Identification of Predictable Biomarkers in Conjunction to Framingham Risk Score to Predict the Risk for Cardiovascular disease (CVD) in Non Cardiac Subjects

INTRODUCTION

Although the cardiovascular disease (CVD) burden is rising in different countries, the morbidity and mortality rate is not reduced to much extent because of lack of application of the biomarkers for diagnosing CVD. Hence, we aimed to establish the predictable biomarkers in conjunction to framingham risk score in order to predict the risk for CVD in non cardiac patients.

MATERIALS AND METHODS

Three hundred subjects were screened for the study who came for the master health checkup. Out of them 50 patients were excluded as they were under medication. 23 patients were excluded due to various systemic diseases like fever and infection etc. The remaining of 227 patients with age range of 30-80 y was randomly selected for investigation. These subjects were divided into four different groups: Group I - controls with age range: 30-60 y (n=50) these subjects were free from all the systemic ailments and risk factors. Study groups comprised of Group II - (n=44) with age range: 30-40 y, Group III - (n=50) with age range: 41-50 y and Group IV - (n=83) with age range: 51-80 y. Patients with different risk factors without medication participated as study groups. Routine biochemical parameters were analysed using fully automated analyser and atherosclerotic biomarkers was analysed using ELISA kit. In addition to this, framingham risk scores was calculated in all the groups, for 30 y risk prognosis for CVD.

RESULTS

The atherosclerotic biomarkers such as E-selectin, Leptin, osteoprotegerin (OPG) and Ox-LDL were elevated among the study groups as compared to control group. Pearson correlation showed a significant association between the individual risk score (30 y framingham risk for CVD) of individuals, and the above biomarkers. The Receiver operating curve (ROC) analysis also showed a greater area under curve with higher sensitivity and specificity.

CONCLUSION

We conclude the application E-Selectin, leptin, OPG and Ox-LDL as biomarkers along with the framingham risk scores in prediction risk for CVD in the individuals with subclinical atherosclerosis. It is more reliable and predictable as compared to the individual biomarkers alone.

Effect of curcumin against oxidation of biomolecules by hydroxyl radicals

BACKGROUND

Among various reactive oxygen species, hydroxyl radicals have the strongest chemical activity, which can damage a wide range of essential biomolecules such as lipids, proteins, and DNA.

OBJECTIVE

The objective of this study was to investigate the beneficial effects of curcumin on prevention of oxidative damage of biomolecules by hydroxyl radicals generated in in vitro by a Fenton like reaction.

MATERIALS AND METHODS

We have incubated the serum, plasma and whole blood with H2O2/Cu2+/ Ascorbic acid system for 4 hours at 37 0C and observed the oxidation of biomolecules like albumin, lipids, proteins and DNA.

RESULTS

Curcumin at the concentrations of 50,100 and 200 μmoles, prevented the formation of ischemia modified albumin, MDA, protein carbonyls, oxidized DNA and increased the total antioxidant levels and GSH significantly.

CONCLUSION

These observations suggest the hydroxyl radical scavenging potentials of curcumin and protective actions to prevent the oxidation of biomolecules by hydroxyl radicals.

Emergence of SFRP5 as a pleiotropic adipocytokine and its association with Wnt signaling pathways

The widespread perception of obesity as a non-communicable disease is slowly giving way to the view of a contagious, communicable and potentially fatal condition. The downstream comorbidities associated with it are endless. Hence, the slogan "Fat To Fit" is being promoted worldwide. The view of white adipose tissue as a fat storage organ is now shifting to an endocrine organ. The secreted hormones, called adipocytokines, act in an autocrine, paracrine, and endocrine fashion. Like other hormones, they can have a positive as well as a negative influence over the body. Secreted frizzled-related protein 5 (SFRP5) is a recently identified novel adipocytokine which falls under the category of those adipokines which have a positive influence on the system. Plasma SFRP5 levels are significantly lower in patients with obesity, insulin resistance and diabetes, a condition which contributes to the major components of the metabolic syndrome and to other disease conditions like atherosclerosis, autoimmune disorders, etc. This review article focuses on the effects of SFRP5 on the major systems of the body and on its association with the Wnt signaling pathways.

