Effects of posture on gastric emptying, transpyloric flow, and hunger after a glucose drink in healthy humans

Magnetization transfer MRI of intragastric milk digestion: A feasibility study in humans

Gastric milk protein coagulation has been extensively studied using in vitro and animal models. Yet, verifying these results in humans remains essential. In this study, we assessed the feasibility of using MT MRI for monitoring milk protein coagulation in vivo in humans. Twelve adults underwent MRI scans before and after ingesting 300 g of milk with low- or high-protein denaturation (LPD or HPD, respectively). We assessed coagulation and gastric emptying dynamics by deriving the MT ratio (MTR), total gastric content (TGC), semi-solid, and liquid volumes. The MTR values increased during digestion for both milk products, indicating an increase in the degree of coagulation. Prolonged heating of milk did not affect the MTR (MD = 16 %, 95 % CI [10-21], p = 0.15), but resulted in higher TGC volumes (MD 40.3 mL, 95 % CI [25.5-55.1], p = 0.044), indicating slower gastric emptying. We thus showed that by combining MT with conventional anatomical MRI both milk protein coagulation and gastric emptying dynamics, and thereby the impact of heating on gastric milk digestion, can be assessed in vivo in humans. Our work underpins the feasibility of using MRI as a non-invasive imaging tool for studying the effects of food processing and composition on gastric digestion.

Is there a fast track ("Darmstrasse") for fluids in the small intestine? Evidence from magnetic resonance imaging

BACKGROUND

The transit and distribution pattern of fluids in the small intestine is a key parameter for the dissolution and absorption of drugs. Although some information is known about the small intestinal water content after administration of fluid volumes and meals, the intestinal transit of orally ingested fluids and solutions has been barely investigated. The aim of this three-arm, cross-over, 9-subject human study was to investigate the transit of orally ingested water in the small intestine under fasting and postprandial conditions using MRI. To identify the ingested water, manganese gluconate, which can be identified with T1-weighted MRI sequences, was added as a marker. Using Horos (DICOM software), quantification of the distribution of Mn2+ ions in the gastrointestinal tract in fasted versus fed state (standard meal by FDA guidance and a light meal) was possible. The distribution and approximate wetted intestinal length was very similar in the fasting and postprandial states, suggesting rapid transport of water ingested after a meal through the chyme-filled small intestine in continuation of the "Magenstrasse" (stomach road). In some subjects, manganese gluconate reached deeper parts of the small intestine even more quickly in the postprandial state than in the fasting arm of the study. A deeper understanding of the behaviour of solutes in the gastrointestinal tract is fundamental to a mechanistic explanation for the kinetic interaction between food and drug intake (food effects).

A systematic review on diagnosis and treatment of gastrointestinal diseases by magnetically controlled capsule endoscopy and artificial intelligence

Background

Magnetically controlled capsule endoscopy (MCCE) is a non-invasive, painless, comfortable, and safe equipment to diagnose gastrointestinal diseases (GID), partially overcoming the shortcomings of conventional endoscopy and wireless capsule endoscopy (WCE). With advancements in technology, the main technical parameters of MCCE have continuously been improved, and MCCE has become more intelligent.

Objectives

The aim of this systematic review was to summarize the research progress of MCCE and artificial intelligence (AI) in the diagnosis and treatment of GID.

Data Sources and Methods

We conducted a systematic search of PubMed and EMBASE for published studies on GID detection of MCCE, physical factors related to MCCE imaging quality, the application of AI in aiding MCCE, and its additional functions. We synergistically reviewed the included studies, extracted relevant data, and made comparisons.

Results

MCCE was confirmed to have the same performance as conventional gastroscopy and WCE in detecting common GID, while it lacks research in detecting early gastric cancer (EGC). The body position and cleanliness of the gastrointestinal tract are the main factors affecting imaging quality. The applications of AI in screening intestinal diseases have been comprehensive, while in the detection of common gastric diseases such as ulcers, it has been developed. MCCE can perform some additional functions, such as observations of drug behavior in the stomach and drug damage to the gastric mucosa. Furthermore, it can be improved to perform a biopsy.

