Mitochondria-targeted nanoplatforms for enhanced photodynamic therapy against hypoxia tumor.

BACKGROUND: Photodynamic therapy (PDT) is a promising therapeutic modality that can convert oxygen into cytotoxic reactive oxygen species (ROS) via photosensitizers to halt tumor growth. However, hypoxia and the unsatisfactory accumulation of photosensitizers in tumors severely diminish the therapeutic effect of PDT. In this study, a multistage nanoplatform is demonstrated to overcome these limitations by encapsulating photosensitizer IR780 and oxygen regulator 3-bromopyruvate (3BP) in poly (lactic-co-glycolic acid) (PLGA) nanocarriers. RESULTS: The as-synthesized nanoplatforms penetrated deeply into the interior region of tumors and preferentially remained in mitochondria due to the intrinsic characteristics of IR780. Meanwhile, 3BP could efficiently suppress oxygen consumption of tumor cells by inhibiting mitochondrial respiratory chain to further improve the generation of ROS. Furthermore, 3BP could abolish the excessive glycolytic capacity of tumor cells and lead to the collapse of ATP production, rendering tumor cells more susceptible to PDT. Successful tumor inhibition in animal models confirmed the therapeutic precision and efficiency. In addition, these nanoplatforms could act as fluorescence (FL) and photoacoustic (PA) imaging contrast agents, effectuating imaging-guided cancer treatment. CONCLUSIONS: This study provides an ideal strategy for cancer therapy by concurrent oxygen consumption reduction, oxygen-augmented PDT, energy supply reduction, mitochondria-targeted/deep-penetrated nanoplatforms and PA/FL dual-modal imaging guidance/monitoring. It is expected that such strategy will provide a promising alternative to maximize the performance of PDT in preclinical/clinical cancer treatment.

Why Are Branched-Chain Amino Acids Increased in Starvation and Diabetes?

Branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are increased in starvation and diabetes mellitus. However, the pathogenesis has not been explained. It has been shown that BCAA catabolism occurs mostly in muscles due to high activity of BCAA aminotransferase, which converts BCAA and α-ketoglutarate (α-KG) to branched-chain keto acids (BCKAs) and glutamate. The loss of α-KG from the citric cycle (cataplerosis) is attenuated by glutamate conversion to α-KG in alanine aminotransferase and aspartate aminotransferase reactions, in which glycolysis is the main source of amino group acceptors, pyruvate and oxaloacetate. Irreversible oxidation of BCKA by BCKA dehydrogenase is sensitive to BCKA supply, and ratios of NADH to NAD+ and acyl-CoA to CoA-SH. It is hypothesized that decreased glycolysis and increased fatty acid oxidation, characteristic features of starvation and diabetes, cause in muscles alterations resulting in increased BCAA levels. The main alterations include (i) impaired BCAA transamination due to decreased supply of amino groups acceptors (α-KG, pyruvate, and oxaloacetate) and (ii) inhibitory influence of NADH and acyl-CoAs produced in fatty acid oxidation on citric cycle and BCKA dehydrogenase. The studies supporting the hypothesis and pros and cons of elevated BCAA concentrations are discussed in the article.

Non-invasive detection of divergent metabolic signals in insulin deficiency vs. insulin resistance in vivo.

The type 2 diabetic phenotype results from mixed effects of insulin deficiency and insulin resistance, but the relative contributions of these two distinct factors remain poorly characterized, as do the respective roles of the gluconeogenic organs. The purpose of this study was to investigate localized in vivo metabolic changes in liver and kidneys of contrasting models of diabetes mellitus (DM): streptozotocin (STZ)-treated wild-type Zucker rats (T1DM) and Zucker diabetic fatty (ZDF) rats (T2DM). Intermediary metabolism was probed using hyperpolarized (HP) [1-13C]pyruvate MRI of the liver and kidneys. These data were correlated with gene expression data for key mediators, assessed using rtPCR. Increased HP [1-13C]lactate was detected in both models, in association with elevated gluconeogenesis as reflected by increased expression of phosphoenolpyruvate carboxykinase. In contrast, HP [1-13C]alanine diverged between the two models, increasing in ZDF rats, while decreasing in the STZ-treated rats. The differences in liver alanine paralleled differences in key lipogenic mediators. Thus, HP [1-13C]alanine is a marker that can identify phenotypic differences in kidneys and liver of rats with T1DM vs. T2DM, non-invasively in vivo. This approach could provide a powerful diagnostic tool for characterizing tissue metabolic defects and responses to treatment in diabetic patients with ambiguous systemic manifestations.

