Effects of lansoprazole on human gastric lipase secretion and intragastric lipolysis in healthy human volunteers

Administration of a standard dose of vonoprazan fumarate delays gastric emptying in Japanese healthy adults: a prospective clinical trial

BACKGROUND

There is no established view of how gastric acid suppression affects the time for gastric emptying. Vonoprazan fumarate shows potent and durable gastric acid inhibitory effects, but its effects on gastric emptying have not been studied widely. We investigated the effects of vonoprazan fumarate on gastric emptying and measured serum gastrin and plasma ghrelin levels in healthy adults.

METHODS

Ten participants were administered 10 mg vonoprazan fumarate daily for 14 days, then 20 mg vonoprazan fumarate daily for 14 days. The gastric emptying breath test was performed and serum gastrin levels were measured at baseline and after each medication administration period. The protocol was then repeated, with the gastric emptying breath test and serum gastrin and plasma desacyl-ghrelin levels measured at baseline and the end of the medication trial.

RESULTS

Mean serum gastrin levels increased in a dose-dependent manner [baseline: 104.7 ± 50.4, after 10 mg protocol: 328 ± 123.8, after 20 mg protocol: 555 ± 378.8 (pg/mL, mean ± standard deviation), p = 0.0008]. There was a significant difference between the gastric emptying breath test Tmax at baseline and just after the 20 mg protocol (baseline: 45.5 ± 15.3, after 20 mg protocol: 60.5 ± 19.6 min, p = 0.0418). Plasma desacyl-ghrelin levels increased significantly just after the 20 mg protocol compared to those at baseline [baseline: 222.3 ± 106.4, after 20 mg protocol: 366.2 ± 178.6 (fmol/mL), p = 0.0008].

CONCLUSIONS

In healthy adults, 14 days of vonoprazan fumarate administration at 20 mg/day delayed gastric emptying.

TRIAL REGISTRATION

This clinical trial was registered in the University hospital Medical Information Network Clinical Trial Registry (Trial No. UMIN000039199 and UMIN000042969).

Colloidal aspects of dispersion and digestion of self-dispersing lipid-based formulations for poorly water-soluble drugs

Self-dispersing lipid-based formulations, particularly self-microemulsifying drug delivery systems (SMEDDS) have gained an increased interest in recent times as a means to enhance the oral bioavailability of poorly water-soluble lipophilic drugs. Upon dilution, SMEDDS self-emulsify in an aqueous fluid and usually form a kinetically stable oil-in-water emulsion or in some rare cases a true thermodynamically stable microemulsion. The digestion of the formulation leads to the production of amphiphilic digestion products that interact with endogenous amphiphilic components and form self-assembled colloidal phases in the aqueous environment of the intestine. The formed colloidal phases play a pivotal role in maintaining the lipophilic drug in the solubilised state during gastrointestinal transit prior to absorption. Thus, this review describes the structural characterisation techniques employed for SMEDDS and the recent literature studies that elucidated the colloidal aspects during dispersion and digestion of SMEDDS and solid SMEDDS. Possible future studies are proposed to gain better understanding on the colloidal aspects of SMEDDS and solid SMEDDS.

Variations in gastrointestinal lipases, pH and bile acid levels with food intake, age and diseases: Possible impact on oral lipid-based drug delivery systems

The lipids and some surfactants present in oral lipid-based drug delivery systems are potential substrates for the various lipases involved in gastrointestinal (GI) lipolysis. The levels of these enzymes, together with pH and biliairy secretion, are important parameters that condition the fate of lipid-based formulations (LBF) and the dispersion, solubilization and absorption of lipophilic drugs in the GI tract. Since in vitro methods of digestion are now combined with dissolution assays for a better assessment of LBF performance, it is essential to have a basic knowledge on lipase, pH and bile acid (BA) levels in vivo to develop relevant in vitro models. While these parameters and their variations in healthy subjects are today well documented, in vivo data on specific populations (age groups, patients with various diseases, patients with treatment affecting GI tract parameters, …) are scarce and obtaining them from clinical studies is sometimes difficult due to ethical limitations. Here we collected some in vivo data already available on the levels of digestive lipases, gastric and intestinal pH, and BAs at various ages and in patients with exocrine pancreatic insufficiency, a pathological situation that leads to drastic changes in GI tract parameters and impacts pharmacological treatments.

