Effect of dietary animal and vegetable protein on gallstone formation and biliary constituents in the hamster

A gallstone-inducing diet was utilized to examine the effect of dietary proteins (casein, soybean and cottonseed) on gallstone formation. Casein produced gallstones in 100% of the animals; however, soybean or cottonseed proteins reduced gallstone incidence to 32% and 0%, respectively. In an effort to ascertain the mechanisms responsible for gallstone formation, serum cholesterol and the 3 primary biliary constituents (bile acids, phospholipids and cholesterol) were measured. Casein produced a 4-fold increase in biliary cholesterol, whereas soybean and cottonseed yielded a 3-and 2-fold increase, respectively, when compared to a commercial diet (Purina, no. 5001). Serum cholesterol was reduced by substituting dietary vegetable protein for animal protein. This study suggests that substitution of vegetable for animal protein in the diet can decrease gallstone formation in hamsters. It is proposed that this reduced gallstone formation is due to the decreased concentrations of biliary cholesterol induced by dietary modification. Preliminary reports of portions of this work were presented at the XIIth International Congress of Nutrition and at the 73rd annual AOCS meeting. Liepa, G., and Mahfouz, S. (1982) J. Am. Oil Chem. Soc. 59, 316A     

Interaction between dietary proteins and lipids in the regulation of serum and liver lipids in the rabbit. Effect of fish protein

Purified diets varying in dietary protein, namely casein (CA), soy protein (SP), fish protein (FP), and lipid origin (corn oil (CN), coconut oil (CO)) were fed to rabbits to evaluate the effects of protein and fat source, as well as protein-lipid interactions, on serum total, lipoprotein and hepatic lipid levels. Dietary proteins and lipids exerted a separate effect on serum total cholesterol (C), very low-density lipoprotein cholesterol (VLDL-C), and low-density lipoprotein cholesterol to high density lipoprotein cholesterol (LDL-C/HDL-C) ratio. Hence, CA increased serum cholesterol compared to SP, while coconut oil enhanced serum and VLDL-C, and decreased LDL-C/HDL-C compared to corn oil. Dietary proteins interacted with dietary lipids to modulate HDL-C levels. Thus, FP maintained a high level of HDL-C regardless of lipid origin, compared to CA and SP whose HDL-C levels were decreased by corn oil, compared to coconut oil. A dietary protein-lipid interaction was also observed in the regulation of liver cholesterol levels. Coconut oil, compared to corn oil, decreased liver cholesterol in rabbits fed FP, whereas hepatic cholesterol concentration was unaltered by dietary lipid source in CA- and SP-fed rabbits. These results demonstrate that dietary proteins act synergistically with dietary lipids to regulate cholesterol metabolism in the rabbit. This work was presented in part at the 74th Annual FASEB meeting held in Washington, D.C., April 1–5, 1990.     

The relationship of corn oil and animal fats to serum cholesterol values at various dietary protein levels

Summary A high level of dietary protein lowered serum cholesterol. Incorporation of increasing amounts of beef tallow did not increase the serum cholesterol levels significantly, and some dietary fat was found to be desirable. Addition of up to 0.3% of dietary cholesterol did not significantly increase the serum cholesterol levels on either low or high levels of dietary fat or protein. The energy protein (E/P) ratio of a diet had a significant effect on serum and carcass cholesterol levels. The type of fat had an effect on serum cholesterol levels, but with lowering of the E/P ratio this effect became negligible. Presented at the 32nd Annual Fall Meeting, American Oil Chemists' Society, October 21, 1958, Chicago, Ill. The work was supported by research grant No. H-1819 from the National Institute of Health, U. S. Public Health Service, Department of Health, Education and Wealfare. Portion of a thesis to be presented by M. G. Kokatnur as partial fulfillment of the requirements for the degree of Doctor of Philosophy in Food Technology.     

