Aspergillus oryzae-Fermented Wheat Peptone Enhances the Potential of Proliferation and Hydration of Human Keratinocytes through Activation of p44/42 MAPK.

Identifying materials contributing to skin hydration, essential for normal skin homeostasis, has recently gained increased research interest. In this study, we investigated the potential benefits and mechanisms of action of Aspergillus oryzae-fermented wheat peptone (AFWP) on the proliferation and hydration of human skin keratinocytes, through in vitro experiments using HaCaT cell lines. The findings revealed that compared to unfermented wheat peptone, AFWP exhibited an improved amino acid composition, significantly (p < 0.05) higher DPPH scavenging capability and cell proliferation activity, and reduced lipopolysaccharide-induced NO production in RAW 264.7 cells. Furthermore, we separated AFWP into eleven fractions, each ≤2 kDa; of these, fraction 4 (AFW4) demonstrated the highest efficacy in the cell proliferation assay and was found to be the key component responsible for the cell proliferation potential and antioxidant properties of AFWP. Additionally, AFW4 increased the expression of genes encoding natural moisturizing factors, including filaggrin, transglutaminase-1, and hyaluronic acid synthase 1-3. Furthermore, AFW4 activated p44/42 MAPK, but not JNK and p38 MAPK, whereas PD98059, a p44/42 MAPK inhibitor, attenuated the beneficial effects of AFW4 on the skin, suggesting that the effects of AFW4 are mediated via p44/42 MAPK activation. Finally, in clinical studies, AFW4 treatment resulted in increased skin hydration and reduced trans-epidermal water loss compared with a placebo group. Collectively, these data provide evidence that AFW4 could be used as a potential therapeutic agent to improve skin barrier damage induced by external stresses.

Different PTH response to oral peptone load and oral calcium load in patients with normocalcemic primary hyperparathyroidism, primary hyperparathyroidism, and healthy subjects.

BACKGROUND: Normocalcemic primary hyperparathyroidism (PHPT-N) is a condition that may have similar long-term implications to primary hyperparathyroidism (PHPT); however, differential diagnosis and treatment for parathyroid disorders are not clearly defined. We investigated the effect of an oral peptone and an oral calcium load on calcium-regulating hormones in PHPT-N compared with PHPT and healthy controls to provide a new potential diagnostic tool. DESIGN: Case-control study. METHODS: We evaluated serum gastrin, PTH, ionized calcium, and phosphate responses to oral calcium (1 g) and peptone (10 g) load in 22 PHPT and 20 PHPT-N patients matched for PTH serum values. Moreover, 30 healthy subjects were enrolled as controls. In 12 patients for each group, we also performed the oral peptone test adding aluminum hydroxide (AH) to suppress phosphate absorption. RESULTS: In PHPT patients, PTH increased significantly 30 min after the oral peptone load, while no significant increase was found in PHPT-N and controls. After oral calcium load, PTH remained stable in PHPT while it decreased dramatically in PHPT-N patients, and ionized calcium increased significantly in each of the three groups. Peptones plus AH induced a blunted PTH increase in the three groups. CONCLUSIONS: Considering the marked difference in PTH response elicited by peptones in PHPT compared with PHPT-N, we suggest that the oral peptone test could be added to the diagnostic evaluation of PHPT patients. In case of absent response to peptones, patients should have their serum calcium levels assessed twice a year in accordance with recent guidelines.

Cholecystokinin enhances visceral pain-related affective memory via vagal afferent pathway in rats.

