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Dietary effects on the intestinal microflora have gained increasing interest because of the evidence that a balanced micro ecology in the gut is important for health and well being. The aim of the present study was to evaluate the effect of different diets on faecal counts of bifidobacteria and Clostridium perfringens in dogs. Two extruded, dry diets, one supplemented with 3% chicory (1.5% inulin), a non-digestible oligosaccharide (NDO) and the other with 3% glucose (GLU) were compared with a protein rich diet (PR+) based on low quality animal derived protein sources (NDO 265, GLU 259, PR+ 726 g crude protein/kg dry matter; greaves meal and bovine lung as protein sources in PR+). Nine adult beagles were subjected to a consecutive cross-over trial. All dogs started with diet PR+, after which groups of four dogs (group A) received GLU and the other five dogs (group B) received NDO. After an intermediate wash-out period with diet PR+ for 3 weeks the A dogs were switched to diet NDO and B dogs to GLU. In the final period all dogs were fed with diet PR+. Faecal samples were collected during each period for dry matter and pH measurements. Faecal bifidobacteria and Cl. perfringens were quantified in fresh samples at the end of each feeding period and additionally on the first days after feed change from the dry diets to diet PR+. Diets NDO and GLU increased faecal dry matter and reduced faecal pH from 6.9 to 7.4 with the high protein diet to 5.9–6.5. The dry diets induced a firmer faecal consistency and a lower faecal pH, with no significant difference between NDO or GLU. Clostridium perfringens was found in all faecal specimens after feeding PR+ with counts of log 8.2–8.8 colony forming units (cfu)/g faeces. Both dry diets reduced the counts of Cl. perfringens significantly (log 3.3–4.0 cfu/g faeces). Switching from the dry diets to the high protein diet induced an increase of Cl. perfringens within 1 day, independent of the previous diet. In dogs fed PR+, bifidobacteria were detected in only four faecal samples and exclusively in the initial feeding period. During the remainder of the experiment the counts fell below the detection limit (log 6 cfu/g faeces). The faecal concentrations of bifidobacteria increased with both dry diets. Slightly higher concentrations (log 9.6–9.7 cfu/g faeces) were obtained from dogs fed the dry diet containing NDO compared with the diet containing glucose (log 9.3–9.4 cfu/g faeces). The increase was small which may be related to the level of total fermentable carbohydrates in both diets which alone increase remarkably the total counts of bifidobacteria. In conclusion, distinct dietary effects on the faecal counts of Cl. perfringens and bifidobacteria with a clear antagonistic pattern were observed. The main factor was the protein source and level in the diet. In this case, NDO favoured the concentrations of bifidobacteria to a limited degree. Further studies are needed to evaluate time effects, metabolic consequences and the potential implication for health promotion in pets. [ABSTRACT FROM AUTHOR]

Cats conjugate their bile acids with taurine but are unable to synthesize sufficient quantities of this amino acid to meet their needs. To maintain the same blood taurine level, canned foods must contain more taurine than dry foods. In the present study we examined the effect of soluble fiber on fecal bile acid excretion and taurine status and compared the quantity and profile of fecal bile acids in cats fed canned and dry diets. In a cross-over design, 10 adult cats were fed a typical canned diet containing 0.25% kappa carrageenan with or without the addition of 0.5% guar gum (2.5% on a dry matter basis) for 6 wk. All cats were then transferred to a dry diet. The addition of guar gum to the canned diet had no significant effect on taurine status, but the dry diet, which contained less taurine than the canned diet, resulted in an increase in plasma taurine. With the dry diet, total bile acid excretion was reduced by approximately 65%. The profile of bile acids in feces was also radically different with a marked decrease in secondary bile acids. This work suggests that when canned rather than dry diets are fed, the conversion of primary to secondary bile acids is greater and is indicative of an alteration in the activity of the gut flora that may lead to an increase in taurine degradation. [ABSTRACT FROM AUTHOR]

