Gastric processing and emptying of fat

Gastrointestinal dysfunction during enteral nutrition delivery in intensive care unit (ICU) patients: Risk factors, natural history, and clinical implications. A post-hoc analysis of The Augmented versus Routine approach to Giving Energy Trial (TARGET)

BACKGROUND

Slow gastric emptying occurs frequently during critical illness and is roughly quantified at bedside by large gastric residual volumes (GRVs). A previously published trial (The Augmented versus Routine approach to Giving Energy Trial; TARGET) reported larger GRVs with energy-dense (1.5 kcal/mL) compared with standard (1.0 kcal/mL) enteral nutrition (EN), warranting further exploration.

OBJECTIVE

To assess the incidence, risk factors, duration, and timing of large GRVs (≥250 mL) and its relation to clinical outcomes in mechanically ventilated adults.

METHODS

A post-hoc analysis of TARGET data in patients with ≥1 GRV recorded. Data are n (%) or median [IQR].

RESULTS

Of 3876 included patients, 1777 (46%) had ≥1 GRV ≥250 mL, which was more common in males (50 compared with 39%; P < 0.001) and in patients receiving energy-dense compared with standard EN (52 compared with 40%; RR = 1.27 (95% CI: 1.19, 1.36); P < 0.001) in whom it also lasted longer (1 [0-2] compared with 0 [0-1] d; P < 0.001), with no difference in time of onset after EN initiation (day 1 [0-2] compared with 1 [0-2]; P = 0.970). Patients with GRV ≥250 mL were more likely to have the following: vasopressor administration (88 compared with 76%; RR = 1.15 [1.12, 1.19]; P < 0.001), positive blood cultures (16 compared with 8%; RR = 1.92 [1.60, 2.31]; P < 0.001), intravenous antimicrobials (88 compared with 81%; RR = 1.09 [1.06, 1.12]; P < 0.001), and prolonged intensive care unit (ICU) stay (ICU-free days to day 28; 12.9 [0.0-21.0] compared with 20.0 [3.9-24.0]; P < 0.001), hospital stay (hospital-free days to day 28: 0.0 [0.0-12.0] compared with 7.0 [0.0-17.6] d; P < 0.001), ventilatory support (ventilator-free days to day 28: 16.0 [0.0-23.0] compared with 22.0 [8.0-25.0]; P < 0.001), and a higher 90-d mortality (29 compared with 23%; adjusted: RR = 1.17 [1.05, 1.30]; P = 0.003).

CONCLUSION

Large GRVs were more common in males and those receiving energy-dense formulae, occurred early and were short-lived, and were associated with a number of negative clinical sequelae, including increased mortality, even when adjusted for illness severity. This trial was registered at clinicaltrials.gov as NCT02306746.

The effects of processing barley and maize on metabolic and digestive responses in horses

The competition for customers increases the search for new grain processing methods for equine feed, but the effect on starch digestibility and metabolic responses varies. Therefore, to evaluate the effect of the processing methods, toasting and micronizing, on starch digestion and the effect on metabolic responses, the mobile bag technique (MBT) and plasma glucose and insulin concentrations in the blood were used to estimate nutrient disappearance and metabolic responses pre-cecally. Further, cecal pH, ammonium nitrogen (N), and short-chain fatty acid (SCFA) concentrations were used to estimate the metabolic response in the cecum. Four cecally cannulated horses (body weight [BW] 565 ± 35 kg) were used in a 4 × 4 Latin square design with four periods of 8 d of diet adaptation and 2 d of data collection. Diets were formulated using hay and processed grains: micronized barley (MB), toasted barley (TB), micronized maize (MM), and toasted maize (TM) and were balanced to provide 1 g starch/kg BW in the morning meal. On day 9 in each period, blood and cecal fluid samples were taken before the morning meal and hourly thereafter for 8 h. On day 10 in each period, 15 bags of either MB, TB, MM, or TM (1 × 1 × 12 cm; 15 μm pore size; 1 g feed) were placed in the stomach, respectively. The dry matter disappearance was highest for the MM at all time points compared with the other feedstuffs (P < 0.001). Maize and micronizing had the highest starch disappearance (P = 0.048) compared with barley and toasting. No treatment effect was measured for any of the glucose and insulin parameters. No feed effect was measured for the insulin parameters. Plasma glucose peaked later (P = 0.045) for maize than for barley, and TB had a larger area under the curve for glucose than MB, MM, and TM (P = 0.015). The concentration of total SCFA increased after feeding (P < 0.001), with a higher concentration for barley than for maize (P = 0.044). No treatment or feed effects were measured for ammonium N or pH, but both were affected by time (P < 0.001). In conclusion, toasting was not as efficient as micronizing to improve pre-cecal starch digestibility; therefore, the preferred processing method for both barley and maize is micronizing. Further, the amount of starch escaping enzymatical digestion in the small intestine was higher than expected.

Measurement of fasted state gastric antral motility before and after a standard bioavailability and bioequivalence 240 mL drink of water: Validation of MRI method against concomitant perfused manometry in healthy participants

Objective

The gastrointestinal environment in which drug products need to disintegrate before the drug can dissolve and be absorbed has not been studied in detail due to limitations, especially invasiveness of existing techniques. Minimal in vivo data is available on undisturbed gastrointestinal motility to improve relevance of predictive dissolution models and in silico tools such as physiologically-based pharmacokinetic models. Recent advances in magnetic resonance imaging methods could provide novel data and insights that can be used as a reference to validate and, if necessary, optimize these models. The conventional method for measuring gastrointestinal motility is via a manometric technique involving intubation. Nevertheless, it is feasible to measure gastrointestinal motility with magnetic resonance imaging. The aim of this study was is to develop and validate a magnetic resonance imaging method using the most recent semi-automated analysis method against concomitant perfused manometry method.

Material and methods

Eighteen healthy fasted participants were recruited for this study. The participants were intubated with a water-perfused manometry catheter. Subsequently, stomach motility was assessed by cine-MRI acquired at intervals, of 3.5min sets, at coronal oblique planes through the abdomen and by simultaneous water perfused manometry, before and after administration of a standard bioavailability / bioequivalence 8 ounces (~240mL) drink of water. The magnetic resonance imaging motility images were analysed using Spatio-Temporal Motility analysis STMM techniques. The area under the curve of the gastric motility contractions was calculated for each set and compared between techniques. The study visit was then repeated one week later.

Results

Data from 15 participants was analysed. There was a good correlation between the MRI antral motility plots area under the curve and corresponding perfused manometry motility area under the curve (r = 0.860) during both antral contractions and quiescence.

Conclusion

Non-invasive dynamic magnetic resonance imaging of gastric antral motility coupled with recently developed, semi-automated magnetic resonance imaging data processing techniques correlated well with simultaneous, ‘gold standard’ water perfused manometry. This will be particularly helpful for research purposes related to oral absorption where the absorption of a drug is highly depending on the underlying gastrointestinal processes such as gastric emptying, gastrointestinal motility and availability of residual fluid volumes.

Clinical trial

This trial was registered at ClinicalTrials.gov as NCT03191045.

