Intracardiac iron distribution in newborn guinea pigs following isolated and combined fetal hypoxemia and fetal iron deficiency

Myocardial iron deficiency complicates chronic intrauterine hypoxemia during diabetic pregnancies. To understand the effect of both conditions during fetal life on intracardiac iron prioritization, we measured heart myoglobin, cytochrome c, and elemental iron concentrations in six iron-deficient, hypoxic, five iron-sufficient, hypoxic, six iron-deficient, normoxic, and six iron-sufficient, normoxic newborn guinea pigs. The iron-deficient, hypoxic group had lower heart iron (p = 0.03) but higher myoglobin concentration (p < 0.0001) when compared with the iron-sufficient, normoxic group. The percentage of iron incorporated into myoglobin was higher than control in the iron-deficient, hypoxic group (23.2+/-7.2% vs. 5.2+/-0.8%; p < 0.001) and increased as total heart iron decreased (r = 0.97; p < 0.001). In contrast, heart cytochrome c concentration was lower than control in the iron-deficient, hypoxic group (p = 0.01), with equal percentages of heart iron incorporated into cytochrome c. This intracellular prioritization of myocardial iron to myoglobin and away from cytochrome c following combined fetal hypoxemia and iron deficiency may represent an adaptive mechanism to preserve myocardial tissue oxygenation, although at the expense of oxidative phosphorylative capability.     

Effect of dietary iron deficiency on mineral levels in tissues of rats

To clarify the influence of iron deficiency on mineral status, the following two synthetic diets were fed to male Wistar rats: a control diet containing 128 micrograms iron/g, and an iron-deficient diet containing 5.9 micrograms iron/g. The rats fed the iron-deficient diet showed pale red conjunctiva and less reactiveness than the rats fed the control diet. The hemoglobin concentration and hematocrit of the rats fed the iron-deficient diet were markedly less than the rats fed the control diet. The changes of mineral concentrations observed in tissues of the rats fed the iron-deficient diet, as compared with the rats fed the control diet, are summarized as follows: . Iron concentrations in blood, brain, lung, heart, liver, spleen, kidney, testis, femoral muscle, and tibia decreased; . Calcium concentrations in blood and liver increased; calcium concentration in lung decreased; . Magnesium concentration in blood increased; . Copper concentrations in blood, liver, spleen and tibia increased; copper concentration in femoral muscle decreased; . Zinc concentration in blood decreased; . Manganese concentrations in brain, heart, kidney, testis, femoral muscle and tibia increased. These results suggest that iron deficiency affects mineral status (iron, calcium, magnesium, copper, zinc, and manganese) in rats.     

Biochemical effects of mild iron deficiency and cold acclimatization on rat skeletal muscle

Most of the previous studies on the effects of iron deficiency on skeletal muscle respiratory capacity and work performance have been investigated in severe or moderate iron-deficiency anemia. We report here that even in mild iron deficiency where the hemoglobin concentration was 10 g/dl and the iron stores in livers and spleen were not completely depleted, a marked reduction in succinate dehydrogenase was observed in skeletal muscles but not in heart. Similarly, cytochrome oxidase activities were reduced. Although no significant change in glycerophosphate dehydrogenase was detected in the iron-deficient rats, exposure to cold in this group greatly reduced this enzyme activity. As cold acclimatization accelerates marrow erythropoiesis (20) which in turn, demands more iron, it seems that in the iron-insufficient state, this iron demand for marrow activity may persist at the expense of the tissue iron pool, resulting in a marked reduction in glycerophosphate dehydrogenase activities. Since succinate dehydrogenase plays a significant role in the impairment of mitochondrial function and early fatigue of iron-deficient muscle (11), the present study shows that even in mild iron deficiency, some loss of muscle functions could result as succinate dehydrogenase activities were greatly reduced.     

The pentose phosphate pathway and NADP-dependent glycerol-3-phosphate dehydrogenase activity in some tissues of albino rat]

The NADP-dependent glycerol-3-phosphate dehydrogenase activity in liver, heart and skeletal muscle of rat was studied. The activity is found when glyceraldehyde-3-phosphate or ribose-5-phosphate in the presence of ATP are taken as substrates. The data obtained confirm that NADP-dependent glycerol-3-phosphate dehydrogenase exists in skeletal muscle and demonstrate that it is found in heart muscle as well.     