Conclusion

This comprehensive review showed that the MCCE technology has made great progress, but studies on GID detection and treatment by MCCE are in the primary stage. Further studies are required to confirm the performance of MCCE.

Computational modeling of drug dissolution in the human stomach: Effects of posture and gastroparesis on drug bioavailability

The oral route is the most common choice for drug administration because of several advantages, such as convenience, low cost, and high patient compliance, and the demand and investment in research and development for oral drugs continue to grow. The rate of dissolution and gastric emptying of the dissolved active pharmaceutical ingredient (API) into the duodenum is modulated by gastric motility, physical properties of the pill, and the contents of the stomach, but current in vitro procedures for assessing dissolution of oral drugs are limited in their ability to recapitulate this process. This is particularly relevant for disease conditions, such as gastroparesis, that alter the anatomy and/or physiology of the stomach. In silico models of gastric biomechanics offer the potential for overcoming these limitations of existing methods. In the current study, we employ a biomimetic in silico simulator based on the realistic anatomy and morphology of the stomach (referred to as "StomachSim") to investigate and quantify the effect of body posture and stomach motility on drug bioavailability. The simulations show that changes in posture can potentially have a significant (up to 83%) effect on the emptying rate of the API into the duodenum. Similarly, a reduction in antral contractility associated with gastroparesis can also be found to significantly reduce the dissolution of the pill as well as emptying of the API into the duodenum. The simulations show that for an equivalent motility index, the reduction in gastric emptying due to neuropathic gastroparesis is larger by a factor of about five compared to myopathic gastroparesis.

Gastric Emptying and Intragastric Behavior of Breast Milk and Infant Formula in Lactating Mothers

BACKGROUND

When sufficient breast milk is not available, infant formula is often used as an alternative. As for digestion, gastric behavior of infant formula and breast milk have not been studied in detail.

OBJECTIVE

This study aimed to compare gastric emptying and intragastric behavior between breast milk and infant formula in vivo using MRI.

METHODS

In this randomized crossover study, 16 lactating mothers (age: 31.7 ± 2.9 y; time since giving birth: 9.3 ± 2 mo), underwent gastric MRI scans before and after consumption of 200 mL of infant formula or their own breast milk. MRI scans were performed after an overnight fast (baseline) and every 10 min up until 60 min following ingestion. Primary outcomes were gastric emptying measures and the secondary outcome was gastric layer volume over time. Differences between infant formula and breast milk in total gastric volume and layering volume were tested using linear mixed models.

RESULTS

Gastric emptying half-time was 5.1 min faster for breast milk than for infant formula (95% CI: -19.0 to 29.2) (n = 14). Within a subgroup (n = 12) with similar initial gastric volume (<20 mL difference), gastric emptying half-time was 20 min faster for breast milk (95% CI: 1.23-43.1). Top layer volume (n = 16) was 6.4 mL greater for infant formula than for breast milk (95% CI: 1.9-10.8). This effect is driven by t = 10 and t = 20 min postingestion.

CONCLUSIONS

When taking initial gastric volume into account, breast milk emptied faster than infant formula in women, which is in line with previous findings in infants. Infant formula showed a significantly larger top layer volume in the first 20 min after ingestion. MRI in adults may find application in studies assessing gastric behavior of infant formula.

Vagally Mediated Gut-Brain Relationships in Appetite Control-Insights from Porcine Studies

Signals arising from the upper part of the gut are essential for the regulation of food intake, particularly satiation. This information is supplied to the brain partly by vagal nervous afferents. The porcine model, because of its sizeable gyrencephalic brain, omnivorous regimen, and comparative anatomy of the proximal part of the gut to that of humans, has provided several important insights relating to the relevance of vagally mediated gut-brain relationships to the regulation of food intake. Furthermore, its large size combined with the capacity to become obese while overeating a western diet makes it a pivotal addition to existing murine models, especially for translational studies relating to obesity. How gastric, proximal intestinal, and portal information relating to meal arrival and transit are encoded by vagal afferents and their further processing by primary and secondary brain projections are reviewed. Their peripheral and central plasticities in the context of obesity are emphasized. We also present recent insights derived from chronic stimulation of the abdominal vagi with specific reference to the modulation of mesolimbic structures and their role in the restoration of insulin sensitivity in the obese miniature pig model.

