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PubMed2004

Differential increases in syntheses of newly identified trypsinogen 2 isoforms by dietary protein in rat pancreas.

We have found that dietary protein markedly induced pancreatic serine protease activity via a mechanism independent of luminal trypsin activity in pancreaticobiliary-diverted (PBD) rats. The aim of this study was to examine the effects of dietary protein on the synthesis of trypsinogen isoforms by comparing in vivo incorporation of [35S] L-methionine into isoform proteins in PBD and sham-operated rats. A small duodenal segment including the ampulla of Vater was sectioned and transposed to the upper ileum with end-to-side anastomosis (PBD) or duodenal transection was followed by reanastomosis (sham) in male Sprague-Dawley rats. After recovery, PBD and sham rats were fed a 25% or 60% casein-sucrose-based diet (NC or HC) for 14 days. Rats were then intravenously injected with [35S] L-methionine (15 MBq/kg body weight) 30 mins before being sacrificed for analysis of pancreatic enzymes by two-dimensional SDS-polyacrylamide gel electrophoresis. By using electrophoresis with narrow range of isoelectric focusing (pI 4.5-5.5), five trypsinogen 2 (2-x) isoform spots were identified using both [35S] incorporation and Coomassie brilliant blue (CBB) staining in PBD rats, but not in sham rats. N-terminal sequences of these trypsinogen 2-x spots were identical to known rat trypsinogen 2 with the exception that the third valine was changed to isoleucine in one isoform. In PBD rats, feeding of HC specifically increased the [35S] and CBB intensities of these trypsinogen 2-x isoforms and trypsinogen 3. The degree of induction of the five trypsinogen 2-x molecules by HC varied greatly. Trypsinogen 1 and 4, which are the major trypsinogens in normal rats, showed no changes. We conclude that increases in synthesis of a few newly identified trypsinogen 2-x isoforms mainly contribute to the induction of trypsin activity in the pancreas by HC in PBD rats.

Anastomosis, Surgical↗
PubMed1984

Effects of dietary protein and exercise on brown adipose tissue and energy balance in experimental animals.

The effects of exercise and of dietary protein level on energy metabolism and brown adipose tissue (BAT) activity were investigated in weaning male mice. Mice were fed diets providing low (7.5%), adequate (12.5%) or high (25%) levels of dietary protein. Half of the animals in each dietary group were given moderate exercise by swimming. The lower the level of dietary protein, the greater the increase in food intake, energy expenditure, body fat and BAT mass; however, total-carcass energy, food efficiency and BAT activity were not affected by the level of dietary protein. In experiment 2, BAT was compared in mice swimming at 33 degrees C and 36 degrees C with non-exercised controls. In a third experiment, energy balance and BAT activity were compared in rats exercised at 36 degrees C and in paired weight gain (PWG) rats whose food intake was restricted to achieve weight gains equal to that of the exercised rats. PWG rats maintained carcass energy content equal to that of the controls and significantly greater than the exercised rats by decreasing energy expenditure. Moderate exercise did not affect food intake, whereas rigorous exercise decreased energy intake. Exercise did not affect BAT mass or thermogenic activity; however, mild cold stress did increase BAT activity. Exercise decreased body fat, carcass energy and food efficiency without affecting BAT.

Adipose Tissue, Brown↗
PubMed1983

Cellular growth responses of rainbow trout (Salmo gairdneri) fed different levels of dietary protein, and an anabolic steroid ethylestrenol.

Cellular growth responses of rainbow trout (Salmo gairdneri) fed different levels of dietary protein (35, 45, and 55%), with and without the anabolic steroid ethylestrenol, have been studied over a 60-day period. With an increase in dietary protein, total liver proteins increased in fish fed the steroid-free (control) diets, whereas no change occurred in the other tissues. Muscle and spleen RNA was unchanged, but RNA increased in liver, kidney, and brain. The DNA content increased in muscle, decreased in brain, but remained constant in liver, kidney, and spleen. Feeding the ethylestrenol-supplemented (experimental) diets resulted in an increase in total proteins, RNA, and DNA of kidney over the respective control value at each level of dietary protein. In the other tissues, total proteins and DNA were essentially unchanged, but total RNA content decreased in liver and increased in muscle in the experimental groups. It is concluded that in trout, the dietary protein level exerts marked differential effects on cellular growth parameters (RNA/DNA, RNA/protein, protein/DNA), which are further modified by steroid treatment. Evidence that cellular growth responses in muscle keep pace with total body growth was also indicated.

