Biomedical subjects

J T Snook

Publications and source records attributed to J T Snook.

At least 19 recordsLinked to original sources

PubMed2002

Does increased leukotriene B4 in type 1 diabetes result from elevated cholesteryl ester transfer protein activity?

Elevated cholesteryl ester transfer protein (CETP) activity has been reported in type 1 diabetic subjects and may be one cause of the high incidence of macrovascular complications in these patients. LDL delivers arachidonic acid (AA), in the form of cholesteryl ester (CE), to cells such as monocytes and fibroblasts, as precursor for eicosanoid synthesis. We discovered that AA content in LDL CE was significantly correlated with CETP activity, even after controlling for CETP concentration, in type 1 diabetic children. The production of LTB(4), a potent chemotactic and pro-inflammatory factor which plays a role in atherogenesis, has been shown to be increased in type 1 diabetic patients. We hypothesized that in these subjects, increased AA content in LDL CE, resulting from increased CETP activity and transient hyperinsulinemia, may lead to enhanced synthesis of LTB(4) and subsequently the higher incidence of cardiovascular disease.

Arachidonic Acid↗

PubMed2001

Cholesteryl ester transfer and cholesterol esterification in type 1 diabetes: relationships with plasma glucose.

The activities of two crucial enzymes of reverse cholesterol transport, cholesterol ester transfer protein (CETP) and lecithin:cholesterol acyltransferase (LCAT), and their relationships with lipid profile and fasting plasma glucose were examined in 35 type 1 diabetic children. The CETP and LCAT activities were significantly lower (p<0.05) in the 4 subjects with normal fasting plasma glucose levels (<6.39 mmol/l) than in the 28 with high plasma glucose levels (CEPT activity, 10.63+/-3.81 vs. 32.18+/-13.94 nmol/ml h; LCAT activity, 25.52+/-4.53 vs. 39.52+/-12.52 nmol/ml h; both p<0.05). The subjects with high plasma glucose levels also had higher total and LDL-cholesterol than those with normal glucose levels. CETP activity was positively correlated with fasting plasma glucose, CETP concentration, LCAT activity, total cholesterol, free cholesterol, LDL-C, and LDL-cholesteryl ester, while negatively correlated with cholesteryl ester to free cholesterol ratio, LDL triglyceride to protein ratio, and LDL triglyceride to cholesteryl ester ratio. LCAT activity was found to positively correlate with CETP activity, total cholesterol, free cholesterol, LDL-C, CETP concentration, and LDL-cholesteryl ester, while it negatively correlated with cholesteryl ester to free cholesterol ratio. The results observed in type 1 diabetic subjects suggest that (1) accelerated LCAT and CETP activities may result in the accumulation of LDL-cholesteryl ester; and (2) fasting plasma glucose may be a major determinant of CETP activity.

Blood Glucose↗

PubMed2001

Risk factors for coronary heart disease in type 1 diabetic children: the influence of apoE phenotype and glycemic regulation.

The effects of apolipoprotein E (apoE) phenotype and glycemic regulation on plasma levels of lipids and lipoproteins, low density lipoprotein (LDL) composition, LDL particle size, and LDL oxidation were examined in 35 type 1 diabetic children aged 5-12 years. All subjects were classified according to glycemic regulation (HbA(1c)<8% vs. HbA(1c)>8%). ApoE phenotypes were identified by isoelectric focusing (IEF) followed by immunoblotting. Results from two-way analysis of variance (ANOVA) showed that subjects with apoE 4/3 and HbA(1c)>8% had higher concentrations of total cholesterol (TC), LDL-cholesterol (LDL-C), and LDL-cholesterol ester (LDL-CE) than subjects with the same apoE phenotype and HbA(1c)<8%. LDL particles in all subjects were classified as the subclass pattern A. Both LDL particle size and susceptibility of LDL to oxidation were not different among subjects stratified by apoE phenotype. In conclusion, children with type 1 diabetes mellitus included in this study did not have high-risk lipoprotein profiles at this early stage of life. However, there was some indication that those with the apoE 4/3 phenotype were more likely to have more favorable lipid profiles when HbA(1c) levels were <8%.

