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Biomedical subjects

M B Katan

Publications and source records attributed to M B Katan.

At least 19 recordsLinked to original sources
PubMed2006

[Uncertain effects of folic acid on disorders other than neural-tube defects].

Periconceptional supplemention with folic acid prevents neural-tube defects in infants. However, contrary to expectations, clinical trials found no beneficial effect of folic acid on the recurrence of cardiovascular disease. Trial evidence on folic acid and cognitive decline or dementia is scarce, though observational studies suggest that high folate intake may prevent these disorders. In contrast, animal studies suggest that high doses of folic acid enhance the growth of existing tumours. However, recent clinical trials failed to show significant effects of folic acid on cancer incidence and mortality. There are also speculations that folic-acid fortification may increase the number of newborns with the thermolabile variant of methylene tetrahydrofolate reductase. There appears to be little evidence that folic-acid supplementation may mask vitamin-B12 deficiency. In view of these controversies, it is unlikely that The Netherlands will mandate folic-acid fortification of staple foods in the near future. Therefore, women who are planning a pregnancy should be urged to take folic-acid supplements.

Animals↗
PubMed2005

[How much vitamin B6 is toxic?].

Vitamin B6 (pyridoxine) causes neuropathy at intakes of 1000 mg per day or more, which is about 800 times the daily intake from foods. There have also been occasional reports of toxicity at intakes of 100-300 mg per day. The US authorities set the no-observed-adverse-effect-level at 200 mg per day and the safe upper limit at 100 mg per day. A report of neurotoxicity in 2 patients who had taken 24 mg and 40 mg of vitamin B6 per day respectively, may be coincidence rather than a true toxic effect of such relatively low doses. However, physicians need to remain alert to high intakes of vitamin B6 as a cause of unexplained neuropathy.

Dose-Response Relationship, Drug↗
PubMed2005

[Cost of foods fortified with plant sterols refunded by a health insurance company].

The Dutch health insurance company VGZ recently decided to refund part of the cost of using spread, yogurt and milk fortified with plant sterols. Plant sterols lower plasma cholesterol concentrations but they do so less effectively than statins. For health insurance companies wishing to improve the health of their clients, it would be more logical to reimburse costs of folic acid supplements for the prevention of neural tube defects, and vitamin-D-enriched products to prevent fractures in elderly people.

Anticholesteremic Agents↗
PubMed2004

Differential gene expression in rat colon by dietary heme and calcium.

Dietary heme and calcium are alleged modulators of colon cancer risk. Little is known about the molecular and cellular changes in the colon epithelium that are induced by consumption of these unabsorbed nutrients. In this nutrigenomics study, we fed rats high- and low-calcium diets with or without heme. In agreement with previous studies, we found that dietary heme increased the cytotoxicity of fecal water in the colon and elevated epithelial proliferation, a risk factor in colon carcinogenesis. Calcium reduced cytotoxicity and inhibits heme-induced effects. Among 365 colon-expressed genes, we could identify 10 diet-modulated genes that show >2-fold altered expression, of which several are related to colon cell turnover and disease. Mucosal pentraxin (Mptx) was the strongest differentially expressed gene, approximately 10-fold down-regulated by dietary heme and 3-fold up-regulated by calcium. cDNA microarray and quantitative PCR analysis show that calcium significantly inhibits the effects of heme, which correlates with the physiological effects. Our results indicate that Mptx expression is related to colonic cell turnover, and that Mptx might be a marker for diet-modulated mucosal integrity. We also show that Mptx expression is restricted to the intestine, and occurs predominantly in the colon.

Acute-Phase Proteins↗
PubMed2004

Bioavailability and antioxidant effects of olive oil phenols in humans: a review.

