Ruth Ellen Johnson

Nutritional properties of the triglycerides of saturated fatty acids of medium chain-length

SummaryThe influence of a purified rat diet containing 20 or 33% of the saturated medium chain-length triglycerides (MCT) with and without linoleic acid supplements on growth, caloric requirements for weight maintenance and weight increase, fertility, lactation performance, and serum cholesterol levels was compared with that of similar diets containing lard, coconut oil, or no fat.Among male rats maintained on diets containing 20% lard or 20% MCT and .09% linoleic acid for 18 months no differences were observed between the groups other than the depressed body weight and lowered serum cholesterol levels of the group fed MCT. When groups of male rats were kept at constant weight by the daily restricted feeding of diets containing lard, MCT, or coconut oil or no fat plus 2% linoleic acid, the weight-maintenance requirements of the group fed MCT were higher than of those on lard and coconut oil and even somewhat higher than the requirements of the animals fed the fat-free diet. The requirements for weight increase over those for maintenance were 0.9 g. per gram increase for all diets. Additional linoleic acid in the MCT diet decreased the weight and maintenance differences between groups fed MCT and lard.The lactation performance of mothers on MCT plus .09% linoleic acid was poor. The second generation animals initially showed signs of more severe linoleic acid deficiency which however disaappeared without linoleic acid supplements.Some cholesterol levels of animals on MCT were significantly below those of groups on lard. Addition of linoleic acid to the MCT diet did not change the results.

Biological effects of the polymeric residues isolated from autoxidized fats

SummaryThere is increasing evidence that the abnormal nutritional properties of highly autoxidized fats are related to the polymers which develop during autoxidation. Lard and cottonseed oil were aerated at 95°C. for 200 hrs. and molecularly distilled; and the residue fractions, non-volatile at 275 to 300°C., were studied.Diets containing 20% of autoxidatively produced polymeric residue, fed to albino rats, led to diarrhea and rapid death, but when this residue was reduced to 10%, most of the animals were gradually able to tolerate it. At the 4 or 7% level it was well tolerated, but growth was reduced. There were no distinctive histological lesions, and withdrawal of the polymer permitted immediate realimentation without evidence of subsequent injuries.The polymeric residue from autoxidized cottonseed oil exerted a greater growth-depressant effect than that from lard, and the latter, more than that from a hydrogenated vegetable oil used for deep-fat frying for 80 hrs. at 190°C. Addition of fresh fat to the polymeric residues decreased their growth-depressant effect.When rats were fed a measured amount of diet sufficient to maintain their weight, the caloric requirement necessary for weight maintenance gradually decreased. When the dietary fat source consisted of polymeric residue to the extent of 4 to 10%, the caloric requirement for weight maintenance decreased relatively little, if at all. The polymeric residue from autoxidized lard was, in this respect, as effective as that from autoxidized cottonseed oil.

A long-term nutritional study with fresh and mildly oxidized vegetable and animal fats

Fresh and oxidized cotton seed oil (CO) olive oil (OO), chicken fat (CF) and beef fat (BF) were fed to male weanling rats for 33 to 108 weeks. Groups fed oxidized fats except OO showed a higher death rate than those fed the corresponding fresh fats. Groups fed oxidized CO and BF had the highest death rate. Histological studies of animals dying from natural causes showed more pronounced cardiac lesions in the animals fed oxidized CO. Serum, liver and brain cholesterol levels were not influenced by oxidized fats. Fatty acid composition of depot fats and of heart and liver lipids did not show significant differences between groups fed fresh and the corresponding oxidized fats.

Exacerbation of heart and liver lesions in rats by feeding of various mildly oxidized fats

Groups of 40 male Charles River rats were fed diets containing cottonseed oil, olive oil, corn oil, soybean oil, coconut oil, chicken fat, beef fat, butter oil, lard and saturated medium chain triglycerides. The fats were fed fresh and after 40 hr aeration at 60 C, which hardly changed peroxide values. In addition, fresh and aerated soybean oil and lard were fed to W/Fu rats. Body weights and life span were significantly influenced by the kind of fat fed, but not by aeration. Many hearts exhibited unspecific focal myocarditis and focal fibrosis. The latter was graded in a blind test, which revealed highly significant differences in the incidence of severe lesions; those fed corn oil had the most, followed by cottonseed oil, soybean oil, olive oil, beef fat, saturated medium chain triglycerides, butter, chicken fat and lard, in that order. Feeding of aerated fat resulted in an increased incidence with six of the eight fats. The W/Fu rats had lower incidences, but those fed soybean oil had more than those fed lard, and aeration led to a higher incidence. Some heart sections stained with Light Green SF Yellowish revealed areas of muscle fibrils that did not accept the stain, probably as a consequence of cellular damage. Higher incidences of this lesion were associated with the same fats as was severe fibrosis, and feeding of aerated fats led to higher incidences. Many livers revealed marked proliferation of bile ducts. The groups fed cottonseed, soybean, olive and corn oils had higher incidences of severe lesions, and feeding of the oxidized oils led to still higher incidences. None of the results appeared to be associated with the fatty acid composition of the fats, which suggested that these long term effects may have been due to minor constituents in the individual fats.

