Hepatic and serum arginase and ornithine transcarbamylase activities of rats maintained on diets of different protein quality

Groups of rats were fed diets containing 15% protein from arhar dal (Cajanus cajan), bengal gram dal (Cicer arietinum), urad dal (Phaseolus mungo) and also isolated proteins from casein, egg, soya bean, gluten and gelatin for a period of 10 days. Rats maintained on the casein diet had the highest liver arginase activity and those having egg the lowest. All the leguminous proteins gave similar levels of arginase activity, the values falling between the casein and egg groups. Serum arginase level was found to be low only in rats on egg and gluten diets. Liver ornithine transcarbamylase (OTC) activity was significantly higher when legumes provided the protein as compared with the diet containing egg. Serum OTC level was lowest in the egg and arhar dal groups. Though the levels of urea cycle enzymes were altered by the quality of dietary proteins, no simple relationship could be established between them.     

Reduced lipogenesis in rats fed a high-protein carbohydrate-free diet

Rates of fatty acid synthesis were assessed in carcass, liver, and adipose tissue from rats fed for 30 to 40 days a balanced diet (66% wt/wt carbohydrate, 17% casein, 8% fat) or a high-protein carbohydrate-free diet (70% casein, 8% fat). Despite similar body weight increases, carcass fatty acid content of rats on the high-protein (HP) diet was 13% less, and the weight of their epididymal fat pads was reduced by 29% in relation to the controls. In vivo incorporation of 3H2O into carcass fatty acids (FA) and into liver triacylglycerol (TAG) was significantly reduced in HP-fed rats. FA synthesis from 14C-acetate, glucose, or leucine and from 3H2O was also markedly decreased in liver slices from HP rats. The amount of 3H-TAG that accumulated in plasma of rats injected with triton WR 1339 to block peripheral utilization of lipoprotein corresponded in HP and control rats to only 4.1% and 5.0%, respectively, of 3H-FA recovered in carcasses from animals not treated with triton, indicating that almost all of the carcass 3H-TAG was synthesized in situ. However, on a long term basis, the reduced hepatic lipogenesis and the resulting decreased transport of TAG might affect lipid accumulation in HP rats. In vivo lipogenesis from 3H2O and in vitro FA synthesis from 3H2O and from 14C-precursors did not differ significantly in retroperitoneal and epididymal adipose tissue from HP and control rats. In both groups of animals, in vivo rates of lipogenesis were higher in retroperitoneal than in epididymal adipose tissue but still did not account for rates of FA synthesis by carcasses, suggesting the existence of other sites with higher lipogenic activity.     

Effects of soy components on blood and liver lipids in rats fed high-cholesterol diets

AIM: To assess the effects of soy protein, isoflavone, and saponin on liver and blood lipid in rats that consumed high-cholesterol diets. METHODS: High-cholesterol diets (1%) with or without soy material were fed to 6-wk-old male Sprague-Dawley rats for 8 wk. Blood lipids, liver lipids, glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) levels were measured. The in vitro bile acid-binding ability of soy materials was analyzed. RESULTS: The results of in vitro studies showed that soy protein isolate had a significantly higher bile acid-binding ability (8.4±0.8%) than soy saponin (3.1±0.7%) and isoflavone (1.3±0.4%, P<0.05). On the other hand, at the end of the experimental period, rats that consumed soy protein diets had lower GOT and GPT levels than rats that consumed casein under high-cholesterol diets. Rats that consumed soy protein also had lower total cholesterol (TC) levels in the liver than those that consumed casein under high-cholesterol diets. Rats that consumed the soy protein diet containing both saponin and isoflavone had lower hepatic TC level than those that consumed the soy protein diet without isoflavone alone. The effect of different types of proteins on triglyceride was not significant. CONCLUSION: Consumption of soy provided benefits to control lipid levels under high-cholesterol dieting conditions in this rat model of hypercholesterolemia. The major component that reduced hepatic TC was not saponin, but possibly isoflavone.     

