Skeletal muscle mitochondrial ATP production rate and walking performance in peripheral arterial disease

This study tested the hypotheses that skeletal muscle mitochondrial ATP production rate (MAPR) is impaired in patients with peripheral arterial disease (PAD) and that it relates positively to their walking performances. Seven untrained patients, eight exercise-trained patients and 11 healthy controls completed a maximal walking test and had muscle sampled from the gastrocnemius medialis muscle. Muscle was analysed for its MAPR in the presence of pyruvate, palmitoyl-L-carnitine or both, as well as citrate synthase (CS) activity. MAPRs were not different between untrained PAD and controls. In contrast, MAPRs (pyruvate) were significantly higher in trained PAD vs. controls. MAPR (pyruvate combinations) was also significantly higher in trained than untrained PAD muscle. MAPR and CS activity were highly correlated with walking performance in patients, but not in controls. These data do not support the hypothesis that isolated mitochondria are functionally impaired in PAD and demonstrate that the muscle mitochondrial capacity to oxidize carbohydrate is positively related to walking performance in these patients.

Spermine modulation of the glutamate(NMDA) receptor is differentially responsive to conantokins in normal and Alzheimer's disease human cerebral cortex

The pharmacology of the N -methyl-d-aspartate (NMDA) receptor site was examined in pathologically affected and relatively spared regions of cerebral cortex tissue obtained at autopsy from Alzheimer's disease cases and matched controls. The affinity and density of the [H-3]MK-801 binding site were delineated along with the enhancement of [H-3]MK-801 binding by glutamate and spermine. Maximal enhancement induced by either ligand was regionally variable; glutamate-mediated maximal enhancement was higher in controls than in Alzheimer's cases in pathologically spared regions, whereas spermine-mediated maximal enhancement was higher in controls in areas susceptible to pathological damage. These and other data suggest that the subunit composition of NMDA receptors may be locally variable. Studies with modified conantokin-G (con-G) peptides showed that Ala(7)-con-G had higher affinity than Lys(7)-con-G, and also defined two distinct binding sites in controls. Nevertheless, the affinity for Lys(7)-con-G was higher overall in Alzheimer's brain than in control brain, whereas the reverse was true for Ala(7)-con-G. Over-excitation mediated by specific NMDA receptors might contribute to localized brain damage in Alzheimer's disease. Modified conantokins are useful for identifying the NMDA receptors involved, and may have potential as protective agents.

Use of stress echocardiography to predict mortality in patients with diabetes and known or suspected coronary artery disease

OBJECTIVE - This study sought to determine whether stress echocardiography using exercise (when feasible) or dobutamine echo could be used to predict mortality in patients with diabetes. RESEARCH DESIGN AND METHODS - Stress echo was performed in 937 patients with diabetes (aged 59 +/- 13 years, 529 men) for symptom evaluation (42%) and follow-up of known coronary artery disease (CAD) (58%). Stress echocardiography using exercise was performed in 333 patients able to exercise maximally, and dobutamine echo using a standard dobutamine stress was used in 604 patients. Patients were followed for less than or equal to9 years (mean 3.9 +/- 2.3) for all-cause mortality. RESULTS - Normal studies were obtained in 567 (60%) patients; 29% had resting left ventricular (LV) dysfunction, and 25% had ischemia. Abnormalities were confined to one territory in 183 (20%) patients and to multiple territories in 187 (20%) patients. Death (in 275 [29%] patients) was predicted by referral for pharmacologic stress (hazard ratio [HR] 3.94, P < 0.0001), ischemia (1.77, P <0.0001), age (1.02, P = 0.002), and heart failure (1.54, P = 0.01). The risk of death in patients With a normal scan was 4% per year, and this was associated with age and selection for pharmacologic stress testing. In stepwise models replicating the sequence of clinical evaluation, the predictive power of independent clinical predictors (age, selection for pharmacologic stress, previous infarction, and heart failure; model chi(2) = 104.8) was significantly enhanced by addition of stress echo data (model chi(2) = 122.9). CONCLUSIONS - The results of stress echo are independent predictors of death in diabetic patients with known or suspected CAD.. Ischemia adds risk that is incremental to clinical risks and LV dysfunction.