Estimation of serum neopterin in patients with acute coronary syndrome

BACKGROUND

The aim of our study was to determine neopterin levels in patients with acute coronary syndrome, in which the release of various cytokines activates the cellular immune system. There is an increase in the number and activity of T-cells in unstable atherosclerotic plaques, and of type 1 helper T-cells that produce interferon γ, which in turn produces neopterin, a byproduct of the guanosine triphosphate-biopterin pathway and a marker for activated macrophages.

METHODS

We studied 600 subjects consisting of healthy volunteers and patients with noncardiac chest pain, ST-segment elevation myocardial infarction, non-ST-segment elevation myocardial infarction, or unstable angina. Neopterin levels were determined by high-performance liquid chromatography.

RESULTS

Mean serum neopterin levels in ST-segment elevation myocardial infarction (11.5 ± 3.2 nmol·L(-1)), non-ST-segment elevation myocardial infarction (9.8 ± 2.9 nmol·L(-1)), and unstable angina patients (9.4 ± 2.3 nmol·L(-1)) were significantly higher than those in noncardiac chest pain patients (7.4 ± 1.9 nmol·L(-1)) and healthy volunteers (7.2 ± 0.6 nmol·L(-1); p < 0.001).

CONCLUSION

These findings suggest that serum neopterin levels may be a useful marker of systemic inflammation, and measurement of serum neopterin may be helpful in assessing the risk of developing coronary heart disease.

Estimation of Ischemia Modified Albumin (IMA) Levels in Patients with Acute Coronary Syndrome

Myocardial ischemia produces free radicals that catalyze a series of oxidative reactions that damage healthy tissues. The N-terminal sequence of albumin is one of the proteins modified by these highly reactive oxygen species and forms the ischemia modified albumin (IMA). This study involves investigations undertaken in different study groups to assess the levels of IMA. Mean serum IMA levels (U/mL) in patients with ST-segment elevated myocardial infarction (92.1 ± 10.6), non-ST-segment elevated myocardial infarction (87.3 ± 5.95) and unstable angina (UA) (88.9 ± 6.16) were significantly higher than non-cardiac chest pain (77.9 ± 6.69) and also healthy subjects (54.7 ± 17.2) (p < 0.001). IMA is a highly sensitive marker and has a high predictive value, which might prove the usefulness of this biomarker for early detection of myocardial ischemia. These data indicate a possible role of the IMA test in the early triage of patients with chest pain.

The clinical and biochemical parameters in relation to the serum neopterin levels in Indian children and adolescents

INTRODUCTION

An adverse pattern of blood lipids and cardiovascular abnormalities starts in obese children during childhood and neopterin serves as a marker for cardiovascular disease. Unfortunately, the data for children and adolescents, particularly, in the Indian population, are scarce. The present study aimed at evaluating the levels of serum neopterin in obese and overweight children and adolescents of the Indian population.

METHODS

The study groups included 296 school going children and adolescents. (96 obese and 97 overweight subjects were compared with 103 normal controls who were aged between 10-17 years). The anthropometric variables, the lipid profile, the fasting serum glucose which was analyzed by using an autoanalyzer and the serum neopterin levels were assayed by HPLC (Shimazdu) by using the method of Palfrey et al., 1993. The serum insulin levels were measured by using ELISA kits.

RESULTS

The serum neopterin levels (nmol/l) were elevated significantly in the obese (7.4±1.4) and overweight (6.4±0.8) (p<0.001) children and adolescents than in the controls (4.9±0.9). The serum neopterin levels showed a positive correlation with the BMI (r=0.79), WHR (r=0.5), systolic (r=0.44) and diastolic blood pressures (r= 0.25), insulin (r=0.57), HOMAIR (r=0.55), total cholesterol (r=0.35), triglycerides (r=0.20) and LDL-C (r=0.27) and they showed a negative correlation with HDL-C (r=-0.15) and fasting glucose (r= -0.3).

CONCLUSION

This study revealed a good relationship between serum neopterin and the anthropometric and biochemical parameters. We, therefore, aim to conduct regular camps at schools to counsel and advise the identified overweight and obese children to go for physical exercise and a balanced diet. The implementation of preventive measures from early childhood will have far reaching benefits, as even the prevalence of other obesity related disorders could decline.

Pregnancy associated plasma protein-A (PAPP-A) as an early marker for the diagnosis of acute coronary syndrome

AIMS AND OBJECTIVES

Pregnancy associated plasma protein-A (PAPP-A), a metalloproteinase plays a pivotal role in the pathogenesis of atherosclerosis. Recent studies have reported that elevated levels of PAPP-A, signal the onset of acute coronary syndrome (ACS). We, therefore, proposed to study the analytical competence of PAPP-A in patients admitted to the emergency department with chest pain and finally diagnosed as ACS.

