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PubMed1999

The role of enterostatin and apolipoprotein AIV on the control of food intake.

Procolipase is secreted as a protein consisting of 101 amino acids. In the intestinal lumen, procolipase is activated by trypsin and cleaves to form the active colipase and the pentapeptide from the amino terminus. This pentapeptide is called enterostatin. Pancreatic procolipase synthesis is stimulated by a high-fat diet. A large body of evidence has been gathered in the past decade demonstrating the role of enterostatin in the inhibition of food intake; in particular, fat intake. This aspect of enterostatin will be discussed in this review. Other functions of enterostatin such as the inhibition of insulin secretion, will not. Apolipoprotein AIV is a protein synthesized by the human intestine. Similar to procolipase, the synthesis and secretion of apo AIV are also stimulated by fat absorption. In 1992, Fujimoto et al. first demonstrated that apo AIV is a satiety signal secreted by the small intestine following the ingestion of a lipid meal. Subsequently, this initial observation was followed by a number of studies supporting apo AIV's role in the inhibition of food intake. This review will discuss the role of apo AIV in inhibiting food intake.

Animals↗
PubMed1997

Pancreatic enzyme secretion in response to test meals differing in the quality of dietary fat (olive and sunflowerseed oils) in human subjects.

The aim of the present study was to investigate in human subjects whether or not the ingestion of two liquid meals that differed only in their fatty acid composition (due to the addition of olive oil (group O) or sunflowerseed oil (group S) as the source of dietary fat) would lead to differences in the pancreatic enzyme activities secreted into the duodenum. The experiments were performed in eighteen cholecystectomized subjects who, during the 30 d period immediately before surgery, modified their habitual diets in such a way that their fat composition would reflect, as far as possible, that of the experimental meals. Lipase (EC 3.1.1.3), colipase, amylase (EC 3.2.1.1), chymotrypsin (EC 3.4.21.1) and trypsin (EC 3.4.21.4) activities were measured in duodenal contents aspirated before and after the ingestion of the test meals. The plasma levels of secretin and cholecystokinin (CCK) were also examined. Duodenal enzyme activities were similar in resting conditions. No significant differences were revealed in postprandial enzyme activities, except for lipase activity, which was higher in group O, probably in relation to the greater plasma CCK concentrations observed in this group. In the absence of enzyme output data, we should not exclude the possibility that the type of dietary fat will affect human pancreatic enzyme secretion to a greater extent than is evident from the present study, for instance through a flow-mediated effect, as we previously observed in dogs.

Amylases↗
PubMed1997

Molecular mechanisms of rat and human pancreatic triglyceride lipases.

Dietary fats affect health and disease. The assimilation of dietary fats into the body requires that they be digested by lipases. One lipase, pancreatic triglyceride lipase, is essential for the efficient digestion of dietary fats. Pancreatic triglyceride lipase is the archetype of the lipase gene family that includes two homologues of pancreatic triglyceride lipase, pancreatic lipase-related proteins 1 and 2. In recent years, important advances have been made in delineating the mechanisms of lipolysis. The cDNA sequences encoding pancreatic triglyceride lipase and the related proteins have been described. The tertiary structure of human pancreatic triglyceride lipase has been determined alone and in a complex with colipase, a pancreatic protein required for lipase activity in the duodenum. This structural information has allowed the rational design of site-specific mutants of pancreatic triglyceride lipase. Together with the structural information, these mutants have greatly advanced our understanding of the molecular details governing lipolysis. This review describes these studies, which will eventually provide the background for the rational design of nutrition therapy in patients with pancreatic insufficiency and fat malabsorption.

Amino Acid Sequence↗
PubMed2001

Exocrine pancreatic secretion is stimulated in piglets fed fish oil compared with those fed coconut oil or lard.

