Cholesteryl ester hydrolysis in J774 macrophages occurs in the cytoplasm and lysosomes.
(17/12738)
The relationship of cholesteryl ester hydrolysis to the physical state of the cholesteryl ester in J774 murine macrophages was explored in cells induced to store cholesteryl esters either in anisotropic (ordered) inclusions or isotropic (liquid) inclusions. In contrast to other cell systems, the rate of cholesteryl ester hydrolysis was faster in cells containing anisotropic inclusions than in cells containing isotropic inclusions. Two contributing factors were identified. Kinetic analyses of the rates of hydrolysis are consistent with a substrate competition by co-deposited triglyceride in cells with isotropic inclusions. In addition, hydrolysis of cholesteryl esters in cells with anisotropic droplets is mediated by both cytoplasmic and lysosomal lipolytic enzymes, as shown by using the lysosomotropic agent, chloroquine, and an inhibitor of neutral cholesteryl ester hydrolase, umbelliferyl diethylphosphate. In cells containing anisotropic inclusions, hydrolysis was partially inhibited by incubation in media containing either chloroquine or umbelliferyl diethylphosphate. Together, chloroquine and umbelliferyl diethylphosphate completely inhibited hydrolysis. However, when cells containing isotropic inclusions were incubated with umbelliferyl diethylphosphate, cholesteryl ester hydrolysis was completely inhibited, but chloroquine had no effect. Transmission electron microscopy demonstrated a primarily lysosomal location for lipid droplets in cells with anisotropic droplets and both non-lysosomal and lysosomal populations of lipid droplets in cells with isotropic droplets. These results support the conclusion that there is a lysosomal component to the hydrolysis of stored cholesteryl esters in foam cells. (+info)
Elevated hepatic lipase activity and low levels of high density lipoprotein in a normotriglyceridemic, nonobese Turkish population.
(18/12738)
Low levels of high density lipoprotein cholesterol (HDL-C) are associated with increased risk of coronary heart disease and, in the United States, are often associated with hypertriglyceridemia and obesity. In Turkey, low HDL-C levels are highly prevalent, 53% of men and 26% of women having HDL-C levels <35 mg/dl, in the absence of hypertriglyceridemia and obesity. In this study to investigate the cause of low HDL-C levels in Turks, various factors affecting HDL metabolism were assessed in normotriglyceridemic Turkish men and women living in Istanbul and in non-Turkish men and women living in San Francisco. Turkish men and women had significantly lower HDL-C levels than the San Francisco men and women, as well as markedly lower apolipoprotein A-I levels (25 and 39 mg/dl lower, respectively). In both Turkish and non-Turkish subjects, the mean body mass index was <27 kg/m2, the mean triglyceride level was <120 mg/dl, and the mean total cholesterol was 170-180 mg/dl. The mean hepatic triglyceride lipase activity was 21% and 31% higher in Turkish men and women, respectively, than in non-Turkish men and women, and remained higher even after subjects with a body mass index >50th percentile for men and women in the United States were excluded from the analysis. As no dietary or behavioral factors have been identified in the Turkish population that account for increased hepatic triglyceride lipase activity, the elevation most likely has a genetic basis. high density lipoprotein in a normotriglyceridemic, nonobese Turkish population. (+info)
Calcium and cAMP are second messengers in the adipokinetic hormone-induced lipolysis of triacylglycerols in Manduca sexta fat body.
(19/12738)
We have previously shown that stereospecific hydrolysis of stored triacylglycerol by a phosphorylatable triacylglycerol-lipase is the pathway for the adipokinetic hormone-stimulated synthesis of sn -1, 2-diacylglycerol in insect fat body. The current series of experiments were designed to determine whether cAMP and/or calcium are involved in the signal transduction pathway for adipokinetic hormone in the fat body. After adipokinetic hormone treatment, cAMP-dependent protein kinase activity in the fat body rapidly increased and reached a maximum after 20 min, suggesting that adipokinetic hormone causes an increase in cAMP. Forskolin (0.1 micrometer), an adenylate cyclase activator, induced up to a 97% increase in the secretion of diacylglycerol from the fat body. 8Br-cAMP (a membrane-permeable analog of cAMP) produced a 40% increase in the hemolymph diacylglycerol content. Treatment with cholera toxin, which also stimulates adenylate cyclase, induced up to a 145% increase in diacylglycerol production. Chelation of extracellular calcium produced up to 70% inhibition of the adipokinetic hormone-dependent mobilization of lipids. Calcium-mobilizing agents, ionomycin and thapsigargin, greatly stimulated DG production by up to 130%. Finally, adipokinetic hormone caused a rapid increase of calcium uptake into the fat body. Our findings indicate that the action of adipokinetic hormone in mobilizing lipids from the insect fat body involves both cAMP and calcium as intracellular messengers. (+info)
Caloric restriction leads to regional specialisation of adipocyte function in the rat.
