Aminoacidemia following ingestion of native whey protein, micellar casein, and a whey-casein blend in young men.

We examined the aminoacidemic, glycemic, and insulinemic responses following ingestion of 25 g of native whey protein, micellar casein, and a 1:1 blend of whey and casein in randomized order in young adult men. Blood samples were drawn at baseline and at regular intervals for 6 h following ingestion. Area under curve and peak plasma essential amino acid concentrations after the ingestion of the protein blend were similar to whey and greater compared with casein.

Impact of human milk pasteurization on gastric digestion in preterm infants: a randomized controlled trial.

BACKGROUND: Holder pasteurization has been reported to modify human milk composition and structure by inactivating bile salt-stimulated lipase (BSSL) and partially denaturing some of its proteins, potentially affecting its subsequent digestion. OBJECTIVE: We sought to determine the impact of human milk pasteurization on gastric digestion (particularly for proteins and lipids) in preterm infants who were fed their mothers' own milk either raw or pasteurized. DESIGN: In a randomized controlled trial, 12 hospitalized tube-fed preterm infants were their own control group in comparing the gastric digestion of raw human milk (RHM) with pasteurized human milk (PHM). Over a 6-d sequence, gastric aspirates were collected 2 times/d before and after RHM or PHM ingestion. The impact of milk pasteurization digestive kinetics and disintegration was tested with the use of a general linear mixed model. RESULTS: Despite inactivating BSSL, instantaneous lipolysis was not affected by pasteurization (mean ± SD at 90 min: 12.6% ± 4.7%; P > 0.05). Lipolysis occurred in milk before digestion and was higher for PHM than for RHM (mean ± SD: 3.2% ± 0.6% and 2.2% ± 0.8%, respectively; P < 0.001). Pasteurization enhanced the proteolysis of lactoferrin (P < 0.01) and reduced that of α-lactalbumin (only at 90 min) (P < 0.05). Strong emulsion destabilization was observed, with smaller aggregates and a higher specific surface for PHM (P < 0.05). Pasteurization did not affect gastric emptying (∼30-min half time) or pH (mean ± SD: 4.4 ± 0.8) at 90 min. CONCLUSIONS: Overall, pasteurization had no impact on the gastric digestion of lipids and some proteins from human milk but did affect lactoferrin and α-lactalbumin proteolysis and emulsion disintegration. Freeze-thawing and pasteurization increased the milk lipolysis before digestion but did not affect gastric lipolysis. Possible consequences on intestinal digestion and associated nutritional outcomes were not considered in this study. This trial was registered at clinicaltrials.gov as NCT02112331.

The safety of oral use of L-glutamine in middle-aged and elderly individuals.

OBJECTIVE: To evaluate the safety of nutraceutical oral administration of L-glutamine (L-Gln) in middle-aged and elderly individuals. METHODS: In this randomized, crossover, double-blind clinical study, 30 residents of a long-term-care institution, selected according to a modified SENIEUR protocol (Working Party of the EURAGE Concerted Action Programme on Ageing of the European Community), were studied. Fourteen subjects received orally 0.5 g kg(-1) d(-1) of L-Gln and 16 received calcium caseinate for 14 d, followed by a 5-d washout. Supplements were switched for the second 14-d trial. Laboratory tests for hepatic and renal functions and ammonemia were performed and the estimated glomerular filtration rate (eGFR) was calculated. RESULTS: Of the 30 subjects, 16 were men, mean age was 69+/-8.8 y, average weight was 61.8+/-14.2 kg, and mean serum albumin was 4.0+/-0.3g/dL. Neither adverse clinical effects nor clinically significant laboratory changes were noted during L-Gln supplementation. There was no difference in ammonemia between the groups. There were statistically but not clinically significant increases in plasma urea nitrogen and creatinine concentrations. There was no significant decrease in eGFR during calcium caseinate supplementation (-2.9%). The eGFR decreased significantly after L-Gln supplementation (-13.3%) but well below the 25% limit for biologic significance. CONCLUSION: Increases in serum urea nitrogen and creatinine and decrease in eGFR are probably due to difficulties by older kidneys in metabolizing the supplemented protein sources. Although not clinically significant, those alterations impose a rigorous control on the evaluation parameters of renal function during oral L-Gln supplementation, with doses of 0.5 g kg(-1) d(-1) in middle-aged and elderly individuals.

Early serum IGF-I response to oral protein supplements in elderly women with a recent hip fracture.

BACKGROUND & AIMS: In patients with recent hip fracture, reduced serum IGF-I in relation to protein undernutrition is frequent. Elevation of circulating IGF-I in response to a daily oral supplement of 20 g of casein was observed after 6 months. This study determined if the response to casein as compared to whey protein can be observed as early as after one week. METHODS: 45 women were randomized after recent hip fracture in 3 groups receiving a preparation of 20 g of casein, an isocaloric supplement of 20 g of whey protein or an isocaloric supplement of 15 g of whey protein combined with 5 g of essential amino acids (a.a.). RESULTS: A similar significant elevation of serum IGF-I was already observed after 7 days for casein (+37.3 microg/L), whey (+29.4) and for whey+a.a. (+34.3). From day 7-28, no further significant rise in IGF-I was recorded. CONCLUSION: After one week of protein supplementation, the percent increase of IGF-I was of similar magnitude to that previously observed after 6 months of protein supplementation. It suggests that in hip fracture patients, long-term effects of various protein preparations on IGF-I could be predicted from changes observed as early as 7 days after the onset of supplementation.

Changes in serum lipoprotein lipids and their fatty acid compositions and lipid peroxidation in growing rats fed soybean protein versus casein with or without cholesterol.