Apolipoproteins E↗

PubMed2001

The cholesterolaemic effects of dietary fats in cholesteryl ester transfer protein transgenic mice.

In order to investigate the role of cholesteryl ester transfer protein (CETP) in the cholesterolaemic response to dietary fats, we analysed plasma lipid profiles of CETP-transgenic and control C57BL/6 mice fed standard chow (AIN-93G; AIN), a low-fat diet, and diets high in butter (saturated fatty acids; SFA), high-oleic acid safflower oil (monounsaturated fatty acids; MUFA), and safflower oil (polyunsaturated fatty acids; PUFA) for 5 weeks. Each group contained four or five mice. There were significant diet and dietxgenotype effects on plasma total cholesterol (TC; and respectively), liver TC ( and respectively), and esterified cholesterol (EC; and respectively); diet effects on plasma triacylglycerol liver free cholesterol and body weight a genotype effect on body-weight gain and a dietxgenotype effect on energy intake In transgenic mice the SFA diet caused significantly higher plasma TC than the PUFA diet In control mice MUFA and PUFA diets, but not the SFA diet, caused significantly higher plasma TC than the low-fat and AIN diets Transgenic mice fed PUFA had lower plasma TC while transgenic mice fed MUFA had lower LDL+VLDL-cholesterol than controls in the same dietary groups. Transgenic mice fed MUFA and PUFA diets also had significantly higher liver TC and respectively) and EC and respectively) than controls fed the same diets. In the present study we showed that: (1) CETP transgenic mice had a cholesterolaemic response to dietary fats similar to that in human subjects; (2) CETP transgenic mice fed PUFA showed significantly lower plasma TC, while those fed MUFA had lower LDL+VLDL-cholesterol than controls; (3) hepatic accumulation of cholesterol, possibly resulting from the combination of the enhanced cholesteryl ester transfer to apolipoprotein B-containing lipoproteins and increased hepatic uptake of cholesterol, may contribute to the cholesterol-lowering effect of MUFA and PUFA in CETP-transgenic mice; (4) CETP may play a role in appetite and/or energy regulation.

Animal Nutritional Physiological Phenomena↗

PubMed1999

Mechanisms mediating lipoprotein responses to diets with medium-chain triglyceride and lauric acid.

Medium-chain triglycerides (MCT) are often used in specialized formula diets or designer fats because of their special properties. Yet their influence on lipid metabolism is not completely understood. In this two-period cross-over study, the effects of MCT (8:0 + 10:0) in contrast to a similar saturated fatty acid (12:0) were compared. Eighteen healthy women ate a baseline diet [polyunsaturated (PUFA)/saturated fat = 0.9] for 1 wk. Then, they consumed test diets (PUFA/saturated fat = 0.2) for 4 wk. Monounsaturated fat and cholesterol were constant in baseline and treatment diets. MCT and 12:0, substituted for part of the PUFA, provided 14 energy (en)% of the test diets. In comparison to the PUFA baseline diet, a 16% increase in mean serum low density lipoprotein (LDL)-cholesterol (C) on the 12:0 diet was accompanied by a 21% decrease in mean receptor-mediated degradation of LDL by freshly isolated mononuclear cells (MNC) in vitro. The MNC assay theoretically gives an indication of receptor-mediated degradation of LDL. In contrast, the MCT diet raised mean receptor-mediated degradation of LDL by 42%, a finding out of line with the mean 11% increase in serum LDL-C. Perhaps MCT, by increasing the rate of LDL-C production, overcame the rate of LDL-C clearance. The 12:0 diet enhanced some factors involved in reverse cholesterol transport (e.g., high density lipoprotein fractions) while MCT had a different or less pronounced effect. The overall effects of MCT on cholesterol metabolism may or may not be desirable, whereas those of 12:0 appear largely undesirable as previously reported.

Adult↗

PubMed1999

Sandwich enzyme-linked immunosorbent assay for plasma cholesteryl ester transfer protein concentration.

