Hypercaloric cafeteria-like diet induced UCP3 gene expression in skeletal muscle is impaired by hypothyroidism

Abstract

The uncoupling protein UCP3 belongs to a family of mitochondrial carriers located in the inner mitochondrial membrane of certain cell types. It is expressed almost exclusively at high levels in skeletal muscle and its physiological role has not been fully determined in this tissue. In the present study we have addressed the possible interaction between a hypercaloric diet and thyroid hormone (T 3 ), which are strong stimulators of UCP3 gene expression in skeletal muscle. Male Wistar rats weighing 180 ± 20 g were rendered hypothyroid by thyroidectomy and the addition of methimazole (0.05%; w/v) to drinking water after surgery. The rats were fed a hypercaloric cafeteria diet (68% carbohydrates, 13% protein and 18% lipids) for 10 days and sacrificed by decapitation. Subsequently, the gastrocnemius muscle was dissected, total RNA was isolated with Trizol™ and UCP3 gene expression was determined by Northern blotting using a specific probe. Statistical analysis was performed by one-way analysis of variance (ANOVA) followed by the Student-Newman-Keuls posttest. Skeletal muscle UCP3 gene expression was decreased by 60% in hypothyroid rats and UCP3 mRNA expression was increased 70% in euthyroid cafeteria-fed rats compared to euthyroid chow-fed animals, confirming previous studies. Interestingly, the cafeteria diet was unable to stimulate UCP3 gene expression in hypothyroid animals (40% lower as compared to euthyroid cafeteria-fed animals). The results show that a hypercaloric diet is a strong stimulator of UCP3 gene expression in skeletal muscle and requires T 3 for an adequate action.

Influência das Dietas Hipercalóricas sobre os Parâmetros de Obesidade, Dislipidemia e Hiperglicemia em Ratos

“…A Dieta Plus se constitui de 27% de proteína, 43% de carboidrato, 20% de lipídio e 10% de outras substâncias, apresentando 4, 6 Kcal (SILVA et al, 2008;NASCIMENTO, 2006). A Dieta Cafeteria, no entanto, tem-se a proposta de 13% de proteínas, 68% de carboidratos e 18% de lipídios, computando valores calóricos de 4,875 Kcal, 3,975 Kcal, 3,6 Kcal, 5,075 Kcal e 3,8 Kcal, como segue a sequência dos cinco dias das dietas cafeterias (CHRISTOFFOLETE; MORISCOT, 2004).…”

Effect of body weight in the pathogenesis of ligature-induced periodontal disease in Wistar rats

“…Concerning obesity, induction can be by a fatrich diet [30] or by use of the so-called ''cafeteria diet'' as complement [13,14].…”

“…The animals were randomly assigned into two groups as follows: a test group given a calorie-rich diet (a ''cafeteria diet'' consisting of chocolate cookies and fat cheese) [13,14] for 4 months (day 0 to day 120) before being submitted to ligatureinduced periodontal disease for 30 days (day 120Á 150), (n 014); and a control group given standard rat chew pellets (Nuvilab † , Curtiba, Brazil) for 4 months (days 0Á120) prior to induction of periodontal disease by means of ligatures, from day 120 to day 150 (n 016). Water was available to both groups ad libitum.…”

Memory of long-term cold acclimation in deacclimated Wistar rats

“…This protein is suggested to export fatty acids outside the mitochondrial matrix for combustion in tissues where fat is the main fuel (Schrauwen and Hesselink, 2004). A hypercaloric diet, obesity and fasting induce UCP3 gene expression in skeletal muscle (Christoffolete and Moriscot, 2004;Abu-Elheiga et al, 2003;Rodriguez et al, 2003;Pilegaard et al, 2003). The physiological role of mammalian UCP3 and UCP2 is thought to be in lipid oxidation and/or prevention of (ROS) accumulation rather than heat production by uncoupling.…”