Transport of haloacids across biological membranes.

Haloacids are considered to be environmental pollutants, but some of them have also been tested in clinical research. The way that haloacids are transported across biological membranes is important for both biodegradation and drug delivery purposes. In this review, we will first summarize putative haloacids transporters and the information about haloacids transport when studying carboxylates transporters. We will then introduce MCT1 and SLC5A8, which are respective transporter for antitumor agent 3-bromopyruvic acid and dichloroacetic acid, and monochloroacetic acid transporters Deh4p and Dehp2 from a haloacids-degrading bacterium. Phylogenetic analysis of these haloacids transporters and other monocarboxylate transporters reveals their evolutionary relationships. Haloacids transporters are not studied to the extent that they deserve compared with their great application potentials, thus future inter-discipline research are desired to better characterize their transport mechanisms for potential applications in both environmental and clinical fields.

Intratracheal instillation of ethyl pyruvate nanoparticles prevents the development of shunt-flow-induced pulmonary arterial hypertension in a rat model.

PURPOSE: To investigate whether inhalation of ethyl pyruvate (EP) encapsulated with poly(ethylene glycol)-block-lactide/glycolide copolymer nanoparticles (EP-NPs) can prevent the development of shunt-flow-induced hyperkinetic pulmonary arterial hypertension (PAH) in a rat model. MATERIALS AND METHODS: Rats were separated into five groups: blank (ie, no treatment after shunt flow), normal control (ie, no shunt flow or treatment), EP-NP instillation, EP-only instillation, and vehicle. The animals received intratracheal instillation of EP-NPs or other treatments immediately after a shunt flow, and treatment continued weekly until the end of the experiment. Hemodynamic data were recorded, pulmonary arterial remodeling was assessed, and levels of inflammatory mediators and ET1 expression in the lung and serum were analyzed. In addition, retention of EP in the lungs of rats in the EP-NP and EP-only groups was measured using high-performance liquid chromatography. RESULTS: After 12 weeks, hemodynamic abnormalities and pulmonary arterial remodeling were improved in the EP-NP instillation group, compared with the blank, EP-only, and vehicle groups (P<0.05). In addition, the EP-NP group showed significantly decreased levels of HMGB1, IL-6, TNFα, reactive oxygen species, and ET1 in the lung during PAH development (P<0.05). Furthermore, EP-NP instillation was associated with reduced serum levels of inflammatory factors and ET1. High-performance liquid-chromatography measurement indicated that EP retention was greater in the lungs of the EP-NP group than in the EP-only group. CONCLUSION: EP-NP instillation attenuated inflammation and prevented pulmonary arterial remodeling during the development of PAH induced by shunt flow. In the future, EP-NP delivery into the lung might provide a novel approach for preventing PAH.

The cytotoxicity of 3-bromopyruvate in breast cancer cells depends on extracellular pH.

Although the anti-cancer properties of 3BP (3-bromopyruvate) have been described previously, its selectivity for cancer cells still needs to be explained [Ko et al. (2001) Cancer Lett. 173, 83-91]. In the present study, we characterized the kinetic parameters of radiolabelled [14C] 3BP uptake in three breast cancer cell lines that display different levels of resistance to 3BP: ZR-75-1 < MCF-7 < SK-BR-3. At pH 6.0, the affinity of cancer cells for 3BP transport correlates with their sensitivity, a pattern that does not occur at pH 7.4. In the three cell lines, the uptake of 3BP is dependent on the protonmotive force and is decreased by MCTs (monocarboxylate transporters) inhibitors. In the SK-BR-3 cell line, a sodium-dependent transport also occurs. Butyrate promotes the localization of MCT-1 at the plasma membrane and increases the level of MCT-4 expression, leading to a higher sensitivity for 3BP. In the present study, we demonstrate that this phenotype is accompanied by an increase in affinity for 3BP uptake. Our results confirm the role of MCTs, especially MCT-1, in 3BP uptake and the importance of cluster of differentiation (CD) 147 glycosylation in this process. We find that the affinity for 3BP transport is higher when the extracellular milieu is acidic. This is a typical phenotype of tumour microenvironment and explains the lack of secondary effects of 3BP already described in in vivo studies [Ko et al. (2004) Biochem. Biophys. Res. Commun. 324, 269-275].

The antitumor agent 3-bromopyruvate has a short half-life at physiological conditions.

