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Biomedical subjects

G Wolfram

Publications and source records attributed to G Wolfram.

At least 145 records · Page 8Linked to original sources
PubMed1987

Inhibition of muscular amino acid release by lipid infusion in man.

Amino acid balances of healthy postabsorptive volunteers were investigated with the forearm technique under the influence of an intravenous infusion of triglyceride emulsions (LCT; MCT/LCT) [corrected]. A decrease of the basal muscular release of most of the amino acids, respectively an increase of pre-existent uptake rates [corrected]. In parallel, arterial concentrations of these amino acids declined. With constant insulin levels and substantially unchanged blood glucose levels, this inhibition of muscular proteolysis and/or stimulation of proteosynthesis is most probably due to the increased level of free fatty acids.

Amino Acids↗
PubMed1987

[Thermogenesis in humans after varying meal time frequency].

To a group of 8 healthy persons a slightly hypocaloric diet with protein (13% of energy), carbohydrates (46% of energy) and fat (41% of energy) was given as one meal or as five meals in a change-over trial. Each person was 2 weeks on each regimen. Under the conditions of slight undernutrition and neutral temperature the balances of nitrogen, carbon and energy were assessed in 7-day collection periods, and according to 48-hour measurements of gaseous exchange (carbon-nitrogen balance method) by the procedures of indirect calorimetry. Changes of body weight were statistically not significant. At isocaloric supply of metabolizable energy with exactly the same foods in different meal frequencies no differences were found in the retention of carbon and energy. Urinary nitrogen excretion was slightly greater with a single daily meal, indicating influences on protein metabolism. The protein-derived energy was compensated by a decrease in the fat oxidation. The heat production calculated by indirect calorimetry was not significantly different with either meal frequency. Water, sodium and potassium balances were not different. The plasma concentrations of cholesterol and uric acid were not influenced by meal frequency, glucose and triglycerides showed typical behaviour depending on the time interval to the last meal. The results demonstrate that the meal frequency did not influence the energy balance.

Body Water↗
PubMed1987

[Essential fatty acids in parenteral nutrition].

Fat is a very important nutrient in that it supplies energy, essential fatty acids and fat soluble vitamins. The importance of n-6 essential fatty acids, i.e., linoleic and arachidonic acid, in total parenteral nutrition was demonstrated in the last 15 years by several cases of essential fatty acid deficiency. In addition, n-3 fatty acids, i.e., alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid, are essential nutrients in forming an independent family of eicosanoids with biological effects different from those of the n-6 fatty acids. The requirement of different essential fatty acids in patients with total parenteral nutrition after heavy injury is of special interest with respect to the development and prognosis of shock, sepsis or adult respiratory distress syndrome. The available soy oil based fat emulsions contain n-6 and n-3 fatty acids in a suitable proportion of 7:1, but further information on essential fatty acid requirement in different diseases is necessary.

Fat Emulsions, Intravenous↗
PubMed1987

[Clinical studies with fat emulsions containing LCT and MCT].

In an effort to supply energy carriers with a high utilization rate specifically in parenteral nutrition during postaggression metabolism, fat emulsions were developed containing long- and medium-chained triglycerides in a 1:1 ratio. The special advantage of the medium-chained fatty acids is, among other things, their low rate of accumulation and high oxidation rate in the organism. Using a graduated schedule, intensive-care patients who were being parenterally fed exclusively were administered either an MCT/LCT mixture or an LCT emulsion alone as a bolus injection and later continuously. Among other things, the behavior of the triglyceride concentrate and the individual fatty acids in serum and of individual lipid fractions, as well as the effect on various parameters of carbohydrate and fat metabolism, were measured. In addition, the oxidation rate of an MCT/LCT emulsion labelled with 13C was measured. The results of the comparative lipid studies were compared. The expected result-that the oxidation rate of medium-chained triglycerides exceeds that of long-chained triglycerides-was confirmed. It was surprising that the median oxidation rate with a continuous fat supply within a complete nutrition program was only 32 +/- 6.8%. Why some patients showed higher triglyceride levels with the MCT/LCT emulsion than with the supply of LCT alone is still unclear. It remains to be investigated whether the rapid splitting of medium-chained triglycerides leads to a temporary loss of activity of the lipoprotein lipase accompanied by a rise in triglycerides in serum. More research will be necessary before we know what role MCT/LCT emulsions will play in future. Such an emulsion would possibly be suitable in severely injured patients, whereby the MCT portion could preferentially supply the organism with energy carriers and the long-chained triglycerides structural components.

