Successful brain aging: plasticity, environmental enrichment, and lifestyle

• MD Francisco Mora• Dialogues Clinical Neuroscience 2013 March

• University of Iowa Carver College of Medicine.

Abstract

• Aging is a physiological process that can develop without the appearance of concurrent diseases. However, older people suffer from memory loss and cognitive decline. Studies of the neurobiology of aging are beginning to decipher the mechanisms behind the physiology of aging of the brain but also the mechanisms that make people more vulnerable to cognitive neurodegenerative diseases. Today we know that the aging brain retains a functional plasticity, which is positively promoted by genes activated by different lifestyle factors. In this article these lfactors and their mechanisms of action are reviewed, including environmental enrichment and the importance of food intake and some nutrients. Aerobic physical exercise and reduction of chronic stress are also briefly reviewed. It is proposed that lifestyle factors promote healthy and successful aging of the brain.

INTRODUCTION

• Aging of the brain is a very complex biological process associated with decline in sensory, motor, and cognitive functions. However, aging is not a disease

• Aging without the appearance of concurrent diseases is successful aging.

• Nonetheless, the possibility of individuals suffering from dementia, as a consequence of that physiological process of aging, has been postulated.

• It has been suggested that around 120 years of age, without diseases, the population of neocortical synapses could decline to the level found in Alzheimer's disease, with a loss of intracerebral connectivity of around 40%. This causes senile dementia without the presence of the plaques and tangles that characterize Alzheimer's disease(debatable)

• Increase in life expectancy is humanity's greatest achievement.

Genome,Ambiome and longevity

Genome

• Aging is not a genetically programmed process.

• It is controlled by molecular events which cause accumulations in the brain cells and have deleterious effects.

• Mostly the causes of aging are:

Increase in oxidative stress free radicals

Mitochondrial instability hence low energy for

maintenance

Longevity

• Longevity means to delay aging.• It is controlled by genes that maintain and fix

damage caused by free radicals and antioxidant activity.

• Today we know that longevity depends more on genes that are activated by different lifestyles.

• Lifestyle factors govern how long and healthily we live and grow old gracefully.

Ambiome

• Ambiome is a set of cultural ,physical , structural factors that affect anatomy and physiology of the brain.

• The aging brain retains a certain plasticity dependant on its environment.

Changes in the Aging Brain

Anatomical Changes

• These changes are governed by interaction with environment.

• Non homologous changes, hypothesis:

1.During aging, neuronal morphology and tissue density

along with interaction of neurotransmitters in changes

only in specific areas .

No significant loss of neurons except in

mono amine cells of mid brain.

Functional Changes

• More functional changes compared to anatomical ones.

1.Deficits in potentiating induction2.Deficits in long term depression induction3.Changes in Calcium ion homeostasis which is

related to protein oxidation ( high accumulation of Ca ion in intracellular fluid causes neuron death )

• All these lead to cognitive diseases.

Neurotrophic Factors

• Brain diseases depend on 3 main age related changes in the Neurotrophic Factors:

Aging causes decrease in BDNF

Production in Hippocampus,

Causing age related impairments in rats.

Deficit in expression of genes encoding

Neuronal factors lead to disease.

Environmental Enrichment

• Experimental setting in which individuals receive better social and cognitive interactions which leads to better learning and successful brain aging.

These organisms

exhibit

Increased BDNF

release

Improved memory and

learning

Reduction in stress

increased brain weight

and neurogenesis

Caloric Restriction

• 20 to 40% reduction (without malnutrition)• Decrease brain aging by decrease in

mitochondrial reactive Oxygen Species that damage macromolecules.

• Reduce cognitive deficits.• Improves glucose homeostasis and insulin

sensitivity.• Elevated production of BDNF in hippocampus.

Specific nutrients

• Omega 3 fatty acid is important for the neuronal membranes, its increased intake leads to increased BDNF in the hippocampus.

• Another example is flavonoids.

Omega 3 fatty acid increased intak

e

Increased BDNF in hippocampu

s

Counteracts brai

n damage

REGULARAEROBIC EXERCISE

CAUSESNEUROGENESISANGIOGENESIS

IN HIPPOCAMPUS.

MAINTAINS BRAIN

HEALTH AND PLASTICITY

INCREASES BDNF

IN HIPPOCAMPUS

DELAYS ONSET AND PROGRESS OF ALZHEIMERS

AND PARKINSONS.

Stress Reduction

Increase in stress

Glucocorticoids released from adrenals

Anatomical changes in amygdala neurons

Conclusion

• Aging is not a disease. Aging is actually controlled by genes activated by our lifestyle factors and their affects on the anatomy and function of the brain. The primary goal of this article is for people to grow old gracefully with full participation In life. Factors like exercise, low stress, caloric restriction and environmental enrichment can result in successful aging.

Critical Analysis

• Helpful and practical review, however the use of flow charts and a few figures could have made it much better and more interesting.