Clinical research is currently exploring the validity of the anti-tumor candidate 3-bromopyruvate (3-BP) as a novel treatment for several types of cancer. However, recent publications have overlooked rarely-cited earlier work about the instability of 3-BP and its decay to 3-hydroxypyruvate (3-HP) which have obvious implications for its mechanism of action against tumors, how it is administered, and for precautions when preparing solutions of 3-BP. This study found the first-order decay rate of 3-BP at physiological temperature and pH has a half-life of only 77 min. Lower buffer pH decreases the decay rate, while choice of buffer and concentration do not affect it. A method for preparing more stable solutions is also reported.

Characterization of pyruvate uptake in Escherichia coli K-12.

The monocarboxylate pyruvate is an important metabolite and can serve as sole carbon source for Escherichia coli. Although specific pyruvate transporters have been identified in two bacterial species, pyruvate transport is not well understood in E. coli. In the present study, pyruvate transport was investigated under different growth conditions. The transport of pyruvate shows specific activities depending on the growth substrate used as sole carbon source, suggesting the existence of at least two systems for pyruvate uptake: i) one inducible system and probably highly specific for pyruvate and ii) one system active under non-induced conditions. Using the toxic pyruvate analog 3-fluoropyruvate, a mutant was isolated unable to grow on and transport pyruvate. Further investigation revealed that a revertant selected for growth on pyruvate regained the inducible pyruvate transport activity. Characterization of pyruvate excretion showed that the pyruvate transport negative mutant accumulated pyruvate in the growth medium suggesting an additional transport system for pyruvate excretion. The here presented data give valuable insight into the pyruvate metabolism and transport of E. coli suggesting the presence of at least two uptake systems and one excretion system to balance the intracellular level of pyruvate.

Transport and cytotoxicity of the anticancer drug 3-bromopyruvate in the yeast Saccharomyces cerevisiae.

We have investigated the cytotoxicity in Saccharomyces cerevisiae of the novel antitumor agent 3-bromopyruvate (3-BP). 3-BP enters the yeast cells through the lactate/pyruvate H(+) symporter Jen1p and inhibits cell growth at minimal inhibitory concentration of 1.8 mM when grown on non-glucose conditions. It is not submitted to the efflux pumps conferring Pleiotropic Drug Resistance in yeast. Yeast growth is more sensitive to 3-BP than Gleevec (Imatinib methanesulfonate) which in contrast to 3-BP is submitted to the PDR network of efflux pumps. The sensitivity of yeast to 3-BP is increased considerably by mutations or chemical treatment by buthionine sulfoximine that decrease the intracellular concentration of glutathione.

Metabolic imaging in the anesthetized rat brain using hyperpolarized [1-13C] pyruvate and [1-13C] ethyl pyruvate.

Formulation, polarization, and dissolution conditions were developed to obtain a stable hyperpolarized solution of [1-(13)C]-ethyl pyruvate. A maximum tolerated concentration and injection rate were determined, and (13)C spectroscopic imaging was used to compare the uptake of hyperpolarized [1-(13)C]-ethyl pyruvate relative to hyperpolarized [1-(13)C]-pyruvate into anesthetized rat brain. Hyperpolarized [1-(13)C]-ethyl pyruvate and [1-(13)C]-pyruvate metabolic imaging in normal brain is demonstrated and quantified in this feasibility and range-finding study.

Beneficial effects of ethyl pyruvate in a mouse model of spinal cord injury.

The aim of the present study was to evaluate in a mouse model of spinal cord injury (SCI) the effect of the treatment with ethyl pyruvate (EP). Spinal cord injury was induced by the application of vascular clips (force of 24 g) to the dura via a four-level T5-T8 laminectomy in mice. Treatment with EP (75, 25, or 8.5 mg/kg) 1 and 6 h after the SCI significantly decreased (a) the degree of spinal cord inflammation and tissue injury (histological score), (b) neutrophil infiltration (myeloperoxidase activity), (c) nitrotyrosine formation and iNOS expression, (d) proinflammatory cytokines expression, (e) nuclear factor kappaB activation, (f) extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase phosphorylation, and (g) apoptosis (TUNEL staining, Fas ligand, Bax, and Bcl-2 expression). Moreover, EP (75, 25, or 8.5 mg/kg) significantly ameliorated in a dose-dependent manner the loss of limb function (evaluated by motor recovery score). Taken together, our results demonstrate that EP treatment reduces the development of inflammation and tissue injury associated with spinal cord trauma.

