Regulation of skeletal muscle UCP-2 and UCP-3 gene expression by exercise and denervation

Abstract

The factors that regulate gene expression of uncoupling proteins 2 and 3 (UCP-2 and UCP-3) in skeletal muscle are poorly understood, but both genes are clearly responsive to the metabolic state of the organism. Therefore, we tested the hypothesis that denervation and acute and/or chronic exercise (factors that profoundly affect metabolism) would alter UCP-2 and UCP-3 gene expression. For the denervation studies, the sciatic nerve of rat and mouse hindlimb was sectioned in one leg while the contralateral limb served as control. Northern blot analysis revealed that denervation was associated with a 331% increase ( P < 0.001) in UCP-3 mRNA and a 200% increase ( P < 0.01) in UCP-2 mRNA levels in rat mixed gastrocnemius (MG) muscle. In contrast, denervation caused a 53% decrease ( P< 0.001) in UCP-3 and a 63% increase ( P < 0.01) in UCP-2 mRNA levels in mouse MG. After acute exercise (2-h treadmill running), rat UCP-3 mRNA levels were elevated (vs. sedentary control) 252% ( P < 0.0001) in white gastrocnemius and 63% ( P < 0.05) in red gastrocnemius muscles, whereas UCP-2 levels were unaffected. To a lesser extent, elevations in UCP-3 mRNA (22%; P < 0.01) and UCP-2 mRNA (55%; P < 0.01) levels were observed after acute exercise in the mouse MG. There were no changes in either UCP-2 or UCP-3 mRNA levels after chronic exercise (9 wk of wheel running). These results indicate that acute exercise and denervation regulate gene expression of skeletal muscle UCPs.

Effects of green tea on insulin sensitivity, lipid profile and expression of PPARα and PPARγ and their target genes in obese dogs

“…An elevation of the expression of PPARg, LPL and GLUT4 in adipose tissue, without any effect on plasma NEFA concentration, would enhance fat depots -similar to thiazolidinedione (49) . An increase in uncoupling protein activity in adipose tissue might regulate the energy balance by uncoupling mitochondrial respiration -as has been shown with thiazolidinedione (50) . Some reports suggested that green tea catechins not only promote energy expenditure but also stimulate the oxidation of lipids by the known inhibitory effect of catechins and notably EGCG on catechol-Omethyltransferase, an enzyme that degrades noradrenaline (51) .…”

Changes in UCP mRNA expression levels in brown adipose tissue and skeletal muscle after feeding a high-energy diet and relationships with leptin, glucose and PPARγ

“…A number of studies have been carried out under different situations showing that both muscle UCPs are similarly regulated, but UCP3 seemed to be much more sensitive to changes. Thus, leptin [40], fasting [2] and exercise [41] increase expression of both proteins, whereas refeeding after fasting [2] and ␤ 3 adrenergic agonist administration [10] decrease their levels. Our results showed a significant increase in mRNA UCP3 levels in animals fed a high-calorie diet, and are in accordance with previous data [7,15].…”

The uncoupling protein homologues: UCP1, UCP2, UCP3, StUCP and AtUCP

“…Increased expression of UCP3 and UCP2 mRNA levels was observed in muscles of exercised mice 0-3 h after the end of the last bout of exercise, under conditions where GLUT4 levels and insulin-induced glucose uptake are increased [245,246]. Conversely, 20-30 h after cessation of the last bout of exercise, when the insulin-induced glucose uptake has returned to its basal value, no increase in UCP3 or UCP2 mRNA was observed [245,247].…”