Exposure of Human Gastric Cells to Oxidized Lipids Stimulates Pathways of Amino Acid Biosynthesis on a Genomic and Metabolomic Level

The Western diet is characterized by a high consumption of heat-treated fats and oils. During deep-frying processes, vegetable oils are subjected to high temperatures which result in the formation of lipid peroxidation products. Dietary intake of oxidized vegetable oils has been associated with various biological effects, whereas knowledge about the effects of structurally-characterized lipid peroxidation products and their possible absorption into the body is scarce. This study investigates the impact of linoleic acid, one of the most abundant polyunsaturated fatty acids in vegetable oils, and its primary and secondary peroxidation products, 13-HpODE and hexanal, on genomic and metabolomic pathways in human gastric cells (HGT-1) in culture. The genomic and metabolomic approach was preceded by an up-to-six-hour exposure study applying 100 µM of each test compound to the apical compartment in order to quantitate the compounds’ recovery at the basolateral side. Exposure of HGT-1 cells to either 100 µM linoleic acid or 100 µM 13-HpODE resulted in the formation of approximately 1 µM of the corresponding hydroxy fatty acid, 13-HODE, in the basolateral compartment, whereas a mean concentration of 0.20 ± 0.13 µM hexanal was quantitated after an equivalent application of 100 µM hexanal. An integrated genomic and metabolomic pathway analysis revealed an impact of the linoleic acid peroxidation products, 13-HpODE and hexanal, primarily on pathways related to amino acid biosynthesis (p < 0.05), indicating that peroxidation of linoleic acid plays an important role in the regulation of intracellular amino acid biosynthesis.

Effect of dairy calcium from cheese and milk on fecal fat excretion, blood lipids, and appetite in young men

BACKGROUND

Calcium from different dairy sources might affect blood lipids and fecal fat excretion differently because of differences in the food matrix and nutritional composition.

OBJECTIVE

We investigated whether milk- and cheese-based diets with similar calcium contents affect a saturated fatty acid-induced increase in blood lipids differently.

DESIGN

Fifteen healthy, young men participated in a randomized 3 × 2-wk crossover study in which the following 3 isocaloric diets that were similar in fat contents and compositions were compared: control diet [nondairy diet (~500 mg Ca/d)], milk diet [semiskimmed milk-based diet (1700 mg Ca/d)], and cheese diet [semihard cow-cheese-based diet (1700 mg Ca/d)]. Blood was drawn before and after each period, and feces were collected for 5 d during each period.

RESULTS

Saturated fatty acid-induced increases in total and low-density lipoprotein (LDL) cholesterol were lower with the milk diet (mean ± SD: 0.57 ± 0.13 and 0.53 ± 0.11 mmol/L, respectively) (P < 0.01) and cheese diet (0.41 ± 0.15 and 0.47 ± 0.12 mmol/L, respectively) (P < 0.05) than with the control diet (0.89 ± 0.12 and 0.84 ± 0.11 mmol/L, respectively). Fecal fat excretion increased more with the consumption of both the milk (5.2 ± 0.4 g/d) and cheese (5.7 ± 0.4 g/d) diets than with the control diet (3.9 ± 0.3 g/d) (P < 0.001). Changes in blood pressure, high-density lipoprotein cholesterol, triglycerides, and lipid ratios did not differ.

CONCLUSIONS

Compared with the control diet, milk- and cheese-based diets attenuated saturated fatty acid-induced increases in total and LDL cholesterol and resulted in increased fecal fat excretion; however, effects of milk and cheese did not differ. Because the diets contained similar amounts of saturated fat, similar increases in total and LDL cholesterol could be expected; however, both milk and cheese attenuated these responses, which seem to be explained by their calcium contents. This trial was registered at clinicaltrials.gov as NCT01317251.

Dairy calcium intake modifies responsiveness of fat metabolism and blood lipids to a high-fat diet

Intervention studies have demonstrated that saturated fat increases total and LDL-cholesterol concentrations, and it is therefore recommended that the intake of high-fat dairy products be limited. However, observational studies have found an inverse relationship between the intake of dairy products and incidence of CVD. We aimed to study whether the Ca content of dairy products influences the effect of dairy fat on the lipid profile. The study had a randomised cross-over design. Subjects (n 9) were randomised to one of the sequence of four isoenergetic 10 d diets: low Ca and low fat (LC/LF: approximately 700 mg Ca/d, 25 % of energy (fat); high Ca and LF (HC/LF: approximately 2800 mg Ca/d, 25 % of energy fat); LC and high fat (LC/HF: approximately 700 mg Ca/d, 49 E% fat); or HC and HF (approximately 2800 mg Ca/d, 49 E% fat). Blood variables were measured before and after each diet period, and faeces and urine were collected at the end of each diet period. A two-way ANOVA was used to examine the effect of Ca and fat intake. Independent of Ca intake, the HF diet increased the concentrations of total (9 %; P < 0·0001), LDL (14 %; P < 0·0001)- and HDL (13 %; P = 0·0002)-cholesterol compared with the LF diet. However, independent of fat intake, the HC diet decreased the concentrations of total (4 %; P = 0·0051) and LDL-cholesterol (10 %; P < 0·0001) but not HDL-cholesterol compared with the LC diet. In addition, total:HDL-cholesterol was decreased (5 %; P = 0·0299), and HDL:LDL was increased (12 %; P = 0·0097) by the HC diet compared with the LC diet. Faecal fat excretion was increased by both the HC (P < 0·0001) and HF (P = 0·0052) diets. In conclusion, we observed that dairy Ca seems to partly counteract the raising effect of dairy fat on total and LDL-cholesterol, without reducing HDL-cholesterol.

Manipulating digestion with foods designed to change the physical characteristics of digesta

We explore how foods can be designed to modulate digestion and to promote health by changing the physical properties of digesta. The physical characteristics of digesta are discussed along with their impact on the physiology of digestion with special reference to sites where these characteristics are likely to influence digestive efficiency. Evidence is reviewed regarding the effects of supplementation with viscoactive agents on the flow and mixing of digesta in particular segments of the human gut that, by changing the rheology and liquid permeability of digesta in that segment, influence specific aspects of digestion and absorption.

Intragastric layering of lipids delays lipid absorption and increases plasma CCK but has minor effects on gastric emptying and appetite

Intestinal intubation studies have demonstrated that lipids induce satiety, but the contribution of lipid processing by the stomach on satiety remains poorly understood. In this explorative, randomized, placebo-controlled, crossover study we tested whether delayed lipid absorption, increased cholecystokinin (CCK), decelerated gastric emptying (GE), and increased satiety can be achieved by controlling lipid distribution in the stomach. Six healthy men were intubated nasogastrically. Two treatments were performed and repeated in duplicate. In the oil-on-top treatment (OT), subjects received a fat-free liquid meal (LM, 325 ml, 145 kcal) followed by intragastric infusion of 4 g of high-oleic-acid rapeseed oil (4.6 ml, 36 kcal) labeled with 77 mg glyceryl-[(13)C]trioleate. In the emulsion treatment (EM, control), 4 g of labeled rapeseed oil was incorporated into the LM (325 ml, 181 kcal); 4.6 ml of saline was infused as a control. In OT and EM a second LM was consumed at time t = 270 min. Plasma (13)C-C18:1, CCK and satiety were measured over 480 min. GE was determined by the paracetamol absorption test. OT delayed oleic acid absorption shown by an increased lag time of absorption (EM: 37 +/- 7 min; OT: 75 +/- 10 min; P < 0.01) and time at maximum concentration (EM: 162 +/- 18 min; OT: 280 +/- 33 min; P = 0.01). OT released more CCK than EM (P = 0.03), including increased CCK after the second meal. OT accelerated initial GE until 30 min postprandial. OT showed a tendency (P = 0.06) to suppress hunger and increase satiety and fullness 120-270 min postprandially. The results demonstrate that low amounts of lipids, when separated from the aqueous phase of a meal, delay lipid absorption and increase CCK. An escalating-dose study should determine whether this could have implications for the development of weight-control foods.

