Serum prolidase activity as a marker of osteoporosis in type 2 diabetes mellitus

Prolidase could be considered a sign of inflammation associated with cigarette smoking

Objectives

Smoking causes inflammation, thickening, and narrowing of the airways. This inflammatory process is a reaction to free radicals and oxidants. Smoking affects collagen metabolism and tissue remodeling. Prolidase enzyme hydrolyzes iminodipeptides with hydroxyproline and C terminal proline. It plays a crucial role in the metabolism of collagen and the remodeling of the matrix. The present study aims to reveal the association of prolidase with inflammation caused by smoking and to compare serum prolidase levels with oxidative-antioxidative status in healthy individuals.

Methods

A total of 76 participants (38 smokers and 38 nonsmokers) were involved in the present study. Serum cotinine levels were measured to show the exposure to nicotine in tobacco smoke by using the competitive inhibition enzyme immunoassay method. Serum prolidase, total oxidant status (TOS), and total antioxidant status (TAS) were determined by the enzyme-linked immunosorbent (ELISA) method, respectively. The correlation between smoking, serum prolidase levels, TOS, and TAS was investigated.

Results

TAS and serum prolidase levels of smokers were considerably lower than those in non-smokers (p < 0.001, p = 0.012 respectively). However, no differences were observed in TOS between the two groups. There was no statistically significant correlation between serum prolidase levels, TAS, and TOS. Moreover, no relationship was observed between respiratory function parameters and serum prolidase levels.

Conclusion

To the best of our knowledge, the present study is the first study to demonstrate the role of prolidase in smoking-related inflammation. The results achieved in the present study suggest that smoking creates an imbalance in the oxidant-antioxidant activity. Smoking decreases prolidase levels, leading to decreased collagen turnover. Chronic pulmonary disease might be related to this decrease in collagen turnover.

THE RELATIONSHIP BETWEEN OXIDATIVE STRESS AND SERUM PROLIDASE ACTIVITY IN PATIENTS WITH DIABETIC NEPHROPATHY, RETINOPATHY AND NEUROPATHY

Amaç: Diyabetin mikrovasküler komplikasyonlarında oksidatif stresin belirteçlerini incelemek, prolidazın oksidatif stres göstergeleriyle ilişkisini incelemek, prolidazın prediktif değer olarak kullanılabilirliliğini araştırmaktır. Gereç ve Yöntemler: Çalışmaya 112 tip 2 Diyabetes Mellitusu (DM) olan hasta ve 44 sağlıklı kontrol birey alındı. Hastaların ayrıntılı anamnezleri alınıp fizik muayeneleri yapıldı. Açlık plazma glukozu (APG), hemoglobin A1c (HbA1C), kreatinin, spot idrarda mikrototal protein düzeyleri bakıldı. Göz dibi muayenesi ile diyabetik retinopati varlığı araştırıldı. Nöropati varlığı açısından nörolojik muayeneleri yapıldı. Ayrıca tüm hastaların sabah alınan kan örneğinde oksidatif stress için katalaz (CAT), superoksit dismutaz(SOD), glutatyon peroksidaz (GPx), malondialdehit (MDA), nitrik oksit(NO), serum prolidaz aktivitesi ölçümü yapıldı. Bulgular: Tip 2 DM olan hastaların 80’inde (%71,42) komplikasyon mevcut iken 41’inde (%28,58) komplikasyon yoktu. Açlık plazma glukozu diyabetik komplikasyonu olan grupta diğer gruplara anlamlı olarak yüksekti (p

PROLIDASE: A Review from Discovery to its Role in Health and Disease

Prolidase (peptidase D), encoded by the PEPD gene, is a ubiquitously expressed cytosolic metalloproteinase, the only enzyme capable of cleaving imidodipeptides containing C-terminal proline or hydroxyproline. Prolidase catalyzes the rate-limiting step during collagen recycling and is essential in protein metabolism, collagen turnover, and matrix remodeling. Prolidase, therefore plays a crucial role in several physiological processes such as wound healing, inflammation, angiogenesis, cell proliferation, and carcinogenesis. Accordingly, mutations leading to loss of prolidase catalytic activity result in prolidase deficiency a rare autosomal recessive metabolic disorder characterized by defective wound healing. In addition, alterations in prolidase enzyme activity have been documented in numerous pathological conditions, making prolidase a useful biochemical marker to measure disease severity. Furthermore, recent studies underscore the importance of a non-enzymatic role of prolidase in cell regulation and infectious disease. This review aims to provide comprehensive information on prolidase, from its discovery to its role in health and disease, while addressing the current knowledge gaps.

Prolidase - A protein with many faces

Prolidase is a metal-dependent peptidase specialized in the cleavage of dipeptides containing proline or hydroxyproline on their C-termini. Prolidase homologues are found in all kingdoms of life. The importance of prolidase in human health is underlined by a rare hereditary syndrome referred to as Prolidase Deficiency. A growing number of studies highlight the importance of prolidase in various other human conditions, including cancer. Some recent studies link prolidase's activity-independent regulatory role to tumorigenesis. Furthermore, the enzyme or engineered variants have some applications in biotechnology. In this short review, we aim to highlight different aspects of the protein the importance of which is increasingly recognized over the last years.

Current Understanding of the Emerging Role of Prolidase in Cellular Metabolism

Prolidase [EC 3.4.13.9], known as PEPD, cleaves di- and tripeptides containing carboxyl-terminal proline or hydroxyproline. For decades, prolidase has been thoroughly investigated, and several mechanisms regulating its activity are known, including the activation of the β₁-integrin receptor, insulin-like growth factor 1 receptor (IGF-1) receptor, and transforming growth factor (TGF)-β₁ receptor. This process may result in increased availability of proline in the mitochondrial proline cycle, thus making proline serve as a substrate for the resynthesis of collagen, an intracellular signaling molecule. However, as a ligand, PEPD can bind directly to the epidermal growth factor receptor (EGFR, epidermal growth factor receptor 2 (HER2)) and regulate cellular metabolism. Recent reports have indicated that PEPD protects p53 from uncontrolled p53 subcellular activation and its translocation between cellular compartments. PEPD also participates in the maturation of the interferon α/β receptor by regulating its expression. In addition to the biological effects, prolidase demonstrates clinical significance reflected in the disease known as prolidase deficiency. It is also known that prolidase activity is affected in collagen metabolism disorders, metabolic, and oncological conditions. In this article, we review the latest knowledge about prolidase and highlight its biological function, and thus provide an in-depth understanding of prolidase as a dipeptidase and protein regulating the function of key biomolecules in cellular metabolism.

Serum prolidase level in patients with brucellosis and its possible relationship with pathogenesis of the disease: a prospective observational study

Background/aim

Changes in collagen metabolism and fibroblastic activity may play a role in the pathogenesis of brucellosis. The prolidase enzyme plays an important role in collagen synthesis. We aimed to investigate the association of prolidase levels with brucellosis.

Materials and methods

Serum prolidase levels in 20 patients newly diagnosed with brucellosis were compared with levels in 30 healthy control subjects. Patients with brucellosis were reassessed 3 months later for prolidase, other laboratory measurements, and response to treatment.

