Plasma semicarbazide-sensitive amine oxidase is moderately decreased by pronounced exogenous hyperinsulinemia but is not associated with insulin sensitivity and body fat

Anatomical distribution of primary amine oxidase activity in four adipose depots and plasma of severely obese women with or without a dysmetabolic profile

Semicarbazide-sensitive amine oxidase (SSAO), identical to primary amine oxidase or vascular adhesion protein-1, is a membrane enzyme that generates hydrogen peroxide. SSAO is highly expressed at the adipocyte surface, and its plasma levels increase with type 2 diabetes. Since visceral adipose tissue (AT) is more tightly associated with obesity complications than subcutaneous (SC) abdominal fat, we compared SSAO activity in plasma and 4 distinct AT locations in 48 severely obese women (body mass index (BMI), averaging 54 ± 11 kg/m²), with or without a dysmetabolic profile. Higher glucose and triacylglycerol levels vs lower high-density lipoprotein (HDL)-cholesterol characterized dysmetabolic women (DYS; n = 25) from non-dysmetabolic (NDYS; n = 23), age- and weight-matched subjects. SC, mesenteric (ME), omental (OM), and round ligament (RL) fat locations were collected during bariatric surgery. SSAO capacity to oxidize up to 1 mM benzylamine was determined in AT and plasma with radiometric and fluorimetric methods. Plasma SSAO was higher in the DYS group. SSAO activity was higher in fat than in plasma, when expressed as radiolabeled benzaldehyde per milligram of protein. In ATs from DYS women, protein content was 10 % higher, and basal hydrogen peroxide release lower than in NDYS subjects, except for RL location. The SSAO affinity towards benzylamine did not exhibit regional variation and was not altered by a dysmetabolic profile (K _m averaging 184 ± 7 μM; n = 183). Although radiometric and fluorimetric methods gave different estimates of oxidase activity, both indicated that AT SSAO activity did not vary according to anatomical location and/or metabolic status in severely obese women.

Soluble vascular adhesion protein-1 correlates with cardiovascular risk factors and early atherosclerotic manifestations

OBJECTIVE

Vascular adhesion protein-1 is an endothelial enzyme that regulates leukocyte traffic and contributes to vascular damage in animal models. The relations of soluble vascular adhesion protein-1 (sVAP-1) with cardiovascular risk factors and markers of subclinical atherosclerosis at a population level have not been studied.

METHODS AND RESULTS

We developed a new high-throughput method and measured sVAP-1 activities in serum of 2183 persons (The Cardiovascular Risk in Young Finns Study). In women, sVAP-1 activity correlated indirectly with body mass index (r=-0.15, P<0.0001), triglycerides (r=-0.13, P<0.0001), C-reactive protein (r=-0.23; P<0.0001), and brachial artery flow-mediated vasodilatation (r=-0.076, P=0.0089) and directly with carotid plaques (r=0.066, P=0.023). None of these correlations was significant in men. In women, all these univariate correlations remained significant after adjustment for body mass index, and direct correlations with LDL-cholesterol (r=0.094, P=0.0014) and carotid intima-media thickness (r=0.075, P=0.010) became evident. In men, sVAP-1 activity associated directly with glucose (r=0.074, P=0.020), intima-media thickness (r=0.072, P=0.025), metabolic syndrome (P=0.016), and type 1 (P=0.0002) and type 2 (P<0.0001) diabetes. In multivariable analyses, sVAP-1 activity was an independent determinant of carotid intima-media thickness (P=0.0072) and plaques [odds ratio 1.71 (95% confidence interval 1.07-2.72, P=0.025] in women, but not in men.

CONCLUSIONS

sVAP-1 activity correlates directly with intima-media thickness and carotid plaques in general population and may play a role in the pathophysiology of preclinical atherosclerosis.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1: a patent survey

INTRODUCTION

Vascular adhesion protein-1 (VAP-1)/semicarbazide-sensitive amine oxidase (SSAO) is an adhesion protein involved in leukocyte trafficking and inflammatory processes, with a special amine oxidase activity. Inhibitors have been mainly developed for treating chronic inflammatory disorders. The utility of inhibitors as antiangiogenic agents in ophthalmological and oncological diseases is currently under evaluation. SSAO substrates may mimic several insulin effects, although their utility for the treatment of diabetes is still far from being fully understood.

