Screening for microalbuminuria by use of microproteinuria

We aimed to develop a reliable, low cost method to assess the early stages of renal impairment in diabetes, for use in high-risk populations in countries with limited resources. We evaluated a trichloroacetic acid (TCA) turbidimetric method for microproteinuria screening in patients with diabetes. The method was compared with an immunoturbidimetric procedure for the detection of microalbumuniuria. Both methods performed within limits of allowable uncertainty based on inter- and intra-individual variation. A urinary albumin/creatinine ratio of 3.0 g/mol, assumed as diagnostic of microalbuminuria, was found to correlate with a cut-off value of 24 mg/L for microproteinuria. The clinical sensitivity and specificity of the TCA method determined against this ratio were 86% and 90% respectively. The reliability and practicability of the TCA method renders it suitable for the detection of early stage renal damage, with emphasis on screening high-risk populations in countries with limited resources.

The Diabetes and Pre-eclampsia Intervention Trial

OBJECTIVE

Rates of pre-eclampsia in women with type 1 diabetes are two to four times higher than in normal pregnancies. Diabetes is associated with antioxidant depletion and increased free radical production, and an increasing body of evidence suggests that oxidative stress and endothelial cell activation may be relevant to disease pathogenesis in pre-eclampsia. The Diabetes and Pre-eclampsia Intervention Trial (DAPIT) aims to establish if pregnant women with type 1 diabetes supplemented with vitamins C and E have lower rates of pre-eclampsia and endothelial activation compared with placebo treatment.

METHODS

DAPIT is a randomised multicentre double-blind placebo-controlled trial that will recruit 756 pregnant women with type 1 diabetes from 20 metabolic-antenatal clinics in the UK over 4 years. Women are randomised to daily vitamin C (1000 mg) and vitamin E (400 IU) or placebo at 8-22 weeks of gestation until delivery. Maternal venous blood is obtained at randomisation, 26 and 34 weeks, for markers of endothelial activation and oxidative stress and to assess glycaemic control. The primary outcome of DAPIT is pre-eclampsia. Secondary outcomes include endothelial activation (PAI-1/PAI-2) and birthweight centile.

Total homocysteine is not a determinant of arterial pulse wave velocity in young healthy adults

AIMS

Hyperhomocysteinaemia has been associated with reduced pulse wave velocity (PWV) in patients with end-stage renal disease and in those with hypertension. The aim of this study was to examine the association between total homocysteine (tHcy) concentrations, the biochemical and genetic determinants of tHcy and PWV in healthy young adults.

METHODS AND RESULTS

A total of 489 subjects aged 20-25 years participated. A fasting blood sample was taken and PWV measured using a non-invasive optical method. tHcy did not correlate with PWV, whether assessed at the aorto-iliac segment (P = 0.18), the aorto-radial segment (P = 0.39) or the aorto-dorsalis-pedis segment (P = 0.22). When tHcy was classified into normal (<15) and high (> or =15micromol/l), PWV did not differ between the two groups at any segment. PWV did not differ by MTHFR C677T or NOS3 G894T genotype, even when smoking and folate sub-groups were considered. Considering aortic PWV as a dependent variable, stepwise regression analysis showed that the only parameter entering the model for all segments was systolic blood pressure (aorto-iliac, P < 0.001; aorto-radial, P = 0.01; aorto-dorsalis-pedis, P = 0.001). Age, sex, COL1A1 genotype and triglycerides entered the model significantly for two of three segments.

CONCLUSION

This study shows that arterial PWV is not associated with tHcy in a healthy young population.

Oxygen consumption is increased relative to work rate in patients with McArdle's disease

BACKGROUND

Patients with McArdle's disease suffer exercise incapacity as a result of myophosphorylase deficiency, and for a given work rate have excessive circulatory and ventilatory responses. We hypothesized that the rate of increase of oxygen consumption with work rate (DeltaVO2-DeltaWR slope) would also be elevated in such patients as a result of these excessive responses.

PATIENTS AND METHODS

Five patients with McArdle's disease and five matched controls carried out a maximal incremental cardiopulmonary exercise test. Controls then carried out a second test matched to the maximal test of a paired patient. Venous blood was sampled at rest, peak exercise and recovery.

