The critical role of gut microbiota dysbiosis in skeletal muscle wasting: a systematic review.

AIMS: Skeletal muscle wasting is affected by the gut microbiota dysbiosis through multiple pathways, including inflammatory process, defected immune system, and anabolic resistance. We aimed to systematically review the studies investigating the gut microbiota composition in sarcopenic and cachexic humans and animals. METHODS: We carried out a comprehensively systematic search using relevant keywords on PubMed, Web of Science, and Scopus databases until July 2021. Original human observational research and animal studies related to our research topics published in English were selected. RESULTS: Seven human studies and five animal studies were included. Three human studies were case-control, whereas the other four were cross-sectional studies that investigated three different conditions, including age-related sarcopenia, as well as liver cirrhosis and cancer cachexia. The principal alteration in age-related sarcopenia and liver cirrhosis-induced sarcopenia was a reduction in short-chain fatty acids (SCFAs) -producing bacteria. Lachnospiraceae family, consisting of Lachnospira, Fusicatenibacter, Roseburia, and Lachnoclostridium, significantly decreased in age-related sarcopenia, while in liver cirrhosis-induced sarcopenia, the alpha diversity of gut microbiota decreased compared with the control group. Moreover, Enterobacteriaceae, which has a pro-inflammatory effect increased in muscle-wasted animals. CONCLUSION: This systematic review presents associations between the gut microbiota alterations and skeletal muscle wasting as a consequence of various pathologies, including aging sarcopenia, renal failure, and cancer cachexia in both human and animal studies.

Brown adipose tissue and alzheimer's disease.

Alzheimer's disease (AD), the most common type of senile dementia, is a chronic neurodegenerative disease characterized by cognitive dysfunction and behavioral disability. The two histopathological hallmarks in this disease are the extraneuronal accumulation of amyloid-ß (Aß) and the intraneuronal deposition of neurofibrillary tangles (NFTs). Despite this, central and peripheral metabolic dysfunction, such as abnormal brain signaling, insulin resistance, inflammation, and impaired glucose utilization, have been indicated to be correlated with AD. There is solid evidence that the age-associated thermoregulatory deficit induces diverse metabolic changes associated with AD development. Brown adipose tissue (BAT) has been known as a thermoregulatory organ particularly vital during infancy. However, in recent years, BAT has been accepted as an endocrine organ, being involved in various functions that prevent AD, such as regulating energy metabolism, secreting hormones, improving insulin sensitivity, and increasing glucose utilization in adult humans. This review focuses on the mechanisms of BAT activation and the effect of aging on BAT production and signaling. Specifically, the evidence demonstrating the effect of BAT on pathological mechanisms influencing the development of AD, including insulin pathway, thermoregulation, and other hormonal pathways, are reviewed in this article.

DNA Damage Responses, the Trump Card of Stem Cells in the Survival Game.

Stem cells, as a group of undifferentiated cells, are enriched with self-renewal and high proliferative capacity, which have attracted the attention of many researchers as a promising approach in the treatment of many diseases over the past years. However, from the cellular and molecular point of view, the DNA repair system is one of the biggest challenges in achieving therapeutic goals through stem cell technology. DNA repair mechanisms are an advantage for stem cells that are constantly multiplying to deal with various types of DNA damage. However, this mechanism can be considered a trump card in the game of cell survival and treatment resistance in cancer stem cells, which can hinder the curability of various types of cancer. Therefore, getting a deep insight into the DNA repair system can bring researchers one step closer to achieving major therapeutic goals. The remarkable thing about the DNA repair system is that this system is not only under the control of genetic factors, but also under the control of epigenetic factors. Therefore, it is necessary to investigate the role of the DNA repair system in maintaining the survival of cancer stem cells from both aspects.

Application of Biocompatible Scaffolds in Stem-Cell-Based Dental Tissue Engineering.

