Proper adipose tissue homeostasis is essential for systemic metabolic health, and its disruption promotes insulin resistance, inflammation, and cardiometabolic risk. Using unbiased systems genetics analyses in mice and humans identified ITIH5 as a central regulator of adipose homeostasis and whole-body metabolism. Acute administration of recombinant ITIH5 with pan-organ sequencing revealed a local adipose function, suppressing recruitment of circulating immune cells. Consistently, ITIH5 treatment in human endothelial cells reduced leukocyte recruitment. We generated temporally controlled, adipocyte-specific ITIH5 overexpression models in mice, which improved adipose architecture, glucose metabolism under high-fat diet conditions, while consistently reducing left ventricular mass and cardiac output regardless of dietary group.. Spatial transcriptomics of adipose tissue showed that elevated ITIH5 signaling to endothelia selectively impairs dendritic cell (DC) and B cell activation pathways. Collectively, these findings identify a mechanism whereby natural genetic variation in an adipocyte-secreted protein modulates endothelial–immune interactions in fat, influencing cardiometabolic homeostasis in a diet-dependent manner.

Circadian rhythms are integral to maintaining metabolic health by temporally coordinating physiology across tissues. However, the mechanisms underlying circadian cross-tissue coordination remain poorly understood. In this study, we uncover a central role for the liver clock in regulating circadian rhythms in white adipose tissue (WAT). Using a hepatocyte-specific Bmal1 knockout mouse model, we show that hepatic circadian control modulates lipid metabolism in WAT. In addition, by utilizing a model where functional clocks are restricted to the hepatocytes, we demonstrate that the liver clock alone integrates feeding cues to modulate circadian gene expression in WAT, including Cebpa, a key regulator of adipogenesis. We show that the hepatocyte clock regulates adipocyte Cebpa rhythmicity through secreted proteins. Further investigation identified one of the contributing mediators to be the adaptor protein 14-3-3η (Ywhah). The clinical relevance of the liver clock for systemic metabolic function is supported by human cohort data, which revealed a gene regulatory network, consisting of several clock-controlled liver genes, linked to cardiometabolic risk. These findings provide evidence for how the hepatocyte clock coordinates WAT physiology and highlights the core clock system as a potential therapeutic target to improve cardiometabolic health.

Mammalian organs continuously produce and consume circulating metabolites for organismal health and survival. However, the landscape of this fundamental process and its perturbation by diet and disease is unknown. Using arteriovenous metabolomics, tissue transcriptomics, and hormone arrays in multiple pathophysiological conditions in pigs, we generated an atlas of 10 cross-organ metabolite production and consumption during fasting/feeding, Western diet, and cardiovascular disease progression induced by low-density lipoprotein receptor (LDLR) deficiency. We discovered numerous instances of feeding-dependent and -independent metabolite production and consumption by organs and proposed mechanisms by which these are disrupted by Western diet via altered metabolite concentration gradients and hormones. Both Western diet and LDLR deficiency trigger the release of bile acids (BAs) by extra-hepatic organs, likely contributing to abnormally elevated circulating BA levels and consequent vascular inflammation and atherosclerosis development. These resources reveal intricate inter-organ metabolic crosstalk across pathophysiological conditions, offering biochemical insights into diet effects and cardiometabolic diseases.

In mammals, the circadian clock network drives daily rhythms of tissue-specific homeostasis. To dissect daily inter-tissue communication, we constructed a mouse minimal clock network comprising only two nodes: the peripheral epidermal clock and the central brain clock. By transcriptomic and functional characterization of this isolated connection, we identified a gatekeeping function of the peripheral tissue clock with respect to systemic inputs. The epidermal clock concurrently integrates and subverts brain signals to ensure timely execution of epidermal daily physiology. Timely cell-cycle termination in the epidermal stem cell compartment depends upon incorporation of clock-driven signals originating from the brain. In contrast, the epidermal clock corrects or outcompetes potentially disruptive feeding-related signals to ensure the optimal timing of DNA replication. Together, we present an approach for cataloging the systemic dependencies of daily temporal organization in a tissue and identify an essential gate-keeping function of peripheral circadian clocks that guarantees tissue homeostasis.

