Vitamin A levels in regenerating rat liver. Effects on microsomal drug metabolism

After being maintained on a vitamin A-deficient or complete diet for a period of five weeks, male Sprague-Dawley rats were subjected to a two-thirds partial hepatectomy (PH) or sham operation. The vitamin A content of the liver of vitamin A-deficient, PH rats was below the limit of detection (less than 1 microgram/g liver). Rats fed the control diet and subjected to PH had hepatic levels of vitamin A that were 37% and 49% lower 48 and 72 hours after surgery, respectively, when compared with sham-operated controls. Hepatic microsomal cytochrome P-450 levels were significantly reduced in PH rats fed the complete diet 48 hours after PH and in PH rats fed either the deficient or complete diet 72 hours after. Vitamin A deficiency alone significantly reduced cytochrome P-450 levels. A combination of vitamin A deficiency and PH had the most dramatic effect on cytochrome P-450 and aminopyrine N-demethylase, which reduced the activity to approximately 50% of the activities found in the sham-operated control group. PH resulted in the greatest reduction in the rate of disappearance of benzo[a]pyrene in the presence of liver microsomes prepared from vitamin A-deficient rats.     

Vitamin A deficiency modifies lipid metabolism in rat liver

Liver fatty acid metabolism of male rats fed on a vitamin A-deficient diet for 3 months from 21 d of age was evaluated. Vitamin A restriction produced subclinical plasma and negligible liver retinol concentrations, compared with the control group receiving the same diet with 4000 IU vitamin A (8 mg retinol as retinyl palmitate)/kg diet. Vitamin A deficiency induced a hypolipidaemic effect by decreasing serum triacylglycerol, cholesterol and HDL-cholesterol levels. The decrease of liver total phospholipid was associated with low phosphatidylcholine synthesis observed by lower [14C]choline incorporation into phosphatidylcholine, compared with control. Also, liver fatty acid synthesis decreased, as was indicated by activity and mRNA expression of acetyl-CoA carboxylase (ACC), and incorporation of [14C]acetate into saponified lipids. A decrease of the PPARalpha mRNA expression was observed. Liver mitochondria of vitamin A-deficient rats showed a lower total phospholipid concentration coinciding with a decrease of the cardiolipin proportion, without changes in the other phospholipid fractions determined. The mitochondria fatty acid oxidation increased by 30 % of the control value and it was attributed to a high activity and mRNA expression of carnitine palmitoyltransferase-I (CPT-I). An increase in serum beta-hydroxybutyrate levels was observed in vitamin A-deficient rats. Vitamin A deficiency alters the mitochondria lipid composition and also enhances fatty acid oxidation by modifying the production of malonyl-CoA, the endogenous inhibitor of CPT-I, due to decreased activity of liver ACC. The incorporation of vitamin A into the diet of vitamin A-deficient rats reverted all the changes observed.     

Expression of retinoic acid nuclear receptors and tissue transglutaminase is altered in various tissues of rats fed a vitamin A-deficient diet.

The effects of vitamin A nutritional status on the levels of expression of retinoic acid nuclear receptors (RAR), and the retinoic acid-responsive gene, tissue transglutaminase, were determined in rats. Weanling male Sprague-Dawley rats fed a vitamin A-deficient diet for approximately 7 wk developed vitamin A deficiency, as confirmed by the depletion of liver retinol and retinyl palmitate. Controls were fed the same diet supplemented with 24 mg/kg retinyl acetate. The levels of expression of RAR beta mRNA were approximately 80% lower in bladder, brain, liver, lung and trachea and those of RAR gamma mRNA were approximately 50% lower in bladder, lung and trachea of rats fed the vitamin A-deficient diet than in controls. The levels of expression of RAR alpha mRNA were approximately 90% lower in brain and approximately 30% greater in liver, kidney, intestine and lung of rats fed the vitamin A-deficient diet. Vitamin A deficiency also resulted in reduced expression of tissue transglutaminase in the bladder, lungs and trachea, which paralleled the effects observed for RAR beta and RAR gamma. When vitamin A-deficient rats were subsequently fed a retinol-deficient diet supplemented with retinoic acid for 4 wk, the expression of RAR (beta and gamma) and tissue transglutaminase returned to the control levels. These results indicate that vitamin A nutritional status in rats influences the expression of both RAR and tissue transglutaminase in certain tissues.     

