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

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.

Association of Audiometric Measures with plasma long chain polyunsaturated fatty acids in a high-fish eating population: The Seychelles Child Development Study

OBJECTIVES

To determine if auditory function is associated with current long chain polyunsaturated fatty acids (LCPUFA) concentrations in a cohort of young adults who consume oceanic fish with naturally acquired methylmercury (MeHg). We measured participants plasma LCPUFA concentrations (total n-3, total n-6 and the n-6:n-3 ratio) and looked for an association with Auditory Brain Response (ABR) latencies and Otoacoustic Emissions (OAE) amplitudes.

DESIGN

Auditory function of 534 participants from the Seychelles Child Development Study (SCDS) main cohort was examined at 19 years of age. Tests included standard pure-tone audiometry, tympanometry, ABR and both Click-Evoked OAE (CEOAE) and Distortion-Product OAE (DPOAE). Associations of LCPUFA status, measured at the time of examination, and auditory outcomes were examined using covariate-adjusted linear regression models. All models were adjusted for sex, prenatal and current MeHg exposure and hearing status.

RESULTS

LCPUFA concentrations were similar for both sexes and when comparing participants with normal hearing (90.4 %) to those who had a sensorineural hearing loss in one or both ears (9.6 %). When looking at a subset of only hearing impaired participants, LCPUFA concentrations were similar in those participants who had a mild sensorineural hearing loss as compared with participants that had a moderate sensorineural hearing loss. LCPUFA concentrations were not correlated with current hair MeHg. LCPUFA concentrations were statistically significantly associated with only 6 of 174 ABR and OAE endpoints examined. Four of the 6 significant associations were present in only one sex. In female participants as n-6 concentrations increased, the ABR wave I absolute latency increased for a 60 dBnHL 19 click/sec stimulus. For male participants the interwave I-III latencies for a 60 dBnHL 69 clicks/sec stimulus increased as the n-6:n-3 LCPUFA ratio increased and the interwave I-V interval decreased for a 60 dBnHL 39 clicks/sec stimulus as the n-6 concentration increased. For both sexes interwave latencies were prolonged for the III-V interwave interval for an 80 dBnHL 39 clicks/sec as n-3 LCPUFA concentration increased. As the n-3 LCPUFA concentrations increased, the amplitude of the 6000 Hz DPOAE in the right ear increased for both sexes. As the n-6:n-3 ratio increased, the amplitude of the 1500 Hz DPOAE in the left ear decreased for females. The amplitude of the CEOAE was not associated with n-3, n-6 LCPUFA concentrations or the n-6:n-3 ratio.

CONCLUSION

There was no evidence to suggest LCPUFA status was associated with hearing acuity, ABR latencies or OAE amplitudes, even though our participants tended to have higher LCPUFA concentrations as compared to individuals consuming a more western diet. No association was observed between LCPUFA status and a participants hearing status (normal hearing or hearing loss). Although we found a few associations between current plasma LCPUFA status and ABR and OAE auditory endpoints examined, no clear pattern exists. Some of these associations would be considered detrimental resulting in prolonged ABR latencies or smaller OAE amplitudes, while others would be considered beneficial resulting in shortened ABR latencies or larger OAE amplitudes.

Effects of dietary omega-3 PUFAs on growth and development: Somatic, neurobiological and reproductive functions in a murine model

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) are relevant to fetal and infant growth and development. Objective: to assess whether long-term exposure to dietary ω-3 PUFA imbalance alters pre- and/or postnatal pups' development and reproductive function later in life. Mice dams were fed with ω-3 PUFA Control (soybean oil, 7%), Deficient (sunflower oil, 7%) or Excess (blend oil; 4.2% cod-liver+2.8% soybean) diet before conception and throughout gestation-lactation and later on, their pups received the same diet from weaning to adulthood. Offspring somatic, neurobiological and reproductive parameters were evaluated. Excess pups were lighter during the preweaning period and shorter in length from postnatal day (PND) 7 to 49, compared to Control pups (P<.05). On PND14, the percentage of pups with eye opening in Excess group was lower than those from Control and Deficient groups (P<.05). In Excess female offspring, puberty onset (vaginal opening and first estrus) occurred significantly later and the percentage of parthenogenetic oocytes on PND63 was higher than Control and Deficient ones (P<.05). Deficient pups were shorter in length (males: on PND14, 21, 35 and 49; females: on PND14, 21 and 42) compared with Control pups (P<.05). Deficient offspring exhibited higher percentage of bending spermatozoa compared to Control and Excess offspring (P<.05). These results show that either an excessively high or insufficient ω-3 PUFA consumption prior to conception until adulthood seems inadvisable because of the potential risks of short-term adverse effects on growth and development of the progeny or long-lasting effects on their reproductive maturation and function.

