Effects of fasting on muscle mitochondrial energetics and fatty acid metabolism in Ucp3(-/-) and wild-type mice.
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Uncoupling protein-3 (UCP3) is a mitochondrial carrier protein of as yet undefined physiological function. To elucidate characteristics of its function, we studied the effects of fasting on resting metabolic rate, respiratory quotient, muscle Ucp3 expression, and mitochondrial proton leak in wild-type and Ucp3(-/-) mice. Also analyzed were the fatty acid compositions of skeletal muscle mitochondria in fed and fasted Ucp3(-/-) and wild-type mice. In wild-type mice, fasting caused significant increases in Ucp3 (4-fold) and Ucp2 (2-fold) mRNA but did not significantly affect mitochondrial proton leak. State 4 oxygen consumption was not affected by fasting in either of the two groups. However, protonmotive force was consistently higher in mitochondria of Ucp3(-/-) animals (P = 0.03), and fasting further augmented protonmotive force in Ucp3(-/-) mice; there was no effect in wild-type mitochondria. Resting metabolic rates decreased with fasting in both groups. Ucp3(-/-) mice had higher respiratory quotients than wild-type mice in fed resting states, indicating impaired fatty acid oxidation. Altogether, results show that the fasting-induced increases in Ucp2 and Ucp3 do not correlate with increased mitochondrial proton leak but support a role for UCP3 in fatty acid metabolism. (+info)
Lipids stimulate the production of 6-keto-prostaglandin f(1alpha) in human dorsal hand veins.
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Obese hypertensives have increased nonesterified fatty acids (NEFAs) and alpha-adrenergic vascular reactivity. Raising NEFAs locally with intralipid and heparin augments dorsal hand venoconstrictor responses to phenylephrine, an alpha(1)-adrenoceptor agonist. The enhanced venoconstrictor responses were reversed by indomethacin. The findings suggest that raising NEFAs leads to the generation of cyclooxygenase (COX) product(s) that enhance vascular reactivity. To test this notion, 6-keto-PGF(1alpha) and TxB(2), the stable metabolites of prostaglandin H(2) (PGH(2)); prostacyclin (PGI(2)); and thromboxane (TxA(2)), were measured approximately 1.5 to 2 cm downstream of a dorsal hand vein infusion of intralipid and heparin (n=10) or saline and heparin (n=5) for 2 hours each. During the third hour, intralipid and heparin (experimental) and saline and heparin (control) were continued, and either saline (control) or indomethacin (intervention) were infused. Intralipid and heparin raised local 6-keto PGF(1alpha) concentrations by 350% to 500% (P<0.005), but saline and heparin did not (P=NS). TxB(2) levels did not change significantly with any infusion. Infusion of indomethacin during the third hour of intralipid and heparin lowered plasma 6-keto-PGF(1alpha) (P<0.05), whereas infusion of saline with intralipid and heparin did not (P=NS). Oleic and linoleic acids at 100 micromol/L, increased 6-keto-PGF(1alpha) in vascular smooth muscle cells (VSMCs) through a protein kinase C and extracellular, signal-regulated kinase independent pathway. However, oleic and linoleic acids increased intracellular Ca(2+) in VSMCs. The data indicate that NEFAs induce the production of COX products, perhaps via Ca(2+)-dependent activation of phospholipase A(2). The COX product(s) may contribute to increased vascular alpha-adrenergic reactivity among insulin-resistant individuals when NEFAs are elevated. (+info)
Body fat of British and Dutch infants.
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The fatty acids in the body fat of 41 British and 37 Dutch infants between birth and 1 year were determined. At birth linoleic acid contributed 1-3% of the total fatty acids of the body fat in infants in both countries. By one month its proportion in the fat of the Dutch infants was about 25% and by four months 32-37%; in the fat of the British infants it was never more than 3%. In the Dutch infants this large increase in the linoleic acid percentage was accompanied by a fall in the percentage contribution of others, particularly the saturated acids myristic, palmitic, and stearic. Infants born preterm showed changes in their fat after birth similar to those in fullterm infants. The difference between the composition of the fat of the infants in the two countries is attributed to the nature of the fat in the milk they received. Until recently most British infants who are not breast-fed have been given milks based on cow's milk with only minor modifications. For the past 10 years many Dutch infants have been given a milk in which all the cow's milk fat has been replaced by maize oil. Dutch infants also had a lower concentration of cholesterol in their serum than British infants, which was not unexpected. The results show that the triglycerides in the adipose tissue are profoundly influenced by the nature of the fat in the diet. (+info)
X-ray structure of the orphan nuclear receptor RORbeta ligand-binding domain in the active conformation.
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The retinoic acid-related orphan receptor beta (RORbeta) exhibits a highly restricted neuronal-specific expression pattern in brain, retina and pineal gland. So far, neither a natural RORbeta target gene nor a functional ligand have been identified, and the physiological role of the receptor is not well understood. We present the crystal structure of the ligand-binding domain (LBD) of RORbeta containing a bound stearate ligand and complexed with a coactivator peptide. In the crystal, the monomeric LBD adopts the canonical agonist-bound form. The fatty acid ligand-coactivator peptide combined action stabilizes the transcriptionally active conformation. The large ligand-binding pocket is strictly hydrophobic on the AF-2 side and more polar on the beta-sheet side where the carboxylate group of the ligand binds. Site-directed mutagenesis experiments validate the significance of the present structure. Homology modeling of the other isotypes will help to design isotype-selective agonists and antagonists that can be used to characterize the physiological functions of RORs. In addition, our crystallization strategy can be extended to other orphan nuclear receptors, providing a powerful tool to delineate their functions. (+info)
Lipid metabolism in the cow during starvation-induced ketosis.