AREAS COVERED

This paper reviews the patent literature of SSAO/VAP-1 inhibitors and substrates, for the period of 1990 - 2010. The current stage of SSAO/VAP-1-interacting agents published in patents is described, along with their chemical structures and pharmacological uses.

EXPERT OPINION

SSAO/VAP-1 is a promising anti-inflammatory target. Another important field for therapeutic application of these inhibitors may be ophthalmology, due to their antiangiogenic effects. SSAO substrates might also be of therapeutic value in the treatment of diabetes; however, more extensive research has to be undertaken to validate this approach.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 deficiency reduces leukocyte infiltration into adipose tissue and favors fat deposition

Obesity is associated with low-grade inflammation and leukocyte infiltration in white adipose tissue (WAT) and is linked to diabetic complications. Semicarbazide-sensitive amine oxidase, also known as vascular adhesion protein-1 (SSAO/VAP-1), is a membrane protein that is highly expressed in adipocytes and is also present on the endothelial cell surface where it is involved in leukocyte extravasation. We studied fat deposition and leukocyte infiltration in WAT of mice with a null mutation in the amine oxidase copper-containing-3 (AOC3) gene encoding SSAO/VAP-1. Both epididymal and inguinal WATs were larger in 6-month-old AOC3-KO males than in age-matched wild-type controls. However, WAT from AOC3-KO mice contained lower CD45 mRNA levels and fewer CD45(+) leukocytes. Subpopulation analyses revealed a diminished infiltration of WAT by T cells, macrophages, natural killer, and natural killer T cells. A decrease in leukocyte content in WAT was also detected in female AOC3-KO mice as early as 2 months of age, whereas increased fat mass was evident by 6 months of age. Reduced CD45(+) populations in WAT of AOC3-KO mice was not rescued by human SSAO/VAP-1 expression on adipocytes under the control of aP2, suggesting the importance of vascular AOC3 in leukocyte entrance into fat. Our results indicate that SSAO/VAP-1 is instrumental for the presence of leukocytes in WAT. Therefore, AOC3-KO mice present a unique model of mild obesity, characterized by increased WAT devoid of low-grade inflammation.

Decreased serum activity of semicarbazide-sensitive amine oxidase (SSAO) in patients treated with second generation antipsychotics: a link to impaired glucose metabolism?

OBJECTIVE

Although the treatment of schizophrenia with many second generation antipsychotics is known to be associated with metabolic changes, such as hyperglycemia or hypercholesterolemia, the underlying mechanisms of these adverse reactions remain unclear. In light of the recent focus on the involvement of semicarbazide-sensitive amine oxidase (SSAO) in glucose metabolism, we investigated SSAO serum activity in schizophrenic patients treated with antipsychotics with the objective of determining a possible link between SSAO and impaired glucose metabolism.

METHODS

Blood samples were drawn from 44 schizophrenic patients (24 receiving second generation antipsychotics known to disturb glucose metabolism) on day 1 and day 5 of inpatient treatment. Forty-one healthy adults with no medical condition known to influence SSAO served as controls.

RESULTS

Of the 44 schizophrenic patients, the 24 treated with second generation antipsychotics known to disturb glucose metabolism showed significantly lower SSAO serum activity [day 1 (mean +/- SD): 477 +/- 105 mU/L; day 5: 438 +/- 86 mU/L] than the 20 patients treated with other antipsychotics not known to influence glucose metabolism (day 1: 513 +/- 124 mU/L, p = 0.359; day 5: 542 +/- 204 mU/L, p = 0.021) only after 5 days of treatment and compared to healthy controls (526 +/- 142 mU/L, p = 0.021). No differences were observed between schizophrenic patients treated with first generation antipsychotics and the controls.

CONCLUSION

We found decreased SSAO serum activity exclusively in schizophrenic patients treated with second generation antipsychotics known to disturb glucose metabolism. In terms of the role of SSAO in glucose metabolism, the observed decrease in SSAO serum activity may be linked to metabolic changes that are known to occur in schizophrenic patients being treated with many second generation antipsychotics.