A gut-derived hormone regulates cholesterol metabolism

Interkingdom signaling between gastrointestinal hormones and the gut microbiome

The interplay between the gut microbiota and gastrointestinal hormones plays a pivotal role in the health of the host and the development of diseases. As a vital component of the intestinal microecosystem, the gut microbiota influences the synthesis and release of many gastrointestinal hormones through mechanisms such as modulating the intestinal environment, producing metabolites, impacting mucosal barriers, generating immune and inflammatory responses, and releasing neurotransmitters. Conversely, gastrointestinal hormones exert feedback regulation on the gut microbiota by modulating the intestinal environment, nutrient absorption and utilization, and the bacterial biological behavior and composition. The distributions of the gut microbiota and gastrointestinal hormones are anatomically intertwined, and close interactions between the gut microbiota and gastrointestinal hormones are crucial for maintaining gastrointestinal homeostasis. Interventions leveraging the interplay between the gut microbiota and gastrointestinal hormones have been employed in the clinical management of metabolic diseases and inflammatory bowel diseases, such as bariatric surgery and fecal microbiota transplantation, offering promising targets for the treatment of dysbiosis-related diseases.

Integrating Mendelian randomization and multi-transcriptomic analyses to unveil the genetic association risk of regulatory T cell-mediated free cholesterol and gastric cancer

BACKGROUND

Evidence from observational studies suggests an association between free cholesterol and gastric cancer. Immune cells play a crucial role in the tumor microenvironment of gastric cancer, and free cholesterol can influence immune cells in various ways, thereby impacting gastric cancer. The mechanisms by which free cholesterol regulates and activates the immune response to exert antitumor effects, as well as the causal relationship between free cholesterol and gastric cancer, remain unclear.

METHODS

We employed a two-sample Mendelian randomization (MR) approach to investigate the causal relationship between 233 metabolites and gastric cancer. Additionally, we validated our findings using data from GWAS databases of similar traits. Using publicly available genetic data, we analyzed the causal relationship between 731 types of immune cells and gastric cancer. Furthermore, we explored the mediating role of regulatory T cells in the causal relationship between free cholesterol and gastric cancer through multivariable Mendelian randomization. Finally, we validated our results using data from the TCGA database and single-cell sequencing data.

FINDINGS

We found a causal relationship between free cholesterol levels and gastric cancer (odds ratio [OR] = 0.89, confidence interval [CI] = 0.81-0.98, P < 0.05). We also observed a causal relationship between free cholesterol levels and regulatory T cells (odds ratio [OR] = 0.86, confidence interval [CI] = 0.75-0.98, P < 0.05), and between regulatory T cells and gastric cancer (odds ratio [OR] = 1.04, confidence interval [CI] = 1.01-1.07, P < 0.05). Additionally, our multivariable Mendelian randomization analysis indicated that regulatory T cells mediate the causal relationship between free cholesterol levels and gastric cancer. Furthermore, through single-cell sequencing analysis and data analysis from the TCGA database, we found that the expression of the free cholesterol uptake protein LDLR is negatively correlated with Treg infiltration, which further influences the occurrence and development of gastric cancer.

INTERPRETATION

Our analysis indicates a causal relationship between free cholesterol levels and gastric cancer, with regulatory T cells acting as mediators. Modulating free cholesterol levels to influence regulatory T cells may offer new insights and prospects for the prevention and treatment of gastric cancer.

GPR146 regulates CYP7A1 transcription in cells and in vivo of mice

G protein-coupled receptor 146 (GPR146) plays a significant role in cholesterol metabolism in both humans and mice. Previous studies have shown that Gpr146 in mouse liver regulates cholesterol metabolism during long-term starvation, short-term starvation, and feeding conditions. Specifically, Gpr146 suppresses endogenous cholesterol synthesis and very-low-density lipoprotein secretion following feeding. However, its role in cholesterol metabolism under other feeding conditions remains unclear. The conversion of cholesterol to bile acids represents the primary pathway of cholesterol metabolism, with cytochrome P450 family 7 subfamily A member 1 (CYP7A1) serving as the critical rate-limiting enzyme. Studies have indicated that overexpression of Cyp7a1 can lower blood cholesterol levels. In this study, we systematically identified CYP7A1 as a target gene of GPR146 both in vivo and in cultured hepatocytes. Our findings revealed that silencing the expression of gpr146 in the mouse liver significantly reduced total blood cholesterol levels while markedly upregulating liver cyp7a1 expression during a 2-h fasting period. Importantly, this regulation occurs independently of farnesoid X-activated receptor (FXR)-dependent and FXR-independent cytokine pathways. These results strongly suggest that CYP7A1 is a crucial endogenous mediator of GPR146 in cholesterol metabolism both in vitro and in vivo.

