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.


METHODS
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 ( approximately 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<0.01) decrease in liver and muscle glycogen content. Plasma free fatty acid and glycerol concentrations were increased (P<0.01) similarly in all three groups during exercise. In a separate experiment conducted in isolated hepatocytes from 24 h fasted Lou/C and Wistar rats, it was found that gluconeogenic flux from glycerol was found to be significantly (P<0.01) higher in Lou/C than in Wistar rats (5.4+/-0.2 vs 3.7+/-0.1 micromol/min/g dry cells). Resting and exercising plasma leptin levels were also significantly (P<0.05) lower in Lou/C than in the two other groups.


CONCLUSIONS
It is concluded that Lou/C rats have the particularity to rely spontaneously less on their liver glycogen stores to meet their energy demands during exercise while maintaining euglycemia.
Couturier
K
K
UMR 5123 CNRS, Laboratoire de Physiologie, Université Claude Bernard, Lyon, France.
Servais
S
S
Koubi
H
H
Sempore
B
B
Cottet-Emard
J-M
JM
Guigas
B
B
Lavoie
J-M
JM
Favier
R
R
D020155:3-Hydroxybutyric Acid / Q000032:analysis; D000818:Animals; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism*; D031204:Caloric Restriction; D005230:Fatty Acids, Nonesterified / Q000032:analysis; D005990:Glycerol / Q000097:blood; D006003:Glycogen / Q000032:analysis; D006706:Homeostasis; D008099:Liver / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D009765:Obesity / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D006003:Glycogen; D005990:Glycerol; D020155:3-Hydroxybutyric Acid