Evaluation of vitamin A absorption by using oil-soluble and water-miscible vitamin A preparations in normal adults and in patients with gastrointestinal disease

Exocrine pancreatic insufficiency in type 1 and type 2 diabetes mellitus: do we need to treat it? A systematic review

The exocrine and endocrine pancreata are very closely linked both anatomically and physiologically. Abdominal symptoms such as nausea, bloating, diarrhea, steatorrhea, and weight loss can often occur in diabetic patients. Impairments of the exocrine pancreatic function seem to be a frequent complication of diabetes mellitus; however, they are largely overlooked. The aim of this paper is to provide an overview of the current concepts of exocrine pancreatic insufficiency (PEI) in diabetes mellitus. The prevalence and symptoms of PEI in diabetes mellitus, the pathomechanism, and difficulties of diagnosis and therapy of PEI are summarized in this systematic review.

Effect of low energy diet for eight weeks to adults with overweight or obesity on folate, retinol, vitamin B12, D and E status and the degree of inflammation: a post hoc analysis of a randomized intervention trial

Background

Obesity is associated with vitamin insufficiency and low grade inflammation. The purpose of this study was to investigate the effect of weight loss on folate, retinol, vitamin B₁₂, D and E status and the degree of inflammation.

Methods

Out of 110, 85 individuals (75% women) aged 39 ± 11 years with a mean ± SD BMI of 33 ± 4 kg/m², completed an eight-week low energy diet (LED). Serum concentration of folate, retinol, B₁₂, D and E and C-reactive protein and homocysteine (Hcy) were measured at baseline and at end of the LED.

Results

At baseline, 8% of the participants were deficient in folate, 13% in vitamin B₁₂, 2% in retinol, 28% in vitamin D (72% were insufficient in vitamin D), and none were deficient in vitamin E. At baseline, BMI was inversely associated with retinol (P < 0.05) as was total and abdominal fat percentage with folate (P < 0.05); further BMI and measures of adiposity were positively associated with CRP (P < 0.01) and Hcy (P < 0.05). Homocysteine was inversely associated with all vitamins but retinol (P < 0.001). After the LED, the participants lost a mean [95% confidence intervals] of 12.3 [− 13.1,-11.6] kg. The serum concentration of folate, vitamin B₁₂ and D were increased (P < 0.001) after the LED whereas the concentration of retinol and vitamin E were reduced (P < 0.001).

Conclusion

Eight-weeks LED resulted in 13% weight loss and an increase in the serum concentrations of folate, vitamin B₁₂ and D. Baseline adiposity was inversely associated with folate and retinol, and positively associated with markers of inflammation.

Trial registration

Ethical Committee of Copenhagen as no. H-4-2013-135, NCT01561131.

Vitamin A and Carotenoid Toxicity

Large differences in time and dose needed to induce hypervitaminosis A have been observed. High doses of vitamin A in food and oily solutions are well tolerated, whereas emulsified preparations have higher toxicity. Chronic hypervitaminosis seems to be induced following daily doses of 300,000 to 600,000 IU of vitamin A (90–180 mg of retinol) in oily preparations for many months or years, whereas teratogenicity may be induced by daily doses as low as 40,000 IU of vitamin A (12 mg of retinol) in oil during the first trimester. for the provitamin A, β-carotene, serious adverse effects have been reported in large-scale prospective randomized trials: four years of supplementation with 20 to 30 mg β-carotene per day was associated with increased risk of lung cancer and cardiovascular disease among smokers and workers exposed to asbestos. These results strongly suggest that high doses of β-carotene should not be recommended for any group until the safety of such doses can be established.

A novel method to identify fat malabsorption: the Serum Retinyl Palmitate Test

BACKGROUND

Malabsorptive etiologies of chronic diarrhea are important to identify. The 72-h stool for fecal fat test (FFT), the gold standard for diagnosing fat malabsorption, is fraught with limitations that impact its reliability. Vitamin A, a fat-soluble vitamin, parallels the absorption of lipids. We assessed the feasibility and validate a novel clinical test, retinyl palmitate (RP), for the diagnosis of fat malabsorption, and to compare the results to the FFT.