Different effects of whole milk and a fermented milk with the same fat and lactose content on gastric emptying and postprandial lipaemia, but not on glycaemic response and appetite

Longitudinal studies indicate that milk and fermented milk products lower basal plasma cholesterol concentrations, despite their high content of saturated fat, and therefore have favourable health effects. However, there have been few studies on the postprandial effects of milk products. The present study compared the effect of whole milk with a fermented milk, A-38, on postprandial carbohydrate and lipid metabolism, gastric emptying and appetite. Eight healthy young men participated. On the two test days, they arrived fasting for collection of baseline values before consuming the meals, which for a 75 kg subject consisted of 1·4 litre milk or fermented milk, plus 165 mg [13C]acetate (for later determination of gastric emptying by a [13C]acetate breath test). Lactose (15 g) was added to the A-38 meal to equalize the lactose content. Postprandially the A-38 meal resulted in a slower gastric emptying rate than milk (P>0·001). Furthermore, the A-38 meal resulted in a greater increase and a quicker decrease of the triacylglycerol content in all lipoprotein fractions (LDL-fraction,P>0·05; other fractions,P>0·001) and of the gastrointestinal hormones (cholecystokinin and peptide YY,P>0·05; gastric inhibitory polypeptide and glucagon-like polypeptide-1,P>0·001). There were no significant differences in appetite sensations (measured by visual analogue scale) or in the glucose and insulin response (P<0·10). The slower emptying rate of the liquid phase after the A-38 meal is probably due to the higher viscosity of A-38. The lower and more prolonged triacylglycerol response after the milk meal might be caused by coagulation of milk in the stomach.

Effects of fat on gastric emptying of and the glycemic, insulin, and incretin responses to a carbohydrate meal in type 2 diabetes

CONTEXT

Gastric emptying (GE) is a major determinant of postprandial glycemia. Because the presence of fat in the small intestine inhibits GE, ingestion of fat may attenuate the glycemic response to carbohydrate.

OBJECTIVE

The objective of this study was to evaluate the effect of patterns of fat consumption on GE and glucose, insulin, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) concentrations after a carbohydrate meal in type 2 diabetes.

DESIGN

This was a randomized, cross-over study in which GE of a radioisotopically labeled potato meal was measured on 3 d.

SETTING

The study was performed at the Royal Adelaide Hospital.

PATIENTS

Six males with type 2 diabetes were studied.

INTERVENTION

Subjects ingested 1) 30 ml water 30 min before the mashed potato (water), 2) 30 ml olive oil 30 min before the mashed potato (oil), or 3) 30 ml water 30 min before the mashed potato meal that contained 30 ml olive oil (water and oil).

MAIN OUTCOME MEASURES

GE, blood glucose, plasma insulin, GLP-1, and GIP concentrations were the main outcome measures.

RESULTS

GE was much slower with oil compared with both water (P < 0.0001) and water and oil (P < 0.05) and was slower after water and oil compared with water (P < 0.01). The postprandial rise in blood glucose was markedly delayed (P = 0.03), and peak glucose occurred later (P = 0.04) with oil compared with the two other meals. The rises in insulin and GIP were attenuated (P < 0.0001), whereas the GLP-1 response was greater (P = 0.0001), after oil.

CONCLUSIONS

Ingestion of fat before a carbohydrate meal markedly slows GE and attenuates the postprandial rises in glucose, insulin, and GIP, but stimulates GLP-1, in type 2 diabetes.

Imaging and modelling of digestion in the stomach and the duodenum

Gastroduodenal physiology is traditionally understood in terms of motor-secretory functions and their electrical, neural and hormonal controls. In contrast, the fluid-mechanical functions that retain and disperse particles, expose substrate to enzymes, or replenish the epithelial boundary with nutrients are little studied. Current ultrasound and magnetic resonance imaging allows to visualize processes critical to digestion like mixing, dilution, swelling, dispersion and elution. Methodological advances in fluid mechanics allow to numerically analyse the forces promoting digestion. Pressure and flow fields, the shear stresses dispersing particles or the effectiveness of bolus mixing can be computed using information on boundary movements and on the luminal contents. These technological advances promise many additional insights into the mechanical processes that promote digestion and absorption.

The supramolecular structure of milk fat influences plasma triacylglycerols and fatty acid profile in the rat

BACKGROUND

The digestion fate of milk fat depending on its supramolecular structure for a given dairy product composition has rarely been studied.

AIM OF THE STUDY

To highlight differences of lipid digestion, we measured (i) the plasma triacylglycerol and cholesterol concentrations and (ii) the total plasma fatty acid profile of fasted rats force-fed with different dairy preparations; the three creams and the unemulsified preparation had a similar composition with different and controlled fat suprastructures.

METHODS

All preparations, manufactured in the laboratory from a given milk batch, contained 205 +/- 3 g . kg(-1) fat that was either fed (i) unemulsified consecutively to the skim milk phase, or as a cream with the following fat globule structures: (ii) native milk fat globules of approximately 4 microm covered with the native milk fat globule membrane (MFGM), (iii) small native milk fat globules of approximately 2 microm selected from the latter by microfiltration and covered by the MFGM, or (iv) fine homogenized fat droplets of approximately 1 microm covered mainly with caseins.

RESULTS

The plasma triacylglycerol appearance was delayed for the creams compared with the rapid onset for the unemulsified preparation. At 90 and 180 min after feeding, the plasma triacylglycerol enrichment was significantly lower for the homogenized cream than for the unemulsified preparation. At 120 min after feeding, triacylglycerol enrichment was significantly lower for each cream than for the unemulsified preparation. At 180 min after feeding, the plasma relative enrichment in C12, C14, C15, C16 and C18:1 n-9 fatty acids was significantly lower for the homogenized cream than for unemulsified fat and regular cream.

CONCLUSIONS

Global lipid digestion based on plasma triacylglycerol enrichment and relative enrichments in some fatty acids was decreased with small homogenized milk fat droplets compared to unemulsified milk fat. These data show that dairy products with the same composition but varying in fat supramolecular structure result in different kinetics of lipid digestion, which could be of health concern.

The metabolism of structured triacylglycerols

The triacylglycerol (TAG) structure in addition to the overall fatty acid profile is of importance when considering the nutritional effect of a dietary fat. This review aims at summarizing our current knowledge of the digestion, absorption, uptake, and transport of structured TAGs, with particular emphasis on the following aspects: gastric emptying, specificity of pancreatic lipase, lymphatic transport and clearance of chylomicrons, effects of lipid structure on tissue lipid compositions and the fecal loss of fats. So an overview will be provided for how the structure and fatty acid composition of TAGs affect their absorption and the distribution of the fatty acids in the body following digestion and absorption.

Meal-induced gastric relaxation and emptying in horses after ingestion of high-fat versus high-carbohydrate diets

OBJECTIVE

To evaluate the effect of ingestion of a high-carbohydrate versus a high-fat meal on relaxation of the proximal portion of the stomach and subsequent gastric emptying in horses.

ANIMALS

6 healthy adult horses.

PROCEDURE

The study consisted of 2 phases. In phase I, horses were offered a high-fat (8% fat) or a high-carbohydrate (3% fat) pelleted meal (0.5 g/kg) of identical volume, caloric density, and protein content. In phase II, meals consisted of a commercial sweet feed meal (0.5 g/kg) or this meal supplemented with corn oil (12.3% fat) or an isocaloric amount of glucose (2.9% fat). Proximal gastric tone was measured by variations in volume of an intragastric bag introduced through a gastric cannula and maintained with a constant internal pressure by an electronic barostat. Rate of gastric emptying was measured simultaneously with the 13C-octanoic acid breath test. Interaction between both techniques was studied in additional experiments.