Animals↗
PubMed1985

Absence of chronic effects of dietary protein content on brain tryptophan concentrations in rats.

Groups of young, adult, male rats were given free access for 2 wk to a diet containing 12, 24 or 40% protein (dry weight). During this period, all animals grew considerably; those consuming the 12% protein diet grew less rapidly than those ingesting the higher percent protein diets. At the end of 2 wk, six rats from each diet group were killed every 4 h throughout a 24-h period, and blood samples and whole brains were obtained for analysis. Serum tryptophan levels were lowest in animals consuming the 12% protein diet, intermediate in rats consuming the 24% protein diet and highest in rats consuming the 40% protein diet (at all times studied). Brain tryptophan levels, however, did not differ significantly as a function of dietary protein content. The ratio in serum of the concentration of tryptophan to the sum of the concentrations of its competitors for brain uptake also was not significantly influenced by dietary protein level. Levels of 5-hydroxyindoles in brain showed significant diurnal variations but no evidence of a significant effect of dietary protein content. Since the ratio of serum tryptophan to its competitors and the levels in brain of tryptophan and 5-hydroxyindoles did not vary as a function of dietary protein intake, the results do not support the view that these variables serve as signals to the brain for regulating long-term dietary protein intake.

Animals↗
PubMed1991

Effect of dietary protein depletion and ethanol on demethylation and denitrosation of N-nitrosodimethylamine by rabbit liver microsomes.

To study how the metabolism of N-nitrosodimethylamine (NDMA) is affected by dietary protein level and chronic ethanol feeding, 24 rabbits at 18 weeks of age, assigned to four groups, each with 6 rabbits, were fed for 8 weeks on the following 4 different diets; 21% protein content containing 21.1% casein and water, 21% protein content containing 21.1% casein and 7.5% ethanol, 7% protein content containing 4.8% casein and water, 7% protein content containing 4.8% casein and 7.5% ethanol. Body weights, liver weights and microsomal protein contents in the liver were significantly smaller in 7% protein diet groups than in 21% protein diet groups. Microsomal P-450 contents per protein content were less in 7% protein diet groups than in 21% protein diet groups. NDMA demethylation activity due to non-arachidonic acid stimulated system (NASS) and NDMA denitrosation activity were greater in 21% protein diet groups than in 7% diet groups. Chronic ethanol feeding increased NDMA denitrosation activity due to arachidonic acid stimulated system in both dietary protein levels. The ratio of NDMA demethylation activity (carcinogenic action) to NDMA denitrosation activity (detoxication action) was greater in 7% dietary protein groups than 21% dietary protein groups. The value of this ratio was decreased by chronic ethanol feeding in 7% dietary protein groups. Cytotoxic and carcinogenic actions of NDMA might be enhanced by low protein diet due to inhibition of denitrosation of NDMA in liver microsome and chronic 7.5% ethanol feeding alleviates metabolic activation of NDMA to carcinogenic compounds.

Animals↗
PubMed1983

Effect of dietary protein concentration on yield of mutagenic metabolites from 1,2-dimethylhydrazine in mice.

