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Biomedical subjects

D Lairon

Publications and source records attributed to D Lairon.

At least 37 records · Page 2Linked to original sources
PubMed1999

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.

Absorption↗
PubMed1999

Flavonoids in food and natural antioxidants in wine.

Plant foodstuffs are an important source of a wide variety of flavonoids with protective properties on low-density lipoprotein oxidation as shown in vitro and in some human and animal experiments. Increasing information is available concerning the absorption and pharmacokinetics of these molecules, but their long-term protective effect on coronary heart disease still needs further investigation.

Antioxidants↗
PubMed1999

Influence of obesity and body fat distribution on postprandial lipemia and triglyceride-rich lipoproteins in adult women.

We know that upper body obesity is associated with metabolic complications, but we don't know how regional body fat distribution influences postprandial lipemia in obese adults. Thus, this study explored the respective effects of android or gynoid types of obesity and fasting triglyceridemia on postprandial lipid metabolism and especially triglyceride-rich lipoproteins. Twenty-four obese and 6 lean normotriglyceridemic women (control), age 24-57 yr, were enrolled. Among obese women with an android phenotype, 9 exhibited normal plasma triglyceride levels (mean: 1.38 mmol/L) (NTAO), and 7 displayed a frank hypertriglyceridemia (mean: 2.40 mmol/L) (HTAO). The 8 patients with a gynoid phenotype had normal triglyceride levels (mean: 1.00 mmol/L) (GO). All were given a mixed test meal providing 40 g triglycerides. Serum and incremental chylomicron triglycerides 0-7 h areas under the curve (AUCs) as well as triglyceride levels in apoB-48-containing triglyceride-rich lipoprotein (TRLs) or chylomicrons were significantly higher in HTAOs and NTAOs than in GOs and controls postprandially. The size of chylomicron particles was bigger in controls and GOs than in HTAOs and NTAOs postprandially. Android obese subjects showed abnormally elevated fasting apoB-48 and apoB-100 triglyceride-rich lipoprotein (TRL) levels. Most abnormalities that were found correlated to plasma levels of insulin and apoC-III. In conclusion, an abnormal postprandial lipid pattern is a trait of abdominal obesity even without fasting hypertriglyceridemia.

Adipose Tissue↗
PubMed1998

Method for simultaneous measurements of traces of heptadeuterated cholesterol and cholesterol by gas chromatography-mass spectrometry: application in humans.

An assay was developed to quantify deuterated cholesterol (used as a tracer) and cholesterol using gas chromatography-mass spectrometry. Ergosterol and epicoprostanol were used as internal standards. Deuterated cholesterol was quantified by comparing its peak area to that of epicoprostanol and cholesterol to ergosterol. The mean absolute recovery in spiked serum was 99.96%; the precision was in the range 0.16-10.9% and accuracy 90.4-100%; the limit of detection in plasma was 3x10(-5) mmol l(-1). Using two internal standards, the method described herein seems particularly suitable for application in humans i.e., measuring traces of deuterated cholesterol (range: 0-6.26 x 10(-4) mmol l(-1)) along with natural cholesterol (range: 0.065-4.42 mmol l(-1)) in human plasma and lipid fractions postprandially.

Cholesterol↗
PubMed1998

The effects of cholesterol uptake from high-density lipoprotein subfractions on biliary sterol secretion in rats with essential fatty-acid deficiency.

High-density lipoprotein (HDL) participates in the transfer of cholesterol to the liver, in which it is subsequently excreted into bile as bile acid and cholesterol. In this study, the effect of essential fatty-acid (EFA) deficiency on cholesterol contribution from HDL subfractions to bile was investigated. Rats that were rendered EFA-deficient over 4 weeks displayed changes in their plasma HDL subfractions and liver tissue fatty acids. Plasma linoleic (18:2n6), linolenic (18:3n3,) and arachidonic (20:4n6) acids decreased, whereas palmitoleic (16:1n7) and eicosatrienoic (20:3n9) acids increased. EFA deficiency was confirmed by an elevation of the 20:3(n-9)/20:4(n-6) index. To examine the hepatic handling of lipoprotein-derived cholesterol, HDL2 and HDL3 from donor rats were isolated, labeled with [14C]-cholesterol, and injected iv into EFA-deficient and normal rats with a bile fistula. In HDL subfractions from control rats, no significant variations were noted in the specific activity of cholesterol output in both groups of EFA recipient rats; however, the output of biliary bile acids was significantly decreased in EFA-deficient rats following the administration of labeled HDL3. In HDL2 and HDL3 originating from EFA-deficient rats, a decrease in the specific activity of both biliary cholesterol and bile acid output was recorded in EFA-deficient rats. Concomitant with the defective HDL2- and HDL3-[14C] cholesterol translocation into bile of EFA-deficient rats, increased hepatic very-low-density lipoprotein (VLDL)-[14C] cholesterol secretion was observed in vivo. HDL2 and HDL3 particles, derived from EFA-deficient rats, had an altered composition including a depletion in apo A-I and an enrichment in apo E isoforms, which are the the two major HDL apolipoproteins involved in the delivery of cholesterol to the liver. Taken together, these results show that normal EFA status is necessary for efficient HDL-cholesterol processing by the liver.

