1,721,336 research outputs found
Regulation of dietary fatty acid entrapment in subcutaneous adipose tissue and skeletal muscle
No full textUsing stable isotopic labeling of dietary fatty acids in conjunction with arteriovenous difference measurements, we have assessed the regulation of lipoprotein lipase-derived fatty acid entrapment in subcutaneous adipose tissue and forearm muscle in healthy subjects in the postprandial state. Eight volunteers fasted overnight and were then given a mixed meal containing [ 1-13C]palmitic acid and [1-13C]oleic acid. At baseline and for 6 h after the meal, blood samples were obtained from an arterialized hand vein and veins draining subcutaneous abdominal adipose tissue and forearm muscle, and arteriovenous differences were calculated. Entrapment of labeled fatty acids released by circulating triacylglycerol hydrolysis was close to 100% at 60 min, decreasing to 10–30% by 360 min. Entrapment of labeled fatty acids in forearm muscle was >100% and did not change with time. This study shows that entrapment of dietary fatty acids in adipose tissue in the postprandial period is a highly regulated process (varying with time) and that this can be studied in humans using stable isotope- labeled fatty acids in combination with measurement of appropriate arteriovenous differences. Also, fatty acid trapping in skeletal muscle is fundamentally different from that in adipose tissue, in that all the fatty acids released by lipoprotein lipase in skeletal muscle are taken up by the tissue
Selective partitioning of dietary fatty acids into the VLDL TG pool in the early postprandial period
No full textCirculating triacylglycerol (TG) arises mainly from dietary fat. However, little is known about the entry of dietary fat into the major TG pool, very low-density lipoprotein (VLDL) TG. We used a novel method to study the specific incorporation of dietary fatty acids into postprandial VLDL TG in humans. Eight healthy volunteers (age 25.4 ± 2.2 years, body mass index 22.1 ± 2.3 kg/m2) were fed a mixed meal containing 30 g fish oil and 600 mg [1-13C]palmitic acid. Chylomicrons and VLDL were separated using immunoaffinity against apolipoprotein B-100. The fatty acid composition of lipoproteins was analyzed by gas chromatography/mass spectrometry. [1-13C]palmitic acid started to appear in VLDL TG 3 h after meal intake, and a similar delay was observed for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Approximately 20% of dietary fatty acids entered the VLDL TG pool 6 h after meal intake. DHA was clearly overincorporated into this pool compared with [1-13C]palmitic acid and EPA. This seemed to depend on a marked elevation of this fatty acid in the nonesterified fatty acid pool. In summary, the contribution of dietary fatty acids to early postprandial VLDL TG is substantial. The role of DHA in VLDL TG production will require further investigation. <br/
Dietary fatty acids make a rapid and substantial contribution to VLDL-triacylglycerol in the fed state
No full textExaggerated postprandial lipemia is associated with coronary heart disease and type II diabetes, yet few studies have examined the effect of sequential meals on lipoprotein metabolism. We have used 13C-labeled fatty acids to trace the incorporation of fatty acid derived from a meal into apolipoprotein B-100 (apoB-100)-containing lipoproteins and plasma nonesterified fatty acids (NEFA) following two consecutive meals. Healthy volunteers (n=8) were given breakfast labeled with [1-(13)C]palmitic acid, eicosapentaenoic acid, and docosahexaenoic acid, followed 5 h later by lunch containing [1-(13)C]oleic acid. Blood samples were taken over a 9-h period. ApoB-100-containing lipoproteins were isolated by immunoaffinity chromatography. Chylomicron-triacylglycerol (TG) concentrations peaked at 195 min following breakfast but at 75 min following lunch (P<0.001). VLDL-TG concentrations, in contrast, rose to a broad peak after breakfast and then fell steadily after lunch. Breakfast markers followed chylomicron-TG concentrations and appeared in plasma NEFA with a similar profile, whereas [1-(13)C]oleic acid peaked 2 h after lunch in plasma TG and NEFA. Breakfast markers appeared steadily in VLDL, peaking 1-3 h after lunch, whereas [1-(13)C]oleic acid was still accumulating in VLDL at 9 h. Around 17% of VLDL-TG originated from recent dietary fat 5 h after breakfast, and around 40% at the end of the experiment. We conclude that there is rapid flux of fatty acids from the diet into endogenous pools. Further study of these processes may open up new targets for intervention to reduce VLDL-TG concentrations and postprandial lipemi
Effects of prior moderate exercise on exogenous and endogenous lipid metabolism and plasma factor VII activity
