The Relationship Between Menopause and Dysphagia: A Scoping Review

Purpose

Menopause marks the end of fertility and rapid decline of ovarian hormones in the female body, which corresponds to a myriad of changes to bodily systems, including the upper aerodigestive tract. Despite substantial evidence that menopause negatively impacts oral health, bones, and skeletal muscles, little research has examined these effects as they relate to swallowing. The purpose of this scoping review was to compile and summarize the existing literature investigating the relationship between menopause and swallowing-related structures and physiology.

Methods

Search terms were selected for three databases (PubMed, Scopus, and CINAHL) to gather relevant literature evaluating the relationship between menopause and swallowing-related anatomy as well as swallowing functions in both human and animal models. Relevant articles were reviewed, collated, and summarized to synthesize findings, identify gaps in the literature, and provide suggestions for future directions.

Results

This scoping review yielded 204 studies with the majority of these studies relating to one or more of the following categories: oral health, saliva, mandibular structures, and taste. Common oral symptoms reported in the literature included xerostomia, hyposalivation, tooth decay, inflammation of oral mucosa, and oral pain. Although literature supports that menopause adversely affects oral health, saliva, mandibular structures, and alters taste, a dearth of information was evident regarding how these hormone-dependent changes can adversely affect swallowing.

Conclusions

The relationship between menopause and swallowing has been overlooked by field of speech-language pathology. By identifying the major gaps in the literature, these results will inform future investigations evaluating relationships among ovarian hormones and swallowing.

Pro-neurocognitive and anti-sarcopenic benefits of one-year metformin therapy in ovariectomized aged mice

Health promotion and healthy nutrition significantly increased life expectancy around the world. Aging is associated with an increase in age-related diseases. The use of metformin (Met) as an anti-aging drug has recently been proposed based on its widespread use in clinical practice. Reports have shown that Met acts as an anti-aging agent. In this study, the effects of long-term, 1 year, Met administration on aging-related behaviors and longevity in ovariectomized mice was studied. Met (1 and 10 mg/kg, daily) was administered orally in ovariectomized mice. The anxiety-like behavior, working memory, and physical strength were measured through elevated plus maze, Y-maze, vertical grid holding, and the obligatory swimming capacity tests. Brains were harvested to measure brain-derived neurotrophic factor (BDNF) level. Also, the Kaplan-Meier survival curves were used to show differences and similarities in survival patterns. Met (10 mg/kg) decreased anxiety-like behaviors as well as increased muscle strength and working memory in the ovariectomized mice. Moreover, Met increased the physical strength and longevity as well as the level of BDNF in the ovariectomized mice. Our results indicate that Met administration can be an effective strategy for having a healthy aging in the absence of female gonadal hormones and reverses deleterious effects of ovariectomy-induced aging possibly through BDNF.

Impact of Gender and Age on Rapid Eye Movement-Related Obstructive Sleep Apnea: A Clinical Study of 3234 Japanese OSA Patients

Rapid eye movement (REM)-related obstructive sleep apnea (OSA) is characterized by apnea and hypopnea events due to airway collapse occurring predominantly or exclusively during REM sleep. Previous studies have reported that REM-related OSA occurs more commonly in women and younger individuals. However, external validity of this tendency has not been confirmed in a large clinical sample. The objective of this study was to evaluate the effect of gender and age on REM-related OSA after adjustment for several covariates based on their established clinical relationships to gender difference in OSA. A total of 3234 Japanese patients with OSA were enrolled in this study. We confirmed that female sex is an important risk factor for REM-related OSA, as reported by previous studies. Moreover, we showed that women aged over 50 years were at a greater risk than those aged under 50 years. These results suggest that hormonal changes in women might play an important role in REM-related OSA and might reflect its unknown pathophysiological characteristics.

Effects of Huperzin-A on the Beta-amyloid accumulation in the brain and skeletal muscle cells of a rat model for Alzheimer's disease

AIMS

Alzheimer's Disease (AD) is characterized by a loss of cognitive function and also the accumulation of β-amyloid peptide (βAP) in the brain parenchyma, which plays an important role in this disease. However, it is often also associated with the non-cognitive symptoms such as loss of muscle function (Inclusion-Body Myositis-IBM).