Animals↗
PubMed1998

Postprandial studies on dietary cholesterol in human subjects using stable isotopes and gas chromatography-mass spectrometry analysis.

We hypothesized that intestinal absorption and postprandial re-secretion of dietary cholesterol may be a particularly complex process in humans. To test this hypothesis, we used deuterium-enriched cholesterol to specifically label meal cholesterol and developed an improved method for quantitative measurement of traces of deuterated cholesterol as well as cholesterol with reference to two different internal standards by gas chromatography-mass spectrometry (GC-MS) measurement. In the first study, a group of healthy subjects ingested a single test meal containing deuterated cholesterol with a 7 h postprandial follow-up. In the second one, a group of healthy subjects ingested a first test meal containing deuterated cholesterol and a follow-up was performed during three consecutive test meals and later until 72 h. The most striking observations were that the occurrence of dietary cholesterol in chylomicrons is not concomitant to triglycerides and is very low after a single meal while most dietary cholesterol is re-secreted in chylomicrons after a second, and even a third, fat test meal. The data obtained show that the re-secretion of dietary cholesterol from the small intestine is a slow and complex process in humans.

Adult↗
PubMed1998

Oxidative stress status and antioxidant status are apparently not related to carotenoid status in healthy subjects.

Several lines of evidence suggest that carotenoids may have a beneficial effect on health as a result of their antioxidant properties. In addition to beta-carotene, five other carotenoids are recovered in noticeable amounts from human plasma and tissues. Although the effect of beta-carotene on in vivo lipid peroxidation has been documented, few data are available on the effects of the other carotenoids. We evaluated the ability of the main human carotenoids to reduce lipid peroxidation by determining the correlations between plasma carotenoid concentration and plasma antioxidant capacity (in 79 healthy volunteers) and between carotenoid status and breath pentane excretion (in a subgroup of 24 subjects). Carotenoid intake was assessed by means of a 3-day food recall. Carotenoid status was evaluated by measurement of beta-carotene, lycopene, lutein/zeaxanthin, and alpha-carotene in plasma and buccal mucosal cells. Antioxidant status was evaluated by measurement of the total antioxidant capacity of the plasma. Oxidative stress status was evaluated by breath pentane measurements. Food recall data and the carotenoid concentrations in plasma and buccal mucosal cells showed that the subjects had normal carotenoid intake and normal carotenoid status. The total antioxidant capacity of the plasma was not related to the concentration of any specific carotenoid. The level of expired air pentane was not related to the carotenoid status of the subjects. These results show that normal concentrations of carotenoids in plasma and tissues are not correlated with these clinical markers of antioxidant and oxidative stress status.

Adult↗
PubMed1998

Effects of graded amounts (0-50 g) of dietary fat on postprandial lipemia and lipoproteins in normolipidemic adults.

Eight normolipidemic males ingested on separate days and in a random order five mixed meals containing 0, 15, 30, 40, or 50 g fat. Fasting and postprandial blood samples were obtained for 7 h and chylomicrons and lipoproteins were isolated. The nonfat and 15-g fat meals did not generate noticeable postprandial variations except for HDL phospholipids (P < 0.05). The serum and chylomicron triacylglycerol responses obtained after the meals correlated positively with the amount of fat ingested and peaked after 2-3 h. Serum free cholesterol and phospholipids increased and esterified cholesterol decreased postprandially in a dose-response manner. At the same time, triacylglycerol-rich-lipoprotein triacylglycerols, esterified cholesterol, LDL free cholesterol, HDL triacylglycerols, phospholipids, and free cholesterol increased whereas LDL and HDL esterified cholesterol decreased when the amount of ingested fat increased. The data showed that increasing the amount of fat in the usual range of ingestion (0-50 g) led to stepwise increases in the postprandial rise of chylomicron and serum triacylglycerols and induced marked changes in serum lipoproteins postprandially. The existence of a no-effect level of dietary fat (15 g) on postprandial lipemia and lipoproteins in healthy adults was shown.