Vitamin A deficiency injures lung and liver parenchyma and impairs function of rat type II pneumocytes

The purpose of this research was to determine the effects of vitamin A deficiency on liver and lung morphology and type II pneumocyte function. Weanling rats were fed a retinol-adequate (control) or -deficient diet for 6 wk. Average food intakes and body weights were not different between the vitamin A-deficient and -adequate rats. Histologic examination revealed that the lungs of vitamin A-deficient rats had less collagen in the adventitia of small caliber arteries and arterioles and in the alveolar septa, which appeared thinner than that of controls. Many areas of the lungs of the same rats were also emphysematous (increased size of air spaces distal to the terminal bronchiole, with thinning and partial or total destruction of septal wall). Content of elastin also was lower in the lung parenchyma, as well as in the small arteries and arterioles, but not in the larger ones. Peribronchial collagen was not affected by the deficient diet. Scattered inflammation was observed in most of the vitamin A-deficient rats; a mild inflammatory reaction also was seen in one of the controls. Vitamin A-deficient rats also exhibited hepatocyte vacuolization and mild inflammation in the liver, specifically in the periportal tracts. Surfactant synthesis and ornithine decarboxylase activity were significantly lower in type II pneumocytes isolated from vitamin A-deficient rats. In conclusion, our data provide evidence that vitamin A deficiency produces profound morphologic alterations in liver and lung parenchyma and impairs pneumocyte function.     

Vitamin B-12 deficiency increases the specific activities of rat liver NADH- and NADPH-linked aquacobalamin reductase isozymes involved in coenzyme synthesis

Rat liver contains both NADH- and NADPH-linked aquacobalamin reductases, which are involved in the synthesis of the vitamin B-12 coenzymes and are distributed in both the mitochondrial and microsomal membranes. To clarify the physiological roles of these hepatic enzymes, vitamin B-12-deficient rats were used to study the effect of the deficiency on the enzyme activities. Male rats fed a vitamin B-12-deficient diet for 11 wk developed a severe vitamin B-12 deficiency with a high urinary methylmalonate excretion (214.3 +/- 115.2 mumol/d) and approximately 96% lower hepatic vitamin B-12 content. Tissues of the vitamin B-12-deficient rats were assayed for NADH- and NADPH-linked aquacobalamin reductase activities. The specific activities of both enzymes in homogenates of liver, kidney or upper intestine were shown to be three- to 20-fold greater in the vitamin-deficient rats than in the control rats. In liver, the vitamin deficiency specifically elevated the specific activities of the mitochondrial NADH-linked and microsomal NADPH-linked enzymes. These are likely the isozymes involved in vitamin B-12 coenzyme synthesis.     

Effect of vitamin A deficiency on the immune response to epizootic diarrhoea of infant mice (EDIM) rotavirus infection in mice.

The effect of vitamin A deficiency on the immune response to epizootic diarrhoea of infant mice (EDIM) rotavirus was studied in mice. The virus was given by oral dosing or by intraperitoneal injection. For oral challenge, weanling mice were fed on either a control or vitamin A-deficient diet ad lib. or pair-fed the control diet to the intake of the vitamin A-deficient group. A fourth group was fed on the vitamin A-deficient diet ad lib. for 10 weeks and then refed the control diet for 2 weeks. On day 77, mice were each given 30 microliters EDIM rotavirus orally and the animals were killed and examined 1 week later. The delayed-type hypersensitivity (DTH) response to picryl chloride was measured as an index of cell-mediated immunity. For intraperitoneal challenge, weanling mice were fed on either the control diet or the vitamin A-deficient diet ad lib. or pair-fed the control diet to the intake of the vitamin A-deficient group. On day 77, mice were each injected intraperitoneally with 30 microliters EDIM rotavirus and 1 week later antibody production was measured. In both experiments the body-weight, liver and serum vitamin A levels of the vitamin A-deficient group were significantly lower than the control or pair-fed groups. Following oral dosing the serum antibody levels specific to rotavirus were statistically significantly lower in vitamin A-deficient animals than the control or pair-fed groups. Vitamin A-deficient mice also showed an impaired DTH response compared with the control and pair-fed animals. Animals refed vitamin A for a short period showed a partial restoration of the antibody response. Following intraperitoneal challenge no statistically significant changes were observed in the serum antibody levels between any of the dietary groups. It is concluded that vitamin A deficiency impaired antibody production when rotavirus was given orally. Vitamin A deficiency also impaired cell-mediated immunity.     