Gastroparesis: a turning point in understanding and treatment

Gastroparesis is defined by delayed gastric emptying (GE) and symptoms of nausea, vomiting, bloating, postprandial fullness, early satiety and abdominal pain. Most common aetiologies include diabetes, postsurgical and postinfectious, but in many cases it is idiopathic. Clinical presentation and natural history vary by the aetiology. There is significant morbidity and healthcare utilisation associated with gastroparesis. Mechanistic studies from diabetic animal models of delayed GE as well as human full-thickness biopsies have significantly advanced our understanding of this disorder. An innate immune dysregulation and injury to the interstitial cells of Cajal and other components of the enteric nervous system through paracrine and oxidative stress mediators is likely central to the pathogenesis of gastroparesis. Scintigraphy and 13C breath testing provide the most validated assessment of GE. The stagnant gastroparesis therapeutic landscape is likely to soon see significant changes. Relatively newer treatment strategies include antiemetics (aprepitant), prokinetics (prucalopride, relamorelin) and fundic relaxants (acotiamide, buspirone). Endoscopic pyloromyotomy appears promising over the short term, especially for symptoms of nausea and vomiting. Further controlled trials and identification of the appropriate subgroup with pyloric dysfunction and assessment of long-term outcomes are essential. This review highlights the clinical presentation, diagnosis, mechanisms and treatment advancements for gastroparesis.

Repetitive Position Change Improves Gastric Cleanliness for Magnetically Controlled Capsule Gastroscopy

BACKGROUND AND AIMS

Good gastric preparation is essential for magnetically controlled capsule gastroscopy (MCCG) examination. This study aims to determine if repetitive position change after dimethicone premedication could further improve gastric cleanliness for MCCG.

METHODS

Consecutive patients referred for MCCG in our center from May 7 to May 31, 2018 were prospectively enrolled and randomized to undergo repetitive position change for 15 min (position change group) or not (conventional group) after ingesting dimethicone. Primary outcome was gastric cleanliness score and secondary outcomes were detection rate of positive findings, number of lesions per patient, gastric examination time, and safety of MCCG.

RESULTS

Totals of 43 and 40 were included in the position change and conventional groups, respectively. Gastric cleanliness score in the position change group was significantly higher than in the conventional group (21.2 ± 1.0 vs. 18.6 ± 2.0, P  < 0.001), as was the proportion of acceptable gastric cleanliness (gastric cleanliness score ≥ 18) (100% vs. 72.5%, P  < 0.001). There was no statistical difference in detection rate of positive findings between the two groups (27.9% vs. 27.5%, P  = 0.97). In the position change group, the gastric examination time was significantly reduced (13.2 ± 4.0 vs. 15.3 ± 5.1, P = 0.043). No adverse events were observed.

CONCLUSIONS

Repetitive position change after dimethicone premedication significantly improves gastric cleanliness for MCCG examination. Clinical Trial Registration ClinicalTrials.gov, ID: NCT03514966.

Just add water: Effects of added gastric distention by water on gastric emptying and satiety related brain activity

BACKGROUND

Gastric distention contributes to meal termination. There is little research on the neural correlates of gastric distention by food. To date, neural measures have not been obtained concurrently with measurements of gastric distention.

OBJECTIVES

1) To study how offering a small versus a large water load following a standardized nutrient load affects gastric distention over time. 2) To assess associations between satiety experiences and brain activity and the degree of gastric distention.

METHOD

19 healthy males (age 22.2 ± 2.5 y, BMI 21.8 ± 1.5 kg/m²) participated in a randomized crossover study with two treatments: ingestion of a 500-kcal 150-mL liquid meal shake followed by a low (LV, 50 mL) or a high volume (HV, 350 mL) water load. At baseline and three times after ingestion satiety was scored, MRI scans were made to determine total gastric content volume (TGV) and functional MRI scans were made to measure cerebral blood flow (CBF).

