Effect of docosahexaenoic acid content of maternal diet on auditory brainstem conduction times in rat pups

Omega-3 fatty acids and health of auditory and vestibular systems: a comprehensive review

PURPOSE

The purpose of this study was to comprehensively review animal and human studies that explore the role of omega-3 PUFAs in maintaining the health of the auditory organ across all life stages.

METHODS

This narrative review involved searching Scopus, PubMed, Google Scholar, and Cochrane Library databases for relevant articles from December 1980 to July 2023.

RESULTS

some animal and human studies suggest that both deficiency and excessive intake of long-chain omega-3 PUFAs, particularly docosahexaenoic acid (DHA), can lead to auditory neural conduction impairment and reduced hearing acuity from fetal development to old age (presbycusis). These effects are likely to be dependent on the dosage. Some research indicates that an excessive intake of omega-3, rather than a deficiency, can result in nutritional toxicity and hearing impairments. Animal studies highlight the positive impact of omega-3 supplements with high DHA content in addressing hearing damage, but human research on this subject is limited. Furthermore, certain studies propose that omega-3 PUFAs may prevent or delay age-related hearing loss, with high plasma omega-3 concentration, particularly long-chain omega-3 PUFA, linked to reduced hearing loss. Additionally, consuming fish more than twice a week may be associated with a lower risk of hearing loss in adulthood, with these effects potentially influenced by age and gender. However, the majority of studies have been conducted on animals, and clinical trials are scarce. Research on the influence of omega-3 PUFAs on the peripheral and central vestibular systems remains limited.

CONCLUSION

This article delves into the impact of omega-3 on the auditory-vestibular system, exploring its influence on neurodevelopment, protection, and treatment. It not only highlights specific research gaps but also offers valuable insights for potential future studies.

Serum polyunsaturated fatty acids and hearing threshold shifts in adults in the United States: A cross-sectional study

Background

Few studies have evaluated the association between polyunsaturated fatty acids (PUFAs) and hearing levels. This study aimed to investigate the association between serum PUFAs and hearing threshold shifts in US adults.

Methods

We investigated 913 adults from the National Health and Nutrition Examination Survey (NHANES) 2011-2012. Multivariate linear regression analyses were conducted to evaluate associations between PUFA and hearing threshold shifts.

Results

Overall, 11 serum PUFAs were inversely associated with low-frequency thresholds, especially in men, and were positively related to high-frequency thresholds, particularly in the 40-59 years old cohort. Furthermore, some serum PUFAs were positively associated with both hearing threshold subgroups in women.

Conclusion

Some PUFAs tend to be beneficial for low-frequency hearing status and detrimental to the high-frequency hearing threshold. The male sex may play a protective role in this association, while the female sex and middle age may be detrimental in the effect of PUFAs on hearing function.

Prenatal High-Fat Diet Rescues Communication Deficits in Fmr1 Mutant Mice in a Sex-Specific Manner

Using high-throughput analysis methods, the present study sought to determine the impact of prenatal high-fat dietary manipulations on isolation-induced ultrasonic vocalization production in both male and female Fmr1mutants on postnatal day 9. Prior to breeding, male FVB/129 Fmr1 wildtype and female Fmr1 heterozygous breeding pairs were assigned to 1 of 3 diet conditions: standard lab chow, omega-3 fatty acid-enriched chow, and a diet controlling for the fat increase. Prenatal exposure to omega-3 fatty acids improved reductions in the number of calls produced by Fmr1heterozygotes females. Moreover, diminished spectral purity in the female Fmr1homozygous mouse was rescued by exposure to both high-fat diets, although these effects were not seen in the male Fmr1knockout. Prenatal dietary fat manipulation also influenced several other aspects of vocalization production, such as the number of calls produced and their fundamental frequency, aside from effects due to loss of Fmr1.Specifically, in males, regardless of genotype, prenatal exposure to high omega-3s increased the average fundamental frequency of calls. These data support the need for future preclinical and clinical work elucidating the full potential of prenatal high-fat diets as a novel therapeutic alternative forFragile X syndrome.

Interesterified fat consumption since gestation decreases striatal dopaminergic targets levels and gdnf impairing locomotion of adult offspring

Interesterified fat (IF) currently substitutes the hydrogenated vegetable fat (HVF) in processed foods. However, the IF consumption impact on the central nervous system (CNS) has been poorly studied. The current study investigated connections between IF chronic consumption and locomotor impairments in early life period and adulthood of rats and access brain molecular targets related to behavior changes in adulthood offspring. During pregnancy and lactation, female rats received soybean oil (SO) or IF and their male pups received the same maternal supplementation from weaning until adulthood. Pups' motor ability and locomotor activity in adulthood were evaluated. In the adult offspring striatum, dopaminergic targets, glial cell line-derived neurotrophic factor (GDFN) and lipid profile were quantified. Pups from IF supplementation group presented impaired learning concerning complex motor skill and sensorimotor behavior. The same animals showed decreased locomotion in adulthood. Moreover, IF group showed decreased immunoreactivity of all dopaminergic targets evaluated and GDNF, along with important changes in FA composition in striatum. This study shows that the brain modifications induce by IF consumption resulted in impaired motor control in pups and decreased locomotion in adult animals. Other studies about health damages induced by IF consumption may have a contribution from our current outcomes.

