Alteration of amine oxidase activity in the adipose tissue of obese subjects.
OBJECTIVE
To explore the activity of monoamine oxidases (MAOs) and semicarbazide-sensitive amine oxidases (SSAOs) in adipose tissue and blood of lean and moderately obese subjects and to study whether there is a link between these hydrogen peroxide-generating enzymes and blood markers of oxidative stress.


METHODS
Nine obese male subjects (BMI 32.6 +/- 0.4 kg/m(2)) and nine controls (BMI 23.4 +/- 0.5) of 24- to 40-year-old subjects were included in the study. MAO and SSAO activities were measured on microbiopsies of abdominal subcutaneous adipose tissue by quantifying (14)C-tyramine and (14)C-benzylamine oxidation. Levels of soluble SSAO, lipid peroxidation products, and antioxidant agents were measured in plasma, whereas cytoprotective enzymes were determined in blood lysates.


RESULTS
The high MAO activity found in adipose tissue was diminished by one-half in obese subjects (maximum initial velocity of 1.2 vs. 2.3 nmol tyramine oxidized/mg protein/min). There was no change in SSAO activity, either under its adipose tissue-bound or plasma-soluble form. Plasma levels of lipid peroxidation products and antioxidant vitamins remained unmodified, as well as erythrocyte antioxidant enzymes, whereas circulating triglycerides, insulin, and leptin were increased.


CONCLUSIONS
Although they already exhibited several signs of endocrino-metabolic disorders, the obese men did not exhibit the increase in blood markers of oxidative stress or the decrease in antioxidant defenses reported to occur in very obese or diabetic subjects. The reduced MAO and the unchanged SSAO activities found in obesity suggest that these hydrogen peroxide-generating enzymes expressed in adipocytes are probably not involved in the onset of the oxidative stress found in severe obesity and/or in its complications.
Visentin
Virgile
V
Institut National de la Santé et de la Recherche Médicale, Centre Hospitalier Universitaire Rangueil, Toulouse, France.
Prévot
Danielle
D
De Saint Front
Véronique Durand
VD
Morin-Cussac
Nathalie
N
Thalamas
Claire
C
Galitzky
Jean
J
Valet
Philippe
P
Zorzano
Antonio
A
Carpéné
Christian
C
D000005:Abdomen; D000273:Adipose Tissue / Q000201:enzymology*; D000328:Adult; D006631:Amine Oxidase (Copper-Containing) / Q000097:blood / Q000378:metabolism*; D000975:Antioxidants / Q000032:analysis; D001596:Benzylamines / Q000378:metabolism; D001706:Biopsy; D015992:Body Mass Index; D002250:Carbon Radioisotopes; D004912:Erythrocytes / Q000201:enzymology; D006801:Humans; D015227:Lipid Peroxidation; D008297:Male; D008995:Monoamine Oxidase / Q000097:blood / Q000378:metabolism*; D009765:Obesity / Q000201:enzymology*; D010084:Oxidation-Reduction; D014439:Tyramine / Q000378:metabolism
D000975:Antioxidants; D001596:Benzylamines; D002250:Carbon Radioisotopes; C030796:benzylamine; D006631:Amine Oxidase (Copper-Containing); D008995:Monoamine Oxidase; D014439:Tyramine