Faecal short chain fatty acids in healthy subjects participating in a randomised controlled trial examining a soluble highly viscous polysaccharide versus control.

BACKGROUND: Short chain fatty acids (SCFA) are produced by the bacterial fermentation of dietary fibre and have been linked with intestinal health. The present study examined faecal SCFA concentrations in subjects consuming a novel soluble highly viscous polysaccharide (HVP) or control for 3 weeks. A total of 54 healthy adults participated in a randomised, double-blind, placebo-controlled study. METHODS: Subjects were randomised to consume HVP or control (skim milk powder). A dose of 5 g day(-1) was consumed in the first week, followed by 10 g day(-1) in the second and third weeks (n = 27 per group). The primary outcome was SCFA concentrations in faecal samples collected at baseline (visit 1, V1), at 1 week (V2) and at 3 week (V3). RESULTS: The reduction in faecal acetate from V1 to V3 in control subjects was not observed in subjects consuming HVP. There were no differences in propionate, butyrate, valerate or caproate concentrations. There was a significant treatment effect (P = 0.03) for total SCFA, with higher concentrations observed in subjects consuming HVP versus control. CONCLUSIONS: HVP is a viscous functional fibre that may influence gut microbial fermentation. Further work is warranted to examine the fermentative properties of HVP and possible links with appetite regulation and reduced serum low-density lipoprotein cholesterol concentrations.

Effects of a 3-month supplementation with a novel soluble highly viscous polysaccharide on anthropometry and blood lipids in nondieting overweight or obese adults.

BACKGROUND: High viscosity fibre is known to exert many beneficial effects on appetite and metabolism. It could potentially help in weight management, in dieting or nondieting individuals. The present study investigated the effects of the daily intake of a novel high viscosity polysaccharide (HVP) over 3 months in nondieting obese or overweight men and women. METHODS: The study comprised a double-blind, randomised controlled clinical trial. Participants ingested 5-15 g per day of either HVP (n = 29, experimental group) or inulin (n = 30, control group) for 15 weeks. Changes in anthropometry (weight, waist and hip circumferences), blood lipids and glucose tolerance were studied from the beginning to the end of administration. Compliance and tolerance were examined. RESULTS: Differences appeared between HVP and inulin supplementation in female participants only. Mean (SD) decreases in body weight [1.6 (3.2) kg; approximately 2% of initial weight] and hip circumference [2.8 (3.6 ) cm] occurred in women of the HVP group but not in controls (Time × Group interactions, P ≤ 0.002). Total, high-density lipoprotein and low-density lipoprotein-cholesterol were lower at the end of supplementation in the women of the HVP group compared to controls (P ≤ 0.021). No effect appeared in waist circumference and triacylglycerol. No difference was noted in the number or severity of the adverse effects reported in both groups. Adverse effects were mild and agreed with commonly reported reactions to intake of dietary fibre. CONCLUSIONS: Beneficial although modest effects appeared after several weeks of daily HVP intake in nondieting obese or overweight women. The effects of HVP should be investigated in the context of a weight loss programme.

Isolation and characterization of brush-border membrane from trout intestine. Regional differences.

The isolation of brush-border membranes from trout enterocytes is described for both middle and posterior intestine. Both procedures are based on differential centrifugations combined with calcium precipitation. Classical marker enzymes are quantified and indicate a valuable purification of the membranes (13-18-fold). No difference appears when comparing the relative amounts of phospholipids, cholesterol and proteins in microvillus membranes isolated from either middle or posterior intestine. In contrast, the membranes isolated from middle intestine are more unsaturated than those from the posterior one, and their sphingomyelin/phosphatidylcholine ratio is lower. These differences are reflected by fluorescence anisotropy studies with diphenylhexatriene as lipid fluorophore which indicate a higher fluidity of the microvillus membranes from the middle intestine as compared with those from the posterior intestine. These results point out the importance of the fatty acyl chains and that of the relative amounts of phosphatidylcholine and sphingomyelin in controlling the fluidity of biological membranes in relation with their transport properties.

