Semicarbazide-sensitive Amine Oxidase Research Articles

Elucidation of novel drought-responsive genes from tuber transcriptome of cassava under water deficit stress

Cassava (Manihot esculenta Carntz) is the major starchy root crop grown in the tropical parts of the world. Two cassava clones contrasting for their drought tolerance capacity (8S501- drought tolerant and H97-drought sensitive) were selected and grown in the field for studying the agronomical and molecular changes in both the clones under drought stress conditions. A reduction in the number of tuberous roots per plant, tuberous root length, average single tuber weight and tuber yield per plant was observed under drought stress when compared with the control conditions and also significantly lower mean values were observed for the sensitive clone H97 than that of the tolerant clone 8S501 when measured at 60 days of stress. Transcriptome sequencing of the tuber tissues of the two clones was done at 60 days of imposing drought stress. Different genes belonging to various groups like aquaporins, transporter genes, growth regulator related genes, calcium binding and mineral transfer-related genes, transferase genes and transcription factors were differentially expressed in the tubers under drought stress. Comparative transcriptomics revealed that acyl-CoA oxidase, primary-amine oxidase, glutathione peroxidase, vesicle transport, late embryogenesis abundant protein related, histone demethylase, BR-signaling kinase, palmitoyltransferase, DNA mismatch repair protein, heat shock protein related, starch/sucrose metabolic pathway related and MFS transporter genes were differentially expressed in the tubers of the tolerant clone 8S501 relative to the susceptible clone H97.

A Novel MAO-B/SSAO Inhibitor Improves Multiple Aspects of Dystrophic Phenotype in mdx Mice

Duchenne muscular dystrophy (DMD) is one of the most frequent and severe childhood muscle diseases. Its pathophysiology is multifaceted and still incompletely understood, but we and others have previously shown that oxidative stress plays an important role. In particular, we have demonstrated that inhibition of mitochondrial monoamine oxidases could improve some functional and biohumoral markers of the pathology. In the present study we report the use of dystrophic mdx mice to evaluate the efficacy of a dual monoamine oxidase B (MAO-B)/semicarbazide-sensitive amine oxidase (SSAO) inhibitor, PXS-5131, in reducing inflammation and fibrosis and improving muscle function. We found that a one-month treatment starting at three months of age was able to decrease reactive oxygen species (ROS) production, fibrosis, and inflammatory infiltrate in the tibialis anterior (TA) and diaphragm muscles. Importantly, we also observed a marked improvement in the capacity of the gastrocnemius muscle to maintain its force when challenged with eccentric contractions. Upon performing a bulk RNA-seq analysis, PXS-5131 treatment affected the expression of genes involved in inflammatory processes and tissue remodeling. We also studied the effect of prolonged treatment in older dystrophic mice, and found that a three-month administration of PXS-5131 was able to greatly reduce the progression of fibrosis not only in the diaphragm but also in the heart. Taken together, these results suggest that PXS-5131 is an effective inhibitor of fibrosis and inflammation in dystrophic muscles, a finding that could open a new therapeutic avenue for DMD patients.

The first selective VAP-1 inhibitor in China, TT-01025-CL: safety, tolerability, pharmacokinetics, and pharmacodynamics of single- and multiple-ascending doses.

