Glutamine and ornithine alpha-ketoglutarate supplementation on malate dehydrogenases expression in hepatectomized rats

PURPOSE: To evaluate the relative gene expression (RGE) of cytosolic (MDH1) and mitochondrial (MDH2) malate dehydrogenases enzymes in partially hepatectomized rats after glutamine (GLN) or ornithine alpha-ketoglutarate (OKG) suplementation. METHODS: One-hundred and eight male Wistar rats were randomly distributed into six groups (n=18): CCaL, GLNL and OKGL and fed calcium caseinate (CCa), GLN and OKG, 0.5g/Kg by gavage, 30 minutes before laparotomy. CCaH, GLNH and OKGH groups were likewise fed 30 minutes before 70% partial hepatectomy. Blood and liver samples were collected three, seven and 14 days after laparotomy/hepatectomy for quantification of MDH1/MDH2 enzymes using the real-time polymerase chain reaction (PCR) methodology. Relative enzymes expression was calculated by the 2-ΔΔC T method using the threshold cycle (CT) value for normalization. RESULTS: MDH1/MDH2 RGE was not different in hepatectomized rats treated with OKG compared to rats treated with CCa. However, MDH1/MDH2 RGE was greater on days 3 (321:1/26.48:1) and 7 (2.12:1/2.48:1) while MDH2 RGE was greater on day 14 (7.79:1) in hepatectomized rats treated with GLN compared to control animals. CONCLUSION: Glutamine has beneficial effects in liver regeneration in rats by promoting an up-regulation of the MDH1 and MDH2 relative gene expression. .

Dietary restriction and triiodothyronine (T3) regulation of malate-aspartate shuttle enzymes in the liver and kidney of mice.

The activities of malate-aspartate shuttle enzymes viz., cytosolic and mitochondrial aspartate aminotransferase (c- and m-AsAT) and malate dehydrogenase (c- and m-MDH) were measured in liver and kidney of ad libitum (AL) and dietary-restricted (DR) mice and also on triiodothyronine (T3) treatment. The results show that the activity (U/mg protein) of c-AsAT is increased significantly in liver and the activities of c-MDH and m-AsAT are increased significantly in kidney during DR. On T3 treatment, the activities of both the isoenzymes (c- and m-) of MDH and AsAT are increased significantly in the liver of AL- and DR-fed mice. In the kidney, m-MDH showed no effect by T3 treatment, however, c-MDH increased significantly in both AL- and DR-fed mice. In contrast, m-AsAT is increased significantly in the kidney in AL-fed mice, but was not affected in DR-fed animals. In vitro reconstitution of malate-aspartate shuttle showed a higher activity in the liver and kidney of DR-fed mice, as compared to AL-fed ones and also in the T3-treated mice, compared to untreated ones. These findings suggest that malate-aspartate shuttle enzymes are differentially regulated during DR in mice, in order to adapt to the metabolic need of liver and kidney. T3 potentially regulates the shuttle enzymes, albeit to a varying degree in the liver and kidney of AL- and DR-fed mice.

Hydrocortisone and triiodothyronine regulation of malate-aspartate shuttle enzymes during postnatal development of chicken.

The normal endogenous level of malate-aspartate shuttle enzymes and its regulation by hydrocortisone and triiodothyronine were studied in the liver and kidney of 0-, 30- and 60-day old male Rhode Island Red (RIR) chicken. The endogenous activity of cytosolic malate dehydrogenase (c-MDH) was significantly higher in the liver of day 30 as compared to day 0 and 60. In contrast, mitochondrial malate dehydrogenase (m-MDH) activity decreased at day 60 in the liver. However, both c- and m-MDH had significantly lower activities at day 0, which increased sharply at day 30 and 60 in the kidney. On the other hand, activity of both cytosolic and mitochondrial aspartate aminotransferase (c- and m-AsAT) showed peak value at day 30 in both liver and kidney. Hydrocortisone administration induced c-MDH in the liver at all the ages studied, but did not influence the activity of the isoenzymes in the kidney whereas, it induced m-MDH in the liver at day 0 and in kidney at day 30. Administration of hydrocortisone, however, did not influence AsAT isoenzymes (c- and m-AsAT) in either of the tissues at any of the postnatal ages. Triiodothyronine induced c-MDH in the liver at all the ages whereas kidney isoenzyme was induced only at day 60. In contrast, m-MDH was induced by triiodothyronine in both liver and kidney at day 30 and 60. Administration of triiodothyronine did not influence c-AsAT of liver and kidney at either of the ages, whereas it induced m-AsAT of only liver at day 0 and 60. These findings indicated a tissue- and age-specific expression of the malate-aspartate shuttle enzymes in chicken and difference in the regulation exerted by hydrocortisone and triiodothyronine during postnatal development of chicken.