The effects of varying dietary protein concentrations on the metabolism of 1,2-dimethylhydrazine (DMH) to mutagenic products by male C57BL/6 X C3H F mice were assayed by in vivo and in vitro methods. DMH and its metabolite, azoxymethane (AOM), did not increase the mutation frequency of Salmonella typhimurium (strain G-46) in vitro alone or in the presence of mouse liver homogenates capable of activating the promutagen dimethylnitrosamine. Methylazoxymethanol (MAM), another metabolite of DMH, was mutagenic in vitro without activation. S.c. administration of DMH, AOM, or MAM at dosages ranging from 0.2 to 0.8 mmol/kg of body weight caused dose-dependent increases in mutations of S. typhimurium in the host-mediated assay, and molar potencies increased progressively from DMH to AOM to MAM. S.c. or i.p. injections of AOM increased host-mediated mutagenesis within 20 min, while increases in mutagenesis by DMH required at least 1 hr. When [14C]DMH was administered, [14C]azomethane was expired immediately, while 14CO2 began to appear 1 hr after DMH administration. The percentage of administered [14C]DMH expired as azomethane varied inversely with dietary protein concentration, while AOM-induced host-mediated mutagenesis was directly proportional to dietary protein (p less than 0.01). The percentage of DMH converted to mutagenic end products was limited by losses of the volatile metabolite azomethane, especially in protein-deficient mice. Greater expiration of azomethane and decreased conversion of AOM to MAM, both seen with restriction of dietary protein, were associated with a smaller body burden of DMH metabolites.

1,2-Dimethylhydrazine↗
PubMed1999

Local antibody response in Peyer's patches to the orally administered dietary protein antigen.

To understand local antibody production to dietary protein antigens in the gut, the reactivity of the monoclonal antibodies (mAbs) from Peyer's patches of BALB/c mice raised against orally administered hen egg lysozyme (HEL) was studied. These mAbs were of IgG1 (7 clones), IgA (5 clones) and IgM (13 clones) isotypes. Some of the HEL-binding mAbs preferentially reacted with reduced, carboxy-methylated HEL, rather than with native HEL. MAbs of the IgA and IgM isotypes had cross-reactivity with other unrelated environmental antigens such as E. coli, single-strand DNA, and soluble components of mouse food. In contrast, the IgG1 mAbs did not cross-react with these antigens. The average of the Kd values for HEL of these mAbs was in the order of 10(-6) M, which is moderately higher than those of mAbs from the preimmune repertoire. These results suggest that, under normal physiological conditions, orally administered dietary proteins predominantly induce the local production of polyreactive IgA/IgM antibodies cross-reacting with environmental luminal antigens.

Administration, Oral↗
PubMed2003

VLDL metabolism in rats is affected by the concentration and source of dietary protein.

The present study was designed to determine if changes in dietary protein level and source are related to changes in VLDL lipid concentrations and VLDL binding by hepatic membranes and isolated hepatocytes. Male Wistar rats were fed cholesterol-free diets containing 10, 20 or 30 g/100 g casein or highly purified soybean protein for 4 wk. Hepatic, plasma and VLDL lipids, VLDL apo B-100 and VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane were determined. Increasing casein or soybean protein level (from 10 to 30 g/100 g) in the diet increased VLDL apo B-100, indicating an increase in the number of VLDL particles. VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane increased when the protein level increased from 10 to 20 g/100 g in the diet and decreased with 30 g/100 g protein, regardless of protein type. The dietary protein source did not affect plasma total cholesterol concentrations at any protein level. Feeding 20 g/100 g soybean protein compared with casein lowered plasma triglyceride concentrations and VLDL number as measured by decreased VLDL-protein, -phospholipid, -triglyceride, -cholesterol and -apo B-100. VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane were higher in rats fed soybean protein than those fed casein. The higher VLDL uptake could be responsible for the hypotriglyceridemia in rats fed soybean protein.

Animals↗
PubMed1984

Protein and energy utilization in germ-free and conventional chicks given diets containing different levels of dietary protein.

The present study was done to clarify the relationship between the amount of dietary protein given to, and the gut microflora of, the host. Day-old chicks were given diets containing three concentrations of dietary protein (50, 200 and 400 g/kg) for 14 d. Body-weight gain, food consumption, body consumption, and protein and energy utilization were measured. There was no difference in body-weight gain and food consumption between germ-free (GF) and conventional (CV) chicks, but food conversion efficiency (g body-weight gained/g food consumed) was significantly higher in GF than in CV chicks. Little difference was found in protein retention (g protein retained/14 d), but protein retention rate (g protein retained/g protein consumed) tended to be higher in GF chicks, particularly those given the diet with the lowest protein. The presence of micro-organisms improved metabolizable energy (ME) values of the diets, but not all of the digested energy in CV chicks was utilized for growth. Therefore there was little difference in energy retention (kJ energy retained/14 d) between environments, although energy retention rate (kJ energy retained/kJ ME consumed) was significantly lower in CV chicks. The amount of body fat in GF chicks was higher than that in CV chicks, especially in those fed on the low-protein diet. It is suggested that although the gut microflora may have beneficial effects on the digestion of dietary energy components, they may have detrimental effects on utilization of ME by their hosts, because chicks harbouring a gut microflora seem to have higher energy requirements for maintenance.