Introduction: TT-01025-CL is an oral, irreversible small molecule that potently inhibits vascular adhesion protein-1 (VAP-1) for the treatment of inflammation associated with non-alcoholic steatohepatitis (NASH). The objectives of this study were to evaluate the safety/tolerability, pharmacokinetics, and pharmacodynamics of TT-01025-CL, a VAP-1 inhibitor, in healthy Chinese volunteers. Methods: Double-blind, placebo-controlled, dose-escalation studies were conducted in subjects randomized to receive oral once-daily TT-01025-CL (ranges: 10-300mg [single dose]; 20-100mg for 7days [multiple doses]) or placebo under fasting conditions. Safety and tolerability were monitored throughout the study. Pharmacokinetic (PK) parameters were determined using non-compartment analysis. The activity of semicarbazide-sensitive amine oxidase (SSAO)-specific amine oxidase and the accumulation of methylamine in plasma were evaluated as pharmacodynamic (PD) biomarkers. Results: A total of 36 (single-dose group) and 24 (multiple-dose group) subjects were enrolled in the study. No serious adverse events (AEs) were reported, and no subject discontinued due to an AE. All treatment-emergent adverse events (TEAEs) were mild and moderate in intensity. No dose-dependent increase in the intensity or frequency of events was observed. TT-01025-CL was rapidly absorbed after administration. In the single-ascending dose (SAD) study, median Tmax ranged from 0.5 to 2h and mean t1/2z ranged from 2.09 to 4.39h. PK was linear in the range of 100-300mg. The mean Emax of methylamine ranged from 19.167 to 124.970ng/mL, with mean TEmax ranging from 13.5 to 28.0h. The complete inhibition (>90%) of SSAO activity was observed at 0.25-0.5h post-dose and was maintained 48-168h post-dose. In the multiple-ascending dose (MAD) study, a steady state was reached by day 5 in the 40mg and 100mg dose groups. Negligible accumulation was observed after repeated dosing. PK was linear in the range of 20-100mg. Plasma methylamine appeared to plateau at doses of 20mg and above, with mean Emax ranging from 124.142 to 156.070ng/mL and mean TEmax ranging from 14.2 to 22.0h on day 7. SSAO activity in plasma was persistently inhibited throughout the treatment period. No evident change in methylamine and SSAO activity was observed in the placebo groups. Conclusion: TT-01025-CL was safe and well-tolerated at a single dose of up to 300mg and multiple doses of up to 100mg once daily for 7 consecutive days. Absorption and elimination occurred rapidly in healthy volunteers. Linearity in plasma exposure was observed. TT-01025-CL inhibited SSAO activity rapidly and persistently in humans. The profile of TT-01025-CL demonstrates its suitability for further clinical development.

L-tryptophan anaerobic fermentation for indole acetic acid production: Bacterial enrichment and effects of zero valent iron

Indole acetic acid (IAA) as a plant hormone, was one of the valuable products of anaerobic fermentation. However, the enriching method remained unknown. Moreover, whether zero valent iron (ZVI) could enhance IAA production was unexplored. In this work, IAA producing bacteria Klebsiella (63 %) was enriched successfully. IAA average production rate and concentration were up to 3 mg/L/h and 56 mg/L. With addition of 1 g/L ZVI, IAA average production rate and concentration was increased for 2 and 3 folds. Mechanisms indicated ZVI increased Na+K+-ATP activity and electron transport activity for 2 folds and 1 fold. Moreover, macro transcription determined indole pyruvate pathway activity like primary-amine oxidase, indole pyruvate decarboxylase and aldehyde dehydrogenase were increased for 146 %, 187 %, and 557 %, respectively. Therefore, ZVI was suitable for enhancement IAA production from mixed culture anaerobic fermentation.

Midbrain FA initiates neuroinflammation and depression onset in both acute and chronic LPS-induced depressive model mice

Both exogenous gaseous and liquid forms of formaldehyde (FA) can induce depressive-like behaviors in both animals and humans. Stress and neuronal excitation can elicit brain FA generation. However, whether endogenous FA participates in depression occurrence remains largely unknown. In this study, we report that midbrain FA derived from lipopolysaccharide (LPS) is a direct trigger of depression. Using an acute depressive model in mice, we found that one-week intraperitoneal injection (i.p.) of LPS activated semicarbazide-sensitive amine oxidase (SSAO) leading to FA production from the midbrain vascular endothelium. In both in vitro and in vivo experiments, FA stimulated the production of cytokines such as IL-1β, IL-6, and TNF-α. Strikingly, one-week microinfusion of FA as well as LPS into the midbrain dorsal raphe nucleus (DRN, a 5-HT-nergic nucleus) induced depressive-like behaviors and concurrent neuroinflammation. Conversely, NaHSO3 (a FA scavenger), improved depressive symptoms associated with a reduction in the levels of midbrain FA and cytokines. Moreover, the chronic depressive model of mice injected with four-week i.p. LPS exhibited a marked elevation in the levels of midbrain LPS accompanied by a substantial increase in the levels of FA and cytokines. Notably, four-week i.p. injection of FA as well as LPS elicited cytokine storm in the midbrain and disrupted the blood–brain barrier (BBB) by activating microglia and reducing the expression of claudin 5 (CLDN5, a protein with tight junctions in the BBB). However, the administration of 30 nm nano-packed coenzyme-Q10 (Q10, an endogenous FA scavenger), phototherapy (PT) utilizing 630-nm red light to degrade FA, and the combination of PT and Q10, reduced FA accumulation and neuroinflammation in the midbrain. Moreover, the combined therapy exhibited superior therapeutic efficacy in attenuating depressive symptoms compared to individual treatments. Thus, LPS-derived FA directly initiates depression onset, thereby suggesting that scavenging FA represents a promising strategy for depression treatment.