Molecular architecture of human LYCHOS involved in lysosomal cholesterol signaling

Lysosomal membrane protein LYCHOS (lysosomal cholesterol signaling) translates cholesterol abundance to mammalian target of rapamycin activation. Here we report the 2.11-Å structure of human LYCHOS, revealing a unique fusion architecture comprising a G-protein-coupled receptor (GPCR)-like domain and a transporter domain that mediates homodimer assembly. The NhaA-fold transporter harbors a previously uncharacterized intramembrane Na+ pocket. The GPCR-like domain is stabilized, by analogy to canonical GPCRs, in an inactive state through 'tethered antagonism' by a lumenal loop and strong interactions at the cytosol side preventing the hallmark swing of the sixth transmembrane helix seen in active GPCRs. A cholesterol molecule and an associated docosahexaenoic acid (DHA)-phospholipid are entrapped between the transporter and GPCR-like domains, with the DHA-phospholipid occupying a pocket previously implicated in cholesterol sensing, indicating inter-domain coupling via dynamic lipid-protein interactions. Our work provides a high-resolution framework for functional investigations of the understudied LYCHOS protein.

A study into rare GPR146 gene variants in humans and mice

BACKGROUND AND AIMS

G-protein coupled receptor 146 (GPR146)-deficient mice exhibit a moderate 21 % reduction in plasma cholesterol. This is associated with decreased phosphorylation of ERK1/2 and reduced SREBP2 activity in the liver, which leads to lower VLDL secretion. Insight into the role of GPR146 in humans is however limited. We therefore set out to study rare genetic variants in GPR146 to improve our understanding of this new player in lipid metabolism.

METHODS

We used whole genome sequencing data from UK Biobank participants to search for rare coding variants in GPR146. We first carried out gene-based burden tests (using SAIGE-GENE-framework) and examined the association of individual variants with plasma cholesterol levels. One of the variants (P62L) was also studied using the Global Lipids Genetics Consortium (GLGC) data set and in a knock-in mouse model.

RESULTS

We found that the combination of rare genetic variants identified in GPR146 is significantly associated with plasma cholesterol levels. Three rare variants, i.e. P62L, I129I, and A175T were individually associated with reduced plasma cholesterol. In the GLGC cohort, the P62L variant was associated with reductions in both HDL and LDL cholesterol. Follow-up experiments show lower plasma cholesterol levels in GPR146P61L male and female mice (-13 %, p < 0.05 and -15 %, p < 0.005, respectively) when compared to controls due to a reduction in HDL cholesterol. The GPR146P61L mice did not exhibit a change in VLDL secretion. In line, the ERK1/2 signalling pathway and Srebp2 mRNA expression in liver homogenates, and the secretion of apoB by primary hepatocytes of GPR146P61L and wild-type mice were unchanged.

CONCLUSIONS

This study shows that rare GPR146 gene variants are associated with lower plasma cholesterol levels in humans. One of these variants, P62L is associated with reductions of HDL cholesterol and LDL cholesterol in humans while the ortholog in mice confers a loss of GPR146 function leading to only reduced HDL cholesterol. How GPR146 affects HDL metabolism in humans and mice remains to be resolved.