Effects of energy and essential fatty acids content in breast milk on infant's head dimensions

OBJECTIVES

Essential fatty acids (EFA), including linoleic acid (LA) and alpha-linolenic acid (ALA), are indispensable for proper brain growth especially in the first months after birth when it develops most rapidly. Since fats, especially EFA, in breast milk are highly variable between mothers, we indirectly examined whether milk energy, LA and ALA content in breast milk affect volume and shape of the infant's head.

METHODS

The study encompassed 60 mothers and their healthy term-born infants between the third and sixth month of lactation. The percentage of macronutrients and dry matter in human milk samples was assessed using Fourier-transform infrared spectroscopy (FTIR), and LA and ALA concentrations in breast milk were determined using gas chromatography (GC). Infant head measurements were taken using standard anthropometric equipment and methods.

RESULTS

LA content in breast milk was found to be positively associated with head volume in boys. Furthermore, ALA content was positively associated with the head height-to-length ratio thus with more arched head in infants irrespective of sex. No relationship was found between milk energy content in mothers' milk and infant head dimensions.

CONCLUSIONS

This is the first study to demonstrate a relationship between EFA concentration in human milk and infant head dimensions. Given that LA and ALA in human milk are variable in women and due to the extremely rapid growth of nerve tissue in the first months of life, adequate supply of EFA in breast milk should attract the attention of public health sciences.

Effects of enriched endogenous omega-3 fatty acids on age-related hearing loss in mice

Objective

Dietary intervention is a practical prevention strategy for age-related hearing loss (AHL). Omega-3 (n-3) polyunsaturated fatty acids (PUFAs) may be effective in prevention of AHL due to their anti-inflammatory and tissue-protective functions. Age-related changes in the hearing function of wild-type and Fat-1 transgenic mice derived from the C57BL/6N strain, which can convert omega-6 PUFAs to n-3 PUFAs and consequently produce enriched endogenous n-3 PUFAs, were investigated to test the efficacy of n-3 PUFAs for AHL prevention.

Results

At 2 months, the baseline auditory brainstem response (ABR) thresholds were the same in Fat-1 and wild-type mice at 8–16 kHz but were significantly higher in Fat-1 mice at 4 and 32 kHz. In contrast, the ABR thresholds of Fat-1 mice were significantly lower at 10 months. Moreover, the ABR thresholds of Fat-1 mice at low-middle frequencies were significantly lower at 13 months (12 kHz). Body weights were significantly reduced in Fat-1 mice at 13 months, but not at 2, 10, and 16–17 months. In conclusion, enriched endogenous n-3 PUFAs produced due to the expression of the Fat-1 transgene partially alleviated AHL in male C57BL/6N mice.

Association of Delta-6-Desaturase Expression with Aggressiveness of Cancer, Diabetes Mellitus, and Multiple Sclerosis: A Narrative Review

Background: The phosphatidylinositol 3-kinase/ protein kinase B /mammalian target of rapamycin (PI3K/Akt/ mTOR) signaling regulates multiple cellular processes and organizes cell proliferation, survival, and differentiation with the available nutrients, in particular, fatty acids. Polyunsaturated fatty acids (PUFAs) are cytotoxic to cancer cells and play a critical role in the treatment of multiple sclerosis (MS) and diabetes mellitus (DM). PUFAs are produced in the body by desaturases and elongases from dietary essential fatty acids (EFAs), primarily involving delta-6-desaturase (D6D). D6D is a rate-limiting enzyme for maintaining many aspects of lipid homeostasis and normal health. D6D is important to recognize the mechanisms that regulate the expression of this enzyme in humans. A lower level of D6D was seen in breast tumors compared to normal tissues. Interestingly, the elevated serum level of D6D was seen in MS and DM, which explains the critical role of D6D in inflammatory diseases. Methods: We searched databases of PubMed, Web of Science (WOS), Google Scholar, Scopus and related studies by predefined eligibility criteria. We assessed their quality and extracted data. Results: Regarding the mTOR signaling pathway, there is remarkable contributions of many inflammatory diseases to attention to common metabolic pathways are depicted. Of course, we need to have the insights into each disorder and their pathological process. The first step in balancing the intake of EFAs is to prevent the disruption of metabolism and expression of the D6D enzyme. Conclusions: The ω6 and ω3 pathways are two major pathways in the biosynthesis of PUFAs. In both of these, D6D is a vital bifunctional enzyme desaturating linoleic acid or alpha-linolenic acid. Therefore, if ω6 and ω3 EFAs are given together in a ratio of 2: 1, the D6D expression will be down-regulated and normalized.

