Serum Semicarbazide-sensitive Amine Oxidase Research Articles

Formic acid induces hypertension-related hemorrhage in hSSAOTG in mice and human

Hypertension is a confirmed risk factor for cerebral hemorrhage in humans. Which endogenous factor directly induces hypertension-related hemorrhage is unclear. In this study, 42 hemorrhagic patients with hypertension and hyperlipidemia and 42 age-matched healthy controls were enrolled. The contents of serum semicarbazide-sensitive amine oxidase (SSAO) and formic acid (FC, FC is a final product of SSAO through the oxidation of endogenous formaldehyde, which results from the enzymatic oxidative deamination of the SSAO substrate, methylamine) were examined in the patients after stroke. Hemorrhagic areas were quantified by computer tomography. In the animal study, hemorrhagic degree was assessed by hemotoxylin & eosin or tissue hemoglobin kits. The relationship between FC and blood pressure/hemorrhagic degree was examined in wild-type mice and hSSAOTG mice fed with high-fat diets or high-fat and -salt diets. The results showed that the levels of serum FC were positively correlated with blood pressure and hemorrhagic areas in hemorrhagic patients. Transfection of microRNA-134 could enhance SSAO expression in human vascular smooth muscle cells. Consistently, after treatment with high-fat and -salt diets, hSSAOTG mice exhibited higher levels of miR134 and FC, higher blood pressure, and more severe hemorrhage than wild-type mice. Interestingly, folic acid reduced hypertension and hemorrhage in hSSAOTG mice fed with high-fat diets. These findings suggest that FC is a crucial endogenous factor for hypertension and hemorrhage.

Hypoxia serves a key function in the upregulated expression of vascular adhesion protein‑1 invitro and in a rat model of hemorrhagic shock.

Hemorrhagic shock following major trauma results in mortality, but the function of vascular adhesion protein-1 (VAP-1), implicated in intracranial hemorrhage, remains unknown. This study aimed to determine whether expression of the AOC3 gene and its encoded protein, VAP-1, is altered by hypoxia. Rat hepatic sinusoidal endothelial cells (RHSECs) and rat intestinal microvascular endothelial cells (RIMECs) were transduced with a viral vector carrying AOC3, and AOC3 mRNA expression levels were measured by reverse transcription-quantitative polymerase chain reaction. VAP-1 protein expression levels were measured by western blot analysis and compared between normoxic and hypoxic conditions. Following this, AOC3 mRNA and VAP-1 protein expression levels in hepatic and intestinal tissues were assessed in a rat model of hemorrhagic shock with or without fluid resuscitation; and serum semicarbazide-sensitive amine oxidase (SSAO) activity was measured by fluorometric assays. The effects of 2-bromoethylamine (2-BEA) on AOC3/VAP-1 levels and 24 h survival were investigated. AOC3 mRNA and VAP-1 protein levels were increased in RHSECs and RIMECs by hypoxia, and in hepatic and intestinal tissues from rats following hemorrhagic shock. Hypoxia increased serum SSAO activity in these animals. 2-BEA reduced AOC3 mRNA and VAP-1 protein levels in hepatic and intestinal tissues from rats following hemorrhagic shock, and appeared to improve survival in animals not receiving resuscitation following hemorrhagic shock. In conclusion, hemorrhagic shock upregulates AOC3/VAP-1 expressions, and this potentially occurs via hypoxia. Therefore, inhibition of VAP-1 may be beneficial in the setting of hemorrhagic shock. Further studies are required to confirm these findings and to establish whether VAP-1 may be a valid target for the development of novel therapies for hemorrhagic shock.

Inactivation of Semicarbazide-Sensitive Amine Oxidase Stabilizes the Established Atherosclerotic Lesions via Inducing the Phenotypic Switch of Smooth Muscle Cells.

