High-protein-low-carbohydrate diet during pregnancy alters maternal plasma amino acid concentration and placental amino acid extraction but not fetal plasma amino acids in pigs.

A high protein-low-carbohydrate diet during pregnancy can cause intra-uterine growth restriction. However, its impact during pregnancy on maternal, umbilical and fetal plasma amino acid (AA) profiles is unknown. A maternal high-protein (30 %)-low-carbohydrate (HP-LC) diet was compared with isoenergetic standard (12·1 % crude protein; ST) and low-protein (6·5 %)-high-carbohydrate (LP-HC) diets fed to nulliparous pregnant sows to examine changes in AA concentrations in maternal, venous and arterial umbilical and fetal plasma in mid and late pregnancy. At 64 and 94 days of pregnancy (dp), sows underwent Caesarean section, and maternal, umbilical and fetal plasma samples were collected. The HP-LC diet mainly affected maternal plasma AA concentrations. Plasma concentrations of Ile and Val were increased and those of Ala, Glu and Gly were decreased (P ≤ 0·05) in HP-LC compared with ST sows at 64 and 94 dp. The LP-HC diet decreased fetal plasma Glu concentration compared with the ST diet at 94 dp. Substantial AA catabolism was reflected by increased (P ≤ 0·05) maternal and fetal plasma urea concentrations with the HP-LC compared with the ST and LP-HC diets at 94 dp. Fractional placental extraction of Val was higher whereas those of Ala, Gln and Glu were lower in the HP-LC compared with the ST sows at 64 and 94 dp (P ≤ 0·05). Reduced fetal mass at 94 dp was accompanied by reduced fetal extraction of Lys and Pro in the HP-LC group (P ≤ 0·05). In conclusion, a maternal HP-LC diet during pregnancy altered maternal plasma composition of many AA and modified placental AA extraction to compensate for imbalanced maternal nutrient intake.

Intrauterine growth retarded progeny of pregnant sows fed high protein:low carbohydrate diet is related to metabolic energy deficit.

High and low protein diets fed to pregnant adolescent sows led to intrauterine growth retardation (IUGR). To explore underlying mechanisms, sow plasma metabolite and hormone concentrations were analyzed during different pregnancy stages and correlated with litter weight (LW) at birth, sow body weight and back fat thickness. Sows were fed diets with low (6.5%, LP), adequate (12.1%, AP), and high (30%, HP) protein levels, made isoenergetic by adjusted carbohydrate content. At -5, 24, 66, and 108 days post coitum (dpc) fasted blood was collected. At 92 dpc, diurnal metabolic profiles were determined. Fasted serum urea and plasma glucagon were higher due to the HP diet. High density lipoprotein cholesterol (HDLC), %HDLC and cortisol were reduced in HP compared with AP sows. Lowest concentrations were observed for serum urea and protein, plasma insulin-like growth factor-I, low density lipoprotein cholesterol, and progesterone in LP compared with AP and HP sows. Fasted plasma glucose, insulin and leptin concentrations were unchanged. Diurnal metabolic profiles showed lower glucose in HP sows whereas non-esterified fatty acids (NEFA) concentrations were higher in HP compared with AP and LP sows. In HP and LP sows, urea concentrations were 300% and 60% of AP sows, respectively. Plasma total cholesterol was higher in LP than in AP and HP sows. In AP sows, LW correlated positively with insulin and insulin/glucose and negatively with glucagon/insulin at 66 dpc, whereas in HP sows LW associated positively with NEFA. In conclusion, IUGR in sows fed high protein:low carbohydrate diet was probably due to glucose and energy deficit whereas in sows with low protein:high carbohydrate diet it was possibly a response to a deficit of indispensable amino acids which impaired lipoprotein metabolism and favored maternal lipid disposal.

Effect of inulin supplementation on selected gastric, duodenal, and caecal microbiota and short chain fatty acid pattern in growing piglets.