BACKGROUND: Pain contains both sensory and affective dimensions. Using a rodent visceral pain assay that combines the colorectal distension (CRD) model with the conditioned place avoidance (CPA) paradigms, we measured a learned behavior that directly reflects the affective component of visceral pain, and showed that perigenual anterior cingulate cortex (pACC) activation is critical for memory processing involved in long-term visceral affective state and prediction of aversive stimuli by contextual cue. Progress has been made and suggested that activation of vagal afferents plays a role in the behavioral control nociception and memory storage processes.In human patients, electrical vagus nerve stimulation enhanced retention of verbal learning performance. Cholecystokinin-octapeptide (CCK), which is a gastrointestinal hormone released during feeding, has been shown to enhance memory retention. Mice access to food immediately after training session enhanced memory retention. It has been well demonstrated that CCK acting on vagal afferent fibers mediates various physiological functions. We hypothesize that CCK activation of vagal afferent enhances visceral pain-related affective memory. RESULTS: In the presented study, infusion of CCK-8 at physiological concentration combining with conditional training significantly increased the CRD-induced CPA scores, and enhanced the pain affective memory retention. In contrast, CCK had no effect on CPA induced by non-nociceptive aversive stimulus (U69,593). The physiological implications were further strengthened by the similar effects observed in the rats with duodenal infusion of 5% peptone, which has been shown to induce increases in plasma CCK levels. CCK-8 receptor antagonist CR-1409 or perivagal application of capsaicin abolished the effect of CCK on aversive visceral pain memory, which was consistent with the notion that vagal afferent modulates affective aspects of visceral pain. CCK does not change the nociceptive response (visceral pain sensitivity) and anterior cingulate cortex neuronal responses to CRD. CONCLUSION: CCK activating vagal afferent C fibers enhances memory consolidation and retention involved in long-term visceral negative affective state. Thus, in a number of gastrointestinal disorders, such as irritable bowel syndrome, nutrient content may contribute to painful visceral perception by enhancing visceral aversive memory via acts on vagal afferent pathway.

Acute parathyroid hormone increase by oral peptones administration after roux-en-Y gastric bypass surgery in obese subjects: role of phosphate in the rapid control of parathyroid hormone release.

BACKGROUND: It is generally considered that changes in serum phosphate levels do not alter parathyroid hormone (PTH) secretion in the absence of concomitant changes in ionized serum calcium level in humans. An acute rise in PTH was shown after phosphate administration by intraduodenal gavage in rats. We aimed to study gastrin, phosphate, PTH, ionized calcium (iCa), and blood pH responses to oral peptones in morbidly obese patients before and after roux-en-Y gastric bypass (RYGB) surgery. METHODS: These parameters were evaluated in response to an oral peptone load in 24 (18 male and 6 female) obese subjects before and 6 months after RYGB surgery. In 12 gastric bypass patients, we also evaluated PTH and phosphate after peptones plus aluminum hydroxide administration to suppress phosphate absorption. RESULTS: Before RYGB, peptones increased gastrin (P < .001), and decreased iCa (P < .01) without changes in PTH or pH. Both phosphate and PTH markedly increased after RYGB with the peptones oral load (P < .01), without changes in pH, iCa, or gastrin. There was a significant, direct relationship between the increase of phosphate and the increase of PTH in the patients treated with aluminum hydroxide (r(2) = 0.78; P < .0001). CONCLUSION: Rapid delivery of peptones in the jejunum in bypassed obese patients results in a significant rise in phosphate and PTH, in the absence of changes of other PTH regulators, possibly mediated by a signaling from the gastrointestinal tract. RYGB patients provide an opportunity to study the control of PTH secretion, with potential relevant clinical implications.

[Effect of peptone blocking asbestos-induced carcinogenesis in rats].

Regular intraperitoneal administration of peptone to rats was initiated immediately and 12 months after intraperitoneal thrice injection of crokidolite UICC in a dose of 20 mg. The rate of peritoneal mesotheliomas was 37.8% after co-administration of peptone and crokidolite, 25.6% following 12 months of crokidolite injection, and 72.1% after use of crokidolite alone. The effect of peptone administration is accounted for by the action of macrophages on transformed mesothelial cells and mesothelioma cells.

Isolation of bioactive peptides from tryptone that modulate lipase production in Yarrowia lipolytica.

