Gut microbiome and retinal diseases: an updated review.

PURPOSE OF REVIEW: The gut microbiome, trillions of microorganisms residing in our digestive tract, is now believed to play a significant role in retinal diseases. Breakthroughs in computational biology and specialized animal models have allowed researchers not only to characterize microbes associated with retinal diseases, but also to provide early insights into the function of the microbiome in relation to biological processes in the retinal microenvironment. This review aims to provide an update on recent advances in the current knowledge on the relationship between the gut microbiome and retinal disorders. RECENT FINDINGS: Recent work demonstrates distinct gut microbial compositions associated with retinal diseases such as agerelated macular degeneration and retinopathy of prematurity. Currently, it is believed that gut dysbiosis leads to increased gut permeability, elevated circulation of bacterial products, microbial metabolites and inflammatory mediators that result in immune dysregulation at distant anatomic sites including the retina. SUMMARY: Emerging evidence for the gut-retina axis can elucidate previously unknown pathways involved in retinal diseases and also presents an exciting potential therapeutic avenue. Further preclinical and clinical studies are necessary to establish causation and delineate the precise relationship of the gut microbiome with retinal disorders.

Predictors of Opioid Prescription After Orthognathic Surgery in Opioid Naive Adults From a Large Database.

BACKGROUND: Orthognathic surgery often requires postoperative opioid pain management. The goal of this study was to examine opioid prescribing patterns in adults after orthognathic surgery and to analyze factors associated with high-dose postoperative opioid administration and persistent opioid use. METHODS: We included opioid naive adults in the IBM MarketScan Databases who had undergone orthognathic surgery from 2003 to 2017. Three outcomes were examined: presence of a perioperative outpatient opioid claim; total oral morphine milliequivalents (MMEs) in the perioperative period; and persistent opioid use. Univariate analysis and multiple regression were used to determine associations between the outcomes and independent variables. RESULTS: Our study yielded a cohort of 8163 opioid naive adults, 45.6% of whom had an opioid claim in the perioperative period. The average prescribed MMEs in the perioperative period was 466 MMEs total, and 66 MMEs daily. Of patients with an opioid claim, 17.9% had persistent opioid use past 90 days. The presence of a complication was a predictor of having an opioid claim (P<0.001). Increasing age (P<0.001) and days hospitalized (P < 0.001) were associated with increased opioid usage. Persistent opioid use was associated with being prescribed more than 600 MMEs in the perioperative period (P < 0.001), as well as increasing age and days hospitalized. Interestingly, patients undergoing double-jaw surgery did not have significantly more opioids prescribed than those undergoing single-jaw surgery. CONCLUSIONS: Prescription opioids are relatively uncommon after jaw surgery, although 17.9% of patients continue to use opioids beyond 3 months after surgery. Predictors of persistent opioid use in this population include the number of days hospitalized, increasing age, and increasing amount of opioid prescribed postoperatively.

Oral Metformin Inhibits Choroidal Neovascularization by Modulating the Gut-Retina Axis.

Purpose: Emerging data indicate that metformin may prevent the development of age-related macular degeneration (AMD). Whereas the underlying mechanisms of metformin's anti-aging properties remain undetermined, one proposed avenue is the gut microbiome. Using the laser-induced choroidal neovascularization (CNV) model, we investigate the effects of oral metformin on CNV, retinal pigment epithelium (RPE)/choroid transcriptome, and gut microbiota. Methods: Specific pathogen free (SPF) male mice were treated via daily oral gavage of metformin 300 mg/kg or vehicle. Male mice were selected to minimize sex-specific differences to laser induction and response to metformin. Laser-induced CNV size and macrophage/microglial infiltration were assessed by isolectin and Iba1 immunostaining. High-throughput RNA-seq of the RPE/choroid was performed using Illumina. Fecal pellets were analyzed for gut microbiota composition/pathways with 16S rRNA sequencing/shotgun metagenomics, as well as microbial-derived metabolites, including small-chain fatty acids and bile acids. Investigation was repeated in metformin-treated germ-free (GF) mice and antibiotic-treated/GF mice receiving fecal microbiota transplantation (FMT) from metformin-treated SPF mice. Results: Metformin treatment reduced CNV size (P < 0.01) and decreased Iba1+ macrophage/microglial infiltration (P < 0.005). One hundred forty-five differentially expressed genes were identified in the metformin-treated group (P < 0.05) with a downregulation in pro-angiogenic genes Tie1, Pgf, and Gata2. Furthermore, metformin altered the gut microbiome in favor of Bifidobacterium and Akkermansia, with a significant increase in fecal levels of butyrate, succinate, and cholic acid. Metformin did not suppress CNV in GF mice but colonization of microbiome-depleted mice with metformin-derived FMT suppressed CNV. Conclusions: These data suggest that oral metformin suppresses CNV, the hallmark lesion of advanced neovascular AMD, via gut microbiome modulation.

Notch signaling: Its essential roles in bone and craniofacial development.

Notch is a cell-cell signaling pathway that is involved in a host of activities including development, oncogenesis, skeletal homeostasis, and much more. More specifically, recent research has demonstrated the importance of Notch signaling in osteogenic differentiation, bone healing, and in the development of the skeleton. The craniofacial skeleton is complex and understanding its development has remained an important focus in biology. In this review we briefly summarize what recent research has revealed about Notch signaling and the current understanding of how the skeleton, skull, and face develop. We then discuss the crucial role that Notch plays in both craniofacial development and the skeletal system, and what importance it may play in the future.