The Role of Essential Fatty Acids in Anorexia Nervosa and Obesity

The two basic questions in food intake study are what we eat, and how much do we eat. Most research is directed toward the control of how much is eaten. This is likely the result of the increased number of individuals with eating disorders in the Western world. Feeding behavior is highly complex, and is controlled by many psychological, physiological, biochemical, and immunological factors. The aim of this review is to clarify the involvement of fatty acids in eating disorders such as anorexia and binge eating disorder. The review will describe the modified fatty acid profile observed in individuals with anorexia or binge eating disorder, and discuss on what factors fatty acids can exert beneficial effects. In addition, the differences and similarities between anorexia and binge eating disorder will be discussed. We suggest that beneficial effects of essential fatty acids on both anorexia and binge eating disorder can be explained by the stabilizing effect of those fatty acids on the neuronal membrane fluidity index.

The influence of fish oil on neurological development and function

Fish oil originates from fish tissue rich in omega-3 fatty acids. These include eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Healthy individuals are advised to consume foods rich in fish oil at least twice a week. However, such intake varies depending on cultural or personal preference, and socio-economic status. Many families and patients with chronic neurological conditions consume supplements containing omega-3 fatty acids. We are frequently requested to give advice and recommendations on using such agents to help improve neurological developmental and cognitive functions. The objective of this review is to discuss the available literature supporting the role of fish oils on brain development and function. There is a growing body of literature suggesting a potential benefit of long chain polyunsaturated fatty acids; however it is still unclear if there are response variations according to the developmental stage, age, and dose.

L'influence de l'huile de poisson sur le développement et la fonction neurologique. L'huile de poisson provient de tissus de poisson riches en acides gras oméga-3, l'acide eicosapentaéno&IUque (EPA) et l'acide docosahexaénoïque (DHA). On conseille aux individus en bonne santé de consommer des aliments riches en huiles de poisson au moins deux fois par semaine. Cependant, leur consommation varie selon les préférences culturelles ou personnelles ainsi que selon le statut socio-économique. Plusieurs familles et plusieurs patients atteints de maladies neurologiques chroniques consomment des suppléments contenant des acides gras oméga-3. On nous demande souvent des conseils et des recommandations sur l'utilisation de ces agents pour aider à améliorer le développement neurologique et les fonctions cognitives. L'objectif de cette revue est de discuter de la littérature disponible en faveur du rôle des huiles de poisson dans le développement et le fonctionnement du cerveau. Il existe une documentation de plus en plus importante qui suggère que les acides gras polyinsaturés à longue chaîne pourraient ětre bénéfiques. Cependant, on ne sait pas si la réponse peut varier selon le stade du développement, l'âge et la dose.

Dietary LC-PUFA in iron-deficient anaemic pregnant and lactating guinea pigs induce minor defects in the offsprings' auditory brainstem responses

OBJECTIVES

We previously demonstrated that a mild pre-natal/early post-natal iron-deficient anaemic (IDA) diet devoid of long-chain polyunsaturated fatty acids (LC-PUFA) affected development, neurophysiology, and cerebral lipid biochemistry of the guinea pigs' progeny. Impacts of dietary LC-PUFA on altered cerebral development resulting from pre-natal IDA are unknown. To address this health issue, impacts of mild gestational IDA in the presence of dietary LC-PUFA on the offsprings' neural maturation were studied in guinea pigs using auditory brainstem responses (ABRs) and assessments of brain fatty acids (FAs).

METHODS

Female guinea pigs (n = 10/group) were fed an iron sufficient (IS) or IDA diet (146 and 12.7 mg iron/kg, respectively) with physiological amounts of LC-PUFA, during the gestation and lactation periods. From post-natal day (PNd) 9 onwards, the IS + PUFA diet was given to both groups of weaned offspring. Cerebral tissue and offsprings' ABR were collected on PNd24.

RESULTS

There was no difference in peripheral and brainstem transmission times (BTTs) between IS + PUFA and IDA + PUFA siblings (n = 10/group); the neural synchrony was also similar in both groups. Despite the absence of differences in auditory thresholds, IDA + PUFA siblings demonstrated a sensorineural hearing loss in the extreme range of frequencies (32, 4, and 2 kHz), as well as modified brain FA profiles compared to the IS + PUFA siblings.

DISCUSSION

The present study reveals that siblings born from dams exposed to a moderate IDA diet including balanced physiological LC-PUFA levels during pregnancy and lactation demonstrate minor impairments of ABR compared to the control siblings, particularly on the auditory acuity, but not on neural synchrony, auditory nerve velocity and BTT.