Results

The levels of serum prolidase were significantly higher in brucellosis patients compared with those of healthy controls. Prolidase, sedimentation, and C-reactive protein levels were significantly lower after antibrucellosis treatment than before treatment.

Conclusion

The current study is the first to demonstrate significantly increased serum prolidase levels in patients with brucellosis compared with healthy controls. Prolidase levels also significantly decreased with antibrucellosis treatment. This finding provides a new experimental basis to understand the pathogenesis of brucellosis in relation to collagen metabolism. The increase in serum prolidase levels might be related to several factors such as tissue destruction, increased fibroblastic activity, and granuloma formation, all of which are involved in the natural history of brucellosis.

The Relationship Between Prolidase Activity and Atrial Electromechanical Changes in Patients with Paroxysmal Atrial Fibrillation

Background:

Tissue fibrosis increases in the structure of the atrial tissue of atrial fibrillation patients. Prolidase enzyme regulates collagen synthesis. There may be an association between electrocardiography (ECG) findings and prolidase activity.

Objective:

This study investigated the association between atrial conduction time and prolidase activity, a collagen synthesis enzyme, and P-wave dispersion (PWD) in patients with Paroxysmal Atrial Fibrillation (PAF).

Methods:

Exclusion criteria included the age of <18 years, heart failure, diabetes, hypertension, hyperlipidemia, malignancy, cerebrovascular disease, chronic respiratory distress, osteoporosis, rheumatoid arthritis, renal disease, cirrhosis, and other types of arrhythmia. Patients diagnosed with PAF within 48 hours were considered to have a definite diagnosis. PWD was calculated using a 12-lead ECG, and inter- and intraatrial electromechanical delay (EMD) was assessed using tissue Doppler imaging and conventional echocardiography. Serum prolidase levels were measured in both groups.

Results:

A total of 43 patients with PAF (20 female, 23 male; mean age, 46.8 ± 5.7 years) and 42 healthy volunteers (21 female, 21 male; mean age, 43.9 ± 5.1 years) were included in the study.

:

Inter- and intraatrial EMD, PWD, minimum P-wave (Pmin), and maximum P-wave (Pmax) measurements were significantly higher (39.7 ± 2.7, 35.7 ± 2.3, p < 0.001; 13.2 ± 2.6, 8.5 ± 1.9, p < 0.001; 47.1 ± 11, 24.1 ± 7.1, p < 0.001; 69.8 ± 8.8, 66.7 ± 10.2, p < 0.130; 114.8 ± 13, 93.6 ± 8.6, p < 0.001, respectively) and serum prolidase levels were significantly lower in patients with PAF compared to healthy controls (3.96 ± 1.2, 8.5 ± 3.56, p < 0.001). In patients with PAF, correlation analysis showed a negative correlation between prolidase levels and intra- and interatrial EMD, PWD, and Pmax (r = -0.41, p < 0.05; r = -0.54, p < 0.05; r = -0.62, p < 0.05; r = -0.49, p < 0.05, respectively). Interatrial EMD showed a significant positive correlation with intraatrial EMD, Pmax, and PWD in patients with PAF (r = 0.90, p < 0.05; r = 0.574, p < 0.05; r = 0.43, p < 0.05, respectively). Additionally, the level of high-sensitivity C-reactive protein (hs-CRP) was significantly higher in patients with PAF (6.6 ± 8, 1.8 ± 1.6, p < 0.001).

Conclusion:

The decreased plasma prolidase activity in patients with PAF may explain the irregularity of the collagen metabolism of different extracellular components and may indicate the onset of atrial remodeling. Changes in PWD, interatrial EMD, and serum prolidase level may predict PAF before diagnosis.

Evaluation of serum prolidase enzyme activity and oxidative stress in patients with tinnitus

Introduction

Tinnitus is defined as the perception of sound in the head or in the head in the absence of external sounds. The cause of tinnitus is still unknown.

Objective

We aimed to compare the serum levels of total oxidant status, total antioxidant status, serum prolidase enzyme activity and the oxidative stress index in patients with tinnitus to those of normal subjects.

Methods

Twenty five patients with tinnitus (mean age 34.3) and 25 healthy controls (mean age 37.2) were included in the study.

Results

Total oxidant status levels in the patient group were significantly higher than in the control group (p = 0.037). The mean total oxidant status value was 2.54 ± 0.95 mmoL/L in the patient group, and 2.06 ± 0.98 mmoL/L in the control group. The mean oxidative stress index level was 0.22 ± 0.10 AU in the patient group, while it was 0.17 ± 0.08 AU in the control group. Oxidative stress index was significantly higher in the patient group (0.026). There was no significant difference between the groups in terms of total antioxidant status values (p = 0.838). The mean serum prolidase enzyme activity level was 202.74 ± 33.56 U/L in the patient group and 175.46 ± 42.68 U/L in the control group. Serum prolidase enzyme activity levels in the patient group were significantly higher than in the control group (0.040).

Conclusion

We detected that the total oxidant status, oxidative stress index and serum prolidase enzyme activity levels were higher in patients with tinnitus when compared to the healthy controls. This finding suggests that oxidative stress index and serum prolidase enzyme activity may play a role in the etiopathogenesis of tinnitus.

Evaluation of Prolidase Activity, Oxidative Stress, and Antioxidant Enzyme Levels in Testicular and Penile Tissues after Human Chorionic Gonadotropin Treatment in Rats by Predicting Infertility and Erectile Dysfunction

OBJECTIVES

Prolidase plays a vital role in collagen turnover, matrix remodeling, and cell growth. We aimed to evaluate the association between treatment with chorionic gonadotropin and infertility and erectile dysfunction by investigating tissue prolidase activity, oxidative stress, and levels of antioxidant enzymes.

MATERIALS AND METHODS

The 16 male Wistar albino rats used in this study were randomly divided into 2 groups: rats treated with human chorionic gonadotropin (hCG) and control rats (n = 8 in each group). The rats in the hCG group were subcutaneously injected with 50 IU hCG daily for 15 days, while the rats in the control group were subcutaneously injected isotonic saline. All of the rats were sacrificed by a lethal overdose of sodium pentobarbital at the first month after hCG administration. Prolidase activity and levels of malonyl aldehyde, glutathione reductase, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) were estimated in the testicular and penile tissue. The testicles and penis were transversely dissected and placed in formalin.

RESULTS

Levels of prolidase and malonyl aldehyde in the testicular and penile tissues were significantly higher in the hCG group than in the control group (p < 0.001), while levels of glutathione reductase, SOD, GSH-Px, and CAT were significantly lower in the hCG group than in the control group (p < 0.001).

CONCLUSIONS

In this study, we observed that treatment with hCG increased prolidase activity and oxidative stress and decreased the antioxidant capacity of penile and testicular tissues; therefore, this may affect fertility and erectile function.

Serum prolidase enzyme activity in obese subjects and its relationship with oxidative stress markers

BACKGROUND

The relationship between increased serum enzyme activity of prolidase and increased rate of collagen turnover in the arterial wall has been asserted in previous studies. Collagen reflects much of the strength to the connective tissue involved in the arterial wall. Atherosclerosis is very common vessel disease and oxidative stress plays a pivotal role in the etiopathogenesis. Our objective was to examine the serum enzyme activity of prolidase and its possible relationships with oxidative stress parameters in obese subjects.

