Cardiac and noncardiac biomarkers in patients undergoing anthracycline chemotherapy - a prospective analysis

BACKGROUND

Biomarkers represent a potential tool to identify individuals at risk for anthracycline-induced cardiotoxicity (AICT) prior to symptom onset or left ventricular dysfunction.

METHODS

This study examined the levels of cardiac and noncardiac biomarkers before, after the last dose of, and 3-6 months after completion of doxorubicin chemotherapy. Cardiac biomarkers included 5th generation high-sensitivity cardiac troponin T (cTnT), N-terminal pro-brain natriuretic peptide, growth/differentiation factor-15 (GDF-15), and soluble suppression of tumorigenesis-2 (sST2). Noncardiac biomarkers included activated caspase-1 (CASP-1), activated caspase-3, C-reactive protein, tumor necrosis factor-α, myeloperoxidase (MPO), galectin-3, and 8-hydroxy-2'-deoxyguanosine. Echocardiographic data (LVEF and LVGLS) were obtained at pre- and post-chemotherapy. Subanalysis examined interval changes in biomarkers among high (cumulative doxorubicin dose ≥ 250 mg/m²) and low exposure groups.

RESULTS

The cardiac biomarkers cTnT, GDF-15, and sST2 and the noncardiac biomarkers CASP-1 and MPO demonstrated significant changes over time. cTnT and GDF-15 levels increased after anthracycline exposure, while CASP-1 and MPO decreased significantly. Subanalysis by cumulative dose did not demonstrate a larger increase in any biomarker in the high-dose group.

CONCLUSIONS

The results identify biomarkers with significant interval changes in response to anthracycline therapy. Further research is needed to understand the clinical utility of these novel biomarkers.

Abstract 94: Increased P450 Aromatase Level in Post-menopausal Women After an Acute Ischemic Stroke

Background: Ischemic stroke is a sexually dimorphic disease. Sex differences in stroke have been attributed to neuroprotective effects of estrogen, yet most clinical trials of estrogen supplementation have shown detrimental effects. The role of sex hormones in stroke is still a subject of debate. Aromatization of testosterone to estradiol in neural tissue leads to sexual differentiation. Emerging data suggests similar aromatase activity in response to brain injury, as increased aromatase expression is seen in ischemic penumbra in animals. Administration of aromatase inhibitors exacerbates damage in experimental stroke models. However, studies on sex steroids in humans are sorely lacking. Objective of this study was to investigate the contributions of sex steroids to the etiology of sex differences in stroke .

Methods: 253 patients admitted to Hartford Hospital for focal neurological deficit were consented for 24hour blood draw from symptom onset. Stroke was confirmed by CTscan/MRI brain. Patients with intracerebral or subarachnoid hemorrhage, age<56 years, were excluded from the study. Controls were patients with transient ischemic attack/seizure. ELISA was run for estradiol, testosterone &P450 aromatase levels in serum.

Results: In age matched men & women, no difference in estradiol levels was seen. For testosterone, main effect of sex, F(1,3)=26,p<0.001 & sex by stroke interaction F(1,3)=4.7,p<0.03 was seen. There was a significant effect of stroke, F(1,3)=9.3,p<0.003 & sex by stroke interaction, F(1,3)=5.8,p<0.01 in aromatase levels (*).

Conclusions: Aromatase levels increase in post-menopausal women after acute ischemic stroke. This may indicate increased aromatase activity as testosterone levels also decreased as compared with controls. Local production of estradiol may occur in the injured female brain mediated by aromatase as seen in prior animal studies. Ongoing work will assess functional outcomes and correlation with hormonal levels.

Muscle phosphorylase kinase deficiency: a neutral metabolic variant or a disease?

OBJECTIVE

To examine metabolism during exercise in 2 patients with muscle phosphorylase kinase (PHK) deficiency and to further define the phenotype of this rare glycogen storage disease (GSD).