Critical appraisal of omega-3 fatty acids in attention-deficit/hyperactivity disorder treatment

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. The classical treatment of ADHD where stimulant medication is used has revealed severe side effects and intolerance. Consequently, the demand to search for alternative treatment has increased rapidly. When comparing levels of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) in ADHD patients with those in age-matching controls, lower levels are found in ADHD patients' blood. ω-3 PUFAs are essential nutrients and necessary for a proper brain function and development. Additionally, there are strong indications that ω-3 PUFA supplements could have beneficial effects on ADHD. However, the results of ω-3 PUFA supplementation studies show a high variability. Therefore, we reviewed recent studies published between 2000 and 2015 to identify effective treatment combinations, the quality of design, and safety and tolerability of ω-3-containing food supplements. We searched the databases MEDLINE, PubMed, and Web of Science with keywords such as "ADHD" and "ω-3/6 PUFA" and identified 25 studies that met the inclusion and exclusion criteria. The results of these ω-3 PUFA studies are contradictory but, overall, show evidence for a successful treatment of ADHD symptoms. Tolerability of the given supplements was high, and only mild side effects were reported. In conclusion, there is evidence that a ω-3 PUFA treatment has a positive effect on ADHD. It should be added that treatment could be more effective in patients with mild forms of ADHD. Moreover, the dosage of stimulant medication could be reduced when used in combination with ω-3 PUFA supplements. Further studies are necessary to investigate underlying mechanisms that can lead to a reduction of ADHD symptoms due to ω-3 PUFA treatments and also to determine the optimal concentrations of ω-3 PUFAs, whether used as single treatment or in combination with other medication.

Neurophysiologic measures of auditory function in fish consumers: associations with long chain polyunsaturated fatty acids and methylmercury

BACKGROUND

Determining if associations exist between child neurodevelopment and environmental exposures, especially low level or background ones, is challenging and dependent upon being able to measure specific and sensitive endpoints. Psychometric or behavioral measures of CNS function have traditionally been used in such studies, but do have some limitations. Auditory neurophysiologic measures examine different nervous system structures and mechanisms, have fewer limitations, can more easily be quantified, and might be helpful additions to testing. To date, their use in human epidemiological studies has been limited. We reviewed the use of auditory brainstem responses (ABR) and otoacoustic emissions (OAE) in studies designed to determine the relationship of exposures to methyl mercury (MeHg) and nutrients from fish consumption with neurological development. We included studies of experimental animals and humans in an effort to better understand the possible benefits and risks of fish consumption.

OBJECTIVES

We reviewed the literature on the use of ABR and OAE to measure associations with environmental exposures that result from consuming a diet high in fish. We focused specifically on long chain polyunsaturated fatty acids (LCPUFA) and MeHg.

METHODS

We performed a comprehensive review of relevant studies using web-based search tools and appropriate search terms.

RESULTS

Gestational exposure to both LCPUFA and MeHg has been reported to influence the developing auditory system. In experimental studies supplemental LCPUFA is reported to prolong ABR latencies and human studies also suggest an association. Experimental studies of acute and gestational MeHg exposure are reported to prolong ABR latencies and impair hair cell function. In humans, MeHg exposure is reported to prolong ABR latencies, but the impact on hair cell function is unknown.

CONCLUSION

The auditory system can provide objective measures and may be useful in studying exposures to nutrients and toxicants and whether they are associated with children's neurodevelopment.

Mild maternal iron deficiency anemia during pregnancy and lactation in guinea pigs causes abnormal auditory function in the offspring

Iron deficiency (ID) anemia (IDA) adversely affects different aspects of the nervous system such as myelinogenesis, neurotransmitters synthesis, brain myelin composition, and brain fatty acid and eicosanoid metabolism. Infant neurophysiological outcome in response to maternal IDA is underexplored, especially mild to moderate maternal IDA. Furthermore, most human research has focused on childhood ID rather than prenatal or neonatal ID. Thus, our study evaluated the consequences of mild maternal IDA during pregnancy and lactation on the offsprings' auditory function using the auditory brainstem response (ABR). This technique provides objective measures of auditory acuity, neural transmission times along the peripheral and brainstem portions of the auditory pathway, and postnatal brain maturation. Female guinea pigs (n = 10/group) were fed an iron sufficient diet (ISD) or an iron deficient diet (IDD) (144 and 11.7 mg iron/kg) during their acclimation, gestation, and lactation periods. From postnatal d (PNd) 9 onward, the ISD was given to all weaned offspring. ABR were collected from the offspring on PNd24 using a broad range of stimulus intensities in response to 2, 4, 8, 16, and 32 kHz tone pips. IDA siblings (n = 4), [corrected] compared with the IS siblings (n = 5), had significantly elevated ABR thresholds (hearing loss) in response to all tone pips. These physiological disturbances were primarily due to a sensorineural hearing loss, as revealed by the ABR's latency-intensity curves. These results indicate that mild maternal IDA during gestation and lactation altered the hearing and nervous system development of the young offspring.