ω-(5-Phenyl-2H-tetrazol-2-yl)alkyl-substituted glycine amides and related compounds as inhibitors of the amine oxidase vascular adhesion protein-1 (VAP-1)

Vascular adhesion protein-1 (VAP-1), also known as plasma amine oxidase or semicarbazide-sensitive amine oxidase, is an enzyme that degrades primary amines to aldehydes with the formation of hydrogen peroxide and ammonia. Among others, it plays a role in inflammatory processes as it can mediate the migration of leukocytes from the blood to the inflamed tissue. We prepared a series of ω-(5-phenyl-2H-tetrazol-2-yl)alkyl-substituted glycine amides and related compounds and tested them for inhibition of purified bovine plasma VAP-1. Compounds with submicromolar activity were obtained. Studies on the mechanism of action revealed that the glycine amides are substrate inhibitors, i.e., they are also converted to an aldehyde derivative. However, the reaction proceeds much more slowly than that of the substrate used in the assay, whose conversion is thus blocked. Examination of the selectivity of the synthesized glycine amides with respect to other amine oxidases showed that they inhibited diamine oxidase, which is structurally related to VAP-1, but only to a much lesser extent. In contrast, the activity of monoamine oxidase A and B was not affected. Selected compounds also inhibited VAP-1 in human plasma. The IC50 values measured were higher than those determined with the bovine enzyme. However, the structure–activity relationships obtained with the glycine amides were similar for both enzymes.

Vascular adhesion protein-1-targeted PET imaging in autoimmune myocarditis

BackgroundVascular adhesion protein-1 (VAP-1) is an adhesion molecule and primary amine oxidase, and Gallium-68-labeled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetra-acetic acid conjugated sialic acid-binding immunoglobulin-like lectin 9 motif containing peptide ([68Ga]Ga-DOTA-Siglec-9) is a positron emission tomography (PET) tracer targeting VAP-1. We evaluated the feasibility of PET imaging with [68Ga]Ga-DOTA-Siglec-9 for the detection of myocardial lesions in rats with autoimmune myocarditis.MethodsRats (n = 9) were immunized twice with porcine cardiac myosin in complete Freund’s adjuvant. Control rats (n = 6) were injected with Freund’s adjuvant alone. On day 21, in vivo PET/computed tomography (CT) imaging with [68Ga]Ga-DOTA-Siglec-9 was performed, followed by ex vivo autoradiography, histology, and immunohistochemistry of tissue sections. In addition, myocardial samples from three patients with cardiac sarcoidosis were studied.Results[68Ga]Ga-DOTA-Siglec-9 PET/CT images of immunized rats showed higher uptake in myocardial lesions than in myocardium outside lesions (SUVmean, 0.5 ± 0.1 vs 0.3 ± 0.1; P = .003) or control rats (SUVmean, 0.2 ± 0.03; P < .0001), which was confirmed by ex vivo autoradiography of tissue sections. Immunohistochemistry showed VAP-1-positive staining in lesions of rats with myocarditis and in patients with cardiac sarcoidosis.ConclusionVAP-1-targeted [68Ga]Ga-DOTA-Siglec-9 PET is a potential novel technique for the detection of myocardial lesions.

Pathogenetic mechanisms of mental disorders: endogenous intoxication

There is described the existence of the syndrome of endogenous intoxication in patients with mental disorders. Oxidative stress, middle-mass endotoxic molecules, disorders in functional properties of the blood albumin and the thiols of the albumin, disturbances in the state of the neurotrophic factors and in the activity of several enzymes, including monoamine oxidase and semicarbazide-sensitive amine oxidase, contribute to the development of the endogenous intoxication. We introduce the scheme of the possible pathogenetic mechanisms of the development of the endogenous intoxication and the ways of its overcoming.

Amine oxidase copper-containing 3 aggravates cardiac remodelling by generating hydrogen peroxide after myocardial infarction.