METHODS

Patient 1 (39 years old) had mild exercise-induced forearm pain, and EMG showed a myopathic pattern. Patient 2 (69 years old) had raised levels of creatine kinase (CK) for more than 6 months after statin treatment. Both patients had increased glycogen levels in muscle and PHK activity <11% of normal. Two novel pathogenic nonsense mutations were found in the PHKA1 gene. The metabolic response to anaerobic forearm exercise and aerobic cycle exercise was studied in the patients and 5 healthy subjects.

RESULTS

Ischemic exercise showed a normal 5-fold increase in plasma lactate (peak 5.7 and 6.9 mmol/L) but an exaggerated 5-fold increase in ammonia (peak 197 and 171 μmol/L; control peak range 60-113 μmol/L). An incremental exercise test to exhaustion revealed a blunted lactate response (5.4 and 4.8 mmol/L) vs that for control subjects (9.6 mmol/L; range 7.1-14.3 mmol/L). Fat and carbohydrate oxidation rates at 70% of peak oxygen consumption were normal. None of the patients developed a second wind phenomenon or improved their work capacity with an IV glucose infusion.

CONCLUSION

Our findings demonstrate that muscle PHK deficiency may present as an almost asymptomatic condition, despite a mild impairment of muscle glycogenolysis, raised CK levels, and glycogen accumulation in muscle. The relative preservation of glycogenolysis is probably explained by an alternative activation of myophosphorylase by AMP and P(i) at high exercise intensities.

Natural history of MELAS associated with mitochondrial DNA m.3243A>G genotype

OBJECTIVE

To describe the natural history of clinical and laboratory features associated with the m.3243A>G mitochondrial DNA point mutation. Natural history data are needed to obtain prognostic information and for clinical trial planning.

METHODS

We included 85 matrilineal relatives from 35 families with at least 2 visits in this prospective cohort study. Thirty-one were fully symptomatic with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), and 54 were carrier relatives. Evaluations included standardized questionnaires (medical history and daily living functioning), physical examination, neuropsychological testing, and a battery of imaging and laboratory tests. We evaluated changes in clinical and laboratory features over time and survival. Outcomes are reported over a follow-up period of up to 10.6 years (mean 3.8 ± 2.2 years for patients and 5.5 ± 3.0 for carrier relatives).

RESULTS

Neurologic examination, neuropsychological testing, and daily living scores significantly declined in all patients with MELAS, whereas no significant deterioration occurred in carrier relatives. Cerebral MRI scores declined significantly in patients with MELAS. Magnetic resonance spectroscopy estimates of lactate in the lateral ventricles increased over time, and high lactate was associated with increased mortality. Symptom onset in childhood often was associated with worse outcome. Patients with MELAS had a greater death rate than carrier relatives.

CONCLUSIONS

Patients with MELAS carrying the m.3243A>G mutation show a measurable decline in clinical and imaging outcomes. It is hoped that these data will be helpful in anticipating the disease course and in planning clinical trials for MELAS.

Metabolic disorders of fetal life: glycogenoses and mitochondrial defects of the mitochondrial respiratory chain

Two major groups of inborn errors of energy metabolism are reviewed -glycogenoses and defects of the mitochondrial respiratory chain - to see how often these disorders present in fetal life or neonatally. After some general considerations on energy metabolism in the pre- and postnatal development of the human infant, different glycogen storage diseases and mitochondrial encephalomyopathies are surveyed. General conclusions are that: (i) disorders of glycogen metabolism are more likely to cause 'fetal disease' than defects of the respiratory chain; (ii) mitochondrial encephalomyopathies, especially those due to defects of the nuclear genome, are frequent causes of neonatal or infantile diseases, typically Leigh syndrome, but usually do not cause fetal distress; (iii) notable exceptions include mutations in the complex III assembly gene BCS1L resulting in the GRACILE syndrome (growth retardation, aminoaciduria, cholestasis, iron overload, lactic acidosis, and early death), and defects of mitochondrial protein synthesis, which are the 'new frontier' in mitochondrial translational research.

Biochemical evaluation of mitochondrial respiratory chain enzymes in canine skeletal muscle

OBJECTIVE

To perform respiratory chain enzymatic activity assays on canine skeletal muscle biopsy specimens and establish reference range values of skeletal muscle enzyme activities for dogs.