Excess omega-3 fatty acid consumption by mothers during pregnancy and lactation caused shorter life span and abnormal ABRs in old adult offspring

Consuming omega-3 fatty acids (omega-3 FA) during pregnancy and lactation is beneficial to fetal and infant development and might reduce the incidence and severity of preterm births by prolonging pregnancy. Consequently, supplementing maternal diets with large amounts of omega-3 FA is gaining acceptance. However, both over- and under-supplementation with omega-3 FA can harm offspring development. Adverse fetal and neonatal conditions in general can enhance age-related neural degeneration, shorten life span and cause other adult-onset disorders. We hypothesized that maternal over- and under-nutrition with omega-3 FA would shorten the offspring's life span and enhance neural degeneration in old adulthood. To test these hypotheses, female Wistar rats were randomly assigned to one of the three diet conditions starting from day 1 of pregnancy through the entire period of pregnancy and lactation. The three diets were Control omega-3 FA (omega-3/omega-6 ratio approximately 0.14), Excess omega-3 FA (omega-3/omega-6 ratio approximately 14.5) and Deficient omega-3 FA (omega-3/omega-6 ratio approximately 0% ratio). When possible, one male and female offspring from each litter were assessed for life span and sensory/neural degeneration (n=15 litters/group). The Excess offspring had shorter life spans compared to their Control and Deficient cohorts (mean+/-SEM=506+/-24, 601+/-14 and 585+/-21 days, p<or=0.004) when the study terminated on postnatal day 640. The Excess offspring had a higher incidence of presbycusis than the Control and Deficient groups (33.3, 4.3 and 4.5%, p=0.011) and a persistence of other sensory/neurological abnormalities and lower body weights in old adulthood. In conclusion, omega-3 FA over-nutrition or imbalance during pregnancy and lactation had adverse effects on life span and sensory/neurological function in old adulthood. The adverse outcomes in the Excess offspring were likely due to a "nutritional toxicity" during fetal and/or neonatal development that programmed them for life-long health disorders. The health implication is that consuming or administering large amounts of omega-3 FA during pregnancy and lactation seems inadvisable because of adverse effects on the offspring.

Abnormal neurological responses in young adult offspring caused by excess omega-3 fatty acid (fish oil) consumption by the mother during pregnancy and lactation

Consuming omega-3 fatty acids (omega-3 FA) during pregnancy and lactation benefits fetal and infant brain development and might reduce the severity of preterm births by prolonging pregnancy. However, diets that are relatively rich in omega-3 FA can adversely affect fetal and infant development and the auditory brainstem response (ABR), a measure of brain development and sensory function. We previously examined the offspring of female rats fed excessive, adequate or deficient amounts of omega-3 FA during pregnancy and lactation. The 24-day-old offspring in the Excess group, compared to the Control group, had postnatal growth retardation and poor hearing acuity and prolonged neural transmission times as evidenced by the ABR. The Deficient group was intermediate. The current study followed these offspring to see if these poor outcomes persisted into young adulthood. Based on prior findings, we hypothesized that the Excess and Deficient offspring would "catch-up" to the Control offspring by young adulthood. Female Wistar rats received one of the three diet conditions from day 1 of pregnancy through lactation. The three diets were the Control omega-3 FA condition (omega-3/omega-6 ratio approximately 0.14), the Excess omega-3 FA condition (omega-3/omega-6 ratio approximately 14.0) and Deficient omega-3 FA condition (omega-3/omega-6 ratio approximately 0% ratio). The Control diet contained 7% soybean oil; whereas the Deficient and Excess omega-3 FA diets contained 7% safflower oil and 7% fish oil, respectively. One male and female offspring per litter were ABR-tested as young adults using tone pip stimuli of 2, 4, 8 and 16 kHz. The postnatal growth retardation and prolonged neural transmission times in the Excess and Deficient pups had dissipated by young adulthood. In contrast, the Excess group had elevated ABR thresholds (hearing loss) at all tone pip frequencies in comparison to the Control and Deficient groups. The Deficient group had worse ABR thresholds than the Control group in response to the 8 kHz tone pips only. The Excess group also had ABR amplitude-intensity profiles suggestive of hyperacusis. These results are consistent with the Barker hypothesis concerning the fetal and neonatal origins of adult diseases. Thus, consuming diets that are excessively rich or deficient in omega-3 FA during pregnancy and lactation seems inadvisable because of risks for long-lasting adverse effects on brain development and sensory function.