Topological distribution of choline phospholipid fatty acids in trout intestinal brush-border membrane.

The transbilayer distribution of choline phospholipids in trout intestinal brush-border membrane has been investigated using phospholipase C (from Clostridium welchii). In the middle intestine, 84% of phosphatidylcholine (PC) and 60% of sphingomyelin (SP) are located in the outer membrane leaflet. In the posterior intestine, 89% of PC and 52% of SP are located in the outer membrane leaflet. The externally located PC molecular species are (n - 3) fatty acid-rich in both parts of the intestine. While the sphingomyelin molecular species containing 24:1(n - 9) are exclusively located in the outer leaflet in the middle intestine, those containing 14:0 are more abundant in the same leaflet but in the posterior intestine. This strongly asymmetric distribution of both choline phospholipids may have numerous consequences on the brush-border membrane characteristics.

Topological distribution of aminophospholipid fatty acids in trout intestinal brush-border membrane.

The transbilayer distribution of aminophospholipids in trout intestinal brush-border membrane has been investigated using trinitrobenzene sulfonic acid (TNBS). In the middle intestine, phosphatidylethanolamine (PE) is symmetrically distributed between the two leaflets while 68% of the phosphatidylserine (PS) are located in the inner membrane leaflet. In the posterior intestine, 64% of the PE and 69% of the PS are located in the inner membrane leaflet. When asymmetrically distributed, the inner species of PE and PS have a higher content of 22:6(n-3) than the outer ones. This asymmetric distribution of docosahexaenoic acid in trout intestinal brush-border membrane might be related to the rod-like shape of the microvillus membrane and to its metabolism to hydroxylated derivatives.

Phytosterols have an unfavourable effect on bacterial activity and no evident protective effect on colon carcinogenesis.

The effects of physiological dietary phytosterol supplements on intestinal microflora activity and faecal sterols and their capacity to protect rats fed a normal or high saturated fatty-acid diet against tumour development were studied. A group of 80 female Wistar rats were fed an 8% lipid diet for 4 weeks (adaptation period) and then randomly assigned in a factorial experimental design study to diets containing 8% or 24% hydrogenated coconut oil, with or without a 24-mg/day/rat phytosterol supplement. They were instilled intrarectally with saline or methyl-nitroso-urea (MNU). Faecal sterol output was analysed for one week each month. Pathological analysis was done at the end of the 30-week experiment. Animals treated with MNU and given phytosterol supplements had tumour frequencies (8/20) similar to those not fed phytosterols (11/20). The fat-supplemented diet had no significant influence. Colonic glands were found in area of lymphoid follicles in all the groups, but were more frequent in rats on high-fat diets (P < 0.01). The coprostanol and the cholesterol excretion of the phytosterol-supplemented rats was significantly enhanced. Therefore phytosterols have an unfavourable effect on bacterial activity. These data confirm the capacity of phytosterols to decrease cholesterol absorption, but indicate that a large excess of phytosterol must be avoided until further research on its effects on carcinogenesis has been done.

Hydrogen excretion upon ingestion of dairy products in lactose-intolerant male subjects: importance of the live flora.

OBJECTIVE: To assess the effects of the ingestion of milk, yoghurt (10(8) bacteria/ml), heat-treated yoghurt (<15 bacteria/ml) and two products obtained by dilution of yoghurt with heat-treated product (10(6) and 10(5) bacteria/ml) on hydrogen production and symptoms of lactose intolerance in lactose malabsorbers. DESIGN: Double-blind, randomised cross-over design. SETTING: The study was performed in the phase 1 clinical unit of OPTIMED, Nancy, France. SUBJECTS: Twenty-four male lactose malabsorbers were selected for the study. INTERVENTIONS: Hydrogen production and adverse events were followed during 8 h after ingestion of the products. RESULTS: The results clearly demonstrate that ingestion of yoghurt with 10(8) bacteria/ml leads to lower H(2) excretion and complaints than the other products. Results observed with the products containing a reduced population of live flora remain better than those observed with milk. CONCLUSIONS: The importance of a high population of the live flora is underlined.

