Diet1 is a regulator of fibroblast growth factor 15/19-dependent bile acid synthesis

The Role of FGF19 and MALRD1 in Enterohepatic Bile Acid Signaling

Bile acids are the catabolic end products of cholesterol metabolism that are best known for their role in the digestion of lipids. In the last two decades, extensive investigation has shown bile acids to be important signaling molecules in metabolic processes throughout the body. Bile acids are ligands that can bind to several receptors, including the nuclear receptor farnesoid X receptor (FXR) in ileal enterocytes. FXR activation induces the expression of fibroblast growth factor (FGF) 15/19, a hormone that can modulate bile acid levels, repress gluconeogenesis and lipogenesis, and promote glycogen synthesis. Recent studies have described a novel intestinal protein, MAM and LDL Receptor Class A Domain containing 1 (MALRD1) that positively affects FGF15/19 levels. This signaling pathway presents an exciting target for treating metabolic disease and bile acid-related disorders.

A Peptide Probe Enables Photoacoustic-Guided Imaging and Drug Delivery to Lung Tumors in K-rasLA2 Mutant Mice

The lack of molecular targets and targeting probes remains a major drawback for targeted imaging and drug delivery in lung cancer. In this study, we exploited in vivo phage display to identify a novel targeting probe that homes to the tumor in a K-ras^LA2 mutant mouse lung cancer model. Compared with other candidate peptides selected from 5 rounds of phage display, the CRQTKN peptide homed to tumor nodules in the lung of mutant mice at higher levels. Photoacoustic tomography of mutant mice detected lung tumors via tumor homing of the near-infrared fluorescence dye-labeled CRQTKN peptide. Ex vivo photoacoustic images of isolated organs further demonstrated tumor homing of the CRQTKN peptide, whereas minimal accumulation was observed in control organs, such as the liver. Compared with untargeted liposomes and doxorubicin, doxorubicin-loaded liposomes whose surface was modified with the CRQTKN peptide more efficiently delivered doxorubicin and reduced the number or size of tumor lesions in K-ras^LA2 mutant mice. Analysis of hematologic parameters and liver and kidney function showed no significant systemic side effects by the treatments. Affinity-based identification was used to detect TNF receptor superfamily member 19L (TNFRSF19L), which was upregulated in lung tumors of mutant mice, as the receptor for the CRQTKN peptide. In conclusion, these results suggest that the CRQTKN peptide is a promising targeting probe for photoacoustic-guided detection and drug delivery to lung cancer, and acts by binding to TNFRSF19L. SIGNIFICANCE: These findings present a new tumor-targeting probe for photoacoustic-guided detection and drug delivery.

Challenges in the clinical interpretation of small de novo copy number variants in neurodevelopmental disorders

In clinical genetics, the need to discriminate between benign and pathogenic variants identified in patients with neurodevelopmental disorders is an absolute necessity. Copy number variants (CNVs) of small size can enable the identification of genes that are critical for neurologic development. However, assigning a definite association with a specific disorder is a difficult task. Among 328 trios analyzed over seven years of activity in a single laboratory, we identified 19 unrelated patients (5.8%) who carried a small (<500 kb) de novo CNV. Four patients had an additional independent de novo CNV. Nine had a variant that could be assigned as definitely pathogenic, whereas the remaining CNVs were considered as variants of unknown significance (VUS). We report clinical and molecular findings of patients harboring VUS. We reviewed the medical literature available for genes impacted by CNVs, obtained the probability of truncating loss-of-function intolerance, and compared overlapping CNVs reported in databases. The classification of small non-recurrent CNVs remains difficult but, among our findings, we provide support for a role of SND1 in the susceptibility of autism, describe a new case of the rare 17p13.1 microduplication syndrome, and report an X-linked duplication involving KIF4A and DLG3 as a likely cause of epilepsy.

Regulation of Fgf15 expression in the intestine by glucocorticoid receptor

Fibroblast growth factor 15 (FGF15) was previously identified to be highly expressed in the ileum and functions as an endocrine factor to regulate bile acid synthesis in the liver. FGF15 targets its receptor fibroblast growth factor receptor 4 in the liver and serves important roles in energy metabolism, including bile acid homeostasis, glucose metabolism and protein synthesis. The expression of FGF15 is known to be regulated by the transcription factor farnesoid X receptor (FXR). In the present study, reverse transcription-quantitative polymerase chain reaction was used for measuring Fgf15 expression from the animal and tissue culture experiments, and it was identified that dexamethasone, a drug widely used in anti-inflammation therapy, and a classical inducer of glucocorticoid receptor (GR)- and pregnane X receptor (PXR)-target genes, may downregulate Fgf15 expression in the ileum. GR was identified to be highly expressed in the ileum by western blot analysis. Furthermore, it was demonstrated that the downregulation of Fgf15 by dexamethasone is due to the repression of ileal FXR activity via GR; however, not PXR, in the ileum. The present results provide insight for a better understanding of the adverse effects associated with dexamethasone therapy.

Trimethylamine-N-oxide: a link between the gut microbiome, bile acid metabolism, and atherosclerosis

PURPOSE OF REVIEW

This article evaluates the link between trimethylamine-N-oxide (TMAO) and bile acids and the consequent impact on the development of atherosclerosis.

RECENT FINDINGS

Elevation in plasma TMAO concentrations is associated with an increased risk of cardiovascular disease in many different patient cohorts. In addition to the recently identified direct effects of TMAO on the development of atherosclerosis, other components involved in TMAO metabolism may also have an impact. Furthermore, the relationship between TMAO and bile acid regulation is emerging as a possible mediator of atherosclerosis.

SUMMARY

Studies that are emerging highlight the mechanistic relationship of TMAO to the development atherosclerosis in addition to its role as disease biomarker. The interplay between TMAO and bile acid metabolism mediated through multiple factors, such as the gut microbiome, farnesoid X receptor signaling, and flavin monooxygenase 3 activity may help identify another pathway by which atherosclerosis occurs. In this review, we discuss the most recent data regarding atherosclerosis, TMAO, and bile acid metabolism.