Limosilactobacillus reuteri promotes the expression and secretion of enteroendocrine- and enterocyte-derived hormones

Intestinal microbes can beneficially impact host physiology, prompting investigations into the therapeutic usage of such microbes in a range of diseases. For example, human intestinal microbe Limosilactobacillus reuteri strains ATCC PTA 6475 and DSM 17938 are being considered for use for intestinal ailments, including colic, infection, and inflammation, as well as for non-intestinal ailments, including osteoporosis, wound healing, and autism spectrum disorder. While many of their beneficial properties are attributed to suppressing inflammatory responses, we postulated that L. reuteri may also regulate intestinal hormones to affect physiology within and outside of the gut. To determine if L. reuteri secreted factors impact the secretion of enteric hormones, we treated an engineered jejunal organoid line, NGN3-HIO, which can be induced to be enriched in enteroendocrine cells, with L. reuteri 6475 or 17938 conditioned medium and performed transcriptomics. Our data suggest that these L. reuteri strains affect the transcription of many gut hormones, including vasopressin and luteinizing hormone subunit beta, which have not been previously recognized as produced in the gut epithelium. Moreover, we find that these hormones appear to be produced in enterocytes, in contrast to canonical gut hormones produced in enteroendocrine cells. Finally, we show that L. reuteri conditioned media promote the secretion of enteric hormones, including serotonin, GIP, PYY, vasopressin, and luteinizing hormone subunit beta, and identify by metabolomics metabolites potentially mediating these effects on hormones. These results support L. reuteri affecting host physiology through intestinal hormone secretion, thereby expanding our understanding of the mechanistic actions of this microbe.

A famsin-glucagon axis mediates glucose homeostasis

Glucagon is essential for glucose homeostasis, and its dysregulation is associated with diabetes. Despite extensive research, the mechanisms governing glucagon secretion remain incompletely understood. Here, we unveil that famsin, a gut-secreted hormone, promotes glucagon release and modulates glucose homeostasis. Mechanistically, famsin binds to its receptor OLFR796 in mice (OR10P1 in humans), initiating calcium release in the endoplasmic reticulum of islet α cells. This process triggers glucagon secretion, consequently promoting hepatic glucose production through glucagon signaling. Furthermore, deficiency of famsin signaling reduces hepatic glucose production and lowers blood glucose levels, underscoring the significance of the famsin-glucagon axis in glucose homeostasis. Therefore, our findings establish famsin as a crucial regulator of glucagon secretion and provide valuable insights into the intricate gut-islet-liver interorgan crosstalk that maintains glucose homeostasis.

Molecular Characteristics and Role of Buffalo SREBF2 in Triglyceride and Cholesterol Biosynthesis in Mammary Epithelial Cells

Background/Objectives: Sterol regulatory element-binding transcription factor 2 (SREBF2) is a key transcription factor involved in regulating cholesterol homeostasis. However, its role in buffalo mammary gland lipid metabolism remains unclear. Methods: To address this, we isolated and characterized the SREBF2 gene from buffalo mammary glands and performed an in-depth analysis of its molecular characteristics, tissue-specific expression, and functional roles in buffalo mammary epithelial cells (BuMECs). Additionally, we investigated the single nucleotide polymorphisms (SNPs) of SREBF2 in both river and swamp buffalo. Results: The coding sequence (CDS) of buffalo SREBF2 is 3327 bp long and encodes a protein of 1108 amino acid residues. Bioinformatics analysis revealed that the molecular characteristics of buffalo SREBF2 were highly similar across Bovidae species, with collinearity being observed among them. An expression profile analysis revealed that SREBF2 is expressed in all 11 tested tissues of buffalo, with its expression level in the mammary gland being higher during lactation than in the dry period. The knockdown of SREBF2 in BuMECs during lactation led to a significant reduction in the expression of genes involved in triglyceride (TAG) and cholesterol synthesis, including PI3K, AKT, mTOR, SREBF1, PPARG, INSIG1, ACACA, SCD, DGAT1, LPL, CD36, HMGCR, and SQLE. This knockdown led to a 23.53% and 94.56% reduction in TAG and cholesterol levels in BuMECs, respectively. In addition, a total of 22 SNPs were identified in both buffalo types, of which four non-synonymous substitutions (c.301G>C, c.304A>T, c.1240G>A, and c.2944G>A) were found exclusively in the SREBF2 CDS of swamp buffalo, and the assessment revealed that these substitutions had no impact on SREBF2 function. Conclusions: These findings emphasize the critical role of SREBF2 in regulating both triglyceride and cholesterol biosynthesis, providing valuable insights into its functions in buffalo mammary glands.

