Site-specific effect of ascorbic acid deficiency on the structure and function of odontoblasts in the teeth of osteogenic disorder rat in vivo

The influence of chronic L-ascorbic acid (AsA) deficiency on dentinogenesis was examined in Osteogenic Disorder Shionogi (ODS) rat, which bear inborn lack of L-gulonolactone oxidase. Weanling male rats were kept on AsA-free diet for 4 weeks until all suffered from scurvy. Control rats were given AsA in drinking water. The dentin of molars and incisors of the scorbutic rats was thinner than that in control, except for the crown-analogue (enamel-related) of incisors. Predentin in scorbutic molars showed irregular thickness, and was almost lacking in roots. In the root-analogue (cementum-related) region of scorbutic incisors, dentin displayed metachromatic incremental lines, and the thickened predentin contained collagen fibrils of irregular diameter. The odontoblasts facing the affected regions contained dilated rough endoplasmic reticulum cisternae. In the crown-analogue of scorbutic incisors, however, dentin, predentin, and odontoblasts were comparable to those of controls. These data indicate that AsA deficiency differentially affects the synthetic and/or secretory activity of odontoblasts in ODS rat teeth in a site-specific manner. The regional differences implicate the presence of putative local factor(s) in the crown-analogue of incisors that might have compensated for AsA deficiency. The odontoblasts in the crown-analogue of incisors may have different requirements for AsA from those in molars and the root-analogue of incisors.     

Effects of glutamine administration on inflammatory responses in chronic ethanol-fed rats

The purpose of this study was to investigate the effects of glutamine supplementation on inflammatory responses in chronic ethanol-fed rats. Male Wistar rats weighing about 160 g were divided into five groups. Two groups were fed a normal liquid diet and three groups were fed a glutamine-containing liquid diet. After 1 week, one of the normal liquid diet groups was fed an ethanol-containing liquid diet (CE), and the other group served as the control (CC) group. At the same time, one of the glutamine-containing liquid diet groups was continually fed the same diet (GCG), but the other two groups were fed ethanol-containing diet supplemented with glutamine (GEG) or without glutamine (GE). The following items were analyzed: (1) liver function, (2) cytokine contents, and (3) hepatic oxidative stress. The activities of aspartate transaminase (AST) and alanine transaminase (ALT) and levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in the CE group had significantly increased. In addition, hepatic cytochrome P450 2E1 (CYP2E1) expression had significantly increased in the CE, GE and GEG groups. However, the activities of AST and ALT and levels of TNF-α and IL-1β in the GE group were significantly lower than those of the CE group. The results suggest that the plasma inflammatory responses of rats fed an ethanol-containing liquid diet for 7 weeks significantly increased. However, pretreatment with glutamine improved the plasma inflammatory responses induced by ethanol.     

Impaired development of mammary glands in scorbutic rats unable to synthesize ascorbic acid

The effects of ascorbic acid (AsA)-deficiency on the development of mammary glands were investigated using mutant rats (osteogenic disorder syndrome rats; ODS rats) with hereditary inability to synthesize AsA. Female ODS rats of 21 days old were castrated and divided into two groups. One group was given AsA in their drinking water, and the other was not. All the rats received a daily injection of oestradiol-17 beta and progesterone (EP) from day 28 to day 49 of age. After EP treatment, the concentrations of AsA in the mammary glands of rats not given AsA were less than one tenth of those of rats given AsA and the contents of hydroxyproline in the mammary glands of the former rats were about half of those in the latter. Furthermore, the concentration of serum prolactin in rats not given AsA was reduced to about one third of that in rats given AsA. After EP treatment, whole mounts of mammary glands showed that in rats not given AsA the development of ducts was impaired and there was extensive accumulation of endbuds. Consistent with this finding, EP injections did not increase the area of parenchyma in the mammary glands of rats not given AsA, whereas they increased it about 2-fold in rats given AsA. Moreover, after EP treatment the amount of alpha-lactalbumin was significantly less in the mammary parenchyma of rats not given AsA than in that of rats given AsA. On the other hand, AsA deficiency did not impair the response of the mammary cells to insulin or prolactin in terms of DNA synthesis and alpha-lactalbumin production. These findings indicate that AsA deficiency impaired the development of mammary glands. This effect may be partly attributable to a defect in collagen synthesis in the mammary glands and a decrease in the concentration of serum prolactin.     

