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Hyperenterostatinemia in premenopausal obese women.
Enterostatins [Val-Pro-Asp-Pro-Arg (VPDPR), Val-Pro-Gly-Pro-Arg (VPGPR), and Ala-Pro-Gly-Pro-Arg (APGPR)] are pentapeptides derived from the NH2-terminus of procolipase after tryptic cleavage and belong to the family of gut-brain peptides. Although enterostatin-like immunoreactivities exist in blood, brain, and gut, and exogenous enterostatins decrease fat appetite and insulin secretion in rats, the roles of these peptides in human obesity remain to be examined. To determine whether VPDPR and APGPR secretion is altered in obesity, serum VPDPR and APGPR levels were measured in 38 overnight-fasted subjects (body mass index, 17.9-54.7 kg/m2) before and after a meal. The mean fasting VPDPR in the serum of lean subjects was significantly lower than that in obese subjects [lean = 603 +/- 86 nmol/L (n = 17); obese, 1516 +/- 227 nmol/L (n = 21); P = 0.0023]. In addition, the rise in serum APGPR after a meal (postmeal/fasting ratio) was significantly higher in lean than in obese subjects [lean, 1.71 +/- 0.24 (n = 17); obese, 1.05 +/- 0.14 (n = 21); P = 0.0332]. The results of these studies show hyperenterostatinemia in obesity and a diminution in enterostatin secretion after satiety.
Enterostatin (VPDPR) has anti-analgesic and anti-amnesic activities.
Enterostatin (VPDPR), an anorexigenic peptide derived from the amino terminus of procolipase, significantly inhibited analgesia induced by the mu-opioid agonist morphine (5 mg/kg, s.c.) after i.c.v. administration to mice at a dose of 100 nmol. On the other hand, VPDPR (approximately 200 nmol, i.c.v.) did not attenuate analgesia induced by the kappa-opioid agonist D-Phe-D-Phe-D-Nle-D-Arg-NH2 (100 microg/mouse, i.c.v.) or delta-opioid agonist DTLET (4 nmol/mouse, i.c.v.). VPDPR (100 nmol, i.c.v.) significantly improved amnesia induced by scopolamine (0.2 mg/kg, i.p.) in mice. However, VPDPR did not enhance memory in normal mice at the same dose.
Effects of enterostatin (Val-Pro-Asp-Pro-Arg) on fat intake and blood levels of glucose and insulin in rats.
Enterostatin may be involved in the preference for fat and the control of fat intake. Using two different feeding patterns, we observed a change in food intake after injection of enterostatin (VPDPR) into the third ventricle. When rats were adapted to free selection choice between low fat (LF) and high fat (HF) diets, VPDPR inhibited intake of the LF diet at 100, 200 and 800 ng and inhibited intake of the HF diet at 200 ng. The dose-response of HF diet intake to VPDPR was U-shaped. However, even the optimal dose (200 ng), which reduced the intake of both LF and HF diets when both diets were given together, was not effective when the LF diet was given alone. In the present study, VPDPR has also shown to not affect plasma glucose or insulin levels. These results suggest that exogenous VPDPR may inhibit appetite when endogenous enterostatin secretion is increased by ingestion of dietary fat, and that VPDPR has a limited range of effects on feeding behavior. We support the hypothesis that the early satiety sense of VPDPR as an anorectic agent in a central site is directly related to endogenous enterostatin or procolipase levels after fat intake, but not glucose or insulin levels.
Gut hormones and related concepts.
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Effect of enterostatin on insulin, glucagon, and somatostatin secretion in the perfused rat pancreas.
Enterostatin is a pentapeptide generated by trypic digestion of procolipase in the small intestine. Both peripheral and central administration of this peptide to rats has been shown to reduce food intake, this reduction being due to specific suppression of fat intake. In perifused pancreatic rat islets, enterostatin has been shown to inhibit the insulin response to a high glucose concentration. In the present study, we have investigated the effect of exogenous enterostatin on insulin, glucagon, and somatostatin secretion by the isolated perfused rat pancreas. Enterostatin, at 100 mmol/l, inhibited the insulin response to 9 mmol/l glucose (by 70%), 0.1 mmol/l tolbutamide (by 40%), and 5 mmol/l arginine (by 70%). Enterostatin had no effect on glucagon and somatostatin release at a maintained glucose level (5.5 mmol/l) or in response to 5 mmol/l arginine. Finally, preinfusion of the rat pancreas with a high enterostatin concentration (500 nmol/l) did not alter the insulin response to glucose, an observation that would rule out a toxic effect of this peptide on the beta-cell. In summary, in the perfused rat pancreas, enterostatin, at putatively physiological concentrations, inhibits insulin secretion without affecting glucagon or somatostatin output, thus pointing to a direct effect of enterostatin on the beta-cell and not through an alpha-cell or delta-cell paracrine effect. Because enterostatin is generated in the small intestine after feeding, it might play a role in the enteroinsular axis as an anti-incretin agent.
