Fat absorption and metabolism in bile duct ligated rats.

BACKGROUND: Bile excretion is obstructed in children with extrahepatic bile duct atresia (EHBA) resulting in fat malabsorption and disturbed lipid metabolism. AIM: Investigate if the bile duct ligated rat exhibits similar deviations as patients with EHBA under different feeding conditions. METHODS: 6 bile duct ligated Wistar rats and 12 matched paired controls were randomised over 3 feeding groups. Rats were killed 16 or 30 days postsurgery. Faeces, blood and livers were collected. Fat absorption was evaluated, markers for cholestasis and the fatty acid composition of serum phospholipids (PL) and cholesterol esters (CE) were determined. Fatty acid desaturation activities in liver microsomes were measured. RESULTS: Cholestatic bile duct ligated rats have a lower fat absorption coefficient and a lower fraction of 18:2n-6 and 18:3n-3 in serum triglycerides than their controls. This demonstrates that bile duct ligated rats suffer from fat malabsorption. In contrast to the observations in serum triglycerides, 18:2n-6 and 18:3n-3 were not reduced in serum PL and CE of cholestatic rats. Overflow of 18:2n-6 rich biliary PL in the general circulation could contribute to this observation. In agreement with what was found in man, serum PL of cholestatic rats have a higher 16:0/18:0 ratio, increased monoenes and reduced unsaturated fatty acids. However, no differences were observed in microsomal desaturation activities. CONCLUSION: Cholestatic bile duct ligated rats exhibit similar deviations in serum fatty acid composition as found in patients with EHBA, therefore they can be used as a model for this human disease.

Gas chromatographic characterization of vegetable oil deodorization distillate.

Because of its complex nature, the analysis of deodorizer distillate is a challenging problem. Deodorizer distillate obtained from the deodorization process of vegetable oils consists of many components including free fatty acids, tocopherols, sterols, squalene and neutral oil. A gas chromatographic method for the analysis of deodorizer distillate without saponification of the sample is described. After a concise sample preparation including derivatization and silylation, distillate samples were injected on column at 60 degrees C followed by a gradual increase of the oven temperature towards 340 degrees C. The temperature profile of the oven was optimized in order to obtain a baseline separation of the different distillate components including free fatty acids, tocopherols, sterols, squalene and neutral oil. Good recoveries for delta-tocopherol, alpha-tocopherol, stigmasterol and cholesteryl palmitate of 97, 94.4, 95.6 and 92%, respectively were obtained. Repeatability of the described gas chromatographic method was evaluated by analyzing five replicates of a soybean distillate. Tocopherols and sterols had low relative standard deviations ranging between 1.67 and 2.25%. Squalene, mono- and diacylglycerides had higher relative standard deviations ranging between 3.33 and 4.12%. Several industrial deodorizer distillates obtained from chemical and physical refining of corn, canola, sunflower and soybean have been analyzed for their composition.

Identification of alpha-tocopherol oxidation products in triolein at elevated temperatures.

The effect of high-temperature treatment on the stability of alpha-tocopherol (1) in triolein was assessed under a reduced-pressure atmosphere (4-40 mbar) simulating the deodorization step of the refining of vegetable oils. A marked degradation of 1 was observed, which increased with increasing temperature (180-260 degrees C) and heating time (20-80 min). The degradation of 1 in triolein at 240 degrees C was inhibited by the addition of the synthetic antioxidant TBHQ or when heating was performed under nitrogen atmosphere, indicating oxidative degradation. The oxidation products were isolated and identified as alpha-tocopherolquinone (2), 4a,5-epoxy-alpha-tocopherolquinone (3), and 7,8-epoxy-alpha-tocopherolquinone (4).

Substituting enzymatically interesterified butter for native butter has no effect on lipemia or lipoproteinemia in Man.

The aim of this study was to determine whether substituting enzymatically interesterified butter for native butter in the usual diet affects lipid and lipoprotein levels in man. Parameters studied were serum total cholesterol, LDL-cholesterol, HDL-cholesterol, free cholesterol, phospholipids, triglycerides, apoA1 and apoB and the fatty acid composition of serum triglycerides, free fatty acids, phospholipids and cholesterol esters. Subjects were healthy volunteers and a controlled design was used. The only mathematically significant difference found when interesterified butter was substituted for butter was an about 7% lower fraction of oleic acid in the serum cholesterol esters (p = 0.005). In contrast to an earlier study where chemically interesterified butter fat was substituted for native butter, no indications are found in this study that replacing native butter by enzymatically interesterified butter, in amounts normally consumed, may have any beneficial effect on health.

Contribution of trans fatty acids from vegetable oils and margarines to the Belgian diet.

Nineteen commercial samples of vegetable oils and margarines marketed in Belgium (nine margarines, nineteen vegetable oils), Hungary (seven margarines) and Great Britain (three margarines) were analyzed by gas-liquid chromatography for their trans fatty acid (TFA) content. For the vegetable oil samples under study, the TFA content ranged from 0.0-4.6% (mean : 1.1%, S.D. : 1.1%). Trans isomers in these samples were almost exclusively C18:2 and C18:3 isomers formed during high temperature refining. Trans isomers of the margarines were mainly C18:1 isomers formed during hydrogenation. For the Belgian and Hungarian samples mean trans values of 6.36% (S.D.=6.20%) and 14.06% (S.D.=7.59%), respectively expressed on fat basis were established. From these figures, the average daily intake of TFA from margarines and vegetable oils by the Belgian population was calculated at 1.1 and 0.1g/person/day, respectively. When so-called zero-trans margarines (+/- 0.5% TFA) are consumed, the trans intake can be reduced to about 0.1g/person/day. Further studies leading to figures about the contribution of TFA from 'invisible fat' food products will be conducted in the near future.