Ignacio Monreal

Serum Carboxy-Terminal Propeptide of Procollagen Type I Is a Marker of Myocardial Fibrosis in Hypertensive Heart Disease

BACKGROUND This study was designed to investigate whether the serum concentration of the carboxy-terminal propeptide of procollagen type I (PIP), a marker of collagen type I synthesis, is related to myocardial fibrosis in hypertensive patients. METHODS AND RESULTS The study was performed in 26 patients with essential hypertension in which ischemic cardiomyopathy was excluded after a complete medical workup. Right septal endomyocardial biopsies were performed in hypertensive patients to quantify collagen content. Collagen volume fraction (CVF) was determined on picrosirius red-stained sections with an automated image analysis system. The serum concentration of PIP was measured by specific radioimmunoassay. Compared with normotensives, both serum PIP and CVF were increased (P<0.001) in hypertensives. A direct correlation was found between CVF and serum PIP (r=0.471, P<0.02) in all hypertensives. Histological analysis revealed the presence of 2 subgroups of patients: 8 with severe fibrosis and 18 with nonsevere fibrosis. Serum PIP was higher (P<0.05) in patients with severe fibrosis than in patients with nonsevere fibrosis. Using receiver operating characteristic curves, we observed that a cutoff of 127 microg/L for PIP provided 78% specificity and 75% sensitivity for predicting severe fibrosis with a relative risk of 4.80 (95% CI, 1.19 to 19.30). CONCLUSIONS These results show a strong correlation between myocardial collagen content and the serum concentration of PIP in essential hypertension. Although preliminary, these findings suggest that the determination of PIP may be an easy and reliable method for the screening and diagnosis of severe myocardial fibrosis associated with arterial hypertension.

Abnormalities of the Extracellular Degradation of Collagen Type I in Essential Hypertension

BACKGROUND This study was designed to investigate whether collagen type I degradation is altered in patients with essential hypertension and whether this alteration could be related to disturbances in the serum matrix metalloproteinase pathway of collagen degradation. A second aim of the study was to assess whether some relation exists between serum markers of collagen type I degradation and left ventricular hypertrophy in hypertensive patients. METHODS AND RESULTS We measured serum concentrations of carboxy-terminal telopeptide of collagen type I (CITP) as a marker of extracellular collagen type I degradation, of total matrix metalloproteinase-1 (MMP-1), or collagenase, of total tissue inhibitor of metalloproteinases 1 (TIMP-1), and of MMP-1/TIMP-1 complex in 37 patients with never-treated essential hypertension and in 23 normotensive control subjects. Serum concentrations of free MMP-1 and free TIMP-1 were calculated by subtracting the values of MMP-1/TIMP-1 complex from the values of total MMP-1 and total TIMP-1, respectively. Measurements were repeated in 26 hypertensive patients after 1 year of treatment with the ACE inhibitor lisinopril. Baseline free MMP-1 was decreased (P<0.001) and baseline free TIMP-1 was increased (P<0.001) in hypertensives compared with normotensives. No significant differences were observed in the baseline values of CITP between the 2 groups of subjects. Hypertensive patients with baseline left ventricular hypertrophy exhibited lower values of free MMP-1 (P<0.01) and CITP (P<0.05) and higher (P<0.001) values of free TIMP-1 than hypertensive patients without baseline left ventricular hypertrophy. Treated patients attained an increase (P<0.001) in free MMP-1 and a decrease (P<0.05) in free TIMP-1. In addition, serum CITP was increased (P<0.05) in treated hypertensives compared with normotensive subjects. CONCLUSIONS These findings suggest that systemic extracellular degradation of collagen type I is depressed in patients with essential hypertension and can be normalized by treatment with lisinopril. A depressed degradation of collagen type I may facilitate organ fibrosis in hypertensive patients, namely, in those with left ventricular hypertrophy.