METHODS

Using a case-control study design, patients with chronic diarrhea secondary to suspected malabsorption, and healthy control subjects were identified. A Dietitian taught subjects to consume a 100g fat diet for the FFT with measurements of stool fat after 72-h. Serum levels of Vitamin A (retinol) and RP were measured by reversed-phase high pressure liquid chomatography. Two-way comparisons were made between the groups using 2 sample Wilcoxon rank-sum tests.

RESULTS

Sixteen patients completed this study (8 cases and 8 control subjects). Fecal fat results were available for 15/16 patients. The sensitivity of the FFT was 100% (identified all cases), but the FFT specificity was 42%, as 4/7 control patients were identified as malabsorbers. Cases with short bowel syndrome had the lowest RP levels but this did not meet statistical significance. There was no significant difference for serum RP levels when comparing cases and control patients' AUC.

CONCLUSIONS

Serum RP is useful to identify malabsorption, albeit in severe cases. Furthermore, we have shown that the 72-hour FFT has poor performance characteristics, highlighting the need for more useful diagnostics in identifying malabsorption.

The Spanish Pancreatic Club's recommendations for the diagnosis and treatment of chronic pancreatitis: part 2 (treatment)

Chronic pancreatitis (CP) is a complex disease with a wide range of clinical manifestations. This range comprises from asymptomatic patients to patients with disabling symptoms or complications. The management of CP is frequently different between geographic areas and even medical centers. This is due to the paucity of high quality studies and clinical practice guidelines regarding its diagnosis and treatment. The aim of the Spanish Pancreatic Club was to give current evidence-based recommendations for the management of CP. Two coordinators chose a multidisciplinary panel of 24 experts on this disease. These experts were selected according to clinical and research experience in CP. A list of questions was made and two experts reviewed each question. A draft was later produced and discussed with the entire panel of experts in a face-to-face meeting. The level of evidence was based on the ratings given by the Oxford Centre for Evidence-Based Medicine. In the second part of the consensus, recommendations were given regarding the management of pain, pseudocysts, duodenal and biliary stenosis, pancreatic fistula and ascites, left portal hypertension, diabetes mellitus, exocrine pancreatic insufficiency, and nutritional support in CP.

Serum retinol, alpha-tocopherol and systemic inflammatory response in metastatic colorectal carcinoma patients treated with combination chemotherapy and cetuximab

Cetuximab is a chimeric antibody registered for the therapy of advanced colorectal carcinoma. Cancer and anticancer therapy are associated with oxidative stress, and disorders of antioxidant balance may be involved in the toxicity associated with anticancer treatment. The aim of the present study was to investigate the changes of serum retinol, alpha-tocopherol and C-reactive protein during the first month of treatment with cetuximab and chemotherapy. Twenty-five consecutive patients with metastatic colorectal carcinoma treated with a combination of chemotherapy and cetuximab were included in the present study. Serum retinol and alpha-tocopherol were determined by high-performance liquid chromatography and serum C-reactive protein was determined using commercial kits. Significant correlation was observed between baseline concentrations of retinol and C-reactive protein (r(s)=-0.54, p<0.01). Median survival of patients who had baseline serum retinol below 1.25 µmol/L was 10 mo compared to 18 mo for patients who had serum retinol equal or above 1.25 µmol/L (p<0.05); median survival of patients who had serum C-reactive protein below 24 mg/L was significantly longer compared to patients with C-reactive protein levels equal or above 24 mg/L (18 vs. 7 mo, p<0.05), but no difference in survival was observed based on alpha-tocopherol levels. Twenty-two patients had evaluation of retinol, alpha-tocopherol and C-reactive protein at least once during the follow up. Serum concentration of alpha-tocopherol decreased significantly during the therapy, but retinol and C-reactive protein concentrations remained unchanged. In conclusion, a significant correlation was observed between serum retinol and C-reactive protein. Serum alpha-tocopherol decreased significantly during the first month of combination therapy with cetuximab. Low retinol and high C-reactive protein concentrations were predictive of poor prognosis in this patient population.