OBJECTIVE: We reviewed the bioavailability and antioxidant effects of phenols from extra virgin olive oil. SEARCH STRATEGY: We searched the MEDLINE database for the years 1966-2002. To review the bioavailability of olive oil phenols, we selected animal and human studies that studied the absorption, metabolism, and urinary excretion of olive oil phenols. We also estimated the intake of the various phenols in the Mediterranean area. To review the antioxidant effects of olive oil phenols, we included human and animal studies on the effect of olive oil phenols on markers of oxidative processes in the body. We excluded studies without a proper control treatment and studies in which the antioxidant effects of phenols could not be disentangled from those of the fatty acid composition of olive oil. RESULTS: Bioavailability studies in humans show that the absorption of olive oil phenols is probably larger than 55-66 mol%, and that at least 5% is excreted in urine as tyrosol and hydroxytyrosol. Animal studies suggest that phenol-rich olive oil lowers oxidisability of ex vivo low-density lipoprotein (LDL) particles or lowers markers in urine of oxidative processes in the body. In five out of seven human studies, however, these effects of phenols were not found. There are no data on the phenol concentrations in plasma that are attainable by intake of olive oil. We estimated that 50 g of olive oil per day provides about 2 mg or approximately 13 micromol of hydroxytyrosol-equivalents per day, and that the plasma concentration of olive oil phenols with antioxidant potential resulting from such an intake can be at most 0.06 micromol/l. This is much lower than the minimum concentrations of these phenols (50-100 micromol) required to show antioxidant activity in vitro. CONCLUSION: Although phenols from olive oil seem to be well absorbed, the content of olive oil phenols with antioxidant potential in the Mediterranean diet is probably too low to produce a measurable effect on LDL oxidisability or other oxidation markers in humans. The available evidence does not suggest that consumption of phenols in the amounts provided by dietary olive oil will protect LDL against oxidative modification to any important extent.

Animals↗
PubMed2004

Intake of n-3 fatty acids from fish does not lower serum concentrations of C-reactive protein in healthy subjects.

OBJECTIVE: High-sensitivity C-reactive protein (CRP), a marker of systemic inflammation, is a powerful predictor of cardiovascular risk. We hypothesised that n-3 fatty acids reduce underlying inflammatory processes and consequently CRP concentrations in healthy middle-aged subjects. DESIGN: Placebo-controlled, double-blind study. SUBJECTS: A total of 43 men and 41 postmenopausal women aged 50-70 y. Before and after intervention, we measured serum CRP concentrations with an enzyme immunoassay. INTERVENTIONS: Capsules with either 3.5 g/day fish oil (1.5 g/day n-3 fatty acids) or placebo for 12 weeks. RESULTS: The median CRP change in the fish oil group did not significantly differ from that in the placebo group (0.01 vs -0.17 mg/l, P = 0.057). CONCLUSION: The currently available data--including ours--do not support that beneficial effects on CRP are involved in a mechanism explaining the protective effect on heart disease risk of n-3 fatty acids as present in fish.

Aged↗
PubMed2004

Dietary fructo-oligosaccharides and inulin decrease resistance of rats to salmonella: protective role of calcium.

BACKGROUND: We have shown recently that rapid fermentable fructo-oligosaccharides (FOS) decreased resistance of rats towards salmonella. It is not known whether inulin (which is fermented more gradually) has similar effects or whether buffering nutrients can counteract the adverse effects of rapid fermentation. AIMS: To compare the effects of dietary inulin and FOS on resistance of rats to Salmonella enterica serovar Enteritidis and to determine whether calcium phosphate counteracts the effects of fermentation. METHODS: Male Wistar rats (n = 8 per group) were fed a human "Western style diet". Diets with 60 g/kg cellulose (control), FOS, or inulin had either a low (30 mmol/kg) or high (100 mmol/kg) calcium concentration. After an adaptation period of two weeks, animals were orally infected with 2 x 10(9) colony forming units of Salmonella enterica serovar Enteritidis. Colonisation of salmonella was determined by quantification of salmonella in caecal contents. Translocation of salmonella was quantified by analysis of urinary nitric oxide metabolites in time. RESULTS: Inulin and FOS decreased intestinal pH and increased faecal lactobacilli and enterobacteria. Moreover, both prebiotics increased the cytotoxicity of faecal water and faecal mucin excretion. Both prebiotics increased colonisation of salmonella in caecal contents and enhanced translocation of salmonella. Dietary calcium phosphate counteracted most of the adverse effects of inulin and FOS. CONCLUSIONS: Both inulin and FOS impair resistance to intestinal infections in rats. This impairment is partially prevented by dietary calcium phosphate. The results of the present study await verification in other controlled animal and human studies.