In this work the effect of several organic nitrogen sources on lipase production in Yarrowia lipolytica LgX64.81 overproducing mutant was studied. Among them, tryptone and peptone showed the most prominent stimulatory effect. Interestingly, only tryptic and peptic casein digest were found to highly induce lipase biosynthesis while lipase production was very limited in the presence of casein digest from papain and pronase-catalysed hydrolysis and absent in case of chymotryptic digest. It was also demonstrated that the stimulatory peptides should be present in the culture medium at specific proportions and molecular size to match the physiological requirement of Yarrowia lipolytica strain for lipase biosynthesis. Herein, the lipase-production stimulatory peptides were isolated by ion exchange chromatography for the first time. These results had contributed to gain an insight on tryptone role in lipase production by Yarrowia lipolytica. Moreover the use of a chemically defined medium supplemented with the isolated peptides, will improve the efficiency of the process for lipase production in this yeast.

Pork peptone stimulates cholecystokinin secretion from enteroendocrine cells and suppresses appetite in rats.

We found that soybean beta-conglycinin peptone (BconP) suppresses food intake through cholecystokinin (CCK) release from enteroendocrine cells in association with binding of the peptone to rat small intestinal brush border membrane (BBM). The aim of the present study was to find new appetite suppressing peptides. Peptones from chicken, pork, beef, beef liver, and egg white were examined for activities to bind with rat BBM, CCK-release from enteroendocrine cell line STC-1, and induce satiety in rats. Chicken and pork peptone (ChickP and PorkP) bound to BBM with highest ability as evaluated with a surface plasmon biosensor. PorkP and ChickP released CCK in higher amounts than BconP from STC-1 cells dose-dependently, with highest stimulation by PorkP. An orogastric preload of PorkP, but not ChickP, suppressed food intake similarly to BconP, dose-dependently. These results suggest that PorkP interacts directly with the small intestinal CCK cells to release CCK, and that it suppresses appetite in rats.

Dissimilar PTH, gastrin, and calcitonin responses to oral calcium and peptones in hypocalciuric hypercalcemia, primary hyperparathyroidism, and normal subjects: a useful tool for differential diagnosis.

UNLABELLED: We analyzed gastrin, PTH, and calcitonin responses to oral calcium and peptones in hypocalciuric hypercalcemia, mild primary hyperparathyroidism, and normal controls. We observed diverse hormonal responses that may help in the differential diagnosis of these conditions. INTRODUCTION: Hypocalciuric hypercalcemia (HH) is consequent to calcium-sensing receptor (CaSR) genetic mutations or anti-CaSR antibodies. CaSR is expressed in parathyroid tissue, thyroid C cells, and gastrin-secreting cells, where it has been suggested that on calcium and/or amino acid allosteric activation, promotes gastrin secretion. MATERIALS AND METHODS: We evaluated gastrin, PTH, and calcitonin responses to oral calcium (1 g) and peptones (10 g) in 10 patients with HH (mean age, 58.5 +/- 10.3 years; F/M = 9/1), 15 patients with primary hyperparathyroidism (PH; mean age, 60.4 +/- 8.3 years; F/M = 11/4), and 30 healthy controls (mean age, 60.3 +/- 8.1 years). Statistical analyses for differences during oral loading tests were calculated with ANOVA for repeated measurements and comparisons between two groups were performed with Student's t-test. RESULTS: PTH response to peptones was markedly increased in patients with PH compared with flat responses in controls and HH patients (p < 0.05). Gastrin increase after oral calcium was absent in HH and PH subjects (p < 0.05 versus controls), and gastrin responses to peptones were blunted in HH and PH subjects compared with controls (p < 0.05). PTH drop and calcitonin increase after calcium load observed in controls were absent in HH and PH subjects (p < 0.05). CONCLUSIONS: The marked difference in PTH response elicited by peptones observed in PH compared with subjects with HH may help in the differential diagnosis of these conditions without genetic studies. Peptones may stimulate CaSR-controlled hormones as an allosteric regulatory pathway. CaSR abnormalities may help to explain the different calcium- and peptones-induced hormonal responses observed in PH and HH compared with normal subjects.