Amine oxidase copper-containing 3 (AOC3) is a member of the semicarbazide-sensitive amine oxidase enzyme family. It acts as an ectoenzyme catalysing the oxidative deamination of primary amines and generating hydrogen peroxide (H2 O2 ). While AOC3 is implicated in cardiovascular diseases such as atherosclerosis, its role in cardiac remodelling after myocardial infarction (MI) is unclear. In this study, we first confirmed a long-term upregulation of AOC3 in both cardiac myofibroblasts after MI in vivo and angiotensin II (ANGII)-treated cardiac fibroblasts in vitro. AOC3 knockdown not only inhibited the activation of cardiac fibroblasts induced by ANGII but also alleviated cardiac fibrosis in mice after MI. Using sh-AOC3 lentiviruses, exogenous recombinant AOC3 (r-AOC3), semicarbazide (an AOC3 inhibitor), and catalase (a hydrogen peroxide scavenger) treatments, we also demonstrated that AOC3 promoted H2 O2 generation, increased oxidative stress, and enhanced ERK1/2 activation, which were responsible for the activation of cardiac fibroblasts. In particular, AOC3 knockdown also improved cardiac function and hypertrophy after MI. Through a coculture system, we confirmed that AOC3 expressed on cardiac myofibroblasts was able to enhance oxidative stress and induce hypertrophy of cardiomyocytes by promoting H2 O2 generation. Similarly, r-AOC3 promoted H2 O2 generation and resulted in oxidative stress and hypertrophy of cardiomyocytes, which were almost inhibited by both semicarbazide and catalase. In conclusion, AOC3 plays a critical role in cardiac fibrosis and hypertrophy after MI by promoting the generation of H2 O2 . AOC3 is a promising therapeutic target against cardiac remodelling. © 2023 The Pathological Society of Great Britain and Ireland.

Reader Response: Association of Amount of Weight Lost After Bariatric Surgery With Intracranial Pressure in Women With Idiopathic Intracranial Hypertension.

I read the article by Mollan et al.1 regarding weight loss and intracranial hypertension (IH) with interest. Gastric bypass results in decreased dicarbonyl stress (DS).2 DS-related compounds, such as methylgloxal, are associated with the breakdown of the blood-brain barrier,3 as seen in IH through the glycation of biomolecules and the production of advanced glycation end products (AGEs).3,4 Inhibiting semicarbazide-sensitive amine oxidase, which causes DS, with caffeine may lead to decreased weight gain and AGEs.5

The Impact of Semicarbazide Sensitive Amine Oxidase Activity on Rat Aortic Vascular Smooth Muscle Cells.

Semicarbazide-sensitive amine oxidase (SSAO) is both a soluble- and membrane-bound transmembrane protein expressed in the vascular endothelial and in smooth muscle cells. In vascular endothelial cells, SSAO contributes to the development of atherosclerosis by mediating a leukocyte adhesion cascade; however, its contributory role in the development of atherosclerosis in VSMCs has not yet been fully explored. This study investigates SSAO enzymatic activity in VSMCs using methylamine and aminoacetone as model substrates. The study also addresses the mechanism by which SSAO catalytic activity causes vascular damage, and further evaluates the contribution of SSAO in oxidative stress formation in the vascular wall. SSAO demonstrated higher affinity for aminoacetone when compared to methylamine (Km = 12.08 µM vs. 65.35 µM). Aminoacetone- and methylamine-induced VSMCs death at concentrations of 50 & 1000 µM, and their cytotoxic effect, was reversed with 100 µM of the irreversible SSAO inhibitor MDL72527, which completely abolished cell death. Cytotoxic effects were also observed after 24 h of exposure to formaldehyde, methylglyoxal and H2O2. Enhanced cytotoxicity was detected after the simultaneous addition of formaldehyde and H2O2, as well as methylglyoxal and H2O2. The highest ROS production was observed in aminoacetone- and benzylamine-treated cells. MDL72527 abolished ROS in benzylamine-, methylamine- and aminoacetone-treated cells (**** p < 0.0001), while βAPN demonstrated inhibitory potential only in benzylamine-treated cells (* p < 0.05). Treatment with benzylamine, methylamine and aminoacetone reduced the total GSH levels (**** p < 0.0001); the addition of MDL72527 and βAPN failed to reverse this effect. Overall, a cytotoxic consequence of SSAO catalytic activity was observed in cultured VSMCs where SSAO was identified as a key mediator in ROS formation. These findings could potentially associate SSAO activity with the early developing stages of atherosclerosis through oxidative stress formation and vascular damage.

The Biological Implication of Semicarbazide-Sensitive Amine Oxidase (SSAO) Upregulation in Rat Systemic Inflammatory Response under Simulated Aerospace Environment.