SAMPLE POPULATION

Biopsy specimens from the vastus lateralis muscle were obtained from 24 dogs (8 sexually intact males and 14 sexually intact females) ranging from 15 months to 6 years of age.

PROCEDURE

Mean values of citrate synthase, cytochrome-c oxidase, succinate dehydrogenase, succinate dehydrogenase-cytochrome-c reductase, nicotinamide adenine dinucleotide (NADH) dehydrogenase, and NADH dehydrogenase-cytochrome-c reductase activities were established by use of 6 standard spectrophotometric assays for respiratory chain enzyme analysis.

RESULTS

Compared with published data for skeletal muscle enzyme activities in humans, skeletal muscle enzyme activities in dogs were 2- to 4-fold higher. Additionally, citrate synthase activity, a marker for mitochondrial volume, was positively correlated with age in dogs, suggesting that mitochondrial volume increases with age, although no apparent change in respiratory chain enzymatic activity with an increase in age was found.

CONCLUSIONS AND CLINICAL RELEVANCE

Reference range values for skeletal muscle enzyme activities of dogs are needed to accurately interpret results of respiratory chain enzymatic activity assays. During investigation of metabolic myopathies, if skeletal muscle biopsy specimens are evaluated for respiratory chain enzyme kinetics, they should be performed and evaluated in concert with skeletal muscle biopsy specimens from clinically normal animals of the same species.

Navajo neurohepatopathy: a mitochondrial DNA depletion syndrome?

Navajo neurohepatopathy (NNH) is an autosomal recessive disease of full-blooded Navajo children living in the Navajo Reservation of southwestern United States. Clinical features of NNH include peripheral and central nervous system involvement, acral mutilation, corneal scarring or ulceration, liver failure, and metabolic and immunologic derangement. The cause of NNH is unknown, but the clinical features of NNH are similar to those of patients with mitochondrial DNA (mtDNA) depletion. Therefore, we studied mtDNA concentration in the liver from 2 patients with NNH. Using histochemical, biochemical, and molecular techniques, we found evidence of mtDNA depletion, and we propose that the primary defect in NNH is in the nuclear regulation of mtDNA copy number.

Mitochondrial DNA depletion, near-fatal metabolic acidosis, and liver failure in an HIV-infected child treated with combination antiretroviral therapy

A child with controlled human immunodeficiency virus infection presented with neurologic deterioration, lactic acidosis, and organic aciduria. Muscle biopsy revealed abnormal mitochondrial (mt) morphology, reduced mt enzyme activities, and mtDNA depletion. After adjustment of antiretroviral therapy to a regimen free of nucleoside analogs, marked improvement was seen in clinical status and mt abnormalities.

A new mutation in the regulatory domain of the myophosphorylase gene affecting protein dimer contact

We have identified a novel missense mutation in the myophosphorylase gene in a Spanish patient with McArdle's disease. The patient was homozygous for a T-to-C transition at codon 115 (L115P) in exon 3, which changed an encoded leucine (CUG) to a proline (CCG). This is the first mutation to be described in exon 3 and in a protein domain related to dimer contact. These data further emphasize the importance of private mutations in McArdle's disease, some of which are associated with specific ethnic groups.

Deficient muscle carnitine transport in primary carnitine deficiency

Primary carnitine deficiency is associated with deficient blood and tissue carnitine concentrations. The clinical syndrome is dominated by heart and skeletal muscle symptoms, and the clinical response to oral carnitine supplementation is life-saving. Carnitine uptake has been shown to be defective in cultured skin fibroblasts and leukocytes obtained from patients with this condition. We report a new case of primary carnitine deficiency and offer direct evidence consistent with an impairment of carnitine uptake in differentiating muscle culture. The patient presented with severe and progressive cardiomyopathy and moderate proximal limb weakness. Plasma and muscle carnitine levels were very low, and the maximal rate of carnitine transport in cultured fibroblasts was deficient. An asymptomatic sister with intermediate levels of carnitine in plasma showed partially deficient carnitine uptake in fibroblasts, indicating heterozygosity. The patient's condition improved dramatically with oral carnitine therapy. Further studies were performed in cultured muscle cells at different stages of maturation, which demonstrated deficient maximal rates of carnitine uptake. Our findings are consistent with the concept that primary carnitine deficiency is the result of a generalized defect involving carnitine transport across tissue membranes.

