Biomedical subjects

D Lairon

Publications and source records attributed to D Lairon.

At least 73 records · Page 4Linked to original sources

PubMed1992

Effects of oat bran, rice bran, wheat fiber, and wheat germ on postprandial lipemia in healthy adults.

Six normolipidemic males ingested on separate days a low-fiber test meal [2.8 g dietary fiber (TDF)] containing 70 g fat and 756 mg cholesterol, enriched or not with 10 g TDF as oat bran, rice bran, or wheat fiber or 4.2 g TDF as wheat germ. Fasting and postmeal blood samples were obtained for 7 h and chylomicrons were isolated. Adding fibers to the test meal induced no change in serum glucose or insulin responses. The serum triglyceride response was lower (P less than or equal to 0.05) in the presence of oat bran, wheat fiber, or wheat germ and chylomicron triglycerides were reduced with wheat fiber. All fiber sources reduced chylomicron cholesterol. Cholesterolemia decreased postprandially for 6 h and was further lowered in the presence of oat bran. Serum apolipoprotein (apo) A-1 and apo B concentrations were not affected. Thus, dietary fibers from cereals may reduce postprandial lipemia in humans to a variable extent.

Adult↗

PubMed1992

Long-term wheat germ intake beneficially affects plasma lipids and lipoproteins in hypercholesterolemic human subjects.

In previous short-term studies in rats and humans, the ingestion of raw wheat germ lowered plasma triglycerides and cholesterol. Thus, the present study was designed to investigate the possible long-term effects of wheat germ intake. Diet supplementation with raw wheat germ or partially defatted wheat germ was tested in two separate groups of 10 and 9 free-living human subjects, respectively. They all exhibited hypercholesterolemia (6.14-9.67 mmol/L cholesterol) and 11 had hypertriglyceridemia. None was diabetic. Fasting blood samples were taken at the beginning of the study, after 4 wk of 20 g/d wheat germ intake, after 14 additional weeks of 30 g/d wheat germ intake and after 12 wk without any supplementation. Dietary records were kept for seven and three consecutive days, before and during the wheat germ intake periods, respectively. Raw wheat germ intake significantly decreased plasma cholesterol (-8.7%) and tended to reduce VLDL cholesterol (-19.6%) after 4 wk. After 14 additional weeks, plasma cholesterol (-7.2%) and LDL cholesterol (-15.4%) remained lower and plasma triglycerides (-11.3%) tended to be lower. The apo B:apo A1 ratio significantly decreased after both periods. Partially defatted wheat germ transiently decreased plasma triglycerides and cholesterol after a 4-wk intake. The present data indicate that wheat germ reduces cholesterolemia in the long term and could play a beneficial role in the dietary management of type IIa and IIb hyperlipidemia.

Adult↗

PubMed1991

Plasma lipid lowering effects of wheat germ in hypercholesterolemic subjects.

The present study was performed to investigate the possible effects of wheat germ supplementation on lipid metabolism in humans. Ten free-living adult subjects participated in the study. None was obese or diabetic. They all presented an hypercholesterolemia (from 6.58 to 9.50 mM), associated in 6 over 10 cases to an hypertriglyceridemia (from 1.70 to 5.00 mM). The subjects were studied in three consecutive periods, during which they first were on their usual diet (first week), they then ingested a daily supplement of 30 g wheat germ (4 weeks) and then they returned to their usual basal diet (4 weeks follow-up). Dietary records were obtained for 7 and 3 consecutive days before and during wheat germ supplementation, respectively. Fasting blood samples were taken at the end of each period. After 4 weeks of wheat germ intake, glycemia did not change while total plasma cholesterol significantly decreased (paired Student's t test, p less than or equal to 0.05) from 7.80 to 7.15 mM. LDL and HDL cholesterol values did not show marked changes, but VLDL cholesterol significantly dropped by 40.6%. Thus, the plasma/HDL total cholesterol ratio was significantly lower. Apoprotein B and A1 decreased. In the hypertriglyceridemic subjects, this was accompanied by a significant reduction of plasma triglycerides (1.64 vs. 2.68 mM) and a marked drop of VLDL triglycerides (-51%). Taken as a whole, the present results obtained in humans are very close to those previously obtained in the rat and point out that wheat germ may play a beneficial role in the dietary management of hyperlipidemia.