Cholesin mRNA Expression in Human Intestinal, Liver, and Adipose Tissues

OBJECTIVE

Cholesin is a recently discovered gut-derived hormone secreted by enterocytes upon dietary cholesterol uptake via the transmembrane sterol transporter Niemann-Pick disease C1-like intracellular cholesterol transporter 1 (NPC1L1). In the liver, cholesin activates G protein-coupled receptor 146 (GPR146), causing reduced cholesterol synthesis. In this exploratory, hypothesis-generating study based on post hoc analysis, human data on the cholesin system are presented.

METHODS

Mucosal biopsies were collected throughout the intestinal tract from 12 individuals with type 2 diabetes (T2D) and 12 healthy, matched controls. Upper small intestinal mucosal biopsies were collected from 20 individuals before and after Roux-en-Y gastric bypass (RYGB) surgery. Liver biopsies were collected from 12 men with obesity and 15 matched controls without obesity. Subcutaneous abdominal adipose tissue biopsies were collected from 20 men with type 1 diabetes (T1D). All biopsies underwent full mRNA sequencing.

RESULTS

Cholesin mRNA expression was observed throughout the intestinal tracts of the individuals with T2D and the controls, in the livers of men with and without obesity, and in adipose tissue of men with T1D. NPC1L1 mRNA expression was robust throughout the small intestines but negligible in the large intestines of both individuals with and without T2D. RYGB surgery induced the expression of NPC1L1 mRNA in the upper small intestine. GPR146 mRNA was expressed in the livers of men, both with and without obesity, and in the adipose tissue of men with T1D, but not in the intestines.

CONCLUSIONS

Our results suggest a role of the cholesin system in human physiology, but whether it is perturbed in metabolic diseases remains unknown.

CLINICAL TRIAL REGISTRATION NUMBERS

NCT03044860, NCT03093298, NCT02337660, NCT03734718.

Taurine alleviates dysfunction of cholesterol metabolism under hyperuricemia by inhibiting A2AR-SREBP-2/CREB/HMGCR axis

Dysfunctional cholesterol metabolism is highly prevalent in patients with hyperuricemia. Both uric acid and cholesterol are independent risk factors for atherosclerosis, contributing to an increased incidence of cardiovascular disease in hyperuricemia. Investigating the pathological mechanisms underlying cholesterol metabolism dysfunction in hyperuricemia is essential. This study identified adenosine and inosine, two major purine metabolites, as key regulators of cholesterol biosynthesis. These metabolites upregulate 3-hydroxy-3-methylglutaryl-CoA. Further mechanistic studies revealed that adenosine/inosine up-regulated the expression of 3-hydroxy-3-methylglutaryl-CoA by activating adenosine A2A receptor via the Srebp-2/Creb axis in hyperuricemia. Additionally, we found that taurine deficiency contributes to cholesterol metabolism dysfunction in hyperuricemia. Taurine administration in hyperuricemia mice significantly reduced cholesterol elevation by inhibiting adenosine A2A receptor. This study provides a promising strategy for treating comorbid hypercholesterolemia and hyperuricemia.

Genetic evidence for the causal effects of air pollution on the risk of respiratory diseases

BACKGROUND

Epidemiological studies have consistently demonstrated a robust association between long-term exposure to air pollutants and respiratory diseases. However, establishing causal relationships remains challenging due to residual confounding in observational studies. In this study, Mendelian randomization (MR) analysis was used to explore the causal and epigenetic relationships between various air pollutants and common respiratory diseases.

METHODS

We utilized a two-sample Mendelian randomization (TSMR) approach to explore the impact of PM2.5, PM2.5-10, PM10, NO2, and NOX on the incidence of nine respiratory diseases using data from large-scale European GWAS datasets (N = 423,796-456,380 for exposures; N = 162,962-486,484 for outcomes). The primary analytical method was inverse variance weighting (IVW), which explored the exposure-outcome relationship using single nucleotide polymorphisms (SNPs) associated with air pollution. Sensitivity analyses, including MR-Egger regression and leave-one-out analyses, were employed to ensure result consistency. Multivariate MR (MVMR) was performed to adjust for potential smoking-related confounders, such as cigarettes per day, household smoking, exposure to tobacco smoke at home, ever smoked, second-hand smoke, smoking initiation, and age at smoking initiation, as well as the independent effects of each air pollutant. Additionally, methylation and enrichment analyses were conducted to further elucidate the potential effects of air pollution on respiratory diseases.