METHODS AND RESULTS

Pregnancy associated plasma protein-A was measured using enzyme-linked immunosorbent assay (ELISA) in 485 patients admitted to emergency care unit, of which 89 patients were diagnosed as Non-cardiac chest pain (NCCP). Elevated levels of PAPP-A were observed in patients diagnosed as ACS on comparison with the controls. Receiver operator characteristic (ROC) curve analysis showed PAPP-A to be a good discriminator between ischaemic and non-ischaemic patients. The area under the curve was found to be 0.904, 95% CI (0.874-0.929) with 90% sensitivity and 85% specificity (P< 0.0001). The cut-off value from the ROC curve was 0.55 μg/mL above which PAPP-A was considered to be positive.

CONCLUSION

Pregnancy associated plasma protein-A seems to be a promising biomarker for identification and risk stratification for patients with ACS.

Serum E-selectin levels in Indian children and adolescents: relation to clinical and biochemical parameters

BACKGROUND

An adverse pattern of blood lipids and atherosclerosis begin in childhood. Unfortunately, data for children and adolescents, particularly those in the Indian population, are scarce. The present study aims to evaluate the levels of serum E-selectin in Indian children and adolescents and its correlation with anthropometric and biochemical parameters.

METHODS

The study groups included 338 school children and adolescents. There were 96 obese children, 97 overweight children and 42 children with congenital heart disease who were compared with 103 normal controls, aged 10-17 years. Serum E-selectin and serum leptin were analyzed with enzyme-linked immunosorbent assay kits. Lipid profile and fasting glucose were analyzed using an autoanalyzer.

RESULTS

Serum E-selectin levels were significantly increased in obese (65.3 ± 8.39 ng/mL) and overweight (56.01 ± 6.96 ng/mL) subjects (P < 0.001). However, these levels were lower in children with congenital heart disease (40.99 ± 6.54 ng/mL) than in controls (43.79 ± 6.71 ng/mL).

CONCLUSION

Serum E-selectin levels showed good positive association with body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, leptin, total cholesterol, triglycerides and low-density lipoprotein cholesterol and showed negative correlation with fasting glucose and no significant association with high-density lipoprotein cholesterol. These findings indicate that higher E-selectin levels can induce endothelial activation and play an essential role in the earliest stage of the atherosclerotic process in obese and overweight children. Regular camps at schools to counsel the identified overweight and obese children and to encourage physical exercise would help to reduce the risk of these children being prone to major cardiovascular anomalies in adulthood.

Plasma total nitric oxide and endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphism: a study in a South Indian population

In an analysis of the possible association of endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphism and plasma nitric oxide levels in patients with acute coronary syndrome, we investigated 106 patients with the syndrome and 100 healthy controls. Genotype was determined using the polymerase chain reaction; plasma nitric oxide levels were found using ELISA. The genotype frequencies for the a/b polymorphism in the control group were 77% for bb, 19% for ab, and 4% for aa. In the patients, genotype frequencies were 55% bb, 34% ab, and 11% aa. The allele frequencies were 28% a and 72% b among the patients and 13% a and 87% b among control subjects. Our findings showed a significant association of the ecNOS gene polymorphism with acute coronary syndrome in the South Indian population.

Heart fatty acid binding protein (H-FABP) as a diagnostic biomarker in patients with acute coronary syndrome

AIMS AND OBJECTIVES

Diagnosis of myocardial ischaemia at an early stage in the emergency department is often difficult. A recently proposed biomarker, heart fatty acid binding protein (H-FABP) has been found to appear in the circulation superior to that of cardiac troponins in the early hours of acute coronary syndrome. We proposed to evaluate the levels of H-FABP and ascertain its utility as an early biomarker for acute coronary syndrome (ACS).

METHODS AND RESULTS

The present study was carried out in 485 subjects, of whom 297 were diagnosed as patients with ACS, 89 were diagnosed as non-cardiac chest pain (NCCP) and 99 people served as healthy controls. H-FABP levels were measured in comparison with standard markers such as troponin I and CK-MB in all subjects enrolled in the study. The levels of H-FABP were significantly raised in patients when compared to controls and NCCP (P<0.001). Receiver Operator Characteristic Curve (ROC) analysis showed H-FABP to be a good discriminator between patients with ischaemic heart disease and patients without ischaemic heart disease. The area under the curve was found to be 0.965 with 95% CI (0.945-0.979). The cut-off value above which H-FABP can be considered positive was found to be 17.7ng/ml.