Short-term effects of thyroid hormones on lipogenic enzymes and 14C-acetate incorporation into various lipid classes: in vivo and in vitro studies.

Short-term effect of 3,5,3'-triiodothyronine (T3) and 3,5-diiodothyronine (T2) on lipid metabolism in the liver of Anabas testudineus was examined. In vivo injections of both T3 and T2 at a concentration of 10 ng/g body weight increased malic enzyme (ME), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) activity compared to 6-propylthiouracil (6-PTU) treated group. Treatment of 6-PTU results in the accumulation 14C-acetate into fat and thyroid hormones' treatment reduce it. In vitro experiments show that malic enzyme activity is augmented only by high concentration of T3 (10(-7) M) where as all concentrations of T2 increase its activity. In vitro studies with T3 showed a biphasic effect on cholesterol content. Conversely T2 in vitro, reduced cholesterol content with all concentrations. From these results it can be concluded that both T3 and T2 have short-term effect on lipid metabolism in Anabas.

Changes in lactate dehydrogenase and malate dehydrogenase activities during hypoxia and after temperature acclimation in the armored fish, Rhinelepis strigosa (Siluriformes, Loricariidae)

Lactate (LDH) and malate dehydrogenase (MDH) of white skeletal muscle of fishes acclimated to 20, 25 and 30 degrees Celsius and thereafter submitted to hypoxia were studied in different sbstrate concentrations. Significant differences for LDH and MDH of white muscle enzyme activities are described here for the first time in Rhinelepis strigosa of fishes acclimated to 20 degrees Celsius and submitted to hypoxia for six hours. LDH presented a significant decrease in enzyme affinity for pyruvate in acute hypoxia, for fishes acclimated to 20 degrees Celsius and an increase for fishes acclimated to 30 degrees Celsius.

Regulation of the expression of NADP-malic enzyme by UV-B, red and far-red light in maize seedlings

The induction of nicotinamide adenine dinucleotide phosphate-malic enzyme (NADP-ME) in etiolated maize (Zea mays) seedlings by UV-B and UV-A radiation, and different levels of photosynthetically active radiation (PAR, 400-700 nm) was investigated by measuring changes in activity, protein quantity and RNA levels as a function of intensity and duration of exposure to the different radiations. Under low levels of PAR, exposure to UV-B radiation but not UV-A radiation for 6 to 24 h caused a marked increase in the enzyme levels similar to that observed under high PAR in the absence of UV-B. UV-B treatment of green leaves following a 12-h dark period also caused an increase in NADP-ME expression. Exposure to UV-B radiation for only 5 min resulted in a rapid increase of the enzyme, followed by a more gradual rise with longer exposure up to 6 h. Low levels of red light for 5 min or 6 h were also effective in inducing NADP-ME activity equivalent to that obtained with UV-B radiation. A 5-min exposure to far-red light following UV-B or red light treatment reversed the induction of NADP-ME, and this effect could be eliminated by further treatment with UV-B or red light. These results indicate that physiological levels of UV-B radiation can have a positive effect on the induction of this photosynthetic enzyme. The reducing power and pyruvate generated by the activity of NADP-ME may be used for respiration, in cellular repair processes and as substrates for fatty acid synthesis required for membrane repair

Hormonal regulation of malate-aspartate shuttle enzymes during postnatal development of mice.

The regulation of malate-aspartate shuttle enzymes by hydrocortisone was studied in the liver and kidney of 15-, 30- and 60-day old mice. It has been observed that adrenalectomy decreases and hydrocortisone treatment to adrenalectomized mice increases the activity of cytosolic and mitochondrial malate dehydrogenase and cytosolic aspartate aminotransferase in the liver of 15-, 30- and 60-day old mice. Per cent decrease following adrenalectomy remained almost similar in all the postnatal ages studied. However, hydrocortisone effect shows age-dependency. In the kidney, adrenalectomy decreases and hydrocortisone treatment increases the activity of these isoenzymes only in 30- and 60-day old mice. These findings entail that the same enzyme in different tissues of developing animals may be regulated differentially by the same physiological stimuli. Our findings on hormonal regulation of malate-aspartate shuttle enzymes show that they are subjected to different physiological control in various tissues during postnatal development of mice.

Effect of fatty acid binding proteins on developing human placental malate dehydrogenase activity.

