Processing of vitamin A and E in the human gastrointestinal tract

We aimed to provide basic data on the processing of vitamin A and E in the human gastrointestinal tract and to assess whether the size of emulsion fat globules affects the bioavailability of these vitamins. Eight healthy men received intragastrically two lipid formulas differing in their fat-globule median diameter (0.7 vs. 10. 1 microm. Formulas provided 28 mg vitamin A as retinyl palmitate and 440 mg vitamin E as all-rac alpha-tocopherol. Vitamins were measured in gastric and duodenal aspirates, as well as in chylomicrons, during the postprandial period. The gastric emptying rate of lipids and vitamin A and E was similar. The free retinol/total vitamin A ratio was not significantly modified in the stomach, whereas it was dramatically increased in the duodenum. The proportion of ingested lipid and vitamins was very similar in the duodenal content. The chylomicron response of lipids and vitamins was not significantly different between the two emulsions. Our main conclusions are as follows: 1) there is no significant metabolism of vitamin A and E in the human stomach, 2) the enzyme(s) present in the duodenal lumen is significantly involved in the hydrolysis of retinyl esters, and 3) the size of emulsion fat globules has no major effect on the overall absorption of vitamin A and E.

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.

Relationships between endosonographic appearan e and clinical or manometric features in patients with achalasia

BACKGROUND

The existence of endosonographic abnormalities of the oesophagus in achalasia is discussed. The place of endoscopic ultrasonography (EUS) needs to be clarified.

PATIENTS

Thirty five untreated patients suffering from achalasia and 28 controls without oesophageal disease were prospectively enrolled since 1993. Pseudoachalasia was diagnosed in two patients.

METHODS

EUS measurements were performed at two opposite sites at the level of the cardia, and 5 cm and 10 cm proximally, avoiding compression by the water filled balloon.

RESULTS

The oesophageal wall and the fourth hypoechoic layer were significantly thicker at the level of the cardia and 5 cm above, with mean differences between patients and controls of 0.37/0.42 mm and 0.16/0.23 mm respectively. No statistically significant correlation could be demonstrated between the thickness of the oesophageal wall or of the fourth hypoechoic layer and weight loss, or the average pressure of the lower oesophageal sphincter. However, a significant inverse relationship was demonstrated between the duration of symptoms and the thickness of the fourth hypoechoic layer. The thickness of the fourth hypoechoic layer was also increased in patients who required only one pneumatic dilatation (P < 0.01).

CONCLUSION

The thickness of the oesophageal wall and of the fourth hypoechoic layer appeared to be significantly increased in achalasia patients. However, the slight increase of the mean size (< 0.5 mm) of the muscularis propria suggests that EUS is not helpful in the diagnosis of achalasia. The physiopathological basis of advanced achalasia has to be reconsidered as we demonstrated an inverse relationship between the duration of symptoms and the thickness of the muscularis propria.

Physicochemical characteristics of emulsions during fat digestion in human stomach and duodenum

Seven fasting subjects were fitted with nasogastric and nasoduodenal tubes and received intragastrically a coarsely emulsified test meal. Gastric and duodenal aspirates were collected after 1, 2, 3, and 4 h. In the duodenum, most lipids (> 90%) were present as emulsified droplets 1-100 microns in size. Large droplets and unemulsified material present in the test meal (> 100 micron) disappeared, whereas smaller droplets (1-50 microns) were generated after 1 h of digestion. Thus the median lipid droplet diameter significantly decreased (19.6 vs. 56.5 microns in the test meal) and the droplet surface area significantly increased (1.58 vs. 0.70 micron2/g fat). Intermediate droplet diameters were 34.3, 46.3, and 27.6 microns after 2, 3, and 4 h, respectively. In the stomach, a comparable emulsion particle size pattern was observed, with median droplet diameters of 17.2, 37.9, 52.4, and 41.6 microns after 1, 2, 3, and 4 h, respectively. However, the extent of triglyceride hydrolysis was much lower in the stomach (6-16%) than in the duodenum (42-45%), where small droplets were enriched in lipolytic products, cholesterol, and phospholipids. The present findings show for the first time that most dietary lipids are present in the human duodenum as emulsified droplets 1-50 microns in size and that no further marked emulsification of dietary fat occurs in the duodenum compared with the stomach.

