Long-Term Dietary Folate Deficiency Accelerates Progressive Hearing Loss on CBA/Ca Mice

Association of vitamins with hearing loss, vision disorder and sleep problem in the US general population

Based on nationally representative samples from US, we aimed to assess the associations of vitamins with hearing loss, vision disorder and sleep problem. A total of 25,312, 8425 and 24,234 participants were included in this study to investigate the relationship of vitamins with hearing loss, vision disorder and sleep problem from National Health and Nutrition Examination Survey, respectively. Vitamins including niacin, folic acid, vitamin B6, A, C, E and carotenoids were considered in our study. Logistic regression models were used to assess the associations between all included dietary vitamin intake concentrations and the prevalence of specific outcomes. Increased lycopene (odds ratio [OR]: 0.904, 95% confidence interval [CI]: 0.829-0.985) intake was associated with a deceased prevalence of hearing loss. Higher dietary intake of folic acid (OR: 0.637, 95% CI: 0.443-0.904), vitamin B6 (0.667, 0.465-0.947), alpha-carotene (0.695, 0.494-0.968), beta-carotene (0.703, 0.505-0.969) and lutein + zeaxanthin (0.640, 0.455-0.892) were associated with a decreased prevalence of vision disorder. The inversely associations of sleeping problem with niacin (OR: 0.902, 95% CI: 0.826-0.985), folic acid (0.882, 0.811-0.959), vitamin B6 (0.892, 0.818-0.973), vitamin C (0.908, 0.835-0.987), vitamin E (0.885, 0.813-0.963) and lycopene (0.919, 0.845-0.998) were also observed. Our findings provide evidence that increased specific vitamin intake is associated with decreased prevalence of hearing loss, vision disorder and sleep problem.

Hearing Function and Nutritional Status in Aviation Pilots from Spain Exposed to High Acoustic Damage

Noise-induced hearing loss is the most frequent and preventable occupational disease. Aviation pilots are a vulnerable population, as they spend many hours exposed to noise pollution in their working environment. Different studies suggest that certain dietary compounds may play a key role in the etiology and prevention of this pathology. We aimed to study the relationship linking auditory function, dietary intake, and some serum biomarkers in pilots, exposed to noise in the work environment. A total of 235 pilots, who undergo a periodic medical examination at the Centro de Instrucción de Medicina Aeroespacial (Madrid, SPAIN), were evaluated. Auditory function was assessed by tonal audiometry. Energy and nutrient intakes were estimated by 24 h recall (DIALTM program). Serum homocysteine (Hcy) was determined in a Cobas 6000TM multi-analyzer while folate, vitamin B12, and D were analyzed in a Cobas e411TM. The prevalence of hearing loss (HL) was 64.3%. HL was significantly related to age (r = 0.588, p ≤ 0.001) and flight hours (r = 0.283, p ≤ 0.001). A multiple linear regression model was used to assess the relationship among HL, flight hours, serum folate, and Hcy serum levels. HL was significantly (p < 0.050) associated with flight hours (β = 0.246), serum folate (β = −0.143), and serum Hcy (β = 0.227). Nutritional interventions would be of great interest to monitor and slow down the HL progression in populations exposed to noise pollution in their workplace.

Folate Deficiency Increased Lipid Accumulation and Leptin Production of Adipocytes