OBJECTIVES: Cholesteryl ester transfer protein (CETP) mediates the transfer of HDL cholesterol to apoB-containing lipoproteins. Its mass and activity are increased in several pro-atherogenic conditions. The objective of this study is to develop a cost- and time-effective sandwich ELISA for plasma CETP concentration. DESIGN AND METHODS: Monoclonal anti-CETP, TP20, was used as the capture antibody, while the other biotinylated monoclonal anti-CETP, TP2, was used for detection. The results were expressed in an arbitrary unit, ng biotin-TP2 bound per microl plasma. Plasma CETP concentrations, activities and their relationship were assessed in 35 IDDM children. RESULTS: The assay had an intra-assay CV of 8.75% and an inter-assay CV under 10%. Plasma CETP concentration of these subjects ranged from 0.36-1.89 ng biotin-TP2/microL. CETP concentration was significantly correlated with CETP activity (r = 0.51, p < 0.01). CONCLUSION: The sandwich ELISA we have developed carried sufficient sensitivity for assaying plasma CETP concentration in human.

Antibodies, Monoclonal↗

PubMed1999

Effect of synthetic triglycerides of myristic, palmitic, and stearic acid on serum lipoprotein metabolism.

OBJECTIVES: To determine relative effects of diets high in synthetic sources of myristic (14:0), palmitic (16:0) or stearic (18:0) acid on concentrations and metabolism of serum lipoproteins. DESIGN: Eighteen healthy women participated in a three-way cross-over study for five week periods separated by seven week washout periods, diets were assigned in random order. SUBJECTS: Premenopausal women, not on medication, were from three races (Caucasian, African-American, Asian) and four apolipoprotein E phenotype groups (3/3, 3/2, 4/3, and 4/2). INTERVENTION: During the first week the subjects consumed a baseline diet providing 11 energy (en)% saturated fat, 10en% polyunsaturated fat and 14en% monounsaturated fat. Followed by test diets with 19en% saturated fat (including 14en% test saturated fatty acid), 3en% polyunsaturated fat, and 14en% monounsaturated fat for four weeks. Synthetic fats (trimyristin, tripalmitin, and tristearin) were used in blends with natural fats and oils. RESULTS: Mean concentrations of serum total, esterified and LDL cholesterol were significantly lower after 18:0 than after 16:0 (n = 16-18, P < 0.01 for treatment effect). Myristic acid (14:0) had an intermediate effect. Receptor-mediated degradation of 125I-LDL in mononuclear cells obtained from the subjects was lower after 16:0 than after 14:0 and 18:0 (n = 16-18, P=0.05 for treatment effect). Differences in the digestibilities of the fats were not a major factor in the results. Strong cholesterolemic responses to the 16:0 diet were partly explained by apoE phenotype. CONCLUSIONS: As noted previously, stearic acid was neutral compared to 14:0 and 16:0. In contrast to studies involving natural fats, 14:0, fed as a synthetic triglyceride, was less cholesterolemic than 16:0 in a majority of subjects. ApoE phenotype influenced the cholesterolemic response particularly when diets high in 16:0 were eaten.

Adult↗

PubMed1998

Effect of apolipoprotein E polymorphism on serum lipoprotein response to saturated fatty acids.

This report summarizes two studies which investigated the effects of apolipoprotein E (apoE) polymorphism on the serum total cholesterol (TC) and lipoprotein cholesterol responses to 8:0 + 10:0 and 12:0 diets (Study I) and 14:0, 16:0 and 18:0 diets (Study II). Eighteen healthy premenopausal women (3 apoE 3/2, 12 apoE 3/3, 3 apoE 4/3) in study I and another 18 healthy premenopausal women (4 apoE 3/2, 10 apoE 3/3, 3 apoE 4/3, 1 apoE 4/2) in study II consumed a baseline diet providing 40 en% total fat, 11 en% 18:2, 15 en% 18:1, 11.5 en% saturated fat for the first week of each 5-wk period. The experimental diets for both studies provided 40 en% total fat, 13-14 en% as one of five test saturated fatty acids (SFA), 14-16 en% 18:1, and 3-4 en% 18:2. Analysis by apoE phenotypes showed that both the 8:0 + 10:0 diet and the 12:0 diet in Study I induced significant increases in serum TC in subjects with different apoE phenotypes with the exception of apoE 3/2 in the medium-chain triglyceride group. In contrast, in Study II, individuals with apoE 4/3 consuming the 14:0 diet showed significant increases in serum TC, high density lipoprotein-cholesterol (HDL-C), and HDL2-C, but the same subjects consuming the 16:0 diet showed significant increases in serum TC and low density lipoprotein-cholesterol. The findings from both studies indicated serum lipoprotein responses to SFA were different and the variation of responsiveness may be regulated, at least in part, by apoE polymorphism, especially when 14:0, 16:0, or 18:0 was consumed.