Increased gastrin and calcitonin secretion after oral calcium or peptones administration in patients with hypercalciuria: a clue to an alteration in calcium-sensing receptor activity.

The calcium-sensing receptor (CaSR) has been detected in human antral gastrin-secreting cells, where, upon calcium and/or amino acid allosteric activation, it stimulates gastrin secretion. Patients with absorptive hypercalciuria (AH) display an enhanced gastric acid output; therefore, we evaluated the secretion of gastrin in subjects with AH (30 subjects vs. 30 healthy female controls, all postmenopausal) after oral calcium administration (1 g calcium gluconate) and, on a separate occasion, after peptone loading test (protein hydrolyzed, 10 g). Gastrin and monomeric calcitonin responses were higher in AH after both oral calcium administration (P < 0.01) and peptone loading (P < 0.01). Because the activation of CaSR by oral calcium and peptones directly induces gastrin release, the higher gastrin responses to these stimuli suggest an increased sensitivity of gastrin-secreting cells CaSR in patients with AH. A similar alteration in thyroid C cells might explain the enhanced calcitonin responses to both calcium and peptones. If the same alterations should in addition be present in the distal tubule (where CaSR is expressed as well), then a possible explanation for amino acid-induced hypercalciuria in AH would have been identified.

Abdominal vagal mediation of the satiety effects of CCK in rats.

CCK type 1 (CCK1) receptor antagonists differing in blood-brain barrier permeability were used to test the hypothesis that satiety is mediated in part by CCK action at CCK1 receptors on vagal sensory nerves innervating the small intestine. Devazepide penetrates the blood-brain barrier; A-70104, the dicyclohexylammonium salt of N alpha-3-quinolinoyl-D-Glu-N,N-dipentylamide, does not. At dark onset, non-food-deprived control rats and rats with subdiaphragmatic vagotomies received a bolus injection of devazepide (2.5 micromol/kg i.v.) or a 3-h infusion of A-70104 (3 micromol.kg(-1).h(-1) i.v.) either alone or coadministered with a 2-h intragastric infusion of peptone (0.75 or 1 g/h). Food intake was determined from continuous computer recordings of changes in food bowl weight. In control rats both antagonists stimulated food intake and attenuated the anorexic response to intragastric infusion of peptone. In contrast, only devazepide was effective in stimulating food intake in vagotomized rats. Thus endogenous CCK appears to act both at CCK1 receptors beyond the blood-brain barrier and by a CCK1 receptor-mediated mechanism involving abdominal vagal nerves to inhibit food intake.

Effects of peripheral CCK receptor blockade on feeding responses to duodenal nutrient infusions in rats.

Type A cholecystokinin receptor (CCKAR) antagonists differing in blood-brain barrier permeability were used to test the hypothesis that duodenal delivery of protein, carbohydrate, and fat produces satiety in part by an essential CCK action at CCKARs located peripheral to the blood-brain barrier. Fasted rats with open gastric fistulas received devazepide (1 mg/kg iv) or A-70104 (700 nmol. kg(-1). h(-1) iv) and either a 30-min intravenous infusion of CCK-8 (10 nmol. kg(-1). h(-1)) or duodenal infusion of peptone, maltose, or Intralipid beginning 10 min before 30-min access to 15% sucrose. Devazepide penetrates the blood-brain barrier; A-70104, the dicyclohexylammonium salt of Nalpha-3-quinolinoyl-d-Glu-N,N-dipentylamide, does not. CCK-8 inhibited sham feeding by approximately 50%, and both A-70104 and devazepide abolished this response. Duodenal infusion of each of the macronutrients dose dependently inhibited sham feeding. A-70104 and devazepide attenuated inhibitory responses to each macronutrient. Thus endogenous CCK appears to act in part at CCKARs peripheral to the blood-brain barrier to inhibit food intake.

Effects of peripheral CCK receptor blockade on gastric emptying in rats.