Background & Aims: The acute ingestion of an acetogenic indigestible carbohydrate (lactulose) increased acetate turnover associated with decreased lipolysis (glycerol turnover) in insulin-resistant patients. It is not known whether a decreased lipolysis by chronic ingestion of acetogenic indigestible carbohydrates or fibers improves glucose turnover and insulin sensitivity., Methods: Twenty-one men with metabolic syndrome ingested daily standardized drinks, with or without 28 g acetogenic fibers (acacia gum and pectin), for 5 weeks in a randomized double-blind crossover controlled study design. Euglycaemic-hyperinsulinaemic (EH) clamps coupled with kinetic studies were performed in the fasting state after treatments., Results: Flatulence was more frequent with fiber treatment. Body weight, lipids as well as acetate and glycerol turnovers were unchanged. Fasting endogenous glucose turnover was improved after fiber treatment (7.9 ± 1.3 μmol kg(-1) min(-1)) compared with control (8.6 ± 1.6 μmol kg(-1) min(-1), P < 0.05). But insulin sensitivity (glucose infusion rate) during the EH clamp was not different at the end of fiber and control treatments, 3.7 ± 1.8 and 3.8 ± 1.5 mg kg(-1) min(-1), respectively, nor fasting plasma glucose and insulin., Conclusions: The chronic ingestion of acacia gum and pectin fibers did not decrease lipolysis but improved fasting endogenous glucose turnover with no effect on peripheral insulin resistance in metabolic syndrome patients., (Copyright © 2010. Published by Elsevier Ltd.)

Lycium barbarum (Fructus Lycii, Wolfberry, or Gouqi) belongs to the Solanaceae. The red-colored fruits of L. barbarum have been used for a long time as an ingredient in Chinese cuisine and brewing, and also in traditional Chinese herbal medicine for improving health. However, its effects on cognitive function have not been well studied. In the present study, prevention of a milk-based wolfberry preparation (WP) on cognitive dysfunction was tested in a prenatal stress model with rats and the antioxidant mechanism was tested by in vitro experiments. We found that prenatal stress caused a significant decrease in cognitive function (Morris water maze test) in female offspring. Pretreatment of the mother rats with WP significantly prevented the prenatal stress-induced cognitive dysfunction. In vitro studies showed that WP dose-dependently scavenged hydroxyl and superoxide radicals (determined by an electron spin resonance spectrometric assay), and inhibited FeCl(2)/ascorbic acid-induced dysfunction in brain tissue and tissue mitochondria, including increases in reactive oxygen species and lipid peroxidation and decreases in the activities of complex I, complex II, and glutamate cysteine ligase. These results suggest that dietary supplementation with WP may be an effective strategy for preventing the brain oxidative mitochondrial damage and cognitive dysfunction associated with prenatal stress.

Chicory roots are rich in inulin that is degraded into SCFA in the caecum and colon. Whole-body SCFA metabolism was investigated in rats during food deprivation and postprandial states. After 22 h of food deprivation, sixteen rats received an IV injection of radioactive 14C-labelled SCFA. The volume of distribution and the fractional clearance rate of SCFA were 0.25-0.27 litres/kg and 5.4-5.9 %/min, respectively. The half-life in the first extracellular rapidly decaying compartment was between 0.9 and 1.4 min. After 22 h of food deprivation, another seventeen rats received a primed continuous IV infusion of 13C-labelled SCFA for 2 h. Isotope enrichment (13C) of SCFA was determined in peripheral arterial blood by MS. Peripheral acetate, propionate and butyrate turnover rates were 29, 4 and 0.3 micromol/kg per min respectively. Following 4 weeks of treatment with chicory root or control diets, eighteen fed rats received a primed continuous IV infusion of 13C-labelled SCFA for 2 h. Intestinal degradation of dietary chicory lowered caecal pH, enhanced caecal and colonic weights, caecal SCFA concentrations and breath H2. The diet with chicory supplementation enhanced peripheral acetate turnover by 25 % (P = 0.017) concomitant with an increase in plasma acetate concentration. There were no changes in propionate or butyrate turnovers. In conclusion, by setting up a multi-tracer approach to simultaneously assess the turnovers of acetate, propionate and butyrate it was demonstrated that a chronic chicory-rich diet significantly increases peripheral acetate turnover but not that of propionate or butyrate in rats.

