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      Dose-Dependent Effects of Randomized Intraduodenal Whey-Protein Loads on Glucose, Gut Hormone, and Amino Acid Concentrations in Healthy Older and Younger Men

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          Abstract

          Protein-rich supplements are used widely for the prevention and management of malnutrition in older people. We have reported that healthy older, compared to younger, adults have less suppression of energy intake by whey-protein—effects on appetite-related hormones are unknown. The objective was to determine the effects of intraduodenally administered whey-protein on glucose, gut hormone, and amino acid concentrations, and their relation to subsequent ad libitum energy intake at a buffet meal, in healthy older and younger men. Hydrolyzed whey-protein (30 kcal, 90 kcal, and 180 kcal) and a saline control (~0 kcal) were infused intraduodenally for 60 min in 10 younger (19–29 years, 73 ± 2 kg, 22 ± 1 kg/m 2) and 10 older (68–81 years, 79 ± 2 kg, 26 ± 1 kg/m 2) healthy men in a randomized, double-blind fashion. Plasma insulin, glucagon, gastric inhibitory peptide (GIP), glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY), and amino acid concentrations, but not blood glucose, increased, while ghrelin decreased during the whey-protein infusions. Plasma GIP concentrations were greater in older than younger men. Energy intake correlated positively with plasma ghrelin and negatively with insulin, glucagon, GIP, GLP-1, PYY, and amino acids concentrations ( p < 0.05). In conclusion, intraduodenal whey-protein infusions resulted in increased GIP and comparable ghrelin, insulin, glucagon, GIP, GLP-1, PYY, and amino acid responses in healthy older and younger men, which correlated to subsequent energy intake.

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          Amino acid ingestion improves muscle protein synthesis in the young and elderly.

          We recently demonstrated that muscle protein synthesis was stimulated to a similar extent in young and elderly subjects during a 3-h amino acid infusion. We sought to determine if a more practical bolus oral ingestion would also produce a similar response in young (34 +/- 4 yr) and elderly (67 +/- 2 yr) individuals. Arteriovenous blood samples and muscle biopsies were obtained during a primed (2.0 micromol/kg) constant infusion (0.05 micromol.kg(-1).min(-1)) of L-[ring-2H5]phenylalanine. Muscle protein kinetics and mixed muscle fractional synthetic rate (FSR) were calculated before and after the bolus ingestion of 15 g of essential amino acids (EAA) in young (n = 6) and elderly (n = 7) subjects. After EAA ingestion, the rate of increase in femoral artery phenylalanine concentration was slower in elderly subjects but remained elevated for a longer period. EAA ingestion increased FSR in both age groups by approximately 0.04%/h (P < 0.05). However, muscle intracellular (IC) phenylalanine concentration remained significantly higher in elderly subjects at the completion of the study (young: 115.6 +/- 5.4 nmol/ml; elderly: 150.2 +/- 19.4 nmol/ml). Correction for the free phenylalanine retained in the muscle IC pool resulted in similar net phenylalanine uptake values in the young and elderly. EAA ingestion increased plasma insulin levels in young (6.1 +/- 1.2 to 21.3 +/- 3.1 microIU/ml) but not in elderly subjects (3.0 +/- 0.6 to 4.3 +/- 0.4 microIU/ml). Despite differences in the time course of plasma phenylalanine kinetics and a greater residual IC phenylalanine concentration, amino acid supplementation acutely stimulated muscle protein synthesis in both young and elderly individuals.
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            Protein and energy supplementation in elderly people at risk from malnutrition.