Adult↗

PubMed1991

Gastric lipase: evidence of an adaptive response to dietary fat in the rabbit.

In the rabbit, the stomach is the only source of preduodenal lipase, and in humans, it is quantitatively the most important. Thus, the adaptive response of gastric and pancreatic lipases to dietary fat was studied in the adult rabbit. Effect of duration was studied by feeding rabbits 12% dietary fat for 1, 2, or 4 weeks or 2.7% for 2 weeks (control). To study the effects of the amount of fat, rabbits were fed the control diet (2.7% fat) or 6% and 12% dietary fat for 2 weeks. The influence of sunflower oil and butter was compared by feeding rabbits 12% dietary fat for 2 weeks. Approximately doubling (6% vs. 2.7%) the usual amount of dietary fat was sufficient to induce a maximum increase in gastric lipase activity in the fundus [+ 66.3% (units per gram tissue) or + 85.2% (units per milligram protein)] and the total stomach mucosa [+ 84.5% (units per mucosa)], whereas pancreatic lipase activity only significantly increased when rabbits were fed 12% dietary fat. A full adaptive response was observed for both gastric and pancreatic lipases after 2 weeks of diet. Triglyceride composition did not noticeably change the adaptive response of both lipolytic enzymes. The present results agree closely with those concerning lingual lipase in the rat and evidence that gastric lipase shows an adaptive response to moderate fat intake. The implications of these findings concerning humans are discussed.

Adaptation, Physiological↗

PubMed1990

Effect of wheat bran and wheat germ on the intestinal uptake of oleic acid, monoolein, and cholesterol in the rat.

The effects of fiber-rich wheat bran and wheat germ on the intestinal absorption of dietary cholesterol, free fatty acids, and monoglycerides were studied. Rats were given a test meal containing [(14)C]oleic acid, [(14)C]monoolein, and [(3)H]cholesterol. After a 1-hour digestion period, wheat bran or wheat germ (10% of meal solids) did not significantly modify the gastric emptying of lipids. No effect of wheat bran was evidenced on the amounts of lipids and cholesterol in the intestinal content or the mucosal segments, whereas wheat germ significantly increased the cholesterol in the small intestine content, decreasing its intestinal absorption. Both fractions only slightly influenced the levels of absorbed lipids and cholesterol in the plasma and liver. In vitro binding measurements showed that the wheat fractions bind only 7% to 15% of both lipids and cholesterol. Results indicate that wheat bran has no direct effect on the mucosal uptake process, whereas wheat germ might decrease the uptake of dietary cholesterol by an as yet unknown mechanism.

Journal Article↗

PubMed1990

Adaptation of lingual lipase to dietary fat in rats.

To study the adaptive response of lingual lipase and pancreatic lipase to dietary fat, three sets of experiments were performed in adult male rats. In the first experiment, rats were fed for 3 wk a low fat diet (4.5% fat) or a 10, 20 or 30% fat diet. In the second, rats were fed a 4.5% fat diet for 4 wk or a 20% fat diet for 1, 2 or 4 wk. In the third, rats were fed for 3 wk a 10% fat diet with various sources of fat (lard, sunflower oil, olive oil, peanut oil, butter, soybean oil, corn oil or salmon oil). The results demonstrated that 10% dietary fat was sufficient to promote a maximum significant increase in lingual lipase activity (expressed in units/g tissue and in units/mg protein), whereas pancreatic lipase responded steadily to 20 and 30% fat diets. After 1 wk of feeding 20% dietary fat, both enzyme specific activities had reached their maximum values. The fatty acid composition of dietary triglyceride molecules (chain length, number and location of double bonds) had no specific effect on the adaptation of lingual lipase. The physiological implications of these findings are discussed in regard to the role of intragastric lipolysis in fat digestion.

Animals↗

PubMed1989

Isolation and properties of lipolysis inhibitory proteins from wheat germ and wheat bran.

