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Biomedical subjects

H M Roche

Publications and source records attributed to H M Roche.

27 records · Page 2Linked to original sources
PubMed1999

The effect of low and moderate fat intakes on the postprandial lipaemic and hormonal responses in healthy volunteers.

Present literature indicates that whereas an acute fat intake of 5 g does not elicit a postprandial triacylglycerolaemic response, 20 g of fat does. Since 67% of fat intake occasions involve fat doses of less than 20 g, the present study examined the effect of a relatively low-fat (LF) meal (0.2 g/kg body weight; mean 14 g) on postprandial triacylglycerol (TAG) metabolism, compared with a high-fat (HF) meal (0.6 g/kg body weight; mean 43 g), a fat dose which is more typical of laboratory studies. Plasma- and chylomicron-TAG concentrations increased significantly (P < or = 0.001) following both meals, and the increase was significantly (P < or = 0.02) greater after the HF meal. The postprandial areas under the curves and maximal postprandial TAG concentrations for plasma- and chylomicron-TAG were significantly higher following the HF meal (P < or = 0.05). Postprandial plasma insulin and gastric inhibitory polypeptide concentrations increased significantly (P < or = 0.001) after each meal, but there was no difference between the two meals. These data show that modest amounts of fat in a meal will elicit a measurable postprandial TAG response. Since postprandial lipaemia affects the composition and concentration of the TAG- and cholesterol-rich lipoproteins, controlling dietary TAG supply may influence the metabolic fate of these lipoproteins.

Adult↗
PubMed1998

The effect of test meal monounsaturated fatty acid: saturated fatty acid ratio on postprandial lipid metabolism.

Epidemiological evidence shows that a diet high in monounsaturated fatty acids (MUFA) but low in saturated fatty acids (SFA) is associated with reduced risk of CHD. The hypocholesterolaemic effect of MUFA is known but there has been little research on the effect of test meal MUFA and SFA composition on postprandial lipid metabolism. The present study investigated the effect of meals containing different proportions of MUFA and SFA on postprandial triacylglycerol and non-esterified fatty acid (NEFA) metabolism. Thirty healthy male volunteers consumed three meals containing equal amounts of fat (40 g), but different proportions of MUFA (12, 17 and 24% energy) in random order. Postprandial plasma triacylglycerol, apolipoprotein B-48, cholesterol, HDL-cholesterol, glucose and insulin concentrations and lipoprotein lipase (EC 3.1.1.34) activity were not significantly different following the three meals which varied in their levels of SFA and MUFA. There was a significant difference in the postprandial NEFA response between meals. The incremental area under the curve of postprandial plasma NEFA concentrations was significantly (P = 0.03) lower following the high-MUFA meal. Regression analysis showed that the non-significant difference in fasting NEFA concentrations was the most important factor determining difference between meals, and that the test meal MUFA content had only a minor effect. In conclusion, varying the levels of MUFA and SFA in test meals has little or no effect on postprandial lipid metabolism.

Adult↗
PubMed1998

Effect of long-term olive oil dietary intervention on postprandial triacylglycerol and factor VII metabolism.

Although the beneficial effects of Mediterranean-type diets, which are rich in olive oil, a good source of monounsaturated fatty acids (MUFAs), are generally accepted, little is known about the effects of long-term dietary MUFA intake on postprandial lipoprotein metabolism and hemostasis. This study used a single-blind, randomized, crossover design to investigate the relative effects of a long-term dietary olive oil intervention and a control [saturated fatty acid (SFA)-enriched] diet on postprandial triacylglycerol metabolism and factor VII activity. The postprandial response to a standard test meal was investigated in 23 healthy men who adhered to both diets for 8 wk. cis-MUFAs were successfully substituted for SFAs in the MUFA diet without affecting total dietary fat or energy intakes. The long-term dietary MUFA intervention significantly reduced plasma and LDL-cholesterol concentrations (P = 0.01). Postprandial triacylglycerol concentrations were significantly greater in the early postprandial period after the MUFA diet (P = 0.003). Postprandial factor VII activation and the concentration of the factor VII antigen were significantly lower after the MUFA diet (P = 0.04 and P = 0.006, respectively). This study showed that isoenergetic substitution of MUFAs for SFAs reduces plasma cholesterol and reduces the degree of postprandial factor VII activation. The alterations in the postprandial triacylglycerol response suggest a greater rate of dietary fat absorption and postprandial triacylglycerol metabolism after a diet rich in MUFAs. This study presents new insights into the biochemical basis of the beneficial effects associated with long-term dietary MUFA consumption, which may explain the lower rates of coronary mortality in Mediterranean regions.