RESULTS

TSMR analysis revealed that exposure to PM2.5 increased the risk of early-onset chronic obstructive pulmonary disease (COPD), pneumonia, pulmonary embolism and lung cancer. PM2.5-10 exposure was associated with an increased risk of lung cancer, while PM10 exposure increased the risk of pneumonia and bronchiectasis. NO2 exposure was associated with increased risks of lung cancer and adult asthma. Importantly, these associations remained robust even after controlling for potential tobacco-related confounders in the MVMR analyses. In the MVMR analysis adjusting for other pollutants, significant associations persisted between PM2.5 and early-onset COPD, and between PM10 and pneumonia. Genetic co-localization analyses confirmed that methylation of PM2.5-associated CpG loci (cg11386376 near c1orf175, cg11846064 near rfx2, cg18612040 near rptor, and cg19765378 near c7orf50) was associated with an increased risk of early-onset COPD. Finally, SNPs significantly associated with exposure and outcome were selected for enrichment analysis.

CONCLUSIONS

Our findings suggest that exposure to air pollutants may play a causal role in the development of respiratory diseases, with a potential role of epigenomic modifications emphasized. Strengthening comprehensive air pollution regulations by relevant authorities could potentially mitigate the risk of these diseases.

From Genetic Findings to new Intestinal Molecular Targets in Lipid Metabolism

PURPOSE OF REVIEW

While lipid-lowering therapies demonstrate efficacy, many patients still contend with significant residual risk of atherosclerotic cardiovascular diseases (ASCVD). The intestine plays a pivotal role in regulating circulating lipoproteins levels, thereby exerting influence on ASCVD pathogenesis. This review underscores recent genetic findings from the last six years that delineate new biological pathways and actors in the intestine which regulate lipid-related ASCVD risk.

RECENT FINDINGS

Specifically, we detail the role of LIMA1 in cholesterol absorption within enterocytes, the function of PLA2G12B in the expansion and lipidation of chylomicrons, the involvement of SURF4 in lipoprotein secretion, and the discovery of a gut-derived hormone named CHOLESIN that modulates cholesterol homeostasis through GPR146 via a gut-liver crosstalk. We further discuss the potential of these newly identified genes and pathways as novel targets for pharmaceutical intervention. Newly identified genetic and intestinal molecular mechanisms offer promising opportunities for preventing and treating ASCVD, but careful evaluation and further research are needed to optimize their clinical application.

Probiotics as Potential Treatments for Neurodegenerative Diseases: a Review of the Evidence from in vivo to Clinical Trial

Neurodegenerative diseases (NDDs), characterized by the progressive deterioration of the structure and function of the nervous system, represent a significant global health challenge. Emerging research suggests that the gut microbiota plays a critical role in regulating neurodegeneration via modulation of the gut-brain axis. Probiotics, defined as live microorganisms that confer health benefits to the host, have garnered significant attention owing to their therapeutic potential in NDDs. This review examines the current research trends related to the microbiome-gut-brain axis across various NDDs, highlighting key findings and their implications. Additionally, the effects of specific probiotic strains, including Lactobacillus plantarum, Bifidobacterium breve, and Lactobacillus rhamnosus, on neurodegenerative processes were assessed, focusing on their potential therapeutic benefits. Overall, this review emphasizes the potential of probiotics as promising therapeutic agents for NDDs, underscoring the importance of further investigation into this emerging field.

Gut‑liver axis in liver disease: From basic science to clinical treatment (Review)

Incidence of a number of liver diseases has increased. Gut microbiota serves a role in the pathogenesis of hepatitis, cirrhosis and liver cancer. Gut microbiota is considered 'a new virtual metabolic organ'. The interaction between the gut microbiota and liver is termed the gut‑liver axis. The gut‑liver axis provides a novel research direction for mechanism of liver disease development. The present review discusses the role of the gut‑liver axis and how this can be targeted by novel treatments for common liver diseases.