Prediction of outcomes in hypertensive patients with suspected coronary disease

Stress echocardiography has been shown to improve the diagnosis of coronary artery disease in the presence of hypertension, but its value in prognostic evaluation is unclear. We sought to determine whether stress echocardiography could be used to predict mortality in 2363 patients with hypertension, who were followed for up to 10 years (mean 4.0+/-1.8) for death and revascularization. Stress echocardiograms were normal in 1483 patients (63%), 16% had resting left ventricular (LV) dysfunction alone, and 21% had ischemia. Abnormalities were confined to one territory in 489 patients (21%) and to multiple territories in 365 patients (15%). Cardiac death was less frequent among the patients able to exercise than among those undergoing dobutamine echocardiography (4% versus 7%, P<0.001). The risk of death in patients with a negative stress echocardiogram was <1% per year. Ischemia identified by stress echocardiography was an independent predictor of mortality in those able to exercise (hazard ratio 2.21, 95% confidence intervals 1.10 to 4.43, P=0.0001) as well as those undergoing dobutamine echo (hazard ratio 2.39, 95% confidence intervals 1.53 to 3.75, P=0.0001); other predictors were age, heart failure, resting LV dysfunction, and the Duke treadmill score. In stepwise models replicating the sequence of clinical evaluation, the results of stress echocardiography added prognostic power to models based on clinical and stress-testing variables. Thus, the results of stress echocardiography are an independent predictor of cardiac death in hypertensive patients with known or suspected coronary artery disease, incremental to clinical risks and exercise results.

Lack of association between CYP1A1 polymorphism and Parkinson's disease in a Chinese population

Apart from very few families who have a direct cause from genetic mutation, causes of most Parkinson's disease (PD) remain unclear. Many allelic association studies on polymorphism of different candidate genes have been studied. Although these association studies do not imply a causal relationship, it does warrant further studies to elucidate the pathophysiologic significance. CYP1A1 polymorphisms have been reported to be associated with PD in a Japanese population sample. Since CYP1A1 transforms aromatic hydrocarbons into products that may be neurotoxic and perhaps lead to PD, we therefore undertook a study to look at the possible association of CYP1A1 polymorphism and PD in a Chinese population. Contrary to the Japanese result, we did not find any statistically significant difference between the PD group and the control group in our study with a bigger sample size.

The Cys282Tyr polymorphism in the HFE gene in Australian Parkinson's disease patients

Iron homeostasis is altered in Parkinson's disease (PD). The HFE protein is an important regulator of cellular iron homeostasis and variations within this gene can result in iron overload and the disorder known as hereditary haemochromatosis. We studied the Cys282Tyr single nucleotide polymorphism as a genetic risk factor for PD in two distinct and separately collected cohorts of Australian PD patients and controls. In the combined cohort comprising 438 PD patients and 485 control subjects, we revealed an odds ratio for possession of the 282Tyr allele of 0.61 (95% confidence interval, Cl = 0.42-0.90, P = 0.011) from univariate chi-squared and 0.59 (95% Cl = 0.39-0.90, P = 0.014) after logistic regression analyses (correcting for potential confounding factors). These results suggest that possession of the 282Tyr allele may offer some protection against the development of PD. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Thiazolidinediones and type 2 diabetes: new drugs for an old disease

Thiazolidinediones are a new class of drugs for the treatment of type 2 diabetes, and act by improving insulin sensitivity in adipose tissue, liver and skeletal muscle. Rosiglitazone and pioglitazone are registered for use in monotherapy, and in combination with sulfonylureas and metformin. Pioglitazone is also licensed for use in combination with insulin. There is level II evidence that in patients with inadequate glycaemic control both drugs reduce the level of HbA(1c) and fasting plasma glucose (FPG) when used as monotherapy and in combination with sulfonylurea or metformin or insulin; and both drugs increase levels of HDL and LDL and lower free fatty acid levels, but only pioglitazone significantly lowers triglyceride levels. Both drugs lower fasting insulin and C-peptide levels. In monotherapy, they may be slightly less potent at reducing the level of HbA(1c) than sulfonylureas or metformin. The maximal effect of these agents may not be seen for 6-14 weeks after commencement. Both drugs are well tolerated but liver function must be checked at baseline every second month for the first year, and periodically thereafter. The drugs are currently contraindicated in patients with moderate to severe liver dysfunction and alanine aminotransferase levels more than 2.5 times normal, New York Heart Association III-IV cardiac status, pregnancy, lactation and in children. The main side effects include weight gain, oedema, and mild dilutional anaemia.