Adult↗

PubMed1996

Relative effects of high saturated fatty acid levels in meat, dairy products, and tropical oils on serum lipoprotein and low-density lipoprotein degradation by mononuclear cells in healthy males.

To determine the effects of three saturated fatty acid combinations on lipoprotein metabolism, we fed 18 21- to 32-year-old men three diets in a crossover design for 28-day periods separated by washout periods of 4 to 6 weeks. The men self-selected a prescribed diet at home emphasizing saturated fat as the visible fat for 1 week. Then, they ate experimental diets providing 40%, 15%, 17%, and 7% of food energy, respectively, as total, saturated, monounsaturated, and polyunsaturated fatty acids, levels representing amounts available in the US diet. Different test fatty acid combinations, given at 4 to 6 energy% (en%) each, were incorporated into food products: 12:0 + 14:0, 14:0 + 16:0, and 16:0 + 18:0. Test fatty acids were equalized by giving free myristic acid (14:0) with palm kernel oil or butter and sheanut butter (high in 18:0) with lard. The diet highest in 12:0 + 14:0 also provided 4.2 en% 16:0, the most common saturated fatty acid in the US diet. Mean apparent absorption of all fatty acids was at least 90%. The three diets produced similar concentrations of serum total and low-density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B-100 regardless of the apo E phenotype of the subjects. Compared with baseline, the experimental diets affected serum high-density lipoprotein (HDL) concentrations (P < .06), with the highest values occurring on diet 12:0 + 14:0. When the change from baseline in receptor-mediated degradation of 125I-LDL in freshly isolated mononuclear cells (MNC) was stratified by apo E phenotype, diet 16:0 + 18:0 produced a 30% increase, compared with a 9% decrease on diet 12:0 + 14:0 and a 6% increase on diet 14:0 + 16:0 in subjects with the apo E3/3 phenotype. These results suggested that different saturated fatty acid combinations, consumed at levels typical of availability in the United States and with diets providing ample unsaturated fat, had similar cholesterolemic properties in healthy males despite some subtly different effects on lipoprotein metabolism.

Adult↗

PubMed1995

Relative effects on serum lipids and apolipoproteins of a caprenin-rich diet compared with diets rich in palm oil/palm-kernel oil or butter.

Two randomized, blind studies measured changes in serum cholesterol, other serum lipids, and apolipoprotein (apo) concentrations in hypercholesterolemic men consuming caprenin (Cap)-rich diets after either baseline diets enriched in palm oil/palm-kernel oil (PO/PKO) or butter. The triglyceride Cap contains 45% 22:0 and 50% 8:0-10:0. Compared with baseline values established at 3 wk on the PO/PKO diet, the 17 subjects on the Cap diet showed significant reductions after 6 wk in HDL cholesterol (HDL-C), HDL2-C, and HDL3-C and a significant increase in the ratio of total cholesterol, LDL-C, triglycerides, apo B-100, or apo A-I were seen. Compared with baseline values established at 3 wk on the butter diet, after 6 wk the seven subjects receiving the Cap diet showed no significant changes in the lipid and apolipoprotein indexes analyzed. These data show that one or more of 8:0, 10:0, and 22:0 fatty acids can contribute to hypercholesterolemia in men.

Adult↗

PubMed1993

Exercise training and dietary carbohydrate: effects on selected hormones and the thermic effect of feeding.

