Preduodenal mechanisms compensate completely for absent pancreatic enzymes to stimulate gallbladder after meals

New insights into in vivo gastroduodenal digestion of oil-in-water emulsions: gastric stability and in vitro digestion modeling

In this paper, effect of emulsion stability on gastroduodenal emptying/secretion was reviewed and differentiated. Moreover, novel perspectives on physiology of gastric lumen, duodenum, and gall bladder were achieved using mathematical models, being useful for designing artificial digestive systems. In this regard, numerical data for dynamic gastric emptying/secretion were offered for gastric-stable and gastric-unstable emulsion intakes. It was shown that alterations in human gastric and duodenal volume follow, respectively, linear and sinusoidal curves, with high correlation coefficients (r² > 0.93). For both emulsions, about 30-40 mL ingesta discharged rapidly from stomach upon ingestion; However, further gastric emptying was regulated for the rest of digestion period, so that 0.1 mL/min oil was passing through duodenum. Intragastric evacuation of both emulsions started with a lag phase during which stomach stored secretions incrementally by slow gastric discharge. Lag phase ended with fat layering, when emptying considerably enhanced. This reduction was gradual for stable emulsion while unstable emulsion experienced a rapid emptying before slow declining trend. Along with initial gastric emptying, 87% of gallbladder content discharged into duodenum, prolonged up to the gradual reduction phase of stomach. Supplementary investigations are needed to quantify gastroduodenal secretions, particularly pepsin and pancreas in response to emulsion ingesta.

Differences in cholecystokinin release and gallbladder contraction between emulsified and nonemulsified long-chain triglycerides

BACKGROUND

Fat is a potent stimulus of cholecystokinin (CCK) release. Apart from lipolysis, fatty acid chain length, and saturation, emulsification may also determine the magnitude of CCK release.

METHODS

We have studied the effect of emulsification of soybean oil on CCK and pancreatic polypeptide (PP) release (radioimmunoassay [RIA]) and gallbladder motility (ultrasonography). Six healthy subjects were studied on three separate occasions in random order during (1) intraduodenal administration of emulsified long-chain triglycerides (LCT) (6 mmol/h for 120 minutes); (2) equimolar amounts of nonemulsified LCT with addition of emulsifier; and (3) saline with emulsifier (control).

RESULTS

Intraduodenal administration of both nonemulsified LCT and emulsified LCT induced significant (p < .05) increases in plasma CCK and PP levels and reductions in gallbladder volume. However, compared with nonemulsified LCT, emulsified LCT resulted in a readier and significantly stronger CCK release (212+/-62 pmol/L per 120 minutes vs 36+/-7 pmol/L per 120 minutes; p < .05); PP release (2034+/-461 pmol/L per 120 minutes vs 671+/-106 pmol/L per 120 minutes; p < .05); and gallbladder contraction (77%+/-2% vs 41%+/-7%; p < .05). No significant alterations were observed in plasma CCK or PP levels and gallbladder volume during administration of saline with emulsifier.

CONCLUSIONS

Intraduodenal administration of a low-dose emulsified LCT more potently stimulates CCK and PP release and gallbladder contraction in comparison to equimolar amounts of nonemulsified LCT. These findings point to an important role for solubilization of LCT in determining the magnitude of CCK release from the intestine.

Influence of orlistat on the regulation of gallbladder contraction in man: a randomized double-blind placebo-controlled crossover study

Orlistat (tetrahydrolipstatin) is a potent inhibitor of gastric and pancreatic lipase activity causing a diminution of free fatty acids in the intestinal lumen. The release of cholecystokinin (CCK) critically depends on the presence of free fatty acids in the small intestine. Postprandial CCK release and gallbladder contraction might be decreased by orlistat, potentially resulting in an increased risk of gallstone formation. In this double-blind, placebo-controlled, six-way crossover study, six healthy volunteers ingested in a randomized order three isocaloric test meals (250 ml) of identical osmolality with either orlistat (200 mg) or placebo: (a) a pure-fat meal (25 g triglycerides), (b) a mixed meal containing fat (8 g; 29% of caloric content), protein (10 g; 17%), and dextrose (32 g; 54%), and (c) a fat-free meal containing albumin (25 g; 46%) and dextrose (32 g; 54%). Gallbladder volumes were determined by ultrasonography, and plasma CCK, pancreatic polypeptide and gastrin levels by RIA. Gall-bladder contraction (AUC, % x 90 min; difference of means +/- 95% CI) in subjects receiving orlistat or placebo did not significantly differ after intake of the pure-fat meal (443+/-1174), the mixed meal (313+/-1170), or the fat-free-meal (-760+/-1180). The release of CCK (AUC; pM x 90 min; difference of means +/- 95% CI) was not different between orlistat and placebo after ingestion of the pure-fat meal (-18+/-64), the mixed meal (-45+/-62), and the fat-free meal (27+/-63). Likewise, the release of pancreatic polypeptide and gastrin was similar after intake of the meals with either orlistat or placebo. A single dose of orlistat did not reduce gallbladder motility after ingestion of meals with differing fat contents. The safety of long-term treatment with orlistat with respect to gallstone formation remains to be determined.