Evaluation of vehicle substances on vitamin D bioavailability: a systematic review

Vitamin D insufficiency is a common medical condition. Vitamin supplements can be ingested to improve vitamin D status. It is not known if the vehicle substance that is combined with the vitamin D tablet influences the bioavailability of vitamin D. The purpose of this review is to examine the impact of different vehicles on vitamin D bioavailability. A comprehensive literature search identified studies that directly compared the absorption of vitamin D from two or more vehicles. The change in mean serum 25(OH)D per average daily dose of vitamin D supplemented was calculated and compared among the studies. We identified four clinical studies that compared two different vehicles of vitamin D. Vitamin D in an oil vehicle produced a greater 25(OH)D response than vitamin D in a powder or an ethanol vehicle in healthy subjects. There are limited studies that have compared the influence of the vehicle substance on vitamin D bioavailability. Future studies should examine bioavailability among different vehicle substances such as oil, lactose powder, and ethanol and examine if there are any differences in bioavailability among different patient populations including those with fat malabsorption.

Response Surface Methodology for the Development of Self-Nanoemulsified Drug Delivery System (SNEDDS) of All-Trans-Retinol Acetate

The purpose was to prepare, characterize, and optimize a self-nanoemulsified drug delivery system (SNEDDS) of a model lipophilic compound, all-trans-retinol acetate. As part of the optimization process, the main effects, interaction effects, and quadratic effects of the formulation ingredients were investigated.

METHOD

A three-factor, three-level Box-Behnken design was used to explore the quadratic response surfaces and construct a second-order polynomial model in the form: Y = A + A1X1 + A2X2+ A3X3 + A4X1X2 + A5X2X3 + A6X1X3+ A7X1(2) + A8X2(2) + A9X3(2) + E. Amount of added oil (X1), surfactant (X2), and cosurfactant (X3) were selected as the factors. Particle size (Y1), turbidity (Y2), and cumulative amount of the active ingredient emulsified after 10 (Y3) and 30 (Y4) min were the observed variables. Response surface plots were used to demonstrate the effect of factors (X1), (X2), and (X3) on the response (Y4). Amount of added soybean oil (X1), Cremophor EL (X2), and Capmul MCM-C8 (X3) showed a significant effect on the emulsification rates, as well as on the physical properties of the resultant emulsion (particle size and turbidity). Observed and predicted values of Y4 obtained from the constructed equations were in close agreement. Response surface methodology was then used to predict the levels of factors X1, X2, and X3 under the constrained variables for an optimum response. Applied constraints were 0 < Y1 < 0.5, 1 < Y2 < 20, 60 < Y3 < 80, and 90 < Y4 < 100. The predicted values were 0.0704 microm for particle size (Y1), 18.95 NTU for turbidity (Y2), 88.88% for drug release after 10 min (Y3), and 110.7% drug release after 30 min (Y4). Two new formulations were prepared according to the predicted levels. The observed and predicted values were in close agreement.

Bioavailability assessment of vitamin A self-nanoemulsified drug delivery systems in rats: a comparative study

OBJECTIVES

To assess and compare the bioavailability of three different oral dosage forms of vitamin A in rats. The formulations included vitamin A self-nanoemulsified drug delivery (SNEDD) optimized formulation-filled capsule (F1), vitamin A SNEDD optimized formulation compressed tablet (F2) and vitamin A oily solution-filled capsules without any additives (control, F3).

MATERIALS AND METHODS

Bioavailability was assessed after a single oral dose of the three formulations using three groups of rats, each group comprising 6 rats. Blood samples were collected at baseline and over the next 8 h. Plasma was separated and extracted to obtain the drug, which was measured by HPLC. Statistical data analysis was performed using the Student t test and ANOVA with p < 0.05 as the minimal level of significance.

RESULTS

From the pharmacokinetic parameters, both F1 and F2 showed improved bioavailability compared to F3. The values of AUC +/- SD were 3,080.7 +/- 190.2, 2,137.1 +/- 130.5 and 1,485.2 +/- 80.1 ng x h/ml for F1, F2 and F3, respectively. The Tmax was 1 h in case of F1 and F2 as compared to 1.5 h for F3. The Cmax +/- SD was 799.5 +/- 48.5, 656.2 +/- 64.4 and 425.8 +/- 33.1 for F1, F2 and F3, respectively. The increase in AUC, Cmax and Tmax was significant (p < 0.05). The bioavailability calculated from the AUC for F1 and F2 relative to F3 was 207.4 and 143.8%, respectively. The bioavailability increased almost twofold and 1.4 times for F1 and F2, respectively.