Targeting of VX2 rabbit liver tumor by selective delivery of 3-bromopyruvate: a biodistribution and survival study.

The aim of this study was to determine the biodistribution and tumor targeting ability of (14)C-labeled 3-bromopyruvate ([(14)C]3-BrPA) after i.a. and i.v. delivery in the VX2 rabbit model. In addition, we evaluated the effects of [(14)C]3-BrPA on tumor and healthy tissue glucose metabolism by determining (18)F-deoxyglucose (FDG) uptake. Last, we determined the survival benefit of i.a. administered 3-BrPA. In total, 60 rabbits with VX2 liver tumor received either 1.75 mM [(14)C]3-BrPA i.a., 1.75 mM [(14)C]3-BrPA i.v., 20 mM [(14)C]3-BrPA i.v., or 25 ml of phosphate-buffered saline (PBS). All rabbits (with the exception of the 20 mM i.v. group) received FDG 1 h before sacrifice. Next, we compared survival of animals treated with i.a. administered 1.75 mM [(14)C]3-BrPA in 25 ml of PBS (n = 22) with controls (n = 10). After i.a. infusion, tumor uptake of [(14)C]3-BrPA was 1.8 +/- 0.2% percentage of injected dose per gram of tissue (%ID/g), whereas other tissues showed minimal uptake. After i.v. infusion (1.75 mM), tumor uptake of [(14)C]3-BrPA was 0.03 +/- 0.01% ID/g. After i.a. administration of [(14)C]3-BrPA, tumor uptake of FDG was 26 times lower than in controls. After i.v. administration of [(14)C]3-BrPA, there was no significant difference in tumor FDG uptake. Survival analysis showed that rabbits treated with 1.75 mM 3-BrPA survived longer (55 days) than controls (18.6 days). Intra-arterially delivered 3-BrPA has a favorable biodistribution profile, combining a high tumor uptake resulting in blockage of FDG uptake with no effects on healthy tissue. The local control of the liver tumor by 3-BrPA resulted in a significant survival benefit.

Apoptosis-inducing antitumor efficacy of hexokinase II inhibitor in hepatocellular carcinoma.

Hypoxia stimulates hepatocellular carcinoma (HCC) cell growth via hexokinase (HK) II induction, and alternatively, HK II inhibition induces apoptosis by activating mitochondrial signaling. This study was to investigate whether the induction of HK II by hypoxia is associated with enhanced mitochondrial stability and to confirm the apoptosis-inducing efficacy of HK II inhibitor in an in vivo model of HCC. Mitochondrial stability was examined by treating isolated mitochondria with deoxycholate, a permeability-enhancing agent. Alteration of permeability transition pore complex composition was analyzed by immunoprecipitation and immunoblotting. An in vivo model of HCC was established in C3H mice i.d. implanted with MH134 cells. The antitumor efficacy of i.p. given 3-bromopyruvate (3-BrPA), a HK II inhibitor, was evaluated by measuring tumor volumes and quantifying apoptosis using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining and (99m)Tc-hydrazinonicotinamide-Annexin V scans. Hypoxia enhanced mitochondrial stability, and this was inhibited by 3-BrPA treatment. In particular, HK II levels in permeability transition pore complex immunoprecipitates were reduced after 3-BrPA treatment. In mice treated with 3-BrPA, mean tumor volumes and tumor volume growth were found to be significantly reduced. Moreover, percentages of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were significantly increased in 3-BrPA-treated mice, and this apoptosis-inducing efficacy was reflected in vivo by (99m)Tc-hydrazinonicotinamide-Annexin V imaging. Our results show that hypoxia enhances mitochondrial stability via HK II induction and that HK II inhibitor treatment exhibits an in vivo antitumor effect by inducing apoptosis. Therefore, HK II inhibitors may be therapeutically useful for the treatment of advanced infiltrative hypovascular HCCs, which are growing in a hypoxic environment.

Attenuation of sugar cataract by ethyl pyruvate.

Studies describe an attenuation of sugar cataract formation by topical administration of ethyl pyruvate. Cataract formation was induced by feeding young rats a 30% galactose diet. Mature cataracts appeared in about thirty days. Instillation of the eye drops containing 5% ethyl pyruvate decelerated the process significantly. Biochemically, the effect was reflected by lowering in the contents of dulcitol and glycated proteins. The ATP levels were also higher in comparison to the placebo treated group. The effects are hence attributable to the effect of pyruvate in inhibiting dulcitol synthesis and protein glycation, in addition to its antioxidant properties and metabolic support. The use of esterified pyruvate instead of the unesterified pyruvate was preferred because of its greater penetration through the cornea and consequently a higher concentration attained in the aqueous humor.