Effects of bile acid oxazolines on gallstone formation in prairie dogs

The effects of 2 bile acid analogs, chenodeoxy-oxazoline [2-(3α,7α-dihydroxy-24-nor-5β-cholanyl)-4,4-dimethyl-2-oxazoline] and ursodeoxy-oxazoline [2-(3α, 7β-dihydroxy-24-nor-5β-cholanyl)-4,4-dimethyl-2-oxazoline] were examined in the prairie dog model of cholesterol cholelithiasis. Gallstones and biliary cholesterol crystals were induced in 5 out of 6 male prairie dogs fed a semisynthetic diet containing 0.4% cholesterol for 8 weeks. Six animals maintained on a low cholesterol control diet (0.08% cholesterol) exhibited neither gallstones nor biliary cholesterol crystals. The addition of 0.06% chenodeoxy-oxazoline to the lithogenic diet did not prevent induced cholelithiasis or the appearance of cholesterol crystals in bile. In contrast, 0.06% dietary ursodeoxy-oxazoline prevented gallstones in 5 out of 6 prairie dogs (but cholesterol crystals were present in the bile of 4 of these animals). Histologically, most of the livers from the prairie dogs fed the cholesterol-supplemented semisynthetic diet showed bile duct proliferation, inflammatory infiltration and fibrosis along the portal tracts. These pathologic changes were generally not ameliorated by adding chenodeoxy-oxazoline or chenodeoxy-oxazoline plus chenodeoxycholic acid to the diet. Portal tract pathology was markedly reduced in most animals by adding ursodeoxy-oxazoline to the cholesterol-supplemented diet. The pathologic changes overall could best be correlated with the presence of gallstones, but not with the incidence of biliary cholesterol crystals.     

Cholelithiasis in hamsters: Effects of cholic acid and calcium on gallstone formation

Dietary cholic acid (0.1%) and/or calcium (2.6% as calcium carbonate) were added to a semipurified diet containing cholesterol and ethynyl estradiol to determine whether the incidence of pigment and/or cholesterol gallstones would be changed. Male golden Syrian hamsters were fed the experimental diets for 96 days (Group 1, control; Group 3, cholic acid plus calcium) or only an average of 60 days (Group 2, 0.1% cholic acid). Animals in Group 2 became ill (weight loss, low food intake, diarrhea) possibly due to cholic acid (or deoxycholic acid) toxicity. Cholesterol gallstones and crystals were absent in all experimental groups. The incidence of pigment gallstones was: control, Group 1, 12/16; 0.1% cholic acid, Group 2, 3/13; and 0.1% cholic acid plus calcium, Group 3, 11/22. Cholic acid with or without calcium produced an elevation of both liver and plasma cholesterol: Group 2, 80.1 mg/g and 501 mg/dl; Group 3, 103.7 mg/g and 475 mg/dl vs Group 1, 65 mg/g and 209 mg/dl, respectively. The lithogenic indices of the bile were lower in Groups 2 and 3 compared to Group 1, controls, 0.45 and 0.58 vs 1.16, respectively. The extent of the portal tract pathology could not be correlated with the presence or absence of pigment gallstones or with the levels of lithocholic acid in the hamster bile. In summary, when semipurified diets were supplemented with ethynyl estradiol and cholic acid, with and without calcium supplementation, no cholesterol gallstones formed and the incidence of pigment gallstones was not altered.     

Factors influencing the formation of complexes between oxidized lipids and proteins

Complexes were formed between egg albumin and oxidized lipids, such as thermally oxidized corn oil and autoxidized linoleic acid, under a standardized set of conditions. No complex could be obtained under these conditions when lysine, glycine, bactopeptone, gelatin or sodium caseinate were substituted for egg albumin. Lactalbumin was equally as reactive, casein much less and fresh egg white superior to egg albumin in their complexing ability with oxidized corn oil. As the time of reaction was increased, the amount of the complex formed also increased. Optimum complex formation took place at a concentration of 1% protein, a pH of 7 and 60C. The ease of formation of these complexesin vitro indicated that similar complexing could readily take placein vivo under suitable pathological conditions. This work was supported by research grant no. C-1932 from the National Institutes of Health, U. S. Public Health Service, Department of Health, Education, and Welfare.     

Effect of biliary obstruction on canine plasma and biliary lipids

The common bile duct was obstructed in 17 dogs. Reciprocal changes were noted for the plasma and biliary lipid concentrations of each after obstruction. As the plasma lecithin and free cholesterol concentrations increased, the biliary lipid concentrations declined. After biliary obstruction the reflux of biliary lecithin into the plasma of these animals was demonstrated with both labeled and unlabeled lecithin. The plasma lipid abnormalities seen after acute biliary obstruction were closely simulated by the reflux of lecithin alone from the biliary tree. The isolated reflux of biliary tract taurocholate produced a distinct lowering of plasma phospholipid and cholesterol concentrations, quite different from the plasma lipid alteration noted with acute biliary obstruction. Similar to observations in human obstruction, some of the plasma lipid was in mesophase form after these animals were obstructed.     