Increased Serum Concentrations of Procollagen Peptides in Essential Hypertension Relation to Cardiac Alterations

BACKGROUND The serum concentrations of two procollagen-derived peptides, procollagen type III amino terminal peptide (PIIIP) and procollagen type I carboxy terminal peptide (PIP), have been proposed as useful markers of the tissue synthesis of collagen type III and type I, respectively. Therefore, this study was designed to evaluate fibrogenic activity in patients with essential hypertension by measuring serum PIIIP and PIP. Furthermore, since hypertensive heart disease is characterized by myocardial accumulation of collagen type III and type I, a second aim of the study was to assess whether some relation exists between the serum concentrations of PIIIP and PIP and several parameters of left ventricular anatomy and function in hypertensive patients. METHODS AND RESULTS The study was performed in 50 patients with never-treated essential hypertension and in 30 normotensive control subjects. Measurements were repeated in 43 hypertensive patients after 6 months of treatment with the angiotensin-converting enzyme inhibitor lisinopril. The serum concentrations of PIIIP and PIP were measured by specific radioimmunoassay. Two-dimensional, targeted M-mode and Doppler ultrasound recordings were obtained in every subject to determine several parameters of the left ventricle anatomy and function. Ambulatory ECG monitoring was performed in each patient, and the recorded ventricular arrhythmias were categorized according to Lown-Wolf classification. Baseline serum PIIIP and PIP were increased (P < .001) in hypertensive patients as compared with normotensive subjects. An inverse correlation was found between serum PIIIP and the ratio between maximal early transmitral flow velocity and maximal late transmitral flow velocity measured during diastole (r = .3786, P < .01) in the group of hypertensive patients. Serum PIP was correlated directly with the left ventricular mass index (r = .3277, P < .05) in the group of hypertensive patients. Serum PIP concentrations increased in parallel with the increase in the grade of ventricular arrhythmias in the group of hypertensive patients. Treated patients attained normalization in blood pressure, amelioration of diastolic filling, regression of left ventricular mass index, and a diminution in the number of daily ventricular extrasystoles. In addition, serum PIIIP and PIP concentrations decreased significantly (P < .001) to normal values in patients treated with lisinopril. CONCLUSIONS These findings suggest that tissue synthesis of collagen type III and type I is abnormally increased in essential hypertension and can be normalized by treatment with lisinopril. On the other hand, our results suggest that serum PIIIP and PIP are related to several anatomic and functional alterations of the hypertensive left ventricle. Serum procollagen peptide measurements may therefore provide indirect diagnostic information on the myocardial fibrosis associated with arterial hypertension.

Losartan inhibits the post-transcriptional synthesis of collagen type I and reverses left ventricular fibrosis in spontaneously hypertensive rats

OBJECTIVE Previous studies have shown that as well as left ventricular hypertrophy, myocardial fibrosis develops early in rats with spontaneous hypertension (SHR). The present study was designed to investigate whether chronic treatment with the angiotensin II type 1 (AT1) receptor antagonist losartan modifies collagen type I metabolism and reverses left ventricular fibrosis in young SHR with left ventricular hypertrophy. DESIGN The study was performed in 30-week-old normotensive Wistar-Kyoto (WKY) rats, untreated SHR and SHR treated with losartan (20 mg/mg per day, orally) for 14 weeks before they were killed. METHODS Ventricular pro-alpha 1 (I) collagen messenger RNA was analyzed by Northern blot. Serum levels of the carboxy-terminal propeptide of procollagen type I (PIP) and the pyridoline cross-linked telopeptide domain of collagen type I (CITP) were determined by specific radioimmunoassays as markers of collagen type I synthesis and degradation, respectively. Collagen volume fraction was determined in the left ventricle by quantitative morphometry. RESULTS Compared with WKY rats, SHR exhibited increased (P < 0.05) mean arterial pressure, pro-alpha 1 (I) collagen messenger RNA, PIP and left ventricular collagen volume fraction, and similar CITP values. After the treatment period, mean arterial pressure was higher (P < 0.05) in losartan-treated SHR than in WKY rats. Compared with untreated SHR, treated SHR showed no left ventricular hypertrophy and diminished (P < 0.05) values of mean arterial pressure, PIP and left ventricular collagen volume fraction. No changes in pro-alpha 1 (I) collagen messenger RNA and CITP values were observed with treatment in SHR. No significant differences in the left ventricular collagen volume fraction were observed between treated SHR with normal blood pressure and treated SHR with abnormally high blood pressure at the end of the treatment period. CONCLUSIONS These results suggest that chronic AT1 blockade with losartan decreases the post-transcriptional synthesis of fibril-forming collagen type I molecules in young SHR. This effect may be involved in the ability of this drug to reverse left ventricular fibrosis in young rats with genetic hypertension. Apart from its antihypertensive action, other mechanisms may mediate the antifibrotic effect of losartan in this animal model.

