The oxytocin receptor (OXTR), encoded by the OXTR gene, is responsible for the signal transduction after binding its ligand, oxytocin. Although this signaling is primarily involved in controlling maternal behavior, it was demonstrated that OXTR also plays a role in the development of the nervous system. Therefore, it is not a surprise that both the ligand and the receptor are involved in the modulation of behaviors, especially those related to sexual, social, and stress-induced activities. As in the case of every regulatory system, any disturbances in the structures or functions of oxytocin and OXTR may lead to the development or modulation of various diseases related to the regulated functions, which in this case include either mental problems (autism, depression, schizophrenia, obsessive-compulsive disorders) or those related to the functioning of reproductive organs (endometriosis, uterine adenomyosis, premature birth). Nevertheless, OXTR abnormalities are also connected to other diseases, including cancer, cardiac disorders, osteoporosis, and obesity. Recent reports indicated that the changes in the levels of OXTR and the formation of its aggregates may influence the course of some inherited metabolic diseases, such as mucopolysaccharidoses. In this review, the involvement of OXTR dysfunctions and OXTR polymorphisms in the development of different diseases is summarized and discussed. The analysis of published results led us to suggest that changes in OXTR expression and OXTR abundance and activity are not specific to individual diseases, but rather they influence processes (mostly related to behavioral changes) that might modulate the course of various disorders. Moreover, a possible explanation of the discrepancies in the published results of effects of the OXTR gene polymorphisms and methylation on different diseases is proposed.

Over the past decades, there has been a significant increase in the burden of neurological diseases, including neurodegenerative disorders, on a global scale. This is linked to a widespread demographic trend in which developed societies are aging, leading to an increased proportion of elderly individuals and, concurrently, an increase in the number of those afflicted, posing one of the main public health challenges for the coming decades. The complex pathomechanisms of neurodegenerative diseases and resulting varied symptoms, which differ depending on the disease, environment, and lifestyle of the patients, make searching for therapies for this group of disorders a formidable challenge. Currently, most neurodegenerative diseases are considered incurable. An important aspect in the fight against and prevention of neurodegenerative diseases may be broadly understood lifestyle choices, and more specifically, what we will focus on in this review, a diet. One proposal that may help in the fight against the spread of neurodegenerative diseases is a diet rich in flavonoids. Flavonoids are compounds widely found in products considered healthy, such as fruits, vegetables, and herbs. Many studies indicated not only the neuroprotective effects of these compounds but also their ability to reverse changes occurring during the progression of diseases such as Alzheimer’s, Parkinson’s and amyotrophic lateral sclerosis. Here, we present the main groups of flavonoids, discussing their characteristics and mechanisms of action. The most widely described mechanisms point to neuroprotective functions due to strong antioxidant and anti-inflammatory effects, accompanied with their ability to penetrate the blood-brain barrier, as well as the ability to inhibit the formation of protein aggregates. The latter feature, together with promoting removal of the aggregates is especially important in neurodegenerative diseases. We discuss a therapeutic potential of selected flavonoids in the fight against neurodegenerative diseases, based on in vitro studies, and their impact when included in the diet of animals (laboratory research) and humans (population studies). Thus, this review summarizes flavonoids’ actions and impacts on neurodegenerative diseases. Therapeutic use of these compounds in the future is potentially possible but depends on overcoming key challenges such as low bioavailability, determining the therapeutic dose, and defining what a flavonoid-rich diet is and determining its potential negative effects. This review also suggests further research directions to address these challenges.

Mucopolysaccharidoses (MPS) comprise a group of 12 metabolic disorders where defects in specific enzyme activities lead to the accumulation of glycosaminoglycans (GAGs) within lysosomes. This classification expands to 13 when considering MPS IIIE. This type of MPS, associated with pathogenic variants in the ARSG gene, has thus far been described only in the context of animal models. However, pathogenic variants in this gene also occur in humans, but are linked to a different disorder, Usher syndrome (USH) type IV, which is sparking increasing debate. This paper gathers, discusses, and summarizes arguments both for and against classifying dysfunctions of arylsulfatase G (due to pathogenic variants in the ARSG gene) in humans as another subtype of MPS, called MPS IIIE. Specific difficulties in diagnostics and the classification of some inherited metabolic diseases are also highlighted and discussed.

The classification of mucopolysaccharidoses (MPSs) includes the classical types (I; II; III with subtypes A, B, C, and D; IV with subtypes A and B; VI; VII; IX; X), associated with impaired lysosomal degradation of mucopolysaccharides, also known as glycosaminoglycans (GAGs), as a result of deficiency in the specific enzymes responsible for GAG degradation (MPS IIIE has so far been identified only in animal models) and MPS-plus syndrome (MPSPS), which is characterized by an accumulation of undegraded GAGs, arising from impaired endosomal trafficking and inefficient delivery of these compounds to lysosomes (due to the VPS33A protein deficiency with normal GAG-degrading enzyme activities assessed in vitro). The aim of this comprehensive review is to provide physicians with a clinical, biochemical, and molecular overview of MPS manifestation. A brief summary of available and emerging therapies is also presented.

Neurodegeneration with brain iron accumulation (NBIA) is a group of rare neurodegenerative disorders characterized by excessive iron deposition in the central nervous system. The disease typically manifests in early childhood with progressive dystonia, muscle rigidity, spasticity, ataxia, as well as personality changes (such as nervousness, aggression, and learning difficulties) and psychiatric symptoms (including disorientation, confusion, seizures, and dementia). The most common forms – BPAN, PKAN, MPAN, and PLAN—are associated with mutations in the WDR45, PANK2, C19orf12, and PLA2G6 genes, respectively, leading to disruptions in mitochondrial functions, autophagy, and coenzyme A metabolism. These abnormalities result in oxidative stress and neurodegeneration; however, the connection between the observed mutations and iron accumulation in the central nervous system remains unclear. There is ongoing debate as to whether iron accumulation is a primary pathological factor or a secondary consequence of cellular dysfunction. Unfortunately, despite numerous therapeutic attempts, including the use of iron chelators, treatment efficacy remains very limited. Therefore, the aim of this review was to present the latest findings on the relationship between WDR45, PANK2, C19orf12, and PLA2G6 mutations and iron metabolism disorders. The data presented may help explain the previously undescribed roles of these mutations in the excessive iron accumulation observed in the nervous system of patients with NBIA, while also highlighting the complexity of NBIA pathogenesis. A better understanding of these mechanisms may contribute to the development of new, more effective therapeutic strategies, which are greatly needed by patients.