Significance of vagus nerve function in terms of pathogenesis of psychosocial disorders

Unmasking the hidden risks: clinical implications of 4 premolar extraction orthodontics on health and upper airway dynamics

A COMMENTARY ON

Zhang J, Chen G, Li W, Xu T, Gao X Upper airway changes after orthodontic extraction treatment in adults: a preliminary study using cone beam computed tomography. PLoS ONE 2015; https://doi.org/10.1371/journal.pone.0143233 .

DESIGN

Retrospective study and untreated matched controls.

DATA SOURCE

PubMed, journals.plos.org, researchgate.net, Google Scholar.

STUDY SELECTION

This retrospective study enrolled 18 adults with Class II and hyperdivergent skeletal malocclusion (5 males and 13 females, 24.1 ± 3.8 years of age, BMI 20.33 ± 1.77 kg/m2). And 18 untreated controls were matched 1:1 with the treated patients for age, sex, BMI, and skeletal pattern.

INCLUSION CRITERIA

Age >18 years; sagittal Class II (ANB > 4.7°) and vertical hyperdivergent (MP/SN > 37.7°) skeletal pattern; convex profile evaluated by E line; no missing teeth except for the third molars; orthodontic camouflage treatment with extraction of four premolars and maximum anchorage using mini-screws; and available CBCT data both before and after treatment.

EXCLUSION CRITERIA

Body mass index (BMI) > 25 kg/m2. Rapid maxillary expansion, protraction facemask therapy, extra-oral force to push molars distally, functional appliances, and orthognathic surgery. History of cleft lip or palate. Hyperplasia of tonsils or adenoids or history of tonsillectomy/adenoidectomy. Snoring or other sleep disorders.

RESULTS

Four premolar extraction, upper incisors retracted 7.87 mm, lower incisors retracted 6.10 mm. The cross-sectional area of the upper airway was not changed, but the sagittal dimension between the soft palate and the posterior pharyngeal wall were significantly decreased.

STUDY CONCLUSIONS

The study reported that its null hypothesis was not rejected, with no significant difference in the airway size and significant compression of the sagittal posterior airway.

Psychosocial profiles and their correlation with physical diagnosis in temporomandibular disorders, a preliminary report

OBJECTIVE

To assess representative psychosocial features in a group of temporomandibular disorder (TMD) patients from Jordan using Axis II of the Diagnostic Criteria for TMD (DC/TMD) protocol.

METHODS

Ninety-eight TMD patients were examined according to Axis I DC/TMD protocol in addition to assessment of their pain-related disability, psychological distress, and stress reactivity.

RESULTS

Just under half of the patients (49%) had high intensity of characteristic pain (self-reported TMJ-related pain) and one-third (32%) had high levels of pain-related disability. Furthermore, significant proportions of patients expressed moderate-severe degrees of distress and stress reactivity (41% and 39%, respectively). Significant correlations were identified between the Graded Chronic Pain Scale (GCPS) and each of the pain-related TMD subgroups.

CONCLUSION

TMD patients are susceptible to high levels of pain-related psychosocial impairment, and clinicians should be aware of the possible correlations between the physical TMD diagnosis and specific psychosocial features during treatment planning.

The Brain-Gut-Bone Axis in Neurodegenerative Diseases: Insights, Challenges, and Future Prospects

Neurodegenerative diseases are global health challenges characterized by the progressive degeneration of nerve cells, leading to cognitive and motor impairments. The brain-gut-bone axis, a complex network that modulates multiple physiological systems, has gained increasing attention owing to its profound effects on the occurrence and development of neurodegenerative diseases. No comprehensive review has been conducted to clarify the triangular relationship involving the brain-gut-bone axis and its potential for innovative therapies for neurodegenerative disorders. In light of this, a new perspective is aimed to propose on the interplay between the brain, gut, and bone systems, highlighting the potential of their dynamic communication in neurodegenerative diseases, as they modulate multiple physiological systems, including the nervous, immune, endocrine, and metabolic systems. Therapeutic strategies for maintaining the balance of the axis, including brain health regulation, intestinal microbiota regulation, and improving skeletal health, are also explored. The intricate physiological interactions within the brain-gut-bone axis pose a challenge in the development of effective treatments that can comprehensively target this system. Furthermore, the safety of these treatments requires further evaluation. This review offers a novel insights and strategies for the prevention and treatment of neurodegenerative diseases, which have important implications for clinical practice and patient well-being.

