White adipose tissue as endocrine organ and its role in obesity.

Due to the public health problem represented by obesity, the study of adipose tissue, particularly of the adipocyte, is central to the understanding of metabolic abnormalities associated with the development of obesity. The concept of adipocyte as endocrine and functional cell is not totally understood and can be currently defined as the capacity of the adipocyte to sense, manage, and send signals to maintain energy equilibrium in the body. Adipocyte functionality is lost during obesity and has been related to adipocyte hypertrophy, disequilibrium between lipogenesis and lipolysis, impaired transcriptional regulation of the key factors that control adipogenesis, and lack of sensitivity to external signals, as well as a failure in the signal transduction process. Thus, dysfunctional adipocytes contribute to abnormal utilization of fatty acids causing lipotoxicity in non-adipose tissue such as liver, pancreas and heart, among others. To understand the metabolism of the adipocyte it is necessary to have an overview of the developmental process of new adipocytes, regulation of adipogenesis, lipogenesis and lipolysis, endocrine function of adipocytes and metabolic consequences of its dysfunction. Finally, the key role of adipose tissue is shown by studies in transgenic animals or in animal models of diet-induced obesity that indicate the contribution of adipose tissue during the development of metabolic syndrome. Thus, understanding of the molecular process that occurs in the adipocyte will provide new tools for the treatment of metabolic abnormalities during obesity.

[Vitamin C decreases MMP-9 synthesis induced by hydrogen peroxide in an in vitro chorioamniotic membrane model]. / La vitamina C disminuye la síntesis de MMP-9 inducida con peróxido de hidrógeno en un modelo de estudio in vitro de membranas corioamnióticas.

OBJECTIVE: To evaluate the hydrogen peroxide ability to induce the synthesis of matrix metalloproteinase-9 (MMP-9) in an in vitro chorioamniotic membrane model. MATERIAL AND METHODS: An experimental, transversal, analytic and prospective study was made. From amniotic membranes (n = 13) of term labour pregnant women chorionic and chorioamniotic explants were prepared; these were stimulated with hydrogen peroxide [200 mcM]. A group of explants were cultured with vitamin C, 48 hours prior to the hydrogen peroxide stimulus. Twenty-four hours after hydrogen peroxide stimulus the supernatants were collected and metalloproteinase-9 production was determined by zymography methods. RESULTS: Hydrogen peroxide induced the synthesis of metalloproteinase-9 in chorionic and chorioamniotic membranes. When chorionic and chorioamniotic membranes were cultured with vitamin C prior to the hydrogen peroxide stimulus, the MMP-9 production diminished (p < 0.05; Dunn's method). CONCLUSIONS: Hydrogen peroxide induced the synthesis of metalloproteinase-9 in chorionic and chorioamniotic membranes. When chorionic and chorioamniotic membranes were cultured with vitamin C, 48 hours prior to peroxide hydrogen stimulus, the metalloproteinase-9 production diminished with statistical significance.