Rat Fat Research Articles

Modifications of nutrient selection induced by naloxone in rats.

Total caloric intake and dietary self-selection of the three macronutrients protein, fat, and carbohydrate were examined in male rats maintained on a 6-h feeding schedule following the administration of the opioid antagonist naloxone HCl (0.1, 1.0, and 10.0 mg/kg IP). Total caloric intake (calculated as the sum of caloric intakes from each of the macronutrients) was decreased for up to 2 h following naloxone administration. By the end of the 6-h feeding period, however, no differences in total caloric intakes were observed as a function of naloxone injections. Examination of intakes of the individual macronutrients revealed that naloxone differentially affected fat, carbohydrate, and protein consumption. Across the 6-h feeding period, animals consumed less calories from the fat ration following all three doses of naloxone than after saline injections. Carbohydrate intake was decreased up to 2 h following naloxone injections, but returned to control values by the end of the 6-h feeding period. Protein intake, in contrast to fat and carbohydrate intakes, did not vary as a function of naloxone administration. Results of the present examination are contrasted with patterns of dietary self-selection observed following morphine administration.

Effect of Fluoride on the Absorption of Dietary Fat in Rats

The inhibition of lipid absorption by sodium fluoride in adult male rats was investigated following intraduodenal infusion of labeled lipid and cannulation of the intestinal lymphatics. A striking delay in both the appearance and total amount of lymph radioactivity was observed when 26 mm fluoride was included in the infusate. Effective inhibition of lipid absorption was observed over a 15-fold wide range of fluoride concentration (3.3–56 mm). The inhibitory effect of fluoride was not due to an inhibition of lipolysis since the absorption of free palmitic acid was inhibited to the same extent as that of tripalmitoyl glycerol. Studies on the uptake and distribution of infused lipid in the upper small intestine and experiments examining the extent of fluoride-induced absorptive inhibition of different fatty acids suggest that the effect of fluoride may be on the mucosal reesterification of dietary lipid.fluoride lipid absorption mucosal reesterification

Relation between dietary fat composition and lipid metabolism in the rat

Three fats were used in a synthetic dietary formula containing 20% of its composition as fat from either lard, peanut oil or maize oil. Twelve groups of rats were included in this study, six groups served as controls; 3 from each sex. Control groups received the same dietary formula except fat content was 10%. Saturated dietary fats in male rats seems to be atherogenic while in females, increasing dietary fat to 20% gave atherogenic picture.

Burden and dose-related neurochemical effects of intermittent cyclohexane vapour inhalation in rats

Intermittent daily inhalation exposure to 300,1000 or 2000 ppm of cyclohexane vapour resulted in a dose-dependent solvent concentration in the perirenal fat in rats. The linear relationship changed between the first and second week of exposure as the body solvent burden decreased, despite the continued exposure: this was especially clear in the brain cyclohexane analyses. The salient feature in the brain was the reduction in the activity of azoreductase, while no change could be found in the RNA or glutathione content or in glutathione peroxidase activity. The azoreductase activity was somewhat below the control range after a 2-week withdrawal period, while no solvent could be found and other biochemical variables were within the control ranges.

High Fat Rations for Dairy Cows. Tallow and Hydrolyzed Blended Fat at Two Intakes

Tallow and blended animal-vegetable fat were mixed as 10% of diet concentrate and compared with a concentrate containing no added fat. Concentrate containing fat was fed at two percents of diet dry matter, 50% (supraenergetic) and 33% (isoenergetic). The dry matter of the control diet was 50% concentrate. Isoenergetic high fat diets contained more fiber than control or supraenergetic high fat diets.Change of body weight and intake of feed dry matter were not different among feed groups. Milk and 4% fat-corrected milk production were less when high tallow was fed. Milk fat percent was lowest on the high concentrate diet, intermediate with high grain-high fat feeding, and normal with high fat isoenergetic rations. Multiple regression analysis of digestibility data showed that fat did not influence diet digestibility negatively and that calcium positively influenced digestibility of all diet components.