Cochlear Homocysteine Metabolism at the Crossroad of Nutrition and Sensorineural Hearing Loss

Hearing loss (HL) is one of the most common causes of disability, affecting 360 million people according to the World Health Organization (WHO). HL is most frequently of sensorineural origin, being caused by the irreversible loss of hair cells and/or spiral ganglion neurons. The etiology of sensorineural HL (SNHL) is multifactorial, with genetic and environmental factors such as noise, ototoxic substances and aging playing a role. The nutritional status is central in aging disability, but the interplay between nutrition and SNHL has only recently gained attention. Dietary supplementation could therefore constitute the first step for the prevention and potential repair of hearing damage before it reaches irreversibility. In this context, different epidemiological studies have shown correlations among the nutritional condition, increased total plasma homocysteine (tHcy) and SNHL. Several human genetic rare diseases are also associated with homocysteine (Hcy) metabolism and SNHL confirming this potential link. Accordingly, rodent experimental models have provided the molecular basis to understand the observed effects. Thus, increased tHcy levels and vitamin deficiencies, such as folic acid (FA), have been linked with SNHL, whereas long-term dietary supplementation with omega-3 fatty acids improved Hcy metabolism, cell survival and hearing acuity. Furthermore, pharmacological supplementations with the anti-oxidant fumaric acid that targets Hcy metabolism also improved SNHL. Overall these results strongly suggest that cochlear Hcy metabolism is a key player in the onset and progression of SNHL, opening the way for the design of prospective nutritional therapies.

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.

Lutein and zeaxanthin status and auditory thresholds in a sample of young healthy adults

OBJECTIVES

Dietary carotenoids lutein (L) and zeaxanthin (Z) have been linked to improved visual and cognitive function. These effects are thought to be mediated by the presence of these pigments in critical regions of the retina and brain. There, it has been postulated that L and Z mediate improved performance by enhancing neural efficiency. The auditory system also relies on efficient segregating of signals and noise and LZ are also found in the auditory cortex. The purpose of the present study was to investigate the influence of LZ status (as assessed by the measuring levels in retina) on auditory thresholds in young non-smokers (N = 32, M = 20.72 ± 3.28 years).

DESIGN

LZ status was determined by measuring macular pigment (MP) optical density using a standardized psychophysical technique (customized heterochromatic flicker photometry). Auditory thresholds were assessed with puretone thresholds and puretone auditory thresholds in white noise.

RESULTS

MP density was related to many, but not all, of the puretone thresholds we tested: 250 Hz (F(6,32) = 4.36, P < 0.01), 500 Hz (F(6,32) = 2.25, P < 0.05), 1000 Hz (F(6,32) = 3.22, P < 0.05), and 6000 Hz (F(6,32) = 2.56, P < 0.05).

CONCLUSION

The overall pattern of results is consistent with a role for L and Z in maintaining optimal auditory function.

Long-term omega-3 fatty acid supplementation prevents expression changes in cochlear homocysteine metabolism and ameliorates progressive hearing loss in C57BL/6J mice

Omega-3 polyunsaturated fatty acids (PUFAs) are essential nutrients well known for their beneficial effects, among others on cognitive development and maintenance, inflammation and oxidative stress. Previous studies have shown an inverse association between high plasma levels of PUFAs and age-related hearing loss, and the relationship between low serum folate and elevated plasma homocysteine levels and hearing loss. Therefore, we used C57BL/6J mice and long-term omega-3 supplementation to evaluate the impact on hearing by analyzing their auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) thresholds. The omega-3 group showed significantly lower ABR hearing thresholds (~25 dB sound pressure level) and higher DPOAE amplitudes in mid-high frequencies when compared to the control group. These changes did not correlate with alterations between groups in plasma homocysteine or serum folate levels as measured by high-performance liquid chromatography and a microbiological method, respectively. Aging in the control group was associated with imbalanced cytokine expression toward increased proinflammatory cytokines as determined by quantitative reverse transcriptase polymerase chain reaction; these changes were prevented by omega-3 supplementation. Genes involved in homocysteine metabolism showed decreased expression during aging of control animals, and only alterations in Bhmt and Cbs were significantly prevented by omega-3 feeding. Western blotting showed that omega-3 supplementation precluded the CBS protein increase detected in 10-month-old controls but also produced an increase in BHMT protein levels. Altogether, the results obtained suggest a long-term protective role of omega-3 supplementation on cochlear metabolism and progression of hearing loss.