The progress of space science and technology has ushered in a new era for humanity's exploration of outer space. Recent studies have indicated that the aerospace special environment including microgravity and space radiation poses a significant risk to the health of astronauts, which involves multiple pathophysiological effects on the human body as well on tissues and organs. It has been an important research topic to study the molecular mechanism of body damage and further explore countermeasures against the physiological and pathological changes caused by the space environment. In this study, we used the rat model to study the biological effects of the tissue damage and related molecular pathway under either simulated microgravity or heavy ion radiation or combined stimulation. Our study disclosed that ureaplasma-sensitive amino oxidase (SSAO) upregulation is closely related to the systematic inflammatory response (IL-6, TNF-α) in rats under a simulated aerospace environment. In particular, the space environment leads to significant changes in the level of inflammatory genes in heart tissues, thus altering the expression and activity of SSAO and causing inflammatory responses. The detailed molecular mechanisms have been further validated in the genetic engineering cell line model. Overall, this work clearly shows the biological implication of SSAO upregulation in microgravity and radiation-mediated inflammatory response, providing a scientific basis or potential target for further in-depth investigation of the pathological damage and protection strategy under a space environment.

Semicarbazide-Sensitive Amine Oxidase (SSAO) and Lysyl Oxidase (LOX) Association in Rat Aortic Vascular Smooth Muscle Cells.

Vascular smooth muscle cells (VSMCs) are the main stromal cells in the medial layer of the vascular wall. These cells produce the extracellular matrix (ECM) and are involved in many pathological changes in the vascular wall. Semicarbazide-sensitive amine oxidase (SSAO) and lysyl oxidase (LOX) are vascular enzymes associated with the development of atherosclerosis. In the vascular smooth muscle cells, increased SSAO activity elevates reactive oxygen species (ROS) and induces VSMCs death; increased LOX induces chemotaxis through hydrogen peroxide dependent mechanisms; and decreased LOX contributes to endothelial dysfunction. This study investigates the relationship between SSAO and LOX in VSMCs by studying their activity, protein, and mRNA levels during VSMCs passaging and after silencing the LOX gene, while using their respective substrates and inhibitors. At the basal level, LOX activity decreased with passage and its protein expression was maintained between passages. βAPN abolished LOX activity (** p < 0.01 for 8 vs. 3 and * p < 0.05 for 5 vs. 8) and had no effect on LOX protein and mRNA levels. MDL72527 reduced LOX activity at passage 3 and 5 (##&nbsp;p < 0.01) and had no effect on LOX protein, and mRNA expression. At the basal level, SSAO activity also decreased with passage, and its protein expression was maintained between passages. MDL72527 abolished SSAO activity (****&nbsp;p < 0.0001 for 8 vs. 3 and * p < 0.05 for 5 vs. 8), VAP-1 expression at passage 5 (** p < 0.01) and 8 (**** p < 0.0001), and Aoc3 mRNA levels at passage 8 (* p < 0.05). βAPN inhibited SSAO activity (**** p < 0.0001 for 5 vs. 3 and 8 vs. 3 and * p < 0.05 for 5 vs. 8), VAP-1 expression at passage 3 (* p < 0.05), and Aoc3 mRNA levels at passage 3 (* p < 0.05). Knockdown of the LOX gene (**** p < 0.0001 for Si6 vs. Sictrl and *** p < 0.001 for Si8 vs. Sictrl) and LOX protein (** p < 0.01 for Si6 and Si8 vs. Sictrl) in VSMCs at passage 3 resulted in a reduction in Aoc3 mRNA (####&nbsp;p < 0.0001 for Si6 vs. Sictrl and ###&nbsp;p < 0.001 for Si8 vs. Sictrl) and VAP-1 protein (#&nbsp;p < 0.05 for Si8 vs. Sictrl). These novel findings demonstrate a passage dependent decrease in LOX activity and increase in SSAO activity in rat aortic VSMCs and show an association between both enzymes in early passage rat aortic VSMCs, where LOX was identified as a regulator of SSAO activity, protein, and mRNA expression.

Vascular adhesion protein-1 (VAP-1) in vascular inflammatory diseases.