An experiment was conducted to study the effect of feeding diets containing fat sources with different fatty acid composition (fish oil, coconut oil or lard, 10 g/100 g diet) on exocrine pancreatic secretion in piglets after weaning. A total of 16 barrows were weaned at 4 wk of age; 3 d later, they were surgically fitted with a catheter in the pancreatic duct for continuous collection of pancreatic juice. Collections of pancreatic juice were made every other day starting 4 d postsurgically. Piglets fed the fish oil diet secreted a significantly greater volume of pancreatic juice than piglets fed the coconut oil or lard diets. The output [U/(h. kg(0.75))] of lipase was higher in piglets fed fish oil than in piglets fed lard or coconut oil. The output of colipase was greater in piglets fed fish oil and coconut oil than in those fed lard. The dietary treatments did not affect the output of carboxylester hydrolase. The output of trypsin was significantly lower in piglets fed lard than in piglets fed fish oil or coconut oil diets and the output of carboxypeptidase B was greater in those fed the fish oil diet. Protein, chymotrypsin, carboxypeptidase A, elastase and amylase outputs did not differ among the dietary treatment groups. The apparent digestibilities of nutrients and energy were measured in feces and did not differ among groups. Thus, the greater output of lipase in fish oil-fed piglets did not result in a greater digestibility of fat in this diet.

Animals↗
PubMed1994

Structure-function relationships in naturally occurring mutants of pancreatic lipase.

From primary structure comparison, the pancreatic lipase family is now divided into three subgroups: classical pancreatic lipases, pancreatic lipase-related proteins 1 (RPI) and pancreatic lipase-related proteins 2 (RP2). Among the RP2 subfamily, the guinea-pig and coypu enzymes share kinetic properties which differ from those of classical pancreatic lipases. Both enzymes display a high phospholipase activity and are not interfacially activated using a short chain triglyceride as substrate. Their activity towards insoluble triglycerides is inhibited by micellar concentrations of bile salts and is not restored by addition of colipase. These atypical kinetic properties are discussed in the light of amino acid sequence comparison between RP2 and classical pancreatic lipases, based on the closed and open conformations of the 3-D structure of human pancreatic lipase.

Amino Acid Sequence↗
PubMed1991

Pancreatic procolipase activation peptide-enterostatin-inhibits pancreatic enzyme secretion in the pig.

Pancreatic procolipase, a protein cofactor for lipase, is activated by trypsin, with a simultaneous formation of colipase and a pentapeptide with the sequence Val-Pro-Asp-Pro-Arg (VPDPR). This peptide was found to significantly inhibit pancreatic protein secretion after intraduodenal infusion in pigs (2 mg/kg/h). The inhibition, amounting to 60%, occurred under base-line conditions as well as after stimulation with cholecystokinin (CCK)/secretin (1 U of each peptide/h/kg body wt). In contrast, intravenous infusion of VPDPR (0.2 mg/h/kg) did not affect pancreatic secretion. There was no significant change in the plasma levels of pancreatic polypeptide, insulin, glucagon, or glucose following intraduodenal infusion of VPDPR. It is concluded that the procolipase activation peptide might have an inhibitory function in pancreatic enzyme secretion mediated indirectly through a gut action. Therefore, the lipolytic enzymes of pancreas may also take part in the feed-back regulation of the pancreatic function. We suggest the name enterostatin for this novel regulatory peptide.

Amino Acid Sequence↗
PubMed1995

Kinetics of the two-step hydrolysis of triacylglycerol by pancreatic lipases.