Adult↗
PubMed1998

Comparison of the postprandial plasma vitamin A response in young and older adults.

To assess the influence of age on vitamin A intestinal and liver metabolism in humans, the postprandial plasma concentrations of intestinal-originated vitamin A, i.e., retinyl esters, and liver-originated vitamin A, i.e., retinol, were compared in eight young (20-30 years old) and eight elderly (64-72 years old) healthy men. Plasma and chylomicron retinyl esters and retinol concentrations were measured for up to 24 h following the intake of a test meal that contained 23,300 RE retinyl palmitate. The chylomicron retinyl palmitate response (area under the curve) was not significantly different between the two groups, but its peak was slightly delayed (1 h) in the elderly men. The proportion of the different retinyl esters secreted in the chylomicrons was not significantly different between the two groups. The postprandial plasma retinol concentration did not change in the young participants, whereas it significantly increased in the elderly. These results suggest that vitamin A intestinal absorption and retinol intestinal esterification processes are not markedly modified in the elderly, whereas the chylomicron clearance and the regulation of postprandial plasma retinol concentration are apparently altered in these subjects.

Adult↗
PubMed1998

Chylomicron beta-carotene and retinyl palmitate responses are dramatically diminished when men ingest beta-carotene with medium-chain rather than long-chain triglycerides.

The effect of the ingestion of beta-carotene with medium-chain triglycerides (MCT) or long-chain triglycerides (LCT) on the bioavailability and the provitamin A activity of beta-carotene was investigated in humans. Sixteen healthy young men ingested, on two different days, a test meal containing 120 mg beta-carotene incorporated into 40 g LCT (LCT meal) or 40 g MCT (MCT meal). This meal was followed 6 h later by a beta-carotene-free meal containing 40 g LCT. Chylomicron beta-carotene, retinyl palmitate and triglycerides were measured every hour for 12.5 h after the first meal. No significant increase in chylomicron triglycerides was detected for the 6 h after the MCT meal intake, whereas a significant increase in chylomicron triglycerides was observed after the LCT meal intake. The chylomicron beta-carotene and retinyl palmitate responses to the MCT meal (0-6 h area under the curves, AUC) were significantly (P < 0.05) lower [AUC = 68.1 +/- 26.8 and 43. 4 +/- 10.4 nmol/(L.h), for beta-carotene and retinyl palmitate, respectively] than those obtained after the LCT meal [301.4 +/- 64.0 and 166.0 +/- 29.0 nmol/(L.h), respectively]. The chylomicron beta-carotene and retinyl palmitate responses obtained after the beta-carotene-free meal (6-12.5 h AUC) were also significantly lower when the first meal provided MCT rather than LCT. The chylomicron (retinyl palmitate/beta-carotene) ratios were constant during the postprandial periods, whatever the meal ingested. We conclude that the chylomicron beta-carotene response is markedly diminished when beta-carotene is absorbed with MCT instead of LCT. This phenomenon is apparently due to the lack of secretion of chylomicrons in response to MCT; however, a lower intestinal absorption of beta-carotene or a higher transport of beta-carotene via the portal way in the presence of MCT cannot be ruled out. Finally, the data obtained show that MCT do not affect the rate of intestinal conversion of beta-carotene into vitamin A.

Adult↗
PubMed1998

Low and high responders to pharmacological doses of beta-carotene: proportion in the population, mechanisms involved and consequences on beta-carotene metabolism.

The aim of this study was to assess the interindividual variability of chylomicron beta-carotene response to a pharmacological load of beta-carotene in the population, to identify the mechanisms responsible for this variability, and to evaluate its consequences on beta-carotene status and metabolism. The variability, as estimated by the 3-h chylomicron beta-carotene response to 120 mg beta-carotene in 79 healthy male volunteers, was high (CV = 61%), but it was unimodal and all the subjects had detectable chylomicron beta-carotene. In 16 subjects randomly selected among the 79, the interindividual variability of the triglyceride-adjusted chylomicron (beta-carotene + retinyl palmitate) response (0-12.5 h area under the curve) was high (CV = 54%), suggesting that there is a high interindividual variability in the efficiency of intestinal absorption of beta-carotene. The chylomicron beta-carotene response was correlated (r = 0.50, P < 0.05) with the chylomicron triglyceride response. The beta-carotene status, as assessed by beta-carotene concentration in buccal mucosal cells, was correlated (r = 0.73, P < 0.05) with the triglyceride-adjusted chylomicron beta-carotene response, i.e., with the ability to respond to beta-carotene. The triglyceride-adjusted chylomicron retinyl-palmitate response was correlated (r = 0.55, P < 0.05) with the triglyceride-adjusted chylomicron beta-carotene response. Plasma all-trans retinoic acid slightly, but significantly, increased (+40%) 3 h after the beta-carotene load, but this increase was not related to the triglyceride-adjusted beta-carotene response. In conclusion, the ability to respond to beta-carotene is highly variable, but there is probably a very small proportion of true non-responders to pharmacological doses of beta-carotene in the healthy population. This variability is apparently mainly due to interindividual differences in the efficiency of intestinal absorption of beta-carotene and in chylomicron metabolism. The ability to respond to beta-carotene can affect the beta-carotene status and the provitamin A activity of beta-carotene, but it has apparently no effect on the amount of retinoic acid appearing in the plasma after the ingestion of a pharmacological dose of beta-carotene.