We determined whether the steady-state levels of intestinal mucins are more sensitive than total proteins to dietary threonine intake. For 14 d, male Sprague-Dawley rats (158 +/- 1 g, n = 32) were fed isonitrogenous diets (12.5% protein) containing 30% (group 30), 60% (group 60), 100% (control group), or 150% (group 150) of the theoretical threonine requirement for growth. All groups were pair-fed to the mean intake of group 30. The mucin and mucosal protein fractional synthesis rates (FSR) did not differ from controls in group 60. By contrast, the mucin FSR was significantly lower in the duodenum, ileum, and colon of group 30 compared with group 100, whereas the corresponding mucosal protein FSR did not differ. Because mucin mRNA levels did not differ between these 2 groups, mucin production in group 30 likely was impaired at the translational level. Our results clearly indicate that restriction of dietary threonine significantly and specifically impairs intestinal mucin synthesis. In clinical situations associated with increased threonine utilization, threonine availability may limit intestinal mucin synthesis and consequently reduce gut barrier function.

In young men ingesting protein meals, slowly digested proteins (caseins: CAS) induce a higher protein gain than those that are rapidly digested (whey proteins: WP). Our aim was to assess whether or not this is true in elderly men receiving mixed meals. The effects of meals containing either CAS or two different amounts of WP (WP-iN: isonitrogenous with CAS, or WP-iL: providing the same amount of leucine as CAS) on protein metabolism (assessed by combining oral and intravenous leucine tracers) were compared in nine healthy, elderly (mean +/- S.E.M. age 72 +/- 1 years) and six young men (24 +/- 1 years). In both age groups, WP-iL and WP-iN were digested faster than CAS (P < 0.001, ANOVA). Proteolysis was inhibited similarly whatever the meal and age groups (P = NS). Protein synthesis was higher with WP-iN than with CAS or WP-iL (P < 0.01), irrespective of age (P = NS). An age-related effect (P < 0.05) was found with postprandial leucine balance. Leucine balance was higher with CAS than with WP-iL (P < 0.01) in young men, but not in elderly subjects (P = NS). In isonitrogenous conditions, leucine balance was higher with WP-iN than with CAS (P < 0.001) in both age groups, but the magnitude of the differences was higher in the elderly men (P = 0.05). In conclusion, during aging, protein gain was greater with WP (rapidly digested protein), and lower with CAS (slowly digested protein). This suggests that a 'fast' protein might be more beneficial than a 'slow' one to limit protein losses during aging.

The intestinal mucoprotein synthesis rate was measured in vivo for the first time. For this, a rapid, reproducible, and convenient method to purify mucoproteins from large numbers of intestinal samples at the same time was developed. The method takes advantage of both the high mucin resistance to protease activities due to their extensive glycosylations and the high mucin molecular size. Intestinal homogenates were partially digested with Flavourzyme. Nonprotected proteins partially degraded were easily separated from mucoproteins by small gel filtration chromatography using Sepharose CL-4B. Electrophoretically pure mucins were obtained. Their amino acid composition was typical of purified intestinal epithelial mucins. The mucoprotein synthesis rate was determined in vivo in rats using the flooding dose method with the stable isotope L-[1-13C]valine. Free L-[1-13C]valine enrichments in the intracellular pool were determined by GC-MS. L-[1-13C]valine enrichments into purified mucoproteins or intestinal mucosal proteins were measured by gas chromatography-combustion-isotope ratio mass spectrometry. In rats, we found that the gut mucosa protein synthesis rate (%/day) decreased regularly from duodenum (122%/day) to colon (43%/day). In contrast, mucoprotein fractional synthesis rates were in the same range along the digestive tract, between 112%/day (colon) and 138%/day (ileum).

The objectives of the present study were to determine the splanchnic extraction of glutamine after ingestion of glutamine-rich protein ((15)N-labeled oat proteins) and to compare it with that of free glutamine and to determine de novo glutamine synthesis before and after glutamine consumption. Eight healthy adults were infused intravenously in the postabsorptive state with L-[1-(13)C]glutamine (3 micromol x kg(-1) x h(-1)) and L-[1-(13)C]lysine (1.5 micromol x kg(-1) x h(-1)) for 8 h. Four hours after the beginning of the infusion, subjects consumed (every 20 min) a liquid formula providing either 2.5 g of protein from (15)N-labeled oat proteins or a mixture of free amino acids that mimicked the oat-amino acid profile and contained L-[2,5-(15)N(2)]glutamine and L-[2-(15)N]lysine. Splanchnic extraction of glutamine reached 62.5 +/- 5.0% and 66.7 +/- 3.9% after administration of (15)N-labeled oat proteins and the mixture of free amino acids, respectively. Lysine splanchnic extraction was also not different (40.9 +/- 11.9% and 34.9 +/- 10.6% for (15)N-labeled oat proteins and free amino acids, respectively). The main conclusion of the present study is that glutamine is equally bioavailable when given enterally as a free amino acid and when protein bound. Therefore, and taking into consideration the drawbacks of free glutamine supplementation of ready-to-use formulas for enteral nutrition, protein sources naturally rich in this amino acid are the best option for providing stable glutamine.

