Pancreatic lipase activity inhibition

Within the small intestine, bile-acid binding interferes with micelle formation. Nauss et al. [268] reported that, in vitro, chitosan binds bile acid micelles in toto, with consequent reduced assimilation of all micelle components, i.e., bile acids, cholesterol, monoglycerides and fatty acids. Moreover, in vitro, chitosan inhibits pancreatic lipase activity [269]. Dissolved chitosan may further depress the activity of lipases by acting as an alternative substrate [270]. 

For pancreatic lipase to be active, an additional protein, termed colipase, is required (B26). Pure pancreatic lipase is inhibited by bile salts in concentrations exceeding their critical micellar concentrations (B27). The fiinc-tion of coUpase is to restore lipase activity in the presence of bile salts. Although colipase by itself has no lipolytic activity (B27), defective fot digestion and absorption occur if either lipase or colipase activity is low in the small intestine. Patients with steatorrhea due to either isolated lipase deficiency (F4) or isolated cohpase deficiency (H16) have been reported. A lipase which requires bile acids for activity is human milk lipase (Ol). This enzyme comprises 1% of the protein of human milk, but is inactive i ainst milk fots until its activity is stimulated by bile acids in the small intestine. 

It is well known that dietary fat is not absorbed from the intestine unless it has been subjected to the action of pancreatic lipase [1], Previously, we found that basic proteins such as protamines, histones and purothionine inhibited the hydrolysis of triolein emulsified with phosphatidylcholine [2], The inhibition of hydrolysis of dietary fat may cause a decrease or delay in the intestinal absorption of fat and reduce blood chylomicron levels, an excess of which is known to induce obesity [3], Therefore, there was a possibility that inhibitory substances toward pancreatic lipase activity may prevent the onset of obesity induced by feeding a high fat diet to mice. Recently, we found that natural products such as tea saponin, platycodi radix saponin, chitin-chitosan and chondroitin sulfate inhibited the pancreatic lipase activity. In the following section, the anti-obesity effects of these natural products will be described in detail. 

It was demonstrated that the anti-obesity effects of oolong tea in high-fat diet-treated mice might be partly due to the inhibitory actions of the saponin fraction in oolong tea on pancreatic lipase activity. In this study, tea saponin prevented the high-fat diet-induced increases in body and parametrial adipose tissue weights by inhibiting the intestinal absorption of dietary fat via inhibition of pancreatic lipase activity, Fig. (5). 

The aqueous extract of Platycodi radix inhibited the pancreatic lipase activity in a dose-dependent manner in the assay system using triolein emulsified with phosphatidylcholine, Fig. (6). At 2, 3 and 4 h after the administration of the aqueous extract of Platycodi radix, the plasma triacylglycerol concentration was significantly lower in the treated rats than in the control group, Fig. (7). 

It has been reported that various saponins isolated from foodstuffs have anti-obesity or hypolipidaemic actions [12-16], We found that the crude saponin fractions isolated from Platycodi radix strongly inhibited the pancreatic lipase activity, Fig. (10). 

As shown in Fig. (11a), chitin-chitosan inhibited the pancreatic lipase activity dose-dependently between the concentrations of 6.25 p,g/ml and 200 ig/ml in the assay system, using triolein emulsified with lecithin. For characterization of the mechanism involved in the inhibition of pancreatic lipase by chitin-chitosan, the enzyme activity was assayed at various concentrations of lecithin-emulsified triolein and in the presence of increasing concentrations of chitin-chitosan. A Lineweaver-Burk plot of the data in Fig. (11 b) shows that chitin-chitosan was a competitive inhibitor. The Km and Vmax values of the lipase activity for lecithin-emulsified triolein were 6.06 ag/ml and 8.7 nmol/ml/min, respectively. The K value of chitin-chitosan on the lipase activity in lecithin-emulsified triolein was 17.6 M-g/ml. When triolein was emulsified with... 

As shown in Fig. (14), chondroitin sulfate inhibited the pancreatic lipase activity dose-dependently at the concentrations of 1-20 mg/ml in the assay system using triolein emulsified with phosphatidylcholine at 10 mg/ml it inhibited triolein hydrolysis by about 60%. On the other... 