Effects of vegetable proteins on iron and zinc absorption and availability in humans

This review discusses research on the effects of vegetable protein diets on iron and zinc absorption and availability. Constituents of vegetables can have either a positive or negative effect on iron absorption. Although the use of soy protein to extend beef patties was found to decrease nonheme iron absorption in some studies, the use of soy-extended beef on a regular basis was not found to deleteriously affect the iron status (serum ferritin levels) of adult men, menstruating females or school age subjects. Factors such as phytic acid level, dietary fiber content or protein source of vegetable protein diets have been implicated in decreasing the utilization of iron and zinc by humans. The effect of the molar ratio of phytate on the zinc of the diet is controversial: some studies find a decrease in zinc absorption with an increase in the phytate to zinc molar ratio; other studies find zinc absorption more dependent on the total amount of zinc in the meal than on the presence of phytic acid. Since many people meet their energy and protein requirements from vegetable sources, attention should be given to the mineral availability of these diets.     

Effects of dietary linolenate on the fatty acid composition of brain lipids in rats

Weanling male rats were fed hydrogenated coconut oil to induce essential fatty acid (EFA) deficiency. After 15 weeks, the rats were divided into six groups. Five groups were fed graded amounts of purified linolenate (18∶3ω3) with a constant amount of linoleate (18∶2ω6) for six weeks. Fatty acid composition was determined in brain lipids. Increasing dietary 18∶3ω3 resulted in a decrease in arachidonic acid (20∶4ω6), docosatetraenoic acid (22∶4ω6) and docosapentaenoic acid (22∶5ω6), whereas 18∶2ω6 and eicosatrienoic acid (20∶3ω6) were increased both in total lipids and phospholipids. These results suggest that dietary 18∶3ω3 exerts its inhibitory effect mainly on the desaturation of 20∶ω6 to 20∶4ω6 in brain lipids. Linolenate was undetectable in brain lipids from any dietary treatments. The levels of eicosapentaenoic acid (20∶5ω3) in groups receiving dietary 18∶3ω3 were not different from that of the group receiving no 18∶3ω3. These results indicate that, in the brain, 18∶3ω3 is rapidly converted mainly to 22∶6ω3 without being accumulated and imply that dietary 18∶3ω3 can modulate the level of precursor of diene prostaglandins (PG) but not that of triene PG in the rat brain.     

Effects of dietary fish oil on biliary phospholipids and prostaglandin synthesis in the cholesterol-fed pairie dog

Cholesterol gallstone formation in the prairie dog is accompanied by an increase in the percentage of biliaryphospholipids containing arachidonic acid, and an increase in gallbladder prostaglandin (PG) synthesis, but the pathogenetic significance of these changes is unclear. Dietary supplementation with eicosapentaenoic acid (EPA), an omega-3 fatty acid which is commonly found in fish oil, decreases prostaglandin synthesis in some tissues by replacing arachidonic acid, and by competitively inhibiting prostaglandin synthesis. We studied the effect of dietary fish oil on gallbladder PG synthesis, and the relative abundance of various molecular species of phosphatidylcholines and phosphatidylethanolamines in bile and gallbladder epithelium in the cholesterol-fed prairie dog. Prairie dogs were maintained for 4 weeks on one of four diets: i) control, ii) cholesterol-supplemented (0.34%), iii) menhaden oil (50 g/kg chow), or iv) cholesterol plus menhaden oil. Supplementation with menhaden oil resulted in a replacement of arachidonic and linoleic acids with EPA and docosahexaenoic acids in the phospholipids of bile and gallbladder mucosa. In cholesterol-fed animals, supplementation with menhaden oil prevented increased gallbladder PG synthesis. Menhaden oil also reduced the incidence of cholesterol monohydrate crystals among cholesterol-fed animals (9/20 with cholesterol plus menhaden oil vs 21/22 with cholesterol alone), but the improvement could not clearly be attributed to decreased PG synthesis since supplementation with menhaden oil also increased the total phospholipid concentration in bile, and decreased the degree of cholesterol saturation. These results demonstrate that dietary supplementation with omega-3 fatty acids significantly influences biliary phospholipids, and decreases the incidence of cholesterol monohydrate crystal formation in this animal model.     