Role of fatty acid binding proteins (FABPs) in modulating inhibition of human placental malate dehydrogenase by palmitoyl-CoA and oleate has been studied. Activity of human placental cytosolic malate dehydrogenase is detected throughout the gestation, showing a peak at midgestation (20-25 weeks). Inhibition (50%) of the enzyme activity is obtained by 20 microM palmitoyl-CoA or 35 microM oleate. FABPs enhance the activity of malate dehydrogenase in absence of palmitoyl-CoA or oleate and also protect against palmitoyl-CoA or oleate inhibition. Such a modulatory effect of FABP may be due to the binding of long chain fatty acyl-CoA or fatty acid rather than a direct effect of FABPs on the enzyme.

Impact of protein deficiency and exposure to hexachlorocyclohexane or malathion on lipid metabolism in pregnant rats.

Dietary intake of three oral doses of hexachlorocyclohexane (HCH) (60 mg/kg body wt) or malathion (500 mg/kg) by normal and protein-deficient diet fed pregnant rats on the 6th, 10th and 14th day of gestation resulted in the impairment of lipid metabolism, viz. hypercholesterolemia and hypertriglyceridemia. The cholesterol, triglyceride and phospholipid contents in serum, brain, liver, kidney and uterus were increased significantly by HCH and malathion exposure, irrespective of the protein content in the diet. The incorporation of [1,2-14C]acetate into the hepatic lipids was stimulated by both HCH and malathion, suggesting a higher rate of lipid synthesis in the liver of normal and protein-deficient diet fed dams. The low protein content in the diet intensified the pesticide-induced changes and more severe alterations were noticed in HCH exposed dams than in malathion exposed dams.

Long-term treatment with 2,5-hexanedione has no effect on the specific activity of some brain and liver glycolytic enzymes of adult rats

Prolonged exposure to hexacarbon compounds is neurotoxic to humans and animals. As various hexacarbon compounds inhibit glycolytic enzymes in vitro, it has been suggested that this may underlie their neurotoxic effects in vivo. in the present investigation we examined whether long-term treatment with 2,5-hexanedione (200 mg/kg, sc) for 40 days affects the specific activity of brain and liver enolase, lactic dehydrogenase and malate dehydrogenase in female Wistar rats (150-170 g). Glycemia and liver glycogen levels were also determined. The specific activity of all enzymes tested, liver glycogen content and glycemia were not affected by chronic treatment with 2,5-hexanedione. Rats treated with 2,5-hexanedione weighed significantly less than control rats starting on day 18 of treatment (183 ñ 3.4G for the vehicle groups vs 171 ñ 3.2G for the 2,5-hexanedione group). 2,5-hexanedione also increased water intake (46 por cento when compared to vehicle-treated rats). prolonged treatmentof rats with the non-neurotoxic hexacarbon 1,6-hexanediol (207 mg/kg, sc) significantly increased liver glycogen content (5.9 ñ 0.6g/100g for the vehicle group vs 9.0 ñ 1.1g/100 g for the 1.6-hexanediol group) as well as food intake (44.0 ñ 1.5g 100g-1 6 days-1 for thge 1,6-hexanediol group). These results indicate that long-term treatment with 2,5-hexanedione did not alter the brain and liver glycolytic enzymes studied, liver glycogen content or glycemia but did reduce weight gain and increased water intake, whereas the administration of the reportedly non-neurotoxic hexacarbon 1,6-hexanediol has demonstrable metabolic effects

Effect of electropolarity treatment on activity levels of oxidative enzymes in gastrocnemius muscle of toad, Bufo melanostictus, during early stages of denervation.

The activity levels of succinate dehydrogenase (SDH), malate dehydrogenase (MDH) and cytochrome-C-oxidase showed a decrement whereas lactate dehydrogenase (LDH) evinced maximum activity during first 3 days of denervation. Under the impact of cathodal polarity treatment an elevation in the activity levels of these 4 enzymes was relatively more potent when compared to anodal polarity treatment. The role of polarity treatment in the regulation of these oxidative enzymes was discussed.

