Summary
Background
Recurrent malignant brain tumors (RMBTs) carry a poor prognosis. Dichloroacetate (DCA) activates mitochondrial oxidative metabolism and has shown activity against several human ...cancers.
Design
We conducted an open-label study of oral DCA in 15 adults with recurrent WHO grade III – IV gliomas or metastases from a primary cancer outside the central nervous system. The primary objective was detection of a dose limiting toxicity for RMBTs at 4 weeks of treatment, defined as any grade 4 or 5 toxicity, or grade 3 toxicity directly attributable to DCA, based on the National Cancer Institute’s Common Toxicity Criteria for Adverse Events, version 4.0. Secondary objectives involved safety, tolerability and hypothesis-generating data on disease status. Dosing was based on haplotype variation in glutathione transferase zeta 1/maleylacetoacetate isomerase (GSTZ1/MAAI), which participates in DCA and tyrosine catabolism.
Results
Eight patients completed at least 1 four week cycle. During this time, no dose-limiting toxicities occurred. No patient withdrew because of lack of tolerance to DCA, although 2 subjects experienced grade 0–1 distal parasthesias that led to elective withdrawal and/or dose-adjustment. All subjects completing at least 1 four week cycle remained clinically stable during this time and remained on DCA for an average of 75.5 days (range 26–312).
Conclusions
Chronic, oral DCA is feasible and well-tolerated in patients with recurrent malignant gliomas and other tumors metastatic to the brain using the dose range established for metabolic diseases. The importance of genetic-based dosing is confirmed and should be incorporated into future trials of chronic DCA administration.
Our recent studies have revealed that among the 10 different commonly used adeno-associated virus (AAV) serotypes, AAV3 vectors transduce human liver cancer cells extremely efficiently because these ...cells express high levels of human hepatocyte growth factor receptor (hHGFR), and AAV3 utilizes hHGFR as a cellular co-receptor for viral entry. In this report, we provide further evidence that both extracellular as well as intracellular kinase domains of hHGFR are involved in AAV3 vector entry and AAV3-mediated transgene expression. We also document that AAV3 vectors are targeted for degradation by the host cell proteasome machinery, and that site-directed mutagenesis of surface-exposed tyrosine (Y) to phenylalanine (F) residues on AAV3 capsids significantly improves the transduction efficiency of Y701F, Y705F and Y731F mutant AAV3 vectors. The transduction efficiency of the Y705+731F double-mutant vector is significantly higher than each of the single mutants in liver cancer cells in vitro. In immunodeficient mouse xenograft models, direct intratumoral injection of AAV3 vectors also led to high-efficiency transduction of human liver tumor cells in vivo. We also document here that the optimized tyrosine-mutant AAV3 vectors lead to increased transduction efficiency following both intratumoral and tail-vein injections in vivo. The optimized tyrosine-mutant AAV3 serotype vectors containing proapoptotic genes should prove useful for the potential gene therapy of human liver cancers.
Dichloroacetate (DCA) is biotransformed by glutathione transferase zeta 1 (GSTZ1), a bifunctional enzyme that, as maleylacetoacetate isomerase (MAAI), catalyzes the penultimate step in tyrosine ...catabolism. DCA inhibits GSTZ1/MAAI, leading to delayed plasma drug clearance and to accumulation of potentially toxic tyrosine intermediates. Haplotype variability in GSTZ1 influences short‐term DCA kinetics in healthy adults, but the impact of genotype in children treated chronically with DCA is unknown. Drug kinetics was studied in 17 children and adolescents with congenital mitochondrial diseases administered 1,2‐13C‐DCA. Plasma drug half‐life and trough levels varied 3–6‐fold, depending on GSTZ1/MAAI haplotype and correlated directly with urinary maleylacetone, a substrate for MAAI. However, chronic DCA exposure did not lead to progressive accumulation of plasma drug concentration; instead, kinetics parameters plateaued, consistent with the hypothesis that equipoise is established between the inhibitory effect of DCA on GSTZ1/MAAI and new enzyme synthesis. GSTZ1/MAAI haplotype variability affects DCA kinetics and biotransformation. However, these differences appear to be stable in most individuals and are not associated with DCA plasma accumulation or drug‐associated toxicity in young children.
Exercise Training, Without Weight Loss, Increases Insulin Sensitivity and Postheparin Plasma Lipase Activity in Previously
Sedentary Adults
Glen E. Duncan , PHD, RCEPSM 1 ,
Michael G. Perri , PHD 2 ,
...Douglas W. Theriaque , MS 3 ,
Alan D. Hutson , PHD 4 ,
Robert H. Eckel , MD 5 and
Peter W. Stacpoole , PHD, MD 1 6
1 Department of Medicine (Division of Endocrinology and Metabolism), University of Florida, Gainesville, Florida
2 Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida
3 General Clinical Research Center, University of Florida, Gainesville, Florida
4 Department of Biostatistics, University of Florida, Gainesville, Florida
5 Department of Medicine (Division of Endocrinology, Metabolism and Diabetes), University of Colorado Health Sciences Center,
Denver, Colorado
6 Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida
Abstract
OBJECTIVE —To determine the effects of exercise, without weight loss, on insulin sensitivity (S I ), postheparin plasma lipase activity (PHPL), intravenous fat clearance rate (K 2 ), and fasting lipids in sedentary adults.