(20/12738)
The study analysed the responses of three metabolic parameters in five distinct adipose tissue depots to caloric restriction (4 weeks) in the rat. The aims were to evaluate whether specific adipose tissue depots were recruited for triacylglycerol (TAG) storage and/or mobilisation, and to determine to what extent specific adipose tissue depots exhibited preferences for the source of fatty acid (FA) for TAG storage. Caloric restriction led to a general enhancement of the response of lipoprotein lipase (LPL), FA synthesis and glucose utilisation to a meal. Effects were particularly marked in the parametrial, perirenal and interscapular depots compared with mesenteric and subcutaneous depots. There was no evidence that individual depots selectively expressed a preference for the pathways concerned with the generation of FA for storage (the exogenous (LPL) and the endogenous (synthesis) pathway). However, the temporal sequence of activation of these pathways differed in a manner consistent with a switch from preponderant use of FA produced via de novo synthesis during the very early phase of feeding towards later use of FA derived from circulating TAG. The overall excursions in insulin levels observed in the calorie-restricted rats were comparable to those found in free-feeding rats, but the magnitude and the rapidity of the individual metabolic responses of the adipocyte were augmented. The data are consistent with a general enhancement of insulin sensitivity and responsiveness in adipose tissue of calorie-restricted rats, together with adaptive regional specialisation of adipocyte function. These adaptations would be predicted to facilitate the immediate conservation of dietary nutrients by promoting their storage as the FA or glycerol moieties of adipose tissue TAG and thereby to ensure the regulated release of FA and glycerol from adipose tissue in accordance with the requirement for glucose conservation and/or production. (+info)
Endotoxin-induced changes in IGF-I differ in rats provided enteral vs. parenteral nutrition.
(21/12738)
The purpose of the present study was to determine whether acute changes in the insulin-like growth factor (IGF) system induced by mild surgical trauma/fasting or endotoxin [lipopolysaccharide (LPS)] are differentially modulated by total enteral nutrition (TEN) or total parenteral nutrition (TPN). Rats had vascular catheters and a gastrostomy tube surgically placed and were fasted overnight. The next morning animals randomly received an isocaloric, isonitrogenous (250 kcal. kg-1. day-1, 1.6 g N. kg-1. day-1) infusion of either TEN or TPN for 48 h. Then rats were injected intravenously with Escherichia coli LPS (1 mg/kg) while nutritional support was continued. Time-matched control animals were injected with saline. After mild surgical trauma and an 18-h fast, TEN was more effective at increasing plasma IGF-I levels than TPN. Subsequent injection of LPS decreased IGF-I in blood, liver, and muscle in both TEN- and TPN-fed rats compared with saline-injected control animals. However, this decrease was approximately 30% greater in rats fed TPN compared with those fed TEN. LPS-induced downregulation of IGF-I mRNA expression in liver and muscle was also more prominent in TPN-fed rats. The LPS-induced increase in plasma corticosterone and tumor necrosis factor-alpha was greater (2- and 1.6-fold, respectively) in TPN-fed rats, and these changes were consistent with the greater reduction in IGF-I seen in these animals. In similarly treated rats allowed to survive for 24 h after LPS injection, the LPS-induced increase in the urinary 3-methylhistidine-to-creatinine ratio was smaller in TEN-fed rats. In summary, LPS reduced systemic levels of IGF-I as well as IGF-I protein and mRNA in critical target organs. Enteral feeding greatly attenuated this response. Maintenance of higher IGF-I levels in TEN-fed rats was associated with a reduction in inflammatory cytokine levels and lower rates of myofibrillar degradation. (+info)
Kinetics of dodecanedioic acid triglyceride in rats.