Effects of semistarvation on rat liver, kidney, and heart mitochondrial function.

Two groups of rats were provided simultaneously with a commercial stock diet for a period of 7 days. One group was fed ad libitum (control), and the other was restricted to one-fourth of the daily intake of control animals (semistarved). Body weight declined significantly in semistarved rats whereas body weight of controls increased over the 7-day period. The following were determined in vitro on mitochondria isolated from liver, kidney, and heart tissues of both groups: substrate-stimulated and DNP-uncoupled respiratory rates; specific acivities of the Krebs cycle dehydrogenases, and cytochrome c oxidase. Degradative effects of reduced food intake on mitochondrial function were observed. Uncoupled respiratory rates of liver and kidney mitochondria (using succinate as substrate) and heart mitochondria (using alpha-ketoglutarate and pyruvate) were lower. Also lower were activities of isocitrate dehydrogenase, NADP: isocitrate dehydrogenases, transhydrogenase, succinate dehydrogenase, and cytochrome c oxidase of heart mitochondria, transhdrogenase of liver mitochondria, and isocitrate dehydrogenase and transhydrogenase of kidney mitochondria. Such decreases in enzyme activities under conditions of dietary protein deficiency might have their basis in breakdown rates exceeding synthesis rates or result from partial inactivation of existing enzyme protein. Thus, there is evidence that responses to semistarvation of such parameters of mitochondrial function may differ among various tissues. In addition, liver and kidney citrate levels were lower and heart citrate level higher with semistarvation.     

The impact of vitamin a deficiency and repletion with retinol and β-carotene on concanavalin a-induced lymphocyte proliferation

Concanavalin A (Con A)-induced splenic lymphocyte proliferation was studied in young rats during vitamin A deficiency and after oral repletion with 1500 retinol equivalents (R.E.) of either retinyl palmitate (RP) or βC-carotene (βC). Initial studies, designed to optimize the proliferation assay, showed that the response of vitamin A-deficient rats was consistently delayed in comparison to control rats fed a vitamin A-adequate diet. The overall magnitude of the proliferative response in vitamin A-deficient rats was also somewhat reduced (≈34% less than that of the control group). After vitamin A-deficient rats were repleted with RP, the Con A-induced proliferative response of splenic lymphocytes resembled that of the control group in both magnitude and kinetics. However, in vitamin A-deficient rats repleted with βC, the delayed response to Con A persisted in some animals and the overall response was intermediate between that of vitamin A-deficient rats and either control rats or rats repleted with RP.     

Vitamin A levels in regenerating rat liver. Effects on microsomal drug metabolism

After being maintained on a vitamin A‐deficient or complete diet for a period of five weeks, male Sprague‐Dawley rats were subjected to a two‐thirds partial hepatectomy (PH) or sham operation. The vitamin A content of the liver of vitamin A‐deficient, PH rats was below the limit of detection (< 1 μg/g liver). Rats fed the control diet and subjected to PH had hepatic levels of vitamin A that were 37% and 49% lower 48 and 72 hours after surgery, respectively, when compared with sham‐operated controls. Hepatic microsomal cytochrome P‐450 levels were significantly reduced in PH rats fed the complete diet 48 hours after PH and in PH rats fed either the deficient or complete diet 72 hours after. Vitamin A deficiency alone significantly reduced cytochrome P‐450 levels. A combination of vitamin A deficiency and PH had the most dramatic effect on cytochrome P‐450 and aminopyrine N‐demethylase, which reduced the activity to approximately 50% of the activities found in the sham‐operated control group. PH resulted in the greatest reduction in the rate of disappearance of benzo[a]pyrene in the presence of liver microsomes prepared from vitamin A‐deficient rats.     