RESEARCH DESIGN AND METHODS —At baseline and after 6 months of walk training (intensity 45–55 or 65–75% heart rate reserve, frequency 3–4 or 5–7 days/week,
duration 30 min/session), anthropometric indexes, S I , PHPL, K 2 , and fasting lipids were measured in 18 sedentary adults (12 women, 6 men; 51.9 ± 5.8 years of age, BMI 28.9 ± 4.6 kg/m 2 ).
RESULTS —Exercise increased S I (2.54 ± 2.74 vs. 4.41 ± 3.30 μU · ml −1 · min −1 , P < 0.005) and both lipoprotein lipase (LPL) (1,890 ± 1,380 vs. 4,926 ± 1,858 nEq free fatty acid FFA · ml −1 · h −1 ) and hepatic lipase (HL) activities (3,326 ± 1,605 vs. 4,636 ± 1,636 nEq FFA · ml −1 · h −1 ) (both P < 0.001), without altering BMI, waist circumference, K 2 , or fasting lipids. Correlations between changes in LPL and the total:HDL cholesterol ratio ( r = −0.54) and changes in the LPL:HL ratio and waist circumference ( r = −0.50) were significant ( P < 0.05).
CONCLUSIONS —Exercise, without weight loss, increases S I and PHPL activity in previously sedentary adults, without changing K 2 or fasting lipid levels. Furthermore, increased LPL is associated with a decreased total:HDL ratio, and an increased LPL:HL
ratio is associated with a decreased waist circumference. Therefore, even modest amounts of exercise in the absence of weight
loss positively affect markers of glucose and fat metabolism in previously sedentary, middle-aged adults.
GCRC, General Clinical Research Center
HL, hepatic lipase
IR, insulin resistance
K2, intravenous fat clearance rate
LPL, lipoprotein lipase
PHPL, postheparin plasma lipase activity
SI, insulin sensitivity
TG, triglyceride
Footnotes
Address correspondence and reprint requests to Glen E. Duncan, PhD, RCEP SM , Box 100226 JHMHSC, University of Florida, Gainesville, FL 32610-0226. E-mail: gduncan{at}ufl.edu .
Received for publication 18 August 2002 and accepted in revised form 17 October 2002.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
See accompanying editorial, p. 944.
DIABETES CARE
This article critically reviews the pharmacologic effects of the investigational drug dichloroacetate (DCA), which activates the mitochondrial pyruvate dehydrogenase enzyme complex in cardiac tissue ...and thus preferentially facilitates aerobic oxidation of carbohydrate over fatty acids. The pharmacologic effects of DCA are compared with other interventions, such as glucose plus insulin, inhibitors of long chain fatty acid oxidation and adenosine, that are also thought to exert their therapeutic effects by altering myocardial energy metabolism. Short-term clinical and laboratory experiments demonstrate that intravenous DCA rapidly stimulates pyruvate dehydrogenase enzyme complex activity and, therefore, aerobic glucose oxidation in myocardial cells. Typically these effects are associated with suppression of myocardial long chain fatty acid metabolism and increased left ventricular stroke work and cardiac ouput without changes in coronary blood flow or myocardial oxygen consumption. Although long-term studies are lacking, shart-term parenteral administration of DCA appears to be safe and capable of significantly improving myocardial function in conditions of limited oxygen availability by increasing the efficient conversion of myocardial substrate fuels into energy.
Open-label studies indicate that oral dichloroacetate (DCA) may be effective in treating patients with congenital lactic acidosis. We tested this hypothesis by conducting the first double-blind, ...randomized, control trial of DCA in this disease.
Forty-three patients who ranged in age from 0.9 to 19 years were enrolled. All patients had persistent or intermittent hyperlactatemia, and most had severe psychomotor delay. Eleven patients had pyruvate dehydrogenase deficiency, 25 patients had 1 or more defects in enzymes of the respiratory chain, and 7 patients had a mutation in mitochondrial DNA. Patients were preconditioned on placebo for 6 months and then were randomly assigned to receive an additional 6 months of placebo or DCA, at a dose of 12.5 mg/kg every 12 hours. The primary outcome results were (1) a Global Assessment of Treatment Efficacy, which incorporated tests of neuromuscular and behavioral function and quality of life; (2) linear growth; (3) blood lactate concentration in the fasted state and after a carbohydrate meal; (4) frequency and severity of intercurrent illnesses and hospitalizations; and (5) safety, including tests of liver and peripheral nerve function.