Molecular bionics - engineering biomaterials at the molecular level using biological principles

Life and biological units are the result of the supramolecular arrangement of many different types of molecules, all of them combined with exquisite precision to achieve specific functions. Taking inspiration from the design principles of nature allows engineering more efficient and compatible biomaterials. Indeed, bionic (from bion-, unit of life and -ic, like) materials have gained increasing attention in the last decades due to their ability to mimic some of the characteristics of nature systems, such as dynamism, selectivity, or signalling. However, there are still many challenges when it comes to their interaction with the human body, which hinder their further clinical development. Here we review some of the recent progress in the field of molecular bionics with the final aim of providing with design rules to ensure their stability in biological media as well as to engineer novel functionalities which enable navigating the human body.

Relevant pH and lipase for in vitro models of gastric digestion

The development of in vitro digestion models relies on the availability of in vivo data such as digestive enzyme levels and pH values recorded in the course of meal digestion. The variations of these parameters along the GI tract are important for designing dynamic digestion models but also static models for which the choice of representative conditions of the gastric and intestinal conditions is critical. Simulating gastric digestion with a static model and a single set of parameters is particularly challenging because the variations in pH and enzyme concentration occurring in the stomach are much broader than those occurring in the small intestine. A review of the literature on this topic reveals that most models of gastric digestion use very low pH values that are not representative of the fed conditions. This is illustrated here by showing the variations in gastric pH as a function of meal gastric emptying instead of time. This representation highlights those pH values that are the most relevant for testing meal digestion in the stomach. Gastric lipolysis is still largely ignored or is performed with microbial lipases. In vivo data on gastric lipase and lipolysis have however been collected in humans and dogs during test meals. The biochemical characterization of gastric lipase has shown that this enzyme is rather unique among lipases: (i) stability and activity in the pH range 2 to 7 with an optimum at pH 4-5.4; (ii) high tensioactivity that allows resistance to bile salts and penetration into phospholipid layers covering TAG droplets; (iii) sn-3 stereospecificity for TAG hydrolysis; and (iv) resistance to pepsin. Most of these properties have been known for more than two decades and should provide a rational basis for the replacement of gastric lipase by other lipases when gastric lipase is not available.

Development and validation of a lipase nasogastric tube position test

Background

Nasogastric tube position should be checked every day by either aspirate pH or chest radiography to prevent fatal misplaced feeding into the lungs. Many patients do not have acidic gastric aspirates and require daily chest radiographs. We developed and validated a lipase test that was compatible with non-acidic gastric aspirates.

Methods

We conducted evaluations of diagnostic test accuracy at a teaching hospital in development and validation stages. Development: We collected gastric and lung aspirates from 34 consecutive patients. We measured pH and human gastric lipase activity in the laboratory. These data helped us develop the lipase test. Ingenza Ltd (Roslin, Scotland) created tributyrin-coated pH test paper, which human gastric lipase converted into butyric acid, thus correcting false negatives. Validation: We tested nasogastric feeding tube aspirates from 36 consecutive patients with pH and lipase tests, using chest radiography or trial by use as the reference standard.

Results

Development: We demonstrated human gastric lipase activity in the non-acidic stomach aspirates. Validation: The accuracy of the lipase test (sensitivity 97.2%, specificity 100%) was significantly better than pH (sensitivity 65.7%, specificity 100%, p<0.05).

Conclusions

When nasogastric tube stomach aspirates were not acidic and pH was falsely negative, the lipase test showed a true positive and was significantly more accurate.

Lipase Supplementation before a High-Fat Meal Reduces Perceptions of Fullness in Healthy Subjects

Background/Aims

Postprandial symptoms of fullness and abdominal discomfort are common after fatty meals. Gastric lipases hydrolyze 10% to 20% of dietary triglycerides during the stomach trituration period of digestion. The aim of this study was to evaluate the effects of acid-resistant lipase on upper gastrointestinal symptoms, including fullness and bloating, as well as on gastric myoelectrical activity after healthy subjects ingested a high-fat, liquid meal.