Cellular Feimin enhances exercise performance by suppressing muscle thermogenesis

Exercise can rapidly increase core body temperature, and research has indicated that elevated internal body temperature can independently contribute to fatigue during physical activity. However, the precise mechanisms responsible for regulating thermogenesis in muscles during exercise have remained unclear. Here, we demonstrate that cellular Feimin (cFeimin) enhances exercise performance by inhibiting muscle thermogenesis during physical activity. Mechanistically, we found that AMP-activated protein kinase (AMPK) phosphorylates cFeimin and facilitates its translocation into the cell nucleus during exercise. Within the nucleus, cFeimin binds to the forkhead transcription factor FOXC2, leading to the suppressed expression of sarcolipin (Sln), which is a key regulator of muscle thermogenesis. In addition, our results further reveal that short-term AMPK agonist treatments can enhance exercise performance through the activation of the AMPK-cFeimin signalling pathway. In summary, these results underscore the crucial role of cFeimin in enhancing exercise performance by modulating SLN-mediated thermogenesis.

A feeding-induced myokine modulates glucose homeostasis

Maintaining blood glucose homeostasis during fasting and feeding is crucial for the prevention of dysregulation that can lead to either hypo- or hyperglycaemia. Here we identified feimin, encoded by a gene with a previously unknown function (B230219D22Rik in mice, C5orf24 in humans), as a key modulator of glucose homeostasis. Feimin is secreted from skeletal muscle during feeding and binds to its receptor, receptor protein tyrosine kinase Mer (MERTK), promoting glucose uptake and inhibiting glucose production by activation of AKT. Administration of feimin and insulin synergistically improves blood glucose homeostasis in both normal and diabetic mice. Notably, a specific single nucleotide polymorphism (rs7604639, G>A) within the MERTK gene, causing an amino acid substitution (R466K) within the feimin-MERTK binding region, leads to reduced association with feimin and elevated postprandial blood glucose and insulin levels in humans. Our findings underscore a role of the feimin-MERTK signalling axis in glucose homeostasis, providing valuable insights into potential therapeutic avenues for diabetes.

Protocol to identify receptors of secreted proteins through CRISPR-Cas9 whole-genome screening technology

The interaction between cell surface receptors and their ligands is crucial for intercellular communication. However, current techniques for identifying direct receptor-ligand interactions remain limited. Here, we present a protocol to identify receptors of secreted proteins using a genome-scale CRISPR-Cas9 knockout genetic screening approach. We describe steps for creating a single-guide RNA (sgRNA) lentivirus library, infecting stable Cas9-MCF7 cells, staining with tagged Cholesin, and sorting non-binding cells via flow cytometry. We then detail procedures for extracting DNA, amplifying sgRNAs, and sequencing. For complete details on the use and execution of this protocol, please refer to Hu et al.1.

Drugs for dyslipidaemia: the legacy effect of the Scandinavian Simvastatin Survival Study (4S)

Since the discovery of statins and the Scandinavian Simvastatin Survival Study (4S) results three decades ago, remarkable advances have been made in the treatment of dyslipidaemia, a major risk factor for atherosclerotic cardiovascular disease. Safe and effective statins remain the cornerstone of therapeutic approach for this indication, including for children with genetic dyslipidaemia, and are one of the most widely prescribed drugs in the world. However, despite the affordability of generic statins, they remain underutilised worldwide. The use of ezetimibe to further decrease plasma LDL cholesterol and the targeting of other atherogenic lipoproteins, such as triglyceride-rich lipoproteins and lipoprotein(a), are likely to be required to further reduce atherosclerotic cardiovascular disease events. Drugs directed at these lipoproteins, including gene silencing and editing methods that durably suppress the production of proteins, such as PCSK9 and ANGPTL3, open novel therapeutic options to further reduce the development of atherosclerotic cardiovascular disease.

A data mining approach to identify key radioresponsive genes in mouse model of radiation-induced intestinal injury

BACKGROUND

Radiation-mediated GI injury (RIGI) is observed in humans either due to accidental or intentional exposures. This can only be managed with supporting care and no approved countermeasures are available till now. Early detection and monitoring of RIGI is important for effective medical management and improve survival chances of exposed individuals.

OBJECTIVE

The present study aims to identify new signatures of RIGI using data mining approach followed by validation of selected hub genes in mice.

METHODS

Data mining study was performed using microarray datasets from Gene Expression Omnibus database. The differentially expressed genes were identified and further validated in total-body irradiated mice.