Adaptational modification of serine and threonine metabolism in the liver to essential amino acid deficiency in rats

It is known that plasma serine and threonine concentrations are elevated in rats chronically fed an essential amino acid deficient diet, but the underlying mechanisms including related gene expressions or serine and threonine concentrations in liver remained to be elucidated. We fed rats lysine or valine deficient diet for 4 weeks and examined the mRNA expressions of serine synthesising (3-phosphoglycerate dehydrogenase, PHGDH) and serine/threonine degrading enzymes (serine dehydratase, SDS) in the liver. Dietary deficiency induced marked elevation of hepatic serine and threonine levels associated with enhancement of PHGDH mRNA expression and repression of SDS mRNA expression. Increases in plasma serine and threonine levels due to essential amino acid deficiency in diet were caused by marked increases in hepatic serine and threonine levels. Proteolytic responses to the amino acid deficiency may be lessened by storing amino radicals as serine and inducing anorexia through elevation of threonine.     

Portal hypertension produces an evolutive hepato-intestinal pro- and anti-inflammatory response in the rat

An inflammatory etiopathogeny can be suggested in portal hypertensive enteropathy since infiltration of the intestinal wall by mononuclear cells has been described in this condition. This work was carried out with the intention of shedding light on this matter. Male Wistar rats were divided into 4 control groups and 4 groups with partial portal vein ligation at 1, 2, 3 and 15 months. TNF-alpha, IL-1beta and IL-10 were quantified in liver and ileum by ELISA. CO and NO were measured in splanchnic and systemic vein by spectrophotometry and Griess reaction, respectively. Expression of constitutive and inducible isoforms of NO and HO were assayed by Western blot in liver and ileum. An increased hepatic release of proinflammatory mediators (TNF-alpha, IL-1beta and NO) associated with intestinal release of anti-inflammatory mediators (IL-10, CO) occurs in an early evolutive phase (1 month) of experimental portal hypertension. On the contrary, in the long-term (15 months), the increase in the intestinal release of proinflammatory mediators (TNF-alpha, IL-1beta) is associated with an increase in the hepatic release of anti-inflammatory mediators (IL-10, CO). These results suggest that experimental prehepatic portal hypertension presents changes in the serum and tissular (liver and small bowel) concentrations of mediators which are considered as pro- and anti-inflammatory.     

Zinc deficiency decreases plasma level and hepatic mRNA abundance of apolipoprotein A-I in rats and hamsters

The influence of Zn deficiency on the plasma level as well asthe hepatic and intestinal gene expression of apolipoprotein (apo) A-Iwas examined in rats and hamsters. Male Sprague-Dawley rats (8 wk old)and Golden Syrian hamsters (7 wk old) were assigned to three dietarytreatments: Zn adequate (ZA, 30 mg Zn/kg diet), Zn deficient (ZD,<0.5 mg Zn/kg diet), and Zn replete (ZDA, ZD animals fed the ZA dietfor the last 2 days). The dietary treatments lasted for 18 days forrats or 6 wk for hamsters. For the measurement of apoA-I mRNAabundance, hamster apoA-I cDNA was cloned from the small intestine. Thefull-length 905-base pair cDNA shared ~80% similarity with thehuman, rat, and mouse apoA-I cDNAs. Hepatic and plasma Zn levels werereduced in ZD animals but normalized in ZDA rats and increased in ZDAhamsters compared with ZA animals. Zn deficiency reduced plasma apoA-Iand hepatic apoA-I mRNA levels 13 and 38%, respectively, in ZD rats.The 2 days of Zn replenishment raised plasma apoA-I and hepatic apoA-ImRNA levels in ZDA rats by 34 and 28%, respectively, higher than ZArats. Similarly, these levels were decreased by 18 and 25%,respectively, in ZD hamsters but normalized in ZDA hamsters comparedwith ZA hamsters. In contrast to the alterations of hepatic apoA-I mRNAlevels, neither Zn deficiency nor subsequent Zn repletion producedalterations in the intestinal apoA-I mRNA abundance. Data from thisstudy demonstrated that Zn deficiency specifically decreases hepaticapoA-I gene expression, which may at least be partly responsible forthe reduction of plasma apoA-I levels.

