Protein quality is important for patients needing medical nutrition, especially those dependent on tube feeding. A blend of dairy and vegetable proteins (35% whey, 25% casein, 20% soy, 20% pea; P4) developed to obtain a more balanced amino acid profile with higher chemical scores, was compared to its constituent single proteins. Fourteen healthy elderly subjects received P4, whey, casein, soy, and pea (18 g/360 mL bolus) on five separate visits. Blood samples were collected at baseline until 240 min after intake. Amino acid availability was calculated using incremental maximal concentration (iC_max) and area under the curve (iAUC). Availability for P4 as a sum of all amino acids was similar to casein (iC_max and iAUC) and whey (iC_max) and higher vs. soy (iC_max and iAUC) and pea (iC_max). Individual amino acid availability (iC_max and iAUC) showed different profiles reflecting the composition of the protein sources: availability of leucine and methionine was higher for P4 vs. soy and pea; availability of arginine was higher for P4 vs. casein and whey. Conclusions: The P4 amino acid profile was reflected in post-prandial plasma levels and may be regarded as more balanced compared to the constituent single proteins.

The role of plasma glutamine, fish oil and antioxidants concentrations in the treatment effect of immune-modulating high-protein versus high-protein enteral nutrition on 6-month mortality in critically ill patients is explored, as unexpected negative outcomes of recent large randomized controlled trials on immune-modulating nutrients have raised questions about safety of these interventions. Post hoc analysis of the MetaPlus randomized controlled trial which was performed in a total of 301 medical, surgical and trauma critically ill patients in fourteen European intensive care units. Patients received either immune-modulating (glutamine, fish oil and antioxidant enriched) high-protein (IMHP) or isocaloric high-protein (HP) enteral nutrition. Six-month mortality and baseline, day 4 and day 8 plasma concentrations of glutamine, (eicosapentaenoicacid + decosahexaenoicacid)/long-chain fatty acid plasma level ratio ((epa + dha)/lcf ratio), selenium, vitamin c, vitamin e and zinc were measured. The harmful treatment effect of the IMHP versus HP enteral nutrition on 6-month mortality was only demonstrated in the medical subgroup (HR 2.52, 95% CI 1.36–4.78, P = 0.004). Among medical patients, when corrected for age groups and APACHE-II scores, there were no statistically significant associations between baseline plasma levels and 6-month mortality, except for zinc (HR 1.06, 95% CI 1.00–1.12, P = 0.026). IMHP feeding resulted in statistically significant increase in plasma levels of glutamine, vitamin e, vitamin c and (epa + dha)/lcf ratio from baseline to day 4, while only the change from baseline to day 4 of (epa + dha)/lcf ratio was statistically significant associated with 6-month mortality (HR 1.18, 95% CI 1.02–1.35, P = 0.021) and identified as mediator for the harmful treatment effect of IMHP enteral nutrition among medical ICU patients. We hypothesize that the harmful effect of IMHP compared to HP enteral nutrition in a heterogeneous group of critically ill patients is limited to the medical critically ill patients and mediated by an early increase in (epa + dha)/lcf ratio. Trial Registration Dutch Trial Register 26 January 2010 (NTR2181 http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2181 ).

P4, a specific combination of dairy proteins (whey and casein) and plant-based protein isolates (pea and soy), has been shown to provide a more balanced amino acid (AA) profile than its single constituent proteins; however, less is known about how this translates to muscle protein synthesis (MPS). The aim of this study was to investigate the effect of P4 compared to whey or casein against fasted control on MPS. C57BL/6J mice, aged 25 months, were fasted overnight, followed by oral gavage of either whey, P4, casein, or water as a fasted control. Thirty minutes after ingestion, puromycin (0.04 µmol∙g⁻¹ bodyweight) was subcutaneously injected; 30-min thereafter, mice were sacrificed. MPS was measured by the SUnSET method, and signalling proteins were determined in the left-tibialis anterior (TA) muscle by the WES technique. AA composition was determined in plasma and right-TA muscle. Dried blood spots (DBS) were analysed for postprandial AA dynamics at 10, 20, 45, 60 min. MPS was 1.6-fold increased with whey (p = 0.006) and 1.5-fold with P4 compared to fasted (p = 0.008), while no change was seen with casein. This was confirmed by a significant increase of phosphorylated/total ratio of 4E-BP1 for both whey (p = 0.012) and P4 (p = 0.001). No changes were observed in p70S6K and mTOR phosphorylation/total ratio with whey or P4. Intramuscular leucine levels were lower for P4 (0.71 µmol∙g dry weight⁻¹) compared to whey (0.97 µmol∙g dry weight⁻¹) (p = 0.0007). Ten minutes postprandial, DBS showed significantly increased blood AA levels of BCAAs, histidine, lysine, threonine, arginine, and tyrosine for P4 versus fasted. In conclusion, a hybrid mix of dairy and plant-based proteins (P4) resulted in a MPS response that was similar to whey protein in aged mice after fasting. This suggests that other anabolic triggers beyond leucine or the well-balanced amino acid profile and bioavailability of the blend benefit stimulation of MPS.

The aim of this exploratory study was to investigate gastrointestinal tolerance and protein absorption markers with a new enteral peptide formula (PF) compared to an isocaloric enteral intact protein standard formula (SF) containing the same amount of protein in ICU patients. Patients admitted to a cardio-thoracic intensive care unit expected to receive tube feeding for ≥5 days were randomized to receive either PF (1.5 kcal/mL) or SF in a double-blind manner for ≤14 days. Twenty-six patients were randomized (13 SF and 13 PF) and 23 (12 SF and 11 PF) completed at least 5 days of product administration. There were no statistically significant differences between the feeds during the first 5 days of intervention for diarrhea (SF:3 (23%); PF:5 (39%), p = 0.388), vomiting (SF:1 (8%); PF:2 (15%), p = 0.549), constipation (SF:7 (54%), PF:3 (23%), p = 0.115), and high gastric residual volume (>500 mL: SF:1 (8%); PF: 2 (15%), p = 0.535). There were no differences in plasma amino acids or urinary markers of protein absorption and metabolism. In conclusion, no major differences were found in tolerability and protein absorption markers between the standard intact protein formula and the peptide formula.