Fig 1.
1) ad libitum (AL) group (N = 6) animals were not subjected to any intervention from arrival. 2) wheel running (WR) group (N = 8) animals were subjected to running wheel access from arrival to the end of the experiment. 3) food restriction (FR) group (N = 6) animals were subjected to 10-days adaptation, then received 40% of their baseline food intake until a 30% weight reduction was reached (acute FR). The body weight was then maintained for 2.5 weeks (chronic FR). 4) activity-based anorexia (ABA) group (N = 8) animals were subjected to running wheel access from arrival and weight reduction intervention similar to the FR group from day 11. Body weight, food intake, and running wheel activity (only in the WR and ABA groups) were measured daily from day 1 to 28 and every other day from day 28 to 34. The estrous cycle was measured in 4-day blocks from the start of the acute FR session. Spontaneous food intake was estimated at days 18 and 34. Blood collection was done on days 18 (via the tail vein) and 35 (via cardiac puncture).
Fig 2.
Time course of body weight (A) and cumulative food intake (B).
In the FR and ABA groups, 30% of the body weight was lost on day 10 due to food being given at only 40% the amount of the daily food intake in the adaptation period. After achievement of a 30% weight loss, the amount of food given was increased to 50% in order to maintain the target weight.
Fig 3.
Average body weight (A) and daily food intake (B) during three experimental sessions: Acclimatization (days 1 to 10), acute FR (days 11 to 17), and chronic FR (days 18 to 34).
In the FR and ABA groups, it is not surprising that the body weight and daily food intake were significantly lower than in the other two groups.
Fig 4.
Time course of running wheel activity in the light phase (A) and the dark phase (B).
In the ABA groups, a considerable increase in activity in the light phase and the relative decrease in the dark phase were found from day 14.
Fig 5.
Average running wheel activity in the light phase (A) and the dark phase (B) during three experimental sessions: Acclimatization (days 1 to 10), acute FR (days 11 to 17), and chronic FR (days 18 to 34).
In the ABA group, the activity in the light phase was significantly higher and the activity in dark phase was significantly lower than that of the WR group during acute and chronic FR sessions.
Fig 6.
Time course of incidence of estrous cycle in 4-days blocks from the acute FR session.
In the FR and ABA groups, no estrous cycle was found after the second block.
Table 1.
Comparisons of incidence of estrous cycle of four experimental groups in 4-days blocks.
Fig 7.
Time course of spontaneous food intake at days 18 (A) and 34 (B).
At the end of the acute FR session, no significant difference was found between the FR and ABA groups. At the end of the chronic FR session, some spontaneous food restriction was observed in the ABA group.
Fig 8.
Plasma adiponectin levels at days 18 and 35.
There was a trend toward differences among the four groups at the end of the acute FR session. At the end of chronic FR phase, the concentration was significantly higher in the FR and ABA groups than in the AL and WR groups. Circulating adiponectin tended to be lower in the ABA group than in the FR group.