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1. Concentrations and compositions of liver, serum and milk lipids of cows were measured during 6 days' starvation and serum lipids during 60 days' re-feeding. 2. The concentration of free fatty acid in serum increased fivefold during starvation. 3. The content of total lipid in liver (g/100g of liver dry matter) doubled owing to a 20-fold increase in triglyceride, an eightfold increase in cholesterol ester, a three fold increase in free fatty acid and a 20% increase in cholesterol. There were no changes in the content or composition of liver phospholipids. 4. Starvation lowered the concentrations of total lipid, phospholipid and cholesterol ester of dextran sulphate-precipitable serum lipoproteins. Total lipid and cholesterol ester concentrations in lipoproteins of d greater than 1.055 and in lipoproteins not precipitable by dextran sulphate decreased from day 4 of the starvation period and during the first 20 days' re-feeding. 5. During starvation there were decreases in percentages of stearic acid and increases in oleic acid in serum free fatty acids and triglycerides and in liver neutral lipid. 6. Throughout starvation total milk lipid yield decreased, yields and percentages of C4-14 fatty acids decreased and percentages of C18 fatty acids increased. 7. It is suggested that accumulation of triglyceride in liver may be caused by increased uptake of plasma free fatty acids without corresponding increase in lipoprotein secretion. (+info)
In vitro and in vivo study of two types of long-circulating solid lipid nanoparticles containing paclitaxel.
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Paclitaxel (Taxol), a diterpenoid isolated from Taxus brevifolia, is effective against several murine tumors, and is one of the most exciting anticancer molecules currently available. Due to its low solubility in water, it is clinically administered with polyethoxylated castor oil (Cremophor EL), which causes serious side effects. Inclusion of paclitaxel in solid lipid nanoparticles (SLNs) has proved to be a good approach to eliminate the need for Cremophor EL and improve the drug's antitumor efficacy. This paper describes the development of two types of long-circulating SLNs as colloidal carriers for paclitaxel. SLNs are constituted mainly of bioacceptable and biodegradable lipids. In vitro release kinetics showed that the release was very slow, the release of paclitaxel from F68-SLN is linear, and the release of paclitaxel from Brij78-SLN followed the Weibull equation. Pharmacokinetics was evaluated in KM mice after injection of paclitaxel formulated in Cremophor EL or in Brij78-SLN and F68-SLN. Encapsulation of paclitaxel in both SLNs produced marked differences compared with the free drug pharmacokinetics. F68-SLN and Brij78-SLN are long-circulating (t 1/2 beta, 10.06 and 4.88 h, respectively) compared with paclitaxel injection (t 1/2 beta, 1.36 h). (+info)
Estimation of capping incidence by indentation fracture tests.
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The purpose of this study was to predict the capping tendencies of pharmaceutical powders by creating indentation fracture on compacts. Three sets of binary mixtures containing different concentrations of each ingredient were used in the study. The binary mixtures were chosen to represent plastic-plastic, plastic-brittle, and brittle-brittle combination of materials. The mixtures were tableted at different pressures and speeds on Prester, a tablet press simulator. These mixtures were also compacted on the Instron Universal Testing Machine 4502. Static indentation tests were done on these compacts at different depths until surface cracking and chipping were observed. The extent of surface cracking and chipping was observed from light microscope and scanning electron microscope images. A rank order correlation was observed between lamination susceptibility and the depth at which indentation failure occurred. It was concluded that indentation fracture tests could provide a useful estimate of lamination properties of pharmaceutical powders. (+info)
Comparative evaluation of tableting compression behaviors by methods of internal and external lubricant addition: inhibition of enzymatic activity of trypsin preparation by using external lubricant addition during the tableting compression process.
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This study evaluated tableting compression by using internal and external lubricant addition. The effect of lubricant addition on the enzymatic activity of trypsin, which was used as a model drug during the tableting compression process, was also investigated. The powder mixture (2% crystalline trypsin, 58% crystalline lactose, and 40% microcrystalline cellulose) was kneaded with 5% hydroxypropyl cellulose aqueous solution and then granulated using an extruding granulator equipped with a 0.5-mm mesh screen at 20 rpm. After drying, the sample granules were passed through a 10-mesh screen (1680 microm). A 200-mg sample was compressed by using 8-mm punches and dies at 49, 98, 196, or 388 MPa (Mega Pascal) at a speed of 25 mm/min. The external lubricant compression was performed using granules without lubricant in the punches and dies. The granules were already dry coated by the lubricant. In contrast, the internal lubricant compression was performed using sample granules (without dry coating) containing 0.5% lubricant. At 98 MPa, for example, the compression level using the external lubricant addition method was about 13% higher than that for internal addition. The significantly higher compressing energy was also observed at other MPas. By comparison, the friction energy for the external addition method calculated based on upper and lower compression forces was only slightly larger. The hardness of tablets prepared using the internal addition method was 34% to 48% lower than that for the external addition method. The total pore volume of the tablet prepared using the external addition method was significantly higher. The maximum ejection pressure using the no-addition method (ie, the tablet was prepared using neither dry-coated granules nor added lubricant) was significantly higher than that of other addition methods. The order was as follows: no addition, external addition, and then internal addition. The ejection energy (EE) for internal addition was the lowest; for no addition, EE was the highest. In the dissolution test, the tablets obtained using external addition immediately disintegrated and showed faster drug release than those prepared using internal addition. This result occurred because the water penetration rate of the tablet using the external addition was much higher. The trypsin activity in tablets prepared using the external addition method was significantly higher than that produced using the internal addition method at the same pressure. All these results suggest that the external addition method might produce a fast-dissolution tablet. Because the drug will be compressed using low pressure only, an unstable bulk drug may be tableted without losing potency. (+info)