Imbalanced dietary habits are closely associated with poor micronutrients status and the development of obesity. Previous studies have shown that serum folate level is decreased in obese individuals. However, whether folate deficiency could result in adiposity is still unclear. The aim of this study was to investigate the effects of dietary folate on lipid accumulation and leptin production using both in vivo and in vitro studies. Male C57BL/6 mice were fed with a diet with (f1) or without (f0) folate in a high-fat (HF) diet containing high-sucrose (HFS-f1, HFS-f0) for 4.5-5 months in Experiment 1, or an HF diet (HF-f1, HF-f0) for 12 months in Experiment 2, or an HF diet containing high-fructose (HFF-f1, HFF-f0) for 12 months in Experiment 3, compared with the normal-fat (NF-f1, NF-f0) diet, respectively. The serum levels of folate and leptin, white adipose tissue (WAT), size of adipocytes, hepatic contents of triglyceride (TG), and cholesterol were measured. In vitro study, TG contents, proinflammatory cytokines, leptin, and expressions of hypoxia-inducible factor (HIF)-1α and lipogenesis-related genes of 3T3-L1 adipocytes cultured with (f1) or without (f0) folate were assayed. The results showed that folate deficiency together with a high-fat diet (HFS-f0, HF-f0, HFF-f0) had higher WAT mass, adipocyte size, serum leptin level, and hepatic TG compared to those of the folate-sufficient groups (HFS-f1, HF-f1, and HFF-f1). Folate deficiency with a high-fat high -sucrose or -fructose diet (HFS-f0, HFF-f0) significantly increased the body weight of the mice. Increased intracellular TG, leptin, monocyte chemotactic protein (MCP)-1 and interleukin (IL)-6 levels, and the expression of Hif1α and lipogenesis-related genes Cebpα, Cebpβ, Acc1, Fasn, and Fabp4 were also detected in folate-deficient 3T3-L1 adipocytes. Our results suggested that folate deficiency increased lipid accumulation and leptin production of adipocytes, and thus, inadequate folate status might be one of the risk factors for adiposity.

Dietary folic acid deficiency impacts hippocampal morphology and cortical acetylcholine metabolism in adult male and female mice

OBJECTIVE

One-carbon (1C) metabolism is a metabolic network that integrates nutritional signals with biosynthesis, redox homeostasis, and epigenetics. There are sex differences in hepatic 1C metabolism, however, it is unclear whether sex differences in 1C impact the brain. The aim of this study was to investigate if sex modulates the effects of dietary folic acid deficiency, the main component of 1C, in brain tissue using a mouse model.

METHODS

Male and female C57Bl/6J mice were placed on a folic acid deficient (FD) or control diet (CD) at six weeks until six months of aged. After which brain tissue and serum were collected for analysis. In brain tissue, hippocampal volume, morphology, and apoptosis as well as cortical acetylcholine metabolism were measured.

RESULTS

Male and female FD mice had reduced serum levels of folate. Both males and females maintained on a FD showed a decrease in the thickness of the hippocampal CA1-CA3 region. Interestingly, there was a sex difference in the levels of active caspase-3 within the CA3 region of the hippocampus. In cortical tissue, there were increased levels of neuronal ChAT and reduced levels of AChE in FD females and male mice.

CONCLUSIONS

The results indicated that FD impacts hippocampal morphology and cortical neuronal acetylcholine metabolism. The data from our study indicate that there was only one sex difference and that was in hippocampal apoptosis. Our study provides little evidence that sex modulates the effects of dietary folate deficiency on hippocampal morphology and cortical neuronal acetylcholine metabolism.

Effect of Malnutrition on Hearing Loss in Children

OBJECTIVE

To characterize the relation between protein-calorie malnutrition (PCM) and hearing loss (HL) in children.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral hospital.

PATIENTS

Children in the Audiological and Genetic Database with a diagnosis of protein-calorie malnutrition, marasmus, and/or kwashiorkor.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Prevalence, type, severity (4-tone pure-tone average, PTA), and progression of HL.

RESULTS

Of 770 children with PCM, 57.8% had HL, compared to 45.5% of children without PCM (p < 0.001). Severely malnourished children had significantly higher odds of moderate-profound HL (aOR 2.27, 95% CI 1.47-3.43), high-frequency HL (aOR 1.82, 95% CI 1.21-2.75), and sensorineural or mixed HL (aOR 1.60, 95% CI 1.05-2.41) compared to children without PCM. Severely malnourished children had significantly worse initial (35.0 dB vs 25.0 dB, p < 0.001), and final median PTA (31.3 dB vs 20.0 dB, p < 0.001) compared to children without PCM. Additionally, HL in children who were moderately and severely malnourished was significantly less likely to improve (aOR 0.47, 95% CI 0.25-0.82 and aOR 0.4, 95% CI 0.2-0.9) when compared to those without PCM.

CONCLUSIONS

Given the greater prevalence and severity of hearing loss, children with PCM should be considered an at-risk group for poor audiological outcomes, and clinical practice should focus on early treatment and intervention for malnourished children. Routine audiological evaluation should be considered in this population.