Type A CCK receptor (CCKAR) antagonists differing in blood-brain barrier permeability [devazepide penetrates; the dicyclohexylammonium salt of Nalpha-3-quinolinoyl-d-Glu-N,N-dipentylamide (A-70104) does not] were used to test the hypothesis that duodenal nutrient-induced inhibition of gastric emptying is mediated by CCKARs located peripheral to the blood-brain barrier. Rats received A-70104 (700 or 3,000 nmol. kg(-1). h(-1) iv) or devazepide (2.5 micromol/kg iv) and either a 15-min intravenous infusion of CCK-8 (3 nmol. kg(-1). h(-1)) or duodenal infusion of casein, peptone, Intralipid, or maltose. Gastric emptying of saline was measured during the last 5 min of each infusion. A-70104 and devazepide abolished the gastric emptying response to a maximal inhibitory dose of CCK-8. Each of the macronutrients inhibited gastric emptying. A-70104 and devazepide attenuated inhibitory responses to each macronutrient. Intravenous injection of a CCK antibody to immunoneutralize circulating CCK had no effect on peptone or Intralipid-induced responses. Thus endogenous CCK appears to act in part by a paracrine or neurocrine mechanism at CCKARs peripheral to the blood-brain barrier to inhibit gastric emptying.

Gastric analysis with fractional test meals (ethanol, caffeine, and peptone meal), augmented histamine or pentagastrin tests, and gastric pH recording.

For centuries it was recognized that the stomach produces a juice, which has acidic properties, however, it was not until 1824 when Prout demonstrated the presence of hydrochloric acid in gastric juice. At the same time experiments on a patient with gastric fistula began by W. Beaumont showing alterations of acid secretion after meals and under various psychological conditions. After the discovery by L. Popielski in 1920 that histamine is a direct stimulant of oxyntic glands, histamine started to be used in the 1930s in gastric secretory tests. Then in 1949 the dose of histamine was established by K. Kowalewski to induce in humans maximal gastric secretion and in 1953 Kay from UK, using a similar dose of histamine (0.04 mg/kg), introduced augmented histamine test to determine maximal acid output. The digestive period of gastric secretion can be divided into 3 phases: cephalic phase, gastric phase, and intestinal phase. When an acidified meal reaches the antrum or proximal part of the small intestine, the inhibitory autoregulatory mechanisms are triggered. Using a peptone meal as a physiological stimulant of gastric secretion, Fordtran and Walsh designed in 1973 the intragastric titration method. Histamine stimulates H1 and H2 receptors, producing some side effects so Betazole (Histalog), an analogue of histamine was introduced, because of smaller side effects than with histamine. In 1967, pentagastrin, which contains a C-terminal amino-acid sequence of gastrin and does not exert serious side effects, was applied first in Poland as a stimulant of gastric acid secretion instead of histamine. At the present time, a 12 or 24 h pH-metry with a magnetic recording of gastric acidity using the Digitrapper was found to have a greater diagnostic value in assessment of gastric acid secretion under natural conditions including meal than classic gastric secretory tests. This technique has been widely used in detecting the duodeno-gastric or gastro-esophageal reflux (GERD) and testing various drugs affecting gastric acid secretion and healing acid-pepsin disorders.

Does the route of feeding modify gastric emptying in rats?

BACKGROUND: It has been shown that the pattern of previous nutrient intake can influence gastric emptying. However, the effect of the absence of enteral stimulation in the setting of a normal energy supply on gastric emptying has not been examined. The aim of this study was to determine whether the absence of enteral stimulation during total parenteral nutrition (TPN) could modify gastric emptying in rats. METHODS: Two experiments were performed. First, gastric emptying of a peptone meal was compared between rats receiving TPN, oral liquid diet (same solution as TPN), or regular diet (control group) for 10 days. In the second experiment, gastric emptying of two test meals (40% peptone and 25% glucose) was studied before and after rats received TPN or intragastric nutrition (same solution as TPN) for 10 to 12 days. RESULTS: In experiment 1, gastric emptying of 40% peptone in the TPN and liquid diet groups was slower than that in the control group. This difference was significant between the TPN group and the control group (p < .01) but not between the liquid diet and control groups (p = .076). Gastric emptying of this meal in the TPN and liquid diet groups was similar. In experiment 2, no difference in gastric emptying of 40% peptone or 25% glucose was found between rats receiving TPN and those receiving intragastric nutrition for 10 to 12 days. CONCLUSIONS: The composition of diet not the route of feeding is important in the modification of gastric emptying by the pattern of previous nutrient intake.