水溶性辅酶Q10与维生素E协同抗氧化作用研究

[目的]研究水溶性辅酶Q10与维生素E协同对老龄小鼠和D-半乳糖衰老模型小鼠的抗氧化作用。[方法]通过测定给药小鼠血液中或组织中超氧化物歧化酶（SOD）活性和丙二醛（MDA）的含量来研究水溶性辅酶Q10＋维生素E的抗氧化功能。[结果]老龄鼠组：与阴性对照组相比,辅酶Q10＋维生素E组能明显提高小鼠红细胞中SOD活力,MDA活性均不同程度下降;衰老模型组：与空白对照组和模型对照组相比,辅酶Q10＋维生素E组小鼠红细胞及肝脏组织中SOD活性有不同程度升高,MDA含量均有不同程度下降。[结论]辅酶Q10和维生素E具有协同作用,其抗氧化效果优于单独的维生素E。     

Vitamin A deficiency reduces insulin-like growth factor (IGF)-I gene expression and increases IGF-I receptor and insulin receptor gene expression in tissues of Japanese quail (Coturnix coturnix japonica)

The insulin-like growth factor (IGF) system is regulated by various stimuli, including hormones, growth factors and nutritional status. We examined the effects of vitamin A on components of the IGF system in Japanese quail. Male quail (1 d old) fed a vitamin A-deficient diet for 14 or 21 d developed vitamin A deficiency, as confirmed by a depletion of serum retinol and hepatic retinyl palmitate. Consuming the vitamin A-deficient diet for 14 d did not affect growth rate, but decreased the serum IGF-I concentrations by 22% compared with the control group. The decreased serum IGF-I levels were accompanied by 21-52% lower levels of IGF-I mRNA in the testis, lung, liver and heart, whereas IGF-I receptor (IGF-IR) and insulin receptor (IR) gene expressions were unaffected in these tissues. Continuous feeding of the vitamin A-deficient diet for 21 d retarded growth and further decreased the levels of serum IGF-I and tissue IGF-I mRNA. Serum IGF-I levels were reduced by approximately 50%; IGF-I mRNA levels were > 90% lower in the liver and lung and approximately 60% lower in the heart and testis. In contrast, levels of the IGF-IR and IR mRNAs were approximately 100% greater in some tissues examined. When vitamin A-deficient quail received a single injection of retinol or retinoic acid (0.1 mg/bird), tissue IGF-I, IGF-IR and IR gene expressions did not change after 4 h. These results suggest a possible physiologic role of the IGF system in mediating vitamin A-supported growth of Japanese quail.     

Vitamin A status and metabolism of benzo[a]pyrene in the rat

Male Sprague-Dawley rats were maintained on a vitamin A-deficient diet for a period of five weeks. At the end of that time, hepatic cytochrome P450 levels in vitamin A-deficient rats were 65% that of rats fed a complete diet. However, the hepatic rate of benzo[a]pyrene metabolism was significantly greater (2 times) in vitamin A-deficient rats compared with those fed a complete diet. The pattern of metabolites separable by thin-layer chromatography was similar in both groups of rats. Benzo[a]pyrene induced its own metabolism by a slightly greater amount in the vitamin-sufficient rats, but it was not to the level of the deficient group, although the levels of cytochrome P450 were still below those of the deficient rats. In discussing lung microsomes, benzo[a]pyrene pre-treatment of deficient rats resulted in slightly elevated levels of cytochrome P450 and a slightly greater rate of metabolism of benzo[a]pyrene compared with rats fed the complete diet.     