Vestibular Evoked Myogenic Potentials in Patients With Low Vitamin B12 Levels

OBJECTIVE

Vitamin B12 deficiency-induced hyperhomocysteinemia has been associated with impaired microarterial flow, demyelization, and neuronal damage, resulting in cochlear damage and auditory dysfunction. Therefore, we aimed to evaluate the possible vestibular-evoked myogenic potential (VEMP) abnormalities in patients with vitamin B12 deficiency.

MATERIAL AND METHOD

In this prospective study, 37 patients diagnosed with vitamin B12 deficiency (<220 pg/mL) were compared with 31 audiologically healthy participants with normal B12 levels. Burst-evoked cervical VEMP (cVEMP) measurements were performed on all participants. Additionally, cVEMP responses were analyzed for P1-N1 latency, interpeak amplitude, and amplitude asymmetry ratio. The results of audiometric examination and VEMP records as well as absent responses were evaluated and compared between groups.

RESULTS

The rate of absent VEMP responses was twice as high in the patient group than in the healthy control group (12 vs 6 cases, respectively). Moreover, the mean values of interpeak amplitude in both right and left ears were statistically shorter in the patient group than the control group (P values = .024 and .007, respectively). Similarly, the mean amplitude asymmetry ratio was statistically higher in the patient group than the control group (P = .050). There were no statistically significant differences in latency responses between groups. Furthermore, positive, statistically significant correlation was detected between values of the left P1-N1 interpeak amplitude and vitamin B12 levels (r = 0.287, P = .037).

CONCLUSIONS

Increased rates of absent VEMPs and decreased amplitudes with normal latencies are attributed to peripheral vestibular hypofunction in patients with vitamin B12 deficiency.

Betaine-homocysteine S-methyltransferase deficiency causes increased susceptibility to noise-induced hearing loss associated with plasma hyperhomocysteinemia

Betaine-homocysteine S-methyltransferases (BHMTs) are methionine cycle enzymes that remethylate homocysteine; hence, their malfunction leads to hyperhomocysteinemia. Epidemiologic and experimental studies have revealed a correlation between hyperhomocysteinemia and hearing loss. Here, we have studied the expression of methionine cycle genes in the mouse cochlea and the impact of knocking out the Bhmt gene in the auditory receptor. We evaluated age-related changes in mouse hearing by recording auditory brainstem responses before and following exposure to noise. Also, we measured cochlear cytoarchitecture, gene expression by RNA-arrays and quantitative RT-PCR, and metabolite levels in liver and plasma by HPLC. Our results indicate that there is an age-dependent strain-specific expression of methionine cycle genes in the mouse cochlea and a further regulation during the response to noise damage. Loss of Bhmt did not cause an evident impact in the hearing acuity of young mice, but it produced higher threshold shifts and poorer recovery following noise challenge. Hearing loss was associated with increased cochlear injury, outer hair cell loss, altered expression of cochlear methionine cycle genes, and hyperhomocysteinemia. Our results suggest that BHMT plays a central role in the homeostasis of cochlear methionine metabolism and that Bhmt2 up-regulation could carry out a compensatory role in cochlear protection against noise injury in the absence of BHMT.-Partearroyo, T., Murillo-Cuesta, S., Vallecillo, N., Bermúdez-Muñoz, J. M., Rodríguez-de la Rosa, L., Mandruzzato, G., Celaya, A. M., Zeisel, S. H., Pajares, M. A., Varela-Moreiras, G., Varela-Nieto, I. Betaine-homocysteine S-methyltransferase deficiency causes increased susceptibility to noise-induced hearing loss associated with plasma hyperhomocysteinemia.