Serum Markers of Collagen Type I Metabolism in Spontaneously Hypertensive Rats Relation to Myocardial Fibrosis

BACKGROUND The assay of serum peptides of extracellular collagen synthesis and degradation could provide an indirect estimate of the rate of fibrillar turnover. This study was designed to investigate whether serum peptides of collagen type I synthesis and degradation are altered in spontaneously hypertensive rats (SHR) with left ventricular hypertrophy and whether these serum collagen-derived peptides are related to myocardial fibrosis. METHODS AND RESULTS We measured serum levels of carboxyterminal propeptide of procollagen type I (PIP) as a marker of collagen I synthesis and serum levels of the pyridinoline crosslinked telopeptide domain of collagen type I (CITP) as a marker of fibrillar collagen I degradation in ten 36-week-old normotensive Wistar-Kyoto (WKY) rats, ten 36-week-old SHR, and ten 16-week-old SHR treated with the angiotensin-converting enzyme inhibitor quinapril (10 mg /kg body wt per day, orally) for 20 weeks. PIP and CITP were determined by specific radioimmunoassays. Histomorphometric and immunohistochemical studies of the left ventricle were performed in all rats. In untreated SHR compared with WKY rats, we found a more extensive interstitial and perivascular fibrosis, an increased (P<.01) collagen volume fraction, a more marked deposition of collagen type I, an increased (P<.01) serum concentration of PIP, and a similar serum concentration of CITP. In quinapril-treated SHR compared with untreated SHR, we found an absence of left ventricular hypertrophy, a marked decrease of fibrosis, a lower (P<.01) collagen volume fraction, a diminished deposition of collagen type I, a decreased (P<.01) concentration of PIP, and a similar concentration of CITP. A direct correlation was found between the collagen volume fraction and serum PIP (r=.753, P<.05) in untreated SHR. CONCLUSIONS These results suggest that tissue metabolism of collagen type I is abnormal in SHR and can be normalized by treatment with quinapril. On the basis of our findings, we propose that serum PIP may be a marker of collagen type I-dependent myocardial fibrosis in rats with genetic hypertension.

Independent Association of Fibrinogen with Carotid Intima-Media Thickness in Asymptomatic Subjects

Background: Fibrinogen has been found to be an independent risk factor for cardiovascular disease. Both genetic and environmental factors contribute to its variability in plasma. However, whether the relation between fibrinogen and carotid intima-media thickness (IMT) is independent of those factors has not been established. Therefore, the aim of this study was to investigate the relations of plasma fibrinogens and the –455 G/A Bβ-fibrinogen polymorphism with the carotid IMT in a series of asymptomatic subjects. Methods: Markers of inflammation, C-reactive protein (CRP) and leukocytes, and endothelial perturbation (von Willebrand factor, vWF) were measured in 135 subjects. All individuals underwent a complete clinical examination and lipid measurements (cholesterol and its fractions HDL and LDL and triglycerides). The carotid IMT was measured by B-mode ultrasound in the common carotid artery. Results: Patients in the highest fibrinogen tertile had a significantly higher BMI (p < 0.01), LDL-cholesterol (p < 0.01), leukocyte count, CRP and vWF (p < 0.001). In the univariate model a strong positive relationship was found between plasma fibrinogen and carotid IMT (p < 0.01). Fibrinogen also correlated positively with age, BMI, arterial systolic pressure, cholesterol, cholesterol-LDL, smoking, CRP and vWF (p < 0.01). In the multivariate analysis, the association of fibrinogen with carotid IMT remained significant (p < 0.01) after adjustment for all the parameters analyzed. Conclusion: In a population sample of adults without clinically overt atherosclerotic disease, elevated fibrinogen was related to carotid IMT independent of a wide range of important confounding variables.

Insulin-like growth factor binding proteins in arterial hypertension : relationship to left ventricular hypertrophy