            Evidence for the effectiveness of nutritional supplements containing protein and energy, often prescribed for older people, is limited. Malnutrition is more common in this age group and deterioration of nutritional status can occur during illness. It is important to establish whether supplementing the diet is an effective way of improving outcomes for older people at risk from malnutrition. This review examined trials for improvement in nutritional status and clinical outcomes when extra protein and energy were provided, usually as commercial 'sip-feeds'. We searched The Cochrane Library, MEDLINE, EMBASE, Healthstar, CINAHL, BIOSIS, CAB abstracts. We also hand searched nutrition journals and reference lists and contacted 'sip-feed' manufacturers. Randomised and quasi-randomised controlled trials of oral protein and energy supplementation in older people, with the exception of groups recovering from cancer treatment or in critical care. Two reviewers independently assessed trials prior to inclusion and independently extracted data and assessed trial quality. Authors of trials were contacted for further information as necessary. Sixty-two trials with 10,187 randomised participants have been included in the review. Maximum duration of intervention was 18 months. Most included trials had poor study quality. The pooled weighted mean difference (WMD) for percentage weight change showed a benefit of supplementation of 2.2% (95% confidence interval (CI) 1.8 to 2.5) from 42 trials. There was no significant reduction in mortality in the supplemented compared with control groups (relative risk (RR) 0.92, CI 0.81 to 1.04) from 42 trials. Mortality results were statistically significant when limited to trials in which participants (N = 2461) were defined as undernourished (RR 0.79, 95% CI 0.64 to 0.97).The risk of complications was reduced in 24 trials (RR 0.86, 95% CI 0.75 to 0.99). Few trials were able to suggest any functional benefit from supplementation. The WMD for length of stay from 12 trials also showed no statistically significant effect (-0.8 days, 95% CI -2.8 to 1.3). Adverse effects included nausea or diarrhoea. Supplementation produces a small but consistent weight gain in older people. Mortality may be reduced in older people who are undernourished. There may also be a beneficial effect on complications which needs to be confirmed. However, this updated review found no evidence of improvement in functional benefit or reduction in length of hospital stay with supplements. Additional data from large-scale multi-centre trials are still required.
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              Effectiveness of nutritional supplementation on muscle mass in treatment of sarcopenia in old age: a systematic review.

              Much interest has been focused on nutritional treatment of sarcopenia, loss of muscle mass and performance associated to aging; however, its benefits are unclear. To analyze the relevance of nutritional treatment of sarcopenia and assess the effects of supplementation on muscle mass and function within the aged population. We searched Medline and the Cochrane Library for controlled trials published between 1991 and 2012. We have assessed the quality, type of intervention, the cohort used, the way muscle mass was measured, and the outcomes of the various studies. We have included 17 studies, with a total of 1287 patients, aged between 65 and 85 on average. An improvement in muscle mass was proven, whether measured with bioelectrical impedance analysis or dual energy x-ray absorptiometry, and an improvement in strength was also proven. Nutritional supplementation is effective in the treatment of sarcopenia in old age, and its positive effects increase when associated with physical exercise. The main limitation of this treatment is lack of long-term adherence. A healthy diet associated with a physically active lifestyle and possibly with aerobic exercise are the basis of healthy aging, which is the aim of all doctors treating aged people must seek. Copyright © 2013 American Medical Directors Association, Inc. Published by Elsevier Inc. All rights reserved.
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                Author and article information

                Journal
                Nutrients
                Nutrients
                nutrients
                Nutrients
                MDPI
                2072-6643
                12 January 2018
                January 2018
                : 10
                : 1
                : 78
                Affiliations
                [1 ]Discipline of Medicine and National Health and Medical Research Council of Australia (NHMRC) Centre of Research Excellence in Translating Nutritional Science to Good Health, Adelaide Medical School, Adelaide 5000, Australia; caroline.giezenaar@ 123456adelaide.edu.au (C.G.); natalie.luscombe-marsh@ 123456csiro.au (N.D.L.-M.); amy.hutchsison@ 123456adelaide.edu.au (A.T.H.); scott.standfield@ 123456adelaide.edu.au (S.S.); christine.feinle@ 123456adelaide.edu.au (C.F.-B.); michael.horowitz@ 123456adelaide.edu.au (M.H.); ian.chapman@ 123456adelaide.edu.au (I.C.)
                [2 ]Commonwealth Scientific and Industrial Research Organisation (CSIRO), Food and Nutrition, Adelaide 5000, Australia
                Author notes
                [* ]Correspondence: stijn.soenen@ 123456adelaide.edu.au ; Tel.: +61-8-8313-3638
                Author information
                https://orcid.org/0000-0001-5612-1918
                https://orcid.org/0000-0002-6393-3671
                Article
                nutrients-10-00078
                10.3390/nu10010078
                5793306
                29329233
                7b0c1d25-9250-485f-93da-1d6e36704cfa
                © 2018 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 02 November 2017
                : 09 January 2018
                Categories
                Article

                Nutrition & Dietetics
                ageing,whey protein,gut hormones
                Nutrition & Dietetics
                ageing, whey protein, gut hormones

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