Administration, Oral↗
PubMed1997

Oxidative tyrosylation of high density lipoprotein impairs biliary sterol secretion in rats.

The oxidation of low density lipoprotein plays a central role in the pathogenesis of atherosclerosis. Oxidative modification could also occur in high density lipoprotein (HDL), which may alter reverse cholesterol transport. It has recently been proposed that myeloperoxidase-generated tyrosyl radical may modify HDL. In the present study we have examined whether the oxidative tyrosylation of HDL by peroxidase may alter biliary cholesterol secretion and bile acid transformation. HDL was modified by exposure to L-tyrosine, H2O2 and peroxidase labelled with [14C]cholesterol and injected i.v. into rats with bile diversion. A reduced excretion of radioactivity (14-20%) was recovered in the bile of animals administered with tyrosylated HDL at the different periods of collection. Both labelled cholesterol (14.3%, P < 0.05) and bile acids (18.9%, P < 0.05) were decreased in these rats, similarly to results obtained from malondialdehyde-modified HDL. Consequently, this kind of oxidative modification resulted in a loss of the hepatobiliary systems capacity to normally process HDL.

Animals↗
PubMed1997

Dietary fatty acids and arteriosclerosis.

Dietary fatty acids show different molecular structures and thus physicochemical properties of importance regarding lipid metabolism and atherogenesis. Intake of dietary fatty acids is associated with several risk factors for arteriosclerosis including fasting and postprandial plasma lipids and lipoproteins, obesity and thrombosis. Consumption of saturated fatty acids is detrimental while that of monounsaturated and polyunsaturated fatty acids lowers the incidence of coronary heart disease, but the respective influence of the various unsaturated fatty acids ingested is still discussed. The importance of the interaction between the human gene pool and dietary fatty acids is emerging.

Arteriosclerosis↗
PubMed1997

Digestive and metabolic effects of potato and maize fibres in human subjects.

The physiological effects of dietary fibres in humans are due to their physico-chemical properties. However, it is difficult to predict these effects simply by measuring certain characteristics in vitro. Studies in human subjects are still required to assess the effectiveness of new substrates. The aim of the present study in healthy human subjects was to evaluate the effects of two novel fibres, potato (PF) and maize (MF), on fasting and postprandial blood concentrations of carbohydrate and lipid metabolites as well as on stool output and transit time. The chemical composition, water-binding capacity (WBC) and fermentative properties of the fibres were also characterized in order to determine their possible involvement in digestive and metabolic effects. Stools, as well as breath and blood samples, were collected after consumption for 1 month of either a basal diet (control) or a basal diet supplemented with fibre (15 g/d). MF resisted fermentation better than PF and had lower digestibility. However, both fibres increased faecal output of dry matter, neutral sugars and water. There was an inverse relationship between stool weight and orofaecal transit time, although only MF significantly reduced transit time. Orocaecal transit was lengthened by PF, probably because of its high WBC. PF ingestion also decreased postprandial plasma levels of total and esterified cholesterol but had no effect on fasting concentrations. In contrast, MF lowered fasting cholesterolaemia and increased free:esterified cholesterol. These particular physiological and fermentative properties suggest that PF and MF would be suitable ingredients in a healthy diet.

Adult↗
PubMed1997

A new look at dietary carbohydrate: chemistry, physiology and health. Paris Carbohydrate Group.