MAIN METHODS

Sprague-Dawley rats (13 weeks-n=68) were randomly assigned into five groups: Group C: Control; Group D: d-galactose; Group O+D: Bilateral oophorectomy+d-galactose; Group O: Bilateral oophorectomy; Group O+D+H: Bilateral oophorectomy+d-galactose+Hup-A. Tissue fixation was performed with the perfusion method. The Compound Muscle Action Potential (CMAP) and mechanical muscle activity were recorded using the standard electro-biophysical techniques. Immune staining was performed with specific antibodies, and the pathological changes were examined. RNA was obtained from brain tissue samples with the Trizol Method. Then, the expression data of mature-miRNAs (rno-miR-9-5p, rno-miR-29a-3p, rno-miR-106a-5p, rno-miR-107 and rno-miR-125a-3p), which may be effective in AD, were taken with Real-Time PCR.

KEY FINDINGS

Impairments occurred in behavioral tests of the rats in the O+D group. βAP accumulation and AChE activity increased significantly in the forebrain in the O+D group compared to the C group. It was seen that Huperzine-A (Hup-A) reduced AChE activity and destructed βAP accumulation. There was a significant decrease in the maximum contractile force at different frequencies in the O+D group and in the O group compared to the C group.

SIGNIFICANCE

It was found that Hup-A contributed to the healing process in rats for damage occurring both in the brain and in the neuro-muscular system.

Comparative physiology of vocal musculature in two odontocetes, the bottlenose dolphin (Tursiops truncatus) and the harbor porpoise (Phocoena phocoena)

The mechanism by which odontocetes produce sound is unique among mammals. To gain insight into the physiological properties that support sound production in toothed whales, we examined myoglobin content ([Mb]), non-bicarbonate buffering capacity (β), fiber-type profiles, and myosin heavy chain expression of vocal musculature in two odontocetes: the bottlenose dolphin (Tursiops truncatus; n = 4) and the harbor porpoise (Phocoena phocoena; n = 5). Both species use the same anatomical structures to produce sound, but differ markedly in their vocal repertoires. Tursiops produce both broadband clicks and tonal whistles, while Phocoena only produce higher frequency clicks. Specific muscles examined in this study included: (1) the nasal musculature around the phonic lips on the right (RNM) and left (LNM) sides of the head, (2) the palatopharyngeal sphincter (PPS), which surrounds the larynx and aids in pressurizing cranial air spaces, and (3) the genioglossus complex (GGC), a group of muscles positioned ventrally within the head. Overall, vocal muscles had significantly lower [Mb] and β than locomotor muscles from the same species. The PPS was predominately composed of small diameter slow-twitch fibers. Fiber-type and myosin heavy chain analyses revealed that the GGC was comprised largely of fast-twitch fibers (Tursiops: 88.6%, Phocoena: 79.7%) and had the highest β of all vocal muscles. Notably, there was a significant difference in [Mb] between the RNM and LNM in Tursiops, but not Phocoena. Our results reveal shared physiological characteristics of individual vocal muscles across species that enhance our understanding of key functional roles, as well as species-specific differences which appear to reflect differences in vocal capacities.

Estradiol modulates myosin regulatory light chain phosphorylation and contractility in skeletal muscle of female mice

Impairment of skeletal muscle function has been associated with changes in ovarian hormones, especially estradiol. To elucidate mechanisms of estradiol on skeletal muscle strength, the hormone's effects on phosphorylation of the myosin regulatory light chain (pRLC) and muscle contractility were investigated, hypothesizing an estradiol-specific beneficial impact. In a skeletal muscle cell line, C2C12, pRLC was increased by 17β-estradiol (E2) in a concentration-dependent manner. In skeletal muscles of C57BL/6 mice that were E2 deficient via ovariectomy (OVX), pRLC was lower than that from ovary-intact, sham-operated mice (Sham). The reduced pRLC in OVX muscle was reversed by in vivo E2 treatment. Posttetanic potentiation (PTP) of muscle from OVX mice was low compared with that from Sham mice, and this decrement was reversed by acute E2 treatment, demonstrating physiological consequence. Western blot of those muscles revealed that low PTP corresponded with low pRLC and higher PTP with greater pRLC. We aimed to elucidate signaling pathways affecting E2-mediated pRLC using a kinase inhibitor library and C2C12 cells as well as a specific myosin light chain kinase inhibitor in muscles. PI3K/Akt, MAPK, and CamKII were identified as candidate kinases sensitive to E2 in terms of phosphorylating RLC. Applying siRNA strategy in C2C12 cells, pRLC triggered by E2 was found to be mediated by estrogen receptor-β and the G protein-coupled estrogen receptor. Together, these results provide evidence that E2 modulates myosin pRLC in skeletal muscle and is one mechanism by which this hormone can affect muscle contractility in females.