CONCLUSIONS

The study showed that the newly developed vitamin A SNEDD formulations increased the rate and extent of drug absorption compared to the oily drug solution. The present investigation demonstrated that vitamin A SNEDD optimized formulations, either as filled capsules or as compressed tablets, were superior to its oily solution with regard to their biopharmaceutical characteristics.

Development and validation of a liquid chromatography method for the simultaneous determination of α-tocopherol, retinol and retinyl esters in human serum using a monolithic column for the monitoring of anticancer therapy side effects

Among other side effects, administration of anticancer agents is accompanied by manifestations of gastrointestinal toxicity and disturbances of antioxidant balance. The monitoring of these toxic effects in clinical practice is impeded by a dearth of reliable laboratory methods. Therefore, a simple and rapid reversed-phase high-performance liquid chromatography procedure for selective and sensitive determination of retinol, a-tocopherol, and retinyl esters (retinyl-palmitate and retinyl-stearate) in blood serum has been developed and presented in this study. A Series 200 LC HPLC instrument from Perkin Elmer (Norwalk, USA) with diode-array detector (DAD) was used for the analysis. Separations of retinol, alpha-tocopherol, retinyl-palmitate, and retinyl-stearate were performed using a Chromolith Performance RP-18e, 100 x 4.6 mm monolithic column from Merck (Darmstadt, Germany). Gradient elution was used at a flow rate of 3 mL/min; the mobile phase was methanol-water (95:5, v/v) for 0-2.1 min and methanol-2-propanol (60:40, v/v) for 2.1-4.9 min. The total time of analysis was 6 min. The injection volume was 20 microL and the analysis was performed at ambient temperature. Detection of retinol, alpha-tocopherol, and retinyl esters was carried out at 325, 295, and 330 nm, respectively. For practical assessment of the method, the vitamin A absorption test was performed on seven healthy controls as well as on six patients with non-small cell lung carcinoma or head and neck carcinoma previously treated by chemotherapy and/or radiotherapy, six patients with rectal carcinoma before chemoradiotherapy, four patients with gastrointestinal stromal tumor (GIST) before treatment with imatinib, and a breast cancer patient with chemotherapy-induced diarrhea. Present data demonstrate the feasibility of large scale HPLC determination of vitamin E, vitamin A, and retinyl esters in human serum using a silica monolithic column, and this method may represent a valuable aid in the laboratory monitoring of the toxicity of anticancer therapy.

Preparation and in vitro characterization of self-nanoemulsified drug delivery system (SNEDDS) of all-trans-retinol acetate

PURPOSE

To prepare a self-nanoemulsified drug delivery system (SNEDDS) of all-trans-retinol acetate, with enhanced dissolution and better chance of oral absorption.

METHOD

All-trans-retinol acetate SNEDDS was prepared using different concentrations of soybean oil (solvent) Cremophor EL (surfactant) and Capmul MCM-C8 (co-surfactant). Particle size and turbidity of the SNEDDS were determined after adding water to the oily solution. Dissolution profile of SNEDDS filled in hydroxyl propyl methyl cellulose (HPMC) capsules was determined by using water in USP apparatus 2. Ternary phase diagrams were constructed to identify the self-nanoemulsified region. The SNEDDS were evaluated by the visual observation, turbidity in nephrometric turbidity units (NTU), mean particle size (microm) and Fourier transformed-infrared spectroscopy (FT-IR). SNEDDS were thermally characterized using differential scanning calorimetry (DSC) to ensure the compatibility of the SNEDDS ingredient.