Influence of vitamin B2 deficiency on polychlorinated biphenyls-induced liver lipid peroxides formation in rats

The present study is carried out to explore whether the liver microsomal drug-metabolizing enzymes induced by PCB are associated with the PCB-induced liver lipid peroxide formation in rats. For this purpose, variations of the drug-metabolizing enzyme activities mediated by vitamin B2 deficiency were utilized. The administration of PCB to rats induced the liver microsomal cytochrome P-450 and vitamin B2 deficiency promoted the induction. The cytochrome b5 was also induced by PCB but no further induction by vitamin B2 deficiency was observed. The flavoenzyme, NADPH-cytochrome c reductase, was induced by PCB when the vitamin B2-supplemented PCB diet was fed to rats, but the activity of the enzyme was decreased by vitamin B2 deficiency and PCB further decreased the activity. The liver lipid peroxide levels increased in PCB groups with and without vitamin B2 compared with each PCB-free group, but the lipid peroxide level in vitamin B2-deficient PCB group was significantly lower than in vitamin B2-supplemented PCB group. From these results, the PCB-induced liver lipid peroxide formation was not necessarily related to the variations of the liver microsomal drug-metabolizing enzymes.     

The interaction of vitamin A deficiency and rotavirus infection in the mouse

Weanling mice were fed on a control diet ad lib., a vitamin A-deficient diet ad lib. or pair-fed to the intake of the vitamin A-deficient group. Vitamin A deficiency was induced by 63-70 d of age. On day 77 mice were given 30 microliters rotavirus/mouse orally and examined histologically 1 week later. There were no changes in relative liver weight in any of the groups, but following infection animals deficient in vitamin A showed a significant increase in spleen weight compared with the other groups. The relative weight of the thymus was reduced by vitamin A deficiency, in both non-infected and infected animals. The histology of the spleen, thymus and small intestine was similar in all three dietary groups before infection. The number of goblet cells per duodenal villus in vitamin A-deficient animals was significantly lower than that of control and pair-fed animals. In the small intestine of vitamin A-deficient animals, rotavirus infection caused dramatic changes to the mucosa, with almost complete destruction of the tips of the villi, but control and pair-fed animals had normal villi. It is concluded that although rotavirus infection and vitamin A-deficiency cause few changes alone, in their action together there is significant destruction of the mucosal barrier of the small intestine.     

Biochemical functions of coenzyme Q10.

Coenzyme Q is well defined as a crucial component of the oxidative phosphorylation process in mitochondria which converts the energy in carbohydrates and fatty acids into ATP to drive cellular machinery and synthesis. New roles for coenzyme Q in other cellular functions are only becoming recognized. The new aspects have developed from the recognition that coenzyme Q can undergo oxidation/reduction reactions in other cell membranes such as lysosomes. Golgi or plasma membranes. In mitochondria and lysosomes, coenzyme Q undergoes reduction/oxidation cycles during which it transfers protons across the membrane to form a proton gradient. The presence of high concentrations of quinol in all membranes provides a basis for antioxidant action either by direct reaction with radicals or by regeneration of tocopherol and ascorbate. Evidence for a function in redox control of cell signaling and gene expression is developing from studies on coenzyme Q stimulation of cell growth, inhibition of apoptosis, control of thiol groups, formation of hydrogen peroxide and control of membrane channels. Deficiency of coenzyme Q has been described based on failure of biosynthesis caused by gene mutation, inhibition of biosynthesis by HMG coA reductase inhibitors (statins) or for unknown reasons in ageing and cancer. Correction of deficiency requires supplementation with higher levels of coenzyme Q than are available in the diet.     

Changes in content of coenzyme Q10 in beef muscle, beef liver and beef heart with cooking and in vitro digestion

The goals of this study were to determine the contents and digestibility of coenzyme Q10 (CoQ10) in beef muscle, beef liver and beef heart, which are rich in coenzyme Q10, as well as the effects of cooking on coenzyme Q10 content. Coenzyme Q10 contents were found as 109.97 ± 1.54 μg/g in beef heart, 33.34 ± 1.43 μg/g in beef liver and 23.47 ± 1.06 μg/g in beef M. longissimus dorsi muscle. The lowest retention in coenzyme Q10 content was found as 69.42 ± 0.56% (p < 0.01) in beef heart after frying processing. Coenzyme Q10 retentions were also found as 76.38 ± 0.89% and 77.19 ± 1.09% after frying of beef liver and boiling of beef M. longissimus dorsi muscle, respectively. Digestibility of coenzyme Q10 in beef heart (65.84 ± 0.84%) and beef liver (68.17 ± 0.60%) was significantly higher than the digestibility of coenzyme Q10 in beef M. longissimus dorsi muscle (60.16 ± 0.53%) (p < 0.01).     