Estradiol stimulates mitochondrial biogenesis and adiponectin expression in skeletal muscle

Sexual dimorphism has been found in mitochondrial features of skeletal muscle, with female rats showing greater mitochondrial mass and function compared with males. Adiponectin is an insulin-sensitizing adipokine whose expression has been related to mitochondrial function and that is also expressed in skeletal muscle, where it exerts local metabolic effects. The aim of this research was to elucidate the role of sex hormones in modulation of mitochondrial function, as well as its relationship with adiponectin production in rat skeletal muscle. An in vivo study with ovariectomized Wistar rats receiving or not receiving 17β-estradiol (E2) (10 μg/kg per 48 h for 4 weeks) was carried out, in parallel with an assay of cultured myotubes (L6E9) treated with E2 (10 nM), progesterone (Pg; 1 μM), or testosterone (1 μM). E2 upregulated the markers of mitochondrial biogenesis and dynamics, and also of mitochondrial function in skeletal muscle and L6E9. Although in vivo E2 supplementation only partially restored the decreased adiponectin expression levels induced by ovariectomy, these were enhanced by E2 and Pg treatment in cultured myotubes, whereas testosterone showed no effects. Adiponectin receptor 1 expression was increased by E2 treatment, both in vivo and in vitro, but testosterone decreased it. In conclusion, our results are in agreement with the sexual dimorphism previously reported in skeletal muscle mitochondrial function and indicate E2 to be its main effector, as it enhances mitochondrial function and diminishes oxidative stress. Moreover, our data support the idea of the existence of a link between mitochondrial function and adiponectin expression in skeletal muscle, which could be modulated by sex hormones.

Comparison of natural estrogens and synthetic derivative on genioglossus function and estrogen receptors expression in rats with chronic intermittent hypoxia

The pathogenesis of obstructive sleep apnea--hypopnea syndrome (OSAHS) is summarized as the narrow anatomic structure of upper airway (UA) and the defective function of UA dilator muscles. Up to now, there have been no specific treatments for the UA dilator muscle deficiency. We previously found that some estrogen-like compounds exert protective effects on genioglossus, but this protection tends to be less satisfactory. A novel phytoestrogen derivative was synthesized in recent years and was verified to have some cytoprotective activity. This study was designed to compare the effects of natural estrogens and the synthetic resveratrol dimer on genioglossus contraction and expression of estrogen receptors (ERs) under chronic intermittent hypoxia (CIH) condition. Genioglossus myoblasts of rat were isolated and cultured in a culture medium with different agents (estradiol, genistein, resveratrol, and resveratrol dimer, respectively) under hypoxia condition, and ERs expressions were detected. In vivo study, 48 ovariectomized female rats were randomized into six groups. After CIH exposure and agents injection, rats were tested for genioglossus contractile properties and further analysis of ERs expression. Estradiol up-regulated ERα level and exerted the best protective effect of fatigue resistance. Genistein, resveratrol and resveratrol dimer primarily up-regulated the expression of ERβ. Resveratrol dimer exhibited better protection of fatigue resistance than genistein and resveratrol, and expressed higher binding affinity for ERβ than for ERα. Besides estrogenic effects, there may be some other mechanisms for the fatigue resistance improvement contributed by phytoestrogens and their derivatives.