Effects of Fish Oil Supplementation during the Suckling Period on Auditory Neural Conduction in n-3 Fatty Acid-Deficient Rat Pups

INTRODUCTION

Omega-3 fatty acid, particularly in the form of fish oil, has a structural and biological role in various systems of the body. The auditory and nervous systems are both influenced by omega-3 fatty acids, with omega-3 deficiency having devastating effects on both systems. Numerous studies have attempted to investigate this further. This study aimed to evaluate neural conduction in n-3 fatty acid-deficient rat pups following supplementation with fish oil during the suckling period.

MATERIALS AND METHODS

In this interventional and experimental study, omega-3 fatty acids from fish oil (FO) were fed to rat pups of n-3 polyunsaturated fatty acid (PUFA)-deficient dams. Changes in auditory neural conduction were compared with those of control and n-3 PUFA-deficient groups using auditory brainstem response (ABR). The parameters of interest were P1, P3, and P4 absolute latency, P1-P3, P1-P4, and P3-P4 interpeak latency (IPL), and P4/P1 amplitude ratio. The rat pups were given oral FO, 5 ml/g weight for 17 days, between the age of 5 and 21 days.

RESULTS

No significant group differences were observed in P1 and P3 absolute latency (P>0.05), but there was a significant difference in P4 (P≤0.05). The n-3 PUFA-deficient + vehicle group had the most prolonged (the worst) P1-P4 IPL and P3-P4 IPL compared with control and n-3 PUFA-deficient + FO groups. There was no significant difference in P1-P4 IPL and P3-P4 IPL between the n-3 PUFA-deficient + FO group and the control group (P>0.05). There was a significant effect of diet on P1-P4 IPL and P3-P4 IPL between groups (P≤0.05).

CONCLUSION

The results of present study showed the effect of omega-3 deficiency on auditory neural structure during pregnancy and the lactation period. Additionally, we observed reduced reduction in devastating effects on neural conduction in n-3 fatty acid-deficient rat pups following the supplementation of FO during the suckling period.

Wistar rats: a forgotten model of age-related hearing loss

Age-related hearing loss (ARHL) is one of the most frequent sensory impairments in senescence and is a source of important socio-economic consequences. Understanding the pathological responses that occur in the central auditory pathway of patients who suffer from this disability is vital to improve its diagnosis and treatment. Therefore, the goal of this study was to characterize age-related modifications in auditory brainstem responses (ABR) and to determine whether these functional responses might be accompanied by an imbalance between excitation and inhibition in the cochlear nucleus of Wistar rats. To do so, ABR recordings at different frequencies and immunohistochemistry for the vesicular glutamate transporter 1 (VGLUT1) and the vesicular GABA transporter (VGAT) in the ventral cochlear nucleus (VCN) were performed in young, middle-aged and old male Wistar rats. The results demonstrate that there was a significant increase in the auditory thresholds, a significant decrease in the amplitudes and an increase in the latencies of the ABR waves as the age of the rat increased. Additionally, there were decreases in VGLUT1 and VGAT immunostaining in the VCN of older rats compared to younger rats. Therefore, the observed age-related decline in the magnitude of auditory evoked responses might be due in part to a reduction in markers of excitatory function; meanwhile, the concomitant reduction in both excitatory and inhibitory markers might reflect a common central alteration in animal models of ARLH. Together, these findings highlight the suitability of the Wistar rat as an excellent model to study ARHL.

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.

Normal variations in the morphology of auditory brainstem response (ABR) waveforms: a study in Wistar rats

Auditory brainstem evoked responses (ABR) have been used for decades to assess auditory function. Surprisingly, despite the fact that rats are one of the most widely used experimental models in hearing, there have been no studies that have characterized in detail the normal morphological variations that occur in ABR waves. Therefore, the goal of this study was to characterize the patterns of ABR waves in rats to establish baseline criteria that could be used to identify abnormalities. Rats were stimulated with pure tone sounds at different frequencies and ABR waves were classified based on morphology. The most definitive finding was that, unlike what is observed in human ABRs, wave II of the rat ABR was the most prominent. Additionally, wave III was the smallest and, in many cases, was not apparent at low frequencies. Wave III was frequently involved in the formation of complexes, often appearing as a small wave or adjoining primarily wave IV. Complexes were common at low and medium frequencies and rare at high frequencies. These results indicate that knowledge of the different wave patterns in normal rats is fundamental to understanding how the wave morphology changes in pathological conditions that could lead to hearing impairment.