RESULTS

During the matched test, the DeltaVO2-DeltaWR slope was higher in the patients than in the controls [19.9 (15.0-24.6) vs. 11.7 (9.2-13.5) mL min(-1) W(-1); mean (range); P = 0.022], and the peak-achieved VO2 was also greater in the patient group [1201 (890-1575) vs. 918 (599-1248) mL min(-1); P = 0.003]. A similar pattern was observed for heart rate [173 (165-182) vs. 108 (105-134) b.p.m.; P = 0.001] and plasma norepinephrine levels [12.6 (9.2-19.9) vs. 2.9 (2.2-4.9) nmol l(-1); P = 0.003].

CONCLUSION

There is an increased rate of rise in VO2 relative to work rate during exercise in patients with McArdle's disease. There is also a greater rise in catecholamines, which may be the result of a physiological response to substrate starvation, and is likely to contribute to the increase in VO2.

Malondialdehyde and Measures of Antioxidant Activity in Subjects from the Belfast Elderly Longitudinal Free-Living Aging Study

Glutathione and glutathione peroxidase activity are important components in the complex body defense against oxidative damage. In this study, we have measured malondialdehyde (MDA) as a marker of oxidative stress, the antioxidant glutathione (GSH), and activity of the antioxidant enzyme (GSHPx), in a cohort of free-living elderly subjects from the Belfast Elderly Longitudinal Free-living Aging STudy (BELFAST), hypothesizing that free-living Senieur-approximated nonagenarians might demonstrate enhanced antioxidant defense mechanisms. The main finding in the BELFAST octo/nonagenarians was that plasma antioxidant glutathione increased in nonagenarian compared with septo/octogenarian subjects (P =.015), whereas conversely antioxidant glutathione peroxidase activity fell in the nonagenarian group (P <.0001). In the same subject group, malondialdehyde, a measure of lipid peroxidation, showed no change across the age groups (P =.73). These results might overall represent a situation in which elderly survivors in the BELFAST study have evolved a sort of free radical/antioxidant equilibrium as a mechanism of successful aging.

The photochemistry of indenyl alcohols and esters: Substituent effects on the competition between ion- and radical-derived products

The photochemistry of the indenyl acetates 1 and pivalates 2, substituted with X = H, 5-CH3O, and 6-CH3O, have been examined in both methanol and cyclohexane. The precursor alcohols 3 were also found to be photoreactive. Although only radical-derived products were obtained in cyclohexane, both ion- and radical-derived products were formed in methanol. The absence of significant fluorescence emission from any of the substrates 1, 2, and 3 indicates that the excited singlet states are highly reactive. A mechanism is proposed for the ion-derived products that proceeds through direct heterolytic cleavage to give an indenyl cation – carboxylate anion pair. The indenyl cations generated are anti-aromatic in the ground state and their efficient generation by this photochemical solvolysis is in sharp contrast to the very low reactivity of related ground-state substrates. For the pivalate esters 2, an excited-state migratory decarboxylation is proposed for the formation of tert-butyl derived products.Key words: ester photochemistry, indenyl cations, indenyl radicals.

Oxidative modification of triacylglycerol-rich lipoproteins

Lipoprotein oxidation is thought to play a pivotal role in the evolution of atherosclerosis. Low-density lipoprotein (LDL) is the main source of oxidized lipid in the arterial wall. Oxidation of LDL alters its properties in a number of ways, making it more atherogenic, but oxidation of other lipoprotein classes may also be important. Common mechanisms are likely to contribute to the oxidation of all lipoprotein classes, with enzyme-mediated oxidation likely to be most important. Antioxidant content, fatty acid composition, particle size and the presence of seeding hydroperoxides also influence oxidative reactions. Larger triglyceride-rich lipoproteins are less likely to enter the arterial wall than LDL, but when oxidized will deliver a greater oxidant load to the arterial wall.

Vitamin C improves endothelial function in healthy estrogen-deficient postmenopausal women

OBJECTIVE

Estrogen deficiency is associated with increased cardiovascular risk and endothelial dysfunction. Improvements in endothelial function with antioxidants, including vitamin C, have been reported. We aimed to determine the acute effect of vitamin C on endothelial function in healthy women with established menopause.

