Caloric restriction alters galanin and its receptor in hypothalamus of wistar rats

Caloric restriction (CR) reverses obesity and insulin resistance, yet the detailed mechanism underlying its beneficial effects is poorly understood. The galanin system is closely associated with energy metabolism. It is yet unclear whether this effect of CR is operating through the regulation of the galanin system. To test this effect, we subjected rats to either 60% or 40% calorie restriction for one week. After the one-week's experiment, galanin and many genes associated with the function of metabolism were examined. The present findings showed that 7 days of 60% or 40% calorie restriction lowered body weight and plasma glucose concentration in rats, suggesting that rats under CR have improved weight loss and systemic glucose metabolism. Besides, the lower plasma glucose was associated with an increase in muscle glucose uptake resulting from elevations of both glucose transporter 4 (GLUT4) and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression in skeletal muscles. Moreover, the levels of galanin and its receptors (GALR1-3) mRNA markedly increased in the hypothalamus of CR rats. Taken together, these results supported that non-pharmacological activation of the galanin/GALR signaling with CR regimen led to activation of the PGC-1α/GLUT4 axis in skeletal muscles which can enhance energy metabolism. The current findings provide additional evidence that galanin is a critical factor for CR-induced weight loss and metabolic changes. CR regimen may be recognized as a non-pharmacological intervention that could prevent obesity and its associated metabolic disorders.