Given that the elevated serum semicarbazide-sensitive amine oxidase (SSAO) activity is associated with the severity of carotid atherosclerosis in clinic, the current study aims to investigate whether SSAO inactivation by semicarbazide is beneficial for established atherosclerotic lesions in LDLr knockout mice on a high-fat/high- cholesterol Western-type diet or after dietary lipid lowering. Despite no impact on plasma total cholesterol levels, the infiltration of circulating monocytes into peripheral tissues, and the size of atherosclerotic lesions, abrogation of SSAO activity resulted in the stabilization of established lesions as evidenced by the increased collagen contents under both conditions. Moreover, SSAO inactivation decreased Ly6Chigh monocytosis and lesion macrophage contents in hypercholesterolemic mice, while no effect was observed in mice after normalization of hypercholesterolemia by dietary lipid lowering. Strikingly, abrogation of SSAO activity significantly increased not only the absolute numbers of smooth muscle cells (SMCs), but also the percent of SMCs with a synthetic phenotype in established lesions of mice regardless of plasma cholesterol levels. Overall, our data indicate that SSAO inactivation in vivo stabilizes the established plaques mainly via inducing the switch of SMCs from a contractile to a synthetic phenotype. Targeting SSAO activity thus may represent a potential treatment for patients with atherosclerosis.

Inactivation of semicarbazide-sensitive amine oxidase induces the phenotypic switch of smooth muscle cells and aggravates the development of atherosclerotic lesions

Background and aimsClinical studies have demonstrated that serum semicarbazide-sensitive amine oxidase (SSAO) activities positively correlate with the progression of atherosclerosis. The aim of the present study is to investigate the effect of SSAO inactivation on the development of atherosclerosis. MethodsFemale LDLr knockout (KO) mice were given the Western-type diet for 6 and 9 weeks to induce the formation of early and advanced lesions, and semicarbazide (SCZ, 0.125%) was added into the drinking water to inactivate SSAO in vivo. ResultsDespite no impact on plasma total cholesterol levels, abrogation of SSAO by SCZ not only resulted in the enlargement of both early (1.5-fold, p = 0.0043) and advanced (1.8-fold, p = 0.0013) atherosclerotic lesions, but also led to reduced/increased lesion contents of macrophages/smooth muscle cells (SMCs) (macrophage: ∼0.74-fold, p = 0.0002(early)/0.0016(advanced); SMC: ∼1.55-fold, p = 0.0003(early)/0.0001(advanced)), respectively. Moreover, SSAO inactivation inhibited the migration of circulating monocytes into peripheral tissues and reduced the amount of circulating Ly6Chigh monocytes (0.7-fold, p = 0.0001), which may account for the reduced macrophage content in lesions. In contrast, the increased number of SMCs in lesions of SCZ-treated mice is attributed to an augmented synthetic vascular SMC phenotype switch as evidenced by the increased proliferation of SMCs and accumulation of collagens in vivo. ConclusionSSAO inactivation by SCZ promotes the phenotypic switch of SMCs and the development of atherosclerosis. The enzymatic activity of SSAO may thus represent a potential target in the prevention and/or treatment of atherosclerosis.

Determination of human serum semicarbazide-sensitive amine oxidase activity via flow injection analysis with fluorescence detection after online derivatization of the enzymatically produced benzaldehyde with 1,2-diaminoanthraquinone

A fast, simple, and sensitive flow injection analysis method was developed for the measurement of semicarbazide-sensitive amine oxidase (SSAO) activity in human serum. Benzaldehyde, generated by the action of SSAO after incubation of serum with benzylamine, was derivatized with a novel aromatic aldehyde-specific reagent (1,2-diaminoanthraquinone) and the fluorescent product was measured by fluorescence detection at excitation and emission wavelengths of 390 and 570nm, respectively. Serum SSAO activity was defined as benzaldehyde (nmol) formed per milliliter serum per hour. The method was linear over SSAO activity of 0.2–150.0nmolmL−1h−1 with a detection limit of 0.06nmolmL−1h−1. The %RSD of intra-day and inter-day precision did not exceed 9.4% and the accuracy ranged from −6.5 to −0.6%. The method was applied for the determination of the serum SSAO activity in healthy controls (C, n=24) and diabetes mellitus patients (DM, n=18). It was demonstrated that the activity (mean±SE) of SSAO in diabetics sera was significantly higher than that in healthy subjects’ ones (DM; 73.3±1.8nmolmL−1h−1 vs C; 58.9±2.2nmolmL−1h−1, P<0.01).

Aspects of metabolic changes in first-episode drug-naïve schizophrenic patients.