Animal Nutritional Physiological Phenomena↗
PubMed1999

Role of learning in the selection of dietary protein in the golden hamster (Mesocricetus auratus).

Hamsters (Mesocricetus auratus) were kept for several weeks on maintenance diets (MDs) that were either nutritionally complete or protein deficient, and had periodic access to protein-free and high-protein conditioning diets (CDs) with marker flavors (anise and clove). In Experiment 1, protein-restricted hamsters came to prefer the flavor of high-protein CDs but did not prefer unflavored high-protein CD. Thus, hamsters learned to select dietary protein by attending to the flavor of the CD. In Experiment 2, a within-subjects design was used, and MDs also had marker flavors (garlic and sage). Hamsters came to prefer the flavor of high-protein CD when protein restricted, and they showed this preference even in the absence of protein restriction if reexposed for only 90 min to merely the flavor of a protein-deficient MD. Thus, learned associations between the flavor and the usual postingestional consequences of a recently ingested MD can affect short-term dietary protein selection.

Animals↗
PubMed2003

Dietary protein restriction causes modification in aluminum-induced alteration in glutamate and GABA system of rat brain.

BACKGROUND: Alteration of glutamate and gamma-aminobutyrate system have been reported to be associated with neurodegenerative disorders and have been postulated to be involved in aluminum-induced neurotoxicity as well. Aluminum, an well known and commonly exposed neurotoxin, was found to alter glutamate and gamma-aminobutyrate levels as well as activities of associated enzymes with regional specificity. Protein malnutrition also reported to alter glutamate level and some of its metabolic enzymes. Thus the region-wise study of levels of brain glutamate and gamma-aminobutyrate system in protein adequacy and inadequacy may be worthwhile to understand the mechanism of aluminum-induced neurotoxicity. RESULTS: Protein restriction does not have any significant impact on regional aluminum and gamma-aminobutyrate contents of rat brain. Significant interaction of dietary protein restriction and aluminum intoxication to alter regional brain glutamate level was observed in the tested brain regions except cerebellum. Alteration in glutamate alpha-decarboxylase and gamma-aminobutyrate transaminase activities were found to be significantly influenced by interaction of aluminum intoxication and dietary protein restriction in all the tested brain regions. In case of regional brain succinic semialdehyde content, this interaction was significant only in cerebrum and thalamic area. CONCLUSION: The alterations of regional brain glutamate and gamma-aminobutyrate levels by aluminum are region specific as well as dependent on dietary protein intake. The impact of aluminum exposure on the metabolism of these amino acid neurotransmitters are also influenced by dietary protein level. Thus, modification of dietary protein level or manipulation of the brain amino acid homeostasis by any other means may be an useful tool to find out a path to restrict amino acid neurotransmitter alterations in aluminum-associated neurodisorders.

4-Aminobutyrate Transaminase↗
PubMed1980

Influence of dietary protein during the pre-breeder period on subsequent reproductive performance of large white turkeys. 2. Growth, feed consumption, and male sex-limited reproductive traits.

the effect of low dietary protein during the rearing and breeding periods on the reproductive performance of Large White turkey males was examined. At 12 weeks of age 251 males were randomly divided into two groups and fed either 12 or 17% protein through 56 weeks of age. Body weight gains from 12 to 20 weeks and 20 to 28 weeks of age were significantly reduced for the males receiving the 12% dietary protein. However, after 28 weeks of age, weight differences decreased and by 56 weeks of age body weights of both groups were approximately the same. In addition, a significant reduction in feed consumption was noted for the males fed 12% protein. Males on the high protein diet experienced a higher mortality than those on the low protein diet. Low dietary protein reduced semen volume and spermatozoa concentration at 33 weeks of age, but there were no significant differences thereafter. The percentages of normal, abnormal, or dead spermatozoa were unaffected by dietary protein levels. Feeding 12% protein from 12 to 56 weeks of age to Large White turkey breeder males was adequate for high quality semen production.