Extraction and determination of chloroform in rat blood and tissues by gas chromatography-electron-capture detection: distribution of chloroform in the animal body.

Abstract We have developed a simple, sensitive, and accurate method for the determination of chloroform in rat blood, brain, kidney, liver, and fat. The detection limit is 2.5 ng of chloroform per gram of tissue. Studies of in vivo distribution of chloroform in rat blood and target tissues after intragastric intubation of chloroform/water show that the amount of chloroform accumulated in the different tissues increases with increasing doses. Fat tissue contains the greatest amount of chloroform. The accumulation of chloroform in rat blood and target tissues seems to be maximum 1.5 h after administration, and the apparent chloroform concentration is almost at baseline value 8 h later.

Extraction and determination of chloroform in rat blood and tissues by gas chromatography-electron-capture detection: distribution of chloroform in the animal body.

We have developed a simple, sensitive, and accurate method for the determination of chloroform in rat blood, brain, kidney, liver, and fat. The detection limit is 2.5 ng of chloroform per gram of tissue. Studies of in vivo distribution of chloroform in rat blood and target tissues after intragastric intubation of chloroform/water show that the amount of chloroform accumulated in the different tissues increases with increasing doses. Fat tissue contains the greatest amount of chloroform. The accumulation of chloroform in rat blood and target tissues seems to be maximum 1.5 h after administration, and the apparent chloroform concentration is almost at baseline value 8 h later.

Effect of Low Temperature, Diet Density, and Pelleting on the Preference of Broilers for High Fat Rations

Two experiments were conducted to determine whether a previously observed preference of broiler chicks for high fat vs. low fat rations would also be noted: 1) under cold conditions, 2) when energy and nutrient density are increased, and 3) when the physical texture of test rations is equalized by pelleting.In the first experiment conducted in unheated houses under winter conditions, diets compared were A) low-fat low density, B) high fat-high density, and C) high fat-low density. These were offered in pairs (A vs. B, A vs. C, B vs. C) to broiler chicks 4 to 7 weeks of age. A highly significant preference was shown for the high fat-high density diet over both low density diets and for the high fat-low density over the low fat-low density diet.In the second experiment high fat and low fat rations were presented in either mash or pelleted form. Regardless of physical texture, the high fat diet was again preferred by a highly significant (P≤ .01) margin.The relative position of feeders had no apparent influence on the pattern of feed consumption.

Inhibition of rat and human adipocyte adenylate cyclase in the antilipolytic action of insulin, clofibrate, and nicotinic acid

Clofibrate (Atromid-S), nicotinic acid, and insulin are known to be potent hypolipidemic and antilipolytic agents. The present study was undertaken to define the mechanism of action of this latter effect on isolated rat and human fat cells. Sodium clofibrate (0.42 mM), nicotinic acid (0.42 mM), and insulin (100 microU/mL) were shown to inhibit norepinephrine-stimulated lipolysis in rat and human adipose cells and this inhibition was associated with a reduction in intracellular 3',5'-cyclic AMP levels. A similar cyclic AMP lowering effect was demonstrated with insulin in the presence of procaine-HCL, which uncouples the adenylate cyclase system from lipolysis. This insulin effect was attributed to inhibition of adenylate cyclase. A direct and significant inhibition of adenylate cyclase in membrane fractions obtained from isolated human adipocytes was demonstrated for all three antilipolytic agents. The common membrane site of action of these agents whereby adenylate cyclase activity is depressed, thus decreasing cyclic AMP production and free fatty acid (FFA) mobilization from adipose stores, implies a central role for the adenylate cyclase system. These findings are consistent with the view that the hypotriglyceridemic effects of clofibrate, nicotinic acid, and insulin may be partly explained by deprivation of FFA substrate for hepatic very low density lipoprotein synthesis.