     

Vitamin A deficiency modulates iron metabolism via ineffective erythropoiesis

Vitamin A modulates inflammatory status, iron metabolism and erythropoiesis. Given that these factors modulate the expression of the hormone hepcidin (Hamp), we investigated the effect of vitamin A deficiency on molecular biomarkers of iron metabolism, the inflammatory response and the erythropoietic system. Five groups of male Wistar rats were treated: control (AIN-93G), the vitamin A-deficient (VAD) diet, the iron-deficient (FeD) diet, the vitamin A- and iron-deficient (VAFeD) diet or the diet with 12 mg atRA/kg diet replacing all-trans-retinyl palmitate by all-trans retinoic acid (atRA). Vitamin A deficiency reduced serum iron and transferrin saturation levels, increased spleen iron concentrations, reduced hepatic Hamp and kidney erythropoietin messenger RNA (mRNA) levels and up-regulated hepatic and spleen heme oxygenase-1 gene expression while reducing the liver HO-1 specific activity compared with the control. The FeD and VAFeD rats exhibited lower levels of serum iron and transferrin saturation, lower iron concentrations in tissues and lower hepatic Hamp mRNA levels compared with the control. The treatment with atRA resulted in lower serum iron and transferrin concentrations, an increased iron concentration in the liver, a decreased iron concentration in the spleen and in the gut, and decreased hepatic Hamp mRNA levels. In summary, these findings suggest that vitamin A deficiency leads to ineffective erythropoiesis by the down-regulation of renal erythropoietin expression in the kidney, resulting in erythrocyte malformation and the consequent accumulation of the heme group in the spleen. Vitamin A deficiency indirectly modulates systemic iron homeostasis by enhancing erythrophagocytosis of undifferentiated erythrocytes.     

Evidence for the absence of participation of the microbial flora in the hypocholesterolemic effect of guar gum in gnotobiotic rats

Germ-free (GF) and heteroxenic (Hx) rats were given a hypocholesterolemic diet (Hyper) with or without 5% guar gum (GG) for 4 weeks. The GF and Hx rats fed GG diets showed a lower hepatic and plasmatic cholesterol level when compared with Hyper groups. This reduction of cholesterolemia was due to a decrease in the chylomicron + very low density lipoprotein (VLDL) fraction. The caecal and portal concentrations of propionate were 30% higher in Hx rats fed the GG diet than in Hx rats fed the Hyper diet. These results exclude the participation of the intestinal microflora in the hypocholesterolemic effect of GG, and show that guar gum nullifies the effect of the hypocholesterolemic diet in the GF rats.     

Ascorbic acid deficiency decreases hepatic cytochrome P-450, especially CYP2B1/2B2, and simultaneously induces heme oxygenase-1 gene expression in scurvy-prone ODS rats

The mechanisms underlying the decrease in hepatic cytochrome P-450 (CYP) content in ascorbic acid deficiency was investigated in scurvy-prone ODS rats. First, male ODS rats were fed a diet containing sufficient ascorbic acid (control) or a diet without ascorbic acid (deficient) for 18?days, with or without the intraperitoneal injection of phenobarbital. Ascorbic acid deficiency decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial cytochrome oxidase (COX) complex IV subunit I protein, and simultaneously increased heme oxygenase-1 protein in microsomes and mitochondria. Next, heme oxygenase-1 inducers, that is lipopolysaccharide and hemin, were administered to phenobaribital-treated ODS rats fed sufficient ascorbic acid. The administration of these inducers decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial COX complex IV subunit I protein. These results suggested that the stimulation of hepatic heme oxygenase-1 expression by ascorbic acid deficiency caused the decrease in CYP content in liver.     

The effect of dietary copper on rat plasma apolipoprotein B,E plasma levels,and apolipoprotein gene expression in liver and intestine

The plasma levels of apo B and apo E, and the level of hepatic and intestinal mRNA coding for these apolipoproteins were investigated in weanling male rats pair-fed for 6 wk with a control or copperdeficient diet. Plasma cholesterol, triglycerides, and phospholipids were significantly increased, and plasma apo B and apo E levels were also markedly increased in copper-deficient rats as compared to control rats. Copper deficiency significantly increased triglyceride levels and decreased cholesterol levels in the liver. No major differences in the levels of hepatic and intestinal apo B and apo E mRNA occurred between control and copper-deficient rats. These data imply that hypertriglyceridemia dn hypercholesterolemia owing to the copper deficiency are not accompanied by modifications in the gene expression at the mRNA level in the liver and intestine of the apolipoproteins studied.     

非酒精性脂肪性肝炎大鼠肝脏血管内皮生长因子表达的意义

目的探讨血管内皮生长因子（VEGF）在非酒精性脂肪性肝炎（NASH）大鼠肝脏的表达及意义。方法 20只大鼠随机分为对照组（10只）和模型组（10只）,分别给予标准饮食和高脂饮食16周,进行肝脏病理学检查和血生化指标分析;采用超高频小动物超声诊断仪检测肝脏及其血流动力学改变,利用分子生物学方法检测肝组织VEGF表达水平。结果模型组大鼠ALT、AST和TC增高（P〈0.05）。肝组织病理表现为大小泡混合性脂肪变性,伴肝细胞气球样变性、炎性细胞浸润、碎片状坏死和少量纤维组织增生。超声结果为肝脏增大,肝缘圆钝,实质回声细密增强,后方组织明显衰减,与脂肪肝病理结果一致;门静脉内径增大,肝静脉内径减小（p〈0.05）,静脉流速降低。肝组织VEGF蛋白和mRNA表达明显增加（P〈0.05）,VEGF蛋白主要表达在肝细胞和窦内皮细胞。结论 NASH肝脏VEGF蛋白和mRNA表达明显增加,VEGF可能参与NASH肝脏血流动力学的异常。     