(22/12738)
The kinetics of the triglyceride of dodecanedioic acid (TGDA) has been investigated in 30 male Wistar rats after a rapid intravenous bolus injection. TGDA and its product of hydrolysis, nonesterified dodecanedioic acid (NEDA), were measured in plasma samples taken at different times using an improved high-performance liquid chromatographic method. The 24-h urinary excretion of TGDA was 1.54 +/- 0.37 micromol, corresponding to approximately 0.67% of the administered amount. Several kinetics models were considered, including central and peripheral compartments for the triglyceride and the free forms and expressing transports between compartments with combinations of linear, carrier-limited, or time-varying mechanisms. The parameter estimates of the kinetics of TGDA and of NEDA were finally obtained using a three-compartment model in which the transfer of TGDA to NEDA was assumed to be linear, through a peripheral compartment, and the tissue uptake of NEDA was assumed to be carrier limited. TGDA had a large volume of distribution ( approximately 0.5 l/kg body wt) with a fast disappearance rate from plasma (0.42 min-1), whereas NEDA had a very small volume of distribution ( approximately 0.04 l/kg body wt) and a tissue uptake with maximal transport rate of 0.636 mM/min. In conclusion, this first study on the triglyceride form of dodecanedioic acid indicates that it is rapidly hydrolyzed and that both triglyceride and nonesterified forms are excreted in the urine to a very low extent. The tissue uptake rate of NEDA is consistent with the possibility of achieving substantial energy delivery, should it be added to parenteral nutrition formulations. Furthermore, the amount of sodium administered with the triglyceride form is one-half of that necessary with the free diacid. (+info)
Insulin resistance of muscle glucose transport in male and female rats fed a high-sucrose diet.
(23/12738)
It has been reported that, unlike high-fat diets, high-sucrose diets cause insulin resistance in the absence of an increase in visceral fat and that the insulin resistance develops only in male rats. This study was done to 1) determine if isolated muscles of rats fed a high-sucrose diet are resistant to stimulation of glucose transport when studied in vitro and 2) obtain information regarding how the effects of high-sucrose and high-fat diets on muscle insulin resistance differ. We found that, compared with rat chow, semipurified high-sucrose and high-starch diets both caused increased visceral fat accumulation and insulin resistance of skeletal muscle glucose transport. Insulin responsiveness of 2-deoxyglucose (2-DG) transport measured in epitrochlearis and soleus muscles in vitro was decreased approximately 40% (P < 0.01) in both male and female rats fed a high-sucrose compared with a chow diet. The high-sucrose diet also caused resistance of muscle glucose transport to stimulation by contractions. There was a highly significant negative correlation between stimulated muscle 2-DG transport and visceral fat mass. In view of these results, the differences in insulin action in vivo observed by others in rats fed isocaloric high-sucrose and high-starch diets must be due to additional, specific effects of sucrose that do not carry over in muscles studied in vitro. We conclude that, compared with rat chow, semipurified high-sucrose and high-cornstarch diets, like high-fat diets, cause increased visceral fat accumulation and severe resistance of skeletal muscle glucose transport to stimulation by insulin and contractions. (+info)
Socioeconomic status and determinants of hemostatic function in healthy women.
(24/12738)
Hemostatic factors are reported to be associated with coronary heart disease (CHD). Socioeconomic status (SES) is 1 of the determinants of the hemostatic profile, but the factors underlying this association are not well known. Our aim was to examine determinants of the socioeconomic differences in hemostatic profile. Between 1991 and 1994, we studied 300 healthy women, aged 30 to 65 years, who were representative of women living in the greater Stockholm area. Fibrinogen, factor VII mass concentration (FVII:Ag), activated factor VII (FVIIa), von Willebrand factor (vWF), and plasminogen activator inhibitor-1 (PAI-1) were measured. Educational attainment was used as a measure of SES. Low educational level and an unfavorable hemostatic profile were both associated with older age, unhealthful life style, psychosocial stress, atherogenic biochemical factors, and hypertension. Levels of hemostatic factors increased with lower educational attainment. Independently of age, the differences between the lowest (mandatory) and highest (college/university) education in FVII:Ag levels were 41 microg/L (95% confidence interval [CI], 15 to 66 microg/L, P=0.001), 0.26 g/L (95% CI, 0.10 to 0.42 g/L, P=0.001) in fibrinogen levels, and 0.11 U/mL (95% CI, 0.09 to 0.12 U/mL, P=0.03) in levels of vWF. The corresponding differences in FVIIa and PAI-1 were not statistically significant. With further adjustment for menopausal status, family history of CHD, marital status, psychosocial stress, lifestyle patterns, biochemical factors, and hypertension, statistically significant differences between mandatory and college/university education were observed in FVII:Ag (difference=34 microg/L; 95% CI, 2 to 65 microg/L, P=0.05) but not in fibrinogen (difference=0.03 g/L; 95% CI, -0.13 to 0.19 g/L, P=0.92) or in vWF (difference=0.06 U/mL; 95% CI, -0.10 to 0.22 U/mL, P=0.45). An educational gradient was most consistent and statistically significant for FVII:Ag, fibrinogen, and vWF. Age, psychosocial stress, unhealthful life style, atherogenic biochemical factors, and hypertension mediated the association of low educational level with elevated levels of fibrinogen and vWF. Psychosocial stress and unhealthful life style were the most important contributing factors. There was an independent association between education and FVII:Ag, which could not be explained by any of these factors. (+info)