RESULTS

From the data obtained in this work, it was clear that surfactant to co-surfactant ratio has the main impact on the physical characteristics of the emulsion formed. The optimum surfactant to co-surfactant ratio was found to be 2:1 (37.5-50% for Cremophor EL, and 18.75-25% for Capmul MCM-C8). With this ratio, the resultant nanoemulsions obtained have a particle size range of 0.103-0.051 microm, turbidity range of 18.12-2.18 NTU and t30 values (cumulative% all-trans-retinol acetate dissolved in 30 min) of 90.42-99.5. Also the thermograms obtained from DSC experiments showed that there is no incompatibility or interaction between the SNEDDS ingredients (soybean oil, Cremophor EL, and Capmul MCM-C8) and all-trans-retinol acetate.

CONCLUSION

The present study revealed that the self-nanoemulsified drug delivery system of all-trans-retinol acetate increased its dissolution rate and has the potential to enhance its bioavailability without interaction or incompatibility between the ingredients.

Water-miscible, emulsified, and solid forms of retinol supplements are more toxic than oil-based preparations

BACKGROUND

It is well established that an excessive intake of retinol (vitamin A) is toxic; however, it has been > 25 y since the last extensive treatise of case reports on this subject.

OBJECTIVE

The objectives were to identify and evaluate all individual cases of retinol toxicity published in the scientific literature that assessed the thresholds and symptoms induced by high intakes of retinol and to compare the toxicity of different physical forms of retinol preparations.

DESIGN

We performed a meta-analysis of case reports on toxicity claimed to be induced by intakes of excessive amounts of dietary retinol (ie, retinol and retinyl esters in foods or supplements). Using free text and MESH (medical subheading) strategies in PubMed, we identified 248 articles in the scientific literature. From these initial articles we identified other relevant citations. The final database consisted of 259 cases in which individual data on dose, sex, age, time of exposure, and symptoms are reported.

RESULTS

Chronic hypervitaminosis A is induced after daily doses of 2 mg retinol/kg in oil-based preparations for many months or years. In contrast, doses as low as 0.2 mg retinol. kg(-1). d(-1) in water-miscible, emulsified, and solid preparations for only a few weeks caused chronic hypervitaminosis A. Thus, water-miscible, emulsified, and solid preparations of retinol are approximately 10 times as toxic as are oil-based retinol preparations. The safe upper single dose of retinol in oil or liver seems to be approximately 4-6 mg/kg body wt. These thresholds do not vary considerably with age.

CONCLUSIONS

The results of the present study indicate that the physical form of retinol supplements is a major determinant of toxicity. The use of water-miscible, emulsified, and solid preparations of retinol should therefore be carefully considered before being used in supplements and fortifications.

Vitamin A supplementation and childhood morbidity from diarrhea and respiratory infections: a meta-analysis

OBJECTIVES

To perform an updated meta-analysis of the effect of vitamin A supplementation on childhood morbidity from respiratory tract infections and diarrhea. Study design A comprehensive search of the 1966 to 2000 MEDLINE database and review of the reference lists of relevant articles identified 9 randomized controlled trials dealing with morbidity from respiratory infections and diarrhea in children 6 months to 7 years of age and provided "intention-to-treat" data.

RESULTS

The combined results indicated that vitamin A supplementation has no consistent overall protective effect on the incidence of diarrhea (relative risk, 1.00; 95% CI, 0.94-1.07) and that it slightly increases the incidence of respiratory tract infections (relative risk, 1.08; 95% CI, 1.05-1.11).

CONCLUSIONS

High-dose vitamin A supplements are not recommended on a routine basis for all preschool children and should be offered only to individuals or populations with vitamin A deficiency.

Use of water-miscible retinyl palmitate as markers of chylomicrons gives earlier peak response of plasma retinyl esters compared with oil-soluble retinyl palmitate