Excess and deficient omega-3 fatty acid during pregnancy and lactation cause impaired neural transmission in rat pups

Omega-3 fatty acids (omega-3 FA) consumption during pregnancy and lactation is beneficial to fetal and infant growth and may reduce the severity of preterm births. Thus, scientists and clinicians are recommending increasingly higher omega-3 FA doses for pregnant women and nursing babies for advancing the health of preterm, low birth weight, and normal babies. In contrast, some studies report that over-supplementation with omega-3 FA can have adverse effects on fetal and infant development by causing a form of nutritional toxicity. Our goal was to assess the effects of omega-3 FA excess and deficiency during pregnancy and lactation on the offspring's neural transmission as evidenced by their auditory brainstem responses (ABR). Female Wistar rats were given one of three diets from day 1 of pregnancy through lactation. The three diets were the Control omega-3 FA condition (omega-3/omega-6 ratio approximately 0.14), the Deficient omega-3 FA condition (omega-3/omega-6 ratio approximately 0%) and the Excess omega-3 FA condition (omega-3/omega-6 ratio approximately 14.0). The Control diet contained 7% soybean oil, whereas the Deficient diet contained 7% safflower oil and the Excess diet contained 7% fish oil. The offspring were ABR-tested on postnatal day 24. The rat pups in the Excess group had prolonged ABR latencies in comparison to the Control group, indicating slowed neural transmission times. The pups in the Excess group also showed postnatal growth restriction. The Deficient group showed adverse effects that were milder than those seen in the Excess group. Milk fatty acid profiles reflected the fatty acid profiles of the maternal diets. In conclusion, excess or deficient amounts of omega-3 FA during pregnancy and lactation adversely affected the offspring's neural transmission times and postnatal thriving. Consuming either large or inadequate amounts of omega-3 FA during pregnancy and lactation seems inadvisable because of the potential for adverse effects on infant development.

The effects of maternal dietary docosahexaenoic acid intake on rat pup myelin and the auditory startle response

We investigated the effects of maternal docosahexanoic acid (DHA) supplementation on pups' auditory startle responses and the composition of brain myelin.

METHODS

Timed-pregnant rats were fed throughout pregnancy and lactation diets that contained 0, 0.3, 0.7 or 3% of total fatty acids as DHA. Milk was collected from culled pups' stomachs on postnatal day (PND) 3, latency of the auditory startle reflex was measured on PND 15, and pups were killed and brains collected on PND 24.

RESULTS

Higher levels of DHA in maternal diet were reflected in milk and in pups' myelin. The latency of the auditory startle response was significantly longer in offspring of dams fed higher levels of DHA. There was a positive correlation between the myelin content of DHA and the latency of the startle response (p = 0.044), and a negative correlation between the myelin content of DHA and the myelin content of cholesterol (p = 0.005).

CONCLUSION

High levels of maternal DHA intake alter the lipid composition of rat pup myelin, and are associated with longer latencies of the auditory startle response--a myelin-dependent electrophysiologic response.

Reduced auditory acuity in rat pups from excess and deficient omega-3 fatty acid consumption by the mother

Consumption of the nutrients omega-3 fatty acids (omega-3 FA) during pregnancy and lactation is considered beneficial to fetal and infant development. It may also reduce the incidence and severity of preterm births by prolonging gestational length. However several recent human and animal studies have reported that over-supplementation with omega-3 FA, especially in the form of fish oil, can have adverse effects on fetal and infant development and the auditory brainstem response (ABR). Our goal was to assess further the effects of omega-3 FA excess and deficiency during pregnancy and lactation on the offspring's auditory acuity as evidenced by their ABR thresholds. Female Wistar rats were given diets that were either deficient, adequate (control) or excess in omega-3 FA from day 1 of pregnancy through lactation. The offspring were ABR-tested at the postnatal age of 24 days. The rat pups in the Excess treatment condition had significantly elevated (worse) ABR thresholds, postnatal growth restriction, and a trend for increased postnatal mortality in comparison to the Control group. The Deficient group was intermediate. In conclusion, excess or deficient amounts of omega-3 FA during pregnancy and lactation in the laboratory rat adversely affected the offspring's auditory acuity. Postnatal thriving was also adversely affected. Consuming or administering large or inadequate amounts of omega-3 FA during pregnancy and lactation seems inadvisable because of the potential for adverse effects on infant development.

Does inadequate maternal iron or DHA status have a negative impact on an infant's functional outcomes?

Marginal intake of iron and omega-3 long-chain fatty acids (DHA) is prevalent among pregnant women. It is not clear to what extent poor iron or DHA status during pregnancy impacts on an infant's functional outcomes. A few studies suggest that inadequate maternal iron or DHA status may be associated with suboptimal functional outcomes in infants. In addition, there is a lack of prospective studies using randomized, double-blind design or experimental studies with appropriate animal models. Although both nutrients are involved in early brain development and their metabolism is interrelated, no study has examined the interaction between iron and omega-3 fatty acids during pregnancy.

CONCLUSION

Long-term studies on large cohorts of pregnant women and their infants are needed to determine whether inadequate iron or DHA status during pregnancy is detrimental to infant neurodevelopment.

Essential fatty acids and the brain: from infancy to aging

The major effects of essential fatty acids (EFA) on brain structure and functions are reviewed. EFA determine the fluidity of neuronal membrane and control the physiological functions of the brain. EFA is also involved in synthesis and functions of brain neurotransmitters, and in the molecules of the immune system. Since they must be supplied from the diet, a decreased bioavailability is bound to induce major disturbances. While the brain needs a continuous supply during the life span, there are two particularly sensitive periods-infancy and aging. EFA deficiency during infancy delays brain development, and in aging will accelerate deterioration of brain functions. In discussing the role of EFA two issues must be considered-the blood-brain barrier, which determines the bioavailability, and the myelination process, which determines the efficiency of brain and retinal functions.