Vascular adhesion protein-1 (VAP-1) also known as amino oxidase copper containing 3 (AOC3) is a pro-inflammatory and versatile molecule with adhesive and enzymatic properties. VAP-1 is a primary amine oxidase belonging to the semicarbazide-sensitive amine oxidase (SSAO) family, which catalyzes the oxidation of primary amines leading to the production of ammonium, formaldehyde, methylglyoxal, and hydrogen peroxide. VAP-1 is mainly expressed by endothelial cells, smooth muscle cells, adipocytes and pericytes. It is involved in a repertoire of biological functions, e.g., immune cell extravasation, angiogenesis, and vascularization. Research into VAP-1 has intensified within the last decade on its role as a novel clinical biomarker and as a potential therapeutic target of vascular inflammatory disorders such as atherosclerosis, stroke, diabetes, neurovascular disorders (e.g., Alzheimer's Disease), hepatic disease (e.g., non-alcoholic steatohepatitis), and skin conditions (e.g., psoriasis). This is the most up-to-date and comprehensive review on VAP-1 focusing on the translational aspects of VAP-1. Compared to recent reviews, our review provides novel insights on VAP-1 and heart failure, stroke and frailty, diabetes, endometriosis, osteoarthritis, COVID-19, conjunctivitis associated systemic lupus erythematosus, hematopoietic stem cells, gliomas, treatment of colorectal cancer with a novel VAP-1 inhibitor (U-V269), promoting recovery of motor functions and habit learning with a novel VAP-1 inhibitor (PXS-4681A), and 68Ga-DOTA-Siglec-9, a labelled peptide of Siglec-9 (a VAP-1 ligand), which appears to be a safe PET tracer for inflammation in rheumatoid arthritis. Finally, we present the emerging role of VAP-1 in pregnancy as a gatekeeper of immune cells, which are critical for spiral arterial remodeling, the deficiency of which could lead to vascular disorders of pregnancy such as preeclampsia. Future research should prioritize clinical trials on VAP-1 small-molecule inhibitors and monoclonal antibodies, thus, maximizing the potential of VAP-1 targeted therapy as well as research into sVAP-1 as a clinical biomarker of diseases and its prognosis.

Involvement of Cu-containing amine oxidases in the development of lung pathology in ovalbumin-induced bronchial asthma in guinea pigs

Bronchial asthma is developed as an immune response to allergen challenges accompanied by inflammation and fibrosis implicated in airway remodeling. To reveal the causative implication of Cu-containing amino oxidases semicarbazide-sensitive amine oxidase (SSAO), DAO and lysyl oxidase (LOX) in BA development we used their irreversible inhibitor semicarbazide and guinea pig model of BA induced by ovalbumin. Semicarbazide was introduced to asthmatic animals via drink or inhalation. At the 16th week after disease induction, the increase in the activity of pro-inflammatory SSAO and DAO in plasma (1.6 and 2 times, respectively) was observed. The introduction of semicarbazide to asthmatic animals via drink or inhalation significantly decreased activities of these enzymes compared to the untreated asthmatic animals. A considerable­ increase in IL-13 content and LOX activity in the lung tissue of asthmatic animals were observed that evidenced airway inflammation and pulmonary fibrosis development. The uptake of semicarbazide by guinea pigs with bronchial asthma led to normalization of LOX activity. Histological studies confirmed that semicarbazide attenuated morphopathological changes in the lungs of asthmatic animals. Thus, the data obtained indicate the direct participation of the studied enzymes in the progression of pathological processes in atopic bronchial asthma as well as the potential use of semicarbazide as a drug in complex anti-asthmatic therapy. Keywords: atopic bronchial asthma, histaminase/diamine oxidase, IL-13, lysyl oxidase, nitric oxide, semicarbazide, semicarbazide sensitive amine oxidase

Effects of Chemical Structures Interacting with Amine Oxidases on Glucose, Lipid and Hydrogen Peroxide Handling by Human Adipocytes.

Benzylamine is a natural molecule present in food and edible plants, capable of activating hexose uptake and inhibiting lipolysis in human fat cells. These effects are dependent on its oxidation by amine oxidases present in adipocytes, and on the subsequent hydrogen peroxide production, known to exhibit insulin-like actions. Virtually, other substrates interacting with such hydrogen peroxide-releasing enzymes potentially can modulate lipid accumulation in adipose tissue. Inhibition of such enzymes has also been reported to influence lipid deposition. We have therefore studied in human adipocytes the lipolytic and lipogenic activities of pharmacological entities designed to interact with amine oxidases highly expressed in this cell type: the semicarbazide-sensitive amine oxidase (SSAO also known as PrAO or VAP-1) and the monoamine oxidases (MAO). The results showed that SZV-2016 and SZV-2017 behaved as better substrates than benzylamine, releasing hydrogen peroxide once oxidized, and reproduced or even exceeded its insulin-like metabolic effects in fat cells. Additionally, several novel SSAO inhibitors, such as SZV-2007 and SZV-1398, have been evidenced and shown to inhibit benzylamine metabolic actions. Taken as a whole, our findings reinforce the list of molecules that influence the regulation of triacylglycerol assembly/breakdown, at least in vitro in human adipocytes. The novel compounds deserve deeper investigation of their mechanisms of interaction with SSAO or MAO, and constitute potential candidates for therapeutic use in obesity and diabetes.

