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Muzahir H Tayebjee

Publications and source records attributed to Muzahir H Tayebjee.

At least 19 recordsLinked to original sources
PubMed2006

Target organ damage in hypertension: pathophysiology and implications for drug therapy.

Hypertension is a well known risk factor for cardiovascular and cerebrovascular events such as heart attacks and strokes. In addition, it is associated with earlier changes in organ systems in the body, such as left ventricular hypertrophy (LVH), proteinuria and renal failure, retinopathy and vascular dementia which are grouped under the term "target organ damage" (TOD). There are many processes involved in the pathogenesis of TOD and these include endothelial activation, platelet activation, increased thrombogenesis, changes in the renin aldosterone angiotensin system (RAAS), and collagen turnover. All these changes work hand in hand and lead to the production of hypertensive TOD. In this review, we aim to provide an overview of the recent advances in pathophysiology of hypertensive TOD, and examine how these changes lead to the production of TOD. A better understanding of these pathogenic processes would help us better devise treatment strategies in preventing the dreaded complications associated with hypertension.

Blood Platelets↗
PubMed2005

Plasma matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-2, and CD40 ligand levels in patients with stable coronary artery disease.

Endogenous matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitor of metalloproteinases (TIMPs), are important mediators of extracellular matrix remodeling, which is integral to plaque progression in coronary artery disease. In addition, high levels of the soluble fragment of CD40 ligand (sCD40L) have previously been associated with adverse cardiovascular outcomes. We hypothesized that circulating levels of MMP-9, TIMP-1, TIMP-2, and sCD40L were abnormal in patients who had stable coronary artery disease, and these levels were compared with those in matched controls. We also hypothesized correlations of MMPs, TIMPs, and sCD40L to each other and to high-sensitivity C-reactive protein (a proinflammatory marker), white blood cell count, severity of coronary artery disease (based on angiographic measurements of atherosclerotic burden), and coronary collateralization. We studied 204 adult patients who attended our unit for outpatient diagnostic cardiac catheterization for the investigation of suspected coronary artery disease. Coronary angiograms were scored for atheroma burden and stenosis by 2 independent observers. Circulating levels of MMP-9, TIMP-1, TIMP-2, and sCD40L were measured by enzyme-linked immunosorbent assay. Plasma levels of MMP-9 (p = 0.0099), TIMP-2 (p = 0.0019), and sCD40L (p <0.001), but not TIMP-1 (p = 0.463) were high in patients compared with healthy controls. In patients who had coronary artery disease, MMP-9 and high-sensitivity C-reactive protein levels were significantly higher in women than in men. Only MMP-9 correlated modestly with total white blood cell count (Spearman's correlation, r = 0.274, p = 0.002). Logistic regression of cardiovascular risk factors showed that only white blood cell count was independently associated with MMP-9 (p = 0.02). After standardizing for atheroma and stenosis scores, there were no statistically significant differences in our research indexes in patients who had angiographic collaterals compared with those who did not. In conclusion, stable coronary artery disease is associated with abnormal circulating levels of MMP-9, TIMP-2, and sCD40L, which do not appear to related to each other or to severity of coronary artery disease or collateralization. The gender difference in high-sensitivity C-reactive protein and MMP-9 levels may provide insight into the pathophysiology of coronary artery disease in men and women, and further studies are warranted to explore this potential link.

Aged↗
PubMed2005

Relation of platelet activation to coronary angiographic severity and collateralization.

We investigated whether platelet activation can be correlated with angiographic severity and the degree of collateralization in coronary artery disease (CAD), as well as endothelial damage/dysfunction. No studies have attempted to correlate platelet activation status, as measured by soluble plasma markers (soluble CD40 ligand, soluble P-selectin, soluble glycoprotein V), with the appearance of diseased coronary arteries. We found evidence of increased platelet activation in CAD, but a lack of correlation between the degree of platelet activation and the angiographic disease severity, which may reflect the presence of disease elsewhere or the presence of coronary atheroma not detected by angiography.

Aged↗
PubMed2005

Circulating matrix metalloproteinase-9 and tissue inhibitors of metalloproteinases-1 and -2 levels in gestational hypertension.