RESULTS

Meals with higher carbohydrate content induced a significantly more prolonged receptive relaxation of the proximal portion of the stomach than those with higher fat content, but the accommodation response was similar. Labeling the meals with the breath test marker influenced the accommodation response measured by the barostat. Gastric emptying rates were not significantly different between meals, although those high in carbohydrate initially emptied more slowly.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses, in contrast to most species, dietary fat supplementation may not have a profound effect on gastric motility.

The dispersion state of milk fat influences triglyceride metabolism in the rat

BACKGROUND

Milk fat, which has different structures in the various dairy products, is a major and controversial lipid source in the Western diet. However, information about the digestion fate of milk fat depending on its supramolecular structure for a given composition is scarce.

AIM OF THE STUDY

In this study, 13CO2 breath tests were performed with fasted rats force-fed different dairy preparations of similar composition but differing in fat suprastructure in order to highlight differences of general lipid metabolism.

METHODS

Each preparation consisted of a NaCl solution, anhydrous milk fat labelled with a 13C mixed triacylglycerol, casein (as native phosphocaseinate powder with some lactose), and dipalmitoylphosphatidylcholine. Milk fat was either fed (i) unemulsified consecutively to the aqueous phase, or emulsified as (ii) coarse droplets of approximately 10 microm covered mainly with the phospholipid, or (iii-iv) fine droplets of approximately 1 microm covered mainly with casein, force-fed either in the liquid state or in a semi-crystallized state. 13C abundance in expired air samples was measured by isotope ratio mass spectrometry; results were expressed as 13C enrichment and were submitted to an ANOVA analysis.

RESULTS

The 13CO2 excretion curves of the unemulsified preparation and the coarse emulsion were similar and presented a sharp peak, both significantly different from the fine emulsion curves characterized by a nearly linear cumulative recovery. The crystalline state of the fine emulsion droplets and the viscosity of these emulsions did not affect significantly their excretion curves. The lipid metabolization (indicated by the 13C recovery) was significantly slower for the fine droplets coated with casein than for the large droplets coated with the phospholipid and the unemulsified fat. For the latter, a single 13C peak rapidly appeared, while for small droplets coated with caseins, 13C excretion was continuous up to 6 h.

CONCLUSIONS

Global lipid metabolism based on oxidation to CO2 was decreased with smaller compared to larger emulsified milk fat particles with different coatings. These data support the concept that dairy products with different fat suprastructures are digested and metabolized differently.

Gastric function in children with cystic fibrosis: effect of diet on gastric lipase levels and fat digestion

The effect of diet, usual (44 +/- 4% energy as fat), high-fat (49 +/- 4% energy as fat), and moderate-fat (33 +/- 2% energy as fat), on gastric function (lipase and pepsin activities, pH, emptying rate) and intragastric digestion of fat were assessed in six children with cystic fibrosis. Fasting and postprandial activity of digestive enzymes, gastric pH, and gastric volume measured before, during, and after 120 min of feeding did not differ significantly as a function of fat intake. Postprandial gastric lipase output (units per kilogram of body weight) during usual, moderate-fat, and high-fat diets was close to or higher than (38.8 +/- 7.2, 44.9 +/- 8.6, and 54.8 +/- 5.5 U/kg per 20 min) gastric lipase output of premature infants (22.5 +/- 6.4 to 28.3 +/- 6.6 U/kg per 20 min) or of healthy adults (5.4 +/- 0.4 U/kg per 15 min) fed a high-fat diet. Postprandial pepsin output was higher (4749 +/- 797, 6117 +/- 925, and 5444 +/- 819 U/kg per 20 min) than in premature infants (597 +/- 77 to 743 +/- 97 U/kg per 20 min) or healthy adults (781 +/- 56 U/kg per 15 min). Eighty minutes after feeding gastric lipolysis reached 20 to 36%. This study shows that gastric lipase activity is high in cystic fibrosis patients maintained on diets providing 32% to 49% energy as fat, and that gastric lipase level did not increase over the ranges of dietary fat intake tested.

Digestion and absorption of 2 fat emulsions with different droplet sizes in the human digestive tract

BACKGROUND

The extent of fat emulsification affects the activity of digestive lipases in vitro and may govern digestion and absorption of dietary fat.

OBJECTIVE

We investigated the effect of the fat globule size of 2 enteral emulsions on fat digestion and assimilation in humans.

DESIGN

Healthy subjects received intragastrically a coarse (10 microm) and a fine (0.7 microm) lipid emulsion of identical composition in random order. Gastric and duodenal aspirates were collected throughout digestion to measure changes in fat droplet size, gastric and pancreatic lipase activities, and fat digestion. Blood lipids were measured postprandially for fat assimilation.

RESULTS

Despite an increase in droplet size in the stomach (2.75-6.20 microm), the fine emulsion retained droplets of smaller size and its lipolysis was greater than that of the coarse emulsion (36.5% compared with 15.8%; P < 0.05). In the duodenum, lipolysis of the fine emulsion was on the whole higher (73.3% compared with 46.3%). The overall 0-7-h plasma and chylomicron responses given by the areas under the curve were not significantly different between the emulsions, but the triacylglycerol peak was delayed with the fine emulsion (3 h 56 min compared with 2 h 50 min).

CONCLUSIONS

Fat emulsions behave differently in the digestive tract depending on their initial physicochemical properties. A lower initial fat droplet size facilitates fat digestion by gastric lipase in the stomach and duodenal lipolysis. Overall fat assimilation in healthy subjects is not affected by differences in initial droplet size because of efficient fat digestion by pancreatic lipase in the small intestine. Nevertheless, these new observations could be of interest in the enteral nutrition of subjects suffering from pancreatic insufficiency.

Net postprandial utilization of [15N]-labeled milk protein nitrogen is influenced by diet composition in humans

The aim of this study was to follow the fate of dietary nitrogen to assess the postprandial utilization of purified milk protein and to determine the acute influence of energy nutrients. For this purpose, a [15N]-labeling dietary protein approach was used. Twenty-five subjects swallowed an ileal tube and ingested [15 N]-milk protein alone or supplemented with either milk fat or sucrose. The absorption and postprandial deamination of dietary protein was monitored for 8 h. Sucrose delayed the absorption of protein longer than fat, but the ileal digestibility did not differ among groups (94.5-94.8%). Sucrose, but not fat, significantly reduced the postprandial transfer of [15N]-milk nitrogen to urea. Consequently, the net postprandial protein utilization (NPPU) of milk protein calculated 8 h after meal ingestion was 80% when ingested either alone or supplemented with fat and was significantly greater with sucrose (NPPU = 85%). This study shows that energy nutrients do not affect the nitrogen absorption but modify the metabolic utilization of dietary protein in the phase of nitrogen gain. Our method provides information concerning the deamination kinetics of dietary amino acids and further allows the detection of differences of dietary protein utilization in acute conditions. The diet composition should be carefully considered, and protein quality must be determined under optimal conditions of utilization.

Gastric emptying of the liquid, solid and oil phase of a meal in normal volunteers and patients with Billroth II gastrojejunostomy

BACKGROUND

The relationship between gastric emptying of different phases of a meal in humans has only been partly studied in normal subjects and in patients with previous gastric surgery.

METHODS

In the present study, gastric emptying of the liquid, solid and oil phase and the relationship between the phases was evaluated in 10 normal control subjects and in seven patients with Billroth II gastrojejunostomy using breath test technology.

RESULTS

Gastric emptying in normal subjects showed a clear separation between the emptying of the liquid, solid and oil phase. In healthy volunteers, the liquid phase emptied in the same manner in the presence of a solid phase as in the presence of an oil phase. In contrast, the oil phase emptied more slowly with liquids than with solids. The emptying rate of the oil phase was not only inversely related to the amount administered but was also dependent on its chemical composition. Gastric emptying in patients with Billroth II gastroenterostomy was characterized by a complete loss of discrimination between the different phases of the meal, with an extremely fast emptying of the oil phase compared with normal control subjects.