Aim The aim of the study was to investigate the state of parameters characterising different sites of metabolism and the degree of endogenous intoxication in first-episode drug-naïve schizophrenic [first episode of schizophrenia (FES)] patients. It is hypothesised that the FES is the initial step in the development of pathologically disturbed biochemical status that is characteristic of chronic schizophrenia. Platelet monoamine oxidase (MAO) and serum semicarbazide-sensitive amine oxidase (SSAO) activities, serum concentrations of middle-mass endotoxic molecules (MMEM) and malondialdehyde and parameters of the serum albumin functional state were measured in 26 FES patients and 15 age-matched healthy controls. Severity of disorder before the treatment was 75.5 ± 2.2, according to Positive and Negative Syndrome Scale score. FES patients were characterised by significant increase in MAO activity (99%) and MMEM concentration (124%) and significant decrease in SSAO activity (26%) as compared with controls. Changes of all other parameters were insignificant. Regression analysis has showed a significant relationship of three parameters - MAO, SSAO and MMEM, with values of PANNS score. Two methods of extraction of factor analysis revealed that MAO and SSAO belonged to Factor 1, whereas MMEM and albumin functional parameters belonged to Factor 2. Comparing our earlier data on chronic schizophrenic patients with present data, we hypothesise that FES patients are at the stage that leads to a stable, pathological state of metabolism.

LC-MS method for determining the activity of semicarbazide-sensitive amine oxidase in rodents

Semicarbazide-sensitive amine oxidase (SSAO) is present in various mammalian tissues and in blood plasma. Elevation of SSAO activity is linked to vascular disorders associated with pathological conditions such as diabetic complications, heart failure and vascular dementia. In the present paper, a high performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS) method is developed to determine the SSAO activity. Methylamine is used as physiological substrate for the enzyme activity assay of SSAO. Formaldehyde, the enzymatic reaction product, was derivatized by dopamine, and separated by a silica-based pentafluorophenyl column. The calibration curve was linear over the range of 0.03–4.00 μM of formaldehyde concentration, with 0.03 μM the lower limit of quantification (LOQ). The inter-day and intra-day precisions ranged from 2.2% to 7.9% and 4.4% to 9.2% respectively for each quality control sample of formaldehyde at 0.06, 0.50, and 2.00 μM. The accuracy ranged from 96.0% to 111.5%. The limit of detection (LOD) for serum SSAO activity was 1 nmol h−1 mg−1 protein. The method was successfully applied for the determination of SSAO activity in both mouse serum and rat tissues. SSAO activity of the serum in diabetes mice was significantly increased compared with the control and was inhibited by 2-bromoethylamine in vivo. The levels of SSAO activity in rat lung, spleen, aorta, kidney and brain tissues were significantly decreased by semicarbazide in vitro.

S45-03 - Biochemical and biophysical aspects of the pathophysiology of first episode of schizophrenia

IntroductionThe knowledge of pathophysiology of first psychotic episode is still fragmentary.AimTo investigate some biochemical and biophysical parameters in first-episode, drug-naive schizophrenic (FES) patients.Methods26 FES patients (ICD-10; F 20.0 and F 20.3) and 15 age-and gender-match volunteers were investigated. Clinical severity of FES patients were assessed by PANSS scale. Platelet monoamine oxidase (MAO) and serum semicarbazide-sensitive amine oxidase (SSAO) activities, middle-mass endotoxic molecules (MMEM) and malondialdehyde (MDA) levels were measured using respective methods. Steady-state and subnanosecond fluorescent spectroscopy were used for the investigation of albumin conformational changesResults Severity of disorder prior the treatment was 75.5 ± 2.2 (PANSS score). FES patients were characterized by significant increase in MAO activity (99%) and MMEM concentration (124%) and significant decrease in SSAO activity (26%) as compared with controls. Changes of albumin conformational and functional parameters (“effective” albumin concentration and“reserve” of albumin binding) estimated by steady-state fluorescent spectroscopy were insignificant. Factor analysis revealed that MAO and SSAO are more tightly connected with pathogenetic mechanisms of FES then MMEM, MDA and albumin functional parameters. Significant conformational changes of albumin of FES patients were detected using pulse fluorescent spectroscopy with subnanosecond resolution. Results are compared with the data received in chronic schizophrenic patients.ConclusionFrom pathophysiological point of view FES is the initial step in development of pathologically disturbed biochemical status characteristic to chronic schizophrenia.The study was supported by grant # 3156 from International Science and Technology Center (ISTC).