BACKGROUND: Gestational hypertension (GH) is dangerous to both mother and child. Arterial invasiveness and growth are dependent on successful extracellular matrix (ECM) breakdown, which may be abnormal in GH. We hypothesized abnormalities in circulating matrix metalloproteinase-9 (MMP-9) and tissue inhibitors of metalloproteinases-1 and -2 (TIMP-1 and TIMP-2, respectively) in patients with GH, when compared with normotensive women with normal pregnancies and healthy nonpregnant control subjects. METHODS: Plasma MMP-9, TIMP-1, and TIMP-2 were measured by ELISA in 23 women with GH, 30 normotensive pregnant women, and 28 nonpregnant women who were matched for age, gestational age, and parity. RESULTS: Levels of circulating MMP-9, TIMP-1 and TIMP-2, and the MMP-9/TIMP-1 and MMP-9/TIMP-2 ratios were significantly different among the three groups (P = .026, P = .006, P = .007, P = .001 and P = .008 respectively). Within the GH group, MMP-9 and the MMP-9/TIMP-1 ratio correlated negatively with age (r = -0.581, P = .004 and r = -0.563, P = .005, respectively) and levels of diastolic blood pressure (r = -0.432, P = .040 and r = -0.461, P = .027, respectively). With multiple regression analysis, only age independently correlated with circulating levels of MMP-9 (P = .010); neither age nor levels of diastolic blood pressure had any effect on the MMP-9/TIMP-1 ratio. CONCLUSIONS: We have demonstrated altered MMP/TIMP ratios in maternal blood during GH. These observations suggest pregnancy-related changes in ECM breakdown and turnover. Given the importance of changes in ECM composition to vascular and cardiac structure in hypertension, we suggest that these observations may be related to the pathophysiology of human GH.

Adult↗
PubMed2005

Effects of age, gender, ethnicity, diurnal variation and exercise on circulating levels of matrix metalloproteinases (MMP)-2 and -9, and their inhibitors, tissue inhibitors of matrix metalloproteinases (TIMP)-1 and -2.

BACKGROUND: Circulating metalloproteinases (MMP) and their inhibitors (TIMP) are indices of vascular and cardiac tissue matrix turnover. However, the temporal changes and relationship of these parameters to age, gender, ethnicity and exercise have been poorly defined. We therefore studied these aspects on plasma levels of MMP-2 and -9 and TIMP-1 and -2, as the major metalloproteinases (and their inhibitors) implicated in pathophysiology of vascular disease. METHODS: Venous citrated blood was collected from 93 normal healthy volunteers from four ethnic groups (Afro-Caribbean, South Asian, Caucasian and Far Eastern) for a cross-sectional study. In addition, 20 separate healthy volunteers were studied during supine rest, before and immediately following peak treadmill stress using a Bruce protocol. MMP-2 and -9 and TIMP-1 and -2 were all measured by ELISA. RESULTS: There was a categorical distribution of MMP-2 concentration with individual subjects showing high levels, yet others being undetectable, although these changes were unrelated to age, gender or ethnicity. TIMP-1 and -2 showed a modest negative correlation with age (r=-0.251, p=0.015; r=-0.254, p=0.014). There was a positive correlation between MMP-2 and TIMP-2 (r=0.399, p<0.001), MMP-9 and TIMP-1 (r=0.45, p<0.001) and between TIMP-1 and TIMP-2 (r=0.275, p=0.008). When adjusted for age and gender, there were no significant differences in MMP-2 and TIMP-1 and -2 between the four ethnic groups. MMP-9 was significantly lower in the Far Eastern group compared to the other three ethnic groups (p=0.012). Only TIMP-1 (p=0.042) and TIMP-2 (p=0.024) were significantly altered after exercise. CONCLUSION: Age and exercise both have modest effects on circulating concentrations of TIMP-1 and-2. MMP-9 appears lower in individuals of Far Eastern/Chinese origin regardless of age or gender. The positive association between MMPs and TIMPs suggests that in healthy individuals, enzyme activity may be regulated by this interaction. The reasons for the categorical distribution of MMP-2 remain unclear but this would be important in any studies designed to use circulating MMPs as a surrogate for tissue MMPs around clinical events, such as myocardial infarction or in response to therapies affecting extracellular matrix composition.

Adult↗
PubMed2005

Elevated platelet microparticles in stable coronary artery disease are unrelated to disease severity or to indices of inflammation.

Platelet microparticles (PMPs), procoagulant membrane vesicles derived from activated platelets, are elevated in acute myocardial infarction and unstable angina but their relationship to inflammation and indices of coronary artery disease are unclear. We therefore hypothesised that PMPs are related to scores of coronary atheroma and/or coronary stenosis. Our study was completed by comparing PMP data with other platelet markers and with hs-CRP, marking inflammation. We recruited 54 patients attending for coronary angiography, comparing them to 35 age- and sex-matched controls. Peripheral blood was analysed for PMPs, percent platelets positive for CD62P and CD63 (all flow cytometry), soluble P selectin and hsCRP (both immunoassay). Patients exhibited higher PMPs, increased platelet %CD62P, %CD63 and soluble P selectin (all P < 0.01) and hs-CRP (P = 0.0167) than healthy controls. However, analysing only patients with an unequivocal classification, there were no significant (P </= 0.01) correlations with coronary atheroma or coronary stenosis. These findings provide no support for the hypothesis that PMPs are related to the degree of coronary artery disease and therefore may simply be a marker of widespread inappropriate platelet activity.