There were no significant differences in Global Assessment of Treatment Efficacy scores, linear growth, or the frequency or severity of intercurrent illnesses. DCA significantly decreased the rise in blood lactate caused by carbohydrate feeding. Chronic DCA administration was associated with a fall in plasma clearance of the drug and with a rise in the urinary excretion of the tyrosine catabolite maleylacetone and the heme precursor delta-aminolevulinate.
In this highly heterogeneous population of children with congenital lactic acidosis, oral DCA for 6 months was well tolerated and blunted the postprandial increase in circulating lactate. However, it did not improve neurologic or other measures of clinical outcome.
One-carbon metabolism involves both mitochondrial and cytosolic forms of folate-dependent enzymes in mammalian cells, but few in vivo data exist to characterize the biochemical processes involved.
We ...conducted a stable-isotopic investigation to determine the fates of exogenous serine and serine-derived one-carbon units in homocysteine remethylation in hepatic and whole-body metabolism.
A healthy man aged 23 y was administered 2,3,3-(2)H(3)serine and 5,5,5-(2)H(3)leucine by intravenous primed, constant infusion. Serial plasma samples were analyzed to determine the isotopic enrichment of free glycine, serine, leucine, methionine, and cystathionine. VLDL apolipoprotein B-100 served as an index of liver free amino acid labeling.
(2)H(1)Methionine and (2)H(2)methionine were labeled through homocysteine remethylation. We propose that (2)H(2)methionine occurs by remethylation with (2)H(2)methyl groups (as 5-methyltetrahydrofolate) formed only from cytosolic processing of (2)H(3)serine, whereas (2)H(1)methionine is formed with labeled one-carbon units from mitochondrial oxidation of C-3 serine to (2)H(1)formate to yield cytosolic (2)H(1)methyl groups. The labeling pattern of cystathionine formed from homocysteine and labeled serine suggests that cystathionine is derived mainly from a serine pool different from that used in apolipoprotein B-100 synthesis.
The appearance of both (2)H(1)- and (2)H(2)methionine forms indicates that both cytosolic and mitochondrial metabolism of exogenous serine generates carbon units in vivo for methyl group production and homocysteine remethylation. This study also showed the utility of serine infusion and indicated functional roles of cytosolic and mitochondrial compartments in one-carbon metabolism.
We determined acute and chronic effects of dichloroacetate (DCA) on maximal (MAX) and submaximal (SUB) exercise responses in patients with abnormal mitochondrial energetics. Subjects (n = 9) ...completed a MAX treadmill bout 1 h after ingesting 25 mg/kg DCA or placebo (PL). A 15-min SUB bout was completed the next day while receiving the same treatment. After a 1-d washout, MAX and SUB were repeated while receiving the alternate treatment (acute). Gas exchange and heart rate were measured throughout all tests. Blood lactate (Bla) was measured 0, 3, and 10 min after MAX, and 5, 10, and 15 min during SUB. MAX and SUB were repeated after 3 months of daily DCA or PL. After a 2-wk washout, a final MAX and SUB were completed after 3 months of alternate treatment (chronic). Average Bla during SUB was lower (P < 0.05) during both acute (1.99 ± 1.10 vs. 2.49 ± 1.52 mmol/liter) and chronic (1.71 ± 1.37 vs. 2.39 ± 1.32 mmol/liter) DCA vs. PL despite similar exercise intensities between conditions (∼75 and 70% maximal exercise capacity during acute and chronic treatment). Thus, although DCA does not alter MAX responses, acute and chronic DCA attenuate the Bla response to moderate exercise in patients with abnormal mitochondrial energetics.
Dichloroacetate (DCA) is a xenobiotic of interest to both environmental toxicologists and clinicians. The chemical is a product of water chlorination and of the metabolism of various drugs and ...industrial chemicals. Its accumulation in groundwater and at certain Superfund sites is considered a potential health hazard. However, concern about DCA toxicity is predicated mainly on data obtained in inbred rodent strains administered DCA at doses thousands of times higher than those to which humans are usually exposed. In these animals, chronic administration of DCA induces hepatotoxicity and neoplasia. Ironically, the DCA doses used in animal toxicology experiments are very similar to those used clinically for the chronic or acute treatment of several acquired or hereditary metabolic or cardiovascular diseases. As a medicinal, DCA is generally well tolerated and stimulates the activity of the mitochondrial pyruvate dehydrogenase enzyme complex, resulting in increased oxidation of glucose and lactate and an amelioration of lactic acidosis. By this mechanism, the drug may also enhance cellular energy metabolism. DCA is dehalogenated in vivo to monochloroacetate and glyoxylate, from which it can be further catabolized to glycolate, glycine, oxalate, and carbon dioxide. It remains to be determined whether important differences in its metabolism and toxicology exist in humans between environmentally and clinically relevant doses.
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