No full textModerate exercise reduces postprandial triacylglycerol concentrations, which are a risk marker for coronary heart disease. The present study sought to determine the qualitative nature of exercise-induced changes in lipid metabolism and their association (if any) with changes in factor VII activation. Eleven normotriglyceridaemic men, aged 51.7±6.1 years (mean±S.D.), participated in two oral fat tolerance tests after different pre-conditions: control (no exercise), and exercise (90 min of brisk walking the day before). Venous blood samples were obtained in the fasted state and for 8 h after ingestion of a high-fat meal (1.32 g of fat, 1.36 g of carbohydrate, 0.30 g of protein and 10 mg of [1,1,1-13C] tripalmitin·kg-1 body mass). Prior exercise reduced postprandial plasma triacylglycerol concentrations by 25±3% (mean±S.E.M.), with lower concentrations in the Svedberg flotation rate (Sf) 20–400 (very-low-density lipoprotein) fraction accounting for 79±10% of this reduction. There was no effect on plasma factor VII coagulant activity or on the concentration of the active form of factor VIIa. Prior exercise increased postprandial serum 3-hydroxybutyrate and plasma fatty acid concentrations, decreased serum postprandial insulin concentrations and increased exogenous (8 h 13C breath excretion of 15.1±0.9% of ingested dose compared with 11.9±0.8%; P = 0.00001) and endogenous postprandial fat oxidation. These data raise the possibility that reduced hepatic secretion of very-low-density lipoprotein plays a role in the attenuation of plasma triacylglycerol concentrations seen after exercise, although it is possible that increased triacylglycerol clearance also contributes to this effect.<br/
Adrenergic regulation of regional fat metabolism
Get PDFIntroduction: An increased gluteofemoral adipose tissue (AT) mass is associated with a protective cardiovascular and metabolic risk profile, and effective fatty acid retention in femoral AT has been proposed as a possible mechanism. Catecholamines are important regulators of AT lipolysis and blood flow (ATBF). The aim of the thesis was to investigate regional differences in the adrenergic regulation of fatty acid release and ATBF between abdominal and femoral AT in vivo. Furthermore, in vivo regional fatty acid trafficking was studied in a physiological setting over 24 h.Methods: Regional fatty acid trafficking, along with the measurement of ATBF, was studied with the arterio-venous difference technique and stable isotope tracers in healthy volunteers. Adrenergic agonists (isoprenaline, adrenaline) were infused either locally by microinfusion, or systemically. Local microinfusion of adrenoreceptor antagonists (propranolol, phentolamine) was used to characterize specific adrenoreceptor subtype effects. The trafficking of dietary fatty acids was studied over a 24 h period involving three meals containing stable isotope-labelled fatty acids along with intravenous infusions of another labelled fatty acid.Results: Femoral ATBF and lipolysis was less responsive to adrenergic stimulation with adrenaline compared to abdominal AT. This was due to increased femoral α-adrenoreceptor responsiveness. When studied over 24 h, femoral AT showed a lower lipolysis rate compared to abdominal AT, while dietary fatty acids were extracted more avidly by abdominal AT. Uptake of non-dietary fatty acids (derived from very-low-density lipoproteins or unbound non-esterified fatty acids) was comparable between abdominal and femoral AT.Conclusion: There are fundamental differences in response to adrenergic stimuli between abdominal and gluteofemoral tissues and the ability of femoral AT to trap non-dietary fatty acids may provide protection of other tissues from ectopic fatty acid deposition
Fat metabolism and the metabolic syndrome
Get PDFBackground: The metabolic syndrome is associated with an increased risk of diabetes and vascular disease. In order to understand the pathophysiological processes underlying such risk, it is necessary to develop a better understanding of normal fat metabolism and abnormalities associated with the syndrome. The hypothesis tested in this thesis is that specific abnormalities in adipose tissue and muscle fat metabolism characterise the metabolic syndrome. Methods: Fasting biochemical parameters were measured in a cohort of overweight men with and without the metabolic syndrome. Stable-isotope labeling and arterio-venous difference measurements were conducted in 18 men to elucidate pathways of exogenous and endogenous fat metabolism under fasting and postprandial conditions in adipose tissue and skeletal muscle. In addition, a pilot study of the effects of heat and electrical stimulation on adipose tissue metabolism was undertaken. Results: Cohort study - The prevalence of the metabolic syndrome depended on the definition used. Total cholesterol and apoB were greater in those with the metabolic syndrome than in those without. There was no difference in fasting NEFAs. Metabolic investigation - There was significant postprandial uptake of NEFA from the circulating NEFA pool by adipose tissue. Chylomicrons were confirmed as the preferred substrate of LPL. There was preferential uptake of FAs derived from chylomicron hydrolysis. There was release of NEFA across muscle. In the metabolic syndrome, adipose tissue NEFA output is lower during fasting and falls less following a meal than in the healthy obese. Clearance of dietary-derived TG is lower across both adipose tissue and muscle in the metabolic syndrome. Pilot study – Heat increased measures of lipolysis whereas electrical stimulation had no effect. Conclusions: Fat metabolism in individuals with the metabolic syndrome is characterised by metabolic inflexibility but not insulin resistance
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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