CONCLUSION

H-FABP is a promising biomarker for the early detection of patients with acute coronary syndrome.

Urinary 8-OHdG: A marker of oxidative stress to DNA and total antioxidant status in essential hypertension with South Indian population

Establishment of non-invasive urinary biomarker for the early prediction of essential hypertension (EH) is important. We evaluated whether estimation of urinary DNA, serves as a marker to predict the extent of cellular oxidative stress in essential hypertension. A total of 180 South Indian subjects aged 30-65 were recruited for the study. Of these hypertensive subjects investigated, 30 were newly diagnosed and were not on any antihypertensive drugs, but had systolic blood pressure 140-160 mmHg and diastolic blood pressure 95-100 mmHg and 75 hypertensive patients who already on drug therapy for one year and 75 were South Indian normotensive healthy controls with blood pressure ≤ 120/80 mmHg. The 8-OHdG level in urine was significantly increased in hypertensive patients (both newly diagnosed and who already on drug therapy) compared with control group. The significant increase in 8-OHdG was observed in newly diagnosed hypertensive patients compared with hypertensive patients who already on drug therapy. There was a significant decrease in serum TAS value in essential hypertensive group when compared to control group. The urinary 8-OHdG was independently correlated with serum TAS. Decreased TAS levels, which reflect to increased oxidative stress, may be the reason of increased urinary 8-OHdG in South Indian hypertensive patients. Our preliminary data suggest that the competitive ELISA for 8-OHdG appears to be a simple method for quantifying the extent of oxidative stress.

Increased serum concentrations of Soluble CD40 Ligand as a prognostic marker in patients with Acute Coronary Syndrome

CD40-CD40L interaction plays a significant role in the pathogenesis of atherosclerosis and coronary artery disease. The clinical predictive value of Soluble CD40 Ligand (sCD40L) was evaluated in patients with Acute Coronary Syndrome (ACS) and Non-Cardiac Chest Pain (NCCP). The levels of serum soluble CD 40 ligand were measured by ELISA in 485 patients admitted to emergency care unit, of which 89 patients were diagnosed as NCCP. The levels of sCD40L were significantly increased in patients with ACS when compared to controls and NCCP. Receiver Operator Characteristic (ROC) Curve analysis showed sCD40L to be a good discriminator between patients with ischemic heart disease and patients without ischemic heart disease. The area under the curve was found to be 0.940 with 95% CI (0.915 to 0.960) (P<0.0001). The cut off value from the ROC curve was 2.99 ng/ml, above which sCD40L was considered to be positive. Combined assessment of sCD40L, Troponin I and CK-MB enhanced the risk prediction and early classification of patients. sCD40L seems to be a promising biomarker for identification and risk stratification for patients with acute coronary syndrome.

Serum myeloperoxidase: a novel biomarker for evaluation of patients with acute coronary syndrome

OBJECTIVES

Myeloperoxidase, an abundant leucocyte enzyme, is elevated in culprit lesions that have ruptured in patients with sudden cardiac injury. Multiple lines of evidence suggest an association between myeloperoxidase and inflammation and acute coronary syndrome. Myeloperoxidase has been proposed as a potent risk marker and diagnostic tool in acute coronary syndrome (ACS). Recent studies have reported the potential use of myeloperoxidase in acute coronary syndrome, but limited reports are available on its utility in different groups of ACS in the emergency department. Therefore the circulating levels of serum myeloperoxidase in patients with acute coronary syndrome and control subjects were studied.

DESIGN AND SETTING

The levels of serum myeloperoxidase were measured by ELISA in 485 patients admitted to emergency care unit, of which 89 patients were diagnosed as non-cardiac chest pain (NCCP). The levels of myeloperoxidase were significantly increased in patients with ACS when compared with controls and NCCP. From the receiver operator characteristic (ROC) curve analysis, the optimum value above which myeloperoxidase can be considered positive was found to be 48.02 U/ml. The area under the curve was found to be 0.956 with 95% CI (0.934 to 0.973) (p<0.0001). A combination analysis of ROC curves of troponin, creatine kinase MB (CK-MB) and myeloperoxidase showed myeloperoxidase to be highly significant. Multivariate analysis revealed myeloperoxidase to be an independent diagnostic marker for early diagnosis of ACS.

