Influence of long-term obesity on myocardial gene expression

Abstract

Background: Several authors have shown that deterioration of cardiac function is associated with the degree and duration of obesity. It is necessary to establish the gene expression patterns after prolonged periods of obesity. Objective: This study tested the hypothesis that increased duration of exposure to obesity leads to a reduction in the mRNA levels of proteins involved in regulation of myocardial Ca2++ homeostasis. In addition, this study verified whether the decrease in mRNA expression was caused by a reduction in thyroid hormone. Methods: Thirty-day-old male Wistar rats were distributed in two groups: control (C) and obese (Ob). The C group was fed a standard diet and the Ob was fed with high-fat diets for 15, 30 and 45 weeks. Obesity was defined by adiposity index. The gene expression was assessed by quantitative real-time PCR. Results: The adiposity index was higher in the Ob compared to the C after all periods. While obesity at 15 and 45 weeks resulted in a reduction in mRNA of sarcoplasmic reticulum Ca2+-ATPase (SERCA2a), Na+/Ca2+ exchanger (NCX), and calsequestrin (CSQ), L-type Ca2+ channels, ryanodine receptor, SERCA2a, phospholamban (PLB), NCX, and CSQ expression were increased compared to the C after 30 weeks. There was no significant association between T3 levels and mRNA expression. Conclusions: Our data indicate that obesity over the short and long periods of time may promote alteration in gene expression of Ca2+ homeostasis regulatory proteins without influence by thyroid hormone.