Perturbation of mitochondrial composition in muscle by iron deficiency. Implications regarding regulation of mitochondrial assembly

It has been reported that the mitochondrial cytochromes and citrate cycle enzymes occur in constant proportions to each other and increase or decrease roughly in parallel in response to various stimuli. The purpose of this study was to determine whether this proportionality is an obligatory consequence of the way in which mitochondria are assembled. Severe iron deficiency was used to bring about decreases of the iron-containing constituents of the mitochondrial respiratory chain in skeletal muscle. Cytochrome c concentration and cytochrome oxidase activity were decreased approximately 50%, while succinate dehydrogenase and NADH dehydrogenase activities were decreased by 78% in iron-deficient muscle. On electron microscopic examination, mitochondria in iron-deficient muscles had relatively sparse numbers of cristae. The iron deficiency had little or no effect on the levels of a range of mitochondrial matrix enzymes, including citrate synthase, isocitrate dehydrogenase, fumarase, aspartate aminotransferase, 3-hydroxyacyl-CoA dehydrogenase, 3-ketoacid-CoA transferase, and acetoacetyl-CoA thiolase. These results show that the usual constant proportions between the constituents of the mitochondrial respiratory chain and matrix enzymes are not obligatory; they provide evidence that mitochondrial matrix enzymes and respiratory chain constituents can be incorporated into mitochondria independently and that the ratios between them can vary within wide limits.     

Effect of Resistance Exercise on Iron Status in Moderately Iron-Deficient Rats

Resistance exercise increases heme synthesis in the bone marrow, but it does not improve the hemoglobin status in severe iron-deficient rats on a diet containing less than 5?mg iron/kg. The current study investigated whether resistance exercise could mitigate hemoglobin status via increasing heme synthesis in moderately iron-deficient rats. Male 4-week-old Sprague-Dawley rats were fed an iron-deficient diet containing 12?mg iron/kg for 3?weeks. The rats were divided into two groups: a sedentary (S) group (n?=?7) or an exercise (E) group (n?=?7). The rats in the E group performed a climbing exercise (5?min?×?6?sets/day, 3?days/week). The aminolevulinic acid dehydratase activity, hematocrit, and hemoglobin tended to be higher in group E than S. The iron content in the flexor hallucis longus muscle was significantly higher in E than S, whereas the content in the liver, spleen, kidney, and heart did not significantly differ between the groups. Therefore, resistance exercise appears to improve hemoglobin via increasing heme synthesis in the bone marrow in moderately iron-deficient rats.     

Activity-induced adaptations in skeletal muscles of iron-deficient rabbits

The purpose of this study was to determine whether severe iron deficiency alters the adaptive response of skeletal muscle fibers to a sustained increase in tonic contractile activity. Seven weanling rabbits consumed a low iron diet and underwent phlebotomy twice weekly for 6 mo, resulting in severe anemia (mean Hb 5.5 g/dl). Compared with control animals, tibialis anterior skeletal muscles of iron-deficient animals exhibited reduced concentrations of cytochrome c (4.4 +/- 0.7 vs. 8.6 +/- 0.7 nmol/g tissue; P less than 0.01), and reduced activities of citrate synthase (83 +/- 10 vs. 133 +/- 13 mU/mg protein; P less than 0.01) and cytochrome-c oxidase (2.2 +/- 0.2 vs. 3.6 +/- 0.5 U/mg protein; P less than 0.05). In these muscles mitochondria were swollen and displayed deformed cristae. Less severe biochemical abnormalities were observed in cardiac and soleus skeletal muscles. Ten days of continuous electrical stimulation of the motor nerve supplying anterior compartment muscles of iron-deficient rabbits increased expression of mitochondrial proteins: cytochrome c was increased to 154% of control levels (P less than 0.05), and cytochrome-c oxidase and citrate synthase activities were increased to 199 and 272% of control levels, respectively (P less than 0.005). In addition, electrical pacing increased the fractional volume of mitochondria observed by electron microscopy and reduced the activity of aldolase A by 28% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of diet and of alloxan-diabetes on the activity of branched-chain 2-oxo acid dehydrogenase complex and of activator protein in rat tissues.