Critical Care↗
PubMed1986

[Comparison of the effect of linolenic acid and eicosapentaenoic acid on prostaglandin biosynthesis and thrombocyte function in humans].

Platelet aggregation, bleeding time, prostaglandin biosynthesis and plasma cholesterol fatty acids were investigated in 12 healthy females (25-32 years), who were given different amounts of linolenic acid (0%, 4%, 8%, 12%, 16% of total energy intake) or eicosapentaenoic acid (1.7%) with formula diets for 2 weeks each. Linolenic and eicosapentaenoic acids prolonged the bleeding time and inhibited platelet aggregation and prostaglandin biosynthesis. These effects became apparent after a linolenic acid intake of 12% of the energy intake. A decrease in PGE in 24 h urine was observed after intake of linolenic acid amounting to 8% of energy intake. Eicosapentaenoic acid influenced all parameters measured ten times more than linolenic acid. Linolenic acid intake had no effect on the ratio of linoleic/arachidonic acids in plasma cholesterol esters in contrast to in vitro findings. Thus energy intake comprising 1.7% of eicosapentaenoic acid is sufficient to affect thrombocyte function in man. The concomitant intake of linolenic-type fatty acids inhibits the biosynthesis of prostaglandins E2 and F2 alpha to different degrees.

Adult↗
PubMed1986

Effect of acarbose on carbohydrate tolerance during administration of a fibre-free formula diet on healthy subjects.

The influence of the disaccharidase inhibitor acarbose on carbohydrate tolerance was investigated in healthy subjects during substitution of fibre-free formula diets for normal food. Two separate experiments showed that acarbose was highly efficient in retarding and diminishing the postprandial rise in blood glucose and serum insulin when administered with these diets for 10 to 14 days. Acarbose decreased the area under the postprandial curves of blood glucose from 1.836 to -504 mg/dl X min in Study 1, and from 587 to -302 mg/dl X min in Study 2. The area under the serum insulin curves was reduced from 5.022 to 1.440 microU/ml X min in Study 1, and from 7.990 to 918 microU/ml X min in Study 2. In addition, acarbose greatly diminished the interindividual variation in postprandial serum insulin concentration. Its efficacy in reducing the glycaemic response to a test meal in both experiments was found to depend on the time of initiation of therapy; in contrast, the serum insulin response was only time-dependent in Study 2. Use of fibre-free diets to standardise experimental conditions proved to be a valuable tool in investigating these details.

Acarbose↗
PubMed1986

Inhibition of muscular glucose uptake by lipid infusion in man.

During a high-dose intravenous infusion of a mixed MCT/LCT-lipid emulsion and a conventional LCT-emulsion respectively, muscle substrate metabolism was investigated using the human forearm technique. With both lipid emulsions, a decrease in fractional muscular glucose extraction was seen, leading to significantly reduced muscular glucose uptake rates. An inverse linear relation between arterial tree fatty acids supply and fractional glucose extraction was seen suggesting that a mechanism according to Randle's glucose fatty acid concept is operating in skeletal muscle in man.

Journal Article↗
PubMed1986

Influence of artificial fat emulsions on the composition of serum lipoproteins in humans.

Infusions of about 50 g soya oil, emulsified with egg lecithin (Intralipid) or soya lecithin (Lipofundin) have different effects on the composition of serum lipoprotein fractions in volunteers (n = 6). Triglycerides are altered in all lipoprotein fractions most in lowest density classes but also in LDL and HDL. Differences in maximal concentrations (higher during Intralipid) and differences in removal rate of triglycerides (faster with Lipofundin) are due to different emulsifiers. Cholesterol increase in VLDL and decrease in HDL3 are independent from emulsifier. Intralipid produces an increase of phospholipids in all lipoprotein fractions, Lipofundin only in VLDL. Linoleic acid in lecithin fatty acids of lipoprotein fractions is increased by Lipofundin and decreased by Intralipid. Apolipoprotein A-I and A-II decrease in HDL3 and slightly increase in HDL2. During both infusions apolipoprotein C-II increases significantly after Intralipid.