Microglia in Microbiota-Gut-Brain Axis: A Hub in Epilepsy

There is growing concern about the role of the microbiota-gut-brain axis in neurological illnesses, and it makes sense to consider microglia as a critical component of this axis in the context of epilepsy. Microglia, which reside in the central nervous system, are dynamic guardians that monitor brain homeostasis. Microglia receive information from the gut microbiota and function as hubs that may be involved in triggering epileptic seizures. Vagus nerve bridges the communication in the axis. Essential axis signaling molecules, such as gamma-aminobutyric acid, 5-hydroxytryptamin, and short-chain fatty acids, are currently under investigation for their participation in drug-resistant epilepsy (DRE). In this review, we explain how vagus nerve connects the gut microbiota to microglia in the brain and discuss the emerging concepts derived from this interaction. Understanding microbiota-gut-brain axis in epilepsy brings hope for DRE therapies. Future treatments can focus on the modulatory effect of the axis and target microglia in solving DRE.

Rufinamide (RUF) suppresses inflammation and maintains the integrity of the blood-brain barrier during kainic acid-induced brain damage

Rufinamide (RUF) is a structurally unique anti-epileptic drug, but its protective mechanism against brain injury remains unclear. In the present study, we validated how the RUF protected mice with kainic acid (KA)-induced neuronal damage. To achieve that, a mouse epilepsy model was established by KA intraperitoneal injection. After Nissl staining, although there was a significant reduction in Nissl bodies in mice treated with KA, 40, 80, and 120 mg/kg, RUF significantly reduced KA-induced neuronal damage, in a dose-dependent manner. Among them, 120 mg/kg RUF was most pronounced. Immunohistochemistry (IHC) and western blot analysis showed that RUF inhibited the IBA-1 overexpression caused by KA to block microglia cell overactivation. Further, RUF treatment partially reversed neuroinflammatory cytokine (IL-1β, TNFα, HMGB1, and NLRP3) overexpression in mRNA and protein levels in KA mice. Moreover, although KA stimulation inhibited the expression of tight junctions, RUF treatment significantly upregulated expression of tight junction proteins (occludin and claudin 5) in both mRNA and protein levels in the brain tissues of KA mice. RUF inhibited the overactivation of microglia, suppressed the neuroinflammatory response, and reduced the destruction of blood-brain barrier, thereby alleviating the excitatory nerve damage of the KA-mice.

Snapshot of microglial physiological functions

Microglia as a defensive arm of the nervous system emerged early in evolution. The surveilling microglia with motile and ramified processes are the main phenotype in the healthy CNS; the surveilling microglial patrol neuronal somata, dendrites, dendritic spines and axons. Increasing evidence suggests that microglia play fundamental roles in development, maturation and ageing of the brain, as well as contribute to a variety of physiological brain processes including sleep and circadian rhythm. Physiological state of microglia is tightly regulated by brain microenvironment and controlled by a sophisticated system of receptors and signalling cascades including ionotropic and metabotropic purinoceptors, pattern-recognition receptors, and receptors for chemokines and cytokines. Microglia also utilise ion channels and transporters in regulating ionic homeostasis and various aspects of microglial function. The major ion transporters expressed by microglia include Na⁺/H⁺ exchanger 1 and Na⁺/Ca²⁺ exchangers, which are involved in regulation of pH_i and Ca²⁺ homeostasis during microglial physiological responses. Microglial cells control development, maturation and plasticity of neuronal ensembles through controlled physiological phagocytosis of synapses or synaptic fragments - processes known as synaptic pruning and trogocytosis. This special issue on "Physiological roles of microglia" is an assembly of papers written by the leading experts in this research field. We start this special issue with this snapshot of microglial physiological functions as a prelude to the indepth discussion of microglia in physiological processes in the nervous system.