RESULTS

Based on KEGG pathway analysis, lipid metabolism was found as one of the predominant pathways altered in irradiated intestine. Extensive alteration in lipid profile and lipid modification was observed in this tissue. A protein-protein interaction network revealed top 08 hub genes related to lipid metabolism, namely Fabp1, Fabp2, Fabp6, Npc1l1, Ppar-α, Abcg8, Hnf-4α, and Insig1. qRT-PCR analysis revealed significant up-regulation of Fabp6 and Hnf-4α and down-regulation of Fabp1, Fabp2 and Insig1 transcripts in irradiated intestine. Radiation dose and time kinetics study revealed that the selected 05 genes were altered differentially in response to radiation in intestine.

CONCLUSION

Finding suggests that lipid metabolism is one of the key targets of radiation and its mediators may act as biomarkers in detection and progression of RIGI.

Molecular Regulation and Therapeutic Targeting of VLDL Production in Cardiometabolic Disease

There exists a complex relationship between steatotic liver disease (SLD) and atherosclerotic cardiovascular disease (CVD). CVD is a leading cause of morbidity and mortality among individuals with SLD, particularly those with metabolic dysfunction-associated SLD (MASLD), a significant proportion of whom also exhibit features of insulin resistance. Recent evidence supports an expanded role of very low-density lipoprotein (VLDL) in the pathogenesis of CVD in patients, both with and without associated metabolic dysfunction. VLDL represents the major vehicle for exporting neutral lipid from hepatocytes, with each particle containing one molecule of apolipoproteinB100 (APOB100). VLDL production becomes dysregulated under conditions characteristic of MASLD including steatosis and insulin resistance. Insulin resistance not only affects VLDL production but also mediates the pathogenesis of atherosclerotic CVD. VLDL assembly and secretion therefore represents an important pathway in the setting of cardiometabolic disease and offers several candidates for therapeutic targeting, particularly in metabolically complex patients with MASLD at increased risk of atherosclerotic CVD. Here we review the clinical significance as well as the translational and therapeutic potential of key regulatory steps impacting VLDL initiation, maturation, secretion, catabolism, and clearance.

Limosilactobacillus reuteri promotes the expression and secretion of enteroendocrine- and enterocyte-derived hormones

Observations that intestinal microbes can beneficially impact host physiology have prompted investigations into the therapeutic usage of such microbes in a range of diseases. For example, the human intestinal microbe Limosilactobacillus reuteri strains ATCC PTA 6475 and DSM 17938 are being considered for use for intestinal ailments including colic, infection, and inflammation as well as non-intestinal ailments including osteoporosis, wound healing, and autism spectrum disorder. While many of their beneficial properties are attributed to suppressing inflammatory responses in the gut, we postulated that L. reuteri may also regulate hormones of the gastrointestinal tract to affect physiology within and outside of the gut. To determine if L. reuteri secreted factors impact the secretion of enteric hormones, we treated an engineered jejunal organoid line, NGN3-HIO, which can be induced to be enriched in enteroendocrine cells, with L. reuteri 6475 or 17938 conditioned medium and performed transcriptomics. Our data suggest that these L. reuteri strains affect the transcription of many gut hormones, including vasopressin and luteinizing hormone subunit beta, which have not been previously recognized as being produced in the gut epithelium. Moreover, we find that these hormones appear to be produced in enterocytes, in contrast to canonical gut hormones which are produced in enteroendocrine cells. Finally, we show that L. reuteri conditioned media promotes the secretion of several enteric hormones including serotonin, GIP, PYY, vasopressin, and luteinizing hormone subunit beta. These results support L. reuteri affecting host physiology through intestinal hormone secretion, thereby expanding our understanding of the mechanistic actions of this microbe.

Cholesin and GPR146 in Modulating Cholesterol Biosynthesis

BACKGROUND

Cholesterol homeostasis in the human body is a crucial process that involves a delicate balance between dietary cholesterol absorption in the intestine and de novo cholesterol synthesis in the liver. Both pathways contribute significantly to the overall pool of cholesterol in the body, influencing plasma cholesterol levels and impacting cardiovascular health. Elevated absorption of cholesterol in the intestines has a suppressive impact on the synthesis of cholesterol in the liver, serving to preserve cholesterol balance. Nonetheless, the precise mechanisms driving this phenomenon remain largely unclear.

