Triglyceride sub-classes of dog plasma and organs

Lipids were extracted from liver, kidney, myocardium, skeletal muscle, arterial and femoral venous plasma. Triglycerides were purified by thin layer chromatography and the double bond subclasses separated by silver nitrate silica gel H thin layer plates. Gas chromatography was used to delineate the fatty acid composition of each sub-class as well as the carbon number of the purified triglyceride from each site. The major double bond sub-class was O11 (O,saturated fatty acid; 1,one double bond; 2,two double bonds). The plasma values were highest in 001 and 002. All sites had quite uniform 112 while plasma had the lowest 012. The percentage of all saturated fatty acids in a band was summed and equated to 100% and the fatty acid percentage recalculated on this basis. The saturated fatty acid distribution in myocardium and skeletal muscle was highest in myristate in the third 001 sub-class and liver and plasma had the highest stearate in the second 001 band. The palmitate was similar in most bands. Every sample, except the subcutaneous adipose tissue, had a maximum triglyceride content of carbon number 52 (the carbon number represented the sum of all carbon atoms in the fatty acids present in a molecule). The liver and subcutaneous adipose tissue triglyceride carbon number 52 and 54 were approximately equal. The liver exhibited the largest 56.     

Glycerokinase in human adipose tissue

The presence of glycerokinase has been demonstrated in human omental and subcutaneous adipose tissue. The enzyme reaction showed a linear time course for 5 min at 30 C and pH optima at pH 7.6 and 9.0. Saturation of the enzyme was observed at 1.8 mM adenosine triphosphate (ATP) and the double reciprocal plot of activity vs. ATP concentration was nonlinear giving two apparent Km values of 0.094 and 0.518 mM. The apparent Km for glycerol, 0.112 mM, was obtained from a linear double reciprocal plot, and the enzyme was saturated at about 0.4 mM glycerol. The activity of glycerokinase in human adipose tissue excised under general anaesthesia was low and was unrelated to adipose cell size or the degree of obesity of the subject from whom the fat was obtained.     

Bioenergenetics of brown adipose tissue 1

Examination of the effect of 2,4-dinitrophenol (DNP) in vivo on the brown adipose tissue of cold-exposed rats as well as the effect of DNP and dicumarol in vitro, indicates that brown fat does possess a functional electron transport-coupled phosphorylating system. Moreover, the fact that a norepinephrineinduced thermogenic response (in vivo) can be elicited from the brown fat after DNP administration implies that the effect of norepinephrine (NE) is not primarily due to stimulation of an adenosine triphosphatase system. Furthermore, since the magnitude of the NE-stimulated temperature increase is not diminished by prior treatment with DNP, it appears that the effect of NE is not achieved through any significant degree of uncoupling by the released fatty acids. Alternatively, our data suggest that under basal conditions (i.e., when the animal is not stimulated by cold stress or NE) the heat production (oxygen consumption) of the brown fat is limited by the availability of substrate rather than ADP. Conversely, it is proposed that under states of cold stress or NE infusion the thermogenic effect is induced through stimulation of lipolysis and consequent enhancement of substrate accessible for mitochondrial oxidation. One of nine papers to be published from the Symposium “Brown Adipose Tissue,” presented at the AOCS-AACC Joint Meeting, March 1968.     

Control of metabolism in brown adipose tissue

Cells and mitochondria were isolated from brown adipose tissue of the adult hamster. Isolated mitochondria did not show respiratory control. Reversed electron transport was demonstrated and the oxidation rates of various substrates were compared. α-Glycerophosphate gave the highest oxidative rate with isolated mitochondria. The low basal respiration of isolated brown fat cells could be stimulated by catecholamines, oleate, succinate,a-glycerol phosphate and uncoupling agents. Only norepinephrine or oleate induced respiration was sensitive to inhibition by oligomycin, but this inhibition could not be released by uncoupling agents. Neither atractyloside nor (+) decanoylcarnitine were found to affect respiration, suggesting that mitochondrial nucleotide exchange is slow and that fatty acid oxidation might be carnitine independent. In resting brown fat cells, ATP amounts to 75% of the total adenine nucleotides. NE or oleate caused a small decrease of ATP and a corresponding increase of ADP. Oligomycin caused a partial depletion of ATP content, but subsequent NE addition increased ATP back to control values. This effect was abolished by arsenite. Similarly, uncoupling agents diminished the ATP level which was increased only slightly by NE. Arsenite alone decreased ATP levels to a small extent but a rapid depletion occurred upon subsequent NE addition while respiration was inhibited. Thus, substrate level phosphorylation may be the major energy producing reaction for the generation of ATP and GTP for the activation of fatty acids. Norepinephrine addition to brown fat cells caused an oxidation of pyridine nucleotides, a reduction of flavoproteins and an oxidation of cytochrome b. In constras, succinate produced a reduction of all the components of the respiratory chain. The bioenergetic basis of thermogenesis in brown fat is its high respiratory rate. The rapid respiration induced by norepinephrine or fatty acids appears to be characterized by a low yeild of ATP from oxidative phosphorylation and may be controlled by fatty acid mediated release of energy coupling, possibly by an indirect mechanism. One of nine papers to be published from the Symposium “Brown Adipose Tissue,” presented at the AOCS-AACC Joint Meeting, Washington, D. C., March 1968. This work was done during the tenure of an Established Investigatorship from the American Heart Association.     