CONCLUSION

In normal subjects, the liquid, solid and oil phase of a meal are emptied differently. In patients with Billroth II gastrojejunostomy, dumping of the oil phase is the most pronounced difference from the normal physiology of gastric emptying. This could be one of the reasons why Billroth II gastrectomy may be associated with fat malabsorption.

Gastric emptying of oil from solid and liquid meals. Effect of human pancreatic insufficiency

Digestion of fat in pancreatic insufficiency (PI) is strongly affected by how rapidly fat enters the duodenum. We postulated that: (1) oil empties faster in PI than in normals and (2) in both, it empties in a load-dependent fashion. We used a gamma camera to test these ideas by comparing gastric emptying of iodine-123 iodinated oil in normal and pancreatic-insufficient subjects after 15 g of free oil were ingested in a small spaghetti meal and 60 g of oil were ingested in a large spaghetti meal and in a milk emulsion. Indium-113m marked gastric emptying of water in the milk. In both groups after all meals, oil emptied fastest initially, slowing later; and oil emptied three to four times faster when 60 g vs 15 g were ingested. There were no significant differences between the groups of subjects with respect to gastric emptying of the spaghetti meals, but the pancreatic-insufficient subjects emptied both oil and water faster from the milk emulsion than did the normal subjects. The slower emptying of oil in the normal subjects was associated with significantly more layering of oil to the top of the intragastric milk emulsion.

Comparison of the inhibition of dietary fat absorption by full versus divided doses of orlistat

Orlistat is a potent and selective inhibitor of gastrointestinal lipases. The drug is designed for the treatment of obesity. The effect on dietary fat absorption of orlistat after administration of divided doses spread over 2 hours from mid-meal, in comparison with that after administration of a full dose mid-meal, was investigated in a randomized, single-blind study including 16 hospitalized healthy males. After a 5-day run-in, to accustom the subjects to a diet of 2350 kcal and 76 g fat per day and to establish baseline fecal fat excretion, subjects received, in two parallel groups of eight over 8 days, three times a day 80 mg orlistat at mid-meal, and placebo at mid-meal and 0.5, 1, and 2 hr after mid-meal (group A), or placebo at mid-meal, and 20 mg orlistat at mid-meal and 0.5, 1, and 2 hr after mid-meal (group B). Feces were collected to measure total fat excretion. The mean (SD) of fecal fat in percent of dietary fat, after deduction of pretreatment fecal fat, was (%) 36.1 (4.2) and 37.0 (9.3) in groups A and B, respectively. Changing the mode of administration of orlistat, within the dose regimens investigated, does not affect its pharmacologic efficacy.

Stereospecific effects of tryptophan on gastric emptying and hunger in humans

The amino acid tryptophan (tryp) is a potent inhibitor of gastric emptying in both animals and humans. Animal studies suggest that this effect may be specific for the L-enantiomer. The effects of D- and L-tryptophan on gastric emptying, intragastric distribution and appetite in humans were evaluated. Ten volunteers ingested 300 mL of either L-tryp (50 mmol/L), D-tryp (50 mmol/L) or normal saline labelled with 99mTc sulfur colloid on three occasions, separated by between 3 and 7 days. Hunger and fullness were measured with a visual analogue scale at -2, 15, 30 and 60 min after ingestion of each drink. Saline emptied faster from the stomach than both L-tryp and D-tryp (P < 0.05) and D-tryp emptied faster than L-tryp (P < 0.005). Emptying from the proximal stomach was fastest for saline (P < 0.05) and faster for D-tryp than L-tryp (P < 0.005). Emptying from the distal stomach was faster for saline than both D- and L-tryp (P < 0.05). A reduction in hunger (P < 0.05) and a non-significant trend for an increase in fullness were observed after all three drinks. At 60 min, fullness was greater after L-tryp than after ingestion of D-tryp (P < 0.01). These observations indicate that the effect of tryptophan on gastric emptying in humans is stereospecific, consistent with the concept that stereospecific receptors for tryptophan exist in the human small intestine.

Influence of dietary composition on the inhibition of fat absorption by orlistat

Orlistat, a potent and selective inhibitor of gastrointestinal lipases, is designed for the treatment of obesity. The effect of orlistat on dietary fat absorption, when it was administered with diets differing in fibre content (high and low) and accessibility of fat (intra- and extracellular fat), was investigated in 32 hospitalized healthy males, according to an open, two-factorial study design. The subjects were randomly allocated to one of four parallel groups of equal size: A = intracellular fat, high fibre (28 g/day); B = extracellular fat, high fibre; C = extracellular fat, low fibre (9 g/day); or D = intracellular fat, low fibre. After a 5-day run-in period to accustom the volunteers to the standardized diet (2500 kcal and 84 g fat per day) and to establish baseline faecal fat parameters, they received 80 mg orlistat, three times daily mid-way through each meal for 8 days. Faeces were collected to measure total fat and free fatty acid excretions. The mean baseline-corrected excretion (% of dietary fat) in groups A, B, C and D, respectively, was 37.0, 30.4, 30.3 and 34.5 for total fat, and 6.5, 4.3, 2.6 and 3.9 for free fatty acids. The 95% confidence intervals for the difference between the means for high fibre and low fibre groups and for intracellular fat and extracellular fat groups, respectively, were 1.4 +/- 4.9 and 5.5 +/- 4.9 for total fat, and 2.2 +/- 3.1 and 1.9 +/- 3.1 for free fatty acids. The statistically significant difference (P < 0.05) in total faecal fat between intracellular fat and extracellular fat groups, in absolute terms < 5 g fat/day, was not regarded as clinically relevant. Under the conditions of this study, dietary fibre content and accessibility of fat had no relevant effect on the inhibition of fat absorption by orlistat.

Secretion and contribution to lipolysis of gastric and pancreatic lipases during a test meal in humans

BACKGROUND

The aim of this study was to quantitatively evaluate the relative contributions to in vivo lipolysis of gastric and pancreatic lipases.

METHODS

Gastric and pancreatic lipase secretions were measured, and their respective levels were determined in duodenal fluid during the digestion of a liquid test meal in healthy volunteers. Gastric lipase activity was clearly distinguished from that of pancreatic lipase by using both a specific enzymatic assay and an enzyme-linked immunosorbent assay. Lipolysis products were monitored throughout the digestion period.

RESULTS

On a weight basis, the ratio of pancreatic lipase to gastric lipase total secretory outputs was found to be around four after 3 hours of digestion. The level of gastric hydrolysis was calculated to be 10% +/- 1% of the acyl chains released from the meal triglycerides. Gastric lipase remained active in the duodenum where it might still hydrolyze 7.5% of the triglyceride acyl chains.

CONCLUSIONS

Globally during the whole digestion period, gastric lipase might hydrolyze 17.5% of the triglyceride acyl chains. In other words, gastric lipase might hydrolyze 1 acyl chain of 4, which need to be hydrolyzed for a complete intestinal absorption of monoglycerides and free fatty acids resulting from the degradation of two triglyceride molecules.