Tissue engineering as an important field in regenerative medicine is a promising therapeutic approach to replace or regenerate injured tissues. It consists of three vital steps including the selection of suitable cells, formation of 3d scaffolds, and adding growth factors. Mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs) are mentioned as two main sources for this approach that have been used for the treatment of various types of disorders. However, the main focus of literature in the field of dental tissue engineering is on utilizing MSCs. On the other hand, biocompatible scaffolds play a notable role in this regenerative process which is mentioned to be harmless with acceptable osteoinductivity. Their ability in inhibiting inflammatory responses also makes them powerful tools. Indeed, stem cell functions should be supported by biomaterials acting as scaffolds incorporated with biological signals. Naturally derived polymeric scaffolds and synthetically engineered polymeric/ceramic scaffolds are two main types of scaffolds regarding their materials that are defined further in this review. Various strategies of tissue bioengineering can affect the regeneration of dentin-pulp complex, periodontium regeneration, and whole teeth bioengineering. In this regard, in vivo/ex vivo experimental models have been developed recently in order to perform preclinical studies of dental tissue engineering which make it more transferable to be used for clinic uses. This review summarizes dental tissue engineering through its different components. Also, strategies of tissue bioengineering and experimental models are introduced in order to provide a perspective of the potential roles of dental tissue engineering to be used for clinical aims.

Low physical activity is the strongest factor associated with frailty phenotype and frailty index: data from baseline phase of Birjand Longitudinal Aging Study (BLAS).

BACKGROUND: Frailty is the most complicated expression of aging that is related to disability or multi-morbidity. The aim of the present study was to estimate the prevalence of frailty and its associated factors among community-dwelling aged population. METHODS: A total of 1529 eligible community- dwelling older adults (≥ 60 years) were enrolled in the baseline phase of Birjand Longitudinal Aging Study (BLAS) from 2019 to 2020. Their frailty status was assessed using the Fried's frailty phenotype and frailty index. Sociodemographic factors, including sex, age, marital status, and education level, were collected. Health status assessment included the history of hypertension, diabetes mellitus, cardiovascular disease, Alzheimer's diseases and dementia, and other health conditions. Furthermore, functional assessment (ADL, IADL) and anthropometric measurements including height, weight, waist, calf, and mid-arm circumference were made and the body mass index was calculated. The nutrition status and polypharmacy (use 3 or more medication) were also evaluated. RESULTS: The prevalence of frailty was 21.69% according to the frailty phenotype and 23.97% according to the frailty index. A multiple logistic regression model showed a strong association between low physical activity and frailty phenotype (OR = 36.31, CI = 16.99-77.56, P < 0.01), and frailty index (OR = 15.46, CI = 5.65-42.34, P < 0.01). Other factors like old age (≥80), female sex, malnutrition, polypharmacy, obesity, and arthritis were also associated with frailty. The Kappa coefficient of the agreement between these two instruments was 0.18. CONCLUSION: It seems that low physical activity is the most important determinant of frailty. Low physical activity and some other factors may be preventable or modifiable and thus serve as clinically relevant targets for intervention.

Gut microbiota: a perspective of precision medicine in endocrine disorders.

Gut microbiota composition is unique in every individual, it impacts on organ functions that produce hormones. Gut microbiota composition balance is directly related to our general health status. This continual interaction between gut microbiota and endocrine organs sometimes can be considered as the etiology of diseases such as type 2 diabetes mellitus (T2DM), obesity, osteoporosis, polycystic ovary syndrome (PCOS), and thyroid diseases. Microbiota is introduced for a total collection of microbial organisms in our bodies and microbiome referred for their genome and their collective functions. Near 100 trillion microorganisms live in our body and almost all of them occupy the human gut gastrointestinal tract. Precision medicine can play a crucial role in health maintenance by affecting gut microbiota composition in every individual. It can also develop special treatments specifically for every individual. In this review, we addressed any correlation between gut microbiota and endocrine disorders including T2DM, obesity, PCOS, thyroid disorders and osteoporosis.