Effects of Dietary Composition on Somatomedin Activity in Growing Rats

Young growing rats were used to evaluate the effect of dietary composition on growth rate, body and organ weights, biochemical composition of brain and liver, plasma growth hormone concentration, and plasma somatomedin ( SM) activity. Young male rats ( 10/group ) were fed four levels of dietary protein (casein: 2.5, 5, 10, and 20%) and three levels of dietary fat (corn oil: 1.2, 10, and 20%) over a 30-day period. Changes in total body and organ weights paralleled increasing dietary protein and were affected to a lesser extent by dietary fat. Liver protein paralleled in creasing dietary protein. Glycogen, protein, DNA, and RNA determinations on the brain were not significantly influenced by dietary manipulation. Plasma growth hormone concentrations were not significantly different due to dietary protein or fat. Plasma SM activity was positively correlated with dietary protein levels (0.80 units/2.5% protein for all fat levels to 1.35 units/20% protein for all fat levels). Plasma SM was suppressed approxi mately 25% with increasing dietary fat in rats fed the 207r protein diets. Furthermore, SM appears to be directly related to food efficiency ( g gain/ 100 kcal) and body weight change. These data suggest that dietary com position has a direct effect on plasma SM activity and that the severe growth retardation associated with protein malnutrition may be related to its additional effect on serum SM. J. Nutr. 109: 613-620, 1979.

Regulation of phosphoenolpyruvate carboxykinase and fatty acid synthetase in brown fat of suckling rats.

Infant rats were injected with prednisolone (0.5-5 mg/100 g wt). This caused phosphoenolpyruvate carboxykinase (PEPCK) activity to rise in liver and to decrease in brown fat. Fatty acid synthetase (FAS) activity remained unchanged in liver but increased in brown fat. A single injection of prednisolone caused hepatic PEPCK activity to remain elevated for at least 7 days. Brown fat FAS also remained high for that period. However, brown fat PEPK activity returned to normal on the third day after the injection. A single injection of prednisolone or cortisone to 5-day-old rats caused a transient elevation of the blood level of insulin and a prolonged decrease in that of growth hormone. No effect on the level of glucagon was noted. Injections of insulin had effects similar to those of prednisolone, i.e. a rise in hepatic and a fall in brown fat PEPCK. Using antibodies prepared to hepatic PEPCK it was shown that the observed changes were due to changes in the rate of synthesis of the enzyme. Using actinomycin D indirect evidence was obtained that changes in FAS activity of brown fat were also due to changes in the synthetic rate.

Influence of a Liquid Diet and Meal Pattern on Body Weight and Body Fat in Rats

Rats weighing 110 to 150 g or 250 g initially were utilized in five experiments to determine the effect of the form of the diet (dry versus liquid) and the pattern of feeding (meal-feeding, force-feeding, nibbling, or ad libitum) on body weight gain and on body fat. A high-carbohydrate, 20% casein or 20% lactalbumin diet was fed for 4 to 8 weeks. Consumption of a diet mixed with an equal weight of water increased weight gain in one of three experiments. Body fat content of the rats was not influenced by addition of water to the diet. Neither force-feeding nor meal-feeding influenced body fat gain provided the respective control rats were pair-fed during the initial adaptation period. Likewise, when rats were pair force-fed to ad libitum fed rats without an initial adaptation meal frequency did not influence body fat gain. When meal-fed rats were switched to ad libitum intake their food intake increased to equal that of rats which had been continuously fed ad libitum; however, the rats which had been switched gained more body fat than did rats continuously fed ad libitum. These results suggest that meal frequency may have a minimal influence on body fat accumulation, but that a shift to a higher level of food intake may cause an increased food efficiency and greater rate of fat deposition than in rats continuously fed the higher level of intake.