Interplay between Nutrition and Hearing Loss: State of Art

Hearing loss has been recently ranked as the fifth leading cause of years lived with disability, ahead of many other chronic diseases such as diabetes, dementia, or chronic obstructive pulmonary disease. Moreover, according to the World Health Organization, moderate-to-profound hearing loss affects about 466 million people worldwide. Its incidence varies in each population segment, affecting approximately 10% of children and increasing to 30% of the population over 65 years. However, hearing loss receives still very limited research funding and public awareness. This sensory impairment is caused by genetic and environmental factors, and among the latter, the nutritional status has acquired relevance due its association to hearing loss detected in recent epidemiological studies. Several experimental models have proved that the onset and progression of hearing loss are closely linked to the availability of nutrients and their metabolism. Here, we have reviewed studies focused on nutrient effects on auditory function. These studies support the potential of nutritional therapy for the protection against hearing loss progression, which is especially relevant to the aging process and related quality of life.

Mammalian Sulfur Amino Acid Metabolism: A Nexus Between Redox Regulation, Nutrition, Epigenetics, and Detoxification

SIGNIFICANCE

Transsulfuration allows conversion of methionine into cysteine using homocysteine (Hcy) as an intermediate. This pathway produces S-adenosylmethionine (AdoMet), a key metabolite for cell function, and provides 50% of the cysteine needed for hepatic glutathione synthesis. The route requires the intake of essential nutrients (e.g., methionine and vitamins) and is regulated by their availability. Transsulfuration presents multiple interconnections with epigenetics, adenosine triphosphate (ATP), and glutathione synthesis, polyol and pentose phosphate pathways, and detoxification that rely mostly in the exchange of substrates or products. Major hepatic diseases, rare diseases, and sensorineural disorders, among others that concur with oxidative stress, present impaired transsulfuration. Recent Advances: In contrast to the classical view, a nuclear branch of the pathway, potentiated under oxidative stress, is emerging. Several transsulfuration proteins regulate gene expression, suggesting moonlighting activities. In addition, abnormalities in Hcy metabolism link nutrition and hearing loss.

CRITICAL ISSUES

Knowledge about the crossregulation between pathways is mostly limited to the hepatic availability/removal of substrates and inhibitors. However, advances regarding protein-protein interactions involving oncogenes, identification of several post-translational modifications (PTMs), and putative moonlighting activities expand the potential impact of transsulfuration beyond methylations and Hcy.

FUTURE DIRECTIONS

Increasing the knowledge on transsulfuration outside the liver, understanding the protein-protein interaction networks involving these enzymes, the functional role of their PTMs, or the mechanisms controlling their nucleocytoplasmic shuttling may provide further insights into the pathophysiological implications of this pathway, allowing design of new therapeutic interventions. Antioxid. Redox Signal. 29, 408-452.

Erythrocyte folate, serum vitamin B12, and hearing loss in the 2003-2004 National Health And Nutrition Examination Survey (NHANES)

BACKGROUND/OBJECTIVES

Studies based on food frequency questionnaires suggest that folate and vitamin B12 intake could protect against hearing loss. We investigated whether erythrocyte folate and serum vitamin B12 levels are independently associated with hearing loss in humans.

SUBJECTS/METHODS

Participants in the 2003-2004 US National Health and Nutrition Examination Survey who had data on hearing, folate, and vitamin B12 levels were included. Pure-tone average (PTA) at 0.5, 1.0, 2.0, and 4.0 kHz was computed for each ear. We used weighted logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the relation between quartiles of folate and vitamin B12, and hearing loss (present if PTA > 25 dB in either ear and absent if PTA ≤ 25 dB in both ears).

RESULTS

Participants (n = 1149) were 20-69 (mean 42) years old and 16.4% had hearing loss in at least one ear. Our data suggest a U-shaped relationship between folate and hearing loss. Compared to the 1st quartile, the ORs (95% CIs) for hearing loss were 0.87 (0.49-1.53), 0.70 (0.49-1.00), and 1.08 (0.61-1.94) for the 2nd, 3rd, and 4th quartile of erythrocyte folate in analyses adjusted for age, sex, vitamin B12, smoking, alcohol use, body mass index, race/ethnicity, exposure to noise, income, and education. Although we observed inverse associations between vitamin B12 and hearing loss, the associations were not statistically significant (P > 0.05).

CONCLUSIONS

Our data show a U-shaped relationship between erythrocyte folate levels and hearing loss, suggesting a need to evaluate whether optimizing blood folate levels could prevent hearing loss.

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.