We explored whether bifidobacteria and lactobacilli numbers and other selected bacteria in the upper intestine and the caecum of growing pigs were affected by diet and intake of inulin. Starting at two weeks after weaning (28 d) 72 pigs were fed two types of diets (wheat/barley (WB) or maize/gluten (MG)), without or with 3% inulin (WB + I, MG + I) for three and six weeks. Intestinal bacteria were quantified by fluorescence-in-situ-hybridization (n = 8/group). Duration of feeding had no effect on the variables tested, so data for both periods were pooled. Gastric total bacteria amounted to log(10) 7.4/g digesta. Bifidobacteria were detected in stomach and duodenum two weeks after weaning and disappeared thereafter. In jejunum and caecum bifidobacteria were present at a level of log(10) 7.0/g digesta. Inulin did not alter numbers of lactobacilli, bifidobacteria, enterococci, enterobacteria and bacteria of the Clostridium coccoides/Eubacterium rectale-group. Inulin disappearance in stomach plus jejunum was higher with the MG diet (73.7 vs. 60.7%, p = 0.013). Caecal acetate was lower in inulin-supplemented diets (p < 0.05) whereas propionate and butyrate were higher in pigs fed the WB diets (p < 0.05). With the WB diet total caecal short chain fatty acids concentration was higher which resulted in a lower pH value (p < 0.05).

Studies on persisting effects of soy-based compared with amino acid-supplemented casein-based diet on protein metabolism and oxidative stress in juvenile pigs.

Juvenile growing pigs were studied to explore whether a soy-based diet can induce persistent physiological alterations, especially in protein and energy metabolism, nutrient oxidation and redox homeostasis. In former studies we have shown that in juvenile pigs chronically fed protein diets based on either casein (CAS) or soy protein isolate (SPI), the SPI diet significantly decreases growth rate and increases oxidative stress responsiveness as compared to CAS. In addition, here we show that chronic feeding of SPI vs. CAS diet decreases whole body protein synthesis (WBPS) (p = 0.007) and hepatic gene expression associated with protein synthesis. To study persistent SPI effects, a three-period feeding experiment was designed: In the test group 18 pigs received the CAS diet for 24 days (period 1), followed by 31 days on the SPI diet (period 2) and further 31 days on the CAS diet (period 3). In the control group 18 pigs were fed the CAS diet throughout the three periods (86 days). Temporary consumption of SPI diet results in persistent changes of protein metabolism and oxidative stress responsiveness. After switching back from SPI to CAS diet the decrease of WBPS of the test group vs. control group was of borderline significance (p = 0.061), transcript levels of hepatic gene expressions of leucine aminopeptidase, endopeptidase 24.16, glutathione-S-transferase and peptide methionine sulfoxide reductase were increased. In liver tissue, total glutathione was increased and thiobarbituric acid reactive substances were decreased in the test vs. control group. In conclusion, results suggest that SPI-induced changes in protein and amino acid metabolism as well as in redox homeostasis and antioxidative potential in growing pigs persist 4 weeks after the cessation of SPI feeding.

First-pass metabolism limits the intestinal absorption of enteral alpha-ketoglutarate in young pigs.

Our results in a previous study indicated that the portal absorption of intragastrically fed alpha-ketoglutarate (AKG) was limited in young pigs. Our aim was to quantify the net portal absorption, first-pass metabolism, and whole-body flux of enterally infused AKG. In study 1, we quantified the net portal nutrient absorption in young pigs (n = 9) given an intraduodenal infusion of milk replacer [10 mL/(kg . h)] and either saline (control) or 930 micromol/(kg . h) AKG for 4 h. In study 2, we quantified the luminal disappearance of a duodenal AKG bolus in young pigs (n = 7). In study 3, we quantified the whole-body kinetics of (13)C-AKG metabolism when infused either enterally (n = 9) or intravenously (n = 9) in young pigs. In study 1, when compared with the control group, enteral AKG infusion increased (P < 0.01) the arterial (13.8 +/- 1.7 vs. 27.4 +/- 3.6 micromol/L) and portal (22.0 +/- 1.4 vs. 64.6 +/- 5.9 micromol/L) AKG concentrations and the net portal absorption of AKG [19.7 +/- 2.8 vs. 95.2 +/- 12.0 micromol/(kg . h)]. The mean fractional portal appearance of enterally infused AKG was 10.23 +/- 1.3%. In study 2, the luminal disappearance of AKG was 663 micromol/(kg . h), representing 63% of the intraduodenal dose. In study 3, the whole-body (13)C-AKG flux [4685 +/- 666 vs. 801 +/- 67 micromol/(kg . h)] was higher (P < 0.05) when given enterally than intravenously, but (13)CO(2) recovery was not different (37.3 +/- 1.0 vs. 36.2 +/- 0.7%dose). The first-pass splanchnic (13)C-AKG utilization was approximately 80%, of which 30% was oxidized to (13)CO(2). We conclude that the intestinal absorption of AKG is limited in young pigs largely due to substantial first-pass gastrointestinal metabolism.