Essential fatty acid transfer and fetal development

Docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6) are important structural components of the central nervous system. These fatty acids are transferred across the placenta, and are accumulated in the brain and other organs during fetal development. Depletion of 22:6n-3 from the retina and brain results in reduced visual function and learning deficits: these may involve critical roles of 22:6n-3 in membrane-dependent signaling pathways and neurotransmitter metabolism. Transfer of 22:6n-3 across the placenta involves specific binding and transfer proteins that facilitate higher concentrations of 22:6n-3 and 20:4n-6, but lower linoleic acid (18:2n-6) in fetal compared with maternal plasma, or in the breast-fed or formula-fed infant. However, human and animal studies both demonstrate that maternal diet impacts fetal 22:6n-3 and 20:4n-6 accretion. After birth, parenteral lipid, human milk and infant formula feeding all result in a marked decrease in plasma 22:6n-3 and 20:4n-6 and an increase in 18:2n-6. Estimation of fetal tissue fatty acid accretion suggests that current preterm infant feeds are unlikely to meet in utero rates of 22:6n-3 accretion. Consideration needs to be given to whether fetal plasma 22:6n-3 and 20:4n-6 enrichment and the low 18:2n-6 facilitates accretion of 22:6n-3 and 20:4n-6 in developing tissues.

Auditory brainstem evoked response in juvenile rats fed rat milk formulas with high docosahexaenoic acid

Previous studies found that juvenile offspring of rats fed high docosahexaenoic acid (DHA; 22:6n-3) diets through gestation and lactation had longer auditory brainstem-evoked response (ABR) accompanied by higher 22:6n-3 and lower arachidonic acid (ARA; 20:4n-6) in brain. In the present study, ABR was assessed in juvenile rats fed high-DHA diets only postnatally.

METHODS

Rat pups were fed rat milk formulas with varying amounts of DHA and ARA to 19 days of age followed by diets with the corresponding fatty acids. The high-DHA group was fed 2.3% of fatty acids as DHA, the DHA + ARA group was fed DHA and ARA at 0.6 and 0.4% of fatty acids, levels similar to those in some infant formulas, and the unsupplemented group was fed no DHA or ARA. ABR and fatty acid and monoamine levels in brain were measured on postnatal days 26-28. Statistical analyses were measured by ANOVA.

RESULTS

ARA and DHA levels in brain increased with supplementation. ABR was shorter in the high-DHA group than the DHA + ARA group and not different from the unsupplemented or dam-reared suckling group. Norepinephrine levels in the inferior colliculus were lower in the high-DHA group than the DHA + ARA group and higher in all formula groups compared to the dam-reared group.

CONCLUSION

In contrast to the longer ABR in juvenile offspring of rats fed high-DHA through gestation and lactation, ABR was shorter in juvenile rats fed high-DHA diets only after birth than rats fed ARA + DHA. Further studies are needed to understand the relationship between dietary DHA, norepinephrine, and auditory system development over a range of DHA intakes and discrete periods of development.

Mild carbon monoxide exposure and auditory function in the developing rat

We have examined the influence of chronic mild exposure to carbon monoxide (CO) on cognitive (learning) and auditory function in the developing rat. We have demonstrated that the auditory pathway is compromised at exposures less than 50 ppm, whereas learning was not influenced at 100 ppm. Artificially reared rat pups were exposed to CO during the brain growth spurt and onset of myelination. Spatial learning was assessed using the Morris Water Maze and three tests of auditory function: (1) auditory brainstem conduction times; (2) the amplitude of the eighth nerve's action potential; and (3) otoacoustic emissions carried out on rat pups (age 22- 24 days). The pups were gastrostomy-reared on a rat milk substitute and chronically exposed to CO at discrete concentrations in the range of 12-100 ppm from 6 days of age to post-weaning at 21-23 days of age. We found no difference in auditory brainstem conduction times at all CO concentrations in comparison to non-exposed controls. There was a difference in otoacoustic emissions for test and controls at CO concentrations of 50 ppm but not at lower concentrations. There was a consistent attenuation of the amplitude of the eighth nerve's action potential, even at the lowest CO exposure examined. The attenuation of the amplitude of the action potential of the eighth nerve at 50 ppm carbon monoxide exposure did not completely recover by 73 days of age. We conclude that prolonged mild exposure to carbon monoxide during development causes measurable functional changes at the level of the eighth cranial nerve.