Synergistic action of gravity and temperature on the motor system within the lifespan: a "Baby Astronaut" hypothesis

Here we describe GATO (gravity, age, thermoregulation, and oxygenation) hypothesis (or a "Baby Astronaut" hypothesis) which we suggest to explain synergistic effect of these factors on the motor system. Taken separately, microgravity (in spaceflight, G~0), the early age, heat and hypoxia exert identical effect on the motor system. We posit that synergy of these factors originate from their synchronicity during intrauterine immersion (analog microgravity) of the fetus in warm hypoxic condition. We further postulate three successive motor adaptive strategies, driven lifelong by gravity as the key factor. The first by age, fetal/microgravity (FM)-strategy, induced by the intrauterine immersion of the fetus, is based on domination of fast type muscle fibers. After birth, thought to be analog for landing from orbit, newborn is subjected to combined influence of cooler ambient temperature, normoxia, and 1G Earth gravity, which cooperatively form a slower GE-strategy. Eventually, healthy ageing results in further domination of slow type muscle fibers that forms the slowest (SL)-strategy. Our hypothesis implies that specific sensory conditions may substitute for each other owing to their synergistic action on the motor system. According to GATO hypothesis heating and hypoxia may be considered as "pro-microgravity" factors, while cold and hyperoxia - as "pro-gravity" ones. As such, cold may act as a partial "surrogate" for gravity, estimated as ~0.2G. That may have potential to elaborate countermeasures for muscle atrophy in astronauts either on-board in long-term spaceflight or for post-flight rehabilitation. Based on GATO hypothesis, predictions on muscle remodeling caused by illumination, sound/noise, and gravidity are discussed.

Down-regulation of hypoxia inducible factor-1alpha: a possible explanation for the protective effects of estrogen on genioglossus fatigue resistance

Patients with obstructive sleep apnea/hypopnea syndrome (OSAHS) often exhibit fatigued or inefficient upper airway dilator muscle activity. It has been shown that estrogen may have some impact on upper airway contractility under normoxic conditions. Chronic intermittent hypoxia (CIH) is a frequent feature of OSAHS, and it may alter muscle susceptibility to oxidative stress, a characteristic of a fatigable nature. Hypoxia inducible factor-1 (HIF-1) is a transcription factor that is responsible for the regulation of oxygen homeostasis under hypoxic conditions. We examined the effects of estrogen on the contractility of the genioglossus by exposing rats to alternating cycles of 6-8% O(2) every 15 s for a total duration of 35 d. The results showed that muscle fatigue resistance was significantly decreased after CIH but was partially reversed after estrogen treatment. Compared with the control group, real-time reverse transcription-polymerase chain reaction and western blotting showed higher levels of HIF-1alpha messenger RNA and protein in the CIH group, but estrogen treatment reduced, in a dose-independent manner, the levels of HIF-1alpha messenger RNA and protein in rats exposed to CIH. We conclude that CIH induced the expression of HIF-1alpha in the genioglossus and altered the physical properties towards a more fatigable phenotype, whereas estrogen inhibited the over-expression of HIF-1alpha, and this may account for the improvement of upper airway muscle endurance in CIH rats.

Effects of oestrogen on sarcoplasmic reticulum Ca2+-ATPase activity and gene expression in genioglossus in chronic intermittent hypoxia rat

This study was designed to investigate the effects of oestrogen on sarcoplasmic reticulum (SR) Ca(2+)-ATPase activity and gene expression in ovariectomised rats under the condition of chronic intermittent hypoxia (CIH). Thirty-two female Sprague-Dawley rats were randomly divided into four groups: the normal control group (NC), the CIH group (CIH), the CIH-ovariectomised group (CIH+OVX), and the group of CIH-ovariectomised rats receiving estradiol replacement (CIH+OVX+E(2)). Rats in the latter three groups were exposed to CIH for 5 weeks. The animals were killed before genioglossus (GG) was rapidly excised, and their body and uterus mass were determined. Estradiol level was detected by radioimmunoassay. SR Ca(2+)-ATPase (SERCA) activity was observed by detecting inorganic phosphorus ion, and the SERCA mRNA level was measured using real-time quantitative polymerase chain reaction (real-time PCR). It was found that, compared with the NC group, the SERCA activity and mRNA level were remarkably reduced (p<.01) in the CIH group. And compared with the CIH group, the SERCA activity and mRNA level were also significantly reduced (p<.01) in the CIH+OVX group. Meanwhile, the SERCA activity and mRNA level significantly increased (p<.01) in the CIH+OVX+E(2) group compared with the CIH+OVX group, but lower than those in the NC group (p<.01). The results showed that CIH could reduce the SERCA activity and mRNA expression, and oestrogen-deficiency could exacerbate this effect; whilst estradiol replacement can partially reverse the effect of CIH in ovariectomised rats.