Effect of partial dehulling of two- and six-row barley varieties on precaecal digestibility of amino acids in pigs.

Five barrows (German Landrace; initial BW 58 kg, final BW 80 kg) fitted with an ileo-rectal anastomosis were used to determine the effect of partial dehulling and addition of barley hulls of two- and six-row barley varieties on the precaecal digestibility (pD) of CP and amino acids. The following diets were provided according to a standardized diet formulation and tested in seven consecutive periods (repeated group-period design): two-row barley (TRB) + casein (C), dehulled TRB + C, TRB + C + 10% hulls, six-row barley (SRB) + C, dehulled SRB + C, SRB + C + 1% hulls, and wheat starch + C. The diets were supplied at daily rates of 79-86 g DMI x kg BW(-0.75) in barley containing diets and at 49 g DMI x kg BW(-0.75) in the casein diet. The digestibility of amino acids in barley varieties was determined by the difference method (casein as basal diet) using quantitative digesta collection. In both varieties of barley the pD of CP and amino acids did not differ. The pD of CP was unchanged in regard to the treatments in both barley varieties. Due to dehulling in TRB the pD was improved significantly for most indispensable amino acids and in SRB for Met and Cys. Addition of 10% hulls to TRB led to equivalent pD of Arg, His, Leu, Tyr, and Trp compared to TRB, but the pD of Lys, Phe, Thr and Val was significantly decreased below the levels of TRB. Addition of even 1% hulls to SRB impaired the pD of Lys below the level in SRB. In conclusion, addition of barley hulls to pig diets impairs amino acids absorption in the small intestine. The pD values, measured under standardized experimental conditions (without a correction using basal endogenous amino acids), are similar to the values of true digestibility published by NRC (1998).

Inulin alters the intestinal microbiota and short-chain fatty acid concentrations in growing pigs regardless of their basal diet.

Inulin stimulates intestinal bifidobacteria in humans and rodents but its effect in pigs is inconsistent. We assessed the effect of inulin on the intestinal microbiota by fluorescent in situ hybridization in growing pigs (age 9-12 wk). Pigs (n = 64) were assigned to 2 types of basal diets [wheat and barley (WB) or corn and wheat gluten (CG)] with or without 3% inulin (WBI or CGI) for 3 and 6 wk (n = 8/group) to test whether naturally occurring dietary fibers influence the inulin effect. Intestinal organic acids, pH values, and residual inulin were determined. The composition of the microbiota was highly individual. The duration of feeding did not affect any of the variables tested; therefore, data for the 2 periods were pooled. Bifidobacteria were detected in less than half of the pigs. Inulin did not stimulate lactobacilli and bifidobacteria numbers irrespective of the basal diet, although 20-50% of inulin was degraded in the jejunum. The number of pigs with colonic bifidobacteria was higher in those fed diets containing inulin (40 vs. 13%; P < 0.05). Total colonic short-chain fatty acid (SCFA) concentrations were lower in both inulin-fed groups due to reduced acetate (P < 0.05). Proportions of colonic butyrate were higher in pigs fed inulin-supplemented diets (P < 0.05). Colonic pH tended to be lower in the WB groups (WB; 6.6 +/- 0.6), and was higher due to inulin (CGI, 7.1 +/- 0.1; P < 0.05). In conclusion, inulin affected intestinal SCFA and the number of pigs harboring bifidobacteria; this effect was independent of the basal diet.

Intraduodenal infusion of alpha-ketoglutarate decreases whole body energy expenditure in growing pigs.