Recovery of brain docosahexaenoate leads to recovery of spatial task performance

Infants fed vegetable oil-based formulas may have poorer visual function, lower cognitive scores and acquire learning tasks more slowly in comparison with those breast fed or those fed formulas supplemented with docosahexaenoate. The aim of the present study was to determine the reversibility of losses in brain function associated with the loss of brain DHA. Rats were fed very low or adequate levels of n-3 fatty acids through three generations. The n-3 fatty acid deficient animals of the F3 generation were then given an n-3 adequate diet containing alpha-linolenic and docosahexaenoic acids (DHA) at birth, weaning (3 weeks) or young adulthood (7 weeks). The spatial task performance of these animals returned to the n-3 adequate diet was then compared using the Morris water at two different ages, at 9 or 13 weeks. Our results indicate that animals repleted since birth or at weaning were able to achieve nearly the same level of brain DHA and spatial task performance as animals maintained for three generations on an n-3 adequate diet. In the case of young adult animals, the degree of DHA and behavioral performance recovery depended upon the duration of dietary repletion with substantial recovery in animals after 6 weeks but little recovery of function after two weeks. The significance of these findings is that they indicate that at least some of the adverse effects of DHA deficiency during neurodevelopment may be reversible with an n-3 fatty acid supplemented diet.

Higher maternal plasma docosahexaenoic acid during pregnancy is associated with more mature neonatal sleep-state patterning

BACKGROUND

The effect of docosahexaenoic acid (DHA) on the developing fetal central nervous system (CNS) and related functional outcomes in infancy remain unexplored. Sleep and wake states of newborns provide a tool for assessing the functional integrity of the CNS.

OBJECTIVE

We investigated whether CNS integrity in newborns, measured with sleep recordings, was associated with maternal concentrations of long-chain polyunsaturated fatty acids, especially DHA.

DESIGN

Plasma phospholipid fatty acid concentrations were measured in 17 women at parturition. On postpartum day 1 (P1) and day 2 (P2), a pressure-sensitive pad under the infants' bedding recorded body movements and respiratory patterns to measure sleep and wake states.

RESULTS

Maternal plasma phospholipid DHA ranged from 1.91% to 4.5% by wt of total fatty acids. On the basis of previously published data and the median DHA concentration, the women were divided into 2 groups: high DHA (> 3.0% by wt of total fatty acids) and low DHA (</= 3.0% by wt of total fatty acids). Infants of high-DHA mothers had a significantly lower ratio of active sleep (AS) to quiet sleep (QS) and less AS than did infants of low-DHA mothers. Furthermore, the former infants had less sleep-wake transition and more wakefulness on P2. Correlations of maternal DHA status with infant sleep states were consistent with these data. Also, the ratio of maternal n-6 to n-3 fatty acids on P1 was inversely associated with QS and positively associated with arousals in QS. On P2, maternal n-6:n-3 was positively associated with AS, sleep-wake transition, and AS:QS.

CONCLUSION

The sleep patterns of infants born to mothers with higher plasma phospholipid DHA suggest greater CNS maturity.

Maternal dietary docosahexanoic acid content affects the rat pup auditory system

Previous studies of the effects of dietary docosahexanoic acid (DHA), 22:6n3, on neurodevelopment have focused mainly on visual-evoked potentials and indices of visual activity, measures that may be confounded by effects on the retina rather than on neural pathways. We investigated the effect of pre- and postnatal maternal dietary DHA content on auditory brainstem conduction times (ABCTs), the appearance of the auditory startle reflex (ASR), and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) activity in brainstem homogenates. Timed pregnant dams were fed, beginning on day 2 of gestation and throughout lactation, a purified diet containing one of three levels of DHA (0, 1, or 3% of total fatty acids, or 0, 0.4 or 1.2% of total energy). On postnatal day (PND) 3, pups were randomly crossfostered within diet groups to minimize litter effects and culled to 10 per litter. Cerebrums and milk from culled pups stomachs were collected for lipid analysis. The timing of appearance of the ASR was determined between PND 10 through 14 and ABCTs were measured in pups on PND 24 and 31. Pups were sacrificed on PND 31 and cerebrums were removed. In each of two replicated studies, pups in the 1% DHA group weighed significantly less on PND 3 and they gained significantly less weight from PND 3 to 31 compared with pups in the 0 or 3% groups (p<0.01). The auditory studies were not conducted on the 1% DHA group since measures of auditory function are in part a function of somatic growth. The tissue fatty acid data for the 1% DHA group did not show unexpected findings. Higher dietary DHA was reflected in milk and pup cerebrums, and levels of arachidonic acid were inversely related to levels of DHA. In the pups of dams fed diets containing 3% versus 0% DHA, the ASR appeared significantly later (p<0.001) and the ABCTs were longer (p<0.05) on PND 31. CNPase activity levels were not different between the 0 and 3% DHA groups. This study demonstrated that the auditory brainstem response is sensitive for identifying effects of diet on neurodevelopment, and that diets supplemented with high levels of DHA may exert a negative influence on central nervous system development, potentially through effects on myelin. This study suggests the need for further studies of pre- and postnatal long chain polyunsaturated fatty acid dietary supplementation.