Adult↗
PubMed1986

Regulation of lipogenesis in mitogen-stimulated human lymphocytes by thyroid hormones.

The hormonal regulation of precursor incorporation into cellular lipids has been investigated in human lymphocytes stimulated with phytohemeagglutinine. Addition of thyroxine (5 micrograms/ml) for 72 h increased incorporation of [14C]acetate into the triacylglycerol fraction to 290% above the hormone-free control values. Incorporation into the cholesterol fraction was elevated up to 188% under the same conditions. Triiodothyronine was less effective than thyroxine: maximal effects were 153% of the control for triacylglycerols and 142% for cholesterol. Similar results were obtained when [14C]palmitic acid was used as a precursor for triacylglycerol synthesis. Effects of insulin on the parameters described were less pronounced than those obtained with thyroid hormones. Cellular triacylglycerol and protein contents were not elevated significantly by thyroid hormone addition. Further, incorporation of labelled thymidine, uridine, and leucine into acid-precipitable products was not elevated by triiodothyronine above mitogen-stimulated levels. It is concluded, that rapidly dividing lymphocytes provide a suitable system for studies concerning human lipid metabolism.

Acetates↗
PubMed1986

Effect of alpha-linolenic acid in the human diet on linoleic acid metabolism and prostaglandin biosynthesis.

The effect of dietary alpha-linolenic acid intake on linoleic acid metabolism and prostaglandin (PG) biosynthesis was investigated in two groups of six healthy females (25-32 yr). They were given isocaloric formula diets (FD) containing linoleic acid at a constant intake (4% of calories), with different amounts of alpha-linolenic acid: 0% (FD4/0), 4% (FD4/4), 8% (FD4/8) (group I) and 12% (FD4/12) or 16% (FD4/16) (group II); the diets were given for 2 weeks each. Comparing diet FD4/0 to FD4/16, enrichment of alpha-linolenic acid was greatest in cholesteryl esters (+6.8% in plasma, +7.1% in low density lipoproteins (LDL), +5.9% in high density lipoproteins (HDL)), less in phosphatidylcholine (+2.5% in plasma, +2.9% in LDL, +2.7% in HDL), and least in platelet lipids (+0.7%). The accumulation of alpha-linolenic acid was compensated by a decrease of oleic acid. Eicosapentaenoic acid (EPA), which was excluded from the diet, increased in all plasma lipids with augmented alpha-linolenic acid intake, indicating a chain elongation and desaturation of alpha-linolenic acid to EPA. However, even at the end of FD4/16, EPA was less than 2% of total fatty acids in all plasma lipids. Plasma linoleic acid levels were constant during all dietary regimes, according to the constant dietary intake of this fatty acid. No replacement of linoleic acid by alpha-linolenic acid could be observed. The percentage of arachidonic acid in all lipids was unaffected by alpha-linolenic acid intake. As arachidonic acid was not provided by the diet, it can be concluded that alpha-linolenic acid does not inhibit chain elongation and desaturation of linoleic acid to arachidonic acid in man.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Prostaglandin formation and platelet aggregation during fasting and linoleic acid intake.

Prostaglandin formation, estimated by the determination of tetranorprostanedioic acid (TNPDA) in the urine, and platelet aggregation were investigated in seven healthy volunteers each day during fasting, and in three of them additionally during intake of carbohydrates (328kcal/day) or safflor oil (328 kcal, 20 g linoleic acid). Monitoring TNPDA in 8-h fractions of the urine showed a reduction during the night (23.00-07.00) by 70% on the average. During Days 1 and 2 of fasting the amount of TNPDA in 24-h urine was the same as under a conventional diet. On Day 3, TNPDA decreased in all experimental subjects to 162 micrograms/day on the average and was not changed by carbohydrate intake. A linoleic acid intake of 20 g/day increased TNPDA in 24-h urine to pre-experimental levels measured under free diet. Platelet aggregation did not change during the experiment. No relationship between prostaglandin formation and lipolysis in man was found.