Molecular basis of muscle phosphoglycerate mutase (PGAM-M) deficiency in the Italian kindred

Human muscle phosphoglycerate mutase (PGAM-M) deficiency is associated with exercise intolerance, muscle cramps, chronic serum CK elevation, and recurrent episodes of myoglobinuria. Ten patients have been described: 7 African Americans, 1 African, and 2 Caucasians from the Italian kindred described here. Molecular genetic analysis has revealed three different mutations in the PGAM-M gene. The propositus of the Italian family was homozygous for a unique point mutation at codon 90 in exon 1, a C-to-T transition converting an encoded arginine to tryptophan. His sister, who had similar complaints, was also homozygous for this mutation while the paternal grandfather, both parents, a brother and a nephew of the propositus were heterozygous for the mutation. Our studies exclude that PGAM-M deficiency is limited to African Americans, and suggest that the molecular heterogeneity of this rare disorder may be due to a "founder effect" in different ethnic groups.

Polyglucosan body disease

Adult polyglucosan disease has been described in 15 cases. All had signs of peripheral neuropathy, upper motor neuron signs, and 12 of the 15 had sphincter problems. Dementia was prominent in 8 of 15 cases. We reported 2 cases that contained these clinical features. Electrophysiological studies showed axonal neuropathy. Somatosensory evoked potentials on the second patient were abnormal. Sural nerve biopsy showed clusters of polyglucosan bodies. Although the presence of polyglucosan bodies in biopsy is nonspecific, the number as well as the clinical features are necessary to make the diagnosis. Branching enzyme activity in muscle extracts of the muscles were normal. Hence, a specific enzyme abnormality is not yet known.

Cell fractionation studies indicate that dystrophin is a protein of surface membranes of skeletal muscle

We studied the subcellular localization of dystrophin in rabbit skeletal muscle. In Western-blot analysis of membrane preparations, dystrophin was associated with the sarcolemmal fraction, as indicated by cholesterol content and co-purification with ouabain-binding activity and beta-adrenergic receptor. Dystrophin was also found with junctional T-tubules, but not with 'free' T-tubules, longitudinal portions or terminal cisternae of the sarcoplasmic reticulum. Dystrophin was not solubilized by high salt solutions, but it was solubilized by low concentrations of detergents (Triton X-100 and deoxycholate), suggesting that it is a peripheral membrane protein.

Immunocytochemical study of dystrophin in muscle cultures from patients with Duchenne muscular dystrophy and unaffected control patients

Using immunocytochemical methods, the localization of dystrophin, the gene product affected in Duchenne muscular dystrophy (DMD) in aneural, differentiating human muscle cultures, was studied. Dystrophin was not demonstrable in undifferentiated myoblasts from control patients and from two patients with DMD. After myoblast fusion, the protein was found in circumscribed sarcoplasmic patches, in the perinuclear area, and along the surface of all normal multinucleate myotubes, with more mature myotubes showing predominantly sarcolemmal distribution. There was no staining in myotubes from one DMD patient and only faint diffuse fluorescence in myotubes from the second affected boy, however. These data provide further evidence that dystrophin is a sarcolemma-associated protein, that it is developmentally regulated, and that it is absent or greatly reduced in quantity in skeletal muscle cultures from patients with DMD.

Histiocytoid cardiomyopathy of infancy: deficiency of reducible cytochrome b in heart mitochondria

A 3-week-old girl with failure to thrive and cardiomegaly died of cardiac arrest at age 4 weeks. Morphologic studies of the heart showed enlarged muscle fibers with large accumulations of mitochondria, characteristic of histiocytoid cardiomyopathy. Biochemical studies showed markedly decreased succinate-cytochrome c reductase and rotenone-sensitive NADH-cytochrome c reductase activities, while other mitochondrial enzymes were normal. In isolated mitochondria, cytochrome spectra showed a severe defect of reducible cytochrome b and a less marked defect of cytochrome cc1, while the content of cytochrome aa3 (cytochrome c oxidase) was normal. Histiocytoid cardiomyopathy appears to be due to a defect of complex III (reduced coenzyme Q-cytochrome c reductase) in the respiratory chain of heart mitochondria.