METHODS

Our present study was conducted 27 obese subjects and 26 age-matched healthy control subjects. The serum enzyme activity of prolidase in all study population was evaluated spectrophotometrically. Oxidative stress levels in obese subjects were analyzed with total antioxidant capacity (TAC) and total oxidant status (TOS) as well as oxidative stress index (OSI).

RESULTS

Obese subjects have higher serum TOS and OSI indicators as well as prolidase activity than those in control subjects (for all; p<0.001). Moreover, obese subjects have lower levels of TAC than in those in healthy subjects (p<0.001). In the Pearson's correlation analysis, enzyme activity of prolidase was positively related with TOS (p<0.001, r=0.529) and OSI (p<0.001, r=0.519) as well as BMI (p<0.001, r=0.692) and inversely related with TAC (p<0.05, r=-0.405) in obese subjects.

CONCLUSIONS

Increased serum prolidase activity and decreased antioxidant levels are likely to be a results of increased of oxidative stress levels in obese subjects. The significantly correlation between increased oxidative stress and increased prolidase activity may play a pivotal role in etiopathogenesis of atherosclerotic cardiovascular diseases in obese subjects.

Circulating Prolidase Activity in Patients with Myocardial Infarction

Background

Collagen is a major determinant of atherosclerotic plaque stability. Thus, identification of differences in enzymes that regulate collagen integrity could be useful for predicting susceptibility to atherothrombosis or for diagnosing plaque rupture. In this study, we sought to determine whether prolidase, the rate-limiting enzyme of collagen turnover, differs in human subjects with acute myocardial infarction (MI) versus those with stable coronary artery disease (CAD).

Methods

We measured serum prolidase activity in 15 patients with stable CAD and 49 patients with acute MI, of which a subset had clearly defined thrombotic MI (n = 22) or non-thrombotic MI (n = 12). Prolidase activity was compared across study time points (at cardiac catheterization, T0; 6 h after presentation, T6; and at a quiescent follow-up, Tf/u) in acute MI and stable CAD subjects. We performed subgroup analyses to evaluate prolidase activity in subjects presenting with acute thrombotic versus non-thrombotic MI.

Results

Although prolidase activity was lower at T0 and T6 versus the quiescent phase in acute MI and stable CAD subjects (p < 0.0001), it was not significantly different between acute MI and stable CAD subjects at any time point (T0, T6, and Tf/u) or between thrombotic and non-thrombotic MI groups. Preliminary data from stratified analyses of a small number of diabetic subjects (n = 8) suggested lower prolidase activity in diabetic acute MI subjects compared with non-diabetic acute MI subjects (p = 0.02).

Conclusion

Circulating prolidase is not significantly different between patients with acute MI and stable CAD or between patients with thrombotic and non-thrombotic MI. Further studies are required to determine if diabetes significantly affects prolidase activity and how this might relate to the risk of MI.

Up-Regulation of RANK Expression via ERK1/2 by Insulin Contributes to the Enhancement of Osteoclast Differentiation

Despite the importance of the receptor activator of nuclear factor (NF)-kappaB ligand (RANKL)-RANK signaling mechanisms on osteoclast differentiation, little has been studied on how RANK expression is regulated or what regulates its expression during osteoclastogenesis. We show here that insulin signaling increases RANK expression, thus enhancing osteoclast differentiation by RANKL. Insulin stimulation induced RANK gene expression in time- and dose-dependent manners and insulin receptor shRNA completely abolished RANK expression induced by insulin in bone marrow-derived monocyte/macrophage cells (BMMs). Moreover, the addition of insulin in the presence of RANKL promoted RANK expression. The ability of insulin to regulate RANK expression depends on extracellular signal-regulated kinase 1/2 (ERK1/2) since only PD98059, an ERK1/2 inhibitor, specifically inhibited its expression by insulin. However, the RANK expression by RANKL was blocked by all three mitogen-activated protein (MAP) kinases inhibitors. The activation of RANK increased differentiation of BMMs into tartrate-resistant acid phosphatase-positive (TRAP+) osteoclasts as well as the expression of dendritic cell-specific transmembrane protein (DC-STAMP) and d2 isoform of vacuolar (H+) ATPase (v-ATPase) Vo domain (Atp6v0d2), genes critical for osteoclastic cell-cell fusion. Collectively, these results suggest that insulin induces RANK expression via ERK1/2, which contributes to the enhancement of osteoclast differentiation.

Serum Prolidase Activity as a Biomarker for Choroid Plexus Calcification

The choroid plexus (CP) performs multiple functions such as secretion and reabsorption. CP also acts as the blood-cerebrospinal fluid barrier. Prolidase plays an important role in collagen metabolism by degrading imidodipeptides, in which proline or hydroxyproline residue is located at the C-terminal end. Serum prolidase activity (SPA) may reflect the degree of fibrosis and inflammation. Choroid plexus calcification (CPC) is considered as the physiological calcification of the brain, and CPC is diagnosed by the presence of calcification in the anatomical region on computed tomography (CT). Here, CPC and non-calcified CP were defined by Hounsfield Units (HU) values of > 150 and < 50, respectively. We aimed to measure SPA in subjects with CPC and those with non-calcified CP. This study included 89 subjects who were admitted to the neurology clinic and underwent CT: 44 subjects with CPC and 45 subjects with non-calcified CP. The neurological examination of all subjects was normal; namely, the subjects with CPC were asymptomatic. The SPA level was significantly higher in the CPC group than that in the non-calcified CP group (p < 0.002), and there was a significant positive correlation between vitamin D and SPA levels in the CPC group. In contrast, the vitamin D and parathyroid hormone levels were higher in the CPC group, but the difference was not statically significant (p > 0.05). These findings indicate that SPA is a biomarker for CPC that may be predictive of future brain disease.

The relationships among the levels of oxidative and antioxidative parameters, FEV1 and prolidase activity in COPD

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by poorly reversible airflow limitations associated with an abnormal inflammatory response of the lung.

METHODS

We investigated whether prolidase levels in serum, total antioxidant status, total oxidative status (TOS), and the oxidative stress index (OSI) were associated with the etiopathogenesis of COPD, and whether there is a relationship between prolidase activity and oxidative parameters and carotid artery intima-media thickness (CIMT) in patients with COPD. This study included 91 patients with COPD and 15 control cases. Routine haematological and biochemical parameters were determined in all patients. All subjects were fully informed about the study and provided consent.

RESULTS

The mean age of the patients with COPD was 61.3 ± 10.5 years and that of the control group was 56.2 ± 12.1 years. The control group had a significantly higher plasma prolidase level than that in the COPD group. TOS and OSI levels in the control group were significantly lower than those in the COPD group. However, no significant differences were found in TALs or CIMT levels between the COPD and control groups. A negative correlation was detected between prolidase activity and age; however, no significant difference in age was observed between the two groups.