P03-348 - Biochemical and biophysical aspects of the pathophysiology of first episode of schizophrenia

IntroductionThe knowledge of pathophysiology of first psychotic episode is still fragmentary.AimTo investigate some biochemical and biophysical parameters in first-episode, drug-naive schizophrenic (FES) patients.Methods26 FES patients (ICD-10; F 20.0 and F 20.3) and 15 age-and gender-match volunteers were investigated. Clinical severity of FES patients were assessed by PANSS scale. Platelet monoamine oxidase (MAO) and serum semicarbazide-sensitive amine oxidase (SSAO) activities, middle-mass endotoxic molecules (MMEM) and malondialdehyde (MDA) levels were measured using respective methods. Steady-state and subnanosecond fluorescent spectroscopy were used for the investigation of albumin conformational changes.ResultsSeverity of disorder prior the treatment was 75.5 ± 2.2 (PANSS score). FES patients were characterized by significant increase in MAO activity (99%) and MMEM concentration (124%) and significant decrease in SSAO activity (26%) as compared with controls. Changes of albumin conformational and functional parameters (“effective” albumin concentration and “reserve” of albumin binding) estimated by steady-state fluorescent spectroscopy were insignificant. Factor analysis revealed that MAO and SSAO are more tightly connected with pathogenetic mechanisms of FES then MMEM, MDA and albumin functional parameters. Significant conformational changes of albumin of FES patients were detected using pulse fluorescent spectroscopy with subnanosecond resolution. Results are compared with the data received in chronic schizophrenic patients.ConclusionFrom pathophysiological point of view FES is the initial step in development of pathologically disturbed biochemical status characteristic to chronic schizophrenia. The study was supported by grant # 3156 from International Science and Technology Center (ISTC).

P03-243 - Disturbance of neurotransmitters monoamines and indices of reducing-oxidizing processes in patient with the first episode of schizophrenia (FES)

IntroductionEffective treatment of FES patients may lead to achievement of long-term remission, decrease the number of relapses and increase the level of social activity and quality of life.AimTo study some pathophysiological mechanisms of FES.MethodsThe group of patients who were investigated clinically and biochemically consists of 26 persons (11 women and 15 men, average age 28.2 ± 9.5 years) with the first psychotic episode (F20.0; F20.3). Some biochemical parameters, representing the monoaminergic systems, and some biophysical parameters, representing reducing-oxidizing processes, were investigated. These parameters in all patients were estimated following the admission and prior to any treatment.ResultsThe severity of the disorder on admission to the clinic according to PANSS score was 75,5 ± 2,2 (i.e., moderately severe). Patients with FES were characterized by a significant increase of platelet momnoamine oxidase activity (by 107%; р &lt; 0,01) and decrease of serum semicarbazide-sensitive amine oxidase activity (by 29%; p &lt; 0,001) in comparison to the controls. Both reactive capability of SH-group (Cys-34 residue) of serum albumin, the main source of thiols of plasma and intersticial fluid, measured in reaction with thiol-specific reagent - dithyonitrobenzoic acide, and kinetic coefficient were decreased in FES patients (by 24%; p = 0,02) in comparison to controls.ConclusionThese results show that FES patients are characterized by pronounced metabolic disturbances.

Changes in the activities of semicarbazide-sensitive amine oxidase in inferior mesenteric artery segments and in serum of patients with type 2 diabetes

This study aimed to evaluate the semicarbazide-sensitive amine oxidase (SSAO) activity in human arterial tissues and in serum of patients with type 2 diabetes. The SSAO activity, with (14)C-benzylamine as substrate, was measured in homogenates of human inferior mesenteric arteries obtained at surgery, from 10 patients with type 2 diabetes and 16 non-diabetic patients and in the serum of 39 patients with type 2 diabetes and 40 non-diabetic control patients. The SSAO activity in the homogenates of vascular tissue was significantly lower in the diabetics than in the non-diabetics (P = 0.001). The SSAO activity in the serum of patients with type 2 diabetes was higher when compared with control group (P = 0.0001). In conclusion, the SSAO activity increased in the serum and decreased in the arterial tissue. These findings suggest damage in the vascular tissue and support the hypothesis that serum SSAO may be a useful biochemical marker for diabetes.