Methods

This study utilized a double-blind, placebo-controlled, crossover design with 16 healthy volunteers who ingested either a capsule containing 280 mg of acid-resistant lipase or a placebo immediately before a fatty meal (355 calories, 55% fat). Participants rated their stomach fullness, bloating, and nausea before and at timed intervals for 60 minutes after the meal. Electrogastrograms were obtained to assess the gastric myoelectrical activity.

Results

Stomach fullness, bloating, and nausea increased significantly 10 minutes after ingestion of the fatty meal (p<0.01), whereas normal gastric myoelectrical activity decreased and tachygastria increased (p<0.05). With lipase, reports of stomach fullness were significantly lower compared with placebo (p<0.05), but no effect on gastric myoelectrical activity or other upper gastrointestinal symptoms was observed.

Conclusions

The high-fat meal induced transient fullness, bloating, nausea, and tachygastria in healthy individuals, consistent with post-prandial distress syndrome. Acid-resistant lipase supplementation significantly decreased stomach fullness.

Understanding the lipid-digestion processes in the GI tract before designing lipid-based drug-delivery systems

Many of the compounds present in lipid-based drug-delivery systems are esters, such as acylglycerols, phospholipids, polyethyleneglycol mono- and di-esters and polysorbate, which can be hydrolyzed by the various lipolytic enzymes present in the GI tract. Lipolysis of these compounds, along with dietary fats, affects the solubility, dispersion and bioavailibity of poorly water-soluble drugs. Pharmaceutical scientists have been taking a new interest in fat digestion in this context, and several studies presenting in vitro gastrointestinal lipolysis models have been published. In most models, it is generally assumed that pancreatic lipase is the main enzyme involved in the gastrointestinal lipolysis of lipid formulations. It was established, however, that gastric lipase, pancreatic carboxyl ester hydrolaze and pancreatic lipase-related protein 2 are the major players involved in the lipolysis of lipid excipients containing acylglycerols and polyethyleneglycol esters. These findings have shown that the lipolysis of lipid excipients may actually start in the stomach and involve several lipolytic enzymes. These findings should therefore be taken into account when testing in vitro the dispersion and bioavailability of poorly water-soluble drugs formulated with lipids. In this review, we present the latest data available about the lipolytic enzymes involved in gastrointestinal lipolysis and suggest tracks for designing physiologically relevant in vitro digestion models.

Use of artificial digestive systems to investigate the biopharmaceutical factors influencing the survival of probiotic yeast during gastrointestinal transit in humans

PURPOSE

To evaluate the influence of the main biopharmaceutical factors on the viability of a new probiotic yeast strain, using dynamic in vitro systems simulating human gastric/small intestinal (TIM) and large intestinal (ARCOL) environments.

METHODS

The viability of Saccharomyces cerevisiae CNCM I-3856 throughout the artificial digestive tract was determined by microbial counting. We investigated the effects of galenic formulation, food intake, dose, mode and frequency of administration on yeast survival rate.

RESULTS

In both fasted and fed states, yeast viability in the upper digestive tract was significantly higher when the probiotic was administered in hydroxypropylmethylcellulose (HPMC) capsules compared to tablets. Food intake led to a delay in yeast release and a two-fold increase in strain survival. Whatever the dose, yeasts were particularly sensitive to the large intestinal environment. High concentrations of probiotic could only be maintained in the colon when it was inoculated twice a day over a 5-h-period.

CONCLUSIONS

TIM and ARCOL are complementary in vitro tools relevant for screening purposes, supplying valuable information on the effects of galenic form, food intake and dose regimen on the viability of probiotics throughout the human digestive tract.