Características histoquímicas e estruturais do testículo do morcego hematófago (desmodus rotundus rotundus, Geoffrey, 1810) / Histochemical and structural characteristics of the testis of the vampire bat (desmodus rotundus rotundus, Geoffrey, 1810)

O estroma testicular do morcego hematófago, incluindo a cápsula testicular e a lâmina própria dos túbulos seminíferos, mostrou forte reatividade ao PAS. Esta reatividade foi possivelmente decorrente da grande quantidade de mucossubstância neutras (glicogênio e outros glicoconjugados), presentes aos níveis dos elementos estruturais da túnica albugínea e lâmina própria tubular, ou seja das fibras musculares lisas; células contráteis alongadas (mióides) e arranjos colágenos, fibrilares ou lamelares. Ao nível da lâmina própria, as membranas basais dos túbulos seminíferos se mostraram intensamente PAS-positivas, comprovando sua composiçäo predominante por mucossubstâncias neutras, de estruturaçäo complexa, previamente reportada (Malmi et al., 1987). O revestimento epitelial do complexo cavitário e superficial da rede testicular mostrou baixas reatividades para mucossubstâncias; proteínas e lipídios totais e enzimas oxidativas estudadas. Contudo, foi observada granulaçäo epitelial apical fortemente PAS-positiva na rede testicular, com hipótese de secreçäo glicoprotéica a este nível. As reaçöes de PAS, Sudan Black B, NADH, MDH e LDH no tecido intersticial testicular parecem se relacionar ao metabolismo esteróide (biossíntese e secreçäo) ao nível das células de Leydig. O epitélio seminífero, de forma gerla, demonstrou baixas reaçöes a todos os métodos histoquímicos utilizados. No entanto, no epitélio adbasal as localizaqçöes histoquímicas da NADH e LDH observadas se relacionaram possivelmente...

Relationship between the increase in liver nuclear triiodothyronine-receptor sites and malic enzyme activation by dexamethasone

Trabajos previos han demostrado que un exceso de glucocorticoides induce un incremento de la capacidad máxima de unión del receptor nuclear de T3 (MBC) y de la actividad de la enzima málica citosólica (EM), en hígado de rata. El objetivo de este trabajo fue analizar el grado de dependencia entre los cambios en el número de receptores nucleares de T3 y la inducción de una respuesta metabólica específica de T3 medida a través de la EM. La inyección de dosis diarias graduadas de dexametasona a animales adrenalectomizados (Ax) indujo un incremento en MBC y actividad de EM dependiente de la dosis, alcanzando valores máximos a una misma concentración de dexametasona. Los cambios en función del tiempo en MBC y actividad de EM luego de la administración de una dosis diarias de dexametasona, indicaron que ambos parámetros seguían un incremento progresivo en función del tiempo, el cual fue evidente 24 h después del glucocorticoide hasta alcanzar los niveles máximos. MBC y EM fueron medidas en ratas tiroidectomizadas (Tx) y Tx más Ax inyectadas con dexametasona (Tx+Ax+D). MBC incrementó significativamente en animales Ax tratados con dexametasona (Ax+D) y en Tx+Ax+D comparado con grupos controles normales y Tx. Por otra parte, la actividad de EM estuvo marcadamente disminuida en animales Tx y la administración de dexametasona al grupo Ax+Tx no incrementó la actividad enzimática como ocurrió en el grupo Ax, donde los niveles séricos de T3 estaban en el rango normal. Estos datos indican que: 1§) el incremento en la actividad de EM por administración de dexametasona estuvo asociado a un simultáneo incremento en el número de receptores nucleares hepáticos de T3. 2§) La dexametasona inyectada a animales hipotiroideos fracasó en la inducción de la EM tal como se encontró en animales de T3, sugiriendo una acción de dexametasona sobre la actividad de la EM mediada por T3 a través de una modificación del número de receptores nucleares de T3

Alterations in some dehydrogenase profiles of sciatectomized toad gastrocnemius muscle-metabolic modifications by malate.

Sciatectomized toad gastrocnemius has shown a progressive loss in lactate (LDH), succinate (SDH) and malate (MDH) dehydrogenase activities and elevation of glutamate dehydrogenase (GDH) activity during post-neurectemic days. The possible role of malate in the restoration of metabolic homeostasis in denervated muscle is discussed.

Alteration in some hepatic dehydrogenases and certain lipid components in thiamin deficiency.

An investigation was conducted to study the influence of thiamin deficiency on hepatic glucose-6-phosphate dehydrogenase, malic enzyme (NADP), lactate dehydrogenase and it's isoenzymes, total lipids, cholesterol and phospholipids in adult male albino rats. Typical thiamin deficiency symptoms developed in the 6th week. The specific activity of the said enzymes was significantly decreased in deficient rats as compared to pairfed controls. A significant drop in total lipid and phospholipid content was noted in deficient group while total cholesterol remained unchanged. Refeeding of control diet to deficient animals caused reversal of enzyme activities to normal.