Aged↗
PubMed2005

Platelet microparticles and soluble P selectin in peripheral artery disease: relationship to extent of disease and platelet activation markers.

BACKGROUND: There is increased platelet activation in many cardiovascular diseases. This observation may explain the presence of increased levels of platelet microparticles (PMP) in these diseases. However, whether or not levels of PMPs inter-relate with other markers of platelet activation, such as soluble P-selectin, or with disease severity, is unknown. We therefore hypothesized raised PMP levels in stable peripheral artery disease (PAD) intermittent claudication (IC), with an additional increase in severe PAD critical limb ischaemia (CLI). Furthermore, we tested the hypothesis that PMP levels are correlated with other markers of platelet activation, such as soluble P-selectin, membrane bound P-selectin (CD62P) and 63. METHODS: Patients with PAD were recruited from the vascular outpatient and inpatient facilities at a teaching hospital. Age- and sex-matched controls were also recruited from healthy volunteers. Venous blood was obtained from 23 patients with severe disease (CLI), 36 with moderate disease (IC), and from 30 healthy controls. The percentage of platelets positive for CD62P and CD63, as well as the numbers of PMPs were defined by flow cytometry. Plasma soluble P selectin was measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: PMPs were increased relative to healthy controls in patients with IC, with a further increase in CLI (P<0.001). Soluble P selectin and CD62+ve platelets were raised in both patient groups, but there was no difference amongst the two patient groups. CD63+ve cells were raised only in CLI compared to healthy controls. In multivariate analysis, only PMP and soluble P selectin independently predicted disease severity, and the two markers correlated modestly (r=0.345, P<0.001). CONCLUSION: Increased PMP and soluble P selectin are both related to the severity of symptomatic PAD. However, it is uncertain if this relationship is a cause or effect of atherosclerosis. This finding may have clinical implications as PMPs have the potential to influence the progression of atheroma as well as promote thrombosis.

Aged↗
PubMed2005

Soluble CD40L in peripheral artery disease. Relationship with disease severity, platelet markers and the effects of angioplasty.

Although soluble CD40L (sCD40L, possibly derived from platelets and pro-inflammatory in vitro) may be implicated in thrombosis and haemostasis, there are little data in peripheral artery disease (PAD). We hypothesised the following: (a) that sCD40L relates to the clinical severity of PAD; and (b) that peripheral artery angioplasty acutely raises sCD40L levels. sCD40L was compared to established platelet markers soluble P selectin, platelet microparticles and platelet surface expression of CD62 and CD63. We recruited 36 healthy controls, 33 patients with intermittent claudication (IC), and 33 with symptomatically more severe critical limb ischaemia (CLI), measuring plasma markers by ELISA and membrane markers by flow cytometry. Eleven patients with CLI subsequently underwent peripheral artery angioplasty: blood was taken before and 10 minutes after the intervention. Results show that sCD40L was raised in IC at median 68 (IQR 28-333) pg/ml and in CLI at 64 (34-282) pg/mL compared to 35 (IQR 28-55) pg/ml in the healthy controls (p=0.009). Levels were no different between IC and CLI. The same distribution pattern was present for soluble P selectin, %platelets CD62+ve and CD63+ve. sCD40L failed to correlate significantly with ABPI (p=0.264), unlike %platelets CD62+ve (p=0.0032) and CD63+ve (p=0.009). Pre-angioplasty sCD40L level of 72 (35-610) ng/ml rose to 100 ng/ml (IQR=60-237)(p=0.018) post-angioplasty. Plasma sCD40L, in addition to other platelet indices, is raised in peripheral atherosclerosis and is increased by peripheral artery angioplasty, although levels seem unrelated to clinical severity. Failure to correlate with other markers suggest the platelet may not be the sole source of sCD40L, and that other cells may contribute to plasma levels.

Aged↗
PubMed2005

Matrix metalloproteinases in coronary artery disease: clinical and therapeutic implications and pathological significance.

Matrix metalloproteinases (MMP) and their inhibitors (TIMP) are central factors in the control of extracellular matrix turnover. They are important in normal physiology and also during a range of pathological states. Only recently has their role in cardiovascular disease been explored and their analysis through measurements in blood been studied. We have systematically identified clinical articles relevant to coronary artery disease from the last 10 years using MEDLINE. In this review we outline the structure, function and regulation of metalloproteinases and their key roles in angiogenesis, stable and unstable coronary artery disease. Metalloproteinases and their inhibitors are fundamental mediators of change in aging and atherosclerosis, the cell membrane, and in myocardial and vascular tissue. Defining their overall importance and understanding their complex interrelationships with pressure, thrombosis and local neural and hormonal tone will require detailed clinical study. The modulation of MMP and TIMP activity using drugs that affect the expression and function of these proteins will provide us with new ways to treat these serious and disabling diseases, and we explore potential mechanisms and treatments.

