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Summary The effects of feeding 75 versus 750 IU vitamin A/kg body mass (BM) per day to eight healthy pony geldings were studied in a cross-over design experiment for 20 weeks. The vitamin E intake was 2 mg/kg BM per day. α-tocopherol and retinoid distribution was examined in serum and lipoproteins. No effect was seen on retinol, α-tocopherol, cholesterol, triglycerides, phospholipids and protein. The α-tocopherol was distributed between high-density lipoprotein (69%), low-density lipoprotein (LDL; 22%) and very-low-density lipoprotein (VLDL; 9%). A retinol dose response (RDR)-test was carried out in both experimental groups to analyse the vitamin A status. The RDR-test indicated in some cases a false insufficient supply in spite of increased dietary vitamin A. However increased retinyl ester concentrations were found in serum and lipoproteins. Therefore concentrations of retinyl esters seems to be an excellent indicator for the vitamin A status of ponies. In lipoproteins, retinyl ester were measurable in VLDL and LDL. The main ester was retinyl stearate followed by retinyl palmitate. Data suggest that feeding increased concentration of vitamin A did not influence the serum vitamin E status and lipid parameters in ponies, but increased the retinyl esters in serum, VLDL and LDL. [ABSTRACT FROM AUTHOR]

Rhodococcus equi is a well-characterized bacterial pathogen which lyses cell membranes with the help of cholesterol oxidase (CO). Survival in macrophages is warranted by its ability to resist reactive radicals via catalase and superoxide dismutase (SOD). Therefore, CO production in the absence or presence of 0.1% cholesterol and sensitivity to exogenous hydrogen peroxide (H[sub 2]O[sub 2]) and superoxide anion (SEA) were tested in seven strains of R. equi in vitro. When R. equi strains were grown on agar plates with cholesterol, the bacterial growth [colony-forming units (cfu)/plate] did not increase significantly in comparison with the growth on plates without cholesterol. The activity of CO increased, significantly for extracellular CO. In subsequent experiments, R. equi strains grown on cholesterol were stressed with H[sub 2]O[sub 2] or SeA so that approximately 10 % of cfu/plate survived. During stress induced by SeA, membrane CO and SOD activity increased significantly. Catalase activity increased 2-fold with H[sub 2]O[sub 2] and 3-fold with SeA exposure. These data suggest that the presence of cholesterol induces CO in bacteria grown on agar plates. Catalase, SOD and even membrane-bound CO respond to reactive oxygen species. [ABSTRACT FROM AUTHOR]

Phospholipase D (PLD) is a receptor-regulated signalling enzyme involved in biological functions, such as exocytosis, phagocytosis, actin dynamics, membrane trafficking, and is considered to be essential for stimulated degranulation of cells. The purpose of our investigation was to examine how the fatty acid pattern of cellular membranes influences the activities and cellular distribution of the PLD1 and PLD2 isoforms. Expression of GFP-tagged PLD1 and PLD2 in COS-1 cells that were stimulated with mastoparan after cultivation in 20 micromol linoleic (C18:2n6) or linolenic (C18:3n3) acid for 4 d demonstrated that PLD1 dramatically alters its cellular distribution and is redistributed from intracellular vesicles to the cell surface. PLD2, on the other hand, maintains its localisation at the plasma membrane. The activity of PLD, which corresponds to PLD1 and PLD2, significantly increased two- to three-fold in the presence of the fatty acids. We conclude that linoleic acid and linolenic acid supplementation affect the intracellular trafficking of the PLD1 isoform and the activity of PLD most likely due to alterations in the membrane lipid environment conferred by the fatty acids.

Recent studies have indicated that dogs with canine atopic dermatitis (CAD) may have a disorder of fatty acid metabolism: possibly low or absent activity of delta6-desaturase or delta5-desaturase, or both. To clarify this possibility, we examined the erythrocyte and plasma fatty acid patterns of 8 dogs with CAD and their 8 healthy housemates. Atopic dermatitis was diagnosed according to the criteria proposed by Willemse; other causes of dermatitis were excluded clinically and by appropriate tests. Erythrocyte ghosts were prepared from blood samples. Membrane lipids were extracted and separated by thin-layer chromatography. From plasma and lipid fractions, fatty acid content was determined by gas chromatography. In erythrocytes, but not in plasma, we observed significant differences in the fatty acid pattern that suggested a reduction in the n6 fatty acid products of the delta6- and delta5-desaturases in dogs with atopic dermatitis when compared with healthy housemates.

We investigated the influence of polyunsaturated fatty acids on the activity of the cytosolic phospholipase A2 (cPLA2) in the canine mastocytoma cell line C2 as a model for canine atopic dermatitis (CAD). Cells were cultured in a basic medium or in media supplemented with different fatty acids (14 microM) for eight days. The supplemented fatty acids were linoleic acid (18:2n6), alpha-linolenic acid (18:3n3), gamma-linolenic acid (18:3n6) and docosahexaenoic acid (22:6n3). We measured enriched concentrations of the added fatty acid, their delta6-desaturated and elongated products. However, delta5-desaturated products were not increased. Culturing of C2 in 18:3n3 supplemented medium reduced the cPLA2 activity. Furthermore in these cells and in C2 cultured in 22:6n3 supplemented medium decreased the cPLA2 activity after stimulation. The reduced cPLA2 activity by the changed fatty acid pattern of C2 cultured in 18:3n3 or 22:6n3 possibly explain the beneficial effects of these fatty acids in CAD because increased cPLA2 activity is accompanied by enhanced release of proinflammatory type 2 prostaglandins and type 4 leukotrienes.

To investigate the influence of overweight and dietary fat supplementation on lipid and insulin glucose metabolism of Shetland ponies, eight Shetland pony geldings were fed a hypercaloric (30 MJ DE/150 kg bwt. and day) fat diet (10% fat as soybean oil) or a carbohydrate control diet for nine months until ponies gained an overweight of 15%. Afterwards oral glucose tolerance tests (oGTT; 5, 6 mmol/kg bwt.) were performed after a 12 hour fast and after a fast which led to an increase of plasma triglyceride concentrations to a threshold of 3 mmol/l (36-65 hrs.). Plasma concentrations of glucose, insulin, triglycerides and non esterified fatty acids (NEFA) were determined for 480 minutes after the glucose load. Ponys having had received the control diet tended to a higher insulin secretion in case of both oGTTs, whereas the glucose tolerance was similar in both groups but lower than in ponies of normal weight. During the oGTTs after fasting leading to the plasma triglyceride threshold, triglyceride concentrations decreased significantly (p < 0.05) faster and stronger in fat fed ponies. Additionally, fat fed pony showed significantly (p < 0.05) lower NEFA levels. The results of this study demonstrate a positive effect of fat feeding on the triglyceride clearance of overweight Shetland ponies.