The influence of pyruvic acid on the pharmacokinetics of sulphadiazine in rabbits.

During the past few years, acetylation polymorphism has been shown to be a proven, established fact, and N-acetyltransferase, an enzyme that transfers an acetyl group to the substrate, has been recognized as the main factor in acetylation polymorphism. In a recent study, a significant difference between the acetylation phenotype and plasma pyruvic acid (PA) concentration in rabbits was found. In this report, the influence of PA on the pharmacokinetics of sulphadiazine (SDZ), a drug that has been used in pharmacogenetic studies of acetylation, was studied. By using a loading dose of 300 mg kg-1, and an infusion rate of 7.5 mg min-1 kg-1 of PA, the concentration of PA reached a steady state (Css approximately equal to 100 micrograms mL-1) in 30 min. During PA infusion in rapid-acetylation rabbits, no significant changes were found in any of the pharmacokinetic parameters for SDZ. However, differences were found in the beta half-life, AUC, clearance, and k10 of SDZ in slow acetylators: the beta half-life decreased from 115.74 +/- 12.47 min to 62.96 +/- 4.36 min (p < 0.001); AUC decreased from 10,617.38 +/- 1179.81 micrograms min mL-1 to 6217.14 +/- 391.32 micrograms min mL-1 (p < 0.001); clearance increased from 0.0044 +/- 0.0008 L min-1 kg-1 to 0.0068 +/- 0.0007 L min-1 kg-1 (p < 0.001); and k10 increased from 0.0090 +/- 0.0009 min-1 to 0.0193 +/- 0.0028 min-1 (p < 0.005). The reason for this may be that PA influences the elimination of SDZ in slow-acetylation rabbits.

A double mutant allele, csr1-4, of Arabidopsis thaliana encodes an acetolactate synthase with altered kinetics.

A comparison is made of the kinetic characteristics of acetolactate synthase (EC 4.1.3.18) in extracts from Columbia wild type and four near-isogenic, herbicide-resistant mutants of Arabidopsis thaliana (L.) Heynh. The mutants used were the chlorsulfuron-resistant GH50 (csr1-1), the imazapyr-resistant GH90 (csr1-2), the triazolopyrimidine-resistant Tzp5 (csr1-3) and the multiherbicide-resistant, double mutant GM4.8 (csr1-4), derived from csr1-1 and csr1-2 by intragenic recombination (G. Mourad et al. 1994, Mol. Gen. Genet. 243, 178-184). Kmapp and Vmax values for the substrate pyruvate were unaffected by any of the mutations giving rise to herbicide resistance. Feedback inhibition by L-valine (L-Val), L-leucine (L-Leu) and L-isoleucine (L-Ile) of acetolactate synthase extracted from wild type and mutants fitted a mixed competitive pattern most closely. Ki values for L-Val, L-Leu and L-Ile inhibition were not significantly different from wild type in extracts from csr1-1, csr1-2, and csr1-3. Ki values were significantly higher than wild type by two- and five-fold, respectively, for csr1-4 with L-Val and L-Leu but not L-Ile. GM4.8 (csr1-4) plants were also highly resistant in their growth to added L-Val and L-Leu.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of canine donor heart preservation temperature on posttransplant left ventricular function and myocardial metabolism.

The generally accepted method of preserving donor heart integrity during transfer is to arrest it with cold cardioplegic solution, then store it in a plastic bag immersed in an iced electrolyte solution. Temperatures between 0 degree C and 4 degrees C are maintained by this method until the heart is transplanted. Although profound hyperthermia best inhibits metabolic processes, it may damage the myocardium. Higher myocardial temperatures may be more advantageous and may result in better preservation. The efficacy of this hypothesis has been investigated in a canine model. The hearts of 40 dogs were isolated, arrested with cold cardioplegia, removed from the animal, and stored at different temperature ranges from 0-3 degree C to 12-15 degrees C for 4 hr. After this time period, the hearts were transplanted into a recipient animal in the cervical heterotopic position. The degree and speed of myocardial functional recovery were monitored by measuring end-systolic elastance generated from pressure-diameter loops using sonomicrometry techniques. Myocardial metabolism was studied simultaneously by monitoring coronary flow, O2, glucose, lactate, pyruvate, and free fatty acid uptakes. The results were compared with those from a control group of hearts transplanted immediately after their removal. Our results indicate that donor heart function was significantly depressed 30 min after heterotopic transplantation, but returned to "control" levels after 2 hr when stored between 0 degrees C and 6 degrees C. Myocardial function remained significantly depressed throughout the 2-hr recovery period in hearts stored at higher (6-15 degrees C) temperatures. Hearts stored at all temperatures continued to extract glucose, lactate, and free fatty acids, but produced significantly higher levels of pyruvate at higher storage temperatures, which may be related to the favored use of free fatty acids. In conclusion, donor hearts stored at colder temperatures for 4 hr regain complete left ventricular function faster than hearts stored at higher temperatures. Our experiments support the presently applied methods of donor heart preservation for 4 hr.