CONCLUSION

Myeloperoxidase, in contrast to troponin and CK-MB, identified patients at risk of ischaemic events, even in the absence of myocardial necrosis, thus highlighting its potent usefulness for risk stratification among patients presenting with chest pain.

Decreased bioavailability of rifampin and other antituberculosis drugs in patients with advanced human immunodeficiency virus disease

We evaluated the effects of human immunodeficiency virus (HIV) disease on pharmacokinetics of antituberculosis medications by measuring concentrations of isoniazid and rifampin in blood and of pyrazinamide and ethambutol in urine. Peak concentration and exposure were reduced for rifampin, and rapid acetylators of isoniazid had lower drug levels. HIV and HIV-tuberculosis patients who have diarrhea and cryptosporidial infection exhibit decreased bioavailability of antituberculosis drugs.

Disposition of uric acid upon administration of ofloxacin alone and in combination with other anti-tuberculosis drugs

Disposition of uric acid upon administration of ofloxacin (O) alone and in combination with other anti-tuberculosis drugs, rifampicin (R), isoniazid (H) and pyrazinamide (Z) was studied. Twelve male healthy volunteers were investigated on four different occasions with the four drugs alone or in combinations. A partially balanced incomplete block design was adopted and the subjects were randomly allocated to each group. Uric acid concentration in urine samples excreted over 0-8 hr, were determined after coding the samples. There was significant decrease in the group receiving Z when compared to other groups. Though there was a decrease in uric acid excretion in the group receiving O, it was not statistically significant. Rifampicin and H seem to increase the uric acid excretion. The incidence of arthralgia was mainly due to Z and not due to either O or other drugs in the treatment of pulmonary tuberculosis.

Standardization of the method for estimation of ethambutol in pharmaceutical preparations and biological fluid

A simple column chromatographic method for determination of ethambutol (EMB) in pharmaceutical preparations containing EMB in combination with other anti-TB drugs is presented. The method involved extraction of EMB into an organic solvent, followed by basification and column chromatographic separation on Amberlite CG 50 (100-200 mesh) and elution with suitable eluants and estimation at a wavelength of 270 nm. The assay was linear from 25 to 400 microg/ml. The relative standard deviations of intra and inter day assays were lower than 5%. Ethambutol was recovered from human urine quantitatively and stable for a period of at least one week in urine stored at -20 degrees C.

Malabsorption of rifampin and isoniazid in HIV-infected patients with and without tuberculosis

The absorption of rifampin, isoniazid, and D-xylose in patients with human immunodeficiency virus (HIV) infection and diarrhea, in patients with HIV infection and tuberculosis (TB), in patients with pulmonary TB alone, and in healthy subjects was studied. Percentage of dose of the drugs, their metabolites, and D-xylose excreted in urine were calculated. A significant reduction in the absorption of drugs and D-xylose in both the HIV infection/diarrhea and HIV infection/TB groups was observed (P<.05), and the correlation between them was significant. Our results indicate that patients with HIV infection and diarrhea and those with HIV infection and TB have malabsorption of rifampin and isoniazid.

Process development for the synthesis of 5'-O-(4,4'-dimethoxytrityl)-N2-isobutyryl-2'-O-(2-methoxyethyl)-guanosine--a potential precursor for the second generation antisense oligonucleotides: an improved process for the preparation of 2'-O-alkyl-2,6-diaminopurine riboside

An efficient four step process for the preparation of 5'-O-(4,4'-dimethoxytrityl)-N2-isobutyryl-2'-O-(2-methoxyethyl)-guanosine 1 was developed. Direct 2'-O-alkylation of 2,6-diaminopurine riboside 2 was accomplished via inexpensive and commercially available reagents such as KOH, DMSO and alkyl halides at room temperature in 4-6 hrs. Pure 2'-O-(2-methoxyethyl)-DAPR 3 was isolated by crystallization from methanol. Enzymatic deamination of 3 followed by selective N2-isobutyrylation and 5'-O-dimethoxytritylation furnished desired 1 in high yield and purity. Fully optimized four step synthetic process has been scaled up to the pilot plant level.