The total activities (sum of active and inactive forms) of branched-chain 2-oxo acid dehydrogenase complex in tissues of normal rats fed on a standard diet were (unit/g wet wt.): liver, 0.82; kidney, 0.77; heart, 0.57; hindlimb skeletal muscles, 0.034. Total activity was decreased in liver by 9%- or 0%-casein diets and by 48 h starvation, but not by alloxan-diabetes. Total activities were unchanged in kidney and heart. The amount of active form of the complex (in unit/g wet wt. and as % of total) in tissues of normal rats fed on standard diet was: liver, 0.45, 55%; kidney, 0.55, 71%; heart, 0.03, 5%; skeletal muscle less than 0.007, less than 20% (below lower limit of assay). The concentration of the active form of the complex was decreased in liver and kidney, but not in heart, by low-protein diets, 48 h starvation and alloxan-diabetes. In heart muscle alloxan-diabetes increased the concentration of active complex. The concentration of activator protein (which activates phosphorylated complex without dephosphorylation) in liver and kidney was decreased by 70-90% by low-protein diets and 48 h starvation. Alloxan-diabetes decreased activator protein in liver, but not in kidney. Evidence is given that in tissues of rats fed on a normal diet approx. 70% of whole-body active branched chain complex is in the liver and that the major change in activity occasioned by low-protein diets is also in the liver.     

Effects of iron repletion and correction of anemia on norepinephrine turnover and thyroid metabolism in iron deficiency

The reversibility of the alterations in norepinephrine (NE) content and turnover in interscapular brown adipose tissue and heart of iron-deficient rats has not been demonstrated. We therefore examined NE metabolism in age-matched male Sprague-Dawley rats depleted of iron by dietary means and after repletion with iron dextran. Heart NE content was 58, 61, and 85% of controls at 0, 3, and 7 days after repletion, whereas interscapular brown adipose tissue-NE content was 87, 103, and 104% of controls. Fractional heart NE turnover was 225% greater in iron-deficient anemics than controls but normalized within 3 days. Interscapular brown adipose tissue NE turnover was 58%, 46%, and 20% above controls in iron-deficient rats after 0, 3, or 7 days of iron repletion. Hematocrit returned to 80% of normal in 7 days. Liver triiodothyronine production also increased to 80% of control in this period. A second experiment used isovolemic exchange transfusion to examine the influence of anemia per se on these alterations in organ NE turnover. Acute correction of anemia in iron deficiency did not alter brown fat NE turnover. Heart NE turnover was significantly lower in anemic animals regardless of iron status. Defects in heart and brown fat NE metabolism are reversible within 7 days of iron treatment as are alterations in triiodothyronine production. Anemia per se has little effect on brown fat NE metabolism but does dramatically decrease heart NE content.     

Polyhydroxybenzoates inhibit ascorbic acid activation of mitochondrial glycerol-3-phosphate dehydrogenase: implications for glucose metabolism and insulin secretion

Glycerol-3-phosphate dehydrogenase from pig brain mitochondria was stimulated 2.2-fold by the addition of 50 microm l-ascorbic acid. Enzyme activity, dependent upon the presence of l-ascorbic acid, was inhibited by lauryl gallate, propyl gallate, protocatechuic acid ethyl ester, and salicylhydroxamic acid. Homogeneous pig brain mitochondrial glycerol-3-phosphate dehydrogenase was activated by either 150 microm L-ascorbic acid (56%) or 300 microm iron (Fe(2+) or Fe(3+) (62%)) and 2.6-fold by the addition of both L-ascorbic acid and iron. The addition of L-ascorbic acid and iron resulted in a significant increase of k(cat) from 21.1 to 64.1 s(-1), without significantly increasing the K(m) of L-glycerol-3-phosphate (10.0-14.5 mm). The activation of pure glycerol-3-phosphate dehydrogenase by either L-ascorbic acid or iron or its combination could be totally inhibited by 200 microm propyl gallate. The metabolism of [5-(3)H]glucose and the glucose-stimulated insulin secretion from rat insulinoma cells, INS-1, were effectively inhibited by 500 microm or 1 mm propyl gallate and to a lesser extent by 5 mm aminooxyacetate, a potent malate-aspartate shuttle inhibitor. The combined data support the conclusion that l-ascorbic acid is a physiological activator of mitochondrial glycerol-3-phosphate dehydrogenase, that the enzyme is potently inhibited by agents that specifically inhibit certain classes of di-iron metalloenzymes, and that the enzyme is chiefly responsible for the proximal signal events in INS-1 cell glucose-stimulated insulin release.     