Pancreatic lipases catalyze the hydrolysis of triacylglycerol in a sequential manner. First, triacylglycerol is hydrolyzed to 1,2-diacylglycerol, which is subsequently converted to 2-monoacylglycerol. We studied the kinetics of trioleoylglycerol hydrolysis by rabbit and human pancreatic lipases. The products (acylglycerols and fatty acid) were analyzed by extraction from the reaction mixture, separation by thin-layer chromatography, and quantification by capillary gas chromatography. The first-order rate constants of trioleoylglycerol and dioleoylglycerol hydrolysis were calculated showing that both enzymes hydrolyze dioleoylglycerol faster than trioleoylglycerol. Using rabbit pancreatic lipase, we found that deoxycholate enhanced dioleoylglycerol hydrolysis to a higher degree than trioleoylglycerol hydrolysis. Colipase increased both rate constants similarly at high deoxycholate concentrations (35 mM), while at low concentrations (5 mM) a selectivity toward trioleoylglycerol was observed. From the variation of the rate constants with respect to temperature, we calculated the apparent activation energies of trioleoylglycerol and dioleoylglycerol hydrolysis to be 59.8 kJ.mol-1 and 53.5 kJ.mol-1, respectively. Upon storage, both rabbit and human pancreatic lipases showed a greater loss of activity toward dioleoylglycerol as compared to trioleoylglycerol, suggesting that different conformational elements of the enzyme molecule are responsible for the interaction with each substrate.

Animals↗
PubMed1979

Watching fat digestion.

During fat digestion a number of physicochemical events can be seen directly by light microscopy. Under simulated physiological conditions, hydrolysis of emulsified fat droplets by human pancreatic lipase in the presence of colipase and bile salt micelles proceeds with the sequential formation of two visible product phases. A lamellar liquid crystalline or crystalline phase containing calcium and ionized fatty acid forms first; this is followed by the production of a "viscous isotropic" phase composed predominantly of monoglycerides and protonated fatty acids.

Bile Acids and Salts↗
PubMed1986

Bile acid secretion in cystic fibrosis: evidence for a defect unrelated to fat malabsorption.

In order to define basic biliary defects not related to steatorrhoea in cystic fibrosis, we studied 12 control and 18 cystic fibrosis subjects, with a wide range of pancreatic function. Duodenal aspirates were collected over three consecutive 20 minute periods, during continuous intravenous infusion of cholecystokinin and secretin using a marker perfusion technique, and analysed for pancreatic enzyme output (colipase, lipase, trypsin), bile acid output and concentration, and biliary lipids. Cystic fibrosis patients, at all levels of pancreatic function, had significantly reduced total bile acid output (mumol/kg/h) with delayed appearance of the bile acid peak, compared with control subjects. Actual duodenal bile acid concentrations were significantly higher in cystic fibrosis subjects than in controls, however, probably because of the markedly reduced water output shown in these patients. The lithogenic index was not raised in cystic fibrosis patients at any level of pancreatic function. The reduced bile acid output and the delayed peak appearance probably reflect a defect in gall bladder responsiveness which is independent of pancreatic function and steatorrhoea. Whether this defect is related to gall bladder filling or a defective peptide hormone response awaits further study.

Adolescent↗
PubMed1981

Mechanisms of intestinal fat absorption.

Even though most of the major controversies regarding intestinal fat absorption have been resolved over the past three decades, our concepts of fat digestion and absorption continue to be modified, and new concepts have emerged. The purpose of this review is to summarize advances in our understanding of fat digestion and absorption since the topic was last reviewed by Johnston in 1968. The discussion will emphasize 1) the role of colipase and its interactions with lipase, bile salt micelle, and triglyceride substrate; 2) the importance of the unstirred water layer in fat absorption; 3) micellar formation and dissociation; 4) the role of fatty acid binding protein; 5) factors influencing the reesterification mechanisms in the intestine; and 6) intestinal contribution to lipoprotein and apoprotein production. The importance of these new concepts and the remaining gaps in our understanding of these complex digestive and absorptive processes are discussed.

Animals↗
PubMed2003

Pancreatic triacylglycerol lipase in a hibernating mammal. II. Cold-adapted function and differential expression.