Lactic acidosis and mitochondrial myopathy associated with deficiency of several components of complex III of the respiratory chain

We have studied a 17-year-old girl with lactic acidosis (3-18 mEq/liter) and progressive muscle weakness since 9 years of age. Morphological findings in muscle were of a typical ragged red myopathy with multiple collections of bizarre mitochondria, some containing paracrystalline inclusions. The carnitine content of serum and muscle was normal, as were the activities of carnitine palmitoyltransferase, carnitine octanoyltransferase, and carnitine acetyltransferase in the patient's muscle. Measurement of the enzymes of oxidative phosphorylation in both crude muscle homogenates and mitochondrial fractions showed close to normal activities of cytochrome c oxidase, succinate dehydrogenase, and ATPase. In contrast, succinate cytochrome c reductase activity was greatly reduced in the patient, being 0.035 mumol/min/g tissue in whole muscle (controls 1.16 +/- 0.47 mumol/min/g tissue) and 8 nmol/min/mg protein in the mitochondria (control, 340 nmol/min/mg protein). Rotenonesensitive NADH-cytochrome c reductase was also undetectable in the patient's mitochondria. Spectral analysis of cytochromes showed decrease of reducible cytochrome b to 16% of the control. These results indicate a defect of ubiquinol-cytochrome c reductase or the cytochrome bc1 segment (complex III) of the electron transport chain. Antibody-binding studies of the individual components of complex III showed additional deficiencies of core proteins I and II and peptide VI, indicating a more widespread defect of complex III than was evident from spectral analysis and enzyme activity measurements alone. Urine organic acid analysis after fasting and following a medium chain triglyceride load showed unusually high levels of lactate and 3-hydroxybutyrate, lower than expected levels of acetoacetate and dicarboxylic acids, and the presence of several other metabolites suggesting a disturbed citric acid cycle and redox state.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of the molecular lesions in inherited phosphofructokinase deficiency

Human phosphofructokinase (PFK; EC 2.7.1.11) exists in tetrameric isozymic forms. Muscle and liver contain the homotetramers M4 and L4, whereas erythrocytes contain five isozymes composed of M (muscle) and L (liver) subunits, i.e., M4, M3L, M2L2, ML3, and L4. Inherited defects of erythrocyte PFK are usually partial and are described in association with heterogeneous clinical syndromes. To define the molecular basis and pathogenesis of this enzymopathy, we investigated four unrelated individuals manifesting myopathy and hemolysis (glycogenosis type VII), isolated hemolysis, or no symptoms at all. The three symptomatic patients showed high-normal hemoglobin levels, despite hemolysis and early-onset hyperuricemia. They showed total lack of muscle-type PFK and suffered from exertional myopathy of varying severity. In the erythrocytes, a metabolic crossover was evident at the PFK step: the levels of hexose monophosphates were elevated and those of 2,3-diphosphoglycerate (2,3-DPG) were depressed, causing strikingly increased hemoglobin-oxygen affinity. In all cases, the residual erythrocyte PFK consisted exclusively of L4 isozyme, indicating homozygosity for the deficiency of the catalytically active M subunit. However, presence of immunoreactive M subunit was shown in cultured fibroblasts by indirect immunofluorescence with monoclonal anti-M antibody. The fourth individual was completely asymptomatic, had normal erythrocyte metabolism, and had no evidence of hemolysis. His residual erythrocyte PFK showed a striking decrease of the L4, ML3, and M2L2 isozymes, secondary to a mutant unstable L subunit. Identical alterations of erythrocyte PFK were found in his asymptomatic son, indicating heterozygosity for the mutant unstable L subunit in this kindred. These studies show that, except for the varying severity of the myopathic symptoms, glycogenosis type VII has highly uniform clinical and biochemical features and results from homozygosity for mutant inactive M subunit(s). The absence of anemia despite hemolysis may be explained by the low 2,3-DPG levels. The hyperuricemia may result from hyperactivity of the hexose monophosphate shunt. In contrast, the clinically silent carrier state results from heterozygosity for mutant M or L subunit. Of the two, the M subunit appears to be more critical for adequate glycolytic flux in the erythrocyte, since its absence is correlated with hemolysis.