Effects of eicosatetraynoic acid on membrane lipids of trout liver and intestine.

After two months feeding either an (n-3) or an (n-6) fatty acid-rich diet, two groups of trout were switched to the (n-6) or the (n-3) fatty acid-rich diet, respectively. Half of each group was treated with 0.03% 5,8,11,14-eicosatetraynoic acid (ETYA) in the diet. Liver and intestinal brush border membrane lipids were analyzed. No effect was observed on their cholesterol content. ETYA induced an accumulation of 18:2(n-6), and it did not affect the 20:4(n-6) content but decreased the 22:5(n-6) content. ETYA induced an increase of 18:3(n-3) content in the brush border membrane and a decrease of the 22:6(n-3) content in the liver. Those results suggest that ETYA blocks mainly the delta 6-desaturase, which should have two different sites in the liver and one in the intestine.

Increased plasma PYY levels following supplementation with the functional fiber PolyGlycopleX in healthy adults.

BACKGROUND/OBJECTIVES: A variety of dietary fibers have been shown to alter satiety hormone gene expression and secretion. The objective of this study was to examine plasma satiety hormone concentrations in healthy subjects consuming either PolyGlycopleX (PGX) or control (skim milk powder) for 21 days. SUBJECTS/METHODS: A randomized, double-blind, placebo-controlled clinical study was conducted in 54 healthy male and female adults. Participants consumed 5 g per day of PGX or control for 1 week followed by 2 additional weeks of 10 g per day of assigned product (n=27 per group). Primary outcomes measured at three visits (V1, V2 and V3) were plasma active glucagon-like peptide-1 (GLP-1) total ghrelin, peptide YY (PYY) and insulin. RESULTS: There was a significant effect of visit for fasting PYY with control participants experiencing decreased PYY levels over time while PGX prevented this decline. When stratified by body mass index (BMI), PGX increased fasting PYY levels from week 1 to week 3 compared with control in participants with BMI <23 kg/m(2). There was a significant effect of visit for fasting ghrelin with levels decreasing in both PGX and control groups over time. No differences were detected in fasting GLP-1 levels. Although there was a 14% reduction in fasting insulin between V1 and V3 with PGX this was not significantly different from control. CONCLUSIONS: PGX is a highly viscous, functional fiber that modifies satiety hormone secretion in healthy adults. Its' potential to act similarly in overweight adults warrants investigation.

Physiological importance of omega-3/omega-6 polyunsaturated fatty acids in man. An overview of still unresolved and controversial questions.

The 'essentiality' of (omega-6) and (omega-3) fatty acids in mammals is well known. Nevertheless, some important points remain unclear concerning their implication in physiology. After a short discussion about the definition of essential fatty acids deficiency, this brief overview deals with some of these points, pointing out some of the unresolved questions. Different subjects are approached concerning the (omega-6) and (omega-3) fatty acids metabolism: desaturases, eicosanoids, production, as well as some of their metabolic effects on cell membranes, intestinal function, glucose and lipid metabolism, haemorheology.

Dietary modifications of phospholipid composition and biophysical properties of the brush border membrane along the trout intestine.

Brush border membranes (BBM) are isolated from middle and posterior intestine of trout fed either an essential fatty acid-rich diet or a saturated one. The different phospholipid classes are separated, and their fatty acid composition is determined. Fluorescence anisotropy studies are performed using two lipid fluorophores, namely diphenylhexatriene (DPH) and trimethylamino-diphenylhexatriene (TMA-DPH). The results indicate that the usual parameters affecting the lipid fluidity such as the phospholipid:protein (PL:PROT), cholesterol:phospholipid (CHOL:PL), and sphingomyelin:phosphatidylcholine (SP:PC) ratios and the unsaturation of the acyl chains are sufficient to explain the fluidity values determined using DPH, but not those obtained with TMA-DPH as a probe. This fluorophore is assessed to be localized only in the external leaflet of the membrane. Hence, it will be affected by the composition of the major phospholipids of this leaflet, sphingomyelin and phosphatidylcholine.