SUBJECTS

Subjects (aged 47-59 years) were at least 1 year postmenopause. Ten (serum estradiol < 50 pmol/l) were not receiving hormone replacement therapy, while eight hysterectomized subjects received subcutaneous estradiol.

DESIGN

Forearm blood flow (FBF; strain-gauge plethysmography) responses to intrabrachial artery infusions of incremental doses of acetylcholine (endothelium-dependent vasodilation) and sodium nitroprusside (endothelium-independent vasodilation) were determined at baseline, and following 1.5 g vitamin C given intravenously.

RESULTS

At baseline, estrogen-treated subjects had a lower index of insulin resistance (homeostasis model assessment, HOMA) and lower fibrinogen than those of estrogen deficient subjects. There was a trend towards higher baseline FBF and larger baseline FBF response to acetylcholine in estrogen-treated subjects. FBF responses to acetylcholine were significantly enhanced after vitamin C in estrogen-deficient subjects (area under the dose-response curve (AUC): estrogen-deficient 9.9 +/- 2.6 vs. 15.1 +/- 3.2 (mean +/- SEM), p = 0.02; estrogen-treated 17.0 +/- 2.9 vs. 21.0 +/- 3.2, p = 0.07). Resting FBF and response to sodium nitroprusside were unchanged in either group by vitamin C. Plasminogen activator inhibitor-1 levels fell after vitamin C in the estrogen-deficient group (17.0 +/- 1.6 vs. 14.7 +/- 0.9 IU/ml, p = 0.03).

CONCLUSIONS

These results indicate that endothelial function may be improved acutely by antioxidant treatment in postmenopausal women with established estrogen deficiency.

Genetics of the lipoprotein lipase gene and hypertriglyceridaemia

The aim of this study is to assess whether genetic variation at the lipoprotein lipase (LPL) gene is related to fasting triglyceride levels or to the presence of vascular disease. Hypertriglyceridaemic patients are genotyped for the N291S, G188E, and P207L variants and the HindIII and PvuII restriction fragment length polymorphisms of the LPL gene. Sequence analysis is carried out on exons 1-9 of the LPL gene for patients with severe hypertriglyceridaemia, to search for new gene variants. No differences were found between the patient and control group for the N291S, G188E and P207L variants. The HindIII and PvuII allelic frequencies were found to be similar for patients and controls; however, the frequency of the PvuII P2 allele was higher in patients with vascular disease (allele frequency: 0.56) than patients with no vascular disease (allele frequency, 0.42) (P=0.03). Sequence analysis revealed no exon sequence variants in the LPL gene but two intron sequence variants were found in intron 5 in two patients.

The effect of lower limb ischaemia-reperfusion on intestinal permeability and the systemic inflammatory response

OBJECTIVES

a relationship has been demonstrated between increased intestinal permeability, endotoxaemia and the development of the systemic inflammatory response syndrome (SIRS) after aortic surgery. The aim of this study was to evaluate whether isolated lower limb ischaemia-reperfusion (I/R) injury affects intestinal mucosal barrier function and cytokine release.

PATIENTS AND METHODS

four groups of patients were investigated, group I, patients with critical limb ischaemia (CLI) undergoing infra-inguinal bypass surgery (n=18); group II, patients with intermittent claudication (IC) undergoing infra-inguinal bypass surgery (n=14); group III, patients with CLI unsuitable for arterial reconstruction, undergoing major amputation (n=12); and group IV, patients undergoing carotid endarterectomy for symptomatic carotid stenosis (n=13). Intestinal permeability, endotoxaemia and urinary soluble tumour necrosis factor receptors were assessed (p55TNF-R).

RESULTS

an increase in intestinal permeability was observed on the 3rd postoperative day only in CLI group. This was found to correlate with arterial clamp time. Patients who had a femoro-distal bypass had significantly higher intestinal permeability compared to those who had femoro-popliteal bypass. Endotoxaemia was not detected in any of the groups. Postoperative urinary p55TNF-R concentrations were significantly higher in CLI group compared to the other groups. These did not correlate with the increased intestinal permeability.