To evaluate the importance of protein digestion rate on protein deposition, we characterized leucine kinetics after ingestion of "protein" meals of identical amino acid composition and nitrogen contents but of different digestion rates. Four groups of five or six young men received an L-[1-13C]leucine infusion and one of the following 30-g protein meals: a single meal of slowly digested casein (CAS), a single meal of free amino acid mimicking casein composition (AA), a single meal of rapidly digested whey proteins (WP), or repeated meals of whey proteins (RPT-WP) mimicking slow digestion rate. Comparisons were made between "fast" (AA, WP) and "slow" (CAS, RPT-WP) meals of identical amino acid composition (AA vs. CAS, and WP vs. RPT-WP). The fast meals induced a strong, rapid, and transient increase of aminoacidemia, leucine flux, and oxidation. After slow meals, these parameters increased moderately but durably. Postprandial leucine balance over 7 h was higher after the slow than after the fast meals (CAS: 38 +/- 13 vs. AA: -12 +/- 11, P < 0.01; RPT-WP: 87 +/- 25 vs. WP: 6 +/- 19 micromol/kg, P < 0.05). Protein digestion rate is an independent factor modulating postprandial protein deposition.

Objective: To evaluate intestinal permeability and absorption in healthy cats in association with diet and normal intestinal microflora., Animals: 6 healthy domestic shorthair cats., Procedure: A sugar solution containing D-xylose, 30-methyl-D-glucose, L-rhamnose, lactulose, and 51Cr-EDTA was administered intragastrically to healthy cats, and urinary excretion of ingested sugars was determined 5 hours after administration. After the same cats had received metronidazole for 1 month, the study was repeated. A final study was performed while cats were maintained on a new diet differing in composition and processing., Results: Lactulose-to-rhamnose ratios, reflecting intestinal permeability, were higher in cats, compared with values for humans or dogs, and values obtained before and after metronidazole administration (mean +/- SEM; before, 0.40 +/- 0.08; after, 0.45 +/- 0.09) were not significantly different. Intestinal absorption also was unaltered after antibiotic administration, and the xylose-to-glucose ratio was 0.70 +/- 0.03 before and 0.71 +/- 0.06 after metronidazole administration. Sugar recovery did not differ significantly while cats were maintained on canned or dry food., Conclusions and Clinical Relevance: Reference ranges were established for the percentage urinary recovery of orally administered D-xylose, 3-0-methyl-D-glucose, L-rhamnose, lactulose, and 51Cr-EDTA obtained after 5 hours in healthy cats. The intestines of cats appear to be more permeable than those of other species, although the normal bacterial microflora does not appear to influence the integrity or function of the feline intestine, because values obtained for the measured variables before or after antibiotic administration were not significantly different. In addition, differences were not detected when the diet was completely altered.

Objective: To determine whether a colony environment predisposes healthy cats to high bacterial counts, including counts of obligate anaerobes, in the duodenum and whether increased numbers of bacteria could be found in the duodenum of cats with signs of chronic gastrointestinal tract disease., Design: Prospective study., Animals: 20 healthy control cats (10 from a colony environment and 10 pet cats) and 19 cats with a history of chronic gastrointestinal tract disease., Procedure: Undiluted duodenal fluid was quantitatively and qualitatively assessed by bacteriologic culture under aerobic and anaerobic conditions. Serum concentrations of cobalamin and folate were also measured., Results: Significant differences were not detected in the numbers of bacteria found in the duodenum of cats housed in a colony environment, compared with pet cats fed an identical diet prior to sampling. All healthy cats were, therefore, combined into 1 control group. Compared with healthy cats, cats with clinical signs of gastrointestinal tract disease had significantly lower counts of microaerophilic bacteria, whereas total, anaerobic, and aerobic bacterial counts were not significantly different. None of the cats with disease had total bacterial counts higher than expected from the range established in the control cats. Differences were not detected in regard to serum folate or cobalamin concentrations between diseased and healthy cats., Conclusions and Clinical Relevance: These findings indicated that healthy colony cats and pet cats have high numbers of bacteria in the duodenum, including high numbers of obligate anaerobes. Our findings also suggest that bacterial overgrowth in the small intestine is not a common clinical syndrome in cats with chronic nonobstructive gastrointestinal tract disease.