Delayed peak response of plasma retinyl esters (RE) relative to plasma triacylglycerols (TAG) and apolipoprotein (Apo) B-48 responses following a fat load supplemented with vitamin A raised doubts about the use of vitamin A to label dietary-derived lipids and lipoproteins. The present study compared the use of water-miscible and oil-soluble retinyl palmitate (RP) as markers of dietary-derived lipoproteins in healthy subjects along with the measurements of postprandial plasma TAG and ApoB-48 responses to investigate whether the delayed peak response observed was due to delayed intestinal output of RE from oil-based solutions. Nine healthy female subjects were given a standard test meal containing a dose (112 mg) of RP in either water-miscible or oil-soluble form in random order, on two separate occasions after a 12 h overnight fast. The results showed that the mean plasma RE concentrations reached a peak significantly later than mean plasma TAG and ApoB-48 concentrations when oil-soluble RP was consumed, whereas plasma RE peaked earlier relative to plasma TAG and ApoB-48 responses when water-miscible RP was used. The results suggested a more rapid absorption with a significantly higher and earlier peak response of plasma RE when water-miscible RP was consumed. This was in contrast to the delayed initial appearance and later sustained higher concentrations of plasma RE during the late postprandial period when oil-soluble RP was consumed. The RE response to the water-miscible RP showed better concordance with plasma TAG response than that of oil-soluble RP.

Impaired bioavailability of vitamin A in adults and children with persistent diarrhoea in Zambia

BACKGROUND

We have previously demonstrated a strong relationship between low serum retinol concentration and mortality in Zambian AIDS patients with diarrhoea, but were unable to detect any benefit from oral micronutrient supplementation.

AIM

To test the hypothesis that this is related to impaired availability of vitamin A, we analysed serum retinol concentration changes over 6 h following oral mega-dose therapy (60, 120 or 180 mg retinol).

METHODS

Twenty-four men without diarrhoea, 15 adults with persistent diarrhoea and 11 children (six girls, five boys) with persistent diarrhoea were studied.

RESULTS

Men with persistent diarrhoea had lower baseline serum retinol concentrations (median 0.39 micromol/L, interquartile range 0.21-0.56) than controls (median 1.16 micromol/L, interquartile range 0.84-1.47; P=0.0003). After 60 mg retinol, the rise in serum retinol in HIV seropositive controls (median 0.63 micromol/L, interquartile range 0.35-0.77) did not differ significantly from that observed in HIV seronegative controls (median 0.35 micromol/L, interquartile range - 0.04-0.56; P=0.20). Increasing the dose to 120 mg or 180 mg retinol did not enhance the increase in serum retinol concentration. The increase in serum retinol was less in adults with persistent diarrhoea (median 0.25 micromol/L, interquartile range 0.04-0.35) and in children (median 0.11 micromol/L, interquartile range 0.04-0.46) than in men without diarrhoea (median 0.44 micromol/L, interquartile range 0.26-0.74; P=0.03). Adults and children with diarrhoea had greater losses of retinol in urine over a 24-h period than controls, but less than 1% of the ingested dose was excreted.

CONCLUSIONS

These results suggest that persistent diarrhoea in this population is associated with reduced bioavailability of retinol. Further work is required to determine the metabolic fate of therapeutic doses of retinol and to determine appropriate replacement strategies for HIV infected individuals.

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.

Adverse effects of high-dose vitamin A supplements in children hospitalized with pneumonia

OBJECTIVE

To test the hypothesis that high-dose vitamin A supplements will enhance recovery of children hospitalized for the treatment of community-acquired pneumonia.

DESIGN

We conducted a randomized, double-blind, placebo-controlled clinical trial of high-dose vitamin A supplements among children 3 months to 10 years of age (N = 95) admitted to hospital with community-acquired pneumonia in Lima, Peru. Children </=1 year of age received 100 000 IU of water-miscible vitamin A on admission to the hospital and an additional 50 000 IU the next day. Children >1 year of age received 200 000 IU on admission and 100 000 IU the next day.

RESULTS

Children receiving vitamin A (n = 48) had lower blood oxygen saturation (the mean difference on day 3 in hospital was 1.1%), higher prevalence rates of retractions (37% in the vitamin A group vs 15% in the placebo group on day 3), auscultatory evidence of consolidation (28% in the vitamin A group vs 17% in the placebo group on day 3), and were more likely to require supplemental oxygen (21% in the vitamin A group vs 8% in the placebo group on day 3) than children in the placebo group (n = 47). Adjustment for baseline severity of disease and nutritional status did not alter the association of vitamin A with increased clinical severity, although the difference in blood oxygen saturation was no longer statistically significant. No differences were seen in duration of hospitalization or in chest x-ray changes 14 days after admission. No deaths occurred, and toxicity of vitamin A was not seen.