Animals↗
PubMed2004

The rise and fall of postprandial lipids.

The remnants of absorbed fat particles which circulate after a meal might cause atherosclerosis, but such a causal role is still unproven. High levels of such lipoprotein remnants are often found in patients with the metabolic syndrome. Increased activity and weight loss will diminish the cardiovascular risk factors caused by this syndrome including elevations of postprandial remnants.

Causality↗
PubMed2003

Trans fatty acids, HDL-cholesterol, and cardiovascular disease. Effects of dietary changes on vascular reactivity.

A high consumption of trans fatty acids increases the risk of cardiovascular disease (CVD). We investigated whether this increase in risk was due to the decrease in serum HDL-cholesterol by trans fatty acids, because low concentrations of serum HDL-cholesterol also increase risk of CVD. Flow-mediated vasodilation (FMD) was used as an endpoint in dietary interventions that were designed to change the concentration of serum HDL-cholesterol within 4 weeks in healthy volunteers. Replacement of 10% of energy from saturated by trans fatty acids decreased serum HDL-cholesterol by 21 % and impaired FMD. However, a replacement of monounsaturated fats by carbohydrates did not impair FMD, although it decreased serum HDL-cholesterol by 13%. Acute postprandial impairments of FMD by either trans fats or saturated fats were not found, suggesting that long-term effects are responsible for the detrimental effect of trans fats on health. However, the role of serum HDL-cholesterol appears to be less than we expected.

Adult↗
PubMed2003

[Nutrition and health--sense and nonsense regarding food supplements and functional foods].

A functional food is a proprietary food or beverage with a health-related claim. Such functional foods could make it easier to maintain a healthy diet. Unfortunately, in many countries regulations allow manufacturers to imply that a food promotes health without providing proper scientific evidence. At the same time, regulations may forbid claims that a food product prevents disease, even when it does (e.g. folic acid, which reduces the risk of neural tube defects). Functional foods may have beneficial health effects compared with traditional foods in some cases, but current legislation in the Netherlands cannot protect consumers from misleading claims.

Dietary Supplements↗
PubMed2003

n-3 fatty acids in human fat tissue aspirates are stable for up to 6 y.

OBJECTIVES: The content of n-3 (omega-3) polyunsaturated fatty acids in fat tissue is a valid indicator of their long-term consumption. We studied the stability of n-3 fatty acids in human subcutaneous fat microbiopsies after 6 and 11 y of storage. DESIGN: Microbiopsies were taken from a lump of human adipose tissue and stored at +20 and -80 degrees C. SETTING: Laboratory study. RESULTS: After 5.6 y at -80 degrees C the proportion of six out of seven highly polyunsaturated fatty acids varied between 91 and 102% (mean 97%) of their baseline values. Storage at +20 degrees C yielded recoveries between 82 and 105%. After 11 y at -80 degrees C the proportions in the original lump of tissue ranged from 88 to 101% (mean 94%). CONCLUSION: n-3 fatty acids in stored fat tissue aspirates are stable for 6-11 y, and are suitable markers of baseline diet in long-term epidemiological studies. SPONSORSHIP: Wageningen Centre for Food Sciences.

Adipose Tissue↗
PubMed2003

Rationale and design of a randomised controlled clinical trial on supplemental intake of n-3 fatty acids and incidence of cardiac arrhythmia: SOFA.

