Integrating ApoE pharmacogenomics, dietary n-6 intake “pharmacoenvironomics”, and cognitive-status/“pharmaconeuropsychomics” with our understanding of the neuroprotective effects of PUFA supplementation
Data from the cross-sectional, epidemiologic, and prospective cohort studies of the associations between dietary omega-3 PUFA intake and cognitive status have been largely positive. Dietary habits in these cohorts are likely longstanding rather than short-lived, as in a clinical trial paradigm. These data suggest three emerging themes and possible areas of future exploration: 1) dependence of the potential beneficial effects of omega-3 PUFA on cognitive status, with cognitively normal persons and those in the earliest stages of memory decline (MCI or early AD) showing the greatest benefit; 2) a modulatory effect of dietary n-6 intake that alters the n-3/n-6 ratio and may negate the positive benefits of n-3 supplementation irrespective of n-3 intake; and 3) a potential modulatory role of ApoE status that influences the dietary benefits of omega-3 PUFA on cognition. Incomplete assessment of these potential modulators/confounders across studies prevents firm conclusions from being drawn.
Along these same lines, the prospective clinical trial data on omega-3 PUFA supplementation to date suggest a potentially positive effect of DHA supplementation on select persons within the study cohorts only. Emerging themes derived from these data include: 1) a potential augmentation of the beneficial effects of DHA in subjects with normal cognition or in the earliest stages of cognitive decline such as MCI or early AD; and 2) a potential role of ApoE status as a modulator of the effect of DHA supplementation in later stage patients. While definitive answers to the potential roles of cognitive status and ApoE genotype influences are lacking, the results of these studies have generated considerable interest in the field for future exploration.
The field of pharmacogenomics is emerging as an important contributor to our understanding of responders and non-responders to a variety of therapeutic interventions in many human disease states. The potential modulatory effects of ApoE status on omega-3 PUFA associations with cognitive status may be a prime example of this phenomenon. The effects of lifestyle modifications or confounders that influence the therapeutic efficacy of certain medications are highly appreciated and need to be considered an example of pharmacoenvironomics, with the potential for n-6 intake to completely negate or abrogate the suggested beneficial effects of omega-3 PUFA supplementation on cognitive status. Future studies investigating the association of omega-3 PUFA intake with cognitive status need to take these factors into account, ensuring adequate sampling between ApoE ɛ4carriers and non-carriers or even enriching study populations in non-carriers that may show maximal benefit. FFQ and plasma fatty acid analyses should pay strict attention to n-6 dietary intake in addition to the focus on omega-3 PUFA. Definitive studies in select populations (ie, ApoE e4 non-carriers with low dietary intake of saturated fat and n-6 fatty acids) may assist in the development of rationally-guided, individualized therapies for the subset of AD subjects that may benefit from omega-3 PUFA administration. Such individualized therapy could potentially benefit the 60% of ApoE ɛ4 non-carriers in the global population of more than 35 million persons suffering from this disease (http://www.alz.co.uk/research/files/World%20Alzheimer%20Report%20Executive%20Summary.pdf), or 21 million affected persons, if omega-3 PUFA supplementation were combined with a regimen of reduced saturated fat and n-6 fatty acids. The potential influences of ApoE status on omega-3 PUFA biology require further exploration and investigation. Linked through their basic roles in lipid biology, ApoE genotype could greatly influence omega-3 PUFA concentrations, transport, metabolism, and sequestration in lipid raft environments essential for healthy neuronal function and synaptic maintenance. Alternative explanations could include combinatorial effects on the production of toxic Aβ species. While omega-3 PUFA augmentation might decrease the production of Aβ, the effects of the ApoE e4 allele could overwhelm or negate such potential benefits of omega-3 PUFA supplementation. Further studies of the basic biology of omega-3 PUFA and ApoE genotype interactions are needed to answer these important questions.
Other considerations include the effect of timing omega-3 PUFA supplementation over the lifespan. Several studies have convincingly demonstrated that omega-3 PUFA supplementation may be more beneficial if administered prior to or in the earliest stages of cognitive decline. It may be that increased omega-3 PUFA levels are protective against cognitive decline and AD, but later play no role in the pathogenic cascade of events that culminate in the clinical and biological expression of fulminate AD, even in the early stages of disease. Alternatively the beneficial effects of omega-3 PUFA augmentation may still exist, but simply be overwhelmed by the strength of the pathological processes responsible for AD once the disease has produced the clinical and biological manifestations of moderate or more severe disease. Lessons learned from the past might suggest a focus on earlier or even preclinical stages of AD as a target for omega-3 PUFA intervention. Such an approach has practical feasibility given the global shift in focus on AD to the earliest clinical MCI and even preclinical stages of AD that are being investigated by researchers.
Far from dampening scientific progress in our understanding of the potential benefits of omega-3 PUFA intake, the data obtained from the many studies investigating dietary omega-3 PUFA, while seemingly disparate and even contradictory at times, have resulted in an increased understanding of the potential importance of omega-3 PUFA biology in the CNS and its potential importance in abrogating both age-related cognitive decline and the development of AD. These insights should serve to spur much needed research in this area of neurodegenerative biology and advance our understanding of this devastating disease.