Effects of dietary cholesterol and phytosterol overload on Wistar rat plasma lipids.

To study the effects of dietary phytosterols on plasma cholesterol, Wistar rats were fed diets containing a cholesterol overload (24 mg/day), to which phytosterols were added or not (24 or 96 mg/day). The cholesterol overload led to a marked increase in cholesterol, mainly linked to very-low-density and low-density lipoproteins. Phytosterols reduced those effects, the highest dose being most efficient. No undesirable effect was observed either on body or on liver weights. This shows that low doses of phytosterols are sufficient to significantly decrease a plasma cholesterol enhancement induced by a dietary cholesterol overload.

Glycaemic and insulinaemic responses in healthy volunteers upon ingestion of maltitol and hydrogenated glucose syrups.

Glycaemic and insulinaemic index of maltitol and maltitol-containing chocolate have been determined in healthy subjects with reference to glucose and compared with those of sucrose solution and sucrose containing chocolate. All maltitol containing products (solutions and chocolate) show a reduced glycaemic index. Insulinaemic index of maltitol solutions is also low, while that of maltitol chocolate remains high.

Effects of dietary phytosterols on liver lipids and lipid metabolism enzymes.

The effects of dietary phytosterols on lipid metabolism have been assessed through determination of liver lipids (sterols and fatty acids) and lipid metabolism enzymes (acetyl-CoA carboxylase, malic enzyme, glucose-6-phosphate dehydrogenase) in rats fed 12 or 24 mg cholesterol a day and 0-96 mg phytosterols. The results indicate that, provided the dietary phytosterol to cholesterol ratio is at least 1 and in the presence of a dietary cholesterol excess, phytosterols do exert a regulatory role through decreases of both acetyl-CoA carboxylase and malic enzyme activities. A ratio of 2 enhances this effect. At the same time, liver fatty acids and cholesterol contents significantly decrease.

Effects of stigmasterol-supplemented diets on fecal neutral sterols and bile acid excretion in rats.

To study the effects of dietary stigmasterol on sterol and bile acids metabolism, Wistar rats were fed diets containing various amounts of stigmasterol. Feeding high stigmasterol doses (11, 26 or 52 mg/day) led to increased cholesterol, coprostanol and bile acid output. These effects were dose-dependent, and likely to be related to the inhibitory effect of plant sterols on cholesterol absorption. Moreover, it accounts for the beneficial effect of the stigmasterol on cholesterol lowering.

Influence of a high-calcium carbonate diet on the incidence of experimental colon cancer in rats.

This study was done to determine whether a high dietary calcium carbonate concentration could protect against colon tumors in rats. Female Wistar rats were randomly assigned to one of four groups and maintained on an 8% lipid diet for an adaptation period of four weeks. All groups were then fed a 24% lipid diet (sunflower oil), with (Groups 2 and 4) or without (Groups 1 and 3) a 1.5% calcium carbonate supplement. They were intrarectally instilled with saline (Groups 1 and 2) or nitrosomethylurea (NMU) (Groups 3 and 4). Fecal sterol output and pH were analyzed for one week each month. Histological analysis was done at the end of the 32-week experiment. No tumors were found in the non-NMU-treated animals. The NMU-treated rats had tumors: 31% in Group 3 and 30% in Group 4. The calcium carbonate supplement had no effect on this incidence. The lipid and cholesterol excretions of the calcium carbonate-supplemented rats were significantly enhanced. The coprostanol output was not altered, although its fecal concentration of the calcium-supplemented rats was decreased. Although neither lipid overload nor NMU treatment altered the fecal pH, it was significantly increased in both calcium carbonate-supplemented groups. These findings suggest that additional calcium as carbonate has no effect on colon tumor incidence, although the fecal composition is altered. The increased pH of the feces due to the carbonate could have the opposite effect to calcium.