CONCLUSIONS

our results support the hypothesis that revascularisation of critically ischaemia limbs leads to intestinal mucosal barrier dysfunction and cytokine release. They also suggest that the magnitude of the inflammatory response following I/R injury is related to the degree of initial ischaemia.

Autoantibodies to malondialdehyde-modified low-density lipoprotein in patients with angiographically confirmed coronary artery disease

Oxidised low-density lipoprotein (LDL) has physicochemical properties that are pivotal in atherosclerotic plaque formation. As a consequence, antioxidant regimens may prove an important therapy in the prevention and treatment of cardiovascular disease. Since oxidised LDL is immunogenic, the aims of our study were to measure serum IgG titres to malondialdehyde-modified LDL (MDA-LDL) in patients with coronary artery disease (CAD) and control subjects and assess their potential as a clinical marker for coronary atherosclerosis and, consequently, antioxidant intervention. Serum IgG titres to MDA-LDL were measured in patients with angiographically confirmed CAD (n = 40) and aged-matched controls (n = 40) by enzyme-linked immunosorbant assay (ELISA). Titres were calculated and expressed as both the difference and the ratio of blanked absorbance units (AU) for IgG binding to MDA-LDL and native LDL. For the control population, median IgG titres were 0.26 AU (interquartile range (IQR) 0.20-0.46 AU) and 5.34 (IQR 3.40-8.58), respectively, while the patient population had median IgG titres of 0.30 AU (IQR 0.20-0.47 AU) and 5.08 (IQR 3.30-9.66), respectively. Both sets of calculated titre values were not significantly different between the two groups (P = 0.60 and 0.82, respectively). In conclusion, this study could not establish any significant association between circulating autoantibody titres to MDA-LDL and coronary atherosclerosis. Therefore, the diagnostic value of autoantibodies to oxidised LDL remains unclear.

A longitudinal study through adolescence to adulthood: the Young Hearts Project, Northern Ireland

The Young Hearts (YH) Project is an ongoing study of biological and behavioural risk factors for cardiovascular disease in a representative sample of young people from Northern Ireland, a region of high coronary mortality. This article describes the cross-sectional clinical, dietary and lifestyle data obtained from individuals (aged 20-25 y) who participated in phase 3 of the project (YH3). A total of 489 individuals (251 males, 238 females) participated in YH3 (48.2% response rate). Some 31.1% of participants at YH3 were overweight (BMI >25 kg/m(2)) with 4.4% of males and 8.0% of females were obese (BMI >30 kg/m(2)). More females than males had a very poor fitness (55.0 vs 22.1%, chi-squared 51.70, d.f. 1, P<0.001) and did not participate in any sporting or exercise activity (38.4 vs 24.9%, chi-squared 10.26, d.f. 1, P=0.001). Over 20% of participants had a raised total serum cholesterol (>5.2 mmol/l). More females had a raised serum LDL-cholesterol (>3.0 mmol/l) than males (44.6 vs 34.6%, chi-squared 4.39, d.f. 1, P<0.05). Over 46% of participants reported energy intakes from fat above recommended levels, and 68.5% of participants had saturated fat intakes above those recommended (Dietary reference values for food energy and nutrients for the United Kingdom. HMSO: London, 1991). Just over half of the study population reported alcohol intakes in excess of recommended sensible limits set by the Royal College of Physicians (A great and growing evil: the medical consequences of alcohol abuse. Tavistock: London, 1987), with 36.7% of males and 13.4% of females reporting intakes over twice these recommended limits. A total of 37% of the study population smoked. During young adulthood, individuals may be less amenable to attend a health-related study and recruitment of participants to the current phase of the study proved a major problem. However, these data constitute a unique developmental record from adolescence to young adulthood in a cohort from Northern Ireland and provide additional information on the impact of early life, childhood and young adulthood on the development of risk for chronic disease.

Accentuated oxidative stress following reperfusion injury in diabetic rats

BACKGROUND

This study investigates whether diabetes mellitus accentuates hind limb ischemia-reperfusion injury.