Developmentally related changes in the uptake and metabolism of glucose, glutamine and pyruvate by cattle embryos produced in vitro.

The metabolism of, and retention of radioactivity from, radiolabelled glucose, glutamine and pyruvate were measured in individual cattle embryos produced in vitro from the 2-cell to hatched blastocyst stage. Uptake was defined as the numeric sum of metabolism and retention of radiolabel. Glucose metabolism increased significantly between the 8- and 16-cell stages, but was accompanied by a much larger increase in glucose uptake. Consequently, the proportion of glucose uptake that was metabolized through the pentose-phosphate and Embden-Meyerhof pathways reached a minimum at those stages. From the compacted morula stage onward, the calculated uptake of [14C]glucose was only 25 to 33% of that calculated for [5-3H]glucose. This suggests that 66 to 75% of glucose carbon leaves the embryo, after metabolism to phosphoenolpyruvate, in some form other than CO2. Little or no glucose metabolism by the Krebs cycle could be detected at any stage. Both glutamine and pyruvate metabolism were relatively high at the 2- and 4-cell stages, declined to a minimum at the compacted morula stage and then increased with blastulation. Glutamine metabolism continued to increase with expansion and hatching of the blastocyst, but pyruvate metabolism did not. This suggest that, relative to the activity of the pathway from pyruvate to 2-oxoglutarate, the activity of the 2-oxoglutarate-to-oxaloacetate segment of the Krebs cycle is of increasing significance during expansion and hatching of the cattle blastocyst.

Effects of epinephrine on the net hepatic uptake of lactate, pyruvate, and glycerol in sheep.

Epinephrine caused hyperglycemia in part by increasing gluconeogenesis. However, the mechanism of its gluconeogenic effects has not been studied in ruminants. This study was undertaken to examine the effect of epinephrine on the net hepatic uptake of selected glucose precursors in sheep. The major abdominal blood vessels of the sheep were catheterized in normal and alloxan diabetic sheep. Glucose production, metabolic clearance of glucose, and the hepatic removal of certain glucose precursors were determined before, during, and after epinephrine infusion. Epinephrine increased the hepatic glucose output, the concentrations of lactate and glycerol in plasma, and the net hepatic uptake and fractional hepatic extraction of lactate and glycerol. These effects were independent of changes in the concentrations of insulin and glucagon in plasma. These results show that epinephrine directly stimulates hepatic gluconeogenesis in sheep.

1-[11C]pyruvate turnover in brain and muscle of patients with mitochondrial encephalomyopathy. A study with positron emission tomography (PET).

We examined pyruvate turnover using 1-[11C]pyruvate in the brain and epicranial muscle of 6 patients with mitochondrial encephalomyopathy (MEM), diagnosed by muscle biopsy and mitochondrial enzyme assay. The radioactivity was measured by positron emission tomography (PET). The time-activity curve for 11C in both brain and muscle generated after i.v. injection of 1-[11C]pyruvate consisted of 2 components in normal subjects and patients, i.e. a fast and a slow component which were assumed to represent the aerobic (mitochondrial) and anaerobic (glycolytic) metabolism of pyruvate, respectively. In the brain and muscle of patients, the aerobic component was smaller and the anaerobic larger than in normals. The extent of this abnormality seemed to reflect the severity of the disease. The same slight abnormality for [11C]pyruvate turnover was also observed in the brain of MEM patients who were without cerebral symptoms. Cerebral blood flow (CBF) and cerebral oxygen consumption (CMRO2) of most patients were lower than those of normals, and the oxygen extraction fraction (OEF) was decreased in many patients.