Walter Mlekusch

The effect of hunger on free fatty acid and corticosterone plasma levels in rats.

The time function of free fatty acids and of corticosterone in plasma in fed and fasted rats was investigated. Also a study of the influence of hypoxia on the concentration of plasma free fatty acids was carried out. Whereas fasting does not seem to stimulate lipolysis markedly before 12 h, 2 h of hypoxia elevate the free fatty acid level to its maximum. In the fasted condition, all values are significantly higher than corticosterone in the fed animal.

A glucose-rich diet shortens longevity of mice

High plasma levels of glucose and insulin over long-time periods play an important role in the genesis of diabetic complications. There is evidence that the long term consumption of glucose-rich diet by rats is detrimental to insulin sensitivity. We investigated the effect of a glucose-rich diet on longevity of 70 female mice which were compared to 70 mice on a control diet. The average age of death of the control group was 568 +/- 139 days compared to 511 +/- 170 for the glucose group and the seven oldest mice of the control group died at age 890 +/- 52 days, while the seven oldest mice of the glucose group died at 833 +/- 49 days. These differences are statistically significant (P < or = 0.05). Our work shows that a life-long intake of a diet with 20% of total energy derived from glucose leads to a significant reduction of the average and maximal life-span in female mice and thus, supports previous observations of detrimental effects of high glucose intake over long periods.

The effect of reduced physical activity on longevity of mice

Reduced physical activity leads, in female mice, to a reduction of the average and maximal life span. The average age at death of the inactive experimental group was 497 +/- 121 days (mean +/- S.D.) compared to 557 +/- 139 days in the active control group, and the six oldest inactive experimental mice died at age 732 +/- 50 days, while the six oldest active control mice died at 890 +/- 52 days. The restriction of mobility was connected with a higher growth rate and a higher body weight in spite of a significant decrease in food intake. In spite of a reduced food intake leading to a reduced whole body metabolism, the results show that mobility restriction shortens life span in female mice.

Effect of a high fat diet on phospholipid class distribution and fatty acid composition in rat liver

1. Long term consumption (20 weeks) of a high fat diet (65% of the energy content as fat) rich in either saturated [30% (w/w) coconut oil] or unsaturated [30% (w/w) sunflower oil] fatty acids resulted in strikingly similar alterations in the phospholipid class distribution and fatty acid composition in the liver of male Wistar rats. 2. The effect of these two diets was compared to a control group maintained on a 2% fat diet (w/w) for the same time interval. 3. In spite of the difference in the PUFA/SFA (polyunsaturated fatty acid/saturated fatty acid) ratio between the two high fat diets (0.1, saturated fatty acid diet; 5.4, unsaturated fatty acid diet), both diets resulted in a similar PUFA/SFA ratio in liver phospholipids, a similar reduction in palmitic acid (16:0), oleic acid (18:1, n-9) and arachidonic acid (20:4, n-6) and an elevation in stearic acid (18:0), linoleic acid (18:2, n-6) and docosahexaenoic acid (22:6, n-3). 4. Further, changes in the phospholipid classes were also similarly affected by both high fat diets.

Effect of a high fat diet on plasma lipids, lipoprotein lipase, lecithin:cholesterol acyltransferase, and insulin function in adult rabbits

Abstract The influence of a high fat diet (19% wt./wt.) vs. a standard, chow diet (2% fat) on plasma lipids, lipoprotein lipase (LPL), lecithin:cholesterol acyltransferase (LCAT), glucose, and glucose tolerance, was investigated. Both diets had a similar fatty acid pattern and a polyunsaturated:saturated (P:S) fatty acid ratio of 2.7. The high fat diet elevated plasma triglycerides, phospholipids, and cholesterol concentrations and changed the percent distribution of cholesterol and phospholipids among the lipoprotein fractions. Additionally, LCAT and plasma glucose increased, while lipoprotein lipase and its products, free fatty acids and glycerol, were not altered. Glucose tolerance was significantly inhibited in animals on the high fat diet, which also exhibited a diminished insulin secretion. As such, the high fat diet seemed to evoke a diabetogenic situation. The return to the standard chow diet appeared to normalize, to a great extent, the alterations evoked by the high fat diet.

Direkte fluorimetrische bestimmung von serumlipiden auf dünnschichtchromatogrammen

Abstract A simple and rapid method for the direct quantitative analysis of thin-layer chromatograms of serum lipids is described. Estimation of phospholipids, triglycerides, cholesterolester and free cholesterol is achieved by thin-layer chromatography using a new fluorimetric technique.

Effect of skim milk and whey diets on plasma lipid levels of rabbits in a cross-over study

The influence of a skim milk and a whey-based diet on plasma lipids and lipoproteins in rabbits was investigated in a crossover design, in which the diets were switched after 12 weeks. The whey diet increased plasma lipid levels regardless of when it was consumed in the feeding protocol. The milk diet, on the other hand, modestly elevated the lipid levels if provided in the first half of the feeding protocol, but reduced lipid levels if given in the second half of the feeding regime. Both diets also induced similar changes in lipoprotein patterns when given in the first half of the feeding protocol, but opposite effects during the second half. Atherosclerotic changes were also observed in the aorta of animals receiving the whey diet during the second half of the experimental protocol.

The life-shortening effect of reduced physical activity is abolished by a fat rich diet.

In female mice on a control diet (3.6% fat) reduced physical activity leads to a reduction of the average life span. So the average age at death of an inactive group is 500 +/- 166 compared to 565 +/- 175 days in an active control group. If the animals are kept on a fat rich diet (12.4% fat) this effect of physical activity restriction is no longer observable and the average age at death is 570 +/- 142 days, within the range of the control animals. The increased fat intake seems to reduce the stress or to increase the resistance to stress in the activity restricted animals. So stress is a crucial determinant of life span.

Zur anwendung der Sulfophosphovanillinreaktion auf dünnschichtchromatographisch getrennte lipide

Abstract Application of the sulpho-phospho-vanillin reaction to the determination of lipids separated by thin-layer chromatography The “sulpho-phosphoro-vanillin” reaction has shown to be a simple and rapid routine method for quantitative determination of neutral lipids on thin-layer chromatograms. The technique also works well after visualization of the lipids by heating with sulphuric acid under UV light.

The conformational flexibility of 5,6,7,8-tetrahydrobiopterin and 5,6,7,8-tetrahydroneopterin: a molecular dynamical simulation.

5,6,7,8‐Tetrahydrobiopterin is an essential cofactor of diverse enzymes. Of the eight possible stereoisomers, only the 6R,1′R,2′S‐configuration is biologically active. Other stereoisomers, as well as other reduced pterins such as, e.g. 5,6,7,8‐tetrahydroneopterin, fail to exhibit significant cofactor activity. Different theoretical models (molecular mechanics, semi‐empirical quantum chemical calculations) investigating the stereostructure of tetrahydrobiopterin have yielded diverging answers. It has been claimed on the basis of semi‐empirical quantum chemical calculations that conformational properties, and thus particular features in overall shape, might be responsible for the unique biological properties of natural tetrahydrobiopterin in contrast, e.g. to 6R,1′S,2′R‐5,6,7,8‐tetrahydroneopterin. Molecular dynamical simulations of both molecules at realistic temperatures demonstrate, however, that they possess sufficient conformational flexibility as to render questionable any biological significance of mere conformational properties.