Animals↗
PubMed2004

Matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in hypertension and their relationship to cardiovascular risk and treatment: a substudy of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT).

BACKGROUND: Hypertension results in structural changes to the cardiac and vascular extracellular matrix (ECM). Matrix metalloproteinases (MMP) and their inhibitors (TIMP) may play a central role in the modulation of this matrix. We hypothesized that both MMP-9 and TIMP-1 would be abnormal in hypertension, reflecting alterations in ECM turnover, and that their circulating levels should be linked to cardiovascular (CHD) and stroke (CVA) risk scores using the Framingham equation. Second, we hypothesized that treatment would result in changes in ECM indices. METHODS: Plasma MMP-9 and TIMP-1 were measured before and after treatment (median 3 years) from 96 patients with uncontrolled hypertension participating in the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT). Pretreatment values were compared to circulating MMP-9 and TIMP-1 levels in 45 age- and sex-matched healthy controls. RESULTS: Circulating pretreatment MMP-9 and TIMP-1 levels were significantly higher in patients with hypertension than in the normotensive controls (P =.0041 and P =.0166, respectively). Plasma MMP-9 levels decreased, and TIMP-1 levels increased after treatment (P =.035 and P =.005, respectively). Levels of MMP-9 correlated with CHD risk (r = 0.317, P =.007) and HDL cholesterol (r = -0.237, P =.022), but not CVA risk. There were no significant correlations between TIMP-1 and CVA or CHD scores. CONCLUSIONS: Increased circulating MMP-9 and TIMP-1 at baseline in patients with hypertension could reflect an increased deposition and retention of type I collagen at the expense of other components of ECM within the cardiac and vascular ECM. After cardiovascular risk management, MMP-9 levels decreased and TIMP-1 levels increased. Elevated levels of MMP-9 also appeared to be associated with higher Framingham cardiovascular risk scores. Our observations suggest a possible role for these surrogate markers of tissue ECM composition and the prognosis of cardiovascular events in hypertension.

Aged↗
PubMed2004

Tissue inhibitor of metalloproteinase-1 and matrix metalloproteinase-9 levels in patients with hypertension Relationship to tissue Doppler indices of diastolic relaxation.

BACKGROUND: Hypertension, hypertensive heart disease, and left ventricular (LV) hypertrophy are integral to symptomatic diastolic heart failure. Tissue inhibitor of metalloproteinase-1 (TIMP-1) is linked to extracellular matrix fibrosis and is elevated in hypertension. We hypothesized a link between circulating TIMP-1, matrix metalloproteinase-9 (MMP-9), and resting echocardiographic LV filling parameters using tissue Doppler parameters of diastolic (dys)function. METHODS: Circulating MMP-9 and TIMP-1 levels were measured in citrated plasma by ELISA in 74 patients with hypertension (58 men, mean age 58 +/- 11 years) and 34 controls (23 men, mean age 53 +/- 13 years). All had confirmed normal short axis systolic contractility, with no significant wall motion abnormalities; the LV mass and standard resting tissue Doppler echocardiographic indices of diastolic function were also recorded. RESULTS: Both MMP-9 and TIMP-1 levels were higher in the hypertensive group (P =.0039 and P =.0054, respectively). When compared to controls, hypertensive patients had a greater LV mass (P =.0054), and differences in many of the parameters reflecting diastolic dysfunction (controls versus hypertensives: E: 0.71 +/- 0.15 v 0.81 +/- 0.15 m/sec, P =.004; A: 0.66 +/- 0.12 v 0.81 +/- 0.16 m/sec, P <.0001; e': 0.12 (0.09-0.14) v 0.09 (0.07-0.10) m/sec, P =.0017; e'/a': 1.20 (1.00-1.80) v 0.88 (0.71-1.05), P <.0001; E/e': 6.54 (4.75-7.14) v 8.89 (7.55-10.75), P <.0001, respectively). Within the hypertensive cohort, only TIMP-1 levels correlated with LV mass (r = 0.271, P =.024), LV mass index (r = 0.323, P =.007), and tissue Doppler parameters of diastolic dysfunction, including e' (r = -0.338, P =.005), a' (r = -0.350, P =.005), and E/e' (r = 0.334, P =.005). CONCLUSIONS: TIMP-1 is thought to increase tissue concentrations of collagen type I by preventing its breakdown by MMPs. Our findings therefore add weight to a hypothesis suggesting that TIMP-1 may be a key mediator of LV diastolic dysfunction through definition of ventricular matrix composition.

Adult↗