Proteins inhibiting pancreatic lipase in vitro have been isolated from wheat germ and wheat bran, with relative molecular mass ranging from 24,400 to 27,500. Inhibition of pancreatic lipase by the wheat germ proteins is related to their ability to interact with the emulsified substrate and to hinder the adsorption of the enzyme on the interface. The extent of inhibition depends on the amount of substrate and is independent of the enzyme concentration. Bile salts forming micelles in the concentration range used are able to partially reverse the inhibition of pancreatic lipase by the wheat germ proteins. The nutritional significance of the data obtained is discussed.

Dietary Fiber↗

PubMed1989

Wheat bran and wheat germ: effect on digestion and intestinal absorption of dietary lipids in the rat.

We investigated the effects of fiber-rich wheat bran and wheat germ on dietary fat and cholesterol assimilation. Rats were given a test meal containing [14C]triolein and [3H]cholesterol. After various digestion periods, addition of the wheat fractions (10% of meal solids) did not modify the lipid gastric emptying rate. Gastric and intestinal triglyceride lipolysis was significantly reduced when wheat fractions were present. The mucosal uptakes of [14C]lipids and [3H]cholesterol were significantly modified by the wheat fractions after 1 and 2.5 h. No shift in the site of intestinal absorption and no change in the distribution of labeled lipid in the intestinal mucosa was observed. Plasma [14C]lipids and [3H]cholesterol were significantly decreased by both wheat fractions whereas these increased cecal accumulation of dietary lipids and cholesterol. Thus wheat bran and wheat germ alter fat and cholesterol processing in rats. A mechanism of action accounting for the data observed in proposed.

Animals↗

PubMed1989

Lack of effect of purified cellulose and hemicellulose on the digestion and the intestinal absorption of dietary lipids in the rat.

Fasted adult rats were intragastrically intubated an emulsified test meal containing both 14C-triolein and 3H-cholesterol, in the presence or absence of either purified hemicellulose (xylan) or cellulose (both 10% of meal solids). After a 1-hour digestion period, purified fibers did not significantly modify the rate of gastric emptying of lipids or the extent of triglyceride lipolysis in the stomach and the small intestine. The presence of cellulose or hemicellulose induced no change in the amounts of lipids and cholesterol found in the intestinal content, the mucosa, and the plasma, nor in the site of lipid mucosal uptake. As a whole, the present results show that cellulose or hemicellulose, which are the main fractions of dietary fiber in cereals, did not exert a determinant influence on the biochemical events involved in the digestion of dietary fats.

Animals↗

PubMed1988

Metabolism of low- and high-density-lipoprotein-free cholesterol in rats fed high-fat diets.

The regulating process of cholesterol in the liver was studied in relation to its exogenous contribution in the rats fed high-fat (28%) high-cholesterol (1.2%) diets rich in saturated (S) fat (lard) or polyunsaturated (PU) fat (corn oil). Accordingly, the fate of 14C free cholesterol originating from high- or low-density lipoproteins (LDL) was examined in the biliary, hepatic and plasmatic lipids, as well as the activity of two key enzymes in the metabolism of lipoproteins: lipoprotein lipase (LPL) and lecithin cholesterol acyl transferase (LCAT). The LPL activity increased in the S diet, in comparison to the PU diet or to a low fat (6%) control (C) diet and the LCAT activity increased but not significantly in the PU diet. In bile the secretion of 14C-cholesterol and 14C-bile salts originating from 14C-cholesterol-HDL increased in the S diet compared to the PU diet and a C diet [previous results]. S and PU diets increased to the same extent the hepatic storage of 14C-esterified cholesterol originating from LDL, compared to the C diet. This cholesterol would contribute to a greater extent to the hepatic synthesis of the lipoproteins destined for the plasma in the case of the S diet than that of PU diet. These results may be explained by the adaptation of hepatic acyl cholesterol acyl transferase and cholesterolesterase to both high-fat-diet enzymes acting simultaneously on the two free and esterified cholesterol compartments. It resulted in an important redistribution of the cholesterol of these two compartments between plasma, bile and liver.

Animals↗

PubMed1987

Yield and content in nitrates, minerals and ascorbic acid of leeks and turnips grown under mineral or organic nitrogen fertilizations.