Effect on dietary fat absorption of orlistat, administered at different times relative to meal intake

Orlistat (O) is a potent and selective inhibitor of gastrointestinal lipases. The effect on dietary fat absorption following dosing of O at different times relative to meals was investigated in a placebo (P) controlled study in 24 hospitalized healthy males. After a 5-day run-in, to accustom the subjects to a diet of 2400 kcal and 77 g fat per day and to establish baseline faecal fat excretion, subjects received, in four parallel groups of 6. over 8 days three times daily doses of 80 mg O.P.P (group A) or P. 80 mg O.P (group B) or P.P. 80 mg O (group C) or P.P.P (group D) at mid-meal. 1 h and 2 h after mid-meal respectively. Faeces were collected to measure total fat excretion. The mean (s.d.) of faecal fat in percent of dietary fat, after deduction of pre-treatment faecal fat, was (%) 32.8 (8.1), 34.0 (8.8), 26.9 (4.0) and -1.4 (1.7) in groups A. B. C and D respectively. It was concluded that, within the time period investigated, the pharmacological effect of O is not critically dependent on the time of dosing relative to meals.

The effect of posture on gastric emptying and intragastric distribution of oil and aqueous meal components and appetite

BACKGROUND

It is uncertain whether gastric emptying of fat is determined mainly by its physical characteristics or chemical composition. In particular, the intragastric distribution of extracellular fat and the importance of that distribution to gastric emptying of fat is controversial. The effects of posture on gastric emptying, intragastric distribution, and appetite after ingestion of a meal containing oil and aqueous phases was evaluated.

METHODS

Eleven volunteers consumed 60 mL 99mTc-(V)-thiocyanate-labeled olive oil and 290 mL 113mIn-labeled soup while sitting and while lying in the left lateral decubitus position. Hunger before and after the meal was recorded.

RESULTS

In the sitting position, oil emptied from the stomach more slowly (P < 0.01) whereas in the decubitus position oil emptied faster (P < 0.01) than the aqueous phase. Oil was preferentially retained in the proximal stomach when sitting (P < 0.01), and more oil was retained in the distal stomach in the decubitus position (P < 0.05). The amount of oil that emptied in the first 180 minutes was not different between the two postures. The aqueous phase emptied much more slowly (P < 0.01) in the decubitus position. At 120 minutes and 180 minutes, subjects were less hungry (P < 0.05) in the decubitus position. In the decubitus position, hunger at 120 minutes and 180 minutes was related to the retention of oil (r > or = 0.79; P < 0.01) in the stomach.

CONCLUSIONS

These results indicate that (1) gravity has a major effect on the intragastric distribution and relatively little effect on total stomach emptying of oil, and (2) postprandial hunger is affected by posture and, in the decubitus position, is inversely related to the amount of oil that has entered the small intestine.

Analysis of segmental phosphate absorption in intact rats. A compartmental analysis approach

Available information supports the dominance of the proximal intestine in inorganic phosphate (Pi) absorption. However, there is no strategy for analyzing segmental Pi absorption from a spontaneously propelled meal in an intact animal. We propose a solution using compartmental analysis. After intragastric administration of a 32P-labeled Pi liquid meal containing a nonabsorbable marker, [14C]polyethylene glycol (PEG), rats were killed at 2, 10, 20, 30, 60, 120, and 240 min. The gastrointestinal tract was removed and divided into seven segments, from which 32P and [14C]PEG were recovered. Data was expressed as a percentage of the dose fed, i.e., (32P[in segment] divided by 32P[fed]) and [14C]PEG[in segment] divided by [14C]PEG[fed]), respectively. A compartmental model was constructed and the rate constants for intersegmental transit and segmental absorption were estimated. The "goodness of fit" between the simulated model and the actual data indicates the estimated rate constants reflect in vivo events. The duodenum, with the highest transit and absorption rates, accounted for a third of the total absorption. However, the terminal ileum, with a lower absorption rate but a longer transit time, absorbed an equal amount of Pi. This approach allows the analysis of the mechanism and the regulation of Pi absorption under more authentic in vivo conditions.

Measurement of gastric emptying by magnetic resonance imaging in humans

A new noninvasive radiation-free method to measure gastric emptying in humans was developed. The upper abdomen was recorded with a magnetic resonance imager after administration of a liquid meal containing Gadolinium tetraazacyclododecane tetraacetic acid as a magnetic resonance image (MRI) marker. Meal volumes, total gastric volumes, and secretory rates were measured. The MRI technique was validated simultaneously by the double indicator method in 5 healthy volunteers and in 5 patients with symptoms of disordered gastric emptying applying gamma camera scintigraphy and MRI in randomized order. Similar gastric meal emptying curves were obtained in volunteers and in patients by MRI and the reference methods as assessed by linear (r greater than 0.90; P less than 0.001) and intraclass correlation analysis (r greater than 0.905) for T1/2, areas under the curve, and percent of gastric meal retained. Furthermore, similar total gastric volumes and gastric secretory rates were measured by MRI and the double indicator technique. The new MRI method correctly reflected gastric emptying disorders in patients. Thus for the first time it is possible to combine these measurements of gastric functions in a single method and to relate them to gastric morphology visualized by the generation of three-dimensional images.

Protein digestibility in dog. Effect of the quantity and quality of dietary fat (virgin olive oil and sunflower oil)

Protein digestibility has been estimated in dog when fed on two similar diets except their lipid quality (virgin olive oil and sunflower oil) from weaning up to 6 months of life. Experiments were carried out at 60, 105 and 150 days of adaptation to either diet. In dog, age does not seem to affect the protein digestive and metabolic utilization when fed on a high lipid content diet. A higher dietary fat percentage led to an increase of the mentioned parameters which could be caused to a delayed gastric emptying due to fat. As far as the fat quality is concerned, an improved protein digestive and metabolic utilization was evidenced in adult animals fed on olive oil. On the other hand, the weight progress was normal in both experimental groups. These results suggest that olive oil may have beneficial effects on protein digestibility as compared to sunflower oil.

Effect of ingested carbohydrate, fat, and protein on the release of somatostatin-28 in humans

The level of somatostatin-28, a bioactive peptide derived from pro-somatostatin in gastrointestinal epithelial cells, increases in human plasma after food intake. To determine if an equivalent response occurs with individual components of a mixed meal, somatostatin-28 and prosomatostatin, somatostatin-14, and somatostatin-13, in combination, were measured in healthy men before and after intake of (a) a mixed meal (715 kcal), (b) carbohydrate (100 g equivalent glucose), (c) protein (22 and 45 g), and (d) fat (25 and 50 g). After the mixed meal, somatostatin-28 levels doubled within 120 min and gradually declined by 4 h. With carbohydrate, somatostatin-28 levels were unaltered. After 22 and 45 g of protein, somatostatin-28 increased equivalently within 60 min, representing 30% of the amount with the mixed meal. With 25 g fat, a somatostatin-28 increase similar to that with the meal was seen; this response was doubled with 50 g fat. No changes in prosomatostatin, somatostatin-14, or somatostatin-13 were observed with the mixed meal or with the separate macronutrients. The authors conclude that fat is the major stimulus for somatostatin-28 secretion in humans and hypothesize that somatostatin-28 is an inhibitor of the endocrine and exocrine pancreas during nutrient absorption.

