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General Peptide Use & Information
Thoughts on GHK-cu capsules?
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<blockquote data-quote="BadassBlues" data-source="post: 271242" data-attributes="member: 38526"><p>There have been studies done on the intestinal absorption of small peptides. It appears that they are easily absorbed, and that absorption can be enhanced by dietary factors.</p><p></p><p>[URL unfurl="true"]https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048[/URL]</p><p></p><h2><em>Summary</em></h2><p><em></em></p><p><em>Peptides display diverse structural features because of their varied amino acid compositions. The structural diversity often imparts them complex physiological functions, or possible health-beneficial effects. Some small peptides (di-/tripeptides) exert preventive effects against conditions such as hypertension, hypercholesterolaemia and atherosclerosis. Despite their health benefits, a limited understanding of peptide absorption may hinder their extensive application. Therefore, this review briefly introduces the in vitro and in vivo findings on the intestinal absorption of small peptides and potential factors affecting their absorption.</em></p><p><em></em></p><h2><em>Factors affecting the absorption of small peptides</em></h2><p><em>Current studies on the absorption of peptides are mainly conducted by a single oral administration of target peptides. However, as a food material, it is possible that co-existing compounds present in a food matrix could affect the absorption of peptides. For instance, although PepT1 exhibits a certain level of transport capacity and dose dependency (Jappar et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0016" target="_blank">2011</a>), the absorption of targeted small peptides could be competitively restricted when co-existing compounds share the same PepT1 transport pathway. In previous studies, we demonstrated that the transport of dipeptides Val-Tyr (Hong et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0012" target="_blank">2013</a>) and Trp-His (Tanaka et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0039" target="_blank">2015</a>) was inhibited by the existence of a PepT1 substrate Gly-Sar, using an ex vivo chamber transport experiment. Also, the blood concentration of a PepT1-transported dipeptidyl drug, captopril significantly decreased when administered simultaneously with a dipeptide Val-Tyr (Matsui et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0024" target="_blank">2006</a>). In such cases, the transport of dipeptide(s) mainly depends on the affinity (Km) to PepT1. On the contrary, some food compounds could alter the absorption of dipeptides by adjusting the expression of PepT1. <strong>It has been reported that dietary amino acids and protein (hydrolysates) could up-regulate the expression of intestinal PepT1 mRNA to increase the intestinal transporter capacity of PepT1 and facilitate the absorption of peptides </strong>(Shiraga et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0032" target="_blank">1999</a>; Osmanyan et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0031" target="_blank">2018</a>). Meanwhile, theaflavins, polymeric catechins, have been reported to down-regulate the expression of PepT1 via the activation of intracellular AMP-dependent kinase, thus restricting the transport of dipeptides (Takeda et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0035" target="_blank">2013</a>). In addition, Wenzel et al. (<a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0041" target="_blank">2001</a>) examined thirty-three food derived flavonoids and reported that quercetin, genistein, naringin, diosmin, acacetin and chrysin had the potential to increase the absorption of PepT1-transported compounds by activation of apical Na+/H+-exchanger to maintain the proton gradient which serves as a driving force for PepT1-mediated transport. Similarly, because a proton is released when a non-charged fatty acid enters the cytosol, <strong>dietary fatty acids could also facilitate the absorption of dipeptides by maintaining the transmembrane proton flux </strong>(Spanier et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0034" target="_blank">2009</a>; Fig. <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-fig-0003" target="_blank">3</a>). With regards to other macronutrients, carbohydrates have been reported to stimulate intestinal tissue anabolism, thus incorporating more peptides into the intestinal cells than released into blood circulation. In contrast, addition of fibre increased the systemic availability of di-/tripeptides (Ten Have et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0040" target="_blank">2015</a>). However, information is still limited on the effects of respective macronutrients on the absorption of small peptides.</em></p><p><em></em></p><p><em><a href="https://ifst.onlinelibrary.wiley.com/cms/asset/3577b5a0-b241-4d76-8cbe-280f6a3c4545/ijfs14048-fig-0003-m.jpg" target="_blank">[IMG alt="Details are in the caption following the image"]https://ifst.onlinelibrary.wiley.com/cms/asset/28628ce8-492e-4ee1-8723-9c834c9c2286/ijfs14048-fig-0003-m.png[/IMG]</a></em></p><p><em><strong>Figure 3</strong></em></p><p><em><a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#" target="_blank">Open in figure viewer</a><a href="https://ifst.onlinelibrary.wiley.com/action/downloadFigures?id=ijfs14048-fig-0003&doi=10.1111%2Fijfs.14048" target="_blank">PowerPoint</a></em></p><p><em>Factors affecting the absorption of small peptides. Food and non-food factors could affect the absorption of small peptides potentially via (1) competitive inhibition of PepT1, (2) transcriptional regulation of PepT1 and (3) maintenance of the proton gradient (a driving force for PepT1-mediated transport).</em></p><p><em>Besides food factors, the absorption of small peptides could also be affected by other factors such as health of the individual. In a recent study, we reported enhanced absorption of dipeptides Gly-Sar and Trp-His in 40-week-old spontaneously hypertensive rats (SHRs) and compared them to 8-week young SHRs. We discovered that the expression of intestinal PepT1 was significantly (~1.5-fold) higher in the 40-week SHRs, which could indicate its enhanced absorption (Hanh et al., <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0009" target="_blank">2017</a>; Fig. <a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-fig-0003" target="_blank">3</a>). Although the mechanisms underlying the elevated expression of PepT1 are still not clear, we speculated that chronic inflammation and hypertension in ageing individuals could be involved in the regulation of intestinal PepT1 (Ingersoll et al., </em><a href="https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0014" target="_blank"><em>2012</em></a>).</p></blockquote><p></p>