Bile salts inhibit pancreatic lipase activity by coating the substrate and not allowing the enzyme access to the substrate. The colipase relieves the bile salt inhibition, and allows the triglyceride to enter the active site of the lipase. 

Pancreatic lipase is a key enzyme for TAG absorption and many studies have associated polyphenols with lipase inhibition. Sugiyama et al. (2007) showed that oligomeric apple procyanidins had an inhibitory effect on pancreatic lipase activity in vitro which was higher than other polyphenolic compounds of an apple extract. These results were also confirmed in both an animal and a human study where oligomeric apple procyanidins inhibited postprandial TAG absorption. ... 

Mori, T., Satouchi, K., and Matsushita, S., 1973, A protein inhibiting pancreatic lipase activity in soybean seeds,... 

In 1987, scientists at Hoffmann-La Roche described their discovery of hpstatin (5), a secondary metabolite isolated from Strptomyces toxytricini, and demonstrated that it is a potent inhibitor of pancreatic lipase.Simple hydrogenation of 5 formed terahydrolipstatin (1,USAN, orlistat) which possesses comparable biological activity but is more stable than 5. Orlistat (1, Xenical ) works through pancreatic lipase inhibition. Pancreatic lipase is the key enzyme of dietary triglyceride absorption, exerting its activity... 

Patton, J.S. and Carey, M.C. 1981. Inhibition of human pancreatic lipase-colipase activity by mixed bile salt-phospholipid micelles. Am. J. Physiol. 241, G328-G336. 

Like pancreatic lipase, this enzyme is clearly dependent on a lipid/water interface for maximal activity, where it also may reach a very high catalytic rale, Abo like pancreatic lipase, it is not inhibited by serine esterase inhibitors like DFP orPMSF. 

Orlistat (Xenical /Roche) is a reversible gastric and pancreatic lipase inhibitor. The compound has no effect on appetite suppression but rather acts by inhibiting dietary fat absorption from the GI tract. Sibutramine (Meridia /Abbott) and its major active metabolites are re-uptake... 

The only known lipase that is nonspecific is the enzyme of a mold. Geotrichum candidum. It has a decided preference for fatty acids with a cis-A9 double bond such as oleic acid 14). There is no explanation for this specificity. The lipases of most other microorganisms are very similar to pancreatic lipase. For example, the lipase of the mold Rhizopus arrhizus is an exoenzyme which contains carbohydrates that are not essential for activity. It is not inhibited by DFP, it is specific for primary ester groups, and it does not distinguish between diflEerent fatty acids (15). Other microbial lipases are similar in these respects but may diflFer in their recognition of steric hindrance. The lipase of Stapyhlococcus aureus... 

Orlistat is a pentanoic acid ester that binds to and inhibits gastric and pancreatic lipases the resulting inhibition of their activity prevents the absorption of about 30% of dietary fat compared with a normal 5% loss. Weight loss is due to calorie loss but drug-related adverse effects also contribute by diminishing food intake. The drug is not absorbed from the alimentary tract. 

Pancreatic lipase is one of the mammalian key digestive enzymes. It completes the dietary triacylglycerol breakdown initiated by preduode-nal lipases, including lingual and gastric enzymes, (see below). The enzyme is inhibited in the intestine by bile salts, but the activity is restored in the presence of colipase (CLP), a relatively short (95 residues) heat-stable polypeptide secreted by the pancreas (Semeriva and Desnuelle, 1979 Borgstrbm and Erlanson-Albertsson, 1984). The structural details of the interaction of colipase with lipase are described in Section III,C. 

Orlistat. Orlistat acts in the GI tract, where it inhibits pancreatic lipases located in the lumen. Systemic exposure of the drug is not required for pharmacological activity. With negligible oral bioavailability (F < 5%), orlistat is primarily excreted unchanged in the feces. However, several metabolites including (40) and (41) have been identified in the plasma of both normal and obese volunteers. These compounds are formed by hydrolysis cf both the N-formyl leucine ester moiety and the lactone ring and do not exhibit any inhibitory activities toward pancreatic lipases (68) (see Fig. 15.1). 

Patton JS and Carey MC. Inhibition of Human Pancreatic Lipase-Colipase Activity by Mixed Bile Salt-Phospholipid Micelles. Am J Physiol 1981 241 G328-G336. 

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