High Fat Rations for Dairy Cows. Effects on Feed Intake, Milk and Fat Production, and Plasma Metabolites

High fat diets (2.9 to 10.8% ether extract in total diet dry matter) for cows in early lactation were compared in two 4×4 Latin squares. In Trial I, grain concentrate was 42% of the ration dry matter. Total diets and their ether extract (percent) were: 1) control, 3.2; 2) ground raw soybeans, 5.9; 3) hydrolyzed fat, 5.7; and 4) hydrolyzed fat, 10.8. While dry matter intake of Holsteins was lowest with Diet 2 and highest with Diet 3, milk production, fat, and protein were not different. Jerseys produced the most fat-corrected milk per unit metabolic body size on Diet 4.In Trial II, two concentrations of total diet ether extract and crude protein were arranged factorially in isoenergetic diets. Ether extract (percent) and crude protein (percent) were, respectively: 1) 3.3, 13.6; 2) 2.9, 15.9; 3) 5.9, 13.5; and 4) 6.8, 16.3. In Diets 1 and 2, grain was 50% of dry matter fed; in Diets 3 and 4, grain was 33% of dry matter fed. Dry matter intake and milk production were not different among diets. Mean milk fat (percent) of low and high fat diets was 2.7 and 3.4. Consequently, 4% fat-corrected milk was higher with high fat diets.In 32 digestion trials, high fat diets increased digestibility of ether extract and did not reduce digestibility of any other nutrient. In some instances fat increased digestibility of crude protein but not nitrogen balance. Digestibility of acid detergent fiber was increased nonsignificantly.In Trial I, Diet 2 decreased rumen acetate to propionate ratio; in Trial II, the high grain (low fat) rations decreased acetate to propionate ratio and milk fat percent and increased body weight gain.Fat increased total lipid of plasma in Trial II but not in Trial I. Triglycerides and nonesterified fatty acids were increased by fat in both trials. Glucose was not affected by fat in either trial. Rumen ammonia and plasma urea-nitrogen were increased but amino acids of plasma were unchanged by high protein diets in Trial II.Seven to eight percent fat can be included in lactation total diets to 1) increase diet energy density or 2) increase the forage to concentrate ratio to maintain milk fat percent, without negative effects on digestibility.

Relative rates of gastric emptying of glucose vs. fat in rats fed nonliquid meals.

Sprague-Dawley rats were briefly starved, fed various test meals, and killed at measured intervals, and the average fractional emptying (disappearance from stomach) rates for glucose (Kgl) and for fat (Kfat) were determined. The Kgl/Kfat ratio was calculated as a measure of the degree to which the stomach emptied glucose preferentially to fat. The size of the meal affected this ratio, which was 7.6 for a small (0.5 g) meal and 2.4 for a large (2.0 g) meal of a nutritionally complete diet. When test meals contained one of two levels of fat (0.4 and 0.1 g) and of glucose (1.2 and 0.3 g), the high level of fat depressed Kgl and Kgl/Kfat, whereas the high level of glucose depressed Kgl and particularly Kfat and, therefore, raised Kgl/Kfat. Kgl/Kfat was also affected by strain of rat and was reduced almost to 1.0 by mixing the meal into a viscous gel of xanthan gum. In the absence of this gel, the percentage of water existing in stomach contents shortly after the test meals varied between 53 and 79% and was suspected of influencing Kgl/Kfat.

Effect of 6-hydroxydopamine and alpha-methyltyrosine on brown adipose tissue of infant rats.

A single-dose administration of 6-hydroxydopamine (50 mg/kg body weight, sc) to infant rats resulted in an enlargement, higher fresh weight, markedly elevated lipid content, and higher total protein content of their interscapular and cervical brown adipose tissue. The protein kinase (EC 2.7.1.37) activation ratio in the tissue was decreased as was the phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity. Fatty acid synthetase, on the other hand, showed an increased activity. These changes commenced as soon as 24 h after the administration of the drug, were fully developed 2-4 days later, and persisted for at least 14 days. The results are in line with the assumption that 6-hydroxydopamine administration causes chemical sympathectomy of brown adipose tissue. This is further supported by the fact that treatment with alpha-methyltyrosine, which is known to competively inhibit norepinephrine systhesis, results in similar changes in brown fat of infant rats. Hence it seems that 6-hydroxydopamine administration offers a simple and inexpensive experimental model for studies of the role norepinephrine-mediated sympathetic nervous system in brown tissue function and development.

Effect of dam's diet on PCB accumulation in nursing Osborne Mendel pups.