Objective It was reported previously that circulating insulin-like growth factor I levels are abnormally elevated in patients with essential hypertension and left ventricular hypertrophy. Tissue availability of the factor depends on the distribution of the circulating bound factor between its high-and low-molecular mass binding proteins, only the latter being able to cross the endothelium. The aim of this study was to investigate whether the presence of the different serum binding proteins is altered in patients with essential hypertension and left ventricular hypertrophy. Design The study was performed in 30 never-treated patients with essential hypertension and 30 age-and sex-matched normotensive subjects. Patients were separated into two groups according to the presence or the absence of echocardiographically determined left ventricular hypertrophy. Methods Plasma insulin-like growth factor I levels were determined by specific radioimmunoassay. The different molecular forms of its serum binding proteins were analysed by Western blotting using [125I]-labelled insulin-like growth factor I. A densitometric scanning of the blots was performed to analyse the quantitative relationships between the different forms of binding proteins. Results Insulin-like growth factor I levels were significantly higher in the hypertensive patients with than in the hypertensive patients without left ventricular hypertrophy or in the normotensive subjects. Compared with the normotensive subjects, both hypertensive patients subgroups exhibited increased high-molecular mass binding protein type 3 and decreased low-molecular mass binding proteins types 1 and 2. However, changes in the binding proteins were more marked in the hypertensive patients without than in the hypertensive patients with left ventricular hypertrophy. Accordingly, the ratio of low-to high-molecular mass binding proteins (an index of insulin-like growth factor I bioavailability) was higher in the hypertensive patients with than in the hypertensive patients without left ventricular hypertrophy. Conclusions These results show that the distribution of the molecular forms of serum insulin-like growth factor binding proteins is altered in patients with essential hypertension, independently of insulin-like growth factor I levels. This suggests that regulation of the binding proteins is abnormal in essential hypertension. Whether the tissue availability of circulating insulin-like growth factor I is higher in hypertensive patients with than in hypertensive patients without left ventricular hypertrophy merits further investigation.

Laboratory approach to mitochondrial diseases

Dysfunction in mitochondrial processes has been related to several pathologies. In these disorders, the cell suffers oxidative imbalance that is mostly due to defects in pyruvate metabolism, mitochondrial fatty acids oxidation, the citric acid cycle or electron transport by the mitochondrial respiratory chain. These metabolic alterations produce mitochondrial diseases that have been related to inherited syndromes, such as MERRF or MELAS. The main affected organs are brain, skeletal muscle, kidney, heart and liver, because of the high energetic demand and the oxidative metabolism. Moreover, the relationship between mitochondrial dysfunction and neurodegenerative processes, such as Parkinson disease or Alzheimer disease, as well as ageing, has been shown. Because mitochondrias are the target of several xenobiotics, such as aspirin, AZT or alcohol consumption, motochondrial impairment has also been proposed as a mechanism of toxicity. Most laboratory tests that are available in the diagnosis of mitochondrial illness are assayed in tissue biopsies and are usually difficult to interpret. Recently, it has been shown that non-invasive techniques, such as nuclear magnetic resonance or the 2-keto [1-13C] isocaproic acid breath test, may be useful to assess mitochondrial function. This article attempts to show the laboratory approach to mitochondrial diseases, reviewing new techniques that could be of great value in the research of mitochondrial function, such as the 2-keto[1-13C]isocaproic breath test.ResumenLa alteración de la función mitocondrial se ha relacionado con una amplia gama de patologías de origen diverso. Básicamente, los defectos en el metabolismo del piruvato y en la oxidación mitocondrial de los ácidos grasos, junto con deficiencias en el ciclo del ácido cítrico y en el funcionamiento de la cadena respiratoria, generan un estado de estrés oxidativo en las células que sufren este tipo de desórdenes. Estas alteraciones mitocondriales no sólo están presentes en síndromes congénitos como MERRF o MELAS sino que también se han relacionado con procesos neurodegenerativos, como la enfermedad de Alzheimer o la enfermedad de Parkinson, con el proceso de envejecimiento y con el mecanismo de toxicidad de diversos xenobióticos, come el alcohol o la aspirina.La mayor parte de las pruebas disponibles en el laboratorio para estudiar la función mitocondrial, presentan una interpretación difícil además de requerir una toma de muestra cruenta, ya que el estudio suele realizarse en biopsias. Recientemente, se han propuesto técnicas no invasivas, como la resonancia magnética nuclear y las pruebas de aliento con isótopos estables, como pruebas útiles en el estudio de la función mitocondrial.El objetivo de este trabajo es la revisión de las pruebas disponibles en el laboratorio para el estudio de las citopatías mitocondriales y de las técnicas empleadas, mostrando nuevas pruebas que pueden resultar útiles en el estudio de la función mitocondrial, como el test del aliento del ácido 2-ceto[1-13C]isocaproico.