P03-209 Peculiarities of biochemical changes in the first-episode drug naïve schizophrenic patients

Aim:The aim of the study was to investigate the state of parameters characterizing different sites of metabolism and the degree of endogenous intoxication in drug-naïve first episode schizophrenic patients (FES).Methods:Platelet monoamine oxidase (MAO) and serum semicarbazide-sensitive amine oxidase (SSAO) activities, serum concentrations of middle-mass endotoxic molecules (MMEM) and malondialdehyde and parameters of serum albumin functional state (Uzbekov et al., 2006) were measured in 16 FES patients and 15 age-matched healthy volunteers.Results:Severity of disorder prior the treatment was 73.1±12.5 according to PANSS score. FES patients were characterized by significant increase in MAO activity (by 107 %) and MMEM concentration (by 140 %) and significant decrease in SSAO activity (by 29 %) as compared with controls. Degree of endogenous intoxication in 13 patients was assessed as moderate and severe. Changes of all other parameters were insignificant. Regression analysis has shown significant relationship of 3 parameters - MAO (p&lt; 0,01), SSAO (p&lt; 0,01) and MMEM (p&lt; 0,02) with values of PANNS score. Three methods of extraction of factor analysis have revealed that MAO and SSAO are belonged to factor 1 whereas MMEM and albumin functional parameters - to factor 2.Conclusions:It is supposed that MAO and SSAO are integral components of schizophrenia pathogenetic mechanisms. Comparing our earlier data on chronic schizophrenic patients with these data we suppose that FES patients are on the stage of the formation of the pathological state of metabolism.Study was partially supported by the ISTC grant 3156.

Semicarbazide-sensitive amine oxidase activity and total nitrite and nitrate concentrations in serum: novel biochemical markers for type 2 diabetes?

The aim of this study was to evaluate the activity of semicarbazide-sensitive amine oxidase (SSAO) and the total nitrite and nitrate (NO( x )) concentrations in serum from type 2 diabetic patients and control subjects in order to evaluate if they could be used as novel diabetic markers. We studied 38 type 2 diabetic patients and 35 control subjects. Serum samples from those subjects were evaluated by radiochemical methods for SSAO activity using (14)C-benzylamine. Serum NO( x ) concentrations were obtained as an index of nitric oxide production by the Griess reaction. Serum SSAO activity was higher in type 2 diabetic patients than in control group and serum SSAO in type 2 diabetic correlated with age, serum creatinine and total cholesterol. Serum NO( x ) levels in type 2 diabetic patients were also significantly higher than those in the control group. Serum NO( x ) levels in control group correlated with serum SSAO activity. In conclusion, the increase in the SSAO activity and NO( x ) levels observed in type 2 diabetic patients could be parameters to take in account and play relevant role in diabetes development. SSAO and NO( x ) are suggested as markers for prognostic of diabetes.

Alteration of serum semicarbazide-sensitive amine oxidase activity in chronic renal failure

Despite recent intensive investigations, physiological and pathological role of semicarbazide-sensitive amine oxidase (SSAO) is far from clear. In this study, serum SSAO activity was determined, radiochemically, in various groups of uremic patients: haemodialysed (HD), peritoneally dialysed (PD) and those receiving conservative treatment but still not dialysed (ND), as well as in controls. Reduced enzyme activity was found in HD uremic patients before and after dialysis treatment, compared to controls (5260 +/- 862 and 6011 +/- 958 pmol/h/ml vs. 8601 +/- 283 pmol/h/ml, p < 0.01 and p < 0.05, respectively). The activity was slightly lower in PD, and normal in ND patients. In HD patients SSAO activity was also determined by an assay based on the formation of hydrogen peroxide, and was found to be elevated compared to controls (2384 +/- 323 pmol/h/ml vs. 1437 +/- 72 pmol/h/ml, p < 0.05). The elevated serum SSAO activity measured through the detection of the enzyme-generated hydrogen peroxide in HD patients might indicate its contribution to the accelerated atherosclerotic disease observed in uremia.

Semicarbazide-sensitive amine oxidase: current status and perspectives.