Dietary protein, fat, and minerals in nephrocalcinosis in female rats

Young female rats fed semipurified diets containing casein or a soy protein isolate had extensive nephrocalcinosis at the junction between the outer and inner stripe of the outer medullary zone after 5 wk on the diets, whereas rats fed a diet containing a lactalbumin concentrate did not. Although the percentages of actual protein and of total ash were similar in all three diets, the concentrations of individual minerals were not, owing to methods used in isolating the proteins. Comparison of the individual mineral contents of these diets with those in other laboratories as compiled from the literature suggested that factors other than minerals, including protein, are also implicated. Dietary fat appeared to be another such factor in a series of experiments in which saturated medium-chain triglycerides and corn oil were included in diets containing soy protein isolate. Although these diets had identical mineral compositions, the rats fed medium-chain triglycerides had less severe lesions.

Influence of feeding fractionated esters of autoxidized lard and cottonseed oil on growth, thirst, organ weights, and liver lipids of rats

SummaryLard and cottonseed oil which had been autoxidized at about 100°C. for 210 hrs. were fractionated by a technique involving molecular distillation, conversion to ethyl esters, urea-complex formation, and redistillation. The ethyl esters were then fed to rats for three weeks at a level of 8% in a purified diet. Growth, water intake, organ weights, total liver lipids, and serum and liver cholesterol levels were determined. Groups fed 8% lard served as controls.Growth was severely depressed by the residue fractions of the urea-complex- and noncomplex-forming portions of the original molecular distillates. Of the three fractions from the original molecular distillation residues, the dimeric and polymeric fractions were the most active. The relative liver and kidney weights were usually increased by feeding the growth-depressing fractions. However there were a number of exceptions indicating more specific effects from some of the fractions. Water intakes were lower with the fractions derived from the original molecular distillates than with those from the original molecular distillation residues. Testicular fat body weights suggested that feeding of autoxidized CSO fractions led to less neutral fat deposition than feeding of corresponding autoxidized lard fractions. Dry weight of the enlarged livers was higher, and the total lipid lower than of the control livers. Total liver cholesterol was higher in animals with smaller livers, but there was no difference in the cholesterol content of the total liver lipids. Serum cholesterol levels were lower in animals with large livers.Further study of those fractions having pharmacological properties is suggested.

Electron microscope studies of the absorption of lipids: II. Medium chain saturated triglycerides☆

Abstract The absorption of saturated long chain triglycerides across the jejunal epithelium of the rat has been studied by electron microscope. The absence of lipid droplets in the microvilli, the terminal web and the absence of phagocytosis of lipid droplets at the cell surface is consistent with the concept that the majority of the triglyceride is hydrolyzed in the intestinal lumen, is transferred across the cell surface as fatty acids, glycerol, and monoglyceride. Visible lipid first appears in the channels of the endoplasmic reticulum, probably as a triglyceride resynthesized from the absorbed fatty acids. As with the saturated medium chain acids, the long chain acids also produced a negative image in the electron micrographs due to the absence of the double bonds necessary to reduce osmium. The chylomicrons developed by the intestinal epithelial cells are ellipsoidal or elongated in comparison to those formed with MCT and unsaturated fatty acids, which are spherical. These unstained chylomicrons were visible only because of the formation of a tiny “membrane” immediately investing each chylomicron. These “membranes” have been interpreted as lipoprotein or phospholipid acquired by the chylomicron in its transit through the epithelial cell. One of the major differences in the absorption of LCT in comparison with other lipids is the development of large cleft-like deposits of this lipid within the cytoplasm of the epithelial cells. This ultimately causes damage to the cell as evidenced by the destruction of mitochondria and the development of “myelin” forms within the cytoplasm of some of the cells.