Animals↗
PubMed2000

The response of altering the ratio of dietary protein to energy on growth, feed efficiency, and mammary development in rapidly growing prepubertal heifers.

This study was conducted to evaluate the effects of increasing the ratio of dietary protein to energy above National Research Council recommendations on average daily gain, feed efficiency, structural growth, and indirect measurements of mammary growth. Forty-five Holstein heifers were randomly assigned to either a low, medium, or high ratio of dietary crude protein (CP) to metabolizable energy of 46:1, 54:1, and 61:1 g/Mcal, respectively. The ratio of dietary protein to energy was altered by adjusting the concentration of CP with a similar amount of energy across all diets. Heifers were individually fed and began the treatment period at 200 kg of body weight and 28 wk of age. During the 3-wk adaptation period and 20-wk treatment period, all heifers were fed for a daily dry matter intake (DMI) of 2.45% of body weight. Body weight was monitored for two consecutive days each week and was used to adjust the dry matter offered on a weekly basis. The high versus low ratio of dietary protein to energy increased feed efficiency 6%, which resulted in larger heifers that were subsequently fed 3% more DMI over the course of the trial. The increased feed efficiency and DMI increased average daily gain by 9% for the high versus low ratio of dietary protein to energy. For the high versus low ratio of dietary protein to energy, hip width, hip height, wither height, and heart girth growth was increased 13, 16, 18, and 12%, respectively. The heifers fed the high ratio of dietary protein to energy had a lower rate of increased body condition score compared with the heifers fed the low ratio of dietary protein to energy. Teat length growth was used as an indirect measurement of mammary ductal development and was increased by 35 to 38% for heifers on the high versus low ratio of dietary protein to energy. Feeding dietary ratios of protein to energy above NRC recommendations improved feed efficiency and increased average daily gain, structural growth, and mammary development while decreasing body condition scores in heifers between 28 and 48 wk of age.

Animal Nutritional Physiological Phenomena↗
PubMed1982

The effect of dietary protein quantity on the activity of UDP-glucuronyltransferase and its physiological significance in drug metabolism.

Low dietary protein has been shown to induce the activity of rat hepatic UDP-glucuronyltransferase (UDPGTase) as measured in vitro. The assay of UDPGTase in vitro is hampered by the need to solubilize the microsomal membrane, without destroying the physiological significance of the measurements. The present work was to determine the effect of dietary protein on the activity of UDPGTase and on the activity of UDP-glucose dehydrogenase. Chloral hydrate induced sleeping time was used as a bioassay for UDPGTase, confirming the physiological significance of the in vitro analysis. Sixty male rats were maintained on three different protein levels (7.5, 15, and 45%) for 16 days. Fifteen rats from each group were sacrificed and hepatic UDPGTase, cytochrome P-450, UDP-glucose dehydrogenase, and alcohol dehydrogenase were assayed. Five rats from each group were dosed with 7.5% chloral hydrate (4.8 mL/kg body weight) to measure sleeping time. Rats on 7.5% dietary protein had significantly higher UDPGTase activity than rats fed either 15 or 45% protein diets. These differences in enzyme activity in vitro correlated with the differences in chloral hydrate sleeping time. Dietary protein was not found to affect the activity of UDP-glucose dehydrogenase as measured in vitro.

Animals↗
PubMed1984

Effects of the interrelationship between dietary protein and minerals on tissue content of trace metals in streptozotocin-diabetic rats.