CONCLUSION

These results indicate that prolidase activity decreases in patients with COPD.

The Value of Serum Prolidase Activity in Progression of Microalbuminuria in Patients With Type 2 Diabetes Mellitus

BACKGROUND

Prolidase is a cytosolic exopeptidase that plays a pivotal role in collagen turnover. Diabetic nephropathy (DN) is associated with structural changes in glomerular basement membrane accompanied with increased amounts of collagen. Prolidase is known to be abundant in kidney and collagen accumulation is increased in DN, so we aimed to determine the value of serum prolidase activity (SPA) in predicting the progression of nephropathy in type 2 diabetes mellitus (DM).

METHODS

Thirty type 2 DM patients having microalbuminuria (microalbuminuric group), 30 type 2 DM patients without albuminuria (normoalbuminuric group), and 28 healthy controls (control group) were enrolled. Study groups had similar age, sex distribution, and body mass index (BMI).

RESULTS

Metabolic parameters, SPA and urinary microalbumin were determined. SPA was significantly higher in microalbuminuric group when compared with normoalbuminuric and control groups (P = 0.05 and P < 0.001, respectively). Triglyceride levels were significantly higher and high density lipoprotein cholesterol (HDL-C) levels were significantly lower in microalbuminuric group compared to control group (Both P < 0.05). SPA showed a negative correlation with HDL-C level and a positive correlation with urinary albumin excretion (r = -0.219, P < 0.05 and r = 0.39, P < 0.001 respectively). In regression analysis, albumin excretion was the sole parameter influencing SPA.

CONCLUSION

SPA appears to be higher in type 2 DM patients having microalbuminuria compared to patients without microalbuminuria and healthy controls. The pathophysiological role and the significance of SPA in predicting DN need to be further evaluated.

Evaluation of serum prolidase activity in patients with slow coronary flow

INTRODUCTION

Slow coronary flow (SCF) is described as the slow passage of contrast to distal coronaries despite anatomically normal coronary arteries. It has been shown that increased serum prolidase activity (SPA) correlates with collagen turnover. Increased collagen turnover might be associated with the development of atherosclerotic plaques.

AIM

To investigate the relationship between serum prolidase activity and slow coronary flow.

MATERIAL AND METHODS

This cross-sectional study included 40 SCF patients (mean age: 55.0 ±9.5 years, 20 females) and 40 controls (mean age: 53.9 ±8.2 years, 21 females) with normal coronary anatomy and normal coronary flow. The Thrombolysis in Myocardial Infarction (TIMI) frame-count (TFC) method was used for SCF diagnosis. Serum prolidase activity was measured spectrophotometrically, and the relevant parameters were compared between the groups.

RESULTS

There were no statistically significant differences between the SCF and control groups in terms of basic demographic, clinical, and laboratory data. However, the SPA was significantly higher in the SCF group compared to the control (702.7 ±13.8 and 683.9 ±13.2 respectively, p<0.001). Serum prolidase activity was significantly correlated with the mean TFC (r=0.463, p<0.001). The overall findings of this study support the predictive accuracy of the serum prolidase activity in our cohort, with a statistically significant ROC value of 681.3.

CONCLUSIONS

Our study showed that SPA was increased in SCF patients. The activity of this enzyme was significantly correlated with the mean TFC.

Potential impact of sitagliptin on collagen-derived dipeptides in diabetic osteoporosis

It is known that diabetes coincides with an increased risk of osteoporosis. While a disturbed collagen metabolism is proposed as a possible cause, much remains unknown about the enzymes involved and changes in the collagen-derived dipeptides and amino acids. Therefore, we sought to study this intricate pathway and the effect of dipeptidyl peptidase 4 (DPP4) inhibitors. Control and streptozotocin-nicotinamide-induced diabetic rats were treated for 12 weeks with vehicle or sitagliptin, a DPP4 inhibitor (Con/VH, Con/SG, DM/VH and DM/SG). The activities of four key enzymes involved in collagen breakdown were determined in serum (DPP4, matrix metalloproteinase 2 and 9 and prolidase). Dipeptide (Ala-Pro, Gly-Pro, Pro-Pro and Pro-Hyp) and amino acid (Pro and Hyp) concentrations were measured by liquid chromatography coupled to mass spectrometry. We found three-fold higher MMP9 activities in DM/VH than in controls, while in DM/SG this rise was attenuated. MMP2 and prolidase did not differ in the investigated groups. Furthermore, we are the first to report on two-fold higher Ala-Pro and Pro-Pro levels in diabetes compared to controls. In contrast, Pro-Hyp concentrations were lower in diabetes (DM/VH and DM/SG). DPP4 inhibition does not seem to have a direct influence on the collagen metabolism in streptozotocin-nicotinamide-induced diabetic rats. Instead, it probably acts through its effect on osteoprotective substrates. In diabetes, increased MMP9 activities seem to favour the production of Ala-Pro and Pro-Pro containing collagen fragments. The high Pro-Hyp levels in untreated controls might have a bone-stimulating effect. Nevertheless, the biological significance of these dipeptides is not yet clear and should be further investigated.

Plasma Prolidase Activity and Oxidative Stress in Patients with Parkinson's Disease

Prolidase deficiency has been related to mental retardation and oxidative stress. The study aimed to observe plasma prolidase activity (PPA), total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) in patients with Parkinson's disease (PD). 240 subjects with PD and 150 healthy volunteers were considered as cases and controls, respectively. PPA, TOS, TAS, and OSI were measured spectrophotometrically. PPA and TAS in cases were more significantly decreased than controls (P < 0.01), while TOS and OSI were significantly increased (P < 0.001). In cases, nonsignificant, positive correlation was observed between PPA and TOS and OSI while significant, negative correlation was observed between PPA and TAS (P = 0.047). PPA in cases was nonsignificantly decreased with increased duration of PD (P = 0.747) while TAS was significantly decreased (P < 0.001) and TOS and OSI were significantly increased (P < 0.001). It was observed that higher age groups had decreased PPA, and TAS and increased TOS and OSI compared to lower age groups in cases. In summary, patients with PD have decreased PPA and increased oxidative stress compared to healthy volunteers. PPA was associated with oxidative stress markers in patients with PD. Decreased PPA and TAS and increased TOS and OSI were associated with progression of disease and higher age.

Proteomic identification of hair cell repair proteins in the model sea anemone Nematostella vectensis

Sea anemones have an extraordinary capability to repair damaged hair bundles, even after severe trauma. A group of secreted proteins, named repair proteins (RPs), found in mucus covering sea anemones significantly assists the repair of damaged hair bundle mechanoreceptors both in the sea anemone Haliplanella luciae and the blind cavefish Astyanax hubbsi. The polypeptide constituents of RPs must be identified in order to gain insight into the molecular mechanisms by which repair of hair bundles is accomplished. In this study, several polypeptides of RPs were isolated from mucus using blue native PAGE and then sequenced using LC-MS/MS. Thirty-seven known polypeptides were identified, including Hsp70s, as well as many polypeptide subunits of the 20S proteasome. Other identified polypeptides included those involved in cellular stress responses, protein folding, and protein degradation. Specific inhibitors of Hsp70s and the 20S proteasome were employed in experiments to test their involvement in hair bundle repair. The results of those experiments suggested that repair requires biologically active Hsp70s and 20S proteasomes. A model is proposed that considers the function of extracellular Hsp70s and 20S proteasomes in the repair of damaged hair cells.

