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Effect of Age on Blood Glucose and Plasma Insulin, Glucagon, Ghrelin, CCK, GIP, and GLP-1 Responses to Whey Protein Ingestion

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      Protein-rich supplements are used widely to prevent and manage undernutrition in older people. We have previously shown that healthy older, compared to younger, adults have less suppression of energy intake by whey protein—although the effects of age on appetite-related gut hormones are largely unknown. The aim of this study was to determine and compare the acute effects of whey protein loads on blood glucose and plasma gut hormone concentrations in older and younger adults. Sixteen healthy older (eight men, eight women; mean ± SEM: age: 72 ± 1 years; body mass index: 25 ± 1 kg/m2) and 16 younger (eight men, eight women; 24 ± 1 years; 23 ± 0.4 kg/m2) adults were studied on three occasions in which they ingested 30 g (120 kcal) or 70 g (280 kcal) whey protein, or a flavored-water control drink (~2 kcal). At regular intervals over 180 min, blood glucose and plasma insulin, glucagon, ghrelin, cholecystokinin (CCK), gastric inhibitory peptide (GIP), and glucagon-like peptide-1 (GLP-1) concentrations were measured. Plasma ghrelin was dose-dependently suppressed and insulin, glucagon, CCK, GIP, and GLP-1 concentrations were dose-dependently increased by the whey protein ingestion, while blood glucose concentrations were comparable during all study days. The stimulation of plasma CCK and GIP concentrations was greater in older than younger adults. In conclusion, orally ingested whey protein resulted in load-dependent gut hormone responses, which were greater for plasma CCK and GIP in older compared to younger adults.

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      Most cited references 29

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      Inhibition of gastric inhibitory polypeptide signaling prevents obesity.

      Secretion of gastric inhibitory polypeptide (GIP), a duodenal hormone, is primarily induced by absorption of ingested fat. Here we describe a novel pathway of obesity promotion via GIP. Wild-type mice fed a high-fat diet exhibited both hypersecretion of GIP and extreme visceral and subcutaneous fat deposition with insulin resistance. In contrast, mice lacking the GIP receptor (Gipr(-/-)) fed a high-fat diet were clearly protected from both the obesity and the insulin resistance. Moreover, double-homozygous mice (Gipr(-/-), Lep(ob)/Lep(ob)) generated by crossbreeding Gipr(-/-) and obese ob/ob (Lep(ob)/Lep(ob)) mice gained less weight and had lower adiposity than Lep(ob)/Lep(ob) mice. The Gipr(-/-) mice had a lower respiratory quotient and used fat as the preferred energy substrate, and were thus resistant to obesity. Therefore, GIP directly links overnutrition to obesity and it is a potential target for anti-obesity drugs.
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        Gut hormones and appetite control.

        Many peptides are synthesized and released from the gastrointestinal tract. Although their roles in the regulation of gastrointestinal function have been known for some time, it is now evident that they also physiologically influence eating behavior. Our understanding of how neurohormonal gut-brain signaling regulates energy homeostasis has advanced significantly in recent years. Ghrelin is an orexigenic peptide produced by the stomach, which appears to act as a meal initiator. Satiety signals derived from the intestine and pancreas include peptide YY, pancreatic polypeptide, glucagon-like peptide 1, oxyntomodulin, and cholecystokinin. Recent research suggests that gut hormones can be manipulated to regulate energy balance in humans, and that obese subjects retain sensitivity to the actions of gut hormones. Gut hormone-based therapies may thus provide an effective and well-tolerated treatment for obesity.
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          Gender differences in food intake and selection first appear in adolescence. Men consume more calories than women, and the sexes have different eating styles, which indicate that women have been socialized to eat in a more feminine manner. Women experience more food-related conflict than men do, in that they like fattening foods but perceive that they should not eat them. Pressures to be thin are present in early adolescence, as noted by dieting behavior starting in very young girls. Women experience more dissatisfaction with their body weight and shape than men do. Sociocultural and psychological factors may be important in the etiology of eating disorders, which are much more prevalent in females than in males. Thus, further studies of gender differences in eating behavior will be important for understanding the etiology of eating and body-weight disorders and for designing gender-appropriate treatments.

            Author and article information

            [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, 5000 Adelaide, Australia; caroline.giezenaar@ (C.G.); amy.hutchsison@ (A.T.H.); natalie.luscombe-marsh@ (N.D.L.-M.); ian.chapman@ (I.C.); michael.horowitz@ (M.H.)
            [2 ]Commonwealth Scientific and Industrial Research Organisation (CSIRO), Food and Nutrition, 5000 Adelaide, Australia
            Author notes
            [* ]Correspondence: stijn.soenen@ ; Tel.: +61-8-8313-3638
            21 December 2017
            January 2018
            : 10
            : 1
            © 2017 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 (


            Nutrition & Dietetics

            age-effect, whey protein, gut hormones


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