Adult↗
PubMed1985

[The effect of linoleic acid intake on its concentration and resultant products in individual plasma lipids in humans].

Dietary linoleic acid enrichment in different plasma lipids was investigated in six healthy females. They were given formula diets (FD) containing no arachidonic acid, and providing a linoleic acid supply of 0% (FD0), 4% (FD4) or 20% (FD20) of total energy intake. At the end of each two weeks FD period fatty acid distribution was determined in cholesterol esters (CE) and in lecithin of LDL and HDL. The increase of linoleic acid in CE was twice that found in the lecithin of LDL and HDL. Comparing FD0 and FD20 the increase of linoleic acid in CE of LDL and HDL was 34%, and in lecithin 15%. Simultaneously oleic acid was lowered in CE (-17%) and in lecithin (-8%) of LDL and HDL. Comparing FD0 and FD20 arachidonic acid, which derives from linoleic acid, was lowered with increased linoleic acid intake in LDL-CE (-5%) and in HDL-lecithin (-8%), while no effect was found in LDL-lecithin. Our results demonstrate that dietary linoleic acid enrichment occurs preferentially in CE of LDL and HDL, but does not lead to an increase of arachidonic acid in plasma lipids. However, a decrease was found for arachidonic acid in HDL-lecithin, while in LDL-lecithin no effect could be observed. From this it is concluded that incorporation and metabolism of linoleic acid in different plasma lipids is not identical, although lipid exchange and lipid transfer have been shown for most lipoprotein fractions.

Adult↗
PubMed1985

Effect of plasma exchange with and without concomitant drug treatment on lipids and lipoproteins in patients with familial hypercholesterolemia confirmed by tissue culture.

Repeated plasma exchange is an effective treatment for young patients with familial hypercholesterolemia. We treated 2 homozygous and 1 heterozygous patient with very high cholesterol levels with continuous plasma exchange using human albumin solution as exchange medium. The treatment was repeated every 2 weeks in 2 patients and weekly in the third. Treatment periods of plasma exchange alone and of plasma exchange with concomitant drug therapy were compared. For drug treatment beta-pyridylcarbinol, the alcohol corresponding to nicotinic acid (0.9 g/day equivalent to 3 g of nicotinic acid) and cholestyramine (16 g/day) were used. Plasma exchange alone resulted in a decrease of all lipids by 55% and of apolipoproteins by 50-60% as compared to the plasma levels before exchange. Subsequently all lipoproteins rose again to reach pre-exchange levels within about 2 weeks. There was no difference between the homozygous and the heterozygous patients. Beta-pyridylcarbinol or cholestyramine given concomitantly did not alter the post-exchange increase of total, LDL, HDL cholesterol nor of the corresponding apolipoproteins except of apolipoprotein B.

Adult↗
PubMed1985

[Energy balance trials with a diet rich in fats in the human].

The effects of two diets equal in protein content (12% of energy) but different in carbohydrates (80% of energy) or in fat (68% of energy) were studied in a changeover trial with 6 healthy young subjects. Each person was 2 weeks on each diet. Under the conditions of slight undernutrition and neutral temperature the balances of nitrogen, carbon and energy were assessed in 7-day collection periods, and according to 48-hour measurements of gaseous exchange (carbon-nitrogen balance method) by the procedures of indirect calorimetry. At isocaloric supply of metabolizable energy no differences were found in the retention of N, C and energy. The heat production calculated by indirect calorimetry was not significantly different with both diets. The lower body weight during the high-fat diet was due to higher sodium and water excretion. The high-fat diet resulted in lower fecal and higher urine excretion of nitrogen, but because of a compensative response no difference in nitrogen retention was observed between the two dietary regimens. The plasma concentrations of cholesterol, glucose and uric acid were higher with fat-rich diet; those of triglycerides were higher with carbohydrate-rich diet. The results demonstrate that the composition of the diet did not influence the energy balance.

Adult↗