Effects of proton pump inhibitors on gastric emptying: a systematic review

The proton pump inhibitor (PPI) is widely used for the treatment of gastroesophageal reflux disease, peptic ulcer diseases, and functional dyspepsia. The pathogenesis of these acid-related and/or functional upper gastrointestinal disorders is potentially associated with abnormal gastric emptying. To date, variable effects of PPIs on gastric emptying have been reported. Therefore, it is relevant to gather and analyze published information on this topic. A systematic literature search has been performed, showing that the delaying effect of PPIs on gastric emptying of solid meals is consistent, whereas the effect of PPIs on the emptying of liquids is inconsistent. The underlying mechanisms whereby PPIs may affect gastric emptying have been discussed, most of which still remain hypothetic. Gastric emptying of solids involves a process of peptic hydrolysis. PPIs impair the hydrolytic digestion by inhibiting acid-dependent peptic activity, thereby delaying the solid emptying. Gastric emptying of liquids largely depends on volume and energy density of intragastric contents. PPIs variably modify the volume and the energy density by reducing gastric fluid secretion, thereby modifying the liquid emptying in an unpredictable manner. Hypergastrinemia has been considered to delay gastric emptying, but it seems of minor importance in the regulation of gastric emptying during PPI use. The delayed emptying of solids due to PPI therapy may have clinical implications in the management of gastroesophageal reflux disease, functional dyspepsia, as well as diabetes.

Self-assembled structures and pKa value of oleic acid in systems of biological relevance

In the human digestion process, triglycerides are hydrolyzed by lipases to monoglycerides and the corresponding fatty acids. Here we report the self-assembly of structures in biologically relevant, emulsified oleic acid-monoolein mixtures at various pH values and oleic acid concentrations. Small-angle X-ray scattering, cryogenic transmission electron microscopy, and dynamic light scattering were used to investigate the structures formed, and to follow their transitions while these factors were varied. The addition of oleic acid to monoolein-based cubosomes was found to increase the critical packing parameter in the system. Structural transitions from bicontinuous cubosomes through hexosomes and micellar cubosomes (Fd3m symmetry) to emulsified microemulsions occur with increasing oleic acid concentration. At sufficiently high oleic acid concentration, the internal particle structure was also found to strongly depend on the pH of the aqueous phase: transformations from emulsified microemulsion through micellar cubosomes, hexosomes, and bicontinuous cubosomes to vesicles can be observed as a function of increasing pH. The reversible transition from liquid crystals to vesicles occurs at intestinal pH values (between pH 7 and 8). The hydrodynamic radius of the particles decreases from around 120 nm for internally structured particles to around 60 nm for vesicles. All transitions with pH are reversible. Finally, the apparent pK(a) for oleic acid in monoolein could be determined from the change of structure with pH. This value is within the physiological pH range of the intestine and depends somewhat on composition.

Phospholipids and lipid-based formulations in oral drug delivery

Phospholipids become increasingly important as formulation excipients and as active ingredients per se. The present article summarizes particular features of commonly used phospholipids and their application spectrum within oral drug formulation and elucidates current strategies to improve bioavailability and disposition of orally administered drugs. Advantages of phospholipids formulations not only comprise enhanced bioavailability of drugs with low aqueous solubility or low membrane penetration potential, but also improvement or alteration of uptake and release of drugs, protection of sensitive active agents from degradation in the gastrointestinal tract, reduction of gastrointestinal side effects of non-steroidal anti-inflammatory drugs and even masking of bitter taste of orally applied drugs. Technological strategies to achieve these effects are highly diverse and offer various possibilities of liquid, semi-liquid and solid lipid-based formulations for drug delivery optimization.

Lipids and lipid-based formulations: optimizing the oral delivery of lipophilic drugs

Highly potent, but poorly water-soluble, drug candidates are common outcomes of contemporary drug discovery programmes and present a number of challenges to drug development - most notably, the issue of reduced systemic exposure after oral administration. However, it is increasingly apparent that formulations containing natural and/or synthetic lipids present a viable means for enhancing the oral bioavailability of some poorly water-soluble, highly lipophilic drugs. This Review details the mechanisms by which lipids and lipidic excipients affect the oral absorption of lipophilic drugs and provides a perspective on the possible future applications of lipid-based delivery systems. Particular emphasis has been placed on the capacity of lipids to enhance drug solubilization in the intestinal milieu, recruit intestinal lymphatic drug transport (and thereby reduce first-pass drug metabolism) and alter enterocyte-based drug transport and disposition.

Quantitative study of digestive enzyme secretion and gastrointestinal lipolysis in chronic pancreatitis

BACKGROUND & AIMS

The contribution of human gastric lipase (HGL) to the overall lipolysis process in chronic pancreatitis (CP), as well as the relative pancreatic enzyme levels, rarely are addressed. This study was designed to quantify pancreatic and extrapancreatic enzyme output, activity, and stability in CP patients vs. healthy volunteers.