Role of cholecystokinin in the anorexia produced by duodenal delivery of peptone in rats.

We used the cholecystokinin receptor antagonist devazepide to assess the importance of CCK in mediating the anorexia produced by 2-h duodenal infusions of peptone, a protein digest, at dark onset in nonfasted rats. Peptone alone (0.14-2.24 g/h) suppressed food intake dose dependently by 18-96%, with an approximate half-maximal dose of 1 g/h. Peptone-induced reductions in caloric ingestion were comparable to the caloric loads infused. Devazepide alone (30-1,000 microgram/kg) stimulated food intake dose dependently by 30-73%, with a minimal effective dose of 100 micrograms/kg. Devazepide appeared to reverse the anorexic response to peptone (1.1 g/h) dose dependently by 29-65%, with a minimal effective dose of 30 micrograms/kg. The magnitudes of these devazepide-induced effects were similar to, and in some cases were larger than, those produced when the same doses of devazepide were administered alone. Coadministration of devazepide (1,000 micrograms/kg) and a lower peptone dose (0.8 g/h) produced similar results. These results suggest that an essential CCK mechanism plays a significant role in mediating the satiety response to duodenal delivery of protein.

Glucagonlike peptide-1 (GLP-1) participation in ileal brake induced by intraluminal peptones in rat.

The aim of this study was to determine the mechanisms implicated in the gastrointestinal inhibition induced by ovoalbumin hydrolysate infused intraluminally. We studied the site of action, the possible implication of GLP-1, and the nervous mechanisms involved. We prepared anesthetized Sprague-Dawley rats with strain gauges in the antrum, duodenum, and proximal jejunum and a catheter in the duodenum or ileum for peptone infusion. Both intraduodenal (N = 6) and intraileal (N = 5) infusion of ovoalbumin hydrolysate induced inhibition of spontaneous motor activity in the antrum, duodenum, and proximal jejunum. Duodenal inhibition induced by intraduodenal (N = 6) or intraileal (N = 6) infusion of ovoalbumin hydrolysate was reversed by intraarterial infusion of GLP-1 receptor antagonist, exendin (9-39) (3 x 10(-8) mol/kg/40 min). Finally, a combination of the adrenergic blockers phentolamine and propranolol (1 mg/kg, each; N = 7) completely blocked inhibitory gastrointestinal motor actions caused by intraduodenal infusion of ovoalbumin hydrolysate. This study demonstrates that peptone, intraluminally infused, participates in the regulation of gastrointestinal motility through stimulation of adrenergic pathways in anaesthetized rats. Moreover, these effects are partly mediated by GLP-1 secretion. The ileum seems to be the site of action, indicating a role of GLP-1 on the ileal break mechanism.

Intestinal fat-induced inhibition of meal-stimulated gastric acid secretion depends on CCK but not peptide YY.