Upon parturition, dams were fed high fat or high carbohydrate diets to which 1, 10, and 30 ppm of Aroclor 1254 were added to study the effect of diet on fat and PCB accumulation in nursing pups. The percentage of body fat in the carcasses of 0, 8, and 16 day old pups ranged from 2.2 to 18.2% and from 1.2 to 12.0% for animals suckled by dams fed high fat and high carbohydrate rations, respectively. Accumulation of Aroclor 1254 expressed as ppm wet weight or as total PCB's per pup was similar for animals nursed by dams fed either the high fat or high carbohydrate ration, but pups from dams fed a high carbohydrate ration also had significantly less body fat. Therefore, transfer of PCBs via the milk appears to be more a function of the amounts of PCB's consumed by the dam than the diet's ability to increase the percentage of body fat in the pups.

Surgical reduction of adipose tissue in the male Sprague-Dawley rat

The lipostatic theory of regulation of adipose tissue mass was tested by a method for surgical reduction (adipectomy) of 24% of the total body fat of nonobese adult Sprague-Dawley rats, as judged from carcass analyses. The reduction persisted during an observation period of 12 wk without any evidence of altered food intake, weight gain, or compensatory hypertrophy or hyperplasia of adipose tissue compared with sham-operated controls. No changes were found in serum free fatty acids, glycerol, triglycerides, cholesterol, or insulin between adipectomized and control animals, implying an intact quantitative function of the remaining adipose tissue. It is concluded that the size of the adipocytes rather than the number is important for a presumed lipostatic regulation of adipose tissue mass in the adult male Sprague-Dawley rat.

Effect of Gemfibrozil in vitro on Fat-mobilizing Lipolysis in Human Adipose Tissue

Fat-mobilizing lipolysis was studied in rat and human adipose tissue during incubation in vitro by following the release of glycerol into the incubation medium. Gemfibrozil as well as clofibrate consistently and readily inhibited basal as well as noradrenaline-stimulated fat-mobilizing lipolysis in rat fat. With human adipose tissue no effect was observed with gemfibrozil and clofibrate on basal lipolysis. This may be due to the comparatively low rate of the nonstimulated fat-mobilizing lipolysis in human tissue incubated in vitro. When lipolysis was stimulated with noradrenaline as well as isoprenaline, however, both gemfibrozil and clofibrate significantly reduced the fat-mobilizing lipolysis. This inhibition of lipolysis was however not observed in all studies. When lipolysis had been stimulated with theophylline, no inhibition of lipolysis was obtained with either compound. The possibility that reduced fat-mobilizing lipolysis in adipose tissue may cause a lowering of plasma triglycerides by reducing the flow of FFA to the liver is discussed in some detail. It is also suggested that inhibition of lipolysis may be accompanied by increased activity of lipoprotein lipase as well as an increase in the FIAT process. However, the pharmacological implication of the above-mentioned findings, particularly for gemfibrozil, must await further studies, as fairly large doses, around 1 mg/ml of incubation medium, were needed to obtain inhibition of fat-mobilizing lipolysis.

Effect of glucagon and its 1–23 peptide fragment on lipolysis in isolated rat and human fat cells

Effect of glucagon and its 1–23 peptide fragment on lipolysis in isolated rat and human fat cells

Evaluation of the Antilipolytic Action of Clomiphene In Vitro

Clomiphene (10(-3) - 10(-2) M) in a dose-dependent manner inhibited the lypolytic response of isolated rat epididymal adipose tissue and fat cells to epinephrine, ACTH, and dibutyryl-cyclic AMP. Furthermore, it reduced the non-hormonally stimulated activity of a crude preparation of lipase from epididymal adipose tissue. The accumulation of cyclic AMP produced by epinephrine in fat cells was not prevented by clomiphene at a concentration causing antilipolytic activity. It is concluded from these results that clomiphene unlike most other antilipolytic drugs exerts its antilipolytic effect by an inhibition of the lipase rather than by inhibition of adenylcyclase.