BACKGROUND: Evidence from earlier studies indicates that intake of very long-chain n-3 polyunsaturated fatty acids (n-3 PUFA, also named omega-3 fatty acids) as present in fish oil reduces the risk of sudden death. Sudden death forms a major part of mortality from cardiovascular disease and is in most cases a direct consequence of cardiac arrhythmia. n-3 PUFA may exert their protective effect through reducing the susceptibility for cardiac arrhythmia. OBJECTIVE: To investigate the effect of n-3 PUFA on the incidence of recurrent ventricular arrhythmia. This paper presents the rationale, design and methods of the Study on Omega-3 Fatty acids and ventricular Arrhythmia (SOFA) and discusses problems encountered in conducting a multicentre clinical trial on food. DESIGN: A randomised, parallel, placebo-controlled, double blind intervention study, which obeys the guidelines for Good Clinical Practice. SETTING: Multiple cardiology centres in Europe. SUBJECTS: A total of 500 patients with an implantable cardioverter defibrillator (ICD). An ICD detects, treats and stores cardiac arrhythmic events in its memory chip. INTERVENTIONS: Patients receive either 2 g/day of fish oil, containing approximately 450 mg eicosapentaenoic acid and 350 mg docosahexaenoic acid, or placebo for 12 months. PRIMARY OUTCOME: Spontaneous ventricular tachyarrhythmias as recorded by the ICD or all-cause mortality. CONCLUSION: SOFA is designed to answer the question whether intake of n-3 PUFA from fish-a regular food ingredient-can reduce the incidence of life-threatening cardiac arrhythmia. If this proves to be true, increasing the intake of n-3 PUFA could be an easy, effective and safe measure to prevent fatal arrhythmia in the general population.

Anti-Arrhythmia Agents↗
PubMed2002

[Nutrition and health].

In this issue the journal publishes the first of a series of articles on nutrition and health. Dutch investigators have contributed to food research since the work of Eijkman and co-workers on vitamins at the end of the nineteenth century. During the last forty years, food research has moved towards investigating the role of nutrients in the prevention of diseases with a long latency and in specific population groups, e.g. the elderly and people with hypertension or obesity. More recent research has focused on enriched food products and biotechnologically manufactured nutritional elements. The series will discuss subjects such as dietary reference intakes, dietary infections, dietary requirements of the elderly and patients in hospitals and rehabilitation institutions, and the beneficial and detrimental effects of alcohol consumption. This will enable the clinician to provide answers to patients' questions regarding their diet and to recommend a healthy diet.

Diet↗
PubMed2002

ATP binding cassette G5 C1950G polymorphism may affect blood cholesterol concentrations in humans.

ATP binding cassette protein G5 (ABCG5) and G8 (ABCG8) may be involved in the regulation of intestinal cholesterol absorption. Therefore, genetic variation at these loci may affect blood cholesterol concentrations by influencing dietary responsiveness. We studied the association between the ABCG5 C1950G (Gln640Glu) polymorphism and blood cholesterol concentrations in 486 subjects and responsiveness to dietary cholesterol in 99 participants in dietary trials. Mean baseline cholesterol concentrations were 0.65 +/- 0.22 mmol/l higher in 13 subjects with the G/G genotype than in 473 carriers of the C-allele (95% confidence interval 0.22-1.08 mmol/l). The response of serum total cholesterol to dietary cholesterol tended to be larger in subjects with the G/G genotype as compared with carriers of the C-allele. We suggest that the ABCG5 G/G genotype may increase serum cholesterol concentrations and, possibly responsiveness to dietary cholesterol in humans. Studies in other populations and experimental settings are required to confirm or reject this hypothesis.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2002

Trans monounsaturated fatty acids and saturated fatty acids have similar effects on postprandial flow-mediated vasodilation.

OBJECTIVE: Several studies suggest that a fatty meal impairs flow-mediated vasodilation (FMD), a measure of endothelial function. We tested whether the impairment was greater for trans fats than for saturated fats. We did this because we previously showed that replacement of saturated fats by trans fats in a controlled diet decreased FMD after 4 weeks. DESIGN: We fed 21 healthy men two different test meals with 0.9-1.0 g fat/kg body weight in random order: one rich in saturated fatty acids (Sat), mainly from palm kernel fat, and one rich in trans fatty acids (Trans) from partially hydrogenated soy bean oil. The study was performed in our metabolic ward. We had complete data for both diets of 21 men. RESULTS: FMD increased from a fasting value of 2.3+/-2.0% of the baseline diameter to 3.0+/-1.7% after the Sat test meal (95% CI for change -0.33, 1.70) and from 2.7+/-2.3 to 3.1+/-2.0% after the Trans test meal (95% CI for change -0.57, 1.29). The increase after the Sat meal was 0.22 (-1.18-1.61) FMD% higher than after the Trans meal. Serum triacylglycerols increased by 0.46+/-0.36 mmol/l after the Sat test meal and by 0.68+/-0.59 mmol/l after the Trans test meal; a difference of 0.23 (0.07, 0.39) mmol/l. Serum HDL-cholesterol was hardly affected by the test meals. The activity of serum paraoxonase, an esterase bound to HDL, increased slightly after the two test meals but the difference between meals was not significant. CONCLUSION: FMD was not impaired and not different after test meals with saturated or trans fatty acids. Thus, differences in long-term effects of these fats are not caused by differences in acute effects on the vascular wall.