Thirteen-lined ground squirrels (Spermophilus tridecemlineatus) exploit the low-temperature activity of pancreatic triacylglycerol lipase (PTL) during hibernation. Lipolytic activity at body temperatures associated with hibernation was examined using recombinant ground squirrel and human PTLs expressed in yeast. Both the human and ground squirrel enzymes displayed high activity at temperatures as low as 0 degrees C and showed Q10 values of 1.2-1.5 over a range of 37-7 degrees C. These studies indicate that low-temperature lipolysis is a general property of PTL and does not require protein modifications unique to mammalian cells and/or the hibernating state. Western blots show elevated levels of PTL protein during hibernation in both heart and white adipose tissue (WAT). Significant increases in PTL gene expression are seen in heart, WAT, and testes; but not in pancreas, where PTL mRNA levels are highest. Upregulation of PTL in testes is also accompanied by expression of the PTL-specific cofactor, colipase. The multi-tissue expression of PTL during hibernation supports its role as a key enzyme that shows high activity at low temperatures.

Adipose Tissue↗
PubMed1988

Influence of hydrocortisone on the development of pancreas in suckling rats. Ultrastructural morphometric and biochemical studies.

The effect of hydrocortisone on the growth and differentiation of the pancreas was examined in suckling rats. Three doses of hydrocortisone (40, 20, 5 mg/kg/day) were administered during the second week of life. Biochemical and ultrastructural morphometric studies were performed on the pancreas at the end of the treatment. Whatever the dose used, hydrocortisone induced pancreatic hypertrophy and significantly increased enzymatic activities by 70-200% for lipase and colipase, 140-340% for trypsinogen and chymotrypsinogen and 600-1,200% for amylase. With the 20-mg/kg/day dose, ultrastructural morphometric data indicated that the increase in pancreatic weight was associated with cellular exocrine hypotrophy (diminution of cell size, and of the number of zymogen granules). They also suggest that hydrocortisone, at that dose, might enhance the excretion of secretory products. By contrast, the 5-mg/kg/day dose of hydrocortisone did not modify the acinar cell size, but significantly increased the number of granules per cell. The increase in pancreatic weight and the fact that either cellular hypotrophy or no change in acinar cell size was observed, strongly suggest that hyperplasia occurred with both doses. These results confirm that hydrocortisone is an important modulator of pancreatic development in the rat, inducing stimulation of pancreatic activities, associated with modifications in cell structure and components which vary according to the dose.

Aging↗
PubMed1989

Secretory pancreatic stone protein messenger RNA. Nucleotide sequence and expression in chronic calcifying pancreatitis.

The pancreatic stone protein and its secretory form (PSP-S) are inhibitors of CaCO3 crystal growth, possibly involved in the stabilization of pancreatic juice. We have established the structure of PSP-S mRNA and monitored its expression in chronic calcifying pancreatitis (CCP). A cDNA encoding pre-PSP-S has been cloned from a human pancreatic cDNA library. Its nucleotide sequence revealed that it comprised all but the 5' end of PSP-S mRNA, which was obtained by sequencing the first exon of the PSP-S gene. The complete mRNA sequence is 775 nucleotides long, including 5'- and 3'- noncoding regions of 80 and 197 nucleotides, respectively, attached to a poly(A) tail of approximately 125 nucleotides. It encodes a preprotein of 166 amino acids, including a prepeptide of 22 amino acids. No overall sequence homology was found between PSP-S and other pancreatic proteins. Some homology with several serine proteases was observed in the COOH-terminal region, however. The mRNA levels of PSP-S, trypsinogen, chymotrypsinogen, and colipase in CCP and control pancreas were compared. PSP-S mRNA was three times lower in CCP than in control, whereas the others were not altered. It was concluded that PSP-S gene expression is specifically reduced in CCP patients.

Adolescent↗
PubMed1991

Purification of human pancreatic lipase and the influence of bicarbonate on lipase activity.

Pancreatic lipase was purified from human pancreatic juice by ion exchange chromatography and HPLC molecular sieve chromatography. The molecular weight was measured as 50 Kda by SDS-PAGE, as 47 Kda by HPLC and was calculated as 51 Kda following amino acid analysis. The isoelectric point of the purified lipase was 7.4 and maximal enzyme activity occurred at pH 9.5 in glycine buffer (0.1 mol/L) containing deoxycholate (19 mmol/L), colipase (3 mg/L) and triolein (0.3 mmol/L). However, the addition of bicarbonate at a final concentration of 0.1 mol/L decreased the pH for maximal enzyme activity and increased the lipase activity significantly. At higher concentrations of bicarbonate the lipase activity decreased. These results suggest that bicarbonate is an important regulator of lipase activity, perhaps related to an effect on the detergent properties of deoxycholate.