Serum prolidase activity and oxidative stress in diabetic nephropathy and end stage renal disease: a correlative study with glucose and creatinine

Association of oxidative stress and serum prolidase activity (SPA) has been reported in many chronic diseases. The study was aimed at evaluating the correlation of glucose and creatinine to SPA and oxidative stress in patients with diabetic nephropathy (DN) and end stage renal disease (ESRD) concerned with T2DM. 50 healthy volunteers, 50 patients with T2DM, 86 patients with DN, and 43 patients with ESRD were considered as control-1, control-2, case-1, and case-2, respectively. Blood glucose, creatinine, SPA, total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) were measured by colorimetric tests. SPA, TOS, and OSI were significantly increased in case-1 and case-2 than control-1 and control-2, while TAS was significantly decreased (P < 0.001). Blood glucose was linearly correlated to SPA, TOS, TAS, and OSI in control-2, case-1 and case-2 (P < 0.001). Serum creatinine was linearly correlated with SPA, TOS, TAS and OSI in control-2 and case-1 (P < 0.001). In case-2, serum creatinine was significantly correlated with SPA only (P < 0.001). Thus, the study concluded that SPA and oxidative stress significantly correlated with blood glucose and creatinine. SPA, TOS, TAS, and OSI can be used as biomarkers for diagnosis of kidney damage.

Serum prolidase enzyme activity and oxidative stress levels in patients with diabetic neuropathy

Previous studies have suggested that prolidase and nitric oxide (NO) regulate many processes, such as collagen synthesis and matrix remodeling. Oxidative stress plays an important role in the development of microvascular complications in diabetic patients. Data on serum prolidase activity in patients with diabetes mellitus or diabetic neuropathy (DN) are limited and conflicting. The aim of this study was to measure serum prolidase activity, NO, total antioxidant status (TAS), and malondialdehyde (MDA) levels in patients with DN. Forty-five patients with DN and 40 healthy controls were enrolled. Serum prolidase activity, TAS, MDA, and NO levels were determined. Serum MDA and NO levels were significantly higher in DN patients than controls (p = 0.002, p = 0.001, respectively), while prolidase activity and TAS levels were lower (p = 0.003, p = 0.001, respectively). Prolidase activity was negatively correlated with NO and MDA (r = -0.911, p < 0.001; r = -0.905, p < 0.001, respectively), while positively correlated with TAS (r = 0.981, p < 0.001) in DN patients. The current study is the first showing the decreased serum prolidase enzyme activity. Our results suggest that decreased collagen turnover may occur in DN patients, who have increased oxidative stress and increased NO levels. Decreased prolidase activity seems to be associated with increased NO levels and oxidative stress along with decreased antioxidant levels in DN. Therefore, decreased prolidase activity may play a role in pathogenesis of DN. Prospective clinical studies are necessary to confirm these findings.

Evaluation of the utility of serum prolidase as a marker for liver fibrosis

BACKGROUND

Liver dysfunction is common and often unrecognized. Liver biopsy is the gold standard in the assessment of liver fibrosis, but has disadvantages. We assessed the diagnostic accuracy of serum prolidase enzyme activity (SPA) in predicting the presence and degree of liver fibrosis, as compared with liver biopsy. Further, we evaluated the effect of hemolysis on measured SPA levels.

METHODS

We undertook a prospective case control study. Thirty eight outpatients without apparent liver illness and 20 patients with liver pathology scheduled to undergo liver biopsy had their SPA levels measured.

RESULTS

Patients undergoing liver biopsy had higher SPA levels (361 (268) IU/l [median (interquartile range)]) compared with controls (169 (160) (P < 0.001)). A SPA cutoff value of 200 IU/l yielded a sensitivity of 89%, specificity of 59%, an odds ratio of 11.5, negative predictive value of 92%, and a positive predictive value of 50%. Hemolysis causes an apparent increase in SPA levels.

CONCLUSION

Higher SPA levels in patients undergoing liver biopsies compared with controls may reflect the presence of liver fibrosis. SPA levels could not be used to stage the degree of fibrosis. SPA measurement may be useful in the diagnostic workup of suspected liver disease.

Serum prolidase enzyme activity and oxidative stress levels in patients with acute hemorrhagic stroke

BACKGROUND

It has been indicated that oxidative damage contributes to secondary brain injury in both ischemic and hemorrhagic stroke patients. Collagen is a major component of the extracellular matrix, and prolidase plays a role in collagen synthesis. The aim of this study was to evaluate the serum prolidase activity, nitric oxide (NO) levels, total antioxidant capacity (TAC) and total oxidant status (TOS) in patients with acute hemorrhagic stroke.

METHODS

Twenty-five patients with acute hemorrhagic stroke and 25 controls were enrolled. Serum prolidase activity, catalase activity, NO levels, TAC and TOS were measured spectrophotometrically. Oxidative stress index (OSI) was calculated.

RESULTS

Serum TAC levels and catalase activity were significantly lower in acute hemorrhagic stroke patients than controls (both, p < 0.001), while NO levels, TOS levels, OSI values and prolidase activity were significantly higher (all, p < 0.01). When patients with acute hemorrhagic stroke were divided according to gender, no differences were observed between females and males in respect to serum prolidase enzyme activity, NO levels, TAC levels, TOS levels and OSI values (all, p > 0.05).

CONCLUSIONS

Findings from the study suggest an association between increased oxidative stress levels, decreased antioxidant levels and increased prolidase enzyme activity in patients with acute hemorrhagic stroke compared with controls. More studies are needed to elucidate mechanistic pathways on oxidative stress in patients with acute hemorrhagic stroke.

Serum prolidase activity is associated with non-diabetic metabolic syndrome

OBJECTIVE

The aim of this study was to determine the role of serum prolidase activity and the possible association with oxidative stress parameters in non-diabetic metabolic syndrome.

METHODS

30 obese patients without metabolic syndrome (MetS), 34 non-diabetic obese patients with MetS, and 23 volunteer control subjects were enrolled in the study. Fasting plasma glucose (FPG), plasma glucose following 75 g glucose administration, high-density lipoprotein- cholesterol (HDL-C), high-density lipoprotein- cholesterol (LDL-C), total cholesterol, triglyceride (TG), total antioxidant status (TAS), total oxidative status (TOS), oxidative stress index (OSI), and prolidase activities of all subjects were analyzed.

RESULTS

Prolidase levels was significantly higher in MetS group compared to both obese and control groups (p < 0.001 and p < 0.05 respectively). Prolidase was also higher in the obese group than in the control group (p < 0.05). Prolidase was negatively correlated with TAS and HDL-C (r = -0,362, p < 0.001; r = -0.320, p < 0.01, respectively) and positively correlated with BMI, weight, waist-c, SBP, DBP, TG, TC, LDL-C.

CONCLUSION

Prolidase activity may have a role in the pathogenesis of metabolic syndrome.