Bioavailability of rifampicin following concomitant administration of ethambutol or isoniazid or pyrazinamide or a combination of the three drugs

BACKGROUND & OBJECTIVES

Poor bioavailability of rifampicin (R) in combination with other anti-tuberculosis drugs such as isoniazid (H), pyrazinamide (Z), and ethambutol (E) is a subject of much concern for the last few decades. This could be due to an interaction between R and other drugs. An investigation was therefore undertaken to examine the bioavailability of R in the presence of H, Z and E or a combination of the three drugs.

METHODS

The study included eight healthy volunteers, each being investigated on four occasions at weekly intervals once with R alone and with three of the four combinations on the three remaining occasions. A partially balanced incomplete block design was employed and the allocation of R or the drug combinations was random. Plasma concentrations of R at intervals up to 12 h were determined by microbiological assay using Staphylococcus aureus as the test organism. The proportion (%) dose of R as R plus desacetyl R (DR) in urine excreted over the periods 0-8 and 8-12 h was also determined. Bioavailability was expressed as an index (BI) of area under time concentration curve (AUC) calculated from the plasma concentrations or proportion of dose of R excreted as R plus DR in urine with the combinations to that with R alone.

RESULTS

The bioavailability indices based on AUC were 0.96 with RE, 0.76 with RH, 1.08 with RZ and 0.65 with REHZ. The indices based on urine estimations (0-8 h) were similar, the values being 0.94, 0.84, 0.94 and 0.75, respectively. A second investigation revealed that the decrease of bioavailability of R with H was not due to the excipients present in H tablets.

INTERPRETATION & CONCLUSION

Isoniazid alone or in combination with E and Z reduces the bioavailability of R. Urinary excretion data offer a simple and non invasive method for the assessment of bioavailability of R.

Dose related pharmacokinetics of ofloxacin in healthy volunteers

OBJECTIVE

To evaluate the pharmacokinetic profile of ofloxacin in healthy volunteers after single oral doses of 600 and 800 mg.

DESIGN

Seven healthy volunteers were administered 600 and 800 mg of ofloxacin on two occasions with an interval of one week. Paired samples of blood and saliva were collected after 1, 2, 3, 6, 9, 12, 24, 32 and 48 hours post-dose. Urine samples were collected over a period of 0-6, 6-12 and 12-24 hours. Concentrations of ofloxacin in plasma, saliva and urine were assayed by high performance liquid chromatography.

RESULTS

Increases of 22% in peak plasma concentration (Cmax) and 40% in area under the concentration-time curve (AUC0-24) were observed with the 800 mg dose. The other parameters, namely time to attain Cmax, half-life, the apparent volume of distribution, plasma and renal clearance and percentage of dose excreted in urine over 24 hours were independent of doses. The mean ratios of the concentration in saliva to the concentration in plasma ranged from 0.4-0.6, and the correlation coefficient was 0.94.

CONCLUSIONS

Dose proportionality was observed in Cmax and AUC0-24 when 600 and 800 mg doses of ofloxacin were given. Ofloxacin determined in saliva seems to be suitable for therapeutic drug monitoring.

Effect of rifampicin & isoniazid on cytochrome P-450 in mycobacteria

BACKGROUND & OBJECTIVES

Rifampicin and isoniazid are the most important first line drugs used in the treatment of tuberculosis. These drugs are also used in combination with other medications to treat co-infections. It, therefore, becomes important to study the effect of these drugs on the drug metabolizing system, namely, cytochrome P-450, not only in the host but also in the bacteria. We report the effect of rifampicin and isoniazid on the cytochrome P-450 activity in Mycobacterium smegmatis and M. tuberculosis H37Rv.

METHODS

Subinhibitory concentrations of rifampicin and isoniazid were added to the organisms after they had attained the growth phase and cytochrome P-450 activity was estimated in the membranous fractions of the bacteria at different time points.

RESULTS

Rifampicin was able to significantly enhance cytochrome P-450 in both M. smegmatis and M. tuberculosis H37Rv. Isoniazid was found to inhibit cytochrome P-450 in M. tuberculosis H37Rv, while there seemed to be no effect in M. smegmatis.

INTERPRETATION & CONCLUSION

We report here the effect of rifampicin and isoniazid on mycobacterial cytochrome P-450. These findings are similar to those found in eukaryotic organisms. The role of mycobacterial cytochrome P-450 in the metabolism of drugs within the bacteria needs to be elucidated.