Although glutamine status in the critically ill patient can be improved by nutritional means, the most effective way of effecting such supplementation has received little attention. We evaluated two different ways of supplementing clinical nutrition products with glutamine, either with free glutamine or by providing a glutamine-rich protein source, in acute glucocorticoid-treated (intraperitoneal dexamethasone, 120 mg/kg) rats. During the recovery period, the animals received isonitrogenous and isoenergetic diets containing either casein, mixed whey proteins with or without glutamine, or carob protein plus essential amino acids. Plasma and tissue amino acids and glutathione as well as tissue protein synthesis were measured. Dexamethasone treatment lowered weight gain, muscle glutamine, and muscle and jejunal protein synthetic rate. Muscle protein synthesis was increased (from 15.9% to 24.2%/d) only when glutamine was included in the diet as a free amino acid. This increase paralleled a rise in plasma glutamine. We speculate that glutamine provided in dietary protein is extensively metabolized by the splanchnic tissues and does not influence peripheral glutamine status to the same extent as glutamine provided in a free amino acid form. However, both forms of glutamine supplementation were equally effective in increasing protein synthesis in the jejunum (by 25%). This is likely the main benefit of glutamine supplementation of enteral nutrition formulas.

The goal of the present work was to compare the plasma glutamine response to exogenous glutamine administration in human volunteers; glutamine was provided as a free amino acid, bound to proteins, or in the form of peptides. Plasma glutamine concentrations were measured in eight human volunteers at 30, 60, 90, 120, and 240 min after receiving a drink containing 30 g of protein from one of the five different proteins tested (sodium caseinate, sodium caseinate + free glutamine, carob germ flour, carob protein concentrate, and carob protein hydrolysate). Peak plasma glutamine concentrations were 42% higher than postabsorptive basal values when exogenous glutamine was administered in the form of free glutamine added to caseinate (925.9 +/- 67.7 versus 651.3 +/- 44.0 micromol/L, respectively). In contrast, when glutamine was offered 100% bound to proteins (carob proteins), peak plasma glutamine concentration increased only between 18% and 23% from basal values, possibly because of the lower digestibility of carob proteins versus that of caseinate + free glutamine, to a different glutamine utilization at the gut level, or to a different response in endogenous glutamine kinetics to enteral administration of glutamine, depending on the molecular form of the glutamine source (free or protein bound).

Objective: To determine effects of oral administration of metronidazole on the number and species of duodenal bacteria and selective nutrients of cats., Animals: 6 healthy domestic shorthair cats., Procedure: Undiluted duodenal fluid was obtained for quantitative and qualitative bacterial culture to determine species and number of bacteria in healthy cats. Blood samples were assayed for taurine, total protein, albumin, cobalamin, and folate concentrations. Cats then were given metronidazole (20 mg/kg of body weight, PO, q 12 h) for 1 month, after which bacterial cultures and serum assays of nutrients were repeated. Nine months after cessation of antibiotic treatment, duodenal bacteria were re-evaluated and serum was assayed for total protein, albumin, cobalamin, and folate concentrations., Results: Oral administration of metronidazole caused a significant decrease in aerobic and anaerobic bacterial counts in the duodenum of healthy cats, accompanied by emergence of Streptococcus spp and Corynebacterium spp. Serum concentrations of cobalamin and albumin increased when duodenal bacterial counts were decreased, although changes in folate or taurine concentrations were not detected. Measured variables did not differ, when comparing results obtained before and 9 months after cessation of metronidazole., Conclusions and Clinical Relevance: Oral administration of metronidazole decreased the number of aerobic bacteria and altered indigenous flora in the small bowel of cats. Normal duodenal flora appeared to be stable, because species of bacteria were re-established by 9 months after cessation of metronidazole. Bacterial flora appeared to have an impact on nutrients, because albumin and cobalamin increased during antibiotic administration and returned to preadministration concentrations after cessation of the antimicrobial.

