Vulnerability Imposed by Diet and Brain Trauma for Anxiety-Like Phenotype: Implications for Post-Traumatic Stress Disorders

12, 2013; Volume 8; Issue 3; e57945 Ethika Tyagi, Rahul Agrawal, Yumei Zhuang, Catalina Abad, James A. Waschek,Fernando Gomez-PinillaFrom the University of California, Los Angeles (UCLA) KEY POINTS FROM THIS ARTICLE: 1) Post-traumatic stress disorder (PTSD) is a condition in which individualsexposed to trauma develop high levels of anxiety and inability to cope with routineliving conditions. 2) Mild traumatic brain injury (mTBI, cerebral concussion) is a risk factor for thedevelopment of psychiatric illness such as posttraumatic stress disorder (PTSD). 3) The neuropeptide Y1 receptor (NPY1R) is a hallmark of PTSD. 4) Brain-derived neurotrophic factor (BDNF) signaling is disrupted in PTSD.Brain-derived neurotrophic factor (BDNF) is reduced in the plasma of PTSD victimsand has a role in anxiety and depression. 5) This study was done using rats.Rats were given diets either enriched or deficient in omega-3 fatty acids (n-3)during their brain maturation period. All rats were then transitioned to a western diet (WD); when becoming adult they were then subjected to mTBI. 6) TBI resulted in an increase in anxiety-like behavior, increase in NPY1R, anddecrease in BDNF. These effects were more pronounced in the animals exposed toan n-3 deficient diet, and TBI worsened these effects and more prominently incombination with the n-3 deficiency condition. 7) Also, the n-3 deficient diet resulted in a brain inflammatory immunologicalresponse. 8) The western diet, typically maladaptive dietary habit, lowers the threshold forneurological disorders in response to challenges, including mTBI. 9) The balance between brain health and disease is likely dependent on factorsacquired particularly during early life. [Key Point] 10) Dietary factors are surfacing as strong modulators of brain plasticity with thecapacity to alter the course of brain disorders. [Key Point] 11) Adoption of unhealthy dietary habits is increasingly common in the modernsociety, and this may act as a vulnerability factor for neurological disorders. 12) The omega-3 fatty acid docosohexaenoic acid (DHA) is structured inneuronal plasma membranes and crucial for neuronal signaling. Diet is the onlysource of DHA for the brain and subnormal content of DHA has been associatedwith mood disorders in humans, i.e., increased risk of suicide in a populationexposed to trauma. 13) Dietary DHA has been shown to protect against cognitive impairmentfollowing brain trauma. 14) Consumption of DHA is below recommended levels while the consumption ofhigh fat and high sugar is on the raise in the western society, and this hardship has been attributed to increased incidence of psychiatric disorders. [Key Point] 15) Individuals with PTSD have increased brain immune activation with increasedrelease of inflammatory cytokines interleukin-1b (IL-1b) and IL-10. N-3 fatty acidsare also immunomodulatory. 16) Dietary n-3 deficiency results in anxiety-like behavior. 17) Dietary n-3 deficiency reduced NPY1R levels and switching to the WDreduced levels even further. However, prior exposure to dietary n-3supplementation preserved the levels of NPY1R in animals transitioned toWD. 18) TBI reduced the levels of NPY1R greatest in the n-3 deficient diet group. 19) Exposure to TBI reduced levels of BDNF greatest in the n-3 deficient dietgroup. 20) We found that exposure to an n-3 diet during gestation and throughoutmaturation of the brain are crucial for building neural resilience during adulthood.The lack of dietary n-3 during brain maturation worsened the effects of transition toa WD and subsequent TBI on anxiety-like behavior and molecular counterpart. InTBI, the WD enhances inflammation in animals deprived of n-3 during development. 21) Our results showed that effects of mTBI were more pronounced in the n-3deficient animals switched to WD, arguing about the critical role of dietary n-3 toprotect against the development of anxiety like disorders after TBI. 22) Dietary DHA is protective and improves cognitive impairment following TBI. 23) The neuropeptide Y1 receptor (NPY1R) is a marker of PTSD. Adequate levelsof n-3 fatty acids protect against the effects of WD and mTBI, and these effectswere reflected in higher levels of NPY1R. 24) Patients suffering PTSD have lower levels of plasma BDNF. Conditions of n-3deficiency, WD and mTBI reduced BDNF levels, and dietary n-3 offset these effects. 25) The concept of metabolic programming describes the action of a nutritionalstress/stimulus during critical periods of early development on altering anorganisms physiology and metabolism much later in life. The n-3 diet deficiencyduring brain formation and subsequent transition to WD altered brain capacity tosustain insults during adulthood, and clues to understand the molecular basis ofmetabolic programming. Reduced brain levels of n-3 and increased levels of n-6found in may have impaired neuronal signaling and contributed to the protractedmolecular and behavioral plasticity in adulthood. 26) Dietary factors during the developmental period are an environmentalvariable that can have long-term consequences on behavioral and immuneresponses, particularly under challenging conditions. 27) Chronic sugar consumption can lead to protracted plasticity, particular underdeficiency of n-3 fatty acids. [Very Important] 28) Reduced dietary n-3 creates a state of higher immune activity following TBI. Dietary transition with traumatic brain injury may also affect the immune systemduring n-3 deficiency that may interact with pathophysiologic domain relevant tomood regulation. 29) Our results emphasize the powerful action of diet during early life fordetermining later susceptibility to brain insults, involving elements associated withplasma membrane signaling, synaptic plasticity, and immune system. [Key Point] 30) Given the increasing consumption of unhealthy diets in environments withhigh prevalence of brain trauma, diet may be a factor for predisposing towards thedevelopment of disorders like PTSD. 31) The contents of n-3 during gestation and early life influence the vulnerabilityof the brain to future challenges (changes to western diet (WD) or TBI) during adultlife. KEY MESSAGES FROM DAN MURPHY 1) Omega-3 fatty acids, especially EPA and DHA, are critical for optimum brainfunction. 2) In utero and infant dietary omega-3s greatly influence adult brain physiology,including depression, anxiety, schizophrenia, suicide, and PTSD. 3) Supplemental omega-3s are both preventative and therapeutic for TBI andPTSD.