Effects of dietary conjugated linoleic acids on hepatic and muscle lipids in hybrid striped bass

Conjugated linoleic acids (CLA) are the focus of numerous studies, yet the effects of these isomers of octadecadienoic acids have not been evaluated in many species of fish. In this study, graded amounts of CLA-0,0.5, 0.75, or 1.0% of the diet—were fed to juvenile hybrid striped bass for 8 wk. Dietary treatments were fed to apparent satiation twice daily to triplicate groups of fish initially weighing 13.4 g/fish. Feed intake and weight gain of fish fed 1.0% CLA were significantly reduced compared to fish fed no CLA. Fish fed 0.5 and 0.75% CLA exhibited reduced feed intake similar to fish fed 1.0% CLA, but had growth rates that were not significantly different from those of fish fed no CLA. Feed efficiency improved significantly in fish as dietary CLA concentrations increased. Total liver lipid concentrations were significantly reduced in fish fed the diets containing CLA compared to those of fish fed the control diet, and intraperitoneal fat ratio was significantly lower in fish fed 1.0% CLA compared to fish fed no CLA. Fish fed dietary CLA exhibited significant increases in hepatosomatic index and moisture content of muscle and carcass. The CLA isomers were detected in liver and muscle of fish fed the diets containing CLA, while a low concentration of one isomer was detected in liver and muscle of fish fed the control diet. Dietary CLA resulted in a significant increase in 18∶2(c-9,c-12) concentration in liver and muscle, but a significant reduction in 18∶1n−7 in these tissues. Furthermore, feeding CLA resulted in a significant increase in the concentration of 20∶5n−3 and 22∶6n−3 in liver, but a reduction of these fatty acids in muscle. This study showed that feeding CLA elevated tissue concentrations of these fatty acid isomers, reduced tissue lipid contents, improved feed efficiency, and altered fatty acid concentrations in liver and muscle of fish.     

The effects of phenobarbital on biliary lipid metabolism in cholesterol gallstone subjects

The effect of 1.7–2.2 mg/day oral phenobarbital over short (1 MO) and long term (6–24 MO) treatment on primary bile acid (BA) secretion, composition, synthesis, pool size, and enterohepatic cycling rates as well as phospholipid (PL) and cholesterol (C) secretion rates and biliary composition was determined in 12 asymptomatic cholesterol gallstone subjects while 5 normals had only short term studies. Phenobarbital enhanced BA and C secretion (BA-636±166 to 2110±382 mg/hr, p<0.001 and C-42±5 to 224±48 mg/hr, p<0.001) and BA cycling rate in all subjects studied during stimulated enterohepatic circulation but, during fasting, it only enhanced BA secretion (451±129 vs. 759±159 mg/hr, p<0.05) in gallstone subjects. Cholic acid (CA) production rate (171±28 to 395±9 mg/hr, p<0.05) and pool size (727±80 to 1209±132 mg/hr, p<0.05) were increased during long term treatment of gallstone subjects, while the proportion of CA in bile and deoxycholic acid (DCA) in feces increased. Treatment decreased biliary cholesterol from supersaturated to saturated levels (9.5±0.6 vs. 6.1±0.9 moles%, p<0.02) in all fasting gallstone subjects and decreased cholesterol crystal loads during long term treatment; but, while prohibiting gallstone growth, it did not affect stone dissolution over 24 month's treatment. Phenobarbital also failed to affect biliary lipid composition or bile acid pool size in short term treatment of normals. Thus, phenobarbital affected hepatic metabolism of CA by enhancing production rate, secretion, and pool size; and in testinal metabolism of both CA and chenodeoxycholic (CDC) acids by increasing their cycling rates. Phenobarbital may have failed to produce stone dissolution by enhancing CA production and pool size more than that of CDC. Portions of this work were presented at the National Meeting of the American Federation of Clinical Research, Atlantic City, April 29, 1973 and at the Annual Meeting of the Canadian Society of Clinical Investigation, Winnepeg, Manitoba, January 21, 1975 as well as that of the Royal College of Physicians and Surgeons of Canada, January 27, 1977 at Toronto, Canada.     

Effects of ethanol ingestion and dietary fat levels on mitochondrial lipids in male and female rats