Enzymatic and Ultrastructural Changes in Thoracic Muscles of Triatomine Insects during the Last Stages of Metamorphosis

Dipetalogaster maximus and Triatoma infestans are hematophagous insects, vectors of Chagas' disease. After the last molt of their metamorphosis, from fifth instar nymph to adult, they acquire wings and the ability to fly, which is important for their dispersal. Some biochemical changes accompanying this last stage have been studied by determining activity of hexokinase (EC 2.7.1.1), fructose-6-phosphate kinase (EC 2.7.1.11), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), glutamate dehydrogenase (EC 1.4.1.4), aspartate aminotransferase (EC 2.6.1.1), malate dehydrogenase (EC 1.1.1.37) and glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) in thoracic muscle extracts of fifth instar nymphs and adults. Activity of all the enzymes, expressed in U per mg protein, was significantly higher in muscles of adults than of nymphs, except that of aspartate aminotransferase, had lower activity in adults of T. infestans. The increase of glycerol-3-phosphate dehydrogenase activity was particularly striking (30-fold), while the increase in glucose-6-phosphate dehydrogenase activity was of a lesser magnitude than those observed for other enzymes. Comparative ultrastructural studies of thoracic muscles showed that in adult preparations mitochondria were more numerous and larger in size, and presented more cristae than in muscles of fifth instar nymphs. The biochemical changes detected appear to be the expression of the adaptation of adult muscles for flight activity. Thus, adult muscles would have higher glycolytic and respiratory capacity than those of fifth instar nymphs. The operation of systems transferring hydrogen into mitochondria, especially that of the glycerophosphate shuttle, may be greatly increased in adult muscles.     

The activity of tissue enzymes in iron-deficient rat and man: an overview

The effects of iron deficiency in rat and/or man on iron-containing enzymes of different tissues is reviewed. Iron deficiency results in a decrease of skeletal muscle iron containing proteins e.g. myoglobin, cytochromes c, a + a3, and alpha-glycerophosphate oxidase. Iron deficiency produces a reduction in the activity of several respiratory enzymes in the mitochondrial fraction of cardiac muscle, particularly: NADH cytochrome c reductase, succinic cytochrome c reductase, succinic dehydrogenase and NADH ferricyanide oxidoreductase. The effects of iron deficiency on brain tissue is emphasized with respect to cytochromes, monoaminoxidase and amino acids metabolism. Host defence to infection (controversial data), decrease in body temperature, alteration of DNA synthesis, collagen and lipid metabolism, liver and gastrointestinal mucous cytochromes activity perturbations are discussed.     

Effects of iron deficiency upon the antibody response to influenza virus in rats

The effects of severe and moderate iron deficiency upon the antibody response to influenza virus were investigated in rats. Three groups of weanling male Wistar rats were fed one of two iron-deficient diets (5 mg and 15 mg iron/kg diet) or a normal iron-containing diet (35 mg iron/kg diet). A group of individually pair-fed rats was introduced with the low iron-consuming rats. The effects of the diets upon various iron status parameters were followed during the 4th, 5th, 6th, and 7th week of diet. After 4 weeks of feeding different diets, an intraperitoneal injection of inactivated influenza virus A/New Jersey/76 was performed and a recall injection was done at 5 weeks. Primary and secondary antibody responses were assayed. Rats were sacrificed at 7 weeks of diet. After 4 weeks of feeding different diets, the rats fed the 5 mg iron/kg diet were severely anemic and rats fed 15 mg iron/kg diet were moderately iron-deficient, as shown by their iron status parameters. Growth was delayed in anemic and matched pair-fed rats. A primary antibody response was almost nonexistent in all groups. Secondary antibody titers were significantly weaker in anemic rats than in ad libitum controls, but were not different from those of pair-fed rats. This response was similar in moderately iron-deficient, ad libitum, and pair-fed rats. These results show that antibody synthesis in response to the influenza virus vaccine is preserved in moderate iron deficiency but is reduced in severe anemia. The reduction in energy consumption associated with severe iron deficiency in the rat could play a part in the altered humoral response.     