Semicarbazide-sensitive amine-oxidase (SSAO) is present in various human tissues and in plasma. Oxidative deamination of short-chain aliphatic amines is catalyzed by this enzyme to afford the corresponding aldehydes, ammonia and hydrogen peroxide. Methylamine and aminoacetone have been recognized to be physiological substrates for SSAO. There are several pathological states where increased serum SSAO activity have been found, such as diabetes mellitus, congestive heart failure, multiple types of cerebral infarction, uraemia, and hepatic cirrhosis. The role of SSAO in pathophysiology of diabetes has been most extensively investigated. The elevated formation of the potentially cytotoxic products of the enzyme may contribute to the endothelial injury of blood vessels, resulting in the early development of severe atherosclerosis; it may also contribute to the pathogenesis of diabetic angiopathy. It is now suggested that SSAO inhibitors may prevent the development of atherosclerosis and diabetic complications as well. Inhibitors can be conveniently subdivided into the main groups of hydrazine derivatives, arylalkylamines, propenyl- and propargylamines, oxazolidinones, and haloalkylamines. Of them, aryl(alkyl)hydrazines, and 3-halo-2-phenylallylamines are generally very strong SSAO inhibitors. Most of these inhibitors of SSAO have been originally developed for other purposes, or they are simple chemical reagents with highly reactive structural element(s); these compounds have not been able to fulfil all criteria of high potency, selectivity, and acceptable toxicity. New potent compounds with selectivity and low toxicity are needed, which may prove useful tools for understanding the roles and function of SSAO, or they may even be valuable substances for treatment of various diseases.

Semicarbazide-sensitive amine oxidase (SSAO): present and future.

Although the existence of plasma and tissue-bound semicarbazide-sensitive amine oxidases (SSAOs) has been recognised for a long time, the physiological relevance of these enzymes still remains uncertain. The ability of SSAO to metabolise various aliphatic and aromatic monoamines differs between species, which limits the predictive value of the animal studies for human tissues. SSAO plays a protective role because the oxidative deamination of monoamines reduces their pharmacological activities. However, the products of deamination may be toxic. Several observations indicated that the plasma and tissue SSAO activities differ in certain disease states. It is proposed that selective inhibitors, of low toxicity, might be protective, through inhibiting the formation of the toxic products and the countering the disease-related elevation of SSAO activity. We reported earlier that there was a significant correlation between the serum SSAO activity and severity of atherosclerosis, as well as the intima-media thickness and serum cholesterol levels. Thus SSAO activity might be a clinical marker in the prognostic evaluation of diabetic-vascular complications. Although molecular biological studies are providing more and more reliable knowledge about the enzyme structure, many more studies should be carried out in different disease states are necessary to discover the clinical meaning of the enzyme function.

Serum semicarbazide-sensitive amine oxidase (SSAO) activity is an independent marker of carotid atherosclerosis

Background: Clinical and experimental studies suggest that increased activity of semicarbazide-sensitive amine oxidase (SSAO) and the production of cytotoxic metabolites (e.g., formaldehyde and hydrogen peroxide) may play an important role in the pathogenesis of atherosclerosis. The present study was designed to assess the relationship between the increased activity of the enzyme and the severity of atherosclerosis in diabetic and control subjects. Methods: The study included 29 patients with type 2 diabetes mellitus and 25 control subjects. Human serum SSAO activity was determined by using 14C-benzylamine as substrate. Mean common carotid intima–media thickness (IMT), Crouse score and Bogousslawsky score was evaluated by color-coded, high-resolution duplex carotid sonography. Results: Serum SSAO activity was significantly increased in patients with type 2 diabetes compared to controls. Carotid plaque score (Crouse score), total cholesterol level and age-corrected intima–media thickness showed positive correlation with enzyme activity in control subjects. In patients with diabetes, serum SSAO activity correlated with the severity of carotid stenosis (Bogousslawsky score) as well as the carotid plaque score. Conclusions: Determination of serum SSAO activity might be a candidate biochemical marker of early atherosclerosis and diabetic macrovascular complications.

Determination of human serum semicarbazide-sensitive amine oxidase activity: a possible clinical marker of atherosclerosis.