Amino Acids↗
PubMed2001

Measurement of pancreatic lipase activity in serum by a kinetic colorimetric assay using a new chromogenic substrate.

We evaluate a new assay reagent for lipase determination, based on the use of 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6'-methylresorufin) ester (DGGR) as substrate. DGGR is cleaved by lipase, resulting in an unstable dicarbonic acid ester which is spontaneously hydrolysed to yield glutaric acid and methylresorufin, a bluish-purple chromophore with peak absorption at 580 nm. The rate of methylresorufin formation is directly proportional to the lipase activity in the sample. Bile salts, colipase and calcium chloride are included to provide optimal reactivity and specificity. Analysis of total imprecision gave a coefficient of variation of between 5.7% and 9.6%. Anticoagulants, common interfering substances and carboxylesterase had no effect on the assay, but interference by increased concentrations of serum triglycerides was noted. Good correlations were obtained with turbidimetry and a coupled enzymatic method. The estimated reference interval was 6-38 U/L. The unique characteristics of the chromogenic substrate qualify the present method as an innovative approach to serum lipase analysis.

Anticoagulants↗
PubMed1992

[Human pancreatic lipase activity: review of methods and general recommendations].

The properties of human pancreatic lipase are described, especially as regards the influence of the kind and the presentation of the substrate, as well as the effects of bile pigments and colipase. The authors have made a classification of the described methods for the determination of lipase activity in serum or plasma and have proposed recommendations for this assay.

Bile Acids and Salts↗
PubMed1992

Kinetic colorimetric assay of lipase in serum.

We describe a kinetic colorimetric method for assaying lipase (EC 3.1.1.3) activity in serum by using a natural long-chain fatty acid 1,2-diglyceride. In the presence of colipase, deoxycholate, and calcium ions, pancreatic lipase hydrolyzes the clear substrate solution to produce a 2-monoglyceride, which in turn releases glycerol by the action of a 2-monoglyceride lipase. Glycerol is then assayed by a sequence of enzymatic actions (glycerol kinase, glycerol phosphate oxidase, and peroxidase) that produce a violet quinone monoimine dye with peak absorption at 550 nm. The method features zero-order reaction kinetics, provides a simple and rapid assay with an extended dynamic range, is specific and precise, gives results that correlate well (r greater than or equal to 0.99) with those of methods in which emulsified triolein is the substrate, and lends itself readily to automation. For all these reasons, the method seems highly suitable for routine use in clinical laboratories.

Calcium↗
PubMed1992

Two automated fully enzymatic assays for lipase activity in serum compared: positive interference from post-heparin lipase activity.

The fully enzymatic Wako and Ektachem assays for pancreatic lipase in serum were found to yield precise (especially Ektachem) and consistent results that were significantly correlated (r = 0.995). Less good concordance was found with the turbidimetric aca method, results being on several occasions above normal by Wako or Ektachem but within the reference limit by the aca. Supplementation of aca packs with colipase generally increased lipase activities measured by the aca in these samples, thereby improving the correlation with Wako and Ektachem. In vitro addition experiments documented that both Wako and Ektachem were relatively insensitive to common chemical interferences. However, post-heparin lipase activities produced a positive interference in both assays, resulting in seemingly increased lipase activities that were suggestive of pancreatic disease. Substituting sodium glycocholate (6 mmol/L) for deoxycholic acid largely eliminated this positive interference in the Wako assay. Because Ektachem reagents cannot be modified in this way, we added sodium glycocholate (2-12 mmol/L) to sera; however, this failed to dissipate the in vivo effect of heparin on the Ektachem results.

Autoanalysis↗