RESULTS

TGV was significantly higher for HV compared to LV at all time points (p < 0.001) with relative differences between HV and LV of 292 ± 37 mL after ingestion, 182 ± 83 mL at t = 15 min and 62 ± 57 mL at t = 35 min. Hunger decreased (p = 0.023) and fullness increased (p = 0.030) significantly more for HV compared to LV. Ingestion increased CBF in the inferior frontal gyrus and the anterior insula, but there were no differences between treatments. There were no significant correlations between appetite ratings and CBF values.

CONCLUSION

Performing concurrent gastric MRI and CBF measurements can be used to investigate neural correlates of gastric distention. Increased distention did not induce significantly greater brain activation. Future research should further examine the role of the inferior frontal gyrus in satiety.

Effects of Glutamine on Gastric Emptying of Low- and High-Nutrient Drinks in Healthy Young Subjects-Impact on Glycaemia

Glutamine is a potent stimulus for the release of glucagon-like peptide-1, which increases postprandial insulin and slows gastric emptying (GE). We determined the effects of glutamine on GE of, and glycaemic responses to, low- and high-nutrient drinks in eight healthy males (mean age 21.6 ± 0.7 years and BMI 22.9 ± 0.7 kg/m²). Participants were studied on four occasions on which they consumed either a low-nutrient (beef soup; 18 kcal) or high-nutrient (75 g dextrose; 255 kcal) drink, each with or without 30 g of glutamine (120 kcal), in a randomised, crossover design. GE (2D ultrasound), blood glucose and plasma insulin concentrations were measured concurrently. Glutamine slowed GE (half emptying time (T50)) of both low- (45 ± 3 min vs. 26 ± 2 min, p < 0.001), and high-nutrient, (100 ± 5 min vs. 77 ± 5 min, p = 0.03) drinks, however, there was no effect on GE of the high nutrient drinks when expressed as kcal/min (3.39 ± 0.21 kcal/min vs. 3.81 ± 0.20 kcal/min, p = 0.25). There was no change in blood glucose after the low-nutrient drinks with or without glutamine, despite a slight increase in plasma insulin with glutamine (p = 0.007). The rise in blood glucose following the high-nutrient drink (p = 0.0001) was attenuated during the first 60 min by glutamine (p = 0.007). We conclude that in healthy subjects, glutamine slows GE of both low- and high-nutrient drinks comparably and attenuates the rise in blood glucose after the high-nutrient glucose drink.

A Multiphase Flow in the Antroduodenal Portion of the Gastrointestinal Tract: A Mathematical Model

A group of authors has developed a multilevel mathematical model that focuses on functional disorders in a human body associated with various chemical, physical, social, and other factors. At this point, the researchers have come up with structure, basic definitions and concepts of a mathematical model at the "macrolevel" that allow describing processes in a human body as a whole. Currently we are working at the "mesolevel" of organs and systems. Due to complexity of the tasks, this paper deals with only one meso-fragment of a digestive system model. It describes some aspects related to modeling multiphase flow in the antroduodenal portion of the gastrointestinal tract. Biochemical reactions, dissolution of food particles, and motor, secretory, and absorbing functions of the tract are taken into consideration. The paper outlines some results concerning influence of secretory function disorders on food dissolution rate and tract contents acidity. The effect which food density has on inflow of food masses from a stomach to a bowel is analyzed. We assume that the future development of the model will include digestive enzymes and related reactions of lipolysis, proteolysis, and carbohydrates breakdown.

Effects of Posture and Meal Volume on Gastric Emptying, Intestinal Transit, Oral Glucose Tolerance, Blood Pressure and Gastrointestinal Symptoms After Roux-en-Y Gastric Bypass

BACKGROUND

The purpose of this study is to determine the effects of posture and drink volume on gastric/pouch emptying (G/PE), intestinal transit, hormones, absorption, glycaemia, blood pressure and gastrointestinal (GI) symptoms after gastric bypass (Roux-en-Y gastric bypass (RYGB)).

METHODS

Ten RYGB subjects were studied on four occasions in randomized order (sitting vs. supine posture; 50 vs. 150 ml of labelled water mixed with 3 g 3-O-methyl-D-glucose (3-OMG) and 50 g glucose). G/PE, caecal arrival time (CAT), blood glucose, plasma insulin, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), peptide YY (PYY), 3-OMG, blood pressure, heart rate and GI symptoms were assessed over 240 min. Controls were ten volunteers with no medical condition or previous abdominal surgery, who were studied with the 150-ml drink in the sitting position.