The influence of mineral NPK fertilizers and organic fertilizers such as manure compost, woodchip compost and blood meal on the yields and the nutritive value of leeks and turnips were compared. Fertilizers were applied on the two crops grown successively in 200-1 containers. Mineral fertilizers, manure compost and blood meal provided equivalent vegetable yields. Contents in dry matter, ascorbic acid and minerals of leeks and turnips were not strongly affected by the different fertilization regimes. The nitrate content of both crops was significantly lower under the application of manure compost and woodchip compost, while mineral fertilizers and blood meal induced similar, higher nitrate levels. The present work thus provides new data showing the usefulness of composts in growing vegetables with low nitrate contents.

Agriculture↗

PubMed1987

Effect of pectin, wheat bran and cellulose on serum lipids and lipoproteins in rats fed on a low- or high-fat diet.

1. Four groups of adult male Sprague-Dawley rats were fed for 6 weeks on a diet with a low-fat content (50 g/kg) and another four groups were given a diet rich in fat (250 g/kg) and cholesterol (12 g/kg). In both cases, the basal diets were either fibre-depleted or supplemented with cellulose (60 g/kg), wheat bran (100 g/kg) or low-methoxyl pectin (100 g/kg). 2. Low-methoxyl pectin displayed the most hypocholesterolaemic effect and decreased the cholesterol content of the very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL), when the low-fat diet was given. When rats were fed on the high-fat diet, pectin no longer had a hypocholesterolaemic effect but still decreased the VLDL-cholesterol content. Pectin lowered serum triglyceride and VLDL-triglyceride levels only when the low-fat diet was given. 3. Wheat bran exerted no hypocholesterolaemic effect in rats fed on the low- and high-fat diets, but decreased the cholesterol content of VLDL and lowered serum triglycerides and VLDL-triglycerides when the high-fat diet was given. 4. Purified cellulose had no significant effect on plasma lipids. 5. As shown by multivariance analysis, low-methoxyl pectin and wheat bran both beneficially modified the serum triglyceride and cholesterol variables except VLDL-triglycerides. However, the magnitude of the effect of each individual type of fibre was dependent on the fat and cholesterol content of the diet, suggesting the existence of different mechanisms of action.

Animals↗

PubMed1987

Beneficial effect of wheat germ on circulating lipoproteins and tissue lipids in rats fed a high fat, cholesterol-containing diet.

Adult male rats were fed for 7 wk either a low fat diet (3% fat) or a high fat-cholesterol diet (20% fat, 0.5% cholesterol) containing 7% wheat germ or not. Body weights and food intakes were unchanged by adding wheat germ to the control low fat or high fat diets. Adding wheat germ to the high fat-cholesterol diet significantly increased high density lipoprotein (HDL) cholesterol and the HDL-serum cholesterol ratio and lowered the very low density lipoprotein (VLDL) triglycerides. Thus the lipoprotein pattern was comparable to that obtained with the low fat diet, but the VLDL lipid composition remained altered. At the same time, triglyceride and cholesterol accumulation in the liver and the triglyceride content in skin were significantly decreased. When wheat germ was added to the low fat diet, cholesterol and triglycerides were not significantly modified. No adaptative change in lipase and colipase contents was observed in the pancreas of rats fed the wheat germ-supplemented diets, whereas the high fat diet increased these values. The results show a beneficial effect of wheat germ added to a high fat-cholesterol diet on the lipid status of rats; the implicated mechanisms are yet to be elucidated.

Animals↗

PubMed1987

Combined effects of chlorpromazine and high fat diet on lipid levels and enzyme activities in bile, liver and plasma of Wistar rats.

The effects of high fat diet and injection of chlorpromazine on bile lipid secretion were studied in the rats fed a control diet (C), a saturated fat, high cholesterol diet (S) and a polyunsaturated fat, high cholesterol diet (PU). As compared to controls, injection of chlorpromazine in the S and PU diet groups caused no appreciable change in the level of bile salts and bile phospholipids. Chlorpromazine did however enhance bile cholesterol, especially in the PU group, and lower secretion of lysosomal enzyme (beta-glucuronidase) into bile. Impairment of lysosomal enzyme secretion but not of bile lipid secretion suggests that the lysosomal activity is not directly involved in the bile secretion mechanism. These data point up the risks of using chlorpromazine therapy in association with a diet high in fat and cholesterol.