Adult↗
PubMed1998

The effect of acute carbohydrate load on the monophasic or biphasic nature of the postprandial lipaemic response to acute fat ingestion in human subjects.

Previous studies in this laboratory have elicited a monophasic response in postprandial plasma triacylglycerol (TAG) level with fat intakes of 0.5 g fat/kg body weight accompanied by about 17 g carbohydrate as lactose. Recent studies involving the same level of fat with a higher level of carbohydrate, 136 g of which 60 g was sucrose, appeared to elicit a biphasic response. The present study compared these two test meals and showed a significant meal x time interaction for plasma total TAG (P = 0.0228) reflecting a monophasic response with the lower-carbohydrate test meal. The higher-carbohydrate meal induced significantly higher insulin and glucose-dependent insulinotropic polypeptide responses (P = 0.0009 and P = 0.0041 respectively). A significant meal x time interaction was seen for plasma non-esterified fatty acids (P = 0.0437). The biphasic plasma TAG response seen with the high-carbohydrate meal largely reflected the TAG-rich lipoprotein (TRL) or chylomicron fraction, which would tend to suggest a biphasic pattern of absorption. This was borne out by TRL-TAG fatty acid compositions. Both peak in the biphasic response showed active incorporation of the main dietary fatty acids, 18:1n-9, 18:2n-6 and 18:3n-3 into TRL-TAG. These results indicate that under the specific test-meal conditions used in the present study, a biphasic pattern of fat absorption was seen.

Adult↗
PubMed1997

Postprandial coagulation factor VII activity: the effect of monounsaturated fatty acids.

The present study investigated the effect of monounsaturated fatty acids (MUFA) on postprandial coagulation factor VII activity. Fifteen healthy male volunteers consumed three meals containing equal amounts (40 g) of fat, but providing different proportions of MUFA (12, 17 and 24% energy) in random order. Fasting and postprandial blood samples were drawn every hour for 9 h. The magnitude of the postprandial triacylglycerolaemic response and the postprandial plasma non-esterified fatty acid (NEFA) concentrations were not significantly different following the three meals. Coagulation factor VII was activated during postprandial triacylglycerolaemia but the area under the curve of postprandial coagulation factor VII activity was not significantly different following the three meals. Regression analysis showed that fasting factor VII activity was the single most important factor affecting postprandial factor VII activity, irrespective of plasma lipid concentrations and meal fat composition. Peak postprandial factor VII activity was attained significantly earlier following the high-MUFA meal compared with the low-MUFA meal (6.33 (SD 2.16)h, 3.60 (SD 1.81)h respectively; P = 0.016). Regression analysis showed that meal MUFA content was the primary determinant of time to peak postprandial factor VII activity. Although the magnitude of postprandial coagulation factor VII activity was not affected by meal MUFA content, peak postprandial factor VII activity occurred earlier and fasting activity levels were quickly restored following the high-MUFA meal. A short-lived increase in factor VII activity may be more beneficial than a prolonged thrombotic response.

Adolescent↗
PubMed1996

Postprandial triacylglycerolaemia: the effect of low-fat dietary treatment with and without fish oil supplementation.

