content of the kidneys did not increase and, because of the epithelial proliferation, the CuZnSOD concentration in each proximal tubular cell was decreased. Armanni-Ebstein lesions were found in the distal tubules 8 and 12 weeks after the induction of diabetes. The cells in these lesions were intensely stained for CuZnSOD, suggesting an adaptive response to the enhanced oxidative stress. The MnSOD staining in the thick ascending limbs of Henle’s loops was enhanced in the diabetic kidneys, while that in the cortical tubules was unaltered. MnSOD was assumed to increase in response to hypermetabolism associated with the proliferation of renal tubules. This was most marked in the cells which were rich in mitochondria, again suggesting an adaptive response to enhanced oxidative stress induced by diabetes mellitus. The glomeruli of both the diabetic and control groups were not stained for SODs, and no significant microscopic change was found even 12 weeks after the induction of diabetes mellitus.

Effect of Dexamethasone on Antioxidant Enzymes in Fetal Rat Lungs and Kidneys

To determine if an enhancement in the fetal antioxidant enzyme (AOE) system by maternal dexamethasone (DEX) is specific to organ and dose, the lung and kidney of pups, whose mother received DEX (0.2 or 2 mg/kg) twice, were obtained on days 19 and 20 of gestation. Low-dose DEX increased the four AOE in the day-19 lung, but not in day-20 lung. High-dose DEX decreased the copper-zinc superoxide dismutase (SOD) and glutathione peroxidase in the lungs. Thus, the DEX-induced maturation of lung AOE is dependent on dose and timing. DEX enhanced the four AOE in the day-19 kidney at both doses. In the day-20 kidney, DEX enhanced the manganese SOD at the low dose and also catalase at the high dose, suggesting that DEX accelerates the maturation of kidney AOE as well.

Immunohistochemical study on perinatal development of rat superoxide dismutases in lungs and kidneys

ABSTRACT: It has been reported that levels of antioxidant enzymes are low in fetal rat lungs and kidneys, and that they increase rapidly during late gestation. Among the antioxidant enzymes, both copper-zinc and manganese superoxide dismutases (CuZnSOD and MnSOD) are assumed to play a key role in protection against oxidative tissue injury. To determine the nature of the rapid perinatal increase in CuZnSOD and MnSOD, immunoenzyme staining was performed in the lungs and kidneys of fetal (d 18 and 20 of gestation) and neonatal (d 22) rats. The CuZnSOD and MnSOD in the homogenates were assayed by RIA, and they were found to be higher in the neonatal organs than in the respective fetal organs. The neonatal bronchiolar epithelium was stained for both CuZnSOD and MnSOD more intensely than the fetal one. The CuZnSOD staining in the neonatal alveolar wall was more intense than that in the fetal one. There was a significant reactivity for MnSOD in the neonatal, but not in the fetal, alveolar walls. In the kidneys, the reactivities for CuZnSOD and MnSOD were confined to the undifferentiated tubules. Although the tubules were increased in numbers in the neonatal kidneys, the intensity of the staining for both CuZnSOD and MnSOD was unchanged. The histo-chemical study disclosed that CuZnSOD and MnSOD increased in the kidneys in a manner different from that in the lungs. The low concentration of both CuZnSOD and MnSOD in the fetal lung tissues may contribute to the vulnerability to oxygen toxicity. Such changes in the concentrations is specific tissues were not delineated in the kidneys.

PEROXISOMAL OXIDASES IN VARIOUS TISSUES OF DIABETIC RATS

The effect of diabetes mellitus induced by streptozotocin on the activities of peroxisomal oxidases and H2O2-metabolizing enzymes, and lipid peroxidation in various rat tissues were investigated. Peroxisomal acyl-CoA oxidase, D-amino acid oxidase and L-alpha-hydroxyacid oxidase were measured by a sensitive spectrophotometric method using dichlorofluorescein/peroxidase as the detector of H2O2. Acyl-CoA oxidase activity was increased most markedly in the heart of diabetic rats, less markedly in the liver, and tended to be increased in the kidneys. The activities of other peroxisomal oxidases were much lower than that of acyl-CoA oxidase in the liver and kidneys, and were undetectable in the heart. Catalase activity was decreased in the liver and kidneys of diabetics, and was increased in the heart. Glutathione peroxidase activity was increased more markedly in the kidneys of the diabetics, and less markedly in the heart than in the liver. Lipid peroxide level was higher in the kidneys of the diabetics than in the controls, unchanged in the heart, and was lower in the liver of the diabetics than in the controls. Thus, peroxisomal beta-oxidation and the H2O2 production coupled with that, were activated in various tissues of diabetic rats, presumably as a part of the overall increase in lipid oxidation. However, they did not appear to contribute to the enhanced oxidative stress induced by diabetes mellitus.

Altered synthesis of renin in patients with insulin-dependent diabetes: plasma prorenin as a marker predicting the evolution of nephropathy☆

Plasma active renin (PARC) and plasma total renin (PTRC) were measured in 72 patients with childhood-onset IDDM and 37 control subjects in the supine posture. The diabetic patients were divided into three groups: group A, 55 patients with normoalbuminuria; group B, 11 patients with microalbuminuria; and group C, 6 patients with overt proteinuria. The levels of PTRC were 125 +/- 51, 240 +/- 124 and 580 +/- 285 ng/l in groups A, B and C, respectively; all of which were significantly higher than 114 +/- 33 ng/l in the control subjects. On the other hand, the ratios of plasma active to total renin, ARC/TRC, were 18.1 +/- 12.5, 10.7 +/- 6.7, and 2.9 +/- 1.4% in groups A, B and C, respectively; all of which were in turn significantly lower than 24.8 +/- 8.7% in the control subjects. Among the diabetic groups, PTRC became higher and ARC/TRC became lower in conjunction with the degree of albuminuria. The acute increments of PARC and PTRC during a standing load test were subsequently observed in 7 patients of group A, 5 of group B, 4 of group C, 13 patients with non-diabetic glomerulonephritis, and 6 control subjects. The ratios of increments of PARC to that of PTRC, delta ARC/delta TRC, were 48.3 +/- 22.3, 35.1 +/- 10.4 and 8.4 +/- 8.1% in groups A, B, C, respectively; all of which were significantly lower than 84.2 +/- 48.6% in the control subjects. Patients with non-diabetic glomerulonephritis showed, to a lesser degree, low ratio of delta ARC/delta TRC (60.4 +/- 37.9%) in conjunction with higher level of PTRC (249 +/- 89 ng/l).(ABSTRACT TRUNCATED AT 250 WORDS)