Characterization of emulsions and lipolysis of dietary lipids in the human stomach

Fasting subjects were intragastrically intubated and received a coarsely emulsified test meal. Gastric aspirates were collected after 1, 2, 3, and 4 h. During digestion in the stomach, unemulsified lipids (> or = 100 microns) represented a minor fraction. A significant amount of the large 70- to 100-microns lipid droplets disappeared, and fine 1- to 10-microns droplets were generated. The median lipid droplet diameter significantly decreased (21.9 vs. 52.9 microns) after 1 h and kept intermediate values for longer periods of time. The emulsion surface area was 100-120 m2/l and was basically provided by 1- to 100-microns droplets. Lipolysis catalyzed by gastric lipase primarily occurred within the first hour of digestion (11.9%). Smaller droplets were enriched in triglyceride lipolytic products. The free fatty acid concentrations were in the range of 5.6-8.2 mM over 1-4 h. The present finding demonstrates for the first time that in the human stomach most dietary lipids are present in the form of emulsified droplets, in the range of 20-40 microns, and that gastric lipolysis can help to increase emulsification in the stomach.

[Treatment of achalasia by pneumatic dilatation]

Between 1979 and 1988, 60 patients with achalasia were treated by pneumatic dilatation under general anaesthesia, using the Rider-Moeller apparatus. The diagnosis rested on clinical, radiological, manometric and endoscopic criteria. These 60 patients underwent a total of 99 dilatations: 63.3 per cent were dilated once and 37.7 per cent were dilated several times. Forty seven of the 60 patients were followed up for more than 12 months (mean: 44 months): 2 of them (4.2 per cent) had to be operated upon, while 45 (95.7 per cent) are asymptomatic. Immediate complications were perforation in one case and cardial fissure in another; both were treated medically and cured. There was no oesophagitis or peptic stenosis, and no patient died. These results are compared with those found in the literature. The authors underline the simplicity, safety and effectiveness of pneumatic dilatation and suggest that it should be used as first-line treatment of achalasia, surgery being performed only when dilatation fails.

Ventilatory effects of domperidone, a new dopamine antagonist, in anaesthetized rabbits

The ventilatory effects of domperidone (DP), a dopamine antagonist that does not cross the blood-brain barrier, were studied on rabbits anaesthetized with pentobarbitone. DP induced hyperventilation (+20%), which was not dose-dependent, without any marked change in arterial blood gases. This effect was abolished by previous transection of both carotid sinus nerves. On an average, steady state hypoxia (PaO2 approximately 45 mmHg for 5 min) doubled ventilation before, and increased itself threefold after DP (0.10 mg kg-1 i.v.). Prazosin (PZ, 0.1 mg kg-1 i.v.), an alpha 1-adrenoceptor antagonist, induced hyperventilation (+16%) but decreased systemic arterial blood pressure. PZ did not modify the ventilatory response to steady state hypoxia. In short, DP has a slight stimulating effect on resting ventilation and potentiates the ventilatory response to steady state hypoxia. This last effect would not depend on additional alpha 1-adrenoceptor antagonism of DP, as PZ does not change the ventilatory response to hypoxia.

[Chronic atrophic polychondritis. Report of three cases, with ultrastructural study by electron microscopy]

The authors report 3 cases of chronic atrophic polychondritis with clinical signs characteristic of the disease. The 3 patients had deafness of perceptive type, very severe in one case. In one case, the relationship between inflammatory rheumatism and rheumatoid arthritis is discussed. The 3 cases include a pathological study under the electron microscope of the cartilage of the ear. Certain ultrastructural peculiarities observed (dense perichondrocyte granules) are compared with the data in the literature.

[The curve of the intraventricular pressure-volume relationships is not mono-exponential]

The graphic and statistic investigations have let us to assert that the right ventricular P/V relationship's curve is characterized by two successive segments: linear and exponential respectively. We have proposed an interpretation based on Roach's and Burton's works. Interest of information about this curve is double: 1) it is a function of the ventricular cavity volume; 2) it gives a general idea about the mode of ventricular filling.