CONCLUSIONS

This study indicates that high-dose vitamin A supplements cause modest adverse effects in children recovering from pneumonia and should not be used therapeutically in such patients unless there is clinical evidence of vitamin A deficiency or concurrent measles infection.

Olestra ingestion and retinyl palmitate absorption in humans

This study examined the effect of olestra, a zero-calorie fat replacement, on the absorption of retinyl palmitate in humans. After a 30-d adaptation period during which they consumed 10 g olestra/d in potato chips under free-living conditions, 68 healthy male subjects were housed in a metabolic ward and given a single dose of retinyl palmitate (0.33 RDA) containing a trace amount of 3H-retinyl palmitate with a breakfast that contained 0, 8, 20 or 32 g of olestra and about 38 g of triglyceride. Blood was collected at defined intervals for 48 h and plasma analyzed for 3H-retinyl esters by HPLC and liquid scintillation spectrometry. There was no significant effect on retinyl palmitate absorption as determined from the area under the plasma 3H-retinyl esters concentration-time curve. However, an area under the plasma concentration-time curve in the 32-g olestra group that was 81% (mean value) or 70% (median value) of the area under the curve for the placebo group suggested that olestra may have affected retinyl palmitate absorption. Inclusion or exclusion of 13 high responders did not change the results.

Clearance of postprandial lipoproteins in normolipemics: role of the apolipoprotein E phenotype

The hepatic clearance of triglyceride-rich lipoproteins is mediated via apolipoprotein (apo) E which occurs in three common isoforms, apoE2, apoE3 and apoE4. To study the importance of the apoE isoforms on the response curves of different triglyceride-rich lipoproteins and the effect of chylomicron remnants on the composition of HDL, 37 normolipemics were investigated after a standardized fatty meal (8 apoE2/E2, 8 apoE2/E3, 8 apoE3/E3, 7 apoE3/E4 and 6 apoE4/E4). These individuals were matched for age, body mass index, fasting triglycerides, HDL-cholesterol, and apoA-I. A delayed chylomicron remnant clearance was observed only in apoE2 homozygotes, and this delay was neither correlated with fasting lip ds nor with peak lipoprotein concentrations. In apoE2/E3 heterozygotes, in contrast, the defective isoform E2 appears to be compensated for by the normal apoE isoform E3. In non-apo-E2/E2 individuals, the chylomicron remnant response was highly correlated with the magnitude of chylomicron and VLDL responses, with fasting triglycerides, and with the triglycerides enrichment and cholesterol depletion of HDL. These correlations were not observed in apoE2/E2. From these results we conclude that the chylomicron remnant response curve is an indicator of the extent of postprandial lipemia in non-apoE2/E2 individuals only.

The effect of orlistat, an inhibitor of dietary fat absorption, on the absorption of vitamins A and E in healthy volunteers

An open-label, placebo-controlled, randomized, two-way crossover study was performed in 12 healthy volunteers (between 20 and 44 years of age) to assess the effect of orlistat, a gastrointestinal lipase inhibitor that reduces dietary fat absorption and is being developed for weight control in obesity, on the absorption of vitamins A and E. Each participant received a single oral dose of 25,000 IU vitamin A followed 24 hours later by a single oral dose of 400 IU vitamin E on two separate occasions: during oral administration of 120 mg orlistat or placebo three times daily for 9 days. The two treatments were separated by a washout period of at least 2 weeks. Serial blood samples for pharmacokinetic analysis were collected at specified times over 24 hours after each dose of vitamin A for determination of serum concentrations of retinol, and over a period of 5 days after each dose of vitamin E for determination of serum concentrations of alpha-tocopherol, total cholesterol, and triglycerides. Orlistat significantly reduced the absorption of vitamin E (approximately 43% according to maximum concentration and approximately 60% according to area under the concentration-time curve), but not that of vitamin A, at the dose levels studied. The results of this study will aid in the implementation of a vitamin supplementation strategy, should vitamin deficiency occur in patients undergoing orlistat therapy.