Background: The body's nucleotide pool derives from three potential sources: de novo synthesis, salvage of preformed-nucleosides/bases or the diet. The relative contributions of these pathways of assimilation are poorly understood in vivo. Dietary nucleotides have been suggested to have beneficial effects an the development and repair of the gastrointestinal tract. Tissues with a rapid turnover, such as the gut and the immune system cells, may utilise preformed nucleotides (coming from the diet), in situations in which there is a high demand of nucleotides for nucleic acid synthesis. Therefore, nucleotides could be considered as conditionally essential nutrients., Aim of the Work and Methods: Development of a method to measure synthesis de novo of RNA-purine nucleotides in Caco-2 cells, relying an the incorporation of 14C-glycine into the purine ring of the nucleotide. To establish the fractional synthesis rate of RNA purine nucleotides in Caco-2 cells, grown in culture medium containing different concentrations of glutamine, in the presence or absence of added nucleotides. To investigate the degree to which tissue ribonucleosides are derived from the culture medium or from de novo synthesis in the presence of different concentrations of glutamine, using undifferentiated Caco-2 cells, stressed or not by the addition of IL-1 beta to the medium., Results and Conclusions: The presence of high levels of glutamine in the culture medium is essential for cell proliferation (estimated by measurement of the fractional synthesis rate of purine nucleotides) and the presence of nucleotides cannot replace the glutamine dependence of Caco-2 cell proliferation. The incorporation of exogenous purine nucleotides into RNA of Caco-2 cells is rather limited, and it becomes important when cells are stressed by glutamine deprivation. Stress by addition of interleukin-1 beta resulted in the maintenance or the increase in de novo synthesised RNA-purine nucleotides, even in the presence of exogenous nucleotides. However, the addition of interleukin-1 beta to the culture medium led to an enhanced salvage of preformed pyrimidine nucleotides for nucleic acid synthesis when glutamine was present in the medium at a concentration of 0.5 mmol/L.

To understand the biological function of taurine, a study of taurine kinetics in the cat was undertaken. This paper describes a method developed for the accurate determination of 15N-taurine enrichment in cat urine by gas chromatography-mass spectrometry. 15N-Taurine was given to six animals as an oral bolus dose of 20 mg/kg body weight, and the urine was pooled on a daily basis. The hydrolysed or non-hydrolysed urine samples (for total and free taurine, respectively) were directly derivatized without further purification. The N-pentafluorobenzoyl di-n-butyl amide derivative obtained was analysed, and the fragment [M-(di-n-butyl amide)]+, carrier of the labelled nitrogen atom, was selectively recorded at m/z 302 (14N-taurine) and m/z 303 (15N-taurine). Calibration curves prepared in hydrolysed and non-hydrolysed urine samples spiked with 15N-taurine gave similar slopes to the calibration curve prepared in water. The average coefficient of variation observed for the mole percent excess in the non-hydrolysed samples was 1.22% (n = 92) and for the hydrolysed urine 1.00% (n = 98). There was no significant difference between free and total taurine enrichment. The half-life of taurine in cat body was found to be 29.3 +/- 2.9 h and 35.0 +/- 1.4 h for free and total taurine, respectively (non-significant). The taurine body pool, calculated by extrapolation of the curve to zero time, had a value of 137 +/- 22 ng/kg and 157 +/- 11 mg/kg for free and total taurine, respectively.

The effects of a daily porcine somatotropin injection on protein synthesis rate in muscle (longissimus), liver and intestine, as influenced by dietary protein, were investigated in 17 pigs. The measurements were made at wk 3 of treatment following 1 wk for adaptation to the diet and 1 wk for determination of nitrogen balance. The fractional rates of protein synthesis in the muscle, liver and intestine were measured using a flooding dose of L-[1-13C]valine. Positive responses of weight gain and nitrogen balance were observed, primarily at higher dietary protein intake, after porcine somatotropin treatment. As expected, porcine somatotropin-treated pigs had a higher proportion of muscle and less fat. Fractional protein synthesis rate was 16% higher in the liver of porcine somatotropin-treated pigs (P < 0.05). In the longissimus muscle fractional protein synthesis rate increased with porcine somatotropin dose from 3.2 to 3.7%/d and from 4.1 to 5.1%/d at low and high protein intake, respectively (P < 0.05). The effect of dietary protein on fractional protein synthesis rate in longissimus was significant, but there was no porcine somatotropin x protein interaction. Ribonucleic acid concentration followed the same pattern as fractional protein synthesis rate in liver and longissimus. In the duodenal tissue, porcine somatotropin treatment depressed fractional protein synthesis rate (P < 0.05) without an effect of dietary protein and RNA concentration did not change. In porcine somatotropin compared with placebo-treated pigs, plasma glucose, insulin and insulin-like growth factor-I concentrations were elevated whereas plasma thyroxine was depressed and plasma triiodothyronine remained constant. There was no clear effect of dietary protein on plasma hormones. We concluded that, in pigs fed an adequate level of protein, porcine somatotropin stimulates protein synthesis in the liver and the muscle, primarily through increased ribosomal capacity.

