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At least 181 records · Page 10Linked to original sources
PubMed1977

Structure-activity relationships of gastrointestinal hormones: motilin, GIP, and [27-TYR]CCK-PZ.

The docosapeptide and the tritetracontapeptide corresponding to the entire amino acid sequence of porcine motilin and gastric inhibitory peptide were synthesized, and in addition, an unsulfated form of cholecystokinin-pancreozymin (CCK-PZ) was prepared to cast some light on the structure-activity relationships of these gastrointestinal hormones. In a series of motilin peptides, elimination of the pentapeptide from the amino terminus decreased the activity (in vitro contraction of rabbit duodenal muscle) to 1/250 of the whole molecule, and subsequent removal of the tripeptide Thr-Tyr-Gly resulted in the complete loss of its effects, In a series of gastric inhibitory peptides, two fragments corresponding to positions 1 to 28 and 26 to 43 were both inactive. However, the nonacosapeptide (15 to 43) retained one-fourth of the activity of the tritetracontapeptide (suppression of the gastric acid secretion stimulated by tetragastrin in Heidenhain pouch dogs). Synthetic [27-Tyr]CCK-PZ exhibited 1/250 of the activity of natural CCK-PZ (amylase release from rat pancreas). This compound was smoothly and efficiently labeled with 125I (specific activity 200 to 250 muc per mug).

Amino Acid Sequence↗
PubMed2003

Casein and whey exert different effects on plasma amino acid profiles, gastrointestinal hormone secretion and appetite.

Protein, generally agreed to be the most satiating macronutrient, may differ in its effects on appetite depending on the protein source and variation in digestion and absorption. We investigated the effects of two milk protein types, casein and whey, on food intake and subjective ratings of hunger and fullness, and on postprandial metabolite and gastrointestinal hormone responses. Two studies were undertaken. The first study showed that energy intake from a buffet meal ad libitum was significantly less 90 min after a 1700 kJ liquid preload containing 48 g whey, compared with an equivalent casein preload (P<0.05). In the second study, the same whey preload led to a 28 % increase in postprandial plasma amino acid concentrations over 3 h compared with casein (incremental area under the curve (iAUC), P<0.05). Plasma cholecystokinin (CCK) was increased by 60 % (iAUC, P<0.005), glucagon-like peptide (GLP)-1 by 65 % (iAUC, P<0.05) and glucose-dependent insulinotropic polypeptide by 36 % (iAUC, P<0.01) following the whey preload compared with the casein. Gastric emptying was influenced by protein type as evidenced by differing plasma paracetamol profiles with the two preloads. Greater subjective satiety followed the whey test meal (P<0.05). These results implicate post-absorptive increases in plasma amino acids together with both CCK and GLP-1 as potential mediators of the increased satiety response to whey and emphasise the importance of considering the impact of protein type on the appetite response to a mixed meal.

Adult↗
PubMed1978

Stimulation of adenylate cyclase in homogenates of isolated intestinal epithelial cells from hamsters. Effects of gastrointestinal hormones, prostaglandins, and deoxycholic and ricinoleic acids.

The mechanism by which intestinal secretagogues evoke fluid secretion in the small bowel and colon has been suggested to involve mucosal adenylate cyclase. Adenylate cyclase activity was assayed by conversion of [32P]ATP to [32P]cyclic AMP in a system of pure epithelial cells isolated from the small intestine of the hamster by vibration in buffer. Several gastrointestinal hormones were tested for their capacity to stimulate adenylate cyclase; vasoactive intestinal peptide and impure cholecystokinin-pancreozymin (but not the 99% pure preparation or pure cholecystokinin octapeptide) were potent stimuli, but pentagastrin, glucagon, secretin, and gastric inhibitory peptide were impotent. Two prostaglandins, PGE1 and PGE2, were potent stimuli of adenylate cyclase. Two other compounds that provoke intestinal secretion of fluid, deoxycholic acid and ricinoleic acid (castor oil), were ineffective stimuli of adenylate cyclase. These experiments do not support a clear-cut relationship between a compound's ability to stimulate adenylate cylase and its activity as an intestinal secretagogue.

Adenylyl Cyclases↗
PubMed2005

Role of gastrointestinal hormones in neuroblastoma.

As a neuroendocrine tumor, neuroblastoma expresses various gastrointestinal (GI) hormones, such as vasoactive intestinal peptide, gastrin-releasing peptide (GRP), neurotensin, and somatostatin, which exert diverse cellular functions in neuroblastoma. In particular, we have recently found that GRP and its cell surface receptor, GRP-R, are abundantly expressed in neuroblastomas. Moreover, more advanced-stage neuroblastomas demonstrated an increased level of GRP-R, suggesting an important role of GRP in aggressive tumor behavior. This review describes the role of several GI hormones commonly expressed in neuroblastoma and discusses in depth the mitogenic actions of GRP in neuroblastoma. In addition, the molecular mechanisms involved in the GRP-induced stimulation of neuroblastoma cell growth are discussed. Our study results demonstrate a role of GRP as an autocrine/paracrine growth factor and elucidate involvement of specific intracellular signaling, the phosphatidylinositol 3-kinase pathway, in the growth regulation of neuroblastoma.

Biomarkers↗