[QUOTE="BadassBlues, post: 271242, member: 38526"] There have been studies done on the intestinal absorption of small peptides. It appears that they are easily absorbed, and that absorption can be enhanced by dietary factors. [URL unfurl="true"]https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048[/URL] [HEADING=1][I]Summary[/I][/HEADING] [I] Peptides display diverse structural features because of their varied amino acid compositions. The structural diversity often imparts them complex physiological functions, or possible health-beneficial effects. Some small peptides (di-/tripeptides) exert preventive effects against conditions such as hypertension, hypercholesterolaemia and atherosclerosis. Despite their health benefits, a limited understanding of peptide absorption may hinder their extensive application. Therefore, this review briefly introduces the in vitro and in vivo findings on the intestinal absorption of small peptides and potential factors affecting their absorption. [/I] [HEADING=1][I]Factors affecting the absorption of small peptides[/I][/HEADING] [I]Current studies on the absorption of peptides are mainly conducted by a single oral administration of target peptides. However, as a food material, it is possible that co-existing compounds present in a food matrix could affect the absorption of peptides. For instance, although PepT1 exhibits a certain level of transport capacity and dose dependency (Jappar et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0016']2011[/URL]), the absorption of targeted small peptides could be competitively restricted when co-existing compounds share the same PepT1 transport pathway. In previous studies, we demonstrated that the transport of dipeptides Val-Tyr (Hong et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0012']2013[/URL]) and Trp-His (Tanaka et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0039']2015[/URL]) was inhibited by the existence of a PepT1 substrate Gly-Sar, using an ex vivo chamber transport experiment. Also, the blood concentration of a PepT1-transported dipeptidyl drug, captopril significantly decreased when administered simultaneously with a dipeptide Val-Tyr (Matsui et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0024']2006[/URL]). In such cases, the transport of dipeptide(s) mainly depends on the affinity (Km) to PepT1. On the contrary, some food compounds could alter the absorption of dipeptides by adjusting the expression of PepT1. [B]It has been reported that dietary amino acids and protein (hydrolysates) could up-regulate the expression of intestinal PepT1 mRNA to increase the intestinal transporter capacity of PepT1 and facilitate the absorption of peptides [/B](Shiraga et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0032']1999[/URL]; Osmanyan et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0031']2018[/URL]). Meanwhile, theaflavins, polymeric catechins, have been reported to down-regulate the expression of PepT1 via the activation of intracellular AMP-dependent kinase, thus restricting the transport of dipeptides (Takeda et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0035']2013[/URL]). In addition, Wenzel et al. ([URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0041']2001[/URL]) examined thirty-three food derived flavonoids and reported that quercetin, genistein, naringin, diosmin, acacetin and chrysin had the potential to increase the absorption of PepT1-transported compounds by activation of apical Na+/H+-exchanger to maintain the proton gradient which serves as a driving force for PepT1-mediated transport. Similarly, because a proton is released when a non-charged fatty acid enters the cytosol, [B]dietary fatty acids could also facilitate the absorption of dipeptides by maintaining the transmembrane proton flux [/B](Spanier et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0034']2009[/URL]; Fig. [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-fig-0003']3[/URL]). With regards to other macronutrients, carbohydrates have been reported to stimulate intestinal tissue anabolism, thus incorporating more peptides into the intestinal cells than released into blood circulation. In contrast, addition of fibre increased the systemic availability of di-/tripeptides (Ten Have et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0040']2015[/URL]). However, information is still limited on the effects of respective macronutrients on the absorption of small peptides. [URL='https://ifst.onlinelibrary.wiley.com/cms/asset/3577b5a0-b241-4d76-8cbe-280f6a3c4545/ijfs14048-fig-0003-m.jpg'][IMG alt="Details are in the caption following the image"]https://ifst.onlinelibrary.wiley.com/cms/asset/28628ce8-492e-4ee1-8723-9c834c9c2286/ijfs14048-fig-0003-m.png[/IMG][/URL] [B]Figure 3[/B] [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#']Open in figure viewer[/URL][URL='https://ifst.onlinelibrary.wiley.com/action/downloadFigures?id=ijfs14048-fig-0003&doi=10.1111%2Fijfs.14048']PowerPoint[/URL] Factors affecting the absorption of small peptides. Food and non-food factors could affect the absorption of small peptides potentially via (1) competitive inhibition of PepT1, (2) transcriptional regulation of PepT1 and (3) maintenance of the proton gradient (a driving force for PepT1-mediated transport). Besides food factors, the absorption of small peptides could also be affected by other factors such as health of the individual. In a recent study, we reported enhanced absorption of dipeptides Gly-Sar and Trp-His in 40-week-old spontaneously hypertensive rats (SHRs) and compared them to 8-week young SHRs. We discovered that the expression of intestinal PepT1 was significantly (~1.5-fold) higher in the 40-week SHRs, which could indicate its enhanced absorption (Hanh et al., [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0009']2017[/URL]; Fig. [URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-fig-0003']3[/URL]). Although the mechanisms underlying the elevated expression of PepT1 are still not clear, we speculated that chronic inflammation and hypertension in ageing individuals could be involved in the regulation of intestinal PepT1 (Ingersoll et al., [/I][URL='https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/ijfs.14048#ijfs14048-bib-0014'][I]2012[/I][/URL]). [/QUOTE]
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