Inter-organ communication involved in metabolic regulation at the whole-body level

Colonic inflammation triggers β cell proliferation during obesity development via a liver-to-pancreas interorgan mechanism

Under insulin-resistant conditions, such as obesity, pancreatic β cells adaptively proliferate and secrete more insulin to prevent blood glucose elevation. We previously reported hepatic ERK activation during obesity development to stimulate a neuronal relay system, consisting of afferent splanchnic nerves from the liver and efferent vagal nerves to the pancreas, thereby triggering adaptive β cell proliferation. However, the mechanism linking obesity with the interorgan system originating in hepatic ERK activation remains unclear. Herein, we clarified that colonic inflammation promotes β cell proliferation through this interorgan system from the liver to the pancreas. First, dextran sodium sulfate (DSS) treatment induced colonic inflammation and hepatic ERK activation as well as β cell proliferation, all of which were suppressed by blockades of the neuronal relay system by several approaches. In addition, treatment with anti-lymphocyte Peyer's patch adhesion molecule-1 (anti-LPAM1) antibody suppressed β cell proliferation induced by DSS treatment. Importantly, high-fat diet (HFD) feeding also elicited colonic inflammation, and its inhibition by anti-LPAM1 antibody administration suppressed hepatic ERK activation and β cell proliferation induced by HFD. Thus, colonic inflammation triggers adaptive β cell proliferation via the interorgan mechanism originating in hepatic ERK activation. The present study revealed a potentially novel role of the gastrointestinal tract in the maintenance of β cell regulation.

Liver Neurobiology: Regulation of Liver Functions by the Nervous System

The nervous system plays an important role in the regulation of liver functions during physiological as well as pathological conditions. This regulatory effect is based on the processing of signals transmitted to the brain by sensory nerves innervating the liver tissue and other visceral organs and by humoral pathways transmitting signals from peripheral tissues and organs. Based on these signals, the brain modulates metabolism, detoxification, regeneration, repair, inflammation, and other processes occurring in the liver. The nervous system thus determines the functional and morphological characteristics of the liver. Liver innervation also mediates the influence of psychosocial factors on liver functions. The aim of this review is to describe complexity of bidirectional interactions between the brain and liver and to characterize the mechanisms and pathways through which the nervous system influences liver function during physiological conditions and maintains liver and systemic homeostasis.

Intercellular communication is crucial in the regulation of healthy aging via exosomes

The hallmarks of aging encompass a variety of molecular categories (genomic, telomeric, and epigenetic), organelles (proteostasis, autophagy, and mitochondria), cellular components (including stem cells), systems (such as intercellular communication and chronic inflammation), and environmental factors (dysbiosis and nutrient sensing). These hallmarks play a crucial role in the aging process. Despite their intricate interconnections, the relationships among the hallmarks of aging remain unclear. Although the boundaries between these hallmarks may be indistinct, they exhibit interdependence, with the influence of one hallmark extending to others. Building on this foundation, we investigated the interrelations among the various hallmarks of aging and provided a systematic overview of their logical relationships, proposing that cellular communication plays a crucial role in the aging process. Exosomes function as a primary mode of cellular communication and significantly impact the aging process. Therefore, we propose utilizing exosomes as valuable tools for understanding the mechanisms of aging and addressing age-related concerns. Exosomes may represent a novel approach for the treatment and diagnosis of aging-related conditions in animals. Furthermore, our research reveals that exocytosis in young nematodes slows the aging process, while exocytosis in aged nematodes has the opposite effect, accelerating aging. In conclusion, exosomes act as intercellular messengers that influence the maintenance of a healthy aging process and link the hallmarks of aging with indicators of well-being.

Endothelial c-Myc knockout disrupts metabolic homeostasis and triggers the development of obesity

Introduction: Obesity is a major risk factor associated with multiple pathological conditions including diabetes and cardiovascular disease. Endothelial dysfunction is an early predictor of obesity. However, little is known regarding how early endothelial changes trigger obesity. In the present work we report a novel endothelial-mediated mechanism essential for regulation of metabolic homeostasis, driven by c-Myc. Methods: We used conditional knockout (EC-Myc KO) and overexpression (EC-Myc OE) mouse models to investigate the endothelial-specific role of c-Myc in metabolic homeostasis during aging and high-fat diet exposure. Body weight and metabolic parameters were collected over time and tissue samples collected at endpoint for biochemical, pathology and RNA-sequencing analysis. Animals exposed to high-fat diet were also evaluated for cardiac dysfunction. Results: In the present study we demonstrate that EC-Myc KO triggers endothelial dysfunction, which precedes progressive increase in body weight during aging, under normal dietary conditions. At endpoint, EC-Myc KO animals showed significant increase in white adipose tissue mass relative to control littermates, which was associated with sex-specific changes in whole body metabolism and increase in systemic leptin. Overexpression of endothelial c-Myc attenuated diet-induced obesity and visceral fat accumulation and prevented the development of glucose intolerance and cardiac dysfunction. Transcriptome analysis of skeletal muscle suggests that the protective effects promoted by endothelial c-Myc overexpression are associated with the expression of genes known to increase weight loss, energy expenditure and glucose tolerance. Conclusion: Our results show a novel important role for endothelial c-Myc in regulating metabolic homeostasis and suggests its potential targeting in preventing obesity and associated complications such as diabetes type-2 and cardiovascular dysfunction.

Metabolite correlation permutation after mice acute exposure to PM2.5: Holistic exploration of toxicometabolomics by network analysis

Many environmental toxicants can cause systemic effects, such as fine particulate matter (PM2.5), which can penetrate the respiratory barrier and induce effects in multiple tissues. Although metabolomics has been used to identify biomarkers for PM2.5, its multi-tissue toxicology has not yet been explored holistically. Our objective is to explore PM2.5 induced metabolic alterations and unveil the intra-tissue responses along with inter-tissue communicational effects. In this study, following a single intratracheal instillation of multiple doses (0, 25, and 150 μg as the control, low, and high dose), non-targeted metabolomics was employed to evaluate the metabolic impact of PM2.5 across multiple tissues. PM2.5 induced tissue-specific and dose-dependent disturbances of metabolites and their pathways. The remarkable increase of both intra- and inter-tissue correlations was observed, with emphasis on the metabolism connectivity among lung, spleen, and heart; the tissues' functional specificity has marked their toxic modes. Beyond the inter-status comparison of the metabolite fold-changes, the current correlation network built on intra-status can offer additional insights into how the multiple tissues and their metabolites coordinately change in response to external stimuli such as PM2.5 exposure.