Reduction of feed intake in sheep by enterostatin, the procolipase activation peptide.
Enterostatin, a peptide formed during the activation of pancreatic procolipase in the duodenum, is likely a mediator of satiety in the rat. The objective of this research was to determine whether administration of enterostatin into the lateral cerebral ventricle of sheep unfed for 2 h resulted in reduced feed intake. Bolus doses of 2 micrograms did reduce (P < .03) feed intake during the hour after injection by one- to two-thirds of control. Doses 20 micrograms or greater were not effective, and .2 microgram also did not have any statistically significant effect. This range of effective doses was similar to that observed in the rat, and the effective dose of 2 micrograms was approximately 10-fold greater on a per-animal basis, but less on a brain-size basis, than the amount needed to achieve a similar response in the rat. Therefore, enterostatin can reduce feed intake and thus may also be involved in satiety in sheep.
Human pancreatic proenzymes are activated at different rates in vitro.
The rates of activation of procolipase, prophospholipase (proPLA2), chymotrypsinogen, and trypsinogen were studied after incubation of human pancreatic juice with porcine enterokinase in vitro. Under the conditions chosen procolipase was fully activated within 10 min of incubation. Full activation of phospholipase (PLA2) was seen within 15 min, whereas complete activation of chymotrypsin and trypsin was not seen until after 30 to 60 min, respectively. The different proenzymes probably differ in their suitability as substrates for trypsin. A physiologic consequence of a differentiated activation of the pancreatic proenzymes in vivo could be a delayed proteolytic degradation of the lipolytic enzymes in the intestine.
Preparation of porcine pancreatic lipase free of co-lipase activity.
Porcine pancreatic lipase LB was purified and released from co-lipase activity by reduction with beta-mercaptoethanol in the presence of guanidine chloride. The amino acid and carbohydrate composition of the enzyme is presented. The following physical constants were measured or calculated: Molecular weight 52 000, sedimentation coefficient (s degrees 20, w) 4.0 S, diffusion coefficient (D degrees 20, w) 6.7 X 10(-7) cm2 s-1. Stokes' radius (r) 30.3 A, partial specific volume (v) 0.72 cm3 g-1, frictional ratio (f/f0) 1.23 and isoelectric point (pI) 5.18.
Pancreatic lipase/colipase-mediated triacylglycerol hydrolysis is required for cholesterol transport from lipid emulsions to intestinal cells.
This study tested the hypothesis that dietary cholesterol uptake by intestinal cells is dependent on the structure and composition of the lipid carriers in the extracellular milieu. In in vivo experiments with female C57BL/6 mice, cholesterol absorption from phospholipid/triacylglycerol emulsions was significantly reduced by administration of tetrahydrolipstatin, an inhibitor of pancreatic lipase. This inhibitor had no effect on the absorption of cholesterol from phospholipid vesicles. The importance of pancreatic-lipase-mediated triacylglycerol hydrolysis for cholesterol transport from emulsions to intestinal cells was confirmed by in vitro experiments with rat IEC-6 intestinal cells. Cellular uptake of cholesterol from emulsions with a phospholipid/triacylglycerol molar ratio of <0.3 could be stimulated by pancreatic lipase/colipase hydrolysis of the core neutral lipids. However, pancreatic lipase/colipase was ineffective in hydrolysing triacylglycerols in emulsions with a phospholipid/triacylglycerol molar ratio of >0.3. Phospholipase A2-mediated hydrolysis of the surface phospholipids was necessary prior to triacylglycerol hydrolysis in these phospholipid-rich emulsions and to the stimulation of cholesterol transport from these particles to IEC-6 cells. The data also revealed that minimal triacylglycerol hydrolysis was sufficient to significantly increase cholesterol transport from lipid emulsions to the intestinal cells. Thus the products of triacylglycerol hydrolysis, namely monoacylglycerol and non-esterified fatty acids, are key determinants in mediating cholesterol transport from lipid emulsions to intestinal cells. Taken together, these results support the hypothesis that remodelling of the surface and core components of lipid carriers is necessary prior to absorption of dietary cholesterol from the gastrointestinal tract.
