Effect of age on arterial plasma amino acid concentrations at the fed state.

<p>Values are expressed as means ± SEM.</p><p>*<i>P</i><0.05 <i>vs</i>. and</p>+<p><i>P</i><0.01 <i>vs</i>. adult rats (Student's <i>t</i>-test). BCAA = branched-chain amino acids; TAA = total amino acids.</p

Effect of age on body composition.

<p>Values are expressed as means ± SEM.</p><p>*<i>P</i><0.05 and</p>+<p><i>P</i><0.01 <i>vs</i>. adult rats (Student's <i>t</i>-test).</p><p>BW: total body weight.</p

Effect of aging on whole-body protein kinetics at the fed state.

<p>□ adult rats and ▪ old rats. Values are expressed as means ± SEM. <i>P</i><0.05 <i>vs</i>. adult group (Student's <i>t</i>-test). CW = carcass weight. WbPS = whole-body protein synthesis; WbPB = whole-body protein breakdown.</p

Amino acid composition of the mixture infused into the rat duodenum.

<p>Amino acid composition of the mixture infused into the rat duodenum.</p

Tracer prime and infusion rates.

<p>With i.v. = intravenous.</p

Effect of aging on organ protein kinetics at the fed state.

<p>Values are expressed as means ± SEM. Groups were compared via a Student's <i>t</i>-test. Phe disposal and production in hindquarters and in portal-drained viscera reflects protein synthesis and breakdown in muscle and in gut, respectively. In the liver, Leu disposal and production were used to assess hepatic protein synthesis and breakdown. Cw = carcass weight.</p

Effect of aging on urea production and hepatic metabolism of major substrates of ureagenesis, i.e. arginine and alanine.

<p>CW = carcass weight. □ adult rats and ▪ old rats. Values are expressed as means ± SEM. * <i>P</i><0.05 <i>vs</i>. adult group (Student's <i>t</i>-test).</p

Organ Total Net balances of XPP peptides.

<p>Study 1. Post-prandial total net balances across organs over 90 min experimental period after <i>intra-gastric</i> administration of tri-peptide (XPP) mixtures: a synthetic dose of XPP (XPP), XPP containing casein hydrolyte (CasH) and spiked CasH (CasH + XPP). Organs: portal drained viscera (PDV), Liver, Splanchnic area (SPL), Kidneys. Positive balance is net release by an organ. Negative balance is net uptake by an organ. Values are mean ± SEM. Statistics: unpaired t-test for comparison of net balances of natural occurring XPP vs administrated XPP (Control vs XPP), water-based vs protein matrix (XPP vs CasH), and for comparison protein matrixes with vs without XPP spike (CasH vs CasH+XPP). Hooks: significance p<0.05. dotted hooks: tendency p<0.10.</p

Portal Drained Viscera fluxes of XPP—Effect of a protein matrix.

<p>Post-prandial portal drained viscera (PDV) fluxes after <i>intra-gastric</i> administration of tri-peptide (XPP) mixtures: control salt solution (Control), synthetic XPP’s (XPP), casein hydrolyte rich in XPP (CasH) or spiked CasH (CasH + XPP). A: Isoleucine-proline-proline (IPP). B: Leucine-proline-proline (LPP). C: Valine-proline-proline (VPP). Respective number of observations for Control, XPP, CasH and CasH +XPP are for graph A: n = 6, 9, 8 and 9; graph B: n = 6, 10, 9 and 9; graph C: n = 5, 9, 9 and 9. Values are mean ± SEM. Positive values is net release, negative values is net uptake. Statistics: repeated measures two-way ANOVA, mixed model, planned comparisons. All curves are significantly different from the XPP mixture: effect test mixture p<0.01; effect time p<0.01; interaction p<0.01</p

Composition of test mixtures—Study 1.

<p>¹⁾ Chemical purities of the IPP, LPP, and VPP synthetic products were 93.4, 95.0 and 98.7%, respectively (Bachem, Weil am Rhein, Switzerland).</p><p>²⁾ The given amounts of tri-peptides isoleucine-proline-proline (IPP), leucine-proline-proline (LPP), valine-proline-proline (VPP) in the casein hydrolysate (CasH, Casimax, DSM Food Specialties, Delft, The Netherlands). The casein hydrolysate contained 57% protein with 5.4, 16.5 and 0.3 mg/g protein of LPP, LPP and VPP, respectively.</p><p>³⁾ Total XPP = total amount of IPP, LPP and VPP.</p><p>Composition of test mixtures—Study 1.</p