Serum prolidase activity, oxidant and antioxidant status in nonulcer dyspepsia and healthy volunteers

Helicobacter pylori (H. pylori) infection is associated with increased oxidative stress and serum prolidase activity (SPA) in many diseases. We aimed to observe SPA and oxidative stress in nonulcer dyspepsia (NUD) infected with and without H. pylori among eastern Indians. 106 patients with H. pylori positive NUD, 82 patients with H. pylori negative NUD, and 50 healthy individuals were selected. SPA, total antioxidant capacity (TAOC), and total oxidant status (TOS) were measured with the use of spectrophotometer and an automated measurement method. SPA, TOS, and oxidative stress index (OSI) were significantly higher in patients with H. pylori positive than H. pylori negative NUD and healthy individuals (all P < 0.0001), whereas TAOC was significantly lower (P < 0.0001). Nonsignificant, increased SPA (P value = 0.6083) and decreased TAOC (P value = 0.1186) were observed in patients with H. pylori negative NUD than healthy individuals, while increased TOS and OSI were significant (P < 0.0001). Weak, nonsignificant correlations were observed between serum prolidase activity and TAOC, TOS, and OSI in H. pylori positive cases. Thus, increased SPA along with increased oxidative stress was observed, which seem to be closely associated with H. pylori infection. SPA and oxidative stress seem to be used as biomarkers for H. pylori infection in NUD.

Serum prolidase activity in ankylosing spondylitis and rheumatoid arthritis

The aim of the present study was to emphasize the collagen turnover in 2 of the most common chronic inflammatory rheumatic diseases by evaluating serum prolidase activity (SPA) in ankylosing spondylitis (AS) and rheumatoid arthritis (RA). 30 patients who met the modified New York Criteria for the classification of AS, 29 patients who met the 2010 Rheumatoid Arthritis Classification Criteria for the classification of RA, and 31 healthy controls were enrolled in the study. Serum samples of the patients and the controls were collected and SPA was measured by a spectrophotometric method. The comparison of the SPA in these 3 groups was statistically examined. In both patient groups, the SPA was lower than in the control group. SPA in patients with AS was statistically significantly lower than in the control and RA groups (P < 0.001/P = 0.002). No statistically significant difference was found between the RA and the control groups (P = 0.891). In conclusion, lower SPA is presumably associated with decreased collagen turnover and fibrosis, leading to decreased physical functions in both chronic inflammatory musculoskeletal diseases.

Serum prolidase activity in diabetic foot ulcers

Impaired wound healing is an important problem in diabetes mellitus; however, its pathogenesis remains unclear. We aimed to evaluate serum prolidase activity (SPA), an important marker of collagen turnover, in subjects with and without diabetic foot ulcers as compared with healthy controls. Twenty-seven patients with diabetic foot ulcers (foot ulcer group), 27 patients without diabetic foot ulcers (diabetic control group) and 27 healthy controls were enrolled. The study groups had similar age, sex distribution and body mass index. Metabolic and inflammatory parameters as well as SPA were determined. The diabetic foot ulcer group had significantly higher SPA (both p < 0.001) when compared with the diabetic and the healthy control groups. SPA showed a positive correlation with high-sensitive C-reactive protein and a negative correlation with high-density lipoprotein cholesterol levels (r = 0.313, p = 0.021 and r = -0.233, p = 0.036, respectively). No correlation was detected between SPA and glycaemic parameters. SPA appears to be higher in patients with diabetic foot ulcers when compared with patients without diabetic foot ulcers and healthy controls. The underlying mechanisms of elevated SPA and its clinical significance in predicting the natural course of wound healing in diabetic foot ulcers needs to be further evaluation.

Molecular mechanisms involved in the bidirectional relationship between diabetes mellitus and periodontal disease

Both diabetes and periodontitis are chronic diseases. Diabetes has many adverse effects on the periodontium, and conversely periodontitis may have deleterious effects further aggravating the condition in diabetics. The potential common pathophysiologic pathways include those associated with inflammation, altered host responses, altered tissue homeostasis, and insulin resistance. This review examines the relationship that exists between periodontal diseases and diabetes mellitus with a focus on potential common pathophysiologic mechanisms.

Serum prolidase activity in psoriasis patients

This study aimed to evaluate serum prolidase activity and the effects of gender, body mass index (BMI), disease severity and duration, and therapy type on prolidase activity in patients with psoriatic as well as the relationship between serum NO· and prolidase levels in these patients. The study included 29 clinically documented plaque patients with psoriasis and 24 healthy volunteers. Data such as age, sex, BMI, duration and severity of disease, and type of therapy were assessed. NO· levels were determined by the Griess reaction. Serum prolidase assay is based on a colorimetric determination of proline by Chinard's reagent. We did not determine any difference in serum NO· levels of psoriatic patients when compared to controls. Serum prolidase levels in psoriasis patients were significantly higher than those in controls. There was no significant difference in prolidase activity between male and female. No statistically significant correlations were found between serum prolidase levels and BMI, PASI and disease duration. When compared between topical treatment group and systemic treatment group, there was no significant difference in serum prolidase activity. In conclusion, patients with psoriasis exhibit higher serum prolidase activity independent of gender, BMI, disease severity or duration, type of treatments or NO· level. However, further studies are needed to verify these findings as well as altered collagen synthesis in patients with psoriasis.

Serum prolidase activity in patients with pulmonary tuberculosis

AIM

To investigate serum prolidase activity (SPA) in patients with pulmonary tuberculosis (PTB).

MATERIAL AND METHODS

Twenty-nine PTB patients and 32 controls were included in the study. PTB patients (cavitary and non-cavitary) and controls were compared in terms of mean SPA. Correlations were evaluated between SPA and acute phase reactants.

RESULTS

Mean SPA was significantly higher in PTB patients than in the control group. Mean SPA was significantly higher in patients with cavitary TB than non-cavitary TB. Mean SPA in patients with mild PTB was lower than patients with moderate and severe disease. We found significant correlations between SPA and CRP, ESR, albumin, platelet counts, HDL-cholesterol and LDH activity.

CONCLUSION

This study has shown that PTB patients have higher SPA than controls. The increase in SPA might be related to tissue destruction, increased immunoglobulin, complement levels and increased fibroblastic activity; all of which are involved in the natural history of PTB.

Serum prolidase activity and oxidative-antioxidative status in Legg-Calve-Perthes disease

We aimed to find out that whether collagen turnover is altered in the context of Legg-Calve-Perthes disease (LCPD) by evaluating serum prolidase activity. We also investigated the correlation between collagen turnover and oxidative-antioxidative status in LCPD. Plasma prolidase activity, total oxidant status (TOS), total antioxidant capacity, and oxidative stress index (OSI) were determined for 39 patients with LCPD and 40 healthy controls. Serum prolidase activity, TOS, and OSI were higher, but TAC was lower in patients with LCPD compared with controls. Prolidase activity was positively correlated with TOS and OSI levels. Serum prolidase activity is significantly associated with LCPD.