Animals↗

PubMed1986

A quantitative dynamic concept of the interphase partition of lipids: application to bile salt-lecithin-cholesterol mixed micelles.

A system is proposed for a quantitative classification of lipids, based on interphase partition coefficients. This system enables calculation of exchanges of lipid molecules between phases. The mass/volume chemical unit mol X cm-3, strictly derived from the CGS system, is used, thus simplifying mathematical relations. Applied to bile salt-lecithin-cholesterol mixed micelles, this dynamic concept gives new insight into the variations of physico-chemical parameters. Experimental results obtained with the glycodesoxycholate and the taurocholate show a striking difference in partition coefficients between aqueous and mixed bile salt-lecithin interfacial phases. A new model applying triangular co-ordinates to a bile salt-lecithin-cholesterol mixed lipid phase is described.

Bile Acids and Salts↗

PubMed1985

Hydrolysis of intralipid by pancreatic lipase and phospholipase A2-gel filtration studies.

Intralipid was incubated with pancreatic lipase (EC 3.1.1.3) and/or phospholipase A2 (EC 3.1.1.4) at two bile salts/phosphatidylcholine molar ratios and at two different triglyceride hydrolysis rates using various amounts of lipase. Incubations were studied by gel filtration. Results show: During lipase action, three phases of lipids coexist: an emulsified phase, a micellar phase and an intermediate heavy phase sized between the two others. The equilibrium between each phase is dependent upon the bile salts concentration. Under these conditions, pancreatic lipase was at 60% bound to the emulsified phase, whereas pancreatic phospholipase A2 was bound at 94% to the micellar phase.

Animals↗

PubMed1985

Effects of dietary fibers and cholestyramine on the activity of pancreatic lipase in vitro.

Most experiments were conducted in the presence of human gallbladder bile; colipase and pancreatic lipase were purified using porcine pancreas. The adsorption of bile salts, phospholipids and cholesterol from the bile, together with that of pancreatic lipase was measured on wheat bran, cellulose, hemicellulose (xylan), slightly methylated pectin (42%) and cholestyramine. In contrast to cholestyramine which intensively binds biliary lipids (61.7-81.7%) and pancreatic lipase (47.5%), the fibers studied only had a low adsorbent power. The direct influence of these fibers and of cholestyramine at concentrations ranging from 0-5% on lipase activity was measured at constant pH, using two conventional assay systems, long chain triglycerides and tributyrin. In the presence of human bile and colipase, a drastic reduction in triglyceride hydrolysis by lipase was observed with cholestyramine (loss of 66-82%) and wheat bran (loss of 77-94%) at 1% concentration. The other fibers did not have any marked effects on enzyme activity. The use of a radio labeled lipase made it possible to demonstrate that the inhibitory effect of bran on enzyme activity was independent of adsorption phenomena on bran. The fraction of bran that can be solubilized in the aqueous phase, in fact, induced this reduction in activity. The presence of protein inhibitor in bran may be responsible for the reduction in pancreatic lipase activity.

Animals↗

PubMed1985

Effect of wheat bran, pectin and cellulose on the secretion of bile lipids in rats.

We assayed the lipid content of bile from rats that had been fed either a standard diet (5% fat) or a high fat diet (25% fat, 1.2% cholesterol) in the presence or in the absence of various dietary fibers (namely, wheat bran, pectin and cellulose). The cholesterol concentration in bile from rats fed the high fat diet plus wheat bran or pectin was lower than that of the rats fed the high fat, high cholesterol diet without fiber. Bile phospholipids did not vary significantly from one group to another. In comparison to the standard diet, the high fat, high cholesterol diet led to a greater ratio of primary to secondary bile salts and a higher level of glycoconjugates. The observed differences may be explained by a variation in the metabolism of bile salts brought about by the difference in diet.

Animals↗