RESULTS

Compared to controls, PE (P < 0.001) and CAT (P < 0.001) were substantially more rapid in RYGB subjects. In RYGB, PE was more rapid in the sitting position (2.5 ± 0.7 vs. 16.6 ± 5.3 min, P = 0.02) and tends to be faster after 150 ml than the 50-ml drinks (9.5 ± 2.9 vs. 14.0 ± 3.5 min, P = 0.16). The sitting position and larger volume drinks were associated with greater releases of insulin, GLP-1 and PYY, as well as more hypotension (P < 0.01), tachycardia (P < 0.01) and postprandial symptoms (P < 0.001).

CONCLUSIONS

Pouch emptying, blood pressure and GI symptoms after RYGB are dependent on both posture and meal volume.

A novel dynamic scintigraphic technique for assessing duodenal contractions during gastric emptying in humans: a feasibility study

Duodenal contractions are thought to play a role in the control of gastric emptying. Although noninvasive techniques, such as ultrasonography and MRI, have been proposed for studying duodenal contractile activity in humans, there are no reports on the use of scintigraphy for this purpose. This work aimed to describe a novel scintigraphic technique for assessing duodenal contractility during gastric emptying in humans, and to present preliminary data on the frequency and amplitude of contractions detected in three different duodenal segments. Fasted young healthy volunteers (N=12) were given either a liquid or a solid test meal of similar calorie content (400 kcal) labeled with 99mTc-phytate. Static images were collected to determine gastric emptying. Dynamic images of the anterior aspect of the abdomen (1 frame/s) were also acquired periodically in a standard position for 256 s at 15-30 min intervals. 'Activity versus time' curves were generated for regions of interest corresponding to the proximal, middle, and distal duodenal segments. Curves were digitally filtered and processed to estimate both dominant frequency (fast Fourier transform) and amplitude (mean ejection fraction) of postprandial duodenal contractions. There were no significant differences regarding dominant frequency among proximal, middle, and distal duodenal regions of interest. In addition, there were no significant differences between the liquid and the solid meal in terms of either frequency or amplitude of duodenal contractions. Characterization of duodenal contractions in humans using scintigraphy is feasible and yields consistent data for both the frequency and the amplitude of postprandial contractions, which seems to be rather independent of meal consistency.

The effect of body position on postprandial perceptions, gastric emptying, and intragastric meal distribution: an ultrasonographic study in reclining healthy subjects

OBJECTIVE

Postprandial dyspepsia is common and may be associated with abnormal intragastric distribution of food. We aimed to determine the effect of body position on gastric emptying, meal distribution, and postprandial perceptions in healthy subjects.

MATERIAL AND METHODS

Eight adolescents (4 females and 4 males aged 14 years) were investigated using three-dimensional ultrasonography. The subjects were studied twice in a random order: once in the right lateral recumbent (RLR) position and once in the left lateral recumbent (LLR) position. Postprandial perceptions, gastric volumes, and antral areas were recorded immediately after the ingestion of 500 ml of a low-caloric meat soup over 4 min, and at 10 and 20 min following the meal.

RESULTS

Postprandial perceptions (epigastric pain, nausea, and fullness) were more pronounced in the RLR position compared to the LLR position, particularly at the end of the meal ingestion (p < 0.01). Gastric volumes were significantly smaller in the RLR position compared to the LLR position at 10 min (p < 0.01) and 20 min (p < 0.05). Antral areas were significantly wider in the RLR position compared to the LLR position at 10 min (p < 0.05) and 20 min (p < 0.01).

CONCLUSION

Postprandial perceptions are more pronounced, gastric emptying is faster, and antral area is wider in the RLR position compared to the LLR position. The results suggest that lying on the left side after a meal may be a measure to reduce postprandial dyspeptic sensations.