Intestinal diamine oxidases and enteral-induced histaminosis: studies on three prognostic variables in an epidemiological model

The danger of luminal histamine administered orally or formed in the intestinal fluid by bacteria has long been neglected. However, the demonstration of blocking intestinal diamine oxidase (DAO) by a variety of common drugs has revived the discussion and has created a new disease concept: enteral-induced histaminosis. In an animal model the three central prognostic variables of this disease concept (large amounts of histamine in food to make the individual ill, blocking of DAO by commonly used drugs, and the relationship between increased plasma histamine levels and disease manifestation by exogenous histamine application) were tested with randomized trials in vivo and biochemical tests in vitro using semipurified enzymes from pig and man. In the first trials authentic histamine in quantities similar to that in normal amounts of food or cheese bought from a supermarket produced life-threatening reactions if the DAO was inhibited by pretreatment with aminoguanidine. In the second series of experiments in vitro a numerous commonly used drugs was shown to inhibit both the porcine and human enzyme. Some of the inhibitors were really strong, such as dihydralazine, chloroquine, pentamidine, cycloserine, clavulanic acid, dobutamine, pancuronium and others. The type of inhibition was sometimes competitive as in the case of dihydralazine and pancuronium, sometimes non competitive (e.g. pentamidine) which may be important for long-term treatment. In the third group of experiments a relationship between the dose of i.v. injected histamine and the elevation in plasma histamine levels and clinical symptoms in pigs was demonstrated. Hence, elevated plasma histamine in pigs acts as a pathogenetic factor for the disease manifestation. It is concluded that after modelling enteral-induced histaminosis in an animal the trias of variables shown in this study should be consequently investigated in man.

GIP and insulin release in relation to gastric emptying of a mixed meal in man

To clarify the role of GIP (gastric inhibitory polypeptide) as an incretin, we related temporally the gastric emptying of fat, protein and glucose to plasma levels of glucose, GIP and insulin in man. Five healthy volunteers with a multiple lumen duodenal tube ingested a mixed meal with phase-specific markers for the aqueous phase, liquid fat and the solid protein phase. Duodenal passage was determined by intraduodenal infusion of a second set of phase-specific non-absorbable markers. Plasma insulin rose rapidly from a basal value of 59 pM to 300 pM at 60 min, and then declined to reach basal levels after 180 min. By contrast, plasma GIP rose more slowly than insulin, from a basal value of 9.4 pM, and remained elevated, in the range of 14-18 pM, throughout the 240 min observation period. The time course of plasma insulin concentration paralleled gastric emptying of the aqueous phase, containing most of the meal's glucose (r = 0.952, P less than 0.001). The time course of plasma GIP concentrations paralleled the gastric emptying of fat and protein (r = 0.763-0.834; P less than 0.01-0.05). Plasma insulin concentrations showed no correlation to the rate of emptying of fat and protein (r = 0.142-0.420; n.s.) and to plasma levels of GIP (r = 0.365; n.s.). The threshold for plasma glucose at which GIP would exert an incretin effect only reached at one time point, 30 min after ingestion of the meal. Our findings of simultaneously tracked gastric emptying of meal nutrients, hormone release and plasma glucose levels do not support an important physiological role for GIP as an insulinotropic hormone after ingestion of mixed meals in man.

Gastrointestinal transit of a solid indigestible capsule as measured by radiotelemetry and dual gamma scintigraphy

The objectives of the present study were to evaluate gastric and small bowel transit times of an indigestible solid matrix and to characterize the specific changes in intraluminal pH as a function of transit time through the gastrointestinal tract. Particular attention was paid to the lag time at the ileocecal junction. A Heidelberg capsule (HC), labeled with 10 microCi Indium-111, was given orally to six healthy male subjects 15 min after oral ingestion of 100 microCi of 99mTc-sulfur colloid as a liquid fatty meal (4 ml/kg). Intraluminal pH was monitored continuously via the HC. Gastric and small bowel transit of the radionuclides was monitored via external scintigraphy at 0.5-hr intervals. Gastric residence times (GRT) of the HC ranged from 2.8 to 4.8 hr. with a mean (+/- SD) of 3.6 +/- 0.8 hr. These values were independent of the individual's weight, height, or body surface area. Small bowel transit times of the HC ranged from 2.8 to greater than 5.5 hr. which were consistent with the reported values of 3 to 5 hr. The lag times of the HC at ileocecal junction ranged from 0.8 to greater than 2.5 hr. The presence of the lag times at the ileocecal junction in all subjects confirmed that it acts as a valve or sphincter. Mouth-to-cecum transit times of the HC occurred within 9.0 hr in 50% of the subjects. In general, following a sharp rise upon pyloric passage of HC the pH dropped slightly but then increased linearly throughout the small intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

Fat and pancreatic secretion

In 10 healthy volunteers we investigated the effects of intraduodenal oleic acid at various concentrations (0-40 mM) and at various degrees of emulsification on pancreaticobiliary secretion and the release of secretin and cholecystokinin (CCK) into plasma. We found that the release of the two hormones was directly related to the dose of fat and to the degree of emulsification. The threshold of CCK release (and amylase output) was low in comparison with the threshold for secretin release (and bicarbonate or volume output). When the degree of emulsification of the fat was increased, no simple relation was observed between hormone levels and pancreatic exocrine secretion. The output of bile salts was identical at various fat concentrations. We conclude that both secretin and CCK are dose-dependently released by emulsions of oleic acid in normal man and that the thresholds for release are probably different.

The effect of bile diversion on satiety and fat absorption from liquid and solid dietary sources

In previous studies, liquid fat has been used to determine the effect of bile diversion on fat absorption. Since protein digests, in addition to bile salts, are capable of solubilizing lipids, we hypothesized that fat incorporated in the protein-rich matrix of solid food would be less sensitive to bile diversion than fat ingested as an oil or liquid. Using [3H]glycerol triether as a nonabsorbable fat recovery marker, we determined how much [14C]triolein was absorbed from solid (chicken liver) and liquid (margarine) dietary sources. After a standard liquid/solid meal with either the chicken liver or margarine labeled, midintestinal chyme was collected for 6 hr, extracted, and counted for 14C and 3H activity. Zero, eighty, or one hundred percent of endogenous bile was diverted. Fat absorption from both chicken liver and margarine was nearly complete by midintestine with 0% diversion and was little affected by diversion of 80% of bile. Complete biliary diversion significantly decreased fat absorption from margarine (87.9 +/- 4.4 to 37.2 +/- 9.2%, P less than 0.05) but reduced [14C]triolein absorption from chicken liver less consistently and insignificantly (78.8 +/- 6.9 to 43.9 +/- 10.6%). These data indicate that fat absorption is not solely dependent on bile and support the hypothesis that fat ingested in a cellular matrix is less dependent on bile than liquid fat. Using these same animals but with the midintestinal cannulas plugged to expose the distal intestine to unabsorbed luminal nutrients, we also demonstrated that bile diversion of an initial meal reduced food consumption at a meal offered 3 hr later.

Temporal relationships of cholecystokinin release, pancreatobiliary secretion, and gastric emptying of a mixed meal

The influence of gastric emptying of nutrients on plasma cholecystokinin and pancreatobiliary functions is poorly understood. We therefore temporally related the emptying of fat, protein, and glucose of a mixed meal to release of the gut hormones cholecystokinin, pancreatic polypeptide, and peptide YY and outputs of trypsin, lipase, bilirubin, and bile salts. Five healthy volunteers with a multilumen duodenal tube ingested a mixed meal with phase-specific markers for the aqueous phase, liquid fat, solid fat, and solid protein phases. Duodenal passage was determined by intraduodenal infusion of a second set of phase-specific nonabsorbable markers. Plasma cholecystokinin levels and pancreatobiliary secretions rose to a maximum at 30-60 min and then gradually declined (p less than 0.01) despite continued entry of protein and fat into the duodenum throughout the whole 4-h experimental period. High levels of both pancreatic polypeptide and peptide YY were observed in the last 2 h of the experiment. Release of factors capable of inhibiting cholecystokinin release and subsequently pancreatobiliary secretion may be responsible for the observed time-course.