Semicarbazide-sensitive amine oxidase (SSAO) is present in the plasma membrane of several human tissues, e.g. vascular smooth muscle cell adipocytes, and is also found in human serum. Some previous studies on cultured endothelial cells indicate that cytotoxic metabolites (e.g. hydrogen peroxide, formaldehyde, acrolein) formed by serum SSAO may cause endothelial injury and subsequently induce atherosclerosis. To investigate the role of this enzyme in the pathogenesis of macrovascular complications in diabetes, a simple and sensitive radiometric procedure was adapted for human serum measurements. Serum SSAO activity of 35 patients with non-insulin dependent diabetes mellitus (NIDDM) and that of 30 controls was determined using [14C]-benzylamine as substrate. The severity of atherosclerosis was assessed by carotid sonography. Diabetic patients with atherosclerosis exhibited a higher SSAO activity compared to diabetic patients without complications (212.91 +/- 90.54 pmol/mg protein/h versus 133.17 +/- 65.40 pmol/mg protein/h, P <0.04). In diabetic patients without complications, serum SSAO activity was elevated compared to control subjects (133.17 +/- 65.40 pmol/mg protein/h versus 91.79 +/- 31.70 pmol/mg protein/h, P <0.01). These results suggest that determination of human serum SSAO activity might be a useful marker in the prognostic evaluation of diabetic angiopathy and atherosclerosis.

Elevated serum semicarbazide-sensitive amine oxidase activity in non-insulin-dependent diabetes mellitus: Correlation with body mass index and serum triglyceride

Previous clinical studies reported elevated semicarbazide-sensitive amine oxidase (SSAO) activity in insulin-dependent diabetes mellitus (IDDM), but there are not sufficient data about SSAO in non-insulin-dependent diabetes mellitus (NIDDM). The present study was conducted to investigate serum SSAO activity in NIDDM patients compared with nondiabetic and IDDM patients. Serum SSAO activity in 61 patients with diabetes (n = 34 NIDDM and n = 27 IDDM) and 36 controls was determined using 14C-benzylamine as a substrate. NIDDM and IDDM patients exhibited higher SSAO activity compared with controls ([mean ± SD] NIDDM, 164.60 ± 69.43 pmol/mg protein/h, P < .0001; IDDM, 143.91 ± 72.45 pmol/mg protein/h, P < .002; control, 91.46 ± 28.11 pmol/mg protein/h). There was a significant positive correlation between serum SSAO activity and the body mass index (BMI), body weight, hemoglobin A 1C (HbA 1c), fasting plasma glucose, and triglycerides. Within the control group, SSAO correlated with total cholesterol levels. The progression and severity of diabetic complications such as angiopathy may be exacerbated by cytotoxic metabolites (eg, formaldehyde and hydrogen peroxide) formed by SSAO. These results reveal the possibility that elevated serum SSAO activity in association with obesity and hyperlipidemia may be a cardiovascular risk factor in diabetes mellitus.

Aminoguanidine inhibits semicarbazide-sensitive amine oxidase activity: implications for advanced glycation and diabetic complications.

Aminoguanidine, a nucleophilic hydrazine, has been shown to be capable of blocking the formation of advanced glycation end products. It reduces the development of atherosclerotic plaques and prevents experimental diabetic nephropathy. We have found that aminoguanidine is also quite potent at inhibiting semicarbazide-sensitive amine oxidase (SSAO) both in vitro and in vivo. The inhibition is irreversible. This enzyme catalyses the deamination of methylamine and aminoacetone, which leads to the production of cytotoxic formaldehyde and methylglyoxal, respectively. Serum SSAO activity was reported to be increased in diabetic patients and positively correlated with the amount of plasma glycated haemoglobin. Increased SSAO has also been demonstrated in diabetic animal models. Urinary excretion of methylamine is substantially increased in the rats following acute or chronic treatment with aminoguanidine. Urinary methylamine levels were substantially increased in streptozotocin (STZ)-induced diabetic rats following administration of aminoguanidine. The non-hydrazine SSAO inhibitor (E)-2-(4-fluorophenethyl)-3-fluoroallylamine hydrochloride (MDL-72974A) has been shown to reduce urinary excretion of lactate dehydrogenase (an indicator of nephropathy) in STZ-induced diabetic rats. Formaldehyde not only induces protein crosslinking, but also enhances the advanced glycation of proteins in vitro. The results support the hypothesis that increased SSAO-mediated deamination may be involved in structural modification of proteins and contribute to advanced glycation in diabetes. The clinical implications for the use of aminoguanidine to prevent glycoxidation have been discussed.