Enterohepatic circulation - Physiological, pharmacokinetic and clinical implications

Enterohepatic recycling occurs by biliary excretion and intestinal reabsorption of a solute, sometimes with hepatic conjugation and intestinal deconjugation. Cycling is often associated with multiple peaks and a longer apparent half-life in a plasma concentration-time profile. Factors affecting biliary excretion include drug characteristics (chemical structure, polarity and molecular size), transport across sinusoidal plasma membrane and canniculae membranes, biotransformation and possible reabsorption from intrahepatic bile ductules. Intestinal reabsorption to complete the enterohepatic cycle may depend on hydrolysis of a drug conjugate by gut bacteria. Bioavailability is also affected by the extent of intestinal absorption, gut-wall P-glycoprotein efflux and gut-wall metabolism. Recently, there has been a considerable increase in our understanding of the role of transporters, of gene expression of intestinal and hepatic enzymes, and of hepatic zonation. Drugs, disease and genetics may result in induced or inhibited activity of transporters and metabolising enzymes. Reduced expression of one transporter, for example hepatic canalicular multidrug resistance-associated protein (MRP) 2, is often associated with enhanced expression of others, for example the usually quiescent basolateral efflux MRP3, to limit hepatic toxicity. In addition, physiologically relevant pharmacokinetic models, which describe enterohepatic recirculation in terms of its determinants (such as sporadic gall bladder emptying), have been developed. In general, enterohepatic recirculation may prolong the pharmacological effect of certain drugs and drug metabolites. Of particular importance is the potential amplifying effect of enterohepatic variability in defining differences in the bioavailability, apparent volume of distribution and clearance of a given compound. Genetic abnormalities, disease states, orally administered adsorbents and certain coadministered drugs all affect enterohepatic recycling.

Cationic drug pharmacokinetics in diseased livers determined by fibrosis index, hepatic protein content, microsomal activity, and nature of drug

The disposition kinetics of six cationic drugs in perfused diseased and normal rat livers were determined by multiple indicator dilution and related to the drug physicochemical properties and liver histopathology. A carbon tetrachloride (CCl4)induced acute hepatocellular injury model had a higher fibrosis index (FI), determined by computer-assisted image analysis, than did an alcohol-induced chronic hepatocellular injury model. The alcohol-treated group had the highest hepatic alpha(1)- acid glycoprotein, microsomal protein (MP), and cytochrome P450 (P450) concentrations. Various pharmacokinetic parameters could be related to the octanol-water partition coefficient (log P-app) of the drug as a surrogate for plasma membrane partition coefficient and affinity for MP or P450, the dependence being lower in the CCl4-treated group and higher in the alcohol-treated group relative to controls. Stepwise regression analysis showed that hepatic extraction ratio, permeability-surface area product, tissue-binding constant, intrinsic clearance, partition ratio of influx (k(in)) and efflux rate constant (k(out)), and k(in)/k(out) were related to physicochemical properties of drug (log P-app or pK(a)) and liver histopathology (FI, MP, or P450). In addition, hepatocyte organelle ion trapping of cationic drugs was evident in all groups. It is concluded that fibrosis-inducing hepatic disease effects on cationic drug disposition in the liver may be predicted from drug properties and liver histopathology.

