Protein absorption

Matthews, D. M.

doi:10.1136/jcp.s3-5.1.29

Cited by 75 publications

(51 citation statements)

References 55 publications

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“…Proteins are hydrolyzed by the action of secreted and membrane-bound peptidases into individual amino acids, di-and tripeptides (1). Individual amino acids are taken up by a variety of amino acid transporters, whereas diand tripeptides are absorbed by the peptide transporter PepT1 (SLC15A1) (2).…”

mentioning

confidence: 99%

Impaired Nutrient Signaling and Body Weight Control in a Na+ Neutral Amino Acid Cotransporter (Slc6a19)-deficient Mouse

Bröer

Juelich

Vanslambrouck

et al. 2011

Journal of Biological Chemistry

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Amino acid uptake in the intestine and kidney is mediated by a variety of amino acid transporters. To understand the role of epithelial neutral amino acid uptake in whole body homeostasis, we analyzed mice lacking the apical broad-spectrum neutral (0) amino acid transporter B 0 AT1 (Slc6a19). A general neutral aminoaciduria was observed similar to human Hartnup disorder which is caused by mutations in SLC6A19. Na ؉ -dependent uptake of neutral amino acids into the intestine and renal brushborder membrane vesicles was abolished. No compensatory increase of peptide transport or other neutral amino acid transporters was detected. Mice lacking B 0 AT1 showed a reduced body weight. When adapted to a standard 20% protein diet, B 0 AT1-deficient mice lost body weight rapidly on diets containing 6 or 40% protein. Secretion of insulin in response to food ingestion after fasting was blunted. In the intestine, amino acid signaling to the mammalian target of rapamycin (mTOR) pathway was reduced, whereas the GCN2/ATF4 stress response pathway was activated, indicating amino acid deprivation in epithelial cells. The results demonstrate that epithelial amino acid uptake is essential for optimal growth and body weight regulation.In a typical Western diet humans consume about 80 -100 g of protein per day. Proteins are hydrolyzed by the action of secreted and membrane-bound peptidases into individual amino acids, di-and tripeptides (1). Individual amino acids are taken up by a variety of amino acid transporters, whereas diand tripeptides are absorbed by the peptide transporter PepT1 (SLC15A1) (2). Together this digestive process makes 90 -95% of ingested proteins available to the body. Protein demand is particularly high during growth and development when new proteins are required to build up body mass. In the adult, protein recycling is quite efficient, and only 50 g of protein is needed per day to replace protein lost through urine and feces.The bulk of neutral amino acids is absorbed in the intestine by the neutral amino acid transporter B 0 AT1 (SLC6A19), which is also expressed in the kidney where it mediates reabsorption of neutral amino acids (3). Expression studies in heterologous systems have shown that B 0 AT1 accepts all neutral amino acids with a preference for large neutral amino acids such as branched-chain amino acids and methionine (4, 5). These amino acids are taken up with a K m of about 1 mM, whereas smaller amino acids are taken up with higher K m values. Glycine and proline are poor substrates of B 0 AT1. As a result additional transporters are involved in the uptake of imino acids and glycine, such as PAT1 (SLC36A1), PAT2 (SLC36A2), and IMINO (SLC6A20) (6). Additional transport systems for other neutral amino acids in the kidney and intestine have been proposed; these include a specific intestinal transporter for methionine and phenylalanine (7) and the amino acid antiporter ASCT2 (SLC1A5) as a mediator of small neutral amino acids and glutamine uptake in kidney and intestine (8).Efficient trafficking and sur...

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mentioning

confidence: 99%

Impaired Nutrient Signaling and Body Weight Control in a Na+ Neutral Amino Acid Cotransporter (Slc6a19)-deficient Mouse

Bröer

Juelich

Vanslambrouck

et al. 2011

Journal of Biological Chemistry

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“…Therefore, molecules with a similar chemical structure compete for the same carrier 26 . As a result, the absorption of some indispensable amino acids can be impaired due to the excess of dispensable amino acids, which reduces the bioavailability of indispensable amino acid 27,28 . Thus, further investigations are needed on the reduction in protein bioavailability by gelatin when it is mixed with a high-quality protein, for example, performing a fecal amino acid profile analysis.…”

Section: Discussionmentioning

confidence: 99%

Hydrolyzed collagen (gelatin) decreases food efficiency and the bioavailability of high-quality protein in rats

Bordin

Naves

2015

Rev. Nutr.