Fat in small intestine decreases meal-stimulated gastric acid secretion and slows gastric emptying. CCK is a mediator of this inhibitory effect (an enterogastrone). Because intravenously administered peptide YY (PYY) inhibits acid secretion, endogenous PYY released by fat may also be an enterogastrone. Four dogs were equipped with gastric, duodenal, and midgut fistulas. PYY antibody (anti-PYY) at a dose of 0.5 mg/kg or CCK-A receptor antagonist (devazepide) at a dose of 0.1 mg/kg was administered alone or in combination 10 min before the proximal half of the gut was perfused with 60 mM oleate or buffer. Acid secretion and gastric emptying were measured. We found that 1) peptone-induced gastric acid secretion was inhibited by intestinal fat (P < 0.0001), 2) inhibition of acid secretion by intestinal fat was reversed by CCK-A receptor antagonist (P < 0.0001) but not by anti-PYY, and 3) slowing of gastric emptying by fat was reversed by CCK-A antagonist (P < 0. 05) but not by anti-PYY. We concluded that inhibition of peptone meal-induced gastric acid secretion and slowing of gastric emptying by intestinal fat depended on CCK but not on circulating PYY.

Ingredient supplementation effects on viability of probiotic bacteria in yogurt.

The present investigation studied the effects of cysteine, whey powder, whey protein concentrate, acid casein hydrolysates, or tryptone on the viability of Streptococcus thermophilus, Lactobacillus acidophilus, and bifidobacteria. Changes in pH, titratable acidity, redox potential, and viability of bacteria were monitored during 24 h of fermentation and refrigerated storage (4 degrees C) of yogurt for 35 d. The incubation time that was needed to reach pH 4.5 was considerably affected by the added ingredients. Also, the drop in pH or the increase in acidity and redox potential was dependent on the added ingredients. The addition of cysteine, whey protein concentrate, acid casein hydrolysates, or tryptone improved the viability of bifidobacteria to a variable extent, but whey powder failed to improve their viability. The morphology of S. thermophilus, as shown by electron microscopy, was affected by cysteine at 500 mg/L, possibly as a result of reduced redox potential. Sodium dodecyl sulfate-PAGE and amino acid analyses suggested that the nitrogen source in the form of peptides and amino acids improved the viability of bifidobacteria in yogurt made with a commercial ABT (Lactobacillus acidophilus, bifidobacteria, and Streptococcus thermophilus) starter culture, which showed a dramatic decline in the counts of this organism in previous studies.

Peptones stimulate both the secretion of the incretin hormone glucagon-like peptide 1 and the transcription of the proglucagon gene.

Truncated glucagon-like peptide (GLP)-1 is a potent incretin. Its synthesis and secretion are modulated by food, but the influence of individual nutrients remains to be established. The hypothesis that protein hydrolysates (peptones) can directly regulate both GLP-1 secretion and proglucagon (PG) gene transcription was tested in this study, ex vivo in the isolated vascularly perfused rat intestine and in vitro in the murine enteroendocrine cell line STC-1. Peptones were albumin egg hydrolysate (AEH) and meat hydrolysate (MH). We demonstrate in these two models that peptones dose-dependently stimulate GLP-1 release, whereas isocaloric quantities of bovine serum albumin or of an amino acid mixture had no stimulatory effect. A strong and rapid increase of PG RNA level was observed in STC-1 cells treated with peptones (14-fold and 7-fold increase after 4 h of incubation with 3% wt/vol MH and AEH, respectively). Peptones also increased the PG RNA level in the colonic PG-expressing cell line GLUTag. In contrast, peptones did not modify the PG RNA level in two pancreatic glucagon-producing cell lines, namely, the RINm5F and INR1G9 cells. The peptone effect in STC-1 cells was completely abolished by blocking transcription before MH treatment. The stability of proglugacon transcripts was not modified by MH treatment, but nascent transcripts were more abundant in STC-1 cells preincubated with MH. Finally, MH treatment strongly stimulated (15-fold stimulation) the transcriptional activity of two PG gene promoter fragments (-1100 and -350 base pair) linked to the CAT reporter gene transiently transfected in STC-1 cells. Overall, peptones evoke an as yet undescribed release of GLP-1 when brought into contact with native intestinal L-cells or with STC-1 enteroendocrine cells. The increased transcription of the glucagon gene in the latter system suggests an important role of protein hydrolysates in the control of not only the secretion but also the synthesis of the incretin hormone.