SUMMARY

This review aimed to discuss the previously unrecognized role of cholesin and GPR146 in the regulation of cholesterol biosynthesis, providing a novel conceptual framework for understanding cholesterol homeostasis.

KEY MESSAGES

The discovery of cholesin, a novel protein implicated in the regulation of cholesterol homeostasis, represents a significant advancement in our understanding of cholesterol biosynthesis and its associated pathways. The cholesin-GPR146 axis could have profound implications across various therapeutic areas concerning abnormal cholesterol metabolism, offering new hope for patients and improving overall healthcare outcomes.

Cholesin receptor signalling is active in cardiovascular system-associated adipose tissue and correlates with SGLT2i treatment in patients with diabetes

BACKGROUND

Recently deorphanized G protein-coupled receptor 146 (GPR146) was shown to respond to signal from a newly identified hormone-cholesin-and to play a role in hepatic lipid metabolism. However, the importance of its biological activity in human organism remains elusive, mainly due to the lack of studies on human tissues up to this point. This study aimed to identify the cholesin receptor-associated genes and clinical factors linked with their expression in cardiovascular system and associated adipose tissues.

METHODS

Right cardiac auricle, aortic wall, saphenous vein, and adipose tissue (periaortic-PAT, epicardial-EAT, thymic-TAT) samples were collected during coronary artery bypass grafting. Clinical records of the study participants were assessed for the presence of diabetes, medications taken and serum cholesterol levels. GPR146 mRNA expression in all gathered tissues was assessed with qPCR, and RNA seqencing was performed in selected tissues of 20 individuals to identify pathways associated with GPR146 expression.

RESULTS

We included 46 participants [37 male, 23 with type 2 diabetes, median age 68.50 (Q1-Q3: 63.00-72.00) years, BMI 28.39 (26.06-31.49) kg/m2]. GPR146 expression in adipose tissues significantly correlated with BMI, c-peptide, total cholesterol, and LDL concentrations. Selected metabolic pathways were significantly and positively enriched in GPR146-dependent manner. GPR146-coexpressed genes contained key regulators of lipid metabolism involved in such pathways as fatty acid metabolism, tricarboxilic acid cycle and peroxisomal metabolism. Those genes correlated positively with serum concentrations of LDL, HDL, and total cholesterol. SGLT2i treatment was associated with inversion of GPR146-related signature in EAT, suggesting potential impact on cholesin-GPR146 network.

CONCLUSIONS

GPR146 expression is associated with serum lipids and metabolically-relevant transcriptomic changes in EAT similar to SGLT2i-associated ones.

Genome wide association study and genomic risk prediction of age related macular degeneration in Israel

The risk of developing age-related macular degeneration (AMD) is influenced by genetic background. In 2016, the International AMD Genomics Consortium (IAMDGC) identified 52 risk variants in 34 loci, and a polygenic risk score (PRS) from these variants was associated with AMD. The Israeli population has a unique genetic composition: Ashkenazi Jewish (AJ), Jewish non-Ashkenazi, and Arab sub-populations. We aimed to perform a genome-wide association study (GWAS) for AMD in Israel, and to evaluate PRSs for AMD. Our discovery set recruited 403 AMD patients and 256 controls at Hadassah Medical Center. We genotyped individuals via custom exome chip. We imputed non-typed variants using cosmopolitan and AJ reference panels. We recruited additional 155 cases and 69 controls for validation. To evaluate predictive power of PRSs for AMD, we used IAMDGC summary-statistics excluding our study and developed PRSs via clumping/thresholding or LDpred2. In our discovery set, 31/34 loci reported by IAMDGC were AMD-associated (P < 0.05). Of those, all effects were directionally consistent with IAMDGC and 11 loci had a P-value under Bonferroni-corrected threshold (0.05/34 = 0.0015). At a 5 × 10-5 threshold, we discovered four suggestive associations in FAM189A1, IGDCC4, C7orf50, and CNTNAP4. Only the FAM189A1 variant was AMD-associated in the replication cohort after Bonferroni-correction. A prediction model including LDpred2-based PRS + covariates had an AUC of 0.82 (95% CI 0.79-0.85) and performed better than covariates-only model (P = 5.1 × 10-9). Therefore, previously reported AMD-associated loci were nominally associated with AMD in Israel. A PRS developed based on a large international study is predictive in Israeli populations.