GH treatment in adults with chronic liver disease: A randomized, double-blind, placebo-controlled, cross-over study

Patients with chronic liver disease (CLD) are catabolic and GH-resistant. The effects of supraphysiological recombinant human GH (rhGH; 0.2 IU.kg(-1).d(-1)) treatment in adults with CLD were assessed in a randomized, double-blind, placebo-controlled cross-over trial (4-wk dietary run-in, 4-wk treatment, and 2-wk wash-out phases). Nine adults with mild- to moderate-severity CLD participated (median age, 49 yr; three males and six females; Child's classification A in six and B in three). Biopsy-proven etiologies were: alcohol (four patients), primary biliary cirrhosis (three patients), non-A, non-B, non-C hepatitis (one patient), and cryptogenic (one patient). Treatment with rhGH increased serum IGF-I (median increase over placebo, +93 mug.liter(-1); P = 0.004), IGF-binding protein-3 (+0.9 mg.liter(-1): P = 0.004), and acid labile subunit (+10.7 nM; P = 0.004). Total body potassium (+8.0 g; P = 0.023), body weight (+1.6 kg; P = 0.008), and total body water (by bioelectrical impedance; +4.9 kg; P = 0.004) increased. Resting metabolic rate (+313 ml.kg(-1).min(-1); P = 0.004) and lipid oxidation (+1072.0 kcal.d(-1); P = 0.032) increased. Metabolic changes included increased fasting plasma glucose (+1.2 mm; P = 0.008), insulin (+33.8 mU.liter(-1); P = 0.004), C-peptide (+0.7 nM; P = 0.004), and free-fatty acids (+0.1 mEq.liter(-1); P = 0.04). Clinical side effects included worsening edema and ascites. Hepatocellular function did not change. Therefore, rbGH treatment in CLD: 1) overcame hepatic GH resistance; 2) may have improved whole-body protein catabolism; 3) increased lipolysis and lipid oxidation; 4) increased insulin resistance; and 5) had potent antinatriuretic effects. Long-term safety and efficacy require further assessment.

Phase variation in meningococcal lipooligosaccharide biosynthesis genes

Neisseria meningitidis expresses a range of lipooligosaccharide (LOS) structures, comprising of at least 13 immunotypes (ITs). Meningococcal LOS is subject to phase variation of its terminal structures allowing switching between ITs, which is proposed to have functional significance in disease. The objectives of this study were to investigate the repertoire of structures that can be expressed in clinical isolates, and to examine the role of phase-variable expression of LOS genes during invasive disease. Southern blotting was used to detect the presence of LOS biosynthetic genes in two collections of meningococci, a global set of strains previously assigned to lineages of greater or lesser virulence, and a collection of local clinical isolates which included paired throat and blood isolates from individual patients. Where the phase-variable genes lgtA, lgtC or IgtG were identified, they were amplified by PCR and the homopolymeric tracts, responsible for their phase-variable expression, were sequenced. The results revealed great potential for variation between alternate LOS structures in the isolates studied, with most strains capable of expressing several alternative terminal structures. The structures predicted to be currently expressed by the genotype of the strains agreed well with conventional immunotyping. No correlation was observed between the structural repertoire and virulence of the isolate. Based on the potential for LOS phase variation in the clinical collection and observations with the paired patient isolates, our data suggest that phase variation of LOS structures is not required for translocation between distinct compartments in the host. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Microbiological Societies.

Expression analysis of delta-catenin and prostate-specific membrane antigen: Their potential as diagnostic markers for prostate cancer

The current approach to prostate cancer diagnosis has major limitations including the inability of prostate-specific antigen (PSA) assays to accurately differentiate between prostate cancer and benign prostate hyperplasia (BPH) and the imprecision of transrectal ultrasound (TRUS) biopsy sampling. We have employed cDNA microarray screening to compare gene expression patterns in BPH and tumour samples to identify expression markers that may be useful in discriminating between these conditions. Screening of 3 individual cDNA arrays identified 8 genes with expression 3-fold greater in 6 tumour tissues than in 1 nontumour sample and I BPH sample. Real-time PCR was used to confirm the overexpression of these 8 genes and 12 genes selected from the literature against a panel of 17 tumours and I 1 BPH samples. Two genes, delta-catenin (delta-catenin; CTNND2) and prostate-specific membrane antigen (PSMA; FOLH1), were significantly overexpressed in prostate cancer compared to BPH. Prostate epithelial cells stained positively for S-catenin and PSMA in our prostate cancer tissues, whereas the majority of our BPH tissues were negative for both markers. Thus we have identified delta-catenin (not previously associated with prostatic adenocarcinoma) and confirmed the potential of PSMA as potential candidates for the diagnosis and management of prostate cancer. (C) 2002 Wiley-Liss. Inc.