A method is described for measuring the stable isotopic enrichment of taurine in cat urine samples by high resolution fast-atom bombardment mass spectrometry, after 15N labelled taurine was given to cats for the purpose of investigating taurine metabolism. The 15N enrichment of taurine was measured after hydrolysis and purification of taurine by anion/cation exchange chromatography. The isotopic ratio of taurine was determined by measuring the [M+H]+ ion peaks in the spectra of the unlabelled and labelled compounds under multiple ion scan conditions. The overall standard deviation of the measurement is better than 4%. This method requires no derivation and uses only 500 microL of urine samples.

Kinetic aspects of threonine (Thr) metabolism were examined in growing pigs fed a well-balanced diet (C), an isocaloric protein-free diet (PF), or starved (S) for 48 h. With the use of continuous simultaneous infusion of L-[1-13C]Thr, [1-14C]sarcosine, and 2-[1-14C]ketobutyrate (KB) for 10 h, estimates were made of rates of Thr incorporated into protein (S), released from body proteins (B), and oxidized through the catabolic pathways of L-Thr 3-dehydrogenase (TDG) and threonine dehydratase (TDH). In the C group S was 185, B was 138, Thr disposal to glycine (DRThr-Gly) was 47, and Thr disposal to KB (DRThr-KB) was 7 mumol.h-1.kg-1. Consequently, Thr balance was +48 mumol.h-1.kg-1. In the PF-fed pigs, S, B, DRThr-Gly, and DRThr-KB were significantly reduced by 38, 15, 74, and 75%, respectively. In the S group, S, B, and DRThr-Gly were significantly reduced by 47, 17, and 55%, respectively, but DRThr-KB was similar to the C group. DRThr-Gly in all groups was highly correlated with TDG enzyme activity measured in liver homogenates. By contrast with in vivo results, TDH enzyme activity was increased by 88% (P less than 0.05) in the S group and decreased by 27% (not significant) in the PF group compared with the C group. The TDH pathway accounted for 13, 12, and 27% of total Thr oxidation in the C, PF, and S groups, respectively. These results suggest that Thr conservation in protein-depleted states (PF and S groups) occurred mainly by a decrease of Thr oxidation and that the partition through these pathways was only altered when energy was completely withdrawn.

To investigate in vivo the interconversion between glycine (Gly) and its N-methyl product sarcosine (Sar), [1-13C]Gly and [1-14C]Sar were infused into hourly fed pigs receiving diets with low- and high-threonine levels. An open two-pool model was developed to calculate Sar demethylation (DM) and Gly methylation (GM). During [1-14C]Sar infusion, intracellular Gly specific radioactivities (SA) in the liver and kidney were higher than plasma Gly SA, suggesting that demethylation of Sar occurred in those tissues. DM estimated by using hippuric acid (HA) as the production pool had a mean value of 1.55 mumol.kg-1.h-1, similar to the Sar production rate (mean 1.85 mumol.kg-1.h-1). GM was undetectable (less than 0.5 mumol.kg-1.h-1). These results suggest that, in fed pigs, Sar is produced mainly from choline catabolism and is degraded only to Gly in liver and kidney. On the assumption that Sar degradation gave rise only to Gly, the production rate of Gly (Gly PR) was calculated from [1-13C]Gly and [1-14C]Sar infusions using either the primary pools (plasma Gly and HA, respectively) or the secondary pools (HA and plasma Gly, respectively). The results were explained by a liver-plasma Gly exchange model. The whole body Gly irreversible loss, i.e., direct loss from plasma and liver, was calculated from this model to be 832 +/- 58 mumol.kg-1.h-1, showing that the estimation of Gly PR with [1-13C]Gly infusion and plasma Gly enrichment (599 +/- 56 mumol.kg-1.h-1) was a significant underestimate of the true value.(ABSTRACT TRUNCATED AT 250 WORDS)