Late-onset acid maltase deficiency. Biochemical studies of leukocytes

The activities of acid and neutral maltase were measured in lymphocytes, granulocytes, and platelets isolated from controls and from 5 patients with late-onset acid maltase deficiency (AMD). Lymphocytes from patients had markedly decreased activity of acid maltase and elevated neutral/acid ratios. In granulocytes, acid maltase was also lower than in controls, but significant activity was retained at pH 4: neutral/acid ratios were consistently elevated. Normal platelets had low acid and high neutral maltase activities: both enzyme activities varied within wide ranges and patients could not be distinguished from controls. The variable proportion of different cell types in unfractionated leukocyte preparations may yield unreliable values when used for detection of AMD. However, lymphocytes isolated from 20 ml of blood provide a readily accessible and reliable source of tissue for accurate diagnosis.

Active transport of carnitine into skeletal muscle

Skeletal muscle carnitine concentration exceeds plasma carnitine concentration. To determine whether this concentration gradient is maintained by active transport we studied rat soleus and extensor digitorum longus muscles. Observations consistent with the existence of an active transport mechanism were that the soleus accumulated carnitine linearly for 3 hours of incubation to exceed a distribution ratio of 1; the temperature coefficient for carnitine accumulation between 33 degrees C and 43 degrees C was 2.0; anaerobic incubation reduced carnitine accumulation by 30 percent; and the rate of carnitine accumulation was saturated at high substrate concentrations and competitively inhibited by gamma-butyrobetaine. The Km for carnitine of the carnitine transport mechanism of the soleus muscle was 0.259 mM and of the extensor digitorum longus muscle, 0.585 mM. The greater affinity of the soleus transport mechanism may explain the difference in carnitine transport by red and white muscle in intact animals. A defect in active transport of carnitine may be involved in the pathogenesis of some human myopathies characterized by excessive lipid storage and in diphtheritic cardiomyopathy.

Corticosteroid-responsive skeletal muscle disease associated with partial carnitine deficiency: studies of liver and metabolic alterations

A patient with progressive skeletal muscle weakness had lipid-containing vacuoles in type I muscle fibers and partial carnitine deficiency of skeletal muscle. Results of certain liver function tests were abnormal, marked morphologic abnormalities of liver were detected, and a reduced cyclic adenosine 3',5'-monophosphate response to glucagon was present. After the oral administration of prednisone the patient exhibited gradual but striking clinical improvement, skeletal muscle fiber vacuoles could no longer be demonstrated, and the glucagon-provoked cyclic AMP response reverted to normal, but liver abnormalities persisted. At the same time utilization by skeletal muscle of long-chain fatty acids, pyruvate and beta-hydroxybutyrate was depressed. It is possible that the involvement of skeletal muscles was due to an inability of carnitine to attach to or to penetrate the sarcolemmal membrane. Some of the derangement, perhaps related to liver malfunction, was apparently corrected by the oral administration of prednisone although skeletal muscle metabolism remained impaired.

Hereditary carnitine deficiency of muscle

An eight-year-old boy with slowly progressive muscle weakness was found to have Oil red O positive vacuoles in predominanty type i muscle fibers. Subsequent studies demonstrated markedly reduced skeletal muscle carnitine (0.24 mumoles per gram; normal 1.64 to 3.34). Serum carnitine was normal. Although both parents were clinically normal, muscle carnitine levels were low in both (mother 0.60; father 0.90 mumoles). There was no clinical evidence of cardiac disease but the patient had ventricular hypertrophy by electrocardiography, vectorcardiography, and echocardiography. Treatment with prednisone resulted in clinical improvement but no change in muscle histology. Our studies suggest that the carnitine deficiency of muscle in this case may be due to impaired carnitine entry into muscle and that this form of disease can be inherited as an autosomal recessive disorder.