Prolidase activity dysregulation and its correlation with oxidative-antioxidative status in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a consequence of an underlying chronic inflammatory disorder of the airways that is usually progressive and causes dysregulation in the metabolism of collagen. Prolidase has an important role in the recycling of proline for collagen synthesis and cell growth.

OBJECTIVE

We measured and compared prolidase activity in healthy individuals with COPD patients to find out that whether its activity might reflect disturbances of collagen metabolism in the patients. We also investigated oxidative-antioxidative status and its relationship with prolidase activity in this disease.

METHODS

Thirty voluntary patients with COPD and 30 healthy control subjects with similar age range and sex were included into the study. Plasma prolidase activities, total antioxidant capacity (TAC) and lipid peroxidation (LPO) levels were measured in the patient and control groups.

RESULTS

Plasma prolidase activity and TAC levels were significantly lower, and LPO levels were significantly higher in the patients than those in the control subjects (P<0.05, P<0.001, and P<0.001, respectively). Significant correlations were detected between plasma prolidase activity and TAC and LPO levels in the patients group (r=0.679, P<0.001; r=-426, P<0.05, respectively).

CONCLUSIONS

The results suggest that oxidative-antioxidative balance and collagen turnover are altered by the development of COPD in human lungs, and prolidase activity may reflect disturbances of collagen metabolism in this pulmonary disease. Monitoring of plasma prolidase activity and oxidative-antioxidative balance may be useful in evaluating fibrotic processes and oxidative damage in the chronic inflammatory lung disease in human.

Periodontitis and risk of diabetes mellitus

Diabetes mellitus (DM) is a complex disease with varying degrees of systemic and oral complications. The periodontium is also a target for diabetic damage. Diabetes is a pandemic in both developed and developing countries. In recent years, a link between periodontitis and diabetes mellitus has been postulated. The oral cavity serves as a continuous source of infectious agents that could further worsen the diabetic status of the patient and serve as an important risk factor deterioration of diabetes mellitus. The present review highlights the relationship between diabetes mellitus and periodontitis. The potential mechanisms involved in the deterioration of diabetic status and periodontal disease are also discussed.

Prolidase activity and oxidative status in patients with thalassemia major

AIM

Prolidase is a specific imidodipeptidase involved in collagen degradation. The increase in the enzyme activity is believed to be correlated with the increased intensity of collagen degradation. The study aimed to evaluate the relationship between prolidase activity and oxidative status in patients with thalassemia major.

METHODS

Comparison was made between 87 patients diagnosed with thalassemia major and 33 healthy children of similar age and gender. Mean age of the subjects was 7.5+/-4.3 years in the group of patients with thalassemia major and 8.9+/-3.1 years in the control group. Serum prolidase activity was measured spectrophotometrically. Oxidative status was determined using total oxidant status (TOS), total antioxidant capacity (TAC), and oxidative stress index (OSI) measurement.

RESULTS

Prolidase activity was significantly increased in patients with thalassemia major (53.7+/-8.7 U/l) compared to the control group (49.2+/-7.2 U/l, P<0.001). TOS was significantly increased in the patient group (5.31+/-3.14 mmol H2O2 equiv./l) compared to the control group (3.49+/-2.98 mumol H2O2 equiv./l) and the OSI was also significantly increased in the patient group (3.86+/-3.28 arbitrary unit) compared to the control group (2.53+/-2.70 arbitrary unit) (P<0.0001 and P<0.001, respectively), while there were no significant differences between the patient (1.61+/-0.30 mumol Trolox equiv./l) and control (1.64+/-0.33 mumol Trolox equiv./l) groups with respect to TAC.

CONCLUSION

Significant increases in prolidase activity in patients with thalassemia major may constitute a key parameter in demonstrating a disorder of the collagen metabolism.

The Role of Prolidase Activity in the Diagnosis of Uremic Bone Disease

The derangements in bone metabolism in patients with chronic renal failure (CRF) are summarized as uremic bone disease (UBD). In this study, we planned to determine the serum prolidase to compare it with the other biochemical markers. This study was performed on 44 patients (19 females, 25 males, mean age = 56.8 +/- 15.6 years) with endstage renal disease (ESRD). The patients were divided into three groups according to serum bone alkaline phosphatase (bAP) levels. The patients whose bAP was > or =77 U/L were accepted as having high-turnover UBD (n=18), the patients whose bAP was < or =50 U/L were accepted as having low-turnover UBD (n=14), and the patients whose bAP levels were between these two values were accepted as having bone disease with normal turnover (n=12). The serum prolidase levels did not increase in patients with ESRD. There were no significant differences between the serum prolidase levels of patients according to types of the UBD (p > 0.05). Kidney is the most prolidase-rich tissue of the human body. The serum prolidase activity is low in all patients with ESRD, irrespective of the type of UBD. Therefore, we concluded that prolidase had no value in the diagnosis of UBD.

The association of serum prolidase activity with the presence and severity of coronary artery disease

OBJECTIVES

Prolidase is a cytosolic exopeptidase that cleaves iminodipeptides with carboxy-terminal proline or hydroxyproline and plays major role in collagen turnover. Collagen is the essential content in atherosclerotic plaque playing a key role in the stability/instability of and progression of coronary artery disease (CAD). Consequently, in this study we sought to determine serum prolidase activity and markers of oxidative stress such as lipid hydroperoxide and total free sulfhydryl in CAD.

DESIGN AND METHODS

We have evaluated 199 patients with CAD and 122 control cases with clinical, electrocardiographic, and laboratory investigation. We have measured serum prolidase activity and serum total free sulfhydryl levels spectrophotometrically. Serum lipid hydroperoxide levels were determined with ferrous ion oxidation-xylenol orange method. We assessed the association of serum prolidase activity with the presence and severity of CAD and clinical characteristics, and laboratory parameters.

RESULTS

Serum prolidase activity (52.5+/-5.6 vs. 46.7+/-5.1 U/l, respectively, P<0.001) and serum lipid hydroperoxide levels were significantly increased in patients with CAD compared with control cases whereas, serum total free sulfhydryl levels were significantly decreased in patients with CAD compared with control cases. Serum prolidase activity and total free sulfhydryl levels were independent predictors of the presence of CAD [(chi=75.532, ss=0.212, P=0.003) and (chi=25.969, ss=-30.486, P=0.019), respectively] and Gensini score [(beta=0.276, P<0.001) and (beta=-0.274, P<0.001), respectively]. Independent predictors of serum prolidase activity were serum high-density lipoprotein cholesterol (beta=-0.138, P=0.023) and urea levels (beta=0.146, P=0.036), and Gensini score (beta=0.317, P<0.001).

CONCLUSION

Findings of this study have shown that serum prolidase activity is significantly associated with the presence and severity of CAD, and elevated serum prolidase activity might be an independent predictor of coronary atherosclerosis.

Association of prolidase activity, oxidative parameters, and presence of atrial fibrillation in patients with mitral stenosis

BACKGROUND

Mitral stenosis (MS) is a common cause of atrial fibrillation (AF). Oxidative stress and inflammation factors were shown to be involved in atrial remodeling. The study aim was to compare the oxidative parameters and prolidase activity in severe MS patients with and without AF.