The effects of sex, dietary fat levels, and ethanol ingestion on rat liver mitochondrial lipids have been studied. Two groups of male animals were fed either a low-fat diet for about 76 days or a high-fat diet for about 52 days, and two groups of female animals were fed the same low-fat diet for about 50 days or the high-fat diet for about 37 days. Ethanol was substituted isocalorically for carbohydrate and amounted to 36% of total calories. The total as well as individual concentrations of fatty acids, phospholipids, and neutral lipids were determined in all eight groups of animals. Variable changes were observed in the total fatty acid composition of mitochondria from each of the four groups of animals. After ethanol ingestion, there was a decrease in arachidonate/linoleate ratio in males, while no change was observed in females. Increasing the fat content of the diet decreased this ratio in both controls and experimentals, but it did not alter the effects of ethanol on either sex. Presumably, this was due to the fact that corn oil was the only source of lipid. After ethanol ingestion, the total fatty acid concentration increased in all groups of animals except the males fed the low-fat diet. A decrease was observed in this group. The same pattern of change was reflected in changes in total phospholipid concentrations. In each case, the majority of the concentration change in total phospholipid could be accounted for by changes in phosphatidylcholine (PC). Measurement of choline oxidase (C.O.) showed that ethanol ingestion increased C.O. activity only in the low-fat group of males. No change was observed in the other three groups. Chronic ethanol ingestion is known to increase the methylation of phosphatidylethanolamine (PE); therefore, in order to decrease PC, the increase in C.O. in the low-fat males must have been of sufficient magnitude to offset the increase in PE methylation. Increasing the fat content of the diet offset the effect of ethanol on C.O. in males. Neither ethanol nor fat exerted much effect on C.O. in females. These results emphasize the importance of dietary levels of fat as well as sex in the study of liver mitochondria structure and function in relation to ethanol metabolism. This work was presented at the AOCS Meeting, New York, May 1977, at which J.A.T. was an Honored Student Awardee.     

Effects of dietaryTrans-fat on biliary and fecal steroid excretion and serum lipoproteins in rats

Rats were fed cholesterol-free or cholesterol-enriched diets containing olive oil or partially hydrogenated corn oil at the 10% level for ca. 30 days (c-18∶1, 77.0% in the former diet andc-18∶1, 24.7% andt-18∶1, 42.5% in the latter). The linoleic acid content of these fat diets was made equivalent (1.7 energy%). After feeding cholesterol-free diets,trans fat compared tocis fat showed(a) no untoward effects on growth parameters, (b) a reduction of serum cholesterol levels without influencing concentrations of serum apolipoproteins A-I, B and E, (c) no effects on the bile flow and the concentration of biliary cholesterol and bile acids, (d) an increasing trend of fecal excretion of neutral and acidic steroids, both in terms of mg/day and mg/g feces, and (e) rather equivocal change in the composition of fecal, but not biliary steroids. Similar response patterns were also observed when cholesterol-enriched diets were fed except for a decrease in serum apo B and an ineffectiveness to increase fecal acidic steroids. Together with the results obtained from experiments simultaneously performed with safflower oil and completely hydrogenated corn oil, it seems that the steroid metabolism can be specificallymodified by the geometry of dietary fats.     

Effects of various parameters on the formation of radiolysis products in model systems

Effects of various parameters on the formation of radiolysis products in triplamitin, palmitic acid, oleic acid, caprylic acid and capric acid were investigated. A greater yeild of primary and recombination products was observed in palmitic acid compared to that of oleic acid. In general, higher amounts of recombination products are formed in both acids when irradiated at room temperature than at −45 C. In the short chain acids, the yield of the hydrocarbon recombination product was enhanced in the liquid state. In contrast, the ketone recombination product was formed in greater amounts from solid capric acid than from liquid caprylic acid. In the absence of oxygen, a linear relationship was obtained between the dose and the yield of radiolysis products in tripalmitin. In the presence of oxygen, a considerable increase in the formation of γ-palmitolactone, n-3 and n-2 alkanes was observed at room temperature.     

The effect of dietary supplementation of cholesterol and its subsequent withdrawal on the liver lipids and serum lipoproteins of chickens