Effect of protein malnutrition on glycoprotein, protein and lipid synthesis in the rat cerebellum during the period of brain growth spurt

Female Wistar rats were fed a normal-protein diet (25% casein) or a low-protein diet (8% casein) during pregnancy and lactation. The two diets were isocaloric and contained appropriate amounts of mineral salts and vitamins. Pups from dams submitted to the low-protein diet had a lower body weight than normally fed controls as early as on the day of birth, but a difference in cerebellar weight between the two groups was observed only on the 15th postnatal day. Malnutrition had no effect on cerebellar protein concentration, which increased with age in both groups. The cerebellar DNA concentration was higher at 7 and 15 days of age in normally fed rats than in malnourished rats, whereas at 21 days of age it was higher in the malnourished animals. [U-14C]Leucine and [2-3H]mannose incorporation into proteins and lipid synthesis from acetyl coenzyme A (CoA) derived from [U-14C]leucine markedly decreased with age in the cerebellum of rats fed both diets. [2-3H]Mannose incorporation into cerebellar glycoproteins was greater in malnourished rats during the period of brain growth spurt than in normally fed rats at all ages studied. Prenatal and postnatal protein malnutrition had no effect on [U-14C]leucine incorporation into cerebellar proteins or on cerebellar lipid synthesis from acetyl-CoA derived from [U-14C]leucine during the period of brain growth spurt.     

Lack of effect of cerulein on pancreatic growth of rats fed a low-protein diet.

The effect of dietary protein deficiency and protein concentration of the diet on the pancreatic trophic response to a CCK analogue (cerulein) were studied. Rats were fed for 14 days with semipurified diets containing 5, 30, or 60% casein. During the final 4 days, they received 2 micrograms/kg cerulein or gelatin vehicle subcutaneously three times/day, and the effects on pancreatic weight and pancreatic content of protein, RNA, DNA, amylase, and chymotrypsin were determined. Cerulein failed to increase significantly any pancreatic parameter in rats fed 5% casein, while stimulating significant increases in almost all parameters in rats fed 30 and 60% casein diets. In the absence of cerulein treatment, increases in dietary protein levels caused progressive increases in all pancreatic growth parameters with the exception of amylase. In the presence of cerulein, increases in dietary protein concentrations caused progressive increases in pancreatic growth parameters (except amylase), which were maximal at 30% casein concentration of the diet for most parameters. The results confirm that pancreatic growth is stimulated by increasing protein concentration of the diet and indicate that a low protein diet, acting through a deficiency of dietary nitrogen and essential amino acids, limits the pancreatic trophic response to CCK or analogues. These results explain the failure of trypsin inhibitors to stimulate pancreatic growth in rats fed low levels of dietary protein.     

Relationship between magnesium and zinc levels of the diet and its protein utilization

Protein utilization of the diet was tested in relation to different levels of magnesium and zinc in rats. The experimental diets contained either a low (0.14 g Mg or 10 mg Zn/kg) or adequate (0.45 g Mg or 40 mg Zn/kg) level of Mg or Zn and two different quality protein sources: casein or wheat gluten. Net protein utilization and net protein radio indexes in case of casein were significantly lower for the diet containing a low level of Mg or Zn. For gluten diets, such differences were not observed. Digestibility of protein measured in rats fed a low Mg or Zn casein diet was the same as for the diets with an adequate content of these minerals. Rats fed low Mg or Zn casein diets showed a significantly lower plasma Mg or Zn and a lower liver DNA content in comparison to the rats on adequate Mg or Zn diets. The results indicate that the utilization of protein is affected by Mg and Zn content of the diet and that this relationship depends on the quality of protein.     

