Synergistic effects of diet and exercise on hippocampal function in chronically stressed mice.

Severe chronic stress can have a profoundly negative impact on the brain, affecting plasticity, neurogenesis, memory and mood. On the other hand, there are factors that upregulate neurogenesis, which include dietary antioxidants and physical activity. These factors are associated with biochemical processes that are also altered in age-related cognitive decline and dementia, such as neurotrophin expression, oxidative stress and inflammation. We exposed mice to an unpredictable series of stressors or left them undisturbed (controls). Subsets of stressed and control mice were concurrently given (1) no additional treatment, (2) a complex dietary supplement (CDS) designed to ameliorate inflammation, oxidative stress, mitochondrial dysfunction, insulin resistance and membrane integrity, (3) a running wheel in each of their home cages that permitted them to exercise, or (4) both the CDS and the running wheel for exercise. Four weeks of unpredictable stress reduced the animals' preference for saccharin, increased their adrenal weights and abolished the exercise-induced upregulation of neurogenesis that was observed in non-stressed animals. Unexpectedly, stress did not reduce hippocampal size, brain-derived neurotrophic factor (BDNF), or neurogenesis. The combination of dietary supplementation and exercise had multiple beneficial effects, as reflected in the number of doublecortin (DCX)-positive immature neurons in the dentate gyrus (DG), the sectional area of the DG and hippocampal CA1, as well as increased hippocampal BDNF messenger ribonucleic acid (mRNA) and serum vascular endothelial growth factor (VEGF) levels. In contrast, these benefits were not observed in chronically stressed animals exposed to either dietary supplementation or exercise alone. These findings could have important clinical implications for those suffering from chronic stress-related disorders such as major depression.

Attenuation of mania-like behavior in Na(+),K(+)-ATPase α3 mutant mice by prospective therapies for bipolar disorder: melatonin and exercise.

Bipolar disorder is a neuropsychiatric disease characterized by states of mania with or without depression. Pharmacological treatments can be inadequate at regulating mood for many individuals. Melatonin therapy and aerobic exercise are independent prospective therapies for bipolar disorder that have shown potential as mood stabilizers in humans. Myshkin mice (Myk/+) carry a heterozygous missense mutation in the neuronal Na(+),K(+)-ATPase α3 and model mania-related symptoms of bipolar disorder including increased activity, risk-taking behavior and reductions in sleep. One cohort of Myk/+ and wild-type littermates (+/+) was treated with melatonin and a separate cohort was treated with voluntary exercise. Mania-related behavior was assessed in both cohorts. The effect of melatonin on sleep and the effect of exercise on brain-derived neurotrophic factor (BDNF) expression in the hippocampus were assayed. Melatonin and voluntary wheel running were both effective at reducing mania-related behavior in Myk/+ but did not affect behavior in +/+. Melatonin increased sleep in Myk/+ and did not change sleep in +/+. Myk/+ showed higher baseline levels of BDNF protein in the hippocampus than +/+. Exercise increased BDNF protein in +/+ hippocampus, while it did not significantly affect BDNF levels in Myk/+ hippocampus. These findings support initial studies in humans indicating that melatonin and exercise are useful independent adjunct therapies for bipolar disorder. Their effects on mood regulation should be further examined in randomized clinical trials. Our results also suggest that hippocampal BDNF may not mediate the effects of exercise on mania-related behavior in the Myk/+ model of mania.