METHODS

Male Wistar rats rendered diabetic (n=40) following injection of streptozotocin were compared to non-diabetic control rats (n=30). Each group was divided into sham, 4 hrs of hind limb ischemia, 4 hrs of ischemia followed by 10, 30 or 60 min of reperfusion. Plasma concentrations of an end-product of lipid peroxidation [malondialdehyde (MDA)] and antioxidants (vitamins A and E) were measured together with the resting membrane potential (RMP) of the gastrocnemius muscle.

RESULTS

Following reperfusion, the diabetic group showed greater and more persistent elevation of MDA and greater reduction of antioxidants. This was associated with reduction in the RMP only in the diabetic group. There was significant correlation between MDA level and the RMP in both groups of animals.

CONCLUSIONS

These results indicate that oxidative stress following reperfusion injury is greater in the presence of diabetes mellitus. This may lead to a decrease in the RMP and increase in the vascular permeability, which may be associated with more complications.

Oxidative stress in lavage fluid of preterm infants at risk of chronic lung disease

There is evidence that oxidative stress plays a role in the development of chronic lung disease (CLD), with immature lungs being particularly sensitive to the injurious effect of oxygen and mechanical ventilation. We analyzed total ascorbate, urate, and protein carbonyls in 102 bronchoalveolar lavage fluid samples from 38 babies (33 preterm, 24-36 wk gestation; 5 term, 37-39 wk gestation). Preterm babies had significantly decreasing concentrations of ascorbate, urate, and protein carbonyls during the first 9 days of life (days 1-3, 4-6, and 7-9, Kruskal-Wallis ANOVA: P = 0.016, P < 0.0001, and P = 0.010, respectively). Preterm babies had significantly higher protein carbonyl concentrations at days 1-3 and 4-6 (P = 0.005 and P = 0.044) compared with term babies. Very preterm babies (24-28 wk gestation) had increased concentrations of protein carbonyls at days 4-6 (P = 0.056) and significantly decreased ascorbate concentrations at days 4-6 (P = 0.004) compared with preterm babies (29-36 wk gestation). Urate concentrations were significantly elevated at days 1-3 (P = 0.023) in preterm babies who subsequently developed CLD. This study has shown the presence of oxidative stress in the lungs of preterm babies during ventilation, especially in those who subsequently developed CLD.

Intermittent hypoxic training: implications for lipid peroxidation induced by acute normoxic exercise in active men

Oxidant generation during regular physical exercise training may influence the adaptive responses that have been shown to confer protection against oxidative stress induced by subsequent acute exercise. To examine this, we randomly assigned 32 males to either a normoxic (n=14) or a hypoxic (n=18) group. During the acute phase, subjects in the hypoxic group performed two maximal cycling tests in a randomized double-blind fashion: one under conditions of normoxia and the other under hypoxic conditions (inspired fraction of O(2)=0.21 and 0.16 respectively). During the intermittent phase, the normoxic and hypoxic groups each trained for 4 weeks at the same relative exercise intensity, under conditions of normoxia and hypoxia respectively. During acute exercise under hypoxic conditions, the venous concentrations of lipid hydroperoxides and malondialdehyde were increased, despite a comparatively lower maximal oxygen uptake (VO(2max)) (P<0.05 compared with normoxia). The increases in lipid hydroperoxides and malondialdehyde were correlated with the exercise-induced decrease in arterial haemoglobin oxygen saturation (r=-0.61 and r=-0.50 respectively; P<0.05), but not with VO(2max). Intermittent hypoxic training attenuated the increases in lipid hydroperoxides and malondialdehyde induced by acute normoxic exercise more effectively than did normoxic training, due to a selective mobilization of alpha-tocopherol (P<0.05). The latter was related to enhanced exercise-induced mobilization/oxidation of blood lipids due to a selective increase in VO(2max) (P<0.05 compared with normoxic group). We conclude that lipid peroxidation induced by acute exercise (1) increases during hypoxia; (2) is not regulated exclusively by a mass action effect of VO(2); and (3) is selectively attenuated by regular hypoxic training. Oxidative stress may thus be considered as a biological prerequisite for adaptation to physical stress in humans.