Influence of Dietary Protein Concentration and Quality on Response to Erythropoietin in the Polycythaemic Rat

S ummary . The effects were examined of dietary protein concentration and quality on the response of polycythaemic hypertransfused rats to 6 units of human urinary erythropoietin. Rats were either starved or fed one of 14 different diets. Four protein sources were used, having a quality gradient from 100 to about 24. Two proteins—casein and wheat gluten—were used at five different levels of concentration (5–25%) in the diet. The response of rats maintained on the standard diet (Purina rat chow, 23.4% protein/g) was taken as the normal standard. The response to erythropoietin was 25% of normal in starved rats and 35% of normal in rats put on a protein-free diet. When 10% protein in the diet was obtained by using high biological value proteins (egg yolk or casein) the response to erythropoietin was normal. When the same concentration was achieved by using low biological value proteins (wheat gluten or corn protein) the response to erythropoietin was undistinguishable from that of rats put on the protein-free diet. When rats were maintained on diets with different concentrations of casein (5–25%) a normal response was observed when protein concentration was 10% with no further changes at higher concentrations. When rats were fed diets with different wheat gluten concentrations (5–25%) the response to erythropoietin was subnormal. These data suggest that the ability of rats to respond normally to erythropoietin is dependent on a continuous dietary intake of proteins at levels which are dependent on their biological values.     

甘氨酸在肝硬化发生发展过程中对肝组织CD14基因及蛋白表达的影响

目的 观察甘氨酸在肝硬化形成过程中对肝组织表达CD14基因和CD14蛋白的影响。方法 采用复合因素建立肝硬化动物模型的同时，实验组分别用甘氨酸液（1g/d)给大鼠灌胃，或用含5%甘氨酸食物喂养大鼠，并于实验的2周末、4周末和8周末以逆转录多聚酶链反应（RT-PCR）和western blot法检测大鼠肝组织CD14 mRNA和CD14蛋白的表达。结果 在用含甘氨酸食物喂养的脂肪肝和肝硬化大鼠中，其肝组织CD14 mRNA及CD14蛋白的表达较对照组大鼠明显减弱，其中用含甘氨酸食物喂养8周末的肝硬化大鼠肝组织的CD14 mRNA及CD14蛋白表达最弱。结论 甘氨酸可下调肝组织CD14基因和CD14蛋白的表达。     

The effect of quantitative and qualitative protein deficiency on blood regeneration; hemoglobin

1. The effect of diets, varying in quantity or quality of protein, on hemopoiesiswas studied in protein depleted and anemic adult rats.

2. In experiments with diets containing different amounts of casein (0, 3, 9 and18 per cent, respectively), and fed ad libitum, it was found that with a protein-freediet a further decrease of hemoglobin occurred, whereas the other three dietsinitiated a regeneration of hemoglobin; its degree being more or less proportionalto the casein content.

3. In experiments, in which diets with 9 and 18 per cent of casein, respectively,were given in restricted amounts, it was found that the degree of hemoglobinformation was similar to that with the same diets when given ad libitum, whereasthe weight gain was considerably less. It is concluded, therefore, that in caloricdeficiency hemoglobin formation has a priority over weight recovery.

4. A diet containing 30 per cent casein and given in restricted amounts induceda further weight loss, whereas the concentration of hemoglobin showed a markedincrease. Comparing the results obtained by this diet with those observed with 18per cent casein diets, given either ad libitum or in controlled amounts, it was evident that restriction of the quantity of food protein interferes more seriously withhemopoiesis than restriction of calories.

5. Diets containing nutritionally inferior proteins fed at 9 per cent level, alsoimpaired normal hemopoiesis. Hemoglobin regeneration induced by the proteinsinvestigated was found to decrease in the following order: eggs, meat, processedsoya, casein, peanut, maize, wheat, gelatin.

6. Comparing the nutritive value of various proteins for regeneration of hemoglobin and of granulocytes it was found, that casein and soya and maize proteinsare considerably more efficient for hemoglobin formation than for production ofgranulocytes, whereas wheat protein and gelatin have a higher granulocytopoieticcapacity.