Comparative oral toxicity of coenzyme Q10 and its (2Z)-isomer in rats: single and four-week repeated dose toxicity studies

It has been reported that coenzyme Q10 (CoQ10) functions as an electron transfer carrier in mitochondria, and can produce an improvement in heart diseases such as congestive heart failure. Its (2Z)-isomer contains a cis-double bond at the 2-position of the decaprenyl side chain. As the original organic industrial synthesis of CoQ10 resulted in a product that contained a small amount of this isomer, the efficacy and safety of CoQ10 was determined using CoQ10 containing this isomer; however, no toxicity data have been reported for the (2Z)-isomer itself. Thus, we conducted single (2,000 mg/kg) and 4-wk repeated (1,000 mg/kg) oral dose toxicity studies in rats to compare the toxicological profiles of CoQ10 and its (2Z)-isomer. The two compounds displayed similar toxicological profiles, and it was concluded that neither CoQ10 nor its (2Z)-isomer produce toxic effects in rats in single or repeated doses.     

维生素A强化食用油改善大鼠免疫功能的实验研究

目的认识食用油强化维生素A对实验动物免疫功能的改善作用。方法建立大鼠维生素A缺乏模型,在食用油中强化维生素A6500μg/kg,按照大鼠饲料的正常油脂含量,将维生素A强化油混入饲料中,喂养4周后观察动物维生素A营养状况和有关免疫指标的变化。结果与对照组动物比较,维生素A缺乏引起动物肝脏和血清中的维生素A含量显著下降,胸腺和脾脏重量以及外周血淋巴细胞转化率明显减少,T细胞亚群(CD3、CD4、CD8)和细胞因子IL-1、IL-2含量显著降低,但测定的CD4/CD8比例和TNF-a水平未见明显变化。经过补充维生素A强化油4周,实验大鼠肝脏、血清的维生素A水平得到显著改善;T细胞亚群增加,细胞因子接近对照组水平;胸腺和脾脏重量虽然未能恢复正常,但出现增加趋势;而淋巴细胞转化率未见明显改善。结论维生素A强化食用油能够有效改善实验动物的维生素A营养状况和免疫功能。     

Effects of dietary vitamin A deficiency, retinoic acid and protein quantity and quality on serially obtained plasma and liver levels of vitamin A in rats.

Rats were fed vitamin A-deficient diets either alone, supplemented with retinoic acid (RA), or of limited protein quality or quantity (7%rice or 7% casein protein); one group was fed 7% rice protein supplemented with vitamin A. Plasma and liver levels of vitamin A were determined serially. Plasma levels in rats fed otherwise adequate vitamin A-deficient diets remained above 30 micrograms/dl until liver reserves were below 10 micrograms/g tissue, at which point plasma levels decreased in some but not all rats while liver levels continued to decline (at a slower rate) to levels as low as 3 micrograms/g. Supplementation with RA caused an immediate and sustained reduction of 15 to 20 micrograms/dl in circulating vitamin A. At 7% dietary protein, plasma levels of vitamin A remained above 30 micrograms/dl when casein protein was fed or when the rice protein diet was supplemented with dietary vitamin A, but not when the rice protein diet was fed without an exogenous source of the vitamin. A scheme is proposed suggesting possible regulatory mechanisms that might control homeostatic levels of plasma vitamin A.     

维生素A对大鼠免疫功能的影响

本实验在喂大鼠以维生素A缺乏的基本饲料的基础上,通过补充两倍于大鼠正常生理需要量的维生素A(400IU/100g基本饲料),研究了维生素A对机体免疫功能的影响,同时观察在这两种不同的维生素A营养状况下农药西维因的毒性作用。结果表明,补充维生素A可以提高血清总补体活性,降低血清溶菌酶含量,促进机体产生特异性的溶血素抗体;在维生素A营养缺乏的状态下,农药西维因可抑制特异性溶血素抗体的产生,而在维生素A营养充裕时,这种作用则消失。