Designing food structures for nutrition and health benefits

In addition to providing specific sensory properties (e.g., flavor or textures), there is a need to produce foods that also provide functionality within the gastrointestinal (GI) tract, over and above simple nutrition. As such, there is a need to understand the physical and chemical processes occurring in the mouth, stomach, small intestine, and large intestine, in addition to the food structure-physiology interactions. In vivo techniques and in vitro models have allowed us to study and simulate these processes, which aids us in the design of food microstructures that can provide functionality within the human body. Furthermore, it is important to be aware of the health or nutritional needs of different groups of consumers when designing food structures, to provide targeted functionality. Examples of three groups of consumers (elderly, obese, and athletes) are given to demonstrate their differing nutritional requirements and the formulation engineering approaches that can be utilized to improve the health of these individuals. Eating is a pleasurable process, but foods of the future will be required to provide much more in terms of functionality for health and nutrition.

Comparative effects on glucose absorption of intragastric and post-pyloric nutrient delivery in the critically ill

INTRODUCTION

Studies in the critically ill that evaluate intragastric and post-pyloric delivery of nutrient have yielded conflicting data. A limitation of these studies is that the influence in the route of feeding on glucose absorption and glycaemia has not been determined.

METHODS

In 68 mechanically ventilated critically ill patients, liquid nutrient (100 ml; 1 kcal/ml containing 3 g of 3-O-Methyl-D-glucopyranose (3-OMG), as a marker of glucose absorption), was infused into either the stomach (n = 24) or small intestine (n = 44) over six minutes. Blood glucose and serum 3-OMG concentrations were measured at regular intervals for 240 minutes and the area under the curves (AUCs) calculated for 'early' (AUC60) and 'overall' (AUC240) time periods. Data are presented as mean (95% confidence intervals).

RESULTS

Glucose absorption was initially more rapid following post-pyloric, when compared with intragastric, feeding (3-OMG AUC60: intragastric 7.3 (4.3, 10.2) vs. post-pyloric 12.5 (10.1, 14.8) mmol/l.min; P = 0.008); however, 'overall' glucose absorption was similar (AUC240: 49.1 (34.8, 63.5) vs. 56.6 (48.9, 64.3) mmol/l.min; P = 0.31). Post-pyloric administration of nutrients was also associated with greater increases in blood glucose concentrations in the 'early' period (AUC60: 472 (425, 519) vs. 534 (501, 569) mmol/l.min; P = 0.03), but 'overall' glycaemia was also similar (AUC240: 1,875 (1,674, 2,075) vs. 1,898 (1,755, 2,041) mmol/l.min; P = 0.85).

CONCLUSIONS

In the critically ill, glucose absorption was similar whether nutrient was administered via a gastric or post-pyloric catheter. These data may have implications for the perceived benefit of post-pyloric feeding on nutritional outcomes and warrant further investigation.

Evaluation of gastrointestinal transit in clinical practice: position paper of the American and European Neurogastroenterology and Motility Societies

BACKGROUND

Disorders of gastrointestinal (GI) transit and motility are common, and cause either delayed or accelerated transit through the stomach, small intestine or colon, and affect one or more regions. Assessment of regional and/or whole gut transit times can provide direct measurements and diagnostic information to explain the cause of symptoms, and plan therapy.

PURPOSE

Recently, several newer diagnostic tools have become available. The American and European Neurogastroenterology and Motility Societies undertook this review to provide guidelines on the indications and optimal methods for the use of transit measurements in clinical practice. This was based on evidence of validation including performance characteristics, clinical significance, and strengths of various techniques. The tests include measurements of: gastric emptying with scintigraphy, wireless motility capsule, and (13)C breath tests; small bowel transit with breath tests, scintigraphy, and wireless motility capsule; and colonic transit with radioopaque markers, wireless motility capsule, and scintigraphy. Based on the evidence, consensus recommendations are provided for each technique and for the evaluations of regional and whole gut transit. In summary, tests of gastrointestinal transit are available and useful in the evaluation of patients with symptoms suggestive of gastrointestinal dysmotility, since they can provide objective diagnosis and a rational approach to patient management.