     

Effect of the average diet of the State of S?o Paulo, from time of pregnancy on body weight and composition of the offspring. Study in rats

The effect of diet of S?o Paulo State on some biochemical parameters in the liver, brain and plasma of rats at weaning and 90 days was studied. The tissue parameters studied were the amounts of DNA, RNA and protein in the liver and brain. For the plasma were the total protein and albumin. Wistar rat were fed a 13% casein (control) and 13% protein of experimental diet since the gestation. In experimental diet weight at birth, weaning and 90 days were considerably reduced. A comparison of the data of the experimental rats in relation to the control group indicated that: a) organ weight, total organ DNA, RNA and protein were all reduced; b) no differences in total protein and albumin in plasma were observed between the control and the experimental group. These results suggest that the diet experimental is deficient in some nutrients (minerals, vitamins?) and affected the cellular development of brain and liver.     

The effect of quantitative and qualitative protein deficiency on blood regeneration; white blood cells

1. The effect of diets, varying in quantity or quality of protein, on white bloodcell regeneration was studied in leukopenic rats, the leukopenia having been induced by a protein-free diet.

2. Diets containing different amounts of casein (3, 6, 9 and 18 per cent, respectively), were fed ad libitum. At the 3 per cent level, a further decrease occurred ofwhite blood cells, whereas the other three diets initiated a regeneration of leukocytes, its degree being more or less in proportion to the casein content.

3. In experiments with diets containing 18 and 30 per cent of casein, the amountof protein eaten and not its level in diet was the decisive factor in the regenerationof leukocytes. The white blood cell regenerating effect of a diet containing anoptimal level of protein, may be neutralized when given in restricted amounts.

4. Diets containing nutritionally inferior proteins, fed at 9 per cent level, alsoimpaired normal regeneration of leukocytes. The white blood cell regenerationafforded by the proteins investigated was found to increase in the following order:maize, gelatin, wheat, casein, processed soya, peanut, meat, egg.

5. In white blood cell regeneration promoted by dietary protein, granulocyteswere found to react to a greater degree than lymphocytes and monocytes.

     

Adaptive response of rats with diet-induced adiposity to energy restriction

Groups of 4-week old, male Osborne-Mendel rats were given high fat diet (HFD) for 12 weeks; one group was fed control diet (CON) for 28 weeks. HFD rats were transferred to control diet (HFDCON) and diets restricted to 80% (HFDR80) or 60% (HFDR60) of HFDCON intake for another 16 weeks, while one group continued on HFD. Body, liver and epididymal adipose tissue (EPI) weight, and the EPI/body weight ratio of HFDR60 group decreased significantly. EPI lipid content and total lipoprotein lipase activity also declined in response to 40% restriction. Overall, the data indicate that 40% energy restriction can stabilize body weight at a reduced level, and mobilize adipose lipid to meet the energy needs of HFD rats.     

Effects of soy protein and saponins on serum, tissue and feces steroids in rat

Four groups of rats were fed, for 45 days, one of the following semipurified diets containing sucrose 55% (w/w) and (a) casein 25%, (b) casein 24%, saponins (from Saponaria officinalis) 1%, (c) isolated soy protein 25%, (d) soy protein 24%, saponins 1%. The soy protein diet, compared to the casein one, produced an increase in the fecal excretion of neutral sterols on the 29th and 42nd days, without any modification in the liver, aorta and serum cholesterol concentrations. The effect of soy protein cannot be attributed to its saponin content but other substances associated to soy protein may interfere. With the casein diet, added saponins increased the fecal excretion of neutral sterols and bile acids and decreased liver and aorta cholesterol levels. Serum cholesterol was found unchanged. The effects of saponins were suppressed or greatly reduced with the soy protein diet. These results could be explained by binding of the sterols in insoluble forms.     