To determine relationships among dietary carbohydrate, aerobic exercise training, the thermic effect of food (TEF), and hormonal responses to feeding, 8 trained and 7 sedentary men consumed diets providing 15, 45, or 75% of energy as carbohydrate for 5 days. On Day 6, metabolic rate was measured before as well as 30, 60, 90, and 120 min after an 868-kcal liquid test breakfast. Blood was sampled hourly during Day 5 and during each metabolic rate measurement. The trained group had a larger TEF (40 +/- 2.4 vs. 31 +/- 3.0 kcal/2 hrs), greater insulin sensitivity, and greater plasma prolactin and cortisol levels. As carbohydrate in the treatment diet increased, carbohydrate utilization and thyroid stimulating hormone were higher and thyroxine was lower, but TEF was not significantly different. After the test meal, trained individuals had a higher TEF but the carbohydrate content of the treatment diet did not influence TEF.

Adolescent↗

PubMed1991

Serum lipid and apolipoprotein concentrations in healthy men on diets enriched in either canola oil or safflower oil.

This randomized, blind study measured changes in serum lipid and apolipoprotein concentrations in 16 men consuming 39 +/- 1% of energy (en%) as fat either from safflower- or canola-oil-based diets for 8 wk. Initially, the men were stabilized for 3 wk on a typical American (baseline) diet. Compared with baseline, the vegetable-oil-based diets reduced serum total cholesterol 9-15% (P less than 0.002), low-density-lipoprotein (LDL)-cholesterol 12-20% (P less than 0.002), and apolipoprotein B-100 21-24% (P less than 0.001). There were no significant changes from baseline to the end of the study in serum triglycerides, total high-density-lipoprotein (HDL) cholesterol, HDL3 cholesterol, HDL2 cholesterol, or apolipoprotein A-I. These data suggest that even if total fat intake remains at 39-40 en%, many men show lowered LDL cholesterol if saturated fatty acid intake is minimized and that diets high in polyunsaturated fatty acids do not necessarily lower HDL-cholesterol concentrations.

Adult↗

PubMed1991

Effects of diets high in saturated fatty acids, canola oil, or safflower oil on platelet function, thromboxane B2 formation, and fatty acid composition of platelet phospholipids.

Platelet function and fatty acid composition were investigated in 30 healthy male subjects who ate a controlled-saturated-fatty-acid (baseline) diet for 3 wk and then consumed either safflower oil or canola oil as a major fat source for 8 wk. Fatty acid composition of platelet phospholipids reflected changes in dietary fatty acid composition. Compared with baseline a 35% decrease (P less than 0.05) in arachidonic acid was observed in platelet phospholipids of the canola-oil diet group while long chain n-3 fatty acids rose 7-26% (P greater than 0.05). Compared with baseline both unsaturated-fatty-acid diets reduced platelet aggregation at 3 wk of oil-based diet feeding (P less than 0.01) whereas only canola oil influenced platelet function (lowered ATP secretion) at 8 wk (P less than 0.01). No significant difference was observed in thromboxane B2 concentrations between oil-treatment groups at 8 wk. Both oil-based diets had short-term beneficial effects on platelet function but the effect of canola oil persisted longer.

Adenosine Triphosphate↗

PubMed1990

Effect of diets high in butter, corn oil, or high-oleic acid sunflower oil on serum lipids and apolipoproteins in men.

This randomized blind crossover study compared serum lipid and apolipoprotein concentrations in 20 men consuming 37-43% of energy as fat from diets based on corn oil, high-oleic acid sunflower oil, and butter. Each phase of the crossover design included 2 wk of butter-based diet followed by 5 wk of designated vegetable-oil-based diet with a 7-wk washout period between phases. Compared with values for the butter-based diet, the vegetable-oil-based diets reduced serum total cholesterol by 16-21% (p less than 0.001), LDL cholesterol by 21-26% (p less than 0.001), triglycerides by 10-21% (p less than 0.01 for the higher figure), and apolipoprotein B-100 by 22-29% (p less than 0.001). When values fell, they fell further on the corn-oil-based diet. There were no significant changes in serum HDL cholesterol or apolipoprotein A-1. These data suggest that when men on diets high in saturated fatty acids reduce their saturated fatty acid intake but not their total fat intake, many can still experience a significant lowering in serum total cholesterol.

Adult↗

PubMed1990

Effects of fish oil on serum lipids in men during a controlled feeding trial.