Positional specificity of adipose tissue lipoprotein lipase

The positional specificity of preparations of lipoprotein lipase derived from rat epididymal adipose tissue was investigated. The enzyme preparations were a crude extract of acetone powder of the whole tissue, partially purified lipoprotein lipase fractions a and b separated by gel chromatography from such an extract, and lipoprotein lipase activity eluted from adipose tissue into a medium by incubation with heparin in vitro. The enzyme preparations were incubated with triglyceride substrate labeled with³H in the glycerol moiety and with¹⁴C in the fatty acid esterified to the 2 position of the glycerol. The reaction products were separated by thin layer chromatography. All preparations preferentially hydrolyzed the 1(3) ester bonds of the tri- and diglycerides, indicating that, like lipoprotein lipase from other sources, the adipose tissue enzyme has a specificity for the 1(3) position.     

Steroids in bovine muscle and adipose tissue

Thin layer and gas liquid chromatography, (GLC) were employed as complementary techniques to investigate naturally-occurring steroids in the unsaponifiable matter of bovine muscle and adipose tissue. Three GLC liquid phases, differing in selective partition properties, were used to effectively identify unknown steroids. The results indicate that cholesterol and minor amounts of desmosterol, Δ⁷-cholestenol, lanosterol, dihydrolanosterol, dehydromethostenol, Δ⁸-methostenol, Δ⁷-methostenol, cholestanol and possibly ergosterol were present in the bovine tissues. The minor steroids, with the exception of cholestanol and ergosterol, are steroid precursors in cholesterol biosynthesis. Common hormonal steroids were not found in the unsaponifiables of the tissues.     

Effect of lactation on lipolysis in rat adipose tissue

The concentrations of nonesterified fatty acids and glycerol in rat parametrial adipose tissue increased at peak lactation. Adipose tissue from lactating rats showed higher rates of release of nonesterified fatty acids and glycerol when incubated in vitro than did tissue from nonlactating rats, but there was a substantial increase in the esterification of fatty acids during involution. These results support earlier evidence that fat reserves were mobilized during lactation.     

Estimate of fatty acid turnover in porcine adipose tissue

Fatty acid turnover in the domestic pig was estimated by measuring the half-life of linolenic acid depletion in adipose tissue depots which had been made abnormally high in linolenic acid by feeding large quantities of linseed oil. The measured half-life of linolenate in 8- to 12-month-old pigs was 300 days. The apparent half-life of linolenate in muscle lipids was less than that of subcutaneous backfat.     

Effect of dietary fats on ovine adipose tissue metabolism

The effects of different dietary fats on ovine adipose tissue metabolism have been investigated. Six-month old sheep were fed for 6 weeks a control diet or diets supplemented with either tallow or a mixture of sunflower seed oil and soybean oil, treated to protect the fats from hydrolysis and hydrogenation in the rumen, or with maize oil. The rates of fatty acid, glyceride glycerol, and CO₂ formation were measured in perirenal and subcutaneous adipose tissue slices by following the incorporation of either¹⁴C from labeled acetate or glucose, or³H from tritiated water into the appropriate product. Feeding protected tallow or maize oil but not protected sunflower seed oil plus soybean oil resulted in reduced rates of fatty acid biosynthesis in both perirenal and subcutaneous adipose tissue slices and CO₂ formation in perirenal adipose tissue. Feeding the fat-supplemented diets had no effect on the rate of glyceride glycerol formation. The fat-supplemented diets also resulted in reduced activities of various enzymes, thought to be involved in lipogenesis, measured in 105,000× g supernatant fractions from adipose tissue homogenates. The results suggested that ovine adipose tissue lipogenesis is sensitive to both the amount and the nature of dietary fat.     

Occurrence of ethanolamine- and choline-containing plasmalogens in adipose tissue

Analysis of phospholipids in porcine, bovine and rat adipose tissue revealed a relatively high level of plasmalogens (O-alk-1-enyl lipids). About 50% of the ethanolamine phospholipids in the pig and beef samples consisted of alk-1-enylacylglycerophosphorylethanolamine, and the corresponding value for the rat sample was near 35%. In the ethanolamine and choline phospholipid fractions, theO-alk-1-enyl moieties were almost exclusively 16∶0, 18∶0 and 18∶1, whereas the acyl moieties had chain lengths ranging from 16 to 22 carbon atoms with a high degree of unsaturation.     

Animal endogenous triglycerides: I. Swine adipose tissue

The objective of this study was to define the composition of endogenous glycerides of swine adipose tissues as a basis for further studies on the influences of diet and other environmental factors. It was also hoped that the endogenous triglyceride composition might suggest a fresh approach to the problem of the biosynthetic pathway of natural triglyceride mixtures. Swine were fed a fat-free diet from the age of 17 days to 5 months, and the triglycerides of their mesenteric, perirenal and inner and outer back adipose tissues analyzed by silver ion thin layer chromatography and gas liquid chromatography. Four silver ion fractions were found, S₃, S₂M, SM₂ and M₃ (S, saturated; M, monounsaturated fatty acids). Corresponding fractions from different adipose tissues had identical fatty acid composition. The fatty acid compositions of the 2 position of the fractions were also identical. However, the fatty acid composition of the unfractionated triglycerides varied from tissue to tissue. It is concluded therefore, that the various adipose tissues of swine contain the same triglycerides in varying concentrations. Stearic and oleic acids were located mainly in the combined 1 and 3 positions. Myristic, palmitoleic and palmitic were in the 2 position, with almost 90% of the saturated acids being palmitic. This specific distribution of the major fatty acids can explain the marked simplicity of swine endogenous triglycerides.     

Some aspects of fatty acid metabolism in brown adipose tissue

The action of catecholamines on white and brown adipose tissue is compared. The available evidence indicates that lipolysis is initiated in both tissues by hormonal action. There are, however, some differences in the behavior of the lipolytic process in the two tissues in their response to theophylline, nicotinic acid and insulin which remain unexplained. It would appear that the release of free fatty acids triggers the stimulation of O₂ consumption in both tissues. In brown adipose tissue no evidence has been obtained to indicate that the increased O₂ consumption is geared to the production of ATP for the purpose of reesterification of the released free fatty acids, as is the case in white adipose tissue. One of nine papers to be published from the Symposium “Brown Adipose Tissue,” presented at the AOCS-AACC Joint Meeting, Washington, D.C., March 1968.     

Structural relationships between glycerides of pig serum and adipose tissue

Structural analyses have been performed on the triacylglycerols and phosphoglycerides isolated from adipose tissue, serum chylomicrons, and serum lipoproteins from pigs. The triacylglycerols from adipose tissue contained mainly palmitate esterified at the 2 position of the glycerol moiety, whereas those from the serum had predominately     

Estimating Thermodynamic Properties of Pure Triglyceride Systems Using the Triglyceride Property Calculator

To date, the most comprehensive model for predicting thermodynamic properties of pure triglycerides was presented by Wesdorp in “Liquid-multiple solid phase equilibria in fats: theory and experiments” (1990). In this paper, we present (1) corrections to the published model, as well as (2) a software implementation of the model for numerical assessment. The software tool, Triglyceride Property Calculator (TPC), uses a semi-empirical model to estimate the enthalpy of fusion and melting temperature for a given triglyceride based on its molecular composition and polymorphic form. These estimates are compared to experimentally collected data when available. The web application is available at http://www.crcfoodandhealth.com (under research tools) and through the AOCS Lipid Library. The quality of estimates is characterized according to defined counting metrics and presented for TAG subcategories. Additionally, the extrapolative value of the TPC is assessed by checking for consistency with underlying thermodynamic constraints. The current TPC implementation is effective in describing experimentally collected melting point data, with greater than 91% of the fitted values falling within 10% of the actual data. The TPC is also very good at describing collected enthalpy data. The underlying semi-empirical model and parameter set perform well in ensuring enthalpy predictions are thermodynamically consistent, however, extrapolated melting temperatures appear unreliable. Developing models and parameter sets that ensure thermodynamic consistency is a priority with future TPC iterations.     

Effects of parathion on lipolysis in isolated rat adipose tissue cells

The effects of the pesticide, Parathion (0,0-diethyl 0-p-nitrophenyl thiophosphate) and various lipolytic and antilipolytic agents on lipolysis in adipose tissue were studied with isolated fat cells from rat epididymal fat pads. Lipolysis was measured as the release of free fatty acids into an albumin-bicarbonate medium. Parathion depressed lipolysis in a linear manner at concentrations ranging from 10⁻⁹ to 10⁻³M. At a concentration of 10⁻⁵M, Parathion depressed the lipolytic response to epinephrine (0.15 μg/ml) and slightly to cyclic 3′,5′-adenosine monophosphate (10⁻³ M) and enhanced the antilipolytic response to nicotinic acid (33 μM). It is possible that Parathion may interfere with adenyl cyclase activity. Scientific Contribution No. 400. Agricultural Experiment Station, University of Connecticut, Storrs, Conn. 06268.     

Lipids and lipogenic enzymes in adipose tissue of castrated male goats

Male goats (“Criolla Argentina” breed), castrated at 45 days of age, showed altered lipid metabolism 180 days after castration as compared to control goats. Subcutaneous, perirenal and omental adipose tissues of castrated goats showed increases in fatty acid synthetase, glucose-6-phosphate dehydrogenase and NADP-isocitrate dehydrogenase activities. Castration increased the amount of total lipids and triglycerides, but did not modify the amount of cholesterol, phospholipid and protein in the three types of adipose tissue. The incorporation of [1-¹⁴C]acetate into fatty acids of subcutaneous and perirenal adipose tissue was increased in castrated goats in relation to noncastrated goats. Our results suggest that removal of gonadal steroids increases significantly the rate of lipogenesis in adipose tissue of male goats.