Effects of malnutrition and atherosclerosis on the fatty acid composition of plasma phospholipids in the elderly.

The fatty acid profiles of plasma phospholipids have been compared in 53 elderly subjects suffering from malnutrition (group U, 17 subjects) or from atherosclerosis (group A, 15 subjects). A control group was also included in the study (group C, 21 subjects). Main differences were observed in phosphatidylcholine (PC). In group U, the proportion of monounsaturated fatty acids increased in PC, which was reflected by an increase in unsaturated fatty acids without significant modification of essential fatty acids. In group A, no major modification has been observed statistically, although the proportion of saturated fatty acids tended to increase.

A diet moderately enriched in phytosterols lowers plasma cholesterol concentrations in normocholesterolemic humans.

Twelve normolipidic healthy human subjects were fed a diet with or without additional soybean phytosterols for 4 weeks in a crossover design. The order of the treatments was randomized. Phytosterols were added to the diet blended in butter. The dietary ratio cholesterol:phytosterols was 0.7 during the control period (436 mg cholesterol/day and 29 mg phytosterols/day) and 1.88 during the phytosterols period (410 mg cholesterol/day and 740 mg phytosterols/day). Blood cholesterol was 10% lower after subjects consumed the phytosterol-enriched diet than when they consumed the control diet (p < 0.001), which was due to a 15% LDL cholesterol decrease (p < 0.001). The HDL cholesterol:LDL cholesterol ratio was markedly enhanced (+25%) (p < 0.01). These findings suggest that a significant lowering of plasma total and LDL cholesterol can be effected by a modest dietary intake of soybean phytosterols.

Effect of egg consumption in healthy volunteers: influence of yolk, white or whole-egg on gastric emptying and on glycemic and hormonal responses.

The effects of the ingestion of 2 whole eggs (E), 2 egg whites, 2 egg yolks (Y), or no eggs with a standard breakfast on gastric emptying, glycemic and hormonal responses have been studied in 12 healthy young males. E and Y induce a significant delay of gastric emptying, together with reduced blood glucose and insulin peaks (Y). Egg ingestion, whatever the part, increases gastric inhibitory peptide level in blood. Cholecystokinin is enhanced after E or Y ingestion. The results indicate that egg ingestion, especially yolk ingestion, may be of interest in regulating metabolic variables of glucose metabolism.

Dietary calcium salts as protective agents and laminin P1 as a biochemical marker in chemically induced colon carcinogenesis in rats.

To evaluate the protective effect of different calcium forms against colon carcinogenesis, Wistar rats fed a high-fat diet (24%) were supplemented with different chemical forms of dietary calcium and were intrarectally instilled with N-methyl-N-nitrosourea (NMU). Supplemental calcium was administered at 1.5% mineral (w/w of total diet) complexed with either carbonate, gluconate, or lactate in Groups 2, 3, and 4, respectively. The tumor incidence of colon cancer was compared with a control group (Group 1), fed the same diet without supplemental calcium. Colon carcinoma incidence was 31, 33, 13, and 7% in Groups 1, 2, 3, and 4, respectively. Calcium had a significant protective effect against carcinogenesis, and the maximum protective effect was observed with gluconate and lactate forms. Laminin P1 blood level was measured as a tumor marker. Laminin P1 results were compared with the reference group (Group T), fed a standard diet and not NMU instilled. The serum laminin P1 level was significantly higher (p = 0.0001) in NMU-instilled Groups 1, 2, 3, and 4 (0.24 +/- 0.03, 0.93 +/- 1.43, 0.84 +/- 1.33, and 0.41 +/- 0.34 mU/ml respectively) than in the Reference Group T (0.10 +/- 0.05 mU/ml).