Two groups of male chickens were fed either a control diet (group N) containing a standard poultry ration admixed with 10% corn oil or a cholesterol diet (group C) in which the control diet was supplemented with 1% cholesterol. After 6 weeks on the diets, a negligible amount of very low density lipoprotein (VLDL) was found in the serum from control animals. On the other hand, the serum VLDL from the cholesterol-fed birds was the predominant lipoprotein and carried 72% of the total serum lipids. Surprisingly this lipoprotein from cholesterol-fed animals was very low in triglycrides (6%) and high in total cholesterol (77%). While the level of serum low density liporotein was unaffected by the ingestion of cholesterol, the concentration of total lipids and phospholipids in the high density lipoprotein decreased in cholesterol-fed animals. The greatest change in liver lipids from animals fed cholesterol was found in the cholesterol esters, whereas the unesterified cholesterol, triglyceride and phospholipid varied slightly or remained constant. In normal animals the distribution of cholesterol between the liver and the serum was about equal, whereas in the cholesterol-fed birds the liver accounted for 80% of the cholesterol found in the liver-serum pool. In order to determine how the hypercholesterolemic bird responds to the withdrawal of cholesterol from the ration, a diet-exchange experiment was conducted. In this study the birds that were originally fed the cholesterol diets (group C) for 6 weeks were placed on the control diet (group CN) and the birds fed the control diet (group N) for 6 weeks were given the cholesterol diet (group NC). At periodic intervals, 1, 3, 7 and 14 days following the change of diets, 3–5 animals from each group were sacrificed, and analyses performed on their serum lipoproteins and liver lipids. Within one day after the diet substitution, there was a 31-fold increase and a 46% decrease, respectively, in the serum VLDL concentration in groups NC and CN as compared with their corresponding steady state values (groups N and group C, respectively). The liver cholesterol increased 4-fold and decreased 40%, respectively, in the two groups NC and CN as compared with the values obtained before the diet substitution. It is suggested that the concentration of cholesterol in the liver is the principal factor controlling cholesterol metabolism in chickens fed a hypercholesterolemic diet. This represents a portion of a Ph.D. thesis submitted by A.W. Kruski to the University of Illinois in February 1971.     

Effects of fat crystallization on the behavior of proteins and lipids at oil droplet surfaces

The effects of fat crystallization induced by thermal treatment on the rheological properties of creams and physical phenomena at the oil droplet surfaces were investigated. Creams A or B were prepared from commercial proprietary fats A or B (vegetable oils with different triaclyglycerol composition) and aqueous solution containing proteins. Thermal treatment of the creams at the “critical temperatures” (temperatures inducing a small percentage of solid fats in the oil droplets) caused a rapid increase of solid fat contents in the following cooling process. The thermal treatment of cream B at the “critical temperature” caused an increase of viscosity of the cream and an increase of protein surface coverage during the subsequent cooling process. These results suggest that the oil droplet aggregation induced by the thermal treatment at the “critical temperature” and the subsequent cooling occurred via further adsorption of proteins. Electron spin resonance measurement demonstrated the dramatic reduction of fluidity of triacylglycerol molecules at the oil droplet surface in cream B during the cooling process after thermal treatment at temperatures below “critical”. Based on these results, we speculated on the mechanism for the destabilization of thermally treated creams during the cooling process.     

Effects of dietary conjugated linoleic acid on the expression of uncoupling proteins in mice and rats

CLA inhibits mammary cancer and reduces body fat accumulation in rodents. It is not known whether uncoupling proteins (UCP), which are modulators of energy balance and metabolism, play a role in these actions of CLA. To determine the effects of dietary CLA on the expression of UCP in various tissues, 5-wk-old Sprague-Dawley rats and C57BI/6 mice were fed diets containing 1% CLA for 3 wk. CLA treatment reduced adipose depot weights in both rats and mice but had no significant effects on body weight. There was a species-specific effect of CLA on the expression of UCP. Whereas CLA did not affect the expression of UCP in most tissues in rats, mice fed CLA had increased expression of UCP2 in the mammary gland, brown adipose tissue (BAT), and white adipose tissue (WAT). Furthermore, UCP1 and UCP3 mRNA and protein levels in BAT were significantly lower in CLA-fed mice compared to controls. Skeletal muscle UCP3 mRNA was unchanged, but UCP3 protein levels were significantly increased in mice, suggesting translational or posttranslational regulation of this protein. Results from this study suggest that alterations in the expression of UCP in mice may be related to the previously reported effects of dietary CLA in lowering adiposity and increasing FA oxidation. In rats, however, induction of UCP is not likely to be responsible for fat reduction or for the inhibitory action of CLA on mammary carcinogenesis.     

Investigations on physical refining of animal fats and vegetable oils

Alcohols, polyethyleneglycols, supercritical fluids, and some of their mixtures have been investigated as to their usefulness to purify animal fats and vegetable oils by extraction. The main impurities are free fatty acids. Phase equilibrium was measured as function of temperature and pressure. As primary substances abattoir fat and palm oil were used. Carbon dioxide, dimethylether, and mixtures thereof, likewise methanol and ethanol were tested as extractants for free fatty acids by counter-current extraction in a pilot plant including a high-pressure column and by cross-flow extraction on laboratory scale. With experiments and process simulations including the recovery of the extractants the deacidification of animal fats and vegetable oils was found to be possible. Polyethyleneglycols extract carotenes together with free fatty acids. With the physical refining methods investigated, the formation of waste materials was avoided.