Effects of fish-oil (FO) feeding on serum lipids were investigated in a 42-d controlled diet study. Fifteen healthy male college students were assigned to one of three groups: control (0 g FO); 5 g FO, supplying 2 g n - 3 (omega-3) fatty acids (FAs); or 20 g FO, supplying 8 g n - 3 FAs. In an initial 7-d period subjects consumed a basal diet with no FO. Then FO replaced an equivalent amount of margarine for 5 wk. FO feeding significantly (p less than 0.05) decreased the serum n - 6 FAs, linoleic acid, eicosatrienoic acid, and arachidonic acid. A significant increase in the n - 3 FAs, eicosapentaenoic acid and docosahexaenoic acid, was noted in serum, platelet, and neutrophil phospholipids. The 20-g-FO group showed a 30% decrease (p less than 0.01) in triglycerides after 2 wk FO with no further decrease observed. Thus, 20 g FO produced changes in both FA patterns and triglyceride concentrations whereas 5 g FO produced changes in FA patterns only. Neither FO amount resulted in significant changes in total or HDL cholesterol, apolipoprotein A-I, or apolipoprotein B-100.

Adult↗

PubMed1990

Dietary carbohydrate and intensity of interval swim training.

We tested the effects of 9 d of a high-carbohydrate diet (80% of calories as CHO, 80% CHO diet) vs. a moderate-CHO diet (43% of calories as CHO, 43% CHO diet) on the abilities of collegiate swimmers to maintain a high intensity of interval swim training. Interval swim times and other physiological indices were recorded the last 5 d of each diet. Swim-interval distances ranged from 50-m interval sets to continuous 3000-m swims. There were no diet effects on mean swim velocities for any interval distance, and mean (+/- SEM) velocities for all swims were identical for both diets. There were no diet effects on the physiological indices; however, postswim blood lactate concentrations were higher after the 80% CHO diet. When mean +/- SEM daily caloric intake is 19.56 +/- 2.16 MJ (4675 +/- 516 kcal) for swimmers undertaking swim training to develop aerobic capacity, an 80% CHO diet provides no advantage over a 43% CHO diet for maintaining interval-swim-training intensity.

Adult↗

PubMed1989

Serum and urinary markers of skeletal muscle tissue damage after weight lifting exercise.

The purpose of this study was to determine whether high intensity weight lifting exercise produces elevations of urinary 3-methylhistidine (3-MH), serum creatine kinase activity (CK), and serum myoglobin concentration (MY), and whether trained weight lifters differed in such responses when compared to a group of untrained subjects. Ten experienced male weight lifters (EWL) and seven untrained male subjects (IWL) performed three sets of six weight lifting exercises at 70%-80% of 1 RM. All subjects consumed a meat-free diet. The 3-MH:creatinine (3-MH:CR) values decreased 24 h and 48 h following exercise (P less than 0.05). The 12-h and 24-h postexercise CK response and the 12-h postexercise MY response increased for both EWL and IWL (P less than 0.05). However, EWL had a lower 24-h postexercise CK response and lower 12-h and 24-h postexercise MY responses compared to IWL (P less than 0.05). Within 48 h following weight lifting exercise, skeletal muscle protein degradation (as assessed by 3-MH:CR values) decreased regardless of prior training experience whereas skeletal muscle tissue damage (as assessed by CK and MY responses) increased. However, prior weight lifting training appeared to diminish the extent of muscle tissue damage.

Adult↗

PubMed1987

Effect of a high-protein, very-low-calorie diet on body composition and anthropometric parameters of obese middle-aged women.

Effects of a very-low-calorie (420 kcal/day), high-protein diet (70 g/day) and realimentation on weight and body composition of 15 obese, middle-aged women were examined in a 4-6 mo study. Mean weight loss was 20.5 kg (1.1 kg/wk). Fat accounted for 83% and lean body mass (LBM) for 17% of total body weight loss. Multiple regression equations estimated from anthropometric measures were developed to predict the body density of obese individuals both before and after weight loss. Best predictors of body density in obese women before and after weight loss were circumference measurements in the trunk area. Nine previously published population specific and generalized equations for predicting body fat in women were not strongly enough correlated with body fat values obtained by densitometry in this study to be of use clinically.

Adipose Tissue↗