Adult↗
PubMed2002

Apolipoprotein E polymorphism and serum lipid response to plant sterols in humans.

BACKGROUND: The apolipoprotein E polymorphism may influence the absorption of cholesterol from the intestine and thus the response of serum cholesterol to diet. We decided to use plant sterols to investigate this and studied whether the cholesterol-lowering effect of plant sterols differed between subjects with different apolipoprotein E genotyes. DESIGN: Thirty-one healthy subjects with the E3/4 or E4/4 genotype and 57 with the E3/3 genotype were fed sterol-enriched margarine or control margarine for 3 weeks each in a blind randomised cross-over design. The sterol margarine provided 3.2 g of plant sterols daily, was low-fat, and had the same fatty acid composition as the control margarine. Subjects used the margarines as part of their usual diet, which was fairly low in cholesterol (mean, 175 mg per day). The mean (+/- standard deviation) age of the subjects was 25 (+/- 11) years. RESULTS: The apolipoprotein E polymorphism did not significantly affect the responses of total and LDL cholesterol. The decrease in total cholesterol was 0.36 mmol L-1 (7.4%) in the E3/3 subjects and 0.31 mmol L-1 (5.7%) in the epsilon 4 subjects (P = 0.50) and that in LDL cholesterol was 0.34 mmol L-1 (12.2%) in the E3/3 subjects and 0.32 mmol L-1 (9.8%) in the epsilon 4 subjects (P = 0.68). CONCLUSION: The serum cholesterol response to plant sterols is not affected by the apolipoprotein E polymorphism in healthy subjects who consume a low-cholesterol diet.

Adult↗
PubMed2002

The decrease in body fat in mice fed conjugated linoleic acid is due to increases in energy expenditure and energy loss in the excreta.

We carried out energy balance studies in four groups of young, growing, 5-wk-old Balb-C mice (n = 12/group) that were either food restricted or nonrestricted and fed high fat diets (38 energy%) with or without 0.93 g/100 g conjugated linoleic acid (CLA) for 39 d. The energy in carcasses, excreta and food was measured in a bomb calorimeter. CLA lowered the percentage of the energy intake that was stored in the body from 1.9 +/- 0.8 to -2.3 +/- 0.7% (mean +/- SD, P < 0.05) in the nonrestricted mice and from 1.4 +/- 1.3 to -2.9 +/- 0.7% (P < 0.05) in the restricted mice. Thus, the CLA-treated mice had a net loss of body energy. The percentage of the energy intake eliminated in the excreta increased from 7.6 +/- 0.9% in controls to 8.7 +/- 1.0% (P < 0.05) in the CLA-treated mice that were nonrestricted and from 7.3 +/- 0.8 to 8.4 +/- 0.6 (P < 0.05) in the restricted mice. The amount of energy ingested minus the amount retained in carcasses and excreta equals the energy expenditure. The percentage of the energy intake that was expended as heat increased from 90.5 +/- 1.2 in controls to 93.6 +/- 1.5% (P < 0.05) in the CLA-treated nonrestricted mice and from 91.3 +/- 1.5 to 94.5 +/- 1.0% (P < 0.05) in the restricted mice. The lower energy storage in the CLA-fed mice was accounted for by an increase in the energy expenditure (74%) and by an increase in energy lost in the excreta (26%). Feeding CLA also increased liver weight, which may warrant further studies on the safety of CLA.

Adipose Tissue↗