The estimation of pancreatic lipase--a brief review.
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[Enterostatin, galanin, and GRP].
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[Lipases of the digestive system].
Studies on gastrointestinal lipolysis have underestimated several important points. In view of recent in vitro data obtained in our laboratories, this review focuses on the role of gastric lipolysis during fat digestion. Polyclonal antibodies generated from purified rat lingual lipase were used to screen a cDNA library prepared from mRNA isolated from the serous glands of rat tongue cloned in E. coli expression vectors. A cDNA clone was isolated and the nucleotide and predicted amino acid sequences obtained. Comparison with the N-terminal amino acid sequence of the purified enzyme confirmed the identity of the cDNA. The amino acid sequence of rat lingual lipase consisted of 377 residues and showed little homology with porcine pancreatic lipase, apart from a short region containing a serine residue at an analogous position to the Ser 152 of the porcine enzyme. Human gastric lipase activity on tributyrin emulsion was detected only in the presence of amphiphiles. This behaviour was in sharp contrast with the strong inhibitory effect of amphiphiles observed on pure pancreatic lipase. To reveal human gastric lipase activity, amphiphiles must be added to human gastric lipase in order to prevent irreversible interfacial denaturation. Human gastric lipase activity was found to be restricted to triacylglycerol/water surface tensions ranging from 8 to 13 dynes/cm. All amphiphiles which decrease interfacial tension to less than 8 dynes/cm act as irreversible inhibitors of human gastric lipase in the absence or presence of bile salts. Our results confirm that human gastric lipase is capable of hydrolysing triacylglycerol in the presence of the bile salts concentration prevailing in the upper small intestine and in the presence of alimentary proteins. These observations could explain the high dietary lipid absorption observed under pancreatic lipase deficiency.
Measurement of lipase activity by a differential pH technique.
This is a new electrochemical method for determination of lipase activity in biological fluids, including serum, plasma, and duodenal juice. Advantages of turbidimetric methods--short reaction time, and small sample and reagent volumes--are combined with those of titrimetric methods: measurement of absolute activity (i.e., no standardization required), saturated substrate conditions, and direct measurement of reaction products. The proposed method is easy, inexpensive, and takes only 3 min. Precision is good: CV = 3.74% within day and 7.3% between days at the clinical-decision concentration, CV = 1.86% within day and 4.65% between days for above-normal lipase activities. The standard curve is linear up to 4500 U/L. Results (y) correlate well with those by turbidimetry (x): y = 0.9287x - 65.3 (r = 0.9719). Reference values are between 0 and 130 U/L.
Interfacial structure and lipase action. Characterization of taurodeoxycholate-didecanoylglycerol monolayers by physical and kinetic methods.
Surface pressure-area isotherms for 1,3-didecanoyl-glycerol (dicaprin) were determined as a function of the concentration of taurodeoxycholate in the subphase. Analysis of these curves indicates that, from 0.05 to 0.80 mM bile salt, surface structure is dependent only on the surface concentration of the diglyceride. The limiting areas for dicaprin in the presence and absence of bile salt were about 38 A2/molecule. Subjecting the monolayers to hydrolysis by pancreatic lipase yielded kinetic data which, together with the physical studies, support a model for monolayer glyceride molecules undergoing discrete changes of state. In the absence of bile salt, the relatively expanded state exhibits an area of 75 A2/diglyceride molecule and is not a substrate for pancreatic lipase B. The more condensed state exhibits an area of 38 A2/diglyceride molecule and is hydrolyzed at a rate proportional to its concentration in the monolayer. Taurodeoxybholate at 0.05 to 0.60 mM shifts the apparent area of the expanded state to 360 A2/diglyceride molecule.
Mass law: what mischief they do in thy name.
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Disorders of lipid absorption.
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Enterostatin from collagen?
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