METHODS

Healthy volunteers (n = 6), mild CP patients (n = 5), and severe (n = 7) CP patients were intubated with gastric and duodenal tubes before the administration of a test meal. HGL, human pancreatic lipase (HPL), chymotrypsin, and amylase concentrations were assessed in gastric and duodenal samples by measuring the respective enzymatic activities. Intragastric and overall lipolysis levels at the angle of Treitz were estimated based on quantitative analysis of lipolysis products. Similar analyses were performed on duodenal contents incubated ex vivo for studying enzyme stability and evolution of lipolysis.

RESULTS

Although HPL, chymotrypsin, and amylase outputs all were extremely low, HGL outputs in patients with severe CP (46.8 +/- 31.0 mg) were 3-4-fold higher than in healthy controls (13.3 +/- 13.8 mg). Intragastric lipolysis did not increase, however, in patients with severe CP, probably because of the rapid decrease in the pH level of the gastric contents caused by a higher gastric acid secretion. HGL remains active and highly stable in the acidic duodenal contents of CP patients, and, overall, can achieve a significant lipolysis of the dietary triglycerides (30% of the control values) in the absence of HPL.

CONCLUSIONS

Although all pancreatic enzyme secretions are simultaneously reduced in severe CP, gastric lipase can compensate partly for the loss of pancreatic lipase but not normalize overall lipolytic activity.

Investigation into the role of cephalic stimulation of acid secretion on gastric emptying and appetite following a soup meal using the gastric acid inhibitor omeprazole

We previously showed that oral administration of a liquid soup preload was associated with a slower rate of gastric emptying and suppressed appetite more compared with intragastric administration of the same soup [Appetite 31(1998)377]. The present study was designed to investigate whether these results could be explained by the cephalic stimulation of acid secretion induced by oral administration. Eight healthy male subjects took part in a double-blind placebo controlled study comparing the effects of omeprazole and placebo on gastric emptying, appetite ratings and subsequent food intake following the ingestion of a liquid soup. Subjects were administered with a single oral dose of 80 mg omeprazole or placebo 3 h prior to ingesting the radiolabelled soup preload (400 kcal; 425 ml) over 15 min. Ratings of hunger, desire to eat and fullness were recorded over 135 min and gastric emptying was measured by scintigraphy. Food intake was evaluated from a test meal (yoghurt drink) given 120 min after the end of the soup ingestion. Analysis of data showed that there was no significant difference between omeprazole and placebo in gastric emptying, appetite or subsequent energy intake from the test meal. The results suggest that gastric acid secretion is not responsible for the differences in gastric emptying and appetite observed between intragastrically infused and orally administered soup preloads.

Advantage of expressing the variations in some digestive parameters as a function of gastric emptying instead of time

BACKGROUND/AIM

Gastric emptying is a major cause of variability when studying gastrointestinal parameters as a function of time. Here, we investigate whether the parametric variability could be reduced by running experiments on a gastric emptying basis rather than on a time basis.

METHODS

Healthy volunteers were intubated with gastric and duodenal tubes and were given a liquid meal containing polyethylene glycol to monitor gastric emptying. Gastric pH and human gastric lipase (HGL) concentrations were measured. Their variations were plotted as a function of either time or gastric emptying (%). In both cases, mean curves of variation were established by polynomial regression.

RESULTS

When time was the variable used, the overall deviation of the experimental values from the values given by the best-fitting curve was high (chi2 = 33 for gastric pH; chi2 = 1,744 for HGL), and the individual deviations increased with time. When gastric emptying was the variable used, the overall deviation of the experimental values from the values given by the best-fitting curve was much lower (chi2 = 10 for gastric pH; chi2 = 642 for HGL).

CONCLUSIONS

Expressing gastric pH or HGL concentration as a function of gastric emptying instead of time makes it possible to reduce the individual variability. This new type of data analysis may be of a general interest to observe specific variations of gastrointestinal parameters induced by drugs, hormones, and meals, and that might be masked by the large intrinsic variability induced by gastric emptying.