Obesity Induces Disruption of Microvascular Endothelial Circadian Rhythm

The evolving functions of the vasculature in regulating adipose tissue biology in health and obesity

Adipose tissue is an endocrine organ and a crucial regulator of energy storage and systemic metabolic homeostasis. Additionally, adipose tissue is a pivotal regulator of cardiovascular health and disease, mediated in part by the endocrine and paracrine secretion of several bioactive products, such as adipokines. Adipose vasculature has an instrumental role in the modulation of adipose tissue expansion, homeostasis and metabolism. The role of the adipose vasculature has been extensively explored in the context of obesity, which is recognized as a global health problem. Obesity-induced accumulation of fat, in combination with vascular rarefaction, promotes adipocyte dysfunction and induces oxidative stress, hypoxia and inflammation. It is now recognized that obesity-associated endothelial dysfunction often precedes the development of cardiovascular diseases. Investigations have revealed heterogeneity within the vascular niche and dynamic reciprocity between vascular and adipose cells, which can become dysregulated in obesity. Here we provide a comprehensive overview of the evolving functions of the vasculature in regulating adipose tissue biology in health and obesity.

Circadian rhythm in cardiovascular diseases: a bibliometric analysis of the past, present, and future

BACKGROUND

One of the most prominent features of living organisms is their circadian rhythm, which governs a wide range of physiological processes and plays a critical role in maintaining optimal health and function in response to daily environmental changes. This work applied bibliometric analysis to explore quantitative and qualitative trends in circadian rhythm in cardiovascular diseases (CVD). It also aims to identify research hotspots and provide fresh suggestions for future research.

METHODS

The Web of Science Core Collection was used to search the data on circadian rhythm in CVD. HistCite, CiteSpace, and VOSviewer were used for bibliometric analysis and visualization. The analysis included the overall distribution of yearly outputs, top nations, active institutions and authors, core journals, co-cited references, and keywords. To assess the quality and efficacy of publications, the total global citation score (TGCS) and total local citation score (TLCS) were calculated.

RESULTS

There were 2102 papers found to be associated with the circadian rhythm in CVD, with the overall number of publications increasing year after year. The United States had the most research citations and was the most prolific country. Hermida RC, Young ME, and Ayala DE were the top three writers. The three most notable journals on the subject were Chronobiology International, Hypertension Research, and Hypertension. In the early years, the major emphasis of circadian rhythm in CVD was hormones. Inflammation, atherosclerosis, and myocardial infarction were the top developing research hotspots.

CONCLUSION

Circadian rhythm in CVD has recently received a lot of interest from the medical field. These topics, namely inflammation, atherosclerosis, and myocardial infarction, are critical areas of investigation for understanding the role of circadian rhythm in CVD. Although they may not be future research priorities, they remain of significant importance. In addition, how to implement these chronotherapy theories in clinical practice will depend on additional clinical trials to get sufficient trustworthy clinical evidence.

The biological clock enhancer nobiletin ameliorates steatosis in genetically obese mice by restoring aberrant hepatic circadian rhythm

Nonalcoholic fatty liver disease (NAFLD) is associated with disruption of homeostatic lipid metabolism, but underlying processes are poorly understood. One possible mechanism is impairment in hepatic circadian rhythm, which regulates key lipogenic mediators in the liver and whose circadian oscillation is diminished in obesity. Nobiletin enhances biological rhythms by activating RAR-related orphan receptor nuclear receptor, protecting against metabolic syndrome in a clock-dependent manner. The effect of nobiletin in NAFLD is unclear. In this study, we investigate the clock-enhancing effects of nobiletin in genetically obese (db/db) PER2::LUCIFERASE reporter mice with fatty liver. We report microarray expression data suggesting hepatic circadian signaling is impaired in db/db mice with profound hepatic steatosis. Circadian PER2 activity, as assessed by mRNA and luciferase assay, was significantly diminished in liver of db/db PER2::LUCIFERASE reporter mice. Continuous animal monitoring systems and constant dark studies suggest the primary circadian defect in db/db mice lies within peripheral hepatic oscillators and not behavioral rhythms or the master clock. In vitro, nobiletin restored PER2 amplitude in lipid-laden PER2::LUCIFERASE reporter macrophages. In vivo, nobiletin dramatically upregulated core clock gene expression, hepatic PER2 activity, and ameliorated steatosis in db/db PER2::LUCIFERASE reporter mice. Mechanistically, nobiletin reduced serum insulin levels, decreased hepatic Srebp1c, Acaca1, Tnfα, and Fgf21 expression, but did not improve Plin2, Plin5, or Cpt1, suggesting nobiletin attenuates steatosis in db/db mice via downregulation of hepatic lipid accumulation. These data suggest restoring endogenous rhythm with nobiletin resolves steatosis in obesity, proposing that hypothesis that targeting the biological clock may be an attractive therapeutic strategy for NAFLD.NEW & NOTEWORTHY NAFLD is the most common chronic liver disease, but underlying mechanisms are unclear. We show here that genetically obese (db/db) mice with fatty liver have impaired hepatic circadian rhythm. Hepatic Per2 expression and PER2 reporter activity are diminished in db/db PER2::LUCIFERASE mice. The biological clock-enhancer nobiletin restores hepatic PER2 in db/db PER2::LUCIFERASE mice, resolving steatosis via downregulation of Srebp1c. These studies suggest targeting the circadian clock may be beneficial strategy in NAFLD.