Repeated antenatal corticosteroid treatments adversely affect neural transmission time and auditory thresholds in laboratory rats

Antenatal corticosteroid (AC) treatment is given to pregnant women at risk for preterm birth to reduce infant morbidity and mortality by enhancing lung and brain maturation. However, there is no accepted regimen on how frequently AC treatments should be given and some studies found that repeated AC treatments can cause growth retardation and brain damage. Our goal was to assess the dose-dependent effects of repeated AC treatment and estimate the critical number of AC courses to cause harmful effects on the auditory brainstem response (ABR), a sensitive measure of brain development, neural transmission and hearing loss. We hypothesized that repeated AC treatment would have harmful effects on the offspring's ABRs and growth only if more than 3 AC treatment courses were given. To test this hypothesis, pregnant Wistar rats were given either a high regimen of AC (HAC), a moderate regimen (MAC), a low regimen (LAC), or saline (SAL). An untreated control (CON) group was also used. Simulating the clinical condition, the HAC dams received 0.2mg/kg Betamethasone (IM) twice daily for 6 days during gestation days (GD) 17-22. The MAC dams received 3 days of AC treatment followed by 3 days of saline treatment on GD 17-19 and GD 20-22, respectively. The LAC dams received 1 day of AC treatment followed by 5 days of saline treatment on GD 17 and GD 18-22, respectively. The SAL dams received 6 days of saline treatment from GD 17 to 22 (twice daily, isovolumetric to the HAC injections, IM). The offspring were ABR-tested on postnatal day 24. Results indicated that the ABR's P4 latencies (neural transmission time) were significantly prolonged (worse) in the HAC pups and that ABR's thresholds were significantly elevated (worse) in the HAC and MAC pups when compared to the CON pups. The HAC and MAC pups were also growth retarded and had higher postnatal mortality than the CON pups. The SAL and LAC pups showed little or no adverse effects. In conclusion, repeated AC treatment had harmful effects on the rat offspring's ABRs, postnatal growth and survival. The prolonged ABR latencies reflect slowed neural transmission times along the auditory nerve and brainstem auditory pathway. The elevated ABR thresholds reflect hearing deficits. We concluded that repeated AC treatment can have harmful neurological, sensory and developmental effects on the rat offspring. These effects should be considered when weighing the benefits and risks of repeated AC treatment and when monitoring and managing the prenatally exposed child for possible adverse effects.

Auditory brainstem response (ABR) abnormalities across the life span of rats prenatally exposed to alcohol

BACKGROUND

Fetal alcohol syndrome (FAS) is a leading cause of neurodevelopmental impairments (NDIs) in developed countries. Sensory deficits can play a major role in NDI, yet few studies have investigated the effects of prenatal alcohol exposure on sensory function. In addition, there is a paucity of information on the lifelong effects of prenatal alcohol exposure. Thus, we sought to investigate the effects of prenatal alcohol exposure on auditory function across the life span in an animal model. Based on prior findings with prenatal alcohol exposure and other forms of adverse prenatal environments, we hypothesized that animals prenatally exposed to alcohol would show an age-dependent pattern of (i) hearing and neurological abnormalities as postweanling pups, (ii) a substantial dissipation of such abnormalities in young adulthood, and (iii) a resurgence of such abnormalities in middle-aged adulthood.

METHODS

Pregnant rats were randomly assigned to an untreated control (CON), a pair-fed control (PFC), or an alcohol-treated (ALC) group. The ALC dams were gavaged with 6 mg/kg alcohol daily from gestation day (GD) 6 to 21. The PFC dams were gavaged daily from GD6 to GD21 with an isocaloric and isovolumetric water-based solution of maltose-dextrins and pair-fed to the ALC dams. The CON dams were the untreated group to which the ALC and CON groups were compared. Hearing and neurological functions in the offspring were assessed with the auditory brainstem response (ABR) at the postnatal ages of 22, 220, and 520 days.

RESULTS

In accord with our hypothesis, ABR abnormalities were first observed in the postweanling pups, largely dissipated in young adulthood, and then resurged in middle-aged adulthood. This age-related pattern suggests that the ALC pups had a developmental delay that dissipated in young adulthood and an enhanced age-related deterioration that occurred in middle-aged adulthood. Such a pattern is consistent with the fetal programming hypothesis of adult-onset diseases (the Barker hypothesis).