Background: Chronic stress has a profound impact on circadian regulation of physiology. In turn, disruption of circadian rhythms increases the risk of developing both psychiatric and metabolic disorders. To explore the role of chronic stress in modulating the links between neural and metabolic rhythms, we characterized the circadian transcriptional regulation across different brain regions and the liver as well as serum metabolomics in mice exposed to chronic social defeat stress, a validated model for studying depressive-like behaviors. Methods: Male C57BL/6J mice underwent chronic social defeat stress, and subsequent social interaction screening identified distinct behavioral phenotypes associated with stress resilience and susceptibility. Stressed mice and their control littermates were sacrificed every 4 hours over the circadian cycle for comprehensive analyses of the circadian transcriptome in the hypothalamus, hippocampus, prefrontal cortex, and liver together with assessments of the circadian circulatory metabolome. Results: Our data demonstrate that stress adaptation was characterized by reprogramming of the brain as well as the hepatic circadian transcriptome. Stress resiliency was associated with an increase in cyclic transcription in the hypothalamus, hippocampus, and liver. Furthermore, cross-tissue analyses revealed that resilient mice had enhanced transcriptional coordination of circadian pathways between the brain and liver. Conversely, susceptibility to social stress resulted in a loss of cross-tissue coordination. Circadian serum metabolomic profiles corroborated the transcriptome data, highlighting that stress-resilient mice gained circadian rhythmicity of circulating metabolites, including bile acids and sphingomyelins. Conclusions: This study reveals that resilience to stress is characterized by enhanced metabolic rhythms and circadian brain-liver transcriptional coordination.

Adipose tissue (AT) is highly responsive to nutrient delivery associated with conventional feed/fast cycles over 24 hr and also has a molecular circadian clock that regulates transcriptional rhythms. The joint contribution of these dual inputs to human AT function has not been studied, nor how this interplay changes in obesity. Ten lean (BMI 20-25 kg/m2) and 7 people with upper body obesity (UBO) (BMI 30-35 kg/m2) were within group randomized to either continuous feeding (“CONT”) or intermittent feeding (“INT”) of Ensure via nasogastric tube (NG). CONT was fed at rates to meet 24 hr caloric needs and INT fed 3 evenly spaced feedings (1/3 of daily caloric needs per meal) during daylight hours and fasted overnight. Each person received 4 abdominal AT biopsies across 24 hr. We performed RNA-Seq analysis on AT samples; dryR was used to assess circadian rhythmicity of genes differential between groups and GO and ClusterProfiler for pathway analysis. Most rhythmic genes were driven by feed/fast cycles, 538 transcripts were significantly rhythmic in INT groups and lost rhythmicity in CONT groups (adj. P <0.02)(BICW > 0.1). These genes were enriched for lipid metabolism pathways including biosynthesis and oxidation. Many genes (237) were significantly rhythmic in lean and not UBO individuals regardless of feeding regime (adj. P<0.05)(BICW > 0.1), these were enriched for pathways related to immune response. 399 genes were significantly rhythmic (adj. P<0.02)(BICW > 0.13) in lean CONT and INT and UBO INT, but lost rhythmicity only in UBO CONT. These were enriched for metabolic pathways related to glucose and carbohydrate homeostasis and molecular circadian system. Overall, the fast/feed cycle over 24 hr drives a significant portion of AT gene rhythmicity. Our data suggests lean individuals maintain AT clock system integrity independent of feeding time while patients with UBO require feed-fast cycles to sustain AT clock circadian rhythmicity, suggesting feeding time might be particularly relevant for patients with obesity. Disclosure K. Lytle: None. P. Petrus: None. C. Savva: None. M.D. Jensen: Advisory Panel; Biohaven.

Glutamine and glutamate are interconverted by several enzymes and alterations in this metabolic cycle are linked to cardiometabolic traits. Herein, we show that obesity-associated insulin resistance is characterized by decreased plasma and white adipose tissue glutamine-to-glutamate ratios. We couple these stoichiometric changes to perturbed fat cell glutaminase and glutamine synthase messenger RNA and protein abundance, which together promote glutaminolysis. In human white adipocytes, reductions in glutaminase activity promote aerobic glycolysis and mitochondrial oxidative capacity via increases in hypoxia-inducible factor 1α abundance, lactