Large Fat Cells Research Articles

Studies on the compartmentation of lipid in adipose cells. II. Cholesterol accumulation and distribution in adipose tissue components

Adipose tissue was shown to contain 0.6-1.6 mg of cholesterol per gram wet weight. When expressed per unit of protein or organ mass, fat tissue contains more cholesterol than most other organs or membranes. The cholesterol content of fat tissue increased with the age and weight of the rat. Over 95% of adipose tissue sterols was cholesterol, and most of it was free. In young (150-165 g) rats two-thirds of fat tissue cholesterol was in collagenase-derived adipocytes while in older rats (450-480 g) 90% of fat tissue cholesterol was in adipocytes and the remainder was in stromal-vascular elements. Age-related differences in subcellular cholesterol distribution were also observed. The cholesterol/phospholipid molar ratios of purified plasma membrane fractions from small and large fat cells were identical (0.22-0.25), thus resembling muscle and liver membranes. 7.5 days after intravenous administration of [4-(14)C]cholesterol the specific activity of adipose cholesterol exceeded that of plasma cholesterol. At 28 days the specific activity of adipose and muscle cholesterol exceeded that of plasma three- to fivefold. The t((1/2)) disappearance of adipose tissue cholesterol was approximately 27 days, which is consistent with its function as a slowly turning over storage pool. Thus, fat tissue is a major cholesterol storage organ. This may well account for the marked expansion of the slowly exchangeable cholesterol pool (pool B) observed in obesity.

Carbohydrate-stimulated fatty acid synthesis de novo in human adipose tissue of different cellular types.

Abstract. Fatty acid (FA) synthesis in vitro by human adipose tissue has been determined as glucose incorporation into FA by slices and as the overall enzyme capacity for incorporation of acetyl units into FA from acetate and citrate by an optimal cytoplasmic assay system. Twelve subjects with normal, hypertrophic, hyperplastic or combined hypertrophic‐hyperplastic adipose tissue were examined during basal, weight stable conditions and after 3 and 22 days on a high‐carbohydrate low‐fat chemically defined diet (Vivasorb®) administered in amounts resulting in a moderately negative energy balance. Incorporations obtained with the cytoplasmic assay were several times higher than those with the whole cell technique. During carbohydrate feeding FA synthesis increased 3 and 11 times, respectively, as measured with the subcellular and the whole cell techniques. However, FA synthesis de novo was of little quantitative importance in human adipose tissue even during stimulated conditions. Expressed per g adipose tissue triglyceride (TG), there were no differences in FA synthesis between the four cellular groups before or during high‐carbohydrate feeding. Expressed per cell, large fat cells demonstrated a higher enzyme capacity for FA synthesis than did cells of normal size. The correlation between fat cell size and enzyme capacity for FA synthesis increased during the course of high‐carbohydrate feeding. During but not before high‐carbohydrate feeding there were several correlations between different whole cell and subcellular activities of adipose tissue and also strong correlations between FA synthesis in adipose tissue and serum TG. The latter correlation was most likely not related to a direct dependence between the two factors. Contrary to earlier reports, this investigation indicates the presence of ATP citrate lyase [E.C.4.1.3.8] in human adipose tissue and demonstrates that, in vitro, the enzyme capacity for citrate incorporation is at least as large as the capacity for acetate incorporation into FA if optima! conditions are used for both precursors.

Cellularity in different regions of adipose tissue in young men and women

Body cell mass, body fat, and total number of fat cells were determined in young men and women. In addition, regional determinations of adipose tissue thickness, fat cell size, and fat cell number were also performed. The individuals studied were 11 male and 12 female medical students with a mean age of 22 yr. In order to avoid deviations from ideal body weights, the individuals were preselected by using anthropometric standards. The women had more body fat than the men, which was due to an increase in the total number of fat cells. Mean fat cell size did not differ significantly between sexes. The women had greater adipose tissue thickness than the men, which was primarily due to an increase in local fat cell number in all regions investigated (epigastric, hypogastric, femoral, and gluteal) except in the gluteal region, where the difference was mainly explained by larger fat cells in women. When expressed in per cent of maximum values, the intrasexual patterns of adipose tissue thickness and local fat cell number in different regions were similar in men and women, while the pattern concerning fat cell size was slightly different between the sexes. There were no differences between sexes in cholesterol, triglyceride, fasting blood sugar, or fasting insulin values. Middle-aged randomly selected men and women examined previously had a larger amount of body fat than the young men and women, respectively, examined in the present investigation. This difference in body fat with age was due to a larger mean fat cell size in the middle-aged populations, while there was no difference in total fat cell number.

Effects of carbohydrate feeding on blood coagulation, fibrinolysis and platelet adhesiveness — relations to serum lipids and lipoproteins

An isocaloric diet containing 93 calorie % glucose was given for 23 days to 9 obese subjects and 2 normal controls. The influence on blood coagulation, fibrinolysis and platelet function as well as serum lipids and lipoproteins were: Factor II-VII-X activity, fibrinogen dn plasminogen decreased while factor V and factor VIII, antithrombin III, a 1 antitrypsin and α 2 macroglobulin, did not change. Recalcification time of platelet-rich and platelet-poor plasma, Russel viper venom (RVV) clotting time and activated partial thromboplastin time (APTT) were shortened. No one of the factors known to influence on clotting was found to be responsible for the shortening of the clotting times. Platelet adhesiveness decreased unexpectedly. Fibrinolytic activity in plasma and in euglobulin before and after stasis of the arm did not change sifnificantly. Serum cholesterol, low density lipoproteins (LDL) and high density lipoproteins (HDL) decreased while serum triglycerides and very low density lipoproteins (VLDL) increased - the latter preferentially in the obese group with large fat cells. The reduction in HDL caused by the diet was correlated to the decrease in factor II-VII-X and fibrinogen. A strong correlation was found between LDL and platelet adhesiveness and a causal relationship may exist. According to conventional ideas the shortening of clotting times should tend to increase and the lowering of platelet adhesiveness to decrease the tendency to thrombosis. The results of the present work demonstrate the danger in drawing conclusions from studying only one factor in the complicated scheme of hemostasis.

Childhood Preventatives against Adult Heart Attacks

Childhood Preventatives against Adult Heart Attacks

The composition and metabolism in vitro of adipose tissue fat cells of different sizes.

Abstract. Fat cells of different sizes were isolated from the same sample of adipose tissue by collagenase treatment and fractionation by flotation in an isoosmolar medium. Protein, phospholipid and cholesterol increased with increasing fat cell size. Cholesterol correlated most closely with fat cell volume but phospholipid apparently with surface. Most of fat cell cholesterol was found in the triglyceride droplet, and only a smaller part in a particulate fraction from fat cells. Incorporation of labelled glucose into triglyceride increased with fat cell size, apparently in proportion to fat cell surface rather than diameter or volume. This was the case also with incorporation into fatty acids. The association between fat cell size and metabolism was present also in alloxan diabetic rats. Short term insulin deficiency thus does not abolish the increase of metabolic activity with fat cell size. Analyses of activities of selected glycolytic enzymes and of fatty acid synthesis from acetate in cell‐free systems showed a similar dependence on fat cell size, demonstrating that isotope dilution phenomena in large and small fat cells are probably not responsible. — Lipolytic activity in the basal state and after epinephrine stimulation was increased in large fat cells, which also reesterified more fatty acids than small fat cells when calculated according to the balance method. — It was concluded that larger fat cells are metabolically more active than smaller fat cells. The increase of glyceride‐glycerol labelling and of glycerol release from larger fat cells suggests an increased triglyceride turn‐over in these fat cells. Large fat cells might thus be considered as an active metabolic sub‐compartment of adipose tissue.

Effects of norepinephrine, theophylline and dibutyryl cyclic AMP on in vitro lipolysis of human adipose tissue in obesity.

Lipolysis (release of glycerol and free fatty acids) of subcutaneous human adipose tissuein vitro has been investigated in relation to relative body weight and fat cell size. Studying 86 persons, there was a highly significant logarithmic relation between relative body weight, fat cell size and lipid content of subcutaneous adipose tissue obtained from the abdominal region. Even in extreme obesity a mean fat cell diameter of 135 μ was generally not exceeded. In these cases overweight is due to hypertrophy as well as hyperplasia of adipose tissue. — The basal FFA and glycerol release, calculated on the basis of the lipid content, did not significantly differ in normal and overweight persons. The lipolysis of the individual cell increased, however, with increasing cell diameter. The quotient of resterification (FFA release: glycerol release) was significantly lower in obesity. — When lipolysis was stimulated with norepinephrine, theophylline or dibutyryl-cyclic AMP, the dose response relations were similar in obesity and normal weight. — The stimulation of lipolysis, expressed as % of baseline, was diminished in obesity. Stimulation with dibutyryl-cyclic-AMP was negatively correlated to the cell diameter. — The absolute release of metabolites per fat cell after stimulation with norepinephrine, theophylline or dibutyryl-cyclic AMP was positively correlated with the fat cell diameter. — Addition of glucose resulted in an increment in glycerol release and an inhibition of FFA release. However, the correlation of lipolysis with fat cell diameter was not affected. — The observations suggest that large fat cells are provided with additional total lipase. Under basal conditions the relation of inactive pro lipase to active lipase seemed to change in favour of the active enzyme.

Structure and Function of Aphid Cornicles1

The cornicle area of 18 species of aphids was studied histologically. In Cinara spp. and Longistigma caryae (Harris) (Lachnini) a multicellular sac, the wall of which is a layer of flat cells with compressed nuclei, extends into the cornicle. The sac is surrounded by vacuolated fat cells, and a mass of lipid is found in the sac. In Monellia costalis (Fitch) (Callaphidini) apparently an epidermal syncytial glandular sac extends into the very small cornicle. Stegophylla sp., also in this tribe, has a structure similar to that of the Lachnini. In the Aphidini ( Aphis, Urolcucon, Macrosiphum, Cachryphora, Hyalopterus, Amphorophora ) large fat cells collect in the cornicle and subcornicle area, some with a central nucleus, and many fat vacuoles, others with a large central vacuole and a peripheral nucleus in a ring of vesicular cytoplasm. In Neophyllaphis podocarpi Takahashi (Thelaxini) large granular cells are situated near the cornicle valve, with many smaller cells with central nuclei in the subcornicle area. The presence of lipid in the vacuoles and cornicle sacs was demonstrated by staining frozen sections with Sudan Black B. All species possessed a muscle originating on the venter below the cornicle and inserting on the cornicle valve. Its position is such that in addition to opening the valve it may elevate the long cornicle of some species. A dorsoventral muscle immediately anterior to the cornicle but not attached to it also may help to elevate the cornicle, but it appears to be used in association with other dorsoventral muscles in compressing the body contents, which causes emission of the droplet. The droplets of cornicle liquid consist of haemolymph, haemocytes, and lipid from dissociated fat cells. The lipid appears to be triglyceride. Aphids fed various concentrations of sucrose in water produce varying amounts of cornicle lipid, depending upon the sugar concentration in the diet. The primary function of cornicle droplet emission in aphids appears to be that of removal of excess lipid metabolized from a diet high in carbohydrates.

Microscopic fat cellsize measurements on frozen-cut adipose tissue in comparison with automatic determinations of osmium-fixed fat cells

Diameters of fat cells in adipose tissue slices, floating in an isoosmolar solution, were measured under a microscope. The slices were obtained from percutaneous biopsies by freeze-cutting after brief formaldehyde fixation. All cells in a given part of the slice were measured, thus avoiding selection. A normal distribution of fat cell diameters could be demonstrated with this method, as has been found with previously described methods. The error of the method was 2.6% for diameter and 8.0% for weight determinations. Storage of adipose tissue at 4 degrees C for 48 hr had no effects on cell size determinations. Results with this microscopic method were compared with those obtained from a previously described method for automatic determinations of osmium-fixed fat cells. The latter method was slightly modified by using a viscous electrolyte, which prevented sedimentation of large fat cells, and by using sonication to complete cell separation. The methods agreed closely. A method for calculating mean fat cell weight using osmium-fixed fat cells is described, which makes determinations of sample wet weight and ratio of lipid to wet weight unnecessary.

The histochemistry of Stellantchasmus falcatus Onji and Nishio, 1915 (Trematoda: Heterophyidae) metacercarial cyst in the mullet Mugil cephalus L. and histopathological alterations in the host†

The metacercarial cyst of the heterophyid trematode Stellantchasmus falcatus in the striated muscles of the mullet Mugil cephalus consists of three layers. Histochemical studies have indicated that these layers are chemically distinct. The acellular inner layer is comprised of complex carbohydrate polyanions rich in acidic groups while the medial cellular layer is comprised of a neutral mucopolysaccharide including a moeity of carbohydrate poiyanions. These two layers are believed to be of parasite origin. The outer layer is cellular and is of host origin. It is the most chemically complex and is believed to include one or more of the following: mucopolysaccharides, glycolipids and phospholipids. In addition, the carbohydrate moeity associated with the mucopolysaccharides and/or glycolipids is in the form of sulphated carbohydrate polyanions with undissociated carboxyls as well as acidic groups.The presence of the parasite results in the necrotic degeneration of the host's myofibers situated in the proximity of the parasite. Large fat cells fill the spaces vacated by necrotic muscle cells and many blood cells occur along the periphery of the parasite.

Triglyceride Synthesis in Human Subcutaneous Adipose Tissue Cells of Different Size

Abstract Human adipose tissue fat cells, liberated by eollagenase treatment, were separated into different sizes with a technique utilizing the differences in flotation rates of large and small fat cells in a physiological medium. — Incubation of fat cells after treatment with collagenase caused a pronounced breakage of fat cells. Therefore only incorporation of radioactivity from l‐14C‐glucose into triglyceride but not into carbon dioxide could be measured in separated fat cells. When collagenase‐liberated fat cells were incubated with radioactive glucose, radioactivity in the triglycerides increased with fat cell diameter in the remaining intact fat cells. When intact adipose tissue was incubated with radioactive glucose and then subjected to collagenase treatment, followed by separation of fat cells into different fat cell size classes, the same phenomenon was observed, namely a significant positive correlation between fat cell size and incorporation of radioactivity from glucose into triglycerides in adipose tissue with a wide range of fat cell diameters. Insulin response was small and varying. The dependence of triglyceride synthesis on fat cell size varied in different adipose tissue samples.

Lipoprotein lipase content and triglyceride fatty acid uptake in adipose tissue of rats of differing body weights

Increasing body weight appears to alter lipid metabolism in adipose tissue. We have measured the content of lipoprotein lipase and the uptake of chylomicron triglyceride fatty acids in epididymal fat pads of rats of different weights. In order that the results might be expressed in terms of cell numbers, the relationship between the weights of fat pads and the numbers and volumes of fat cells isolated from them was determined. Highly significant correlations were found between fat pad weight and both the number and the volume of the individual adipocytes. In rats weighing from 140 to 350 g, the increase in the size of fat pads was attributable almost equally to increases in cell size and in cell number. Lipoprotein lipase activity was measured in acetone powders of whole fat pads and of isolated fat cell preparations. With both, lipoprotein lipase activity per cell diminished significantly as the weight of fat tissue increased, i.e., larger fat cells contained less enzyme per cell than smaller cells. The uptake of triglyceride fatty acid radioactivity was measured after incubation of fat pads with radiolabeled rat lymph chylomicrons in flasks containing either buffer alone or with added glucose or glucose plus insulin. The addition of glucose and insulin led to a mean increase of 70% in the uptake of radioactivity, but larger adipocytes were stimulated less than smaller cells. This resulted in a significant negative correlation between the weights of fat pads and the uptake of radioactivity. Enlargement of fat cells also led to a diminution in their capacity to esterify fatty acids.

A Quantitative and Morphological Study of Bovine Longissimus Fat Cells

SUMMARY— A quantitative and morphological study was made of bovine fat cells from three marbling groups of longissimus muscle. Tracings on acetate paper were made of the visual marbling depots and the area measured at three positions with an ocular grid for both size and distribution of fat cells. Comparisons were also made of subcutaneous, intermuscular and intramuscular fat cell size. Intrafiber lipid accumulation was observed and the average number of red fibers per bundle determined. These results indicate that traceable intramuscular fat is not a good measure of total intramuscular fat. There did not appear to be a consistent medial, central and lateral marbling pattern among the three marbling groups; however, significant differences were apparent within groups. Fat cell size increased with increases in cell mass, marbling and total chemical fat of the muscle.Fat cells accumulated and grew in close proximity to portions of the circulatory system. Lipid deposits adjacent to the muscle contained larger fat cells than was evident in the extrafascicular spaces within the muscle. Intrafiber lipid was readily apparent in approximately 35% of the muscle fibers and probably represented either mitochondria or triglyceride. The interrelationship of subjective marbling scores, chemically determined fat, fat cell size, fat cell distribution and intrafiber lipid characteristics are complex and require complete investigation before the association of muscle fat and meat quality can be resolved.