Figure 2
Open field and novel object. (A) All groups showed spatial habituation learning and moved less on day 2 than day 1 in the open field. ****p < 0.001 (ANOVA). Activity levels were lower in mice on a HFD than STD. ****p < 0.001 (ANOVA). (B) Mice on a HFD spent less time in the center of the open field than mice on a STD. ****p < 0.001 (ANOVA). (C) Mice on a HFD had lower activity levels than mice on a STD in the open field containing two identical objects on the object recognition training day. ****p < 0.001 (ANOVA). (D) Mice moved more in the open field containing two identical objects than on the previous day in the open field without object. ****p < 0.001 (ANOVA). There was also a diet × day interaction (F(1,95) = 14.182, ****p < 0.001 (ANOVA)). Mice on a STD showed a relatively larger increase in activity levels when two identical objects were introduced in the open field than mice on a HFD. (E) Mice on a HFD moved less than mice on a STD on the novel object recognition testing day. ****p < 0.001 (ANOVA). (F) In the object recognition test, E3 mice on a STD, treated with saline or insulin showed object recognition and spent more time exploring the novel than familiar object. *p < 0.05 versus the familiar object (paired t test). E3 and E4 mice on a HFD treated with saline spent a similar time exploring the two objects. However, E3 and E4 mice on a HFD treated with insulin and E4 mice on a STD treated with saline showed a trend towards exploring the novel object more than the familiar object. #p = 0.0586 (paired t test). HFD: high fat diet; STD: standard diet. E3 males: n = 9 HFD and n = 12 STD; E3 females: n = 19 HFD and n = 13 STD; E4 males: n = 7 HFD and n = 11 STD; E4 females: n = 15 HFD and n = 14 STD.