Inflammatory response following acute magnesium deficiency in the rat

The importance of inflammatory processes in the pathology of Mg deficiency has been recently reconsidered but the sequence of events leading to the inflammatory response remains unclear. Thus, the purpose of the present study was to characterize more precisely the acute phase response following Mg deficiency in the rat. Weaning male Wistar rats were pair-fed either a Mg-deficient or a control diet for either 4 or 8 days. The characteristic allergy-like crisis of Mg-deficient rats was accompanied by a blood leukocyte response and changes in leukocytes subpopulations. A significant increase in interleukin-6 (IL-6) plasma level was observed in Mg-deficient rats compared to rats fed a control diet. The inflammatory process was accompanied by an increase in plasma levels of acute phase proteins. The concentrations of alpha2-macroglobulin and alpha1-acid glycoprotein in the plasma of Mg-deficient rats were higher than in control rats. This was accompanied in the liver by an increase in the level of mRNA coding for these proteins. Moreover, Mg-deficient rats showed a significant increase in plasma fibrinogen and a significant decrease in albumin concentrations. Macrophages found in greater number in the peritoneal cavity of Mg-deficient rats were activated endogenously and appeared to be primed for superoxide production following phorbol myristate acetate stimulation. A high plasma level of IL-6 could be detected as early as day 4 for the Mg-deficient diet. Substance P does not appear to be the initiator of inflammation since IL-6 increase was observed without plasma elevation of this neuropeptide. The fact that the inflammatory response was an early consequence of Mg deficiency suggests that reduced extracellular Mg might be responsible for the activated state of immune cells.     

Attenuation of LDL receptor gene expression by selenium deficiency during hypercholesterolemia

Selenium deficiency has been associated with hypercholesterolemia. Present study was aimed to determine the effect of selenium (Se) deficiency on LDL receptor (LDL-R) activity as well as mRNA expression during experimental hypercholesterolemia in SD male rats. Animals were fed Se adequate (0.2 ppm) and deficient (0.02 ppm) control diet as well as high cholesterol (2%) diet (HCD) for 1 and 2 months. LDL-R activity was measured in vivo by injecting radiolabeled LDL to rats and percent decrease in cpm with time was taken as a measure of LDL clearance and in turn LDL-R activity. LDL-R mRNA expression was studied by RT-PCR. LDL-R activity and mRNA expression decreased significantly on HCD feeding in both Se deficient and adequate diet fed rats after 2 months. In Se deficiency receptor activity and mRNA expression decreased significantly. After 2 months LDL-R activity and expression decreased in both the Se deficient groups and in Se adequate HCD fed group in comparison to 1 month data. But after 4 month there was no significant difference observed in LDL-R activity and mRNA expression in selenium deficiency as well as on HCD feeding. So the present results demonstrate that Se deficiency act synergistically with hypercholesterolemia to downregulate LDL-R activity as well as mRNA expression.     

Glutamine decreases lipopolysaccharide-induced intestinal inflammation in infant rats

Using a gastrostomy-fed (GF) rat infant "pup-in-a-cup" model, the effects of protein deprivation and supplemental glutamine (Gln) and glutamate (Glu) were examined to test the hypothesis that Gln decreases the proinflammatory response induced by LPS in the developing infant rat small intestine. Four groups of 6- to 7-day-old pups were fed a rat milk substitute (RMS), one providing 100% and three providing 25% of normal protein intake for another 6 days. Two of the 25% protein-fed groups received supplemental Gln or Glu. GF and LPS treatment blunted body growth and intestinal villus height and increased intestinal cytokine-induced neutrophil chemoattractant (CINC) mRNA in the protein-deprived, non-Gln-treated group compared with mother-fed pups (P < 0.05). Gln blunted intestinal CINC mRNA (P < 0.05), but Glu did not. Intestinal CINC peptide in the LPS-treated pups provided 100 and 25% protein was elevated approximately 13-fold compared with the mother-reared pups (P < 0.001). Gln and Glu decreased intestinal CINC peptide by 73 and 80%, respectively. GF, LPS-treated pups also had a higher level of plasma CINC peptide (P < 0.05). Gln but not Glu decreased plasma CINC peptide (P < 0.05). An approximate sixfold elevation of intestinal MPO activity in the GF, LPS-treated rats was decreased by Gln and Glu by 92% (P < 0.001) and 54% (P < 0.05), respectively. Intestinal and plasma TNF-alpha were increased in GF, LPS-treated pups (P < 0.01), and Gln and Glu both blunted this increase (P < 0.05) in the intestine but not in the plasma. The results indicate that Gln decreases the LPS-induced inflammatory response in infant rat intestine under different conditions of protein intake.     

