Protein Level in a Meal Influences Novel Object Recognition in Exercise‐Trained Rats

Exercise and breakfast have positive effects on learning and memory; however, little is known of the acute effect of breakfast composition. The objective of the presented study was to evaluate the effect of protein level in a meal equivalent to breakfast on a memory task in exercise‐trained rats. Adolescent male Spraque‐Dawley rats were assigned to a 6‐week exercise program (n=18) on a motorized treadmill or a sedentary control group (n=18). Exercise duration was increased to 60 min and intensity to 30 m/min at a 10.5% grade over a 4‐week period. Throughout the study, rats were on a feeding schedule consisting of a 30 min meal (20% of daily calories) provided 60 min into the dark period and ad libitum access to rodent chow the last 5 hrs of the dark period. At the end of training week 5, rats were randomly fed a 4g breakfast meal of high casein (50% by calories; HC) or low casein (15% by calories; LC) diets and tested using a Novel Object Recognition task 60 min later. The task consisted of a 5 min acquisition phase followed by a 5 min testing phase 60 min later. Rats spending less than 30 sec exploring objects during either phase or exhibiting clear location preference (≥70% of time on one object during acquisition phase) were removed from the study. Results were evaluated using two‐way ANOVA and paired t‐test. All rats consumed their entire ration of diet during the breakfast meal. During the acquisition phase rats spent approximately 50% of time exploring each of the two objects. During the testing phase, there was no significant effect of exercise‐training (p=0.91); however, there were significant effects of protein level (p=0.02) and the interaction between protein level and training (p=0.05). In the sedentary group, rats fed either the LC or HC diet spent 64% (p=0.05) or 66% (p=0.02) of time exploring the novel object, respectively. In the trained group, rats fed the LC spent 57% (p=0.15) of time exploring the novel object vs 73% (p<0.005) by HC‐fed rats. Total time exploring objects was longer during the testing phase than the acquisition phase (71 +/− 3 sec vs 61 +/− 3 sec, p=0.01). The level of protein in a meal immediately prior to a learning task had a greater influence on learning by exercise‐trained than sedentary rats. There seemed little benefit of a higher protein meal on the memory task in sedentary rats. However, the low protein meal reduced performance while the high protein meal increased performance on the recognition task in the trained rats (vs sedentary controls). These results support the importance of dietary protein intake prior to cognitive tasks in exercise‐trained individuals. Support or Funding Information Supported by UNCG Faculty First Grant and School of Health and Human Sciences Research Excellence Grant