Integrating ApoE pharmacogenomics, dietary n-6 intake “pharmacoenvironomics”, and cognitive-status/“pharmaconeuropsychomics” with our understanding of the neuroprotective effects of PUFA supplementationData from the cross-sectional, epidemiologic, and prospective cohort studies of the associations between dietary omega-3 PUFA intake and cognitive status have been largely positive. Dietary habits in these cohorts are likely longstanding rather than short-lived, as in a clinical trial paradigm. These data suggest three emerging themes and possible areas of future exploration: 1) dependence of the potential beneficial effects of omega-3 PUFA on cognitive status, with cognitively normal persons and those in the earliest stages of memory decline (MCI or early AD) showing the greatest benefit; 2) a modulatory effect of dietary n-6 intake that alters the n-3/n-6 ratio and may negate the positive benefits of n-3 supplementation irrespective of n-3 intake; and 3) a potential modulatory role of ApoE status that influences the dietary benefits of omega-3 PUFA on cognition. Incomplete assessment of these potential modulators/confounders across studies prevents firm conclusions from being drawn.Along these same lines, the prospective clinical trial data on omega-3 PUFA supplementation to date suggest a potentially positive effect of DHA supplementation on select persons within the study cohorts only. Emerging themes derived from these data include: 1) a potential augmentation of the beneficial effects of DHA in subjects with normal cognition or in the earliest stages of cognitive decline such as MCI or early AD; and 2) a potential role of ApoE status as a modulator of the effect of DHA supplementation in later stage patients. While definitive answers to the potential roles of cognitive status and ApoE genotype influences are lacking, the results of these studies have generated considerable interest in the field for future exploration.The field of pharmacogenomics is emerging as an important contributor to our understanding of responders and non-responders to a variety of therapeutic interventions in many human disease states. The potential modulatory effects of ApoE status on omega-3 PUFA associations with cognitive status may be a prime example of this phenomenon. The effects of lifestyle modifications or confounders that influence the therapeutic efficacy of certain medications are highly appreciated and need to be considered an example of pharmacoenvironomics, with the potential for n-6 intake to completely negate or abrogate the suggested beneficial effects of omega-3 PUFA supplementation on cognitive status. Future studies investigating the association of omega-3 PUFA intake with cognitive status need to take these factors into account, ensuring adequate sampling between ApoE ɛ4carriers and non-carriers or even enriching study populations in non-carriers that may show maximal benefit. FFQ and plasma fatty acid analyses should pay strict attention to n-6 dietary intake in addition to the focus on omega-3 PUFA. Definitive studies in select populations (ie, ApoE e4 non-carriers with low dietary intake of saturated fat and n-6 fatty acids) may assist in the development of rationally-guided, individualized therapies for the subset of AD subjects that may benefit from omega-3 PUFA administration. Such individualized therapy could potentially benefit the 60% of ApoE ɛ4 non-carriers in the global population of more than 35 million persons suffering from this disease (http://www.alz.co.uk/research/files/World%20Alzheimer%20Report%20Executive%20Summary.pdf), or 21 million affected persons, if omega-3 PUFA supplementation were combined with a regimen of reduced saturated fat and n-6 fatty acids. The potential influences of ApoE status on omega-3 PUFA biology require further exploration and investigation. Linked through their basic roles in lipid biology, ApoE genotype could greatly influence omega-3 PUFA concentrations, transport, metabolism, and sequestration in lipid raft environments essential for healthy neuronal function and synaptic maintenance. Alternative explanations could include combinatorial effects on the production of toxic Aβ species. While omega-3 PUFA augmentation might decrease the production of Aβ, the effects of the ApoE e4 allele could overwhelm or negate such potential benefits of omega-3 PUFA supplementation. Further studies of the basic biology of omega-3 PUFA and ApoE genotype interactions are needed to answer these important questions.Other considerations include the effect of timing omega-3 PUFA supplementation over the lifespan. Several studies have convincingly demonstrated that omega-3 PUFA supplementation may be more beneficial if administered prior to or in the earliest stages of cognitive decline. It may be that increased omega-3 PUFA levels are protective against cognitive decline and AD, but later play no role in the pathogenic cascade of events that culminate in the clinical and biological expression of fulminate AD, even in the early stages of disease. Alternatively the beneficial effects of omega-3 PUFA augmentation may still exist, but simply be overwhelmed by the strength of the pathological processes responsible for AD once the disease has produced the clinical and biological manifestations of moderate or more severe disease. Lessons learned from the past might suggest a focus on earlier or even preclinical stages of AD as a target for omega-3 PUFA intervention. Such an approach has practical feasibility given the global shift in focus on AD to the earliest clinical MCI and even preclinical stages of AD that are being investigated by researchers.Far from dampening scientific progress in our understanding of the potential benefits of omega-3 PUFA intake, the data obtained from the many studies investigating dietary omega-3 PUFA, while seemingly disparate and even contradictory at times, have resulted in an increased understanding of the potential importance of omega-3 PUFA biology in the CNS and its potential importance in abrogating both age-related cognitive decline and the development of AD. These insights should serve to spur much needed research in this area of neurodegenerative biology and advance our understanding of this devastating disease.
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