Metabolic differentiation of homologous leg muscles of two aquatic birds at the level of enzymatic organization

The quantitative determination of succinic dehydrogenase (SDH), hexokinase (HK), phosphorylase, phosphofructokinase (PFK), glycerol-3-phosphate dehydrogenase (G-3-PDH) and lactate dehydrogenase (LDH) was carried out in the homologous leg muscles of two aquatic Birds. It appears that the leg muscle fibres of the coot, a surface swimmer are more oxidative in nature and appear to utilize glucose as source of energy. The leg muscles of the dabchick, a diving Bird, on the other hand, seem to depend on glycogen as source of energy. The relative activity levels of HK, phosphorylase and PFK support the accepted r?le of glycogen as primary substrate of carbohydrate catabolism in the leg muscles. The ratio of G-3-PDH/LDH in the leg muscles revealed that glycerol 3-phosphate cycle appears to be insufficient to account for the major part of NADH oxidation. However, the LDH activity is quite high in all the muscles. These results led us to believe that glycerol 3-phosphate cycle may function during rest, when the rate of glycolysis will be low.     

Effect of hypothyroidism on mitochondrial energy metabolism and nuclear synthesis of RNA in the liver of Cynomolgus monkeys

The effects of hypothyroidism and of replacement therapy with T4 or T3 were studied on the enzymatic activities of liver subcellular fractions isolated from Cynomolgus monkeys. Animals were sacrificed 20 days after thyroidectomy. In mitochondria, thyroidectomy decreased significantly the respiratory chain activity (succinate cytochrome c-reductase), the transfer of cytosolic reducing equivalents (glycerol-3-phosphate dehydrogenase) and the phosphorylating capacity (oligomycin-sensitive ATPase and state 3 respiratory rate). The activity of nucleolar and nucleoplasmic RNA polymerases dropped by about 50% in hypothyroid monkeys. In T4 (2.5 micrograms/kg/d) or T3 (1 microgram/kg/d) treated thyroidectomized animals, the iodothyronine concentrations and the activity of mitochondria and nuclei enzymes were halfway between normal and hypothyroid values. Thus, the mitochondrial effects of thyroidectomy in monkey are, as in rat, at least partly secondary to a decrease in nucleocytoplasmic protein synthesis.     

Dietary iron deficiency decreases serum osteocalcin concentration and bone mineral density in rats

We investigated the effects of dietary iron deficiency on bone metabolism by measuring markers of bone turnover in rats. Twelve 3-week-old male Wistar-strain rats were fed a control diet or an iron-deficient diet for 4 weeks. Dietary iron deficiency decreased hemoglobin concentration and increased heart weight. Serum osteocalcin concentration, bone mineral content, bone mineral density, and mechanical strength of the femur were significantly lower in the iron-deficient group than in the control group. These results suggested that dietary iron deficiency affected bone, which might have been due to a decrease in bone formation in rats.     

Effects of thyrotoxicosis on mitochondrial enzymes of rat soleus.

Cytochrome oxidase, glycerol-3-phosphate dehydrogenase, and succinate dehydrogenase were measured in mitochondrial fractions obtained from rat soleus muscle of control and 8 week T3 + T4 treated animals. Under these conditions of prolonged treatment, there is a five-fold increase in the specific activities of both cytochrome oxidase and glycerole-3-phosphate dehydrogenase. Significant increases in total cellular mitochondrial content and enzyme activities were observed in T3 + T4 treated animals as compared to controls. These results indicate that thyrotoxicosis can induce selective changes in mitochondrial enzymes in slow twitch red (Type I) muscle fibers.     

Enzyme activities in red and white muscles of guinea-pigs and rabbits indigenous to high altitude.