CONCLUSIONS

Our findings have important clinical implications for the assessment and management of (i) childhood hearing disorders and their comorbidities (i.e., speech-and-language, learning, and attention deficit disorders) and (ii) enhanced age-related hearing and neurological degeneration in middle-aged adulthood that can result from prenatal alcohol exposure. We recommend hearing evaluation be a part of any long-term follow-up for FAS patients and patients exposed to any adverse prenatal environment.

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.

Developmental and neurobehavioral effects of perinatal exposure to diets with different omega-6:omega-3 ratios in mice

OBJECTIVE

To investigate in mice the effect of diets enriched with soy or sunflower oil with different omega-6:omega-3 ratios on gestation, reproductive success, physical maturation, and the neurobiological development of the pups.

METHODS

Dams were assigned, throughout gestation and lactation, to different groups: a commercial diet (CD), a soy oil-enriched diet (SOD), or a sunflower oil-enriched diet (SFOD). Measurements during gestation were dams' body weights and daily food intakes. Measurements in the offspring were physical parameters (body weight, body length, body mass index, fur appearance, pinna detachment, incisor eruption, eye opening, and puberty onset) and behavioral preweaning tests (surface righting reflex, negative geotaxis, and cliff avoidance).

RESULTS

The SOD and SFOD dams became significantly heavier than the CD dams from gestational days 14 and 19, respectively, to parturition. There were no significant differences in gestational length or food consumption during pregnancy or lactation or in maternal weight during lactation. Diets did not modify litter size, sex ratio, survival index at weaning, or body weight. The SFOD and SOD offspring were significantly shorter than the CD offspring at weaning. The mean offspring physical scores of SOD and SFOD offspring were higher than CD offspring and simple reflexes were earlier in the SOD and SFOD groups. In SFOD offspring, puberty onset was significantly delayed, at postnatal days 26 and 27 in male and female offspring, respectively.

CONCLUSION

This study suggests that the maintenance of an adequate omega-6:omega-3 ratio is necessary for the optimal growth and development of murine offspring. In populations that do not have sufficient provision of polyunsaturated fatty acids in the diet, their consumption would be advisable during gestation and lactation because these improve most neurodevelopmental outcomes included in this study.

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.

Perinatal n-3 fatty acid imbalance affects fatty acid composition in rat offspring

This study was designed to investigate the effects of high and low n-3 FA feeding during perinatal period on the growth and FA profiles in the Wistar rat offspring. Female rats were randomized into three diet groups during pregnancy and lactation (L): Control (CON, ratio of n-3/n-6 approximately 0.14, n=24); n-3 FA deficient (LOW, ratio of n-3/n-6 approximately 0, n=31) and n-3 FA excess (HIGH, ratio of n-3/n-6 approximately 14.0, n=23). Milk samples were obtained on L14. After L24, all offspring were fed the control diet until killed at 23-25 weeks of age. There were no group differences in maternal weight gains or offspring birth weights. After birth, the HIGH offspring weighed the least while CON offspring the most. The FA profiles of the CON and LOW milk resembled CON diet, and the HIGH milk resembled HIGH diet. Body FA profiles of males from all groups were similar to the CON milk profile, but the CON and LOW females resembled the CON milk, while the HIGH females resembled the HIGH milk. All HIGH offspring had increased n-3 levels and n-3/n-6 ratios (males: 0.16+/-0.01; females: 0.23+/-0.06). Thus LOW dams likely had maternal body fat mobilization that compensated for the deficiency in dietary n-3 FA, while a compensatory mechanism was not observed when intake was high. Excess amount of n-3 FA affected female offspring more than males. These data indicate the long-lasting effects of supplementation and supplementing high amounts of n-3 FA during pregnancy and lactation may not be advisable.

[Effects of omega 3 supplementation in pregnant women]

Maternal nutrition is a major environmental factor, which can be modified and can affect fetal growth and development with potential long-term consequences. There is currently a strong mediatic pressure for supplementing diets with omega 3 fatty acids. Nevertheless, if beneficial effects seem to be confirmed in adults and in animal models, the evidence for favourable effects of omega 3 supplementation in pregnant women are less obvious. Indeed, there is a trend showing a positive effect on cerebral development, but long term effects have not been demonstrated and both the quantity of omega 3 and the omega 3:omega 6 ratios are not precisely determined. Numerous studies are needed, both in pregnant animal models and in patients, to unravel these effects.

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.