The current view of dietary carbohydrates as simply providing us with energy is outdated. Because of their varied chemistry and physical form the rate and extent to which the different types are digested in and absorbed from the small intestine varies. This in turn leads to affects on satiety, blood glucose and insulin, protein glycosylation, lipids and bile acids. Some carbohydrates reach the colon where they are fermented and affect many aspects of large bowel function, colonocyte and hepatic metabolism. A new framework for classifying and measuring food carbohydrates is needed to allow a greater understanding of the role of individual species in health and to inform the public of their importance. A classification based primarily on molecular size (degree of polymerisation) into sugars, oligosaccharides and polysaccharides, is suggested, with sub-groups identified by the nature of the monosaccharides. Greater knowledge of the chemical and physical properties of carbohydrates allow a more precise relation with physiology and health to be drawn. The Carbohydrate Group met in Paris in December 1995 at the invitation of Gerard Pascal, Director of CNERNA. Financial support for the meeting was provided by CNERNA.

Carbohydrates↗
PubMed1997

Dietary triglycerides, up to 40 g/meal, do not affect preformed vitamin A bioavailability in humans.

OBJECTIVE: Assessing the effect of the dose of dietary triglycerides on preformed vitamin A (retinyl esters) bioavailability in humans. DESIGN: Four test meals containing 15,000 RE retinyl-palmitate and either 0, 15, 30 or 40 g added triglycerides were ingested by eight healthy volunteers, at different days and in a randomized order. SETTING: The study was done in the Hospital Sainte Marguerite, Marseille, France. SUBJECTS: Eight healthy male volunteers were recruited by advertisement. INTERVENTION: Blood samples were collected every hour for seven hours after the test meals intake. Serum and chylomicron (Svedberg flotation unit > 1000) were prepared by centrifugation and retinyl esters were measured by HPLC. RESULTS: The serum retinyl ester response was not significantly lower after the intake of the meal without added triglycerides (7944 +/- 3262 nmol/L h) than after the intake of the fat meals (10012 +/- 2182, 7869 +/- 3157 and 10777 +/- 2067 nmol/L h for the 15, 30 and 40 g-fat meal, respectively), indicating that the serum retinyl ester response was not related to the amount of meal triglycerides. Chylomicron retinyl linoleate response stepwise increased when the amount of meal triglycerides increased while retinyl palmitate and retinyl stearate responses reached a maximum since 15 g triglycerides. Postprandial serum retinol concentration did not change whatever the meal ingested. CONCLUSIONS: (i) a significant amount of preformed vitamin A is apparently absorbed when ingested with trace amount of meal triglycerides only; (ii) meal triglycerides, up to 40 g/meal, do not increase preformed vitamin A bioavailability; (iii) the retinyl ester pattern recovered in the chylomicrons, and probably the esterification process of retinol, is affected by the amount of meal triglycerides; (iv) postprandial retinol homeostasis is not affected by dietary triglycerides.

Adult↗
PubMed1997

Postprandial chylomicron and plasma vitamin E responses in healthy older subjects compared with younger ones.

The effect of ageing on vitamin E bioavailability in humans was assessed by comparing chylomicron and plasma alpha-tocopherol postprandial concentrations after a dose of vitamin E (432 or 937 IU as d1-alpha-tocopherol acetate), in eight young (20-30 years old) and eight healthy elderly men (64-72 years old). The fasting plasma alpha-tocopherol concentration was significantly higher in the elderly (33 +/- 2 mumol L-1) than in the young (22 +/- 2 mumol L-1). In both groups, the plasma and chylomicron alpha-tocopherol postprandial concentrations were significantly, approximately twofold, higher after the 937-IU meal than after the 432-IU meal. For both test meals, the chylomicron alpha-tocopherol areas under the curve were significantly lower in the elderly than in the young subjects: 98.9 +/- 16.5 (young group) vs. 55.3 +/- 7.8 (elderly group) mumol L-1 h for the 937-IU test meal and 60.4 +/- 14.1 (young group) vs. 26.0 +/- 7.6 (elderly group) mumol L-1 h for the 432-IU test meal, whereas the plasma alpha-tocopherol area under the curve was significantly higher in elderly than in young subjects: 337.56 +/- 16.11 (937-IU test meal) vs. 159.81 +/- 35.55 (432-IU test meal) mumol L-1 h in the young group and 709.55 +/- 69.33 (937-IU test meal) vs. 436.39 +/- 41.08 (432-IU test meal) mumol L-1 h in the elderly group. We concluded that (a) the amount of vitamin E appearing in plasma is proportional to the dose ingested (up to 937 IU); (b) the intestinal absorption of vitamin E is not increased, even possibly decreased, in the elderly; and (c) the amount of vitamin E transported by non-chylomicron lipoproteins is apparently higher in the elderly. This suggests that vitamin E postprandial transport is affected by ageing, mainly as the consequence of age-related modifications of lipoprotein metabolism.

Adult↗