Zinc, iron and copper concentrations were measured in several organs from streptozotocin-diabetic and normal male, Long-Evans rats that were maintained for 21 days on a dietary regimen designed to study the combined or singular effects of insulin-dependent diabetes, dietary protein and dietary minerals on the tissue content of trace metals. The diets contained either 20 ppm zinc and iron, 5 ppm copper and 20% protein (HMHP); 8 ppm zinc and iron, 2 ppm copper and 8.3% protein (LMLP); 20 ppm zinc and iron, 5 ppm copper and 8.3% protein (HMLP) or 8 ppm zinc and iron, 2 ppm copper and 20% protein (LMHP). The concentrations of zinc, iron and copper in liver, zinc and iron in kidney and iron in femur were elevated in the diabetic rats and were not influenced by dietary protein and mineral interaction. However, dietary protein, mineral or protein X mineral interaction significantly affected trace metal concentrations of several organs in diabetic rats but had no significant effect in normal rats. Specifically, copper concentration in kidney and duodenum of diabetic rats were influenced by protein X mineral interaction, duodenal zinc concentrations were higher in diabetic rats fed high mineral diets (HMHP and HMLP) compared to diabetic rats fed low mineral diets (LMHP and LMLP) and femur zinc concentration was higher in diabetic rats fed high protein diets (HMHP and LMLP) compared to diabetic rats fed low protein diets (HMLP and LMLP). While hepatic picolinic carboxylase was elevated severalfold in diabetic rats, it was highest in the diabetic rats fed high protein diets (HPHM and HPLM) suggesting that picolinic acid may, at least in part, mediate the effects of dietary protein and minerals on tissue trace metal concentrations in diabetic rats.

Animals↗
PubMed1997

Influence of dietary protein supplements on the formation of bacterial metabolites in the colon.

BACKGROUND: To evaluate the influence of increased dietary protein intake on bacterial colonic metabolism in healthy volunteers. METHODS: Short chain fatty acids, ammonia, and volatile organic compounds in faecal samples, and phenols in the urine of five volunteers were measured after one week of basal nutrient intake and and after one week of a diet supplemented with a protein rich food (Fortimel; Nutricia, Zoetermeer, The Netherlands). Paired t tests and factor analysis were used for statistical analysis. RESULTS: Total energy and resistant carbohydrate intake remained unchanged in each study period. The percentage energy intake delivered as dietary protein, increased significantly (from 15.4% to 23.8%; p = 0.007) during supplement intake. A significant increase in faecal ammonia (p = 0.002), faecal valeric acid (p = 0.02), and urinary p-cresol (p = 0.04) was noted during supplementary protein intake. A total of 120 different volatile compounds were isolated from the faecal samples of which 10 increased significantly during dietary protein supplementation. The change in volatile pattern, especially for S containing metabolites, was clearly shown by a factor analysis model which made a distinction between the two dietary regimens for all volunteers. CONCLUSION: An increase in dietary protein leads to altered products formation by colonic metabolism, mainly reflected by an increase in faecal ammonia, faecal volatile S substances, and urinary p-cresol.

Adult↗
PubMed1979

Insulin dependent and independent actions of dietary protein on in vitro protein synthesis in skeletal muscle of rats.

Insulin dependency of the effect of dietary protein on in vitro protein synthesis in skeletal muscle was studied in rats. Re-feeding fasted rats with an adequate protein diet caused an increase in protein synthetic activity of skeletal muscle within only 5 hours with a concomitant increase in concentration of polyribosomes. During re-feeding of a protein-free diet muscle protein synthesis increased significantly but it was somewhat lower than in rats fed an adequate protein diet. The concentration of insulin in plasma increased promptly and markedly when the rats were re-fed either of these diets. However, the degree of increase was slightly less in rats fed a protein-containing meal. Re-feeding normal rats with egg albumin alone, after fasting 1 day, produced a marked increase in protein synthetic activity of skeletal muscle with a parallel increase in proportion of polyribosomes in the tissue. The stimulatory action of dietary protein on muscle protein synthesis was not abolished even in streptozotocin-diabetic rats. However, there was no appreciable change in ribosomal profile in the diabetic rats. These results indicate that the function of dietary protein in regulating muscle protein synthesis is not mediated entirely by insulin.

Animals↗