Comparison of metabolism of glycine injected intravenously in free and dipeptide forms

Dipeptides, like diglycine, when injected intravenously in rats, are quickly taken up by tissues and hydrolyzed. Metabolism of glycine residue released by diglycine hydrolysis was investigated in this study. Radioactive labeling of nonprotein [trichloroacetic acid (TCA) soluble] and protein fractions of pancreas, intestinal mucosa, liver, kidney cortex, lung, gastrocnemius muscle, brain and plasma, as well as expired CO₂, were determined after injection of ¹⁴C-diglycine. Results were compared with those obtained after equivalent ¹⁴C-glycine injection. The effect of tissue dipeptide hydrolysis on distribution of radioactivity was examined after injection of ¹⁴C-glycylsarcosine under similar experimental conditions. Generally, intravenous injection of diglycine was at least as effective as that of glycine in labeling of nonprotein and protein fractions; labeling of kidney TCA-soluble pool was significantly higher and only that of muscle was lower after diglycine injection. Tissue capacities for transport and protein synthesis appeared to determine the extent of nonprotein and protein labeling, respectively, after both ¹⁴C-glycine and ¹⁴C-diglycine injections. Radioactive labeling of nonprotein pools and proteins were influenced by tissue capacities for dipeptide hydrolysis; both were higher in kidney and lower in pancreas and liver when glycylsarcosine was injected as compared to diglycine. Oxidation of injected glycine (labeling of expired CO₂) was significantly enhanced when glycine was given in the form of diglycine but was reduced when given as glycylsarcosine as compared to free-glycine injection. In conclusion, glycine residue of a readily hydrolyzable peptide, like diglycine, is as effective as free glycine when injected intravenously for incorporation into tissue proteins (except muscle) and for oxidative energy metabolism, while injection of an hydrolysis-resistant peptide like glycylsarcosine favors incorporation of glycine residue into kidney protein at the expense of other tissues.     

The effect of dietary lysine to arginine ratio on cholesterol kinetics in rabbits

The effect of varying the compositions of dietary proteins on the relative cholesterolaemic effects of animal and vegetable proteins was investigated in rabbits. In experiments using high fat diets, the amino acid compositions of dietary proteins (soya or casein) were altered by blending them 1:1 (w/w) with gelatin. This reduced the differences in amino acid compositions and also made soya more and casein less hypercholesterolaemic. In experiment 2a, soya protein was compared with dried skim milk in low fat diets and in experiment 2b, these proteins were supplemented with lysine or arginine, respectively, so that the lysine:arginine ratio of soya was similar to dried skim milk and vice-versa. Serum cholesterol was significantly higher in milk-fed than soya-fed rabbits and was not influenced by reversing the lysine:arginine ratio. In the three experiments, parameters of cholesterol kinetics were estimated from the die-away curve of injected [4 14-C]cholesterol. There were no significant effects of diet on the parameters of cholesterol kinetics. It was concluded that the lysine:arginine ratio of the diet is not the major determinant of the cholesterolaemic properties of proteins, but that the overall amino acid composition is primarily concerned.     

Effects of undernutrition on glycine metabolism in the cerebellum of rats

Undernutrition is a worldwide problem affecting millions of unborn and young children during the most vulnerable stages of brain development. Total restriction of protein during the perinatal period of life can alter the development of the mammalian fetus and have marked repercussions on development of the central nervous system (CNS). The brain is vulnerable to undernutrition with altered morphologic and biochemical maturation, leading to impaired functions. The focus of this study is to investigate [U-14C]glycine metabolism in undernourished rats submitted to pre- and postnatal protein deprivation (diet: 8% protein with and without addition of L-methionine; control group: 25% protein). Although undernutrition produced a reduction in cerebellar weight and alterations in the DNA concentration, the present study shows that glycine metabolism in this structure is partially protected because the undernourished group with L-methionine did not show modifications in glycine metabolism at all ages studied. However, L-methionine deficiency alters glycine metabolism at 7 and 21 days, but in the adult age both undernourished groups presented no differences in oxidation to CO2, conversion to lipids and incorporation into protein from glycine, compared to the control group.     