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.

Combining monoamine oxidase B and semicarbazide-sensitive amine oxidase enzyme inhibition to address inflammatory disease

The discovery of a dual MAO-B/SSAO inhibitor PXS-5131 is reported. The compound offers a compact and rigid three-dimensional structure with superior selectivity over MAO-A. Potency and selectivity are linked to both the double bond geometry and stereochemistry of the allylamine moiety, highlighting the importance of optimal set up of these features in the class of amine oxidase inhibitors. PXS-5131 possesses an attractive preclinical pharmacokinetic profile and has anti-inflammatory properties in models of acute inflammation and neuroinflammation.

Multiple Direct Effects of the Dietary Protoalkaloid N-Methyltyramine in Human Adipocytes.

Dietary amines have been the subject of a novel interest in nutrition since the discovery of trace amine-associated receptors (TAARs), especially TAAR-1, which recognizes tyramine, phenethylamine, tryptamine, octopamine, N-methyltyramine (NMT), synephrine, amphetamine and related derivatives. Alongside the psychostimulant properties of TAAR-1 ligands, it is their ephedrine-like action on weight loss that drives their current consumption via dietary supplements advertised for ‘fat-burning’ properties. Among these trace amines, tyramine has recently been described, at high doses, to exhibit an antilipolytic action and activation of glucose transport in human adipocytes, i.e., effects that are facilitating lipid storage rather than mobilization. Because of its close structural similarity to tyramine, NMT actions on human adipocytes therefore must to be reevaluated. To this aim, we studied the lipolytic and antilipolytic properties of NMT together with its interplay with insulin stimulation of glucose transport along with amine oxidase activities in adipose cells obtained from women undergoing abdominal surgery. NMT activated 2-deoxyglucose uptake when incubated with freshly isolated adipocytes at 0.01–1 mM, reaching one-third of the maximal stimulation by insulin. However, when combined with insulin, NMT limited by half the action of the lipogenic hormone on glucose transport. The NMT-induced stimulation of hexose uptake was sensitive to inhibitors of monoamine oxidases (MAO) and of semicarbazide-sensitive amine oxidase (SSAO), as was the case for tyramine and benzylamine. All three amines inhibited isoprenaline-induced lipolysis to a greater extent than insulin, while they were poorly lipolytic on their own. All three amines—but not isoprenaline—interacted with MAO or SSAO. Due to these multiple effects on human adipocytes, NMT cannot be considered as a direct lipolytic agent, potentially able to improve lipid mobilization and fat oxidation in consumers of NMT-containing dietary supplements.

Investigation of Enzymes in the Phthalide Biosynthetic Pathway in Angelica sinensis Using Integrative Metabolite Profiles and Transcriptome Analysis.

The roots of Angelica sinensis (Oliv.) Diels are well known for their efficacy in promoting blood circulation. Although many studies have indicated that phthalides are the main chemical components responsible for the pharmacological properties of A. sinensis, the phthalide biosynthetic pathway and enzymes that transform different phthalides are still poorly understood. We identified 108 potential candidate isoforms for phthalide accumulation using transcriptome and metabolite profile analyses. Then, six enzymes, including phospho-2-dehydro-3-deoxyheptonate aldolase 2, shikimate dehydrogenase, primary amine oxidase, polyphenol oxidase, tyrosine decarboxylase, and shikimate O-hydroxycinnamoyl transferase, were identified and proven to be involved in phthalide accumulation by heterologously expressing these proteins in Escherichia coli. We proposed a possible mechanism underlying phthalide transformation and biosynthetic pathways in A. sinensis based on our findings. The results of our study can provide valuable information for understanding the mechanisms underlying phthalide accumulation and transformation and enable further development of quality control during the cultivation of A. sinensis.