METHODS

The study population was comprised of 33 patients with MS and sinus rhythm (group I), 27 patients with MS and AF (group II), and 25 healthy controls (group III). Plasma prolidase activity, total antioxidant capacity (TAC), total oxidative status (TOS), and oxidative stress index (OSI) were determined. Additionally, we measured tissue TOS and TAC in patients with mitral valve replacement.

RESULTS

TAC and OSI were higher, but TOS and prolidase were lower in patients with MS than control (all p <0.001). These parameters were similar in group I and group II (ANOVA p >0.05). Tissue TAC was significantly lower in group II than group I (0.015 +/- 0.01 vs. 0.026 +/- 0.01 mmol Trolox equiv/L, p = 0.014), tissue TOS was similar between groups I and II (0.24 +/- 0.06 vs. 0.22 +/- 0.05 mmol Trolox equiv/L, p = 0.161). Presence of AF was correlated with systolic blood pressure, left atrial diameter, plasma TAC, tissue TAC, plasma TOS, plasma OSI, and plasma prolidase activity. Tissue TAC level (beta = -0.435, p = 0.006) and left atrial diameter (beta = 0.460, p = 0.003) were independently related with presence of AF in patients with MS.

CONCLUSIONS

This study suggested that the presence of AF in patients with severe MS may be associated with the plasma prolidase activity, tissue and plasma oxidative parameters.

Serum prolidase activity in patients with hypertension and its relation with left ventricular hypertrophy

OBJECTIVES

The purpose of this study was to determine serum prolidase activity in patients with hypertension and its relation with left ventricular hypertrophy.

DESIGN AND METHODS

Serum prolidase activity was measured spectrophotometrically in hypertensive patients with (Group II, n=30) and without left ventricular hypertrophy (Group III, n=30) and in control group (Group I, n=30).

RESULTS

Prolidase activity was significantly lower in Group I than in Groups II and III (44.64+/-6.42 U/L vs. 54.14+/-6.30 U/L and 54.25+/-7.14 U/L, respectively; ANOVA, p<0.001). We revealed significant correlation between prolidase activity and presence and duration of hypertension (both of p<0.05) but not left ventricular mass index. Multivariate analysis shown that prolidase activity was significantly associated with age (beta=0.481, p<0.001) and duration of hypertension (beta=0.396, p<0.001).

CONCLUSIONS

Our data show that serum prolidase activity is associated with the presence hypertension independent of left ventricular hypertrophy.

Characterization of prolidase activity using capillary electrophoresis with tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection and application to evaluate collagen degradation in diabetes mellitus

A new method for prolidase (PLD, EC 3.4.13.9) activity assay was developed based on the determination of proline produced from enzymatic reaction through capillary electrophoresis (CE) with tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)3(2+)] electrochemiluminescence detection (ECL). A detection limit of 12.2 fmol (S/N = 3) for proline, corresponding to 1.22 x 10(-8) units of prolidase catalyzing for 1 min was achieved. PLD activity determined by CE-ECL method was in agreement with that obtained from the classical Chinard's one. CE-ECL showed its powerful resolving ability and selectivity as no sample pretreatment was needed and no interference existed. The clinical utility of this method was successfully demonstrated by its application to assay PLD activity in the serum of diabetic patients in order to evaluate collagen degradation in diabetes mellitus (DM). The results indicated that enhanced collagen degradation occurred in DM.

Diabetes mellitus and periodontal diseases

BACKGROUND

The purpose of this review is to provide the reader with practical knowledge concerning the relationship between diabetes mellitus and periodontal diseases. Over 200 articles have been published in the English literature over the past 50 years examining the relationship between these two chronic diseases. Data interpretation is often confounded by varying definitions of diabetes and periodontitis and different clinical criteria applied to prevalence, extent, and severity of periodontal diseases, levels of glycemic control, and complications associated with diabetes.

METHODS

This article provides a broad overview of the predominant findings from research published in English over the past 20 years, with reference to certain "classic" articles published prior to that time.

RESULTS

This article describes current diagnostic and classification criteria for diabetes and answers the following questions: 1) Does diabetes affect the risk of periodontitis, and does the level of metabolic control of diabetes have an impact on this relationship? 2) Do periodontal diseases affect the pathophysiology of diabetes mellitus or the metabolic control of diabetes? 3) What are the mechanisms by which these two diseases interrelate? and 4) How do people with diabetes and periodontal disease respond to periodontal treatment?

CONCLUSIONS

Diabetes increases the risk of periodontal diseases, and biologically plausible mechanisms have been demonstrated in abundance. Less clear is the impact of periodontal diseases on glycemic control of diabetes and the mechanisms through which this occurs. Inflammatory periodontal diseases may increase insulin resistance in a way similar to obesity, thereby aggravating glycemic control. Further research is needed to clarify this aspect of the relationship between periodontal diseases and diabetes.

Correlations of serum prolidase activity between bone turnover markers and mineral density in postmenopausal osteoporosis

Prolidase is a specific imidodipeptidase involved in collagen degradation. The increase in the enzyme activity is believed to be correlated with the increased intensity of collagen degradation. The aim of this study was to evaluate the serum prolidase activity and its relationship between bone turnover markers and bone mineral density (BMD) in postmenopausal osteoporosis. The study included 45 postmenopausal osteoporotic, 55 postmenopausal nonosteoporotic and 38 premenopausal healthy women. BMD was measured at the femoral neck and lumbar spine with DEXA. T score was more than 2.5 SD below the normal at the lumbar spine or femoral neck in postmenopausal osteoporotic patients. Serum levels of prolidase, C-terminal telopeptide of type I collagen (C-telopeptide), total alkaline phosphatase (ALP), osteocalcin (OC), urinary deoxypyridinoline (Dpd) and urinary creatinine were also assayed. C-telopeptide, total ALP, OC, urinary Dpd levels were significantly higher in postmenopausal osteoporotic group compared with premenopausal women. However, there was no statistical difference in serum prolidase activity between the three groups. There were also no significant correlations between serum prolidase and any biomarkers of bone turnover as well as BMD. To conclude, in postmenopausal osteoporotic women with increased bone turnover, serum prolidase concentration was not correlated with the biomarkers of bone formation or bone resorption and with BMD.

Is insulin an anabolic agent in bone? Dissecting the diabetic bone for clues

Diabetic osteoporosis is increasingly recognized as a significant comorbidity of type 1 diabetes mellitus. In contrast, type 2 diabetes mellitus is more commonly associated with modest increases in bone mineral density for age. Despite this dichotomy, clinical, in vivo, and in vitro data uniformly support the concept that new bone formation as well as bone microarchitectural integrity are altered in the diabetic state, leading to an increased risk for fragility fracture and inadequate bone regeneration following injury. In this review, we examine the contribution that insulin, as a potential anabolic agent in bone, may make to the pathophysiology of diabetic bone disease. Specifically, we have assimilated human and animal data examining the effects of endogenous insulin production, exogenous insulin administration, insulin sensitivity, and insulin signaling on bone. In so doing, we present evidence that insulin, acting as an anabolic agent in bone, can preserve and increase bone density and bone strength, presumably through direct and/or indirect effects on bone formation.