Diets containing salmon fillet delay development of high blood pressure and hyperfusion damage in kidneys in obese Zucker fa/fa rats

Hypertension is the leading risk factor for cardiovascular and chronic renal diseases, affecting more than 1 billion people. Fish intake is inversely correlated with the prevalence of hypertension in several, but not all, studies, and intake of fish oil and fish proteins has shown promising potential to delay development of high blood pressure in rats. The effects of baked and raw salmon fillet intake on blood pressure and renal function were investigated in obese Zucker fa/fa rats, which spontaneously develop hypertension with proteinuria and renal failure. Rats were fed diets containing baked or raw salmon fillet in an amount corresponding to 25% of total protein from salmon and 75% of protein from casein, or casein as the sole protein source (control group) for 4 weeks. Results show lower blood pressure and lower urine concentrations of albumin and cystatin C (relative to creatinine) in salmon diet groups when compared to control group. Morphological examinations revealed less prominent hyperfusion damage in podocytes from rats fed diets containing baked or raw salmon when compared to control rats. In conclusion, diets containing baked or raw salmon fillet delayed the development of hypertension and protected against podocyte damage in obese Zucker fa/fa rats.     

In vivo conversion of tryptophan to nicotinic acid in rats studied by simultaneous incorporation of [3H]-tryptophan and [14C]-nicotinic acid into liver NAD and NADP

This study was carried out with three groups of weanling rats. One group was fed a high-protein (20%) diet, another group a low-protein (2.5%) diet, the third group a high-protein diet in restricted amounts. After 4 weeks of feeding, rats were injected simultaneously with L-[G-3H]-tryptophan and [carboxyl-14C]-nicotinic acid. The ratio of incorporation of [3H]-tryptophan to that of [14C]-nicotinic acid into liver NAD and NADP was found to be higher in protein-restricted rats. On the other hand, the ratio was found to be reduced in diet-restricted group of rats compared with ad libitum fed or low-protein diet fed groups. These results suggest that the efficiency of conversion of tryptophan to NAD is increased in protein deficiency, but reduced in the diet restriction. These observations are in line with our earlier findings on the changes in liver quinolinate phosphoribosyltransferase (EC 2.4.2.19) activity following feeding of low-protein or restricted diets. It is suggested that this technique of measuring the incorporation of two isotopes from the substrates labelled with two different isotopes can be conveniently used as a tool to measure the relative contribution of tryptophan and nicotinic acid to the synthesis of nicotinamide nucleotides.     

Protein quality evaluation in rats of typical diets for 4- to 6-year-old children from different socioeconomic areas living in Oaxaca, Mexico

Legumes and cereals are principal sources of energy and protein in developing countries. In Oaxaca, Mexico, corn is the primary agricultural crop, therefore corn tortillas and beans are the main energy and protein sources. The objective of this study was to evaluate the protein quality in rats of typical diets for 4- to 6-year-old children from different socioeconomic areas in Oaxaca, Mexico. Composite diets representing the typical diets were formulated and fed to male weanling rats for 10 days. A control diet using casein as the reference diet and one free of nitrogen were included in the study. The apparent protein digestibility was determined in rats using the chromic oxide marker technique and the data was statistically analyzed for differences between control and experimental diets. Rats fed the diet of low income children gained about 2 g/day compared to about 3.8 g/day for the rats fed the control (casein) diet and had the lowest weight gain/g of protein intake. The NPR was 3.52 compared to 4.31 for the control diet. This diet is 67% vegetable protein and 33% animal protein. The diet for the medium income group contained a higher percentage of animal protein, 76% and thus higher digestibility, 78%. The results of this study indicate that the protein quality of children's diets in Oaxaca, Mexico, need to be improved.