BACKGROUND AND AIMS: alpha-Ketoglutarate (AKG) has been suggested to play a particular role as an oxidative fuel for the gut, and thus may have a sparing function for fuels such as glutamate and aspartate. Using the pig model we aimed to quantify how the route of administration (intravenous, i.v.; intragastric, i.g.; intraduodenal, i.d.) affects AKG utilization, whole body energy expenditure (EE) and nutrient oxidation. METHODS: Pigs (15 kg) were supplied with a complete nutrient solution (NS) via catheters. To explore the metabolic effects of AKG, 1.0 g AKG kgBW(-1)d(-1) was infused simultaneously with the NS using either the i.d., i.v. or i.g. route. [1-(13)C]AKG (15 mg kgBW(-1)) was infused i.d., i.v. or i.g., respectively, for 3h. AKG utilization (AKG UTIL) was estimated as AKG UTIL=100-(13)C recovery (% of (13)C dose). (13)C recovery was calculated from the (13)C enrichment in breath CO(2) and the whole-body CO(2) production. RESULTS: AKG infusion and NS via the i.d. route resulted in a reduced AKG UTIL (40.1+/-6.7) as compared to the i.v. route (62.9+/-2.4, P<0.001) and i.g. route (62.3+/-1.6, P<0.001). The total EE was lower with the i.d. route of AKG and NS (745+/-68 kJkgBW(-0.62)d(-1)) as compared to the i.v. route (965+/-54 kJkgBW(-0.62)d(-1), P<0.005) and i.g. route (918+/-43 kJkgBW(-0.62)d(-1), P<0.005). Carbohydrate oxidation was increased with the i.d. route (38.2g+/-3.4 kgBW(-0.62)d(-1)) as compared to the i.v. route (27.8+/-2.9 gkgBW(-0.62)d(-1), P<0.08) and i.g. route (23.9+/-8.5 gkgBW(-0.62)d(-1), P<0.05). Fat oxidation was decreased (2.1+/-1.9 gkgBW(-0.62)d(-1); P<0.001) with the i.d. route as compared to the i.v. route (11.5+/-1.4 gkgBW(-0.62)d(-1), P<0.001) and i.g. route (11.9+/-3.1 gkgBW(-0.62)d(-1), P<0.001). CONCLUSIONS: The i.d. infusion of AKG in combination with the NS affected the whole body EE and nutrient oxidation, in comparison to that obtained with the i.v. and i.g. routes. It was concluded that the i.d. administration of AKG markedly controlled the nutrient partitioning in the oxidation processes. Finally, in contrary to the observations with glutamine or glutamate, a considerable percentage of the AKG infusion was retained in the body irrespective of the route of administration.

Contribution of intestinal microbial lysine to lysine homeostasis is reduced in minipigs fed a wheat gluten-based diet.

BACKGROUND: We previously reported microbial lysine contribution to plasma lysine homeostasis in humans with an adequate lysine intake. OBJECTIVE: We sought to explore whether the low lysine intake from a wheat gluten-based diet is balanced by enhanced microbial lysine contribution in a pig model. DESIGN: Twenty miniature pigs (minipigs) fitted with ileo-ileal cannulas were fed 2 wheat gluten-based diets. One diet provided 2.7 g lysine/kg diet (WG diet) and one diet was supplemented with crystalline lysine to provide 6.6 g lysine/kg diet (WG+Lys diet). Both diets were fed for 10 or 100 d (n = 5 per group): 10WG+Lys, 10WG, 100WG+Lys, and 100WG diets. Ileal microbial lysine, which we considered to be the precursor pool for absorption, was labeled by oral administration of (15)NH(4)Cl for the final 10 d. On days 10 and 100, a 10-h fast-fed tracer protocol with [1-(13)C]lysine was performed. RESULTS: Lysine rates of appearance decreased by 25% with the WG diet in the fed state but increased by 50% with the WG+Lys diet in the fasted state (P < 0.05). Daily gross microbial lysine contribution was lower (P < 0.05) with the WG diet (205.3 micro mol. kg(-) (1). d(-)(1)) than with the WG+Lys diet (370.7 micro mol. kg(-) (1). d(-)(1)), irrespective of the adaptation period and was similar to the ileal lysine loss with the WG diet. In the WG groups, incorporation of microbial lysine increased in the duodenum and liver (P < 0.05) but not in whole-body and muscle proteins. CONCLUSION: Minipigs fed the WG diet did not adapt by showing an enhanced absorption of microbial lysine to the extrasplanchnic tissues, presumably because microbial lysine continues to be used for splanchnic protein synthesis.