OBJECTIVE: This study investigated whether a low-dose of fish oil had the ability to prevent the adverse effects associated with low-fat dietary treatment, namely elevated plasma triacylglycerol (TAG) and reduced high density lipoprotein (HDL) cholesterol concentrations. DESIGN: Thirty-two healthy volunteers participated in the trial, which consisted of four study groups (n = 8): low-fat diet with fish oil supplementation, low-fat diet without fish oil supplementation, full-fat diet with fish oil supplementation and full-fat diet without fish oil supplementation. Low-fat dietary treatment reduced dietary energy derived from fat by at least 10% and the low-dose of fish oil provided 1 g n-3 polyunsaturated fatty acids (PUFA) daily. The postprandial response to a fat-rich test meal (0.5 g/kg pre-trial body weight) was investigated before and after 16 weeks dietary intervention. RESULTS: Fasting plasma TAG concentrations were significantly (P < or = 0.05) reduced by fish oil supplementation and significantly (P < or = 0.05) increased by the low-fat diet alone but not significantly affected following the low-fat diet with fish oil supplementation. The postprandial TAG response was significantly (P < or = 0.05) increased following the low-fat diet with fish oil supplementation. CONCLUSION: This study demonstrated that some of the deleterious effects of a low-fat diet, reduced concentrations of the cardioprotective HDL2 cholesterol fraction and increased fasting plasma TAG concentrations were prevented when a low dose of fish oil was provided with a low-fat diet. However postprandial triacylglycerolaemia is adversely affected when the low-fat diet was supplemented with fish oil.

Adult↗
PubMed1993

Elevated intracellular dCTP levels reduce the induction of GC-->AT transitions in yeast by ethyl methanesulfonate or N-methyl-N'-nitro-N- nitrosoguanidine but increase alkylation-induced GC-->CG transversions.

The effect of an increased intracellular dCTP:dTTP ratio on the specificities of ethyl methanesulfonate (EMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) mutagenesis was examined in the yeast Saccharomyces cerevisiae. To do so, we used a dCMP deaminase-deficient (dcd1) strain having a dCTP:dTTP ratio > 77-fold larger than its isogenic wild-type parent under the treatment conditions employed. This DNA precursor imbalance lowered the frequencies of EMS- or MNNG-induced SUP4-o mutations by 75 or 45%, respectively, relative to the corresponding values for the wild-type strain. A total of 405 SUP4-o mutations produced by the alkylating agents in the dcd1 background were characterized by DNA sequencing and the mutational spectra were compared to those for 399 mutations induced in the wild-type parent and 207 mutations that arose spontaneously in the dcd1 strain. Unexpectedly, the frequencies of EMS- and MNNG-induced GC-->AT transitions in the dcd1 strain were found to be reduced by 93 and 68%, respectively, considerably more than the decreases for the overall SUP4-o mutation frequencies. The differences were due mainly to substantial increases in the frequencies of GC-->CG transversions. Although these events were the predominant type of spontaneous substitution in the dcd1 strain, they were more frequent after alkylation treatment and were distributed differently than the spontaneous GC-->CG transversions. Preferences for the EMS- or MNNG-induced GC-->AT transitions to occur at GC sites having the guanine located on the transcribed strand or preceded by a 5' purine, respectively, also were diminished in the dcd1 strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkylation↗
PubMedDate not supplied

Thermolabile methylenetetrahydrofolate reductase (C677T): frequency in the Irish population.

BACKGROUND: The genetic variation which underlies the thermolability and low enzyme activity of 5,10-methylenetetrahydrofolate reductase (MTHFR; C677T) has been extensively studied in many populations, including the Irish population. AIM: To describe the examination of the C677T substitution in two new control samples drawn from the Irish population. METHODS: A collection of 487 serum samples was obtained through the blood transfusion services of both the Republic of Ireland and Northern Ireland and a further 115 samples from volunteers. RESULTS: In both samples, the frequency of the thermolabile/low enzyme activity allele (T) was higher than that previously reported for the Irish population. CONCLUSION: This finding thus supports the need for a greater use of internal control/family-based association studies, as opposed to the classic case control study design, when assessing the contribution of the MTHFR T allele to disease processes.

Adult↗