Technical advances in monitoring human motility patterns

Abnormal motor patterns are implicated in many motility disorders. However, for many regions of the gut, our knowledge of normal and abnormal motility behaviors and mechanisms remains incomplete. There have been many recent advances in the development of techniques to increase our knowledge of gastrointestinal motility, some readily available while others remain confined to research centers. This review highlights a range of these recent developments and examines their potential to help diagnose and guide treatment for motility disorders.

Gastrointestinal targets of appetite regulation in humans

The aim of this paper is to describe and discuss relevant aspects of the assessment of physiological functions - and related biomarkers - implicated in the regulation of appetite in humans. A short introduction provides the background and the present state of biomarker research as related to satiety and appetite. The main focus of the paper is on the gastrointestinal tract and its functions and biomarkers related to appetite for which sufficient data are available in human studies. The first section describes how gastric emptying, stomach distension and gut motility influence appetite; the second part describes how selected gastrointestinal peptides are involved in the control of satiety and appetite (ghrelin, cholecystokinin, glucagon-like peptide, peptide tyrosin-tyrosin) and can be used as potential biomarkers. For both sections, methodological aspects (adequacy, accuracy and limitation of the methods) are described. The last section focuses on new developments in techniques and methods for the assessment of physiological targets involved in appetite regulation (including brain imaging, interesting new experimental approaches, targets and markers). The conclusion estimates the relevance of selected biomarkers as representative markers of appetite regulation, in view of the current state of the art.

Bed rest in health and critical illness: a body systems approach

Bed rest is a common intervention for critically ill adults. Associated with both benefits and adverse effects, bed rest is undergoing increasing scrutiny as a therapeutic option in the intensive care unit. Bed rest has molecular and systemic effects, ultimately affecting functional outcomes in healthy individuals as well as in those with acute and critical illnesses. Using empirical sources, the purpose of this article was to describe the consequences of bed rest and immobility, especially consequences with implications for critically ill adults in the intensive care unit. This review uses body systems to cluster classic and current results of bed rest studies, beginning with cardiovascular and including pulmonary, renal, skin, nervous, immune, gastrointestinal/ metabolic, and skeletal systems. It concludes with effects on muscles, a system profoundly affected by immobility and bed rest.

Magnetic resonance imaging in the evaluation of the gastric emptying and antral motion: feasibility and reproducibility of a fast not invasive technique

PURPOSE

The aim of this study was to evaluate reproducibility of a fast MRI protocol to measure gastric emptying and motility of the gastric antrum.

METHODS AND MATERIALS

Gastric emptying and antral speed were measured in 12 type 1 diabetic patients (mean age 43 years) and 9 healthy volunteers (mean age 31 years). Subjects, fasting from 6h, were evaluated in supine position using a 1.5T MR scanner and a eight-channels phased-array body coil after ingestion of 400 ml of a vanillas pudding mixed with 5 ml of Gd-DTPA. Axial 3D T1w sequence at 0 and 30 min for volume evaluation and cine-steady state acquisition every 5 min for a total time of 30 min for gastric wave speed assessing were acquired. Two blinded observers extrapolated T(1/2) from gastric volume assessment and speed of gastric waves.

RESULTS

All the patients tolerated the examination. The T(1/2) cut-off was of 115 min with an accuracy in differentiate controls from diabetics of 96% (95% CI 0.766-0.992; p<0.001), while the antral speed cut-off was of 0.15 mm/s with an accuracy of 87% (95% CI 0.628-0.977; p<0.001). The inter-observer agreement for the volumes at time 0 and 30 min was respectively 0.983 (95% CI 0.9628-0.9929; p<0.001) and 0.9933 (95% CI 0.9847-0.9971; p<0.001) with an agreement of 0.9918 (95% CI 0.9853-0.9954; p<0.001), while for antral speed it was of 0.935 (95% CI 0.9097-0.9528; p<0.001).

CONCLUSIONS

MRI is a reproducible technique for the evaluation of gastric emptying and antral motility.

Influence of posture on pharmacokinetics

INTRODUCTION

Body position may influence physiological characteristics, such as perfusion, gastrointestinal function and plasma volume. These characteristics may interact with key factors determining the pharmacokinetics of drugs (dissolution, absorption, distribution, metabolism, excretion).