The activities of several enzymes functioning in different areas of fuel catabolism were measured under standardized conditions, using crude homogenates of sartorius and ventricular muscle from outbred guinea-pigs and rabbits indigenous to high or low altitude. The activities of sartorius and myocardium were found to reflect the metabolic patterns known to be associated with white and red muscle. Both species had right ventricular hypertrophy at high altitude. The enzyme activities in the high altitude guinea-pig were not significantly different from those in the sea level animals. In the high altitude rabbit, compared with the low altitude rabbit, the activities of glyceraldehyde-3-phosphate deydrogenase and phosphofructokinase were greater in both the sartorius and myocardium. In addition, mitochondrial glycerol-3-phosphate dehydrogenase activity was greater in the sartorius at high altitude, while aspartate aminotransferase and beta-hydroxyacylcoenzyme A dehydrogenase activities were greater in the myocardium at high altitude. Succinate dehydrogenase activity was comparable at the two altitudes for both tissues. There was a greater proportion of skeletal muscle type lactate dehydrogenase in the high altitude rabbit myocardium but no difference was found with the guinea-pig.     

Metabolic changes in the African fruit beetle,Pachnoda sinuata,during starvation

Specimens of the fruit beetle Pachnoda sinuata were starved for up to 30 days. The weight of the beetles declined consistently throughout the starvation period. Concentrations of carbohydrates and alanine in flight muscles, fat body and haemolymph decreased rapidly after onset of starvation, while the concentration of proline remained high. Whereas the lipid concentrations in the haemolymph did not change significantly upon starvation, the lipid content in flight muscles and fat body decreased significantly.Beetles that had been starved for 14 days responded to injection of Mem-CC, the endogenous neuropeptide from its corpora cardiaca, with hyperprolinaemia and a decrease in the alanine level, but no such effect was monitored after prolonged starvation of 28 days. Regardless of the period of starvation, Mem-CC injection could not cause hypertrehalosaemia or hyperlipaemia, although carbohydrates were increased in fed beetles after injection.Flight ability of beetles that had been starved for 15 or 30 days was apparently not impaired. During such periods, beetles used proline exclusively as fuel for flight as evidenced by the increase in the level of alanine in the haemolymph and decrease of the level of proline; the concentrations of carbohydrates and lipids remained unchanged.Activities of malic enzyme and alanine aminotransferase (enzymes involved in transamination in proline metabolism), glyceraldehyde-3-phosphate dehydrogenase (enzyme of glycolysis), 3-hydroxyacyl-CoA dehydrogenase (enzyme of beta-oxidation of fatty acids) and of malate dehydrogenase (enzyme of Krebs cycle) were measured in fat body and flight muscles. In flight muscle tissue the maximum activity of NAD(+)-dependent malic enzyme increased, while that of glyceraldehyde-3-phosphate dehydrogenase decreased during starvation, and malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase and alanine aminotransferase were unchanged. In fat body tissue, activities of NADP(+)-dependent malic enzyme and 3-hydroxyacyl-CoA dehydrogenase increased during food deprivation and activities of glyceraldehyde-3-phosphate dehydrogenase, malate dehydrogenase and alanine aminotransferase remained unchanged.     

Idebenone-induced recovery of glycerol-3-phosphate and succinate oxidation inhibited by digitonin

Digitonin solubilizes mitochondrial membrane, breaks the integrity of the respiratory chain and releases two mobile redox-active components: coenzyme Q (CoQ) and cytochrome c (cyt c). In the present study we report the inhibition of glycerol-3-phosphate- and succinate-dependent oxygen consumption rates by digitonin treatment. Our results show that the inhibition of oxygen consumption rates is recovered by the addition of exogenous synthetic analog of CoQ idebenone (hydroxydecyl-ubiquinone; IDB) and cyt c. Glycerol-3-phosphate oxidation rate is recovered to 148 % of control values, whereas succinate-dependent oxidation rate only to 68 %. We find a similar effect on the activities of glycerol-3-phosphate and succinate cytochrome c oxidoreductase. Our results also indicate that succinate-dependent oxidation is less sensitive to digitonin treatment and less activated by IDB in comparison with glycerol-3-phosphate-dependent oxidation. These findings might indicate the different mechanism of the electron transfer from two flavoprotein-dependent dehydrogenases (glycerol-3-phosphate dehydrogenase and succinate dehydrogenase) localized on the outer and inner face of the inner mitochondrial membrane, respectively.