Mutually exclusive muscle designs: the power output of the locomotory and sonic muscles of the oyster toadfish (Opsanus tau)

Animals perform a vast array of motor activities. Although it has generally been accepted that muscles are well suited to the function that they must perform, specialization for performing one function may compromise their ability for carrying out another. We examined this principle in the toadfish muscular system: slow-twitch red and fast-twitch white myotomal muscles are used for powering swimming at relatively low frequencies, while the superfast swimbladder muscle powers mating calls by contracting at 100 Hz. We measured muscle power output over a wide range of frequencies. The red and white locomotory muscles could not generate power over ca. 2.2 and 12 Hz, respectively and, hence, could not power sound production. In contrast, the swimbladder muscle has many specializations that permit it to generate power at frequencies in excess of 100 Hz. However, these specializations drastically reduce its power output at low frequencies: the swimbladder muscle generated only one-twentieth of the power of the red muscle and one-seventh of the power of the white muscle at the frequencies used during swimming. To generate the same total power needed for swimming would require unfeasibly large amounts of swimbladder muscle that could not fit into the fish. Hence, the designs of the swimbladder and locomotory muscles are mutually exclusive.

Lipoprotein oxidation and atherosclerosis

Lipoprotein oxidation is a key early stage in the development of atherosclerosis. Oxidation of low-density lipoprotein (LDL) is initiated by both enzyme-mediated and non-enzymic mechanisms in vivo, and oxidized LDL has many atherogenic properties. Oxidation of LDL in vivo is likely to be influenced by local environmental factors, such as pH. The composition of LDL is also important, including such factors as antioxidant content, fatty acid composition and particle size.

Effect of a COL1A1 Sp1 binding site polymorphism on arterial pulse wave velocity: an index of compliance

-Reduced arterial compliance precedes changes in blood pressure, which may be mediated through alterations in vessel wall matrix composition. We investigated the effect of the collagen type I-alpha1 gene (COL1A1) +2046G>T polymorphism on arterial compliance in healthy individuals. We recruited 489 subjects (251 men and 238 women; mean age, 22.6+/-1.6 years). COL1A1 genotypes were determined using polymerase chain reaction and digestion by restriction enzyme Bal1. Arterial pulse wave velocities were measured in 3 segments, aortoiliac (PWVA), aortoradial (PWVB), and aorto-dorsalis-pedis (PWVF), as an index of compliance using a noninvasive optical method. Data were available for 455 subjects. The sample was in Hardy-Weinberg equilibrium with genotype distributions and allele frequencies that were not significantly different from those reported previously. The T allele frequency was 0.22 (95% confidence interval, 0.19 to 0.24). Two hundred eighty-three (62.2%) subjects were genotype GG, 148 (35.5%) subjects were genotype GT, and 24 (5.3%) subjects were genotype TT. A comparison of GG homozygotes with GT and TT individuals demonstrated a statistically significant association with arterial compliance: PWVF 4.92+/-0.03 versus 5.06+/-0.05 m/s (ANOVA, P=0.009), PWVB 4.20+/-0.03 versus 4.32+/-0.04 m/s (ANOVA, P=0.036), and PWVA 3.07+/-0.03 versus 3.15+/-0.03 m/s (ANOVA, P=0.045). The effects of genotype were independent of age, gender, smoking, mean arterial pressure, body mass index, family history of hypertension, and activity scores. We report an association between the COL1A1 gene polymorphism and arterial compliance. Alterations in arterial collagen type 1A deposition may play a role in the regulation of arterial compliance.

Measurement of asialylated LDL in the blood of patients with coronary artery disease by antibody-lectin sandwich assay

Elevated concentrations of asialylated LDL (asialo-LDL) have been reported in patients with coronary artery disease (CAD). This may stimulate lipid accumulation in arterial intima cells and promote atherosclerosis. To investigate asialo-LDL as a potential risk-factor for coronary atherogenesis, we developed an antibody-lectin sandwich assay to measure levels in serum from CAD patients and age-matched control subjects. LDL was captured with an anti-apolipoprotein (apo) B antibody and asialylated oligosaccharides measured using the biotinylated D-galactose (D-gal) binding lectin, Ricinus communis agglutinin 120 (RCA120), and a streptavidin-alkaline phosphatase conjugate. For the control and atherosclerotic subjects, median [interquartile range (IQR)] values for total concentrations of asialo-LDL were 240 mg,L (180-310 mg/L) and 220 mg/L (186-390 mg/L), respectively (P = 0.82). When expressed as a percentage of serum apo B-100, median (IQR) values were 18% (16-23%) and 19% (15-29%), respectively (P = 0.78). These results suggest asialo-LDL has little value as a risk factor for coronary atherosclerosis.