Duodenal instillation of pancreatin does not abolish steatorrhea in patients with pancreatic insufficiency

Many believe that intragastric deactivation of lipase accounts for the frequent failure of orally ingested pancreatic enzymes to normalize fat absorption in patients with pancreatic insufficiency. To test this hypothesis, we measured fat absorption from a large test meal in six patients with pancreatic insufficiency after we had instilled Viokase directly into the postcibal duodenum in two doses, one to deliver lipase at about 10% of normal secretory rates and the other at four times this rate. Direct duodenal instillation of neither the low nor the high dose of Viokase, nor the low dose of Viokase plus sodium bicarbonate, normalized fat absorption from the test meal; none of these duodenal instillations significantly improved fat absorption over that after the test meal plus orally ingested Viokase. Despite these various treatments, the patients excreted an average of 25.5 g of dietary fat as opposed to 2.1 g excreted by six normal subjects after the same meal. We conclude that more than just intragastric destruction of lipase underlies the frequent failure of orally ingested pancreatin to normalize fat absorption in pancreatic insufficiency.

Intragastric behavior and absorption kinetics of a normal and "floating" modified-release capsule of isradipine under fasted and fed conditions

From measurements of drug levels in both gastric juice and plasma, we investigated whether or not a prolonged gastric residence time (GRT) is responsible for the slow absorption kinetics of a "floating" modified-release (MR) capsule of isradipine [isopropyl methyl (+/-)-4-(4-benzofurazanyl)-1,4-dihydro-2,6-dimethyl-3,5- pyridinedicarboxylate], a lipophilic dihydropyridine calcium channel blocker. The effects of a "high-fat" breakfast on the intragastric behavior and absorption kinetics were also assessed. In an open crossover design, five healthy subjects ingested either a normal or MR capsule of isradipine under fasted conditions. Serial samples of gastric juice (obtained via an indwelling nasogastric tube) and plasma were collected up to 24 h after drug intake, and were analyzed for isradipine by GC and RIA methods, respectively. The pH and titratable acid, protein, and pepsin concentrations of the gastric juice samples were also determined. Four additional subjects were similarly studied after ingesting the capsules following a high-fat breakfast. Under fasted conditions, gastric juice drug levels of the normal and MR capsules indicated a median GRT of less than 1.5 h in both cases. Plasma levels indicated a rapid absorption for the normal capsule (less than 2 h), but a remarkably slow absorption for the MR capsule, lasting 24 h or more. Under fed conditions, gastric juice and plasma profiles of the normal capsule were similar to those for the fasted case. In contrast, the MR capsule had an increased GRT (approximately 2.4 to 4.8 h) that was associated with a delayed and more extensive intragastric drug release. The corresponding plasma profiles showed a rapid absorption phase which correlated closely with the intragastric release kinetics. The influence of a high-fat meal on the release kinetics of the MR capsule did not appear related to the intragastric pH, or acid, protein, or pepsin concentrations. From these results we conclude that: (1) a prolonged GRT is not responsible for the slow absorption achieved with a "floating" MR capsule; (2) the presence or absence of food, rather than buoyancy, is the principal determinant of the GRT of the MR capsule; (3) the release and absorption of a lipophilic drug from a "floating" MR capsule may be affected by intragastric interaction with the lipid phase of meal; and (4) the major portion of drug release from the MR capsule takes place in the colon, rather than in the stomach.

Human postprandial gastric emptying of 1-3-millimeter spheres

Microspheres of pancreatin should empty from the stomachs of patients with pancreatic insufficiency as fast as food. The present study was undertaken in 26 healthy subjects to identify the size of spheres that would empty from the stomach with food and to determine whether different meals alter this size. Spheres of predefined sizes were labeled with 113mIn or 99mTc. Using a gamma-camera, we studied the concurrent gastric emptying of spheres labeled with 113mIn and of chicken liver labeled with 99mTc in 100-g, 154-kcal or 420-g, 919-kcal meals, or the concurrent emptying of 1-mm vs. larger spheres. One-millimeter spheres emptied consistently (p less than 0.01, paired t-test) faster than 2.4- or 3.2-mm spheres when ingested together with either the 420- or 100-g meals. Thus, in the 1-3-mm range of diameters, sphere size was a more important determinant of sphere emptying than meal size. Statistical analyses indicated that spheres 1.4 +/- 0.3 mm in diameter with a density of 1 empty at the same rate as 99mTc-liver. Our data indicate some commercially marketed microspheres of pancreatin will empty too slowly to be effective in digestion of food.

Vagotomy and antrectomy impairs canine fat absorption from solid but not liquid dietary sources

Mild steatorrhea is common after all ulcer operations except parietal cell vagotomy. As these operations impair the grinding and sieving of solid food, we sought to determine the effect of vagotomy and antrectomy on fat absorption from solid (e.g., liver) as compared with liquid (e.g., margarine) dietary sources in the proximal small intestine. Midgut fistulas were placed in 13 dogs; 7 were controls and 6 underwent concurrent vagotomy and antrectomy. To label solid fat, the livers of live chickens were labeled with intravenous [14C]triolein and [3H]glycerol triether, an absorbable and nonabsorbable fat label, respectively. For the liquid fat label, these markers were mixed with margarine. A standard meal of steak, liver, bread, margarine, and water, with either the liver or margarine fat labeled, was fed and the midgut effluent was sieved and centrifuged to obtain four phases: large particles (greater than 0.5 mm), small particles (less than 0.5 mm), aqueous, and oil, which were extracted and counted for 14C and 3H. The ratio of 14C to 3H in each fraction was used to determine how much fat was absorbed from each phase of chyme. With liver fat labeled, 48.3% +/- 8.1% of the [3H]glycerol triether remained in large particles after vagotomy and antrectomy compared with 3.1% +/- 1.0% in controls at midintestine (p less than 0.001). After vagotomy and antrectomy, more than half of the liver fat (solid fat) was malabsorbed (57.1% +/- 6.5% vs. 23.1% +/- 6.6% malabsorbed, p less than 0.01, vagotomy and antrectomy vs. controls), whereas fat absorption from margarine (liquid fat) was not reduced compared with controls (8.8% +/- 2.5% vs. 13.6% +/- 5.5% malabsorbed, p greater than 0.05, vagotomy and antrectomy vs. controls). These observations indicate that by reducing gastric trituration and releasing large particles of poorly digested food into the intestine, vagotomy and antrectomy impairs the absorption of fat selectively from solid, but not from liquid, dietary sources.

Differential effect of food on kinetics of bromocriptine in a modified release capsule and a conventional formulation

The influence of food on release of drug from a modified release capsule of bromocriptine 5 mg (Parlodel SRO) and a conventional formulation of bromocriptine 5 mg has been studied in 8 healthy male volunteers. Both formulations produced objective and subjective effects, such as orthostatic reactions, nausea, dizziness, vomiting and nasal congestion. The modified release capsule caused fewer side-effects than the normal capsule. Both formulations had less cardiovascular effect in the fed than in the fasting state. There was no significant difference between the normal and the modified release capsules taken fasting or after a meal in terms of the AUC extrapolated to infinity. The relative bioavailability of the 5 mg modified release capsule was 84.6% of the normal capsule under fasting conditions and 107.5% after food. In contrast to the virtually unchanged extent of absorption, the rate of absorption was markedly affected by food, especially from the conventional capsule. The mean time of 50% absorption increased from 1.06 h (fasting) to 3.2 h (fed), whereas for the modified release capsule food mainly resulted in an increased lag time of absorption. The almost instantaneous dissolution of bromocriptine from the normal capsule in vitro (both in HCl and fasting human gastric juice) and the delay of absorption after a meal in vivo suggest that the rate limiting step in absorption of the normal capsules is delivery of released drug from the stomach to the small intestine, which is delayed by food. Both the modified release 5-mg capsule and the normal 5-mg capsule showed extended suppression of prolactin over 36 h, in all subjects, both fasted and after a meal.