Interrelations of linoleic acid with medium-chain and long-chain saturated triglycerides

Summary1.Effects of medium-chain (C6–C12) saturated triglycerides (MCT) and long-chain (C14–C18) saturated triglycerides (LCT) with and without linoleic acid (LA) supplementation were studied on rats fed purified diets2.With 2% linoleic acid rats fed MCT and LCT grew somewhat better than those on a low-fat diet with the same supplement. Without linoleic acid those fed MCT grew better, and those fed LCT grew worse than those on the corresponding low-fat diet. MCT seemed to decrease, and LCT to increase linoleic acid requirements.3.In survival studies 14 out of 18 rats fed 20% MCT were alive after 2 years; of their controls fed 20% lard, 10 out of 19 survived.4.Reproduction studies in females gave equally poor results on unsupplemented low-fat, MCT, and LCT diets regarding implantation, birth weight, and survival rate. The weaning weights of the young on MCT were however the highest. With 2% LA weaning weights were equally high with LCT and MCT but lower with low-fat diet.5.In animals fed low-fat diets not supplemented with LA, low serum cholesterol was associated with high liver cholesterol. With MCT, serum values were higher and liver values were significantly lower. With unsupplemented LCT, serum and liver values were high. When the three diets were supplemented with 2% LA, there were no longer any differences in the serum levels and in the liver levels. Whether ar not the presence of some oleate in the MCT and LCT influenced the cholesterol results is not certain.6.The differences in the effects of MCT and LCT are discussed.

Nutritional properties of medium-chain triglycerides

The biological effects of MCT (medium-chain triglycerides) differed from those of conventional fats, and certain of these suggested examination of the fatty acid composition and triglyceride structure of the adipose tissues and other organs of rats which were fed medium- or long-chain triglyceride mixtures with two levels of linoleic acid. Fatty acid compositions and TG patterns varied with the tissue, with the dietary fat, and with the level of linoleate in the diet. Increasing the latter resulted in the deposition of more linoleate at the expense of oleate and in the deposition of more of the dietary fatty acids. The percentage of completely saturated triglyc-erides (S3), in adipose tissue with the higher linoleate supplement in the rats fed MCT, decreased in those fed LCT and was unchanged in the controls fed a fat-free diet. The increased deposition of the dietary fatty acids was more pronounced in the S3 band.

Differences in effects of dietary fats on survival rate and development of neoplastic and other diseases in rats

SummaryGroups of 40 male rats of the Charles River CD strain were fed a purified complete diet containing 20% of cottonseed oil, olive oil, corn oil, soybean oil, chicken fat, beef fat, butter, lard, or medium chain, saturated triglycerides (MCT). Except for the latter, the fats were fed either fresh or after 40 hours of aeration at 60 °C. The rats were observed for weight gain, life span, and terminal pathological changes. There were significant differences in survival rate, occurrence of malignant non-endocrine tumors, and degenerative and inflammatory diseases, such as the high incidence of chloromatous leukemias among the rats fed chicken fat, or the severe myocardial lesions among the groups fed vegetable oils. Inasmuch as the results could not be accounted for by the usual properties of triglycerides, it was concluded that minor constituents in fats play an important part in their individual nutritional effects. It was speculated that the processing of some fats may have to be changed.ZusammenfassungGruppen von vierzig Rattenmännchen der „Charles River CD“ Zucht wurde eine hochgereinigte Nahrung verabreicht, die 20% Baumwollsamenöl, Olivenöl, Maisöl, Soyaöl, Hühnerfett, Rindsfett, Schweineschmalz oder gesättigte Triglyceride mittlerer Kettenlänge (MCT) enthielt. MCT wurde ohne Vorbehandlung, die anderen Fette entweder frisch oder nach vierzig stündigem Luftdurchblasen bei 60 °C verwendet. Gewicht, Überlebenszeit und histopathologische Veränderungen wurden beobachtet. Signifikante Unterschiede zwischen den Gruppen wurden beobachtet. Es erschien z. B. beachtenswert, daß die mit Hühnerfett ernährten Tiere eine erhöhte Zahl von myeloischen Leukaemien aufwiesen und daß die mit Pflanzenfetten ernährten Tiere besonders ausgeprägte myokardiale Veränderungen hatten. Da die Resultate nicht durch die Eigenschaften der Triglyceride erklärt werden konnten, muß man annehmen, daß Substanzen in der Nicht-Triglyceridefraktion von größter Bedeutung für die biologischen Unterschiede dieser Fette sind. Verbesserte Verfahren zur Herstellung von Nahrungsfetten sind zu empfehlen.