The methionine synthase reductase (MTRR) A66G polymorphism is a novel genetic determinant of plasma homocysteine concentrations

Epidemiological evidence has revealed that an elevated plasma homocysteine level (hyperhomocysteinemia) confers an increased risk of cardiovascular disease and neural tube defects. Hyperhomocysteinemia is caused by both nutritional (e.g. folate, vitamins B(6) and B(12)) and genetic factors, including functional polymorphisms of key enzymes involved in homocysteine metabolism. One such enzyme, methionine synthase reductase (MTRR), maintains adequate levels of methylcob(III)alamin, the activated cofactor for methionine synthase, which catalyzes the remethylation of homocysteine to methionine. A common MTRR polymorphism, i.e. a 66 A-->G substitution specifying an isoleucine to methionine substitution (I22M), was recently identified. To assess the influence of this polymorphism on total plasma homocysteine (tHcy), we undertook a genotype/phenotype analysis in a study population of 601 Northern-Irish men, aged 30--49, for which biochemical and genetic data relevant to folate/homocysteine metabolism had already been acquired. The 66AA genotype has a frequency of 29% in this population. We established that there was a significant influence of MTRR genotype on tHcy ranking (P=0.004) and that the 66AA genotype contributes to a moderate increase in tHcy levels across the distribution [OR 1.59 (95% CI: 1.10--2.25) for the 66AA genotype to be in the upper half of the tHcy distribution, P=0.03]. The homocysteine-elevating effect of the 66AA genotype is independent of serum folate, vitamin B(12) and vitamin B(6) levels. Based on published estimates of the enhanced cardiovascular disease risk conferred by defined increments of plasma tHcy, we estimate that 66AA homozygotes have, on average, an approximately 4% increase in cardiovascular disease risk compared to 66GG homozygotes. This study provides the first evidence that the MTRR A66G polymorphism significantly influences the circulating tHcy concentration.

Oxidative stress and increased type-IV collagenase levels in bronchoalveolar lavage fluid from newborn babies

Oxidative stress may increase lung permeability by up-regulation of matrix-metalloproteinase-9 (MMP-9), a type-IV collagenase that can disrupt alveolar basement membranes. We have compared a marker of oxidative stress (protein carbonyl residues) with levels of MMP-9 and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), in bronchoalveolar lavage samples from newborn babies. Bronchoalveolar lavage samples (n = 87, two from each time point) were taken in the first 6 postnatal days from 41 ventilated babies: 18 of <29 wk gestation, 10 of 29-36 wk, 9 term with persistent fetal circulation, and 4 term without lung disease. Respiratory disease severity at the time of bronchoalveolar lavage was assessed using the arterial-alveolar oxygen tension ratio. One sample from each time point was used for the measurement of MMP-9 by zymography and TIMP-1 by ELISA. The second sample was used to measure carbonyl group concentrations, also using an ELISA. Correlations were calculated between protein carbonyls, arterial-alveolar oxygen tension ratio, and MMP-9 and TIMP-1 concentrations. Significant correlations were found between carbonyl concentrations and arterial-alveolar oxygen tension ratio (r = -0.325, p = 0.0031, n = 81), MMP-9 (r = 0.331, p < 0.0029, n = 79), and TIMP-1 (r = 0.436, p < 0.0001, n = 87). Worsening respiratory disease in newborn babies is associated with increased carbonyl concentrations in neonatal bronchoalveolar lavage fluid, and these correlated with MMP-9 and TIMP-1 levels. Increased oxidative stress may damage the lung by increasing type-IV collagenase activity, causing disruption of the extracellular matrix.