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A B S T R A C T ObjectiveAlthough deficient in all indispensable amino acids, gelatin is used in protein-restricted diets. Food efficiency and protein quality of casein and gelatin mixtures in low protein diets in Wistar rats were investigated. MethodsThe rats were treated with protein-restricted diets (10.0 and 12.5%) containing casein (control diets), casein with gelatin mixtures (4:1 of protein content), and gelatin as sources of protein. The food conversion ratio, protein efficiency ratio, relative and corrected protein efficiency ratio, true protein digestibility, and hepatic parameters were estimated. ResultsAfter 28 days of the experiment, food efficiency of 10.0% casein/gelatin diet decreased when compared to that of 10.0% casein diet, and the protein efficiency ratio of the casein/gelatin mixtures (10.0%=2.41 and 12.5%=2.03) were lower than those of the casein (10.0%=2.90 and 12.5%=2.32). After 42 days of the experiment, the weight of the liver of the animals treated with 10.0 and 12.5% casein/gelatin diets, and the liver protein retention of the 12.5% casein/gelatin diet group of animals were lower than those of the control group. ConclusionGelatin decreases food efficiency and high-quality protein bioavailability in protein-restricted diets.Keywords: Amino acids. Biological availability. Caseins. Gelatin. Proteins. Rats. I N T R O D U C T I O NGelatin is a soluble mixture of polypeptides produced by the partial hydrolysis of collagen 1 .Collagen is an insoluble protein of animal origin that holds organs and tissues together and gives strength to tendons, among other biological functions 2,3 . In nutritional terms, gelatin is an incomplete protein because its amino acid profile is quite atypical and deficient in all of the indispensable (essential) amino acids recommended by the Food and Nutrition Board of the Institute of Medicine (IOM) of the National Academy of Sciences 4 . It is known that gelatin contains no tryptophan 5,6 .Gelatin and collagen hydrolysate have been shown to improve skin hydration, transepidermal water loss, elasticity, and skin barrier dysfunction 7,8 . Furthermore, they have been used to promote weight loss because studies have shown that gelatin can inhibit appetite and promote satiety 9,10 . However, the use of gelatin in a protein-restricted diets (like those before and after gastrointestinal tract surgery, chronic renal insufficiency treatment diets, and those aimed to promote weight loss 11,12 ) could be a potential nutritional risk. Insufficient protein intake (in terms of both quantity and quality) inhibits endogenous metabolism of proteins, prolongs the inflammatory phase of the healing process, decreases fibroblast proliferation, angiogenesis and collagen synthesis, and impairs tissue repair 12 . Therefore, the use of gelatin in a protein-deficient diet could slow patient recovery.Considering the uses of gelatin in proteinrestricted diets, this study investigated food efficiency and protein quality of casein (a complete protein) and gelatin mixtures in low protein diet...

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“…Some oligopeptides can be absorbed into the epithelial cell intact, hydrolysis occurring at the brush border or in the cytosol, with small amounts of oligopeptides passing through to the blood (Matthews & Adibi, 1976). The osmoreceptors lie deep to the brush border because, gram for gram, maltose is almost as effective as glucose (Elias, Gibson, Greenwood, Hunt & Tripp, 1968).…”

Section: Gastric Emptying Of Proteinsmentioning

confidence: 99%

“…However, the evidence is against oligopeptides exerting an osmotic effect from within the cell. Diglycine, believed to be absorbed as such (Matthews & Adibi, 1976) (Mallinson, 1968;Knox & Mallinson, 1971 …”

Section: Gastric Emptying Of Proteinsmentioning

confidence: 99%

The slowing of gastric emptying by proteins in test meals.

Burn-Murdoch¹,

Fisher²,

Hunt³

1978

The Journal of Physiology

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SUMMARY1. Test solutions containing either glucose, casein, partially hydrolysed gelatin or egg albumin, native or denatured, at concentrations up to 50 g/l. in 33 mm-trisodium citrate solution, were given by tube into the stomachs of nine subjects in volumes of 600 or 750 ml.2. The volume of the test solution recovered from the stomach after 20 min was measured.3. The greater the concentration of solute the greater was the volume of the test solution recovered.4. Gram for gram, gelatin hydrolysate was equivalent to glucose in slowing gastric emptying. Casein was slightly more effective than glucose and native egg albumin was less effective than glucose.5. The results were explained by assuming that the products of hydrolysis of proteins stimulated osmoreceptors in the walls of the duodenum.6. The results were in line with the suggestion that proteins in food contribute to the slowing of gastric emptying in such a way that isocaloric amounts of carbohydrate and mixed protein have the same effect.7. There was a strong correlation between the concentration of glucose giving a recovery of 400 ml. and the corresponding concentration of casein within-subject, but there was no such relationship for gelatin hydrolysate. It was concluded that the between-subject variability in the digestion of casein was small, that for gelatin hydrolysate was large.

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Protein absorption

Cited by 75 publications

References 55 publications

Impaired Nutrient Signaling and Body Weight Control in a Na+ Neutral Amino Acid Cotransporter (Slc6a19)-deficient Mouse

Impaired Nutrient Signaling and Body Weight Control in a Na+ Neutral Amino Acid Cotransporter (Slc6a19)-deficient Mouse

Hydrolyzed collagen (gelatin) decreases food efficiency and the bioavailability of high-quality protein in rats

The slowing of gastric emptying by proteins in test meals.

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