Stress-induced mucin 13 reductions drive intestinal microbiome shifts and despair behaviors

Depression is a prevalent psychological condition with limited treatment options. While its etiology is multifactorial, both chronic stress and changes in microbiome composition are associated with disease pathology. Stress is known to induce microbiome dysbiosis, defined here as a change in microbial composition associated with a pathological condition. This state of dysbiosis is known to feedback on depressive symptoms. While studies have demonstrated that targeted restoration of the microbiome can alleviate depressive-like symptoms in mice, translating these findings to human patients has proven challenging due to the complexity of the human microbiome. As such, there is an urgent need to identify factors upstream of microbial dysbiosis. Here we investigate the role of mucin 13 as an upstream mediator of microbiome composition changes in the context of stress. Using a model of chronic stress, we show that the glycocalyx protein, mucin 13, is selectively reduced after psychological stress exposure. We further demonstrate that the reduction of Muc13 is mediated by the Hnf4 transcription factor family. Finally, we determine that deleting Muc13 is sufficient to drive microbiome shifts and despair behaviors. These findings shed light on the mechanisms behind stress-induced microbial changes and reveal a novel regulator of mucin 13 expression.

TGFB1 induces fetal reprogramming and enhances intestinal regeneration

The gut epithelium has a remarkable ability to recover from damage. We employed a combination of high-throughput sequencing approaches, mouse genetics, and murine and human organoids and identified a role for TGFB signaling during intestinal regeneration following injury. At 2 days following irradiation (IR)-induced damage of intestinal crypts, a surge in TGFB1 expression is mediated by monocyte/macrophage cells at the location of damage. The depletion of macrophages or genetic disruption of TGFB signaling significantly impaired the regenerative response. Intestinal regeneration is characterized by the induction of a fetal-like transcriptional signature during repair. In organoid culture, TGFB1 treatment was necessary and sufficient to induce the fetal-like/regenerative state. Mesenchymal cells were also responsive to TGFB1 and enhanced the regenerative response. Mechanistically, pro-regenerative factors, YAP/TEAD and SOX9, are activated in the epithelium exposed to TGFB1. Finally, pre-treatment with TGFB1 enhanced the ability of primary epithelial cultures to engraft into damaged murine colon, suggesting promise for cellular therapy.

Zoledronic acid improves bone quality and muscle function in a high bone turnover state

SUMMARY

Zoledronic acid (ZA) prevents muscle weakness in mice with bone metastases; however, its role in muscle weakness in non-tumor-associated metabolic bone diseases and as an effective treatment modality for the prevention of muscle weakness associated with bone disorders, is unknown. We demonstrate the role of ZA-treatment on bone and muscle using a mouse model of accelerated bone remodeling, which represents the clinical manifestation of non-tumor associated metabolic bone disease. ZA increased bone mass and strength and rescued osteocyte lacunocanalicular organization. Short-term ZA treatment increased muscle mass, whereas prolonged, preventive treatment improved muscle mass and function. In these mice, muscle fiber-type shifted from oxidative to glycolytic and ZA restored normal muscle fiber distribution. By blocking TGFβ release from bone, ZA improved muscle function, promoted myoblast differentiation and stabilized Ryanodine Receptor-1 calcium channel. These data demonstrate the beneficial effects of ZA in maintaining bone health and preserving muscle mass and function in a model of metabolic bone disease.

Context and significance

TGFβ is a bone regulatory molecule which is stored in bone matrix, released during bone remodeling, and must be maintained at an optimal level for the good health of the bone. Excess TGFβ causes several bone disorders and skeletal muscle weakness. Reducing excess TGFβ release from bone using zoledronic acid in mice not only improved bone volume and strength but also increased muscle mass, and muscle function. Progressive muscle weakness coexists with bone disorders, decreasing quality of life and increasing morbidity and mortality. Currently, there is a critical need for treatments improving muscle mass and function in patients with debilitating weakness. Zoledronic acid's benefit extends beyond bone and could also be useful in treating muscle weakness associated with bone disorders.

[The laryngeal mask--a valuable instrument for cases of difficult intubation in children. Anesthesiologic management in the presence of Pierre-Robin syndrome]

In cases of craniofacial and mandibulofacial malformations, which are mostly treated during childhood, difficult intubation conditions must generally be expected. In such cases, the laryngeal mask airway (LMA) an alternative instrument for use in endotracheal intubation is a new aid for ventilation. In certain instances, it can be used alone to induce general anaesthesia. Reports of endotracheal intubation by means of the LMA in adults have also been published.

CASE REPORT

In our case, a 6-year-old boy with Pierre-Robin syndrome (triad: micrognathia, broad palatoschisis, glossoptosis) needed dental resetting. After induction of anaesthesia in this very cooperative boy with thiopentone and fluothane and relaxation with succinylcholine, it was not possible to examine the hypopharynx by laryngoscopy preparatory to nasal intubation as usual. Repeated blind attempts at nasal intubation (again with spontaneous breathing) failed, as did the attempt at fibreoptic bronchoscopic intubation, because of the narrow anatomical conditions. Finally, a laryngeal mask airway (LMA; size 2) was introduced, and as a result of this ventilation was achieved. However, endotracheal intubation was required for performance of the surgical resetting. With the fibreoptic bronchoscope, we could verify the central position of the LMA over the glottis. A tracheal tube (size 4) was inserted across the laryngeal airway without optic control. The tube connector was disconnected and a normal guide inserted into the tube to remove the LMA. The dental resetting was also performed by oral intubation.

CONCLUSION

Therefore, the LMA is not only a ventilation aid, but also a valuable tool in difficult intubation conditions. In our opinion, it is necessary to provide this tool in every anaesthetic unit.