Diet-induced adaptation of intestinal fructose absorption in the rat.

The effect of dietary sucrose, fructose and glucose on the intestinal absorption of fructose and glucose was investigated in adult rats in vivo: Glucose absorption was not affected by the type of dietary carbohydrate, while the absorption of fructose was increased by the ingestion of the sucrose or fructose diet, as compared with the glucose diet. An almost maximal increase of fructose absorption was already observed when the quarter of the total dietary carbohydrates was replaced by fructose. Faecal fructose elimination declined during the feeding experiment. The enhanced intestinal absorption of the fructose load in rats fed the fructose diet was manifested by higher concentrations of fructose, but also of glucose and lactate in the hepatic portal blood.     

Hypocholesterolemic mechanism of Chlorella: Chlorella and its indigestible fraction enhance hepatic cholesterol catabolism through up-regulation of cholesterol 7alpha-hydroxylase in rats

Chlorella powder (CP) has a hypocholesterolemic effect and high bile acid-binding capacity; however, its effects on hepatic cholesterol metabolism are still unclear. In the present study, male Wistar rats were divided into four groups and fed a high sucrose + 10% lard diet (H), an H + 10% CP diet (H+CP), an H + 0.5% cholesterol + 0.25% sodium cholate diet (C), or a C + 10% CP diet (C+CP) for 2 weeks. CP decreased serum and liver cholesterol levels significantly in rats fed C-based diets, but did not affect these parameters in rats fed H-based diets. CP increased the hepatic mRNA level and activity of cholesterol 7alpha-hydroxylase (CYP7A1). CP increased hepatic HMG-CoA reductase (HMGR) activity in the rats fed H-based diets, but not in rats fed C-based diets. CP did not affect hepatic mRNA levels of sterol 27-hydroxylase, HMGR, low-density lipoprotein (LDL) receptor, scavenger receptor class B1, ATP-binding cassette (ABC) A1, ABCG5, or ABCB11. Furthermore, the effect of a 3.08% Chlorella indigestible fraction (CIF, corresponding to 10% CP) on hepatic cholesterol metabolism was determined using the same animal models. CIF also decreased serum and liver cholesterol levels significantly in rats fed C-based diets. CIF increased hepatic CYP7A1 mRNA levels. These results suggest that the hypocholesterolemic effect of CP involves enhancement of cholesterol catabolism through up-regulation of hepatic CYP7A1 expression and that CIF contributes to the hypocholesterolemic effect.     

Green tea flavonoids inhibit the LDL oxidation in osteogenic disordered rats fed a marginal ascorbic acid in diet

Osteogenic Disorder Shionogi (ODS) rats can not synthesize ascorbic acid (AA). We have examined the capacity of green tea flavonoids (GTF) to modify low-density lipoprotein (LDL) oxidation in ODS rats with dietary AA restriction. In the first experiment, ODS rats were fed diets containing 300 (AA300 diet) or 0 (AA0 diet) mg AA/kg diets for 20 d. In comparison with the AA300 diet, the AA0 diet significantly decreased the concentrations of plasma AA and alpha-tocopherol in LDL and significantly shortened the lag time of LDL oxidation in vitro. In the second experiment, ODS rats were fed one of the following three diets: the AA300 diet, the diet containing 25 mg AA (AA25, marginal AA)/kg diet (AA25 diet), or the diet containing 25 mg AA + 8 g GTF/kg diet (AA25 + GTF diet) for 20 d. Plasma AA concentration were significantly lower in rats fed AA25 compared with AA300 but not in those fed AA25 + GTF. LDL oxidation lag time was significantly longer in rats fed AA25 + GTF compared with the other two groups. Lag time for LDL oxidation was significantly and positively correlated with LDL alpha-tocopherol (r = 0.6885, P = 0.0191). These results suggest that dietary flavonoids suppress the LDL oxidation through the sparing effect on LDL alpha-tocopherol and/or plasma AA when AA intake is marginal in the ODS rats.