Traditional and Novel Bone Remodeling Markers in Premenopausal and Postmenopausal Women

CONTEXT Bone turnover markers (BTMs) may identify changes in bone remodeling within a relatively short time interval before changes in bone mineral density can be detected. New markers such as osteoprotegerin, receptor activator of nuclear factor-κB ligand, and sclerostin have emerged, but there is little information about their potential use in clinical practice. OBJECTIVES The aim of this study was to analyze the ability of several BTMs to predict bone loss in pre- and postmenopausal women and to monitor the efficacy of treatment in osteoporotic women. DESIGN, PATIENTS, AND SETTING We performed an observational prospective study in pre- and postmenopausal ambulatory women (n = 72 and n = 152, respectively). INTERVENTION Postmenopausal women with osteoporosis (n = 18) were treated with risedronate and calcium. Women filled out a questionnaire and underwent bone mineral density measurement using dual-energy x-ray absorptiometry at the time of enrollment and after 1 year of follow-up. BTMs were measured at baseline, at 6 months, and after 1 year. RESULTS Increased levels of N-terminal propeptide of type 1 procollagen (P1NP) and β-type I collagen telopeptides (CTXs) were associated with low bone mineral density in the premenopausal (P = .02 and P = .04, respectively) and postmenopausal (P = .03 and P = .02) groups. The best analytical performance to diagnose osteoporosis was for β-CTX, osteocalcin, and P1NP, with areas under the curve of 0.70 (P = .005), 0.64 (P = .048), and 0.71 (P = .003). A significant decrease was found in P1NP, osteocalcin, tartrate-resistant acid phosphatase-5b, β-CTX, and bone alkaline phosphatase after 1 year of treatment (all P < .05). CONCLUSIONS Our data suggest that measurement of β-CTX and P1NP shows adequate analytical performance and could potentially be included in algorithms for the screening of osteoporosis. Furthermore, these two markers, along with osteocalcin and tartrate-resistant acid phosphatase-5b, are useful to monitor the response to risedronate.

Tissue availability of insulin-like growth factor I is inversely related to insulin resistance in essential hypertension: effects of angiotensin converting enzyme inhibition.

Background The insulin-like growth factor I possesses biologic actions that resemble those of insulin. Tissue access of the factor depends on the distribution of the circulating bound factor between its binding protein 3 that remains within the intravascular space and its binding protein I that is able to cross the endothelium. Preliminary results have shown that tissue availability of insulin-like growth factor I is a determinant of glucose regulation in essential hypertension Objective To investigate whether the tissue availability of circulating insulin-like growth factor I in patients with essential hypertension is related to insulin resistance and whether chronic angiotensin converting enzyme inhibition influences tissue availability of the factor and insulin resistance in these patients. Design and methods We studied 29 patients with essential hypertension and 20 age-matched and sex-matched normotensive subjects. The measurements were repeated for 25 patients after 12 months of treatment with lisinopril. Tissue availability of circulating insulin-like growth factor I was assessed by analyzing its distribution between its binding proteins 3 and 1. An insulin resistance index was estimated using the homeostasis model analysis of fasting insulin–glucose interactions. Levels of serum insulin-like growth factor I binding proteins 3 and 1, plasma insulin-like growth factor I, and insulin were determined by specific radioimmunoassays. Results Baseline insulin resistance index was significantly higher in the hypertensive patients than it was in the normotensive controls. With the upper 100% confidence limit of the normotensive population as the cutoff point, a subgroup of 12 hypertensives had an abnormally high insulin resistance index. Compared with patients with normal insulin resistance indexes, patients with greater than normal indexes were characterized by lower binding protein 1 levels, similar binding protein 3 levels, lower binding protein 1: binding protein 3 ratio and similar insulin-like growth factor I levels. The serum binding protein 1 level and the binding protein 1: binding protein 3 ratio were inversely correlated to the insulin resistance index for the whole group of hypertensives. After treatment with lisinopril hypertensive patients with higher than normal insulin resistance indexes at baseline exhibited normalization of this parameter and significant increases of binding protein 1 levels and binding protein 1: binding protein 3 ratio, with no significant changes in insulin-like growth factor I levels. These parameters remained unchanged for the remaining patients. Conclusions These results suggest that tissue availability of circulating insulin-like growth factor I is a determinant of insulin sensitivity in patients with essential hypertension. Whereas the patients with normal insulin sensitivity exhibit greater than normal tissue access of circulating insulin-like growth factor I, patients with insulin resistance present normal tissue access of the factor. Our findings suggest that the ability of angiotensin converting enzyme inhibitors to restore insulin sensitivity in essential hypertensives may be related to their ability to facilitate the tissue availability of circulating insulin-like growth factor I.