OBJECTIVES

Based on a systematic literature search, current data on the effect of posture on physiological characteristics and/or pharmacokinetics are summarized, and the relevance of possible effects, such as those presenting in clinical practice and clinical pharmacokinetic studies, is assessed.

RESULTS

Postures which favour rapid gastric emptying (sitting, standing, recumbent right) accelerate the absorption of orally administered drugs. Consequently, these postures favour a shorter time to reach peak plasma drug concentration (t(max)) and a higher maximum plasma drug concentration (C(max)) and--in the case of transient saturation of first-pass metabolism--total exposure (area under the concentration-time curve, AUC) in comparison to recumbent left and supine positions (e.g. nifedipine: AUC 30 and 38% higher in standing and right lateral position vs. left lateral position; C(max) 149 and 80% higher, respectively). The magnitude of these postural effects depends strongly on the nature and amount of liquids and food ingested before drug administration and is most pronounced in the fasting state and after administration with a nonnutrient liquid. Changes in splanchnic-hepatic blood flow (e.g. reduction of estimated hepatic perfusion by 37% in standing vs. supine position) may substantially affect the metabolism of orally administered drugs, especially of those with a high/saturable first-pass metabolism. For highly protein-bound drugs (e.g. phenytoin, imipramine), the total plasma concentration has been found to be approximately 10% higher in standing than lying subjects due to changes in plasma volume.

CONCLUSIONS

Positioning of a patient may be an effective method of enhancing or retarding absorption of some drugs in appropriate clinical situations (e.g. toxic ingestions, bedridden patients). In clinical pharmacokinetic trials, such as bioequivalence studies, defining and maintaining posture precisely is a useful approach for reducing within- and between-subject variability.

Disintegration of solid foods in human stomach

Knowledge of the disintegration of solid foods in human stomach is essential to assess the bioavailability of nutrients in the gastrointestinal (GI) tract. A comprehensive review of food gastric digestion, focusing on disintegration of solid foods, is presented. Most of the research reviewed in this paper is contained in the medical, pharmaceutical, food, and nutritional literature. Stomach physiology is briefly introduced, including composition and rheological properties of gastric contents, stomach wall motility in fed/fasted states, and hydrodynamic and mechanical forces that act on the ingested food. In vivo and in vitro methods used for studying food and drug digestion in GI are summarized. Stomach emptying rate, which controls the rate of absorption of nutrients, is highly related to the disintegration of foods. This topic is highlighted with focus on the important mechanisms and the influence of chemical and physical properties of foods. Future research in this area is identified to increase our fundamental understanding of the food digestion process in the stomach as related to the food composition, material properties such as texture and microstructure, and chemical characteristics. This information is necessary to develop new guidelines for seeking innovative processing methods to manufacture foods specifically targeted for health.

Review article: The diagnosis and management of gastroparesis

BACKGROUND

Gastroparesis is a disorder characterized by a delay in gastric emptying of a meal in the absence of a mechanical gastric outlet obstruction.

AIM

To provide an evidence based overview on diagnosis and management of gastroparesis.

METHODS

A PubMed search was performed using search terms including gastroparesis, gastric retention, gastric emptying, accommodation, manometry, prokinetics, antiemetics, metoclopramide, domperidone, erythromycin, botulinum toxin, gastric pacing. Relevant studies were identified and original articles and reviews were collected. References in these articles were examined for relevance and included where appropriate.

RESULTS

Diagnosis of gastroparesis is based on the presence of symptoms such as nausea, vomiting and postprandial abdominal fullness and on an objectively determined delay in gastric emptying. The true prevalence of gastroparesis is unknown. Gastric emptying can be assessed by scintigraphy and stable isotope breath tests. Management of gastroparesis consists of dietary and lifestyle measures and/or pharmacological interventions (prokinetics, antiemetics, intrapyloric botulinum toxin injection) or other interventions that focus on adequate nutrient intake either through a nasoduodenal tube, percutaneous gastrostomy or jejunostomy.

CONCLUSIONS

Accurate diagnosis of gastroparesis requires an adequate protocol to measure gastric emptying. Treatment options in gastroparesis remain limited despite the disabling nature of the disorder.