Metabolic and hormonal responses to exercise in the anti-obese Lou C rats

OBJECTIVE: Lou/C rats are a substrain of Wistar rats that exhibit a spontaneous low caloric intake and no development of obesity with age. Recently, we reported that Lou/C rats, compared to equally food-restricted Wistar counterparts, show lower resting levels of plasma glucose, epinephrine and liver glycogen. To further explore this metabolic particularity, we used exercise (swimming 60 min) as a situation of high-energy demand, to test the ability of Lou/C rats to maintain euglycemia. DESIGN: Male Lou/C rats (14-week-old) were compared to age-matched male Wistar rats fed either ad libitum (WAL) or Wistar rats whose food was chronically restricted (WFR) to the same caloric intake as the Lou/C rats. RESULTS: In spite of low liver glycogen stores (∼50% of normal values), Lou/C rats were able to maintain euglycemia during exercise even though liver glycogen breakdown was blunted. The decreased use of glycogen during exercise in Lou/C rats was associated with a reduced epinephrine response compared to WFR animals. By contrast, WFR were also able to maintain euglycemia during exercise but at the expense of a significant ( P