Bioavailability of rifampicin, isoniazid and pyrazinamide in a triple drug formulation: comparison of plasma and urine kinetics

SETTING

The present study assesses bioavailability indices for rifampicin, isoniazid and pyrazinamide when administered to healthy volunteers separately or in a fixed triple-drug formulation, Rifater 125 SCT.

OBJECTIVE

To compare the pharmacokinetics of rifampicin, isoniazid and pyrazinamide based on their blood concentrations up to 12 hours with the proportions of the doses of the drugs and their metabolites excreted in urine up to 12 hours, and to assess the bioavailability indices for the free and fixed triple drug formulations.

DESIGN

An open cross-over study was conducted in 18 healthy volunteers with normal hepatic and renal functions to whom the drug combinations were administered in free and fixed dose formulations a week apart, to the same subject.

RESULTS

Concentrations of the three drugs/metabolites were assessed in blood and urine. The results indicated the absence of negative pharmacokinetic interactions between the drugs when administered in both the free and the new fixed triple drug formulation.

CONCLUSION

Human bioavailability studies provide direct straightforward information, particularly when studying compounds such as rifampicin and other major anti-tuberculosis drugs. The results of the present study indicate that the pharmacokinetic properties of rifampicin, isoniazid and pyrazinamide as assessed after individual and combined administration do not change when combined in a single pharmaceutical preparation. The bioavailability indices calculated based on plasma concentrations and urinary levels for all three drugs compared well.

Salivary levels of isoniazid and rifampicin in tuberculous patients

Concentrations of isoniazid and rifampicin were determined in time-matched samples of saliva and serum from 30 tuberculous patients (18 with pulmonary tuberculosis and 12 with intestinal tuberculosis), comprising 18 slow and 12 rapid acetylators of isoniazid, following administration of isoniazid 300 mg and rifampicin 12 mg/kg. The diffusion of isoniazid into saliva was quite rapid and the salivary concentrations were similar to those in serum, suggesting that saliva could be used in place of serum for all pharmacokinetic studies with isoniazid. The salivary concentrations of rifampicin were much lower than those in serum, the mean peak concentrations being 0.9 and 8.5 microgram/ml, respectively. Further, there was evidence of a significant delay in the diffusion of rifampicin from serum to saliva.

Membrane bound cytochrome P-450 determines the optimal temperatures of NADPH-cytochrome P-450 reductase and cytochrome P-450-linked monooxygenase reactions in rat and trout hepatic microsomes

The hepatic monooxygenase systems largely responsible for the biotransformation of drugs and other xenobiotics are comprised of NADPH-cytochrome P-450 reductase and multiple forms of cytochrome P-450. Optimal temperatures for these systems in the trout and rat are 26 degrees and 37 degrees, respectively. Purified trout and rat reductases are optimally functional at 26 degrees and 37 degrees, respectively, when added to trout and rat microsomes. However, rat reductase was shown to function optimally at 26 degrees when added to trout microsomes and trout reductase functioned optimally at 37 degrees when added to rat microsomes. Corresponding shifts in optimal temperatures of cytochrome P-450-linked 0-deethylation of 7-ethoxycoumarin occurred when these reductases were added to rat or trout microsomes. It is proposed that the phospholipid annulus surrounding the active site of membrane-bound cytochrome P-450 determines the optimal temperature of cytochrome P-450 systems.

Lack of relationship between hepatic toxicity and acetylator phenotype in three thousand South Indian patients during treatment with isoniazid for tuberculosis

The results are presented of a retrospective analysis of the incidence of jaundice among 3,000 patients with pulmonary tuberculosis and of the activities of serum aspartate aminotransferase among 850 according to their isoniazid acetylator phenotype. The patients had been treated with a variety of isoniazid-containing regimens in a series of controlled clinical trials in South India. The results show that rapid acetylators are no more prone to develop isoniazid-induced hepatic toxicity than are slow acetylators.

Pyrazinamide deamidase activity in tuberculous disease

To investigate whether pyrazinamide deamidase activity is suppressed in tuberculosis, serial serum concentrations of pyrazinamide, following 40 mg of pyrazinamide per kg, were determined in 10 patients with sputum positive pulmonary tuberculosis and in 10 control subjects without disease. The concentrations and the half-lives of pyrazinamide were similar in the 2 groups, suggesting no suppression of the deamidase activity in tuberculous patients.