OBJECTIVE: We compared the effects of diets based on soybean protein and casein supplemented or not supplemented with 0.1% cholesterol on plasma lipoprotein lipid amounts and their fatty acid compositions, lecithin:cholesterol acyl-transferase activity, and lipid peroxidation. METHODS: The composition and concentration of lipid and apolipoprotein in different lipoprotein classes, plasma LCAT activity, and lipid peroxidation were determined in rats fed 20% highly purified soybean protein or casein with or without 0.1% cholesterol for 2 mo. RESULTS: Soybean protein and casein diets with or without cholesterol had similar plasma total cholesterol concentrations. Soybean protein consumption diminished very low-density lipoprotein particle number, as measured by diminished contents of very low-density lipoprotein triacylglycerol, phospholipid, and apolipoprotein-B100. Lecithin:cholesterol acyl-transferase activity was not significantly modified by either protein. The soybean protein diet decreased the linoleate desaturation index (20:4[omega-6]/18:2[omega-6]) in liver and high-density lipoprotein fraction 2-3-phospholipids but enhanced red blood cell resistance against free radical attack. Addition of cholesterol to both protein diets decreased concentrations of high-density lipoprotein fraction 2-3 cholesterol. Lecithin:cholesterol acyl-transferase activity tended to be greater after cholesterol feeding, likely due to the enhanced high-density lipoprotein fraction 2-3 apolipoprotein-AI, a cofactor activator for lecithin:cholesterol acyl-transferase. Regardless of dietary protein source, cholesterol supplementation decreased the linoleate desaturation index in liver and plasma lipoprotein lipids and red blood cell resistance to free radical attack. CONCLUSIONS: Our results suggest that the dietary protein origin affects lipid peroxidation and polyunsaturated fatty acid biosynthesis and distribution among liver and different lipoprotein lipid classes, but plays only a minor role in the regulation of plasma and lipoprotein cholesterol concentrations. Providing dietary cholesterol (0.1%) with casein or soybean protein attenuates the effects of these proteins, with the exception of plasma cholesterol.

Comparative study of glycine, alanine or casein as inert nitrogen sources in endotoxemic rats.

Pharmacological effects of dietary amino acids (AA) and peptides must be compared to an isonitrogenous control that is as inert as possible. To establish a rationale for the choice of such a control, potential metabolic and nutritional effects of three currently used nitrogenous controls (glycine, alanine, and casein) were evaluated in an endotoxemic rat model that has well-defined alterations in AA and protein metabolism. Five-week-old male Sprague-Dawley rats (113 +/- 1 g) were randomly assigned to four groups and received at d 0 an intraperitoneal injection of endotoxin (3 mg/kg). After withdrawal of food for 24 h, the rats were enterally refed for 48 h with a liquid diet (Osmolite((R))) supplemented with 0.19 g N. kg(-1). d(-1) in the form of glycine [lipopolysaccharide (LPS)-GLY group], alanine (LPS-ALA group) or casein (LPS-CAS group). One group (LPS group) received only Osmolite((R)). Plasma, two skeletal muscles, the liver and the intestine were then removed. Body and tissue weights and tissue protein contents did not differ among the four groups. Intestine histomorphometry showed no significant difference among groups. Jejunal hydrolase activities were significantly affected by the nitrogenous supplementations, but no effect was observed in the ileum. Only limited significant effects were observed on plasma and tissue-free AA concentrations, except for an accumulation of glycine in the plasma and tissues from the LPS-GLY group, compared to other groups. Overall, whereas glycine as a nitrogenous control should be used with care, either alanine or casein may be used as the "placebo," with the choice depending on the study to be performed.

Enzyme-linked immunosorbent assay of colostral IgG transported into lymph and plasma in neonatal pigs.

Amounts of colostral proteins in lymph and plasma were estimated by an enzyme-linked immunosorbent assay (ELISA) after infusion of bovine colostrum into the duodenal lumen in nonsuckling neonatal pigs. The rate of immunoglobulin (Ig) G transport in lymph of the thoracic duct reached the maximal level (4.7 +/- 1.3 mg.15 min-1.kg body wt-1) within 3 h after the duodenal infusion. The rate of small protein (SP) transport more slowly increased than that of IgG. On the contrary, casein remained in the much lower level in lymph. IgG concentration in plasma increased gradually and reached a plateau level (2.5 +/- 0.9 g/l) 5 h after the infusion, but the levels of SP and casein were slowly and slightly increased in plasma. The IgG-to-casein and SP-to-casein ratios in lymph and plasma were 161:15:1 and 128:12:1 4 h after the infusion, respectively, and much higher than the value in the colostrum (IgG/SP/casein = 15:4:1). These results indicate 1) that IgG transported via lymph flow after absorption through the small intestine is faster than that via blood flow, 2) that the concentration of absorbed IgG is higher than that of absorbed SP and much higher than the concentration of absorbed casein both in the lymph and plasma, and 3) that total amount of colostral protein transported via blood flow is larger than that transported via lymph flow.

Toxicological evaluation of rapeseed products in a subacute feeding study in rats.

Groups of 15 male rats were fed ad libitum for 4 weeks standard diet containing 0, 2.5, 5 or 10% rapeseed protein isolate (RPI), 2.5, 5 or 10% rapeseed extraction residue (RER) or 10% casein. Body weight gain and food intake were recorded weekly. Clinical chemistry analyses, haematology, urinalysis, organ weights and histology were performed terminally. Serum alanine aminotransferase was decreased by RPI, RER and casein, while serum albumin only increased in rats fed RER. Microscopic examinations revealed abnormalities in liver and kidneys of animals at the 10% RPI, RER and casein levels. The absolute liver weights showed increases in the 5 and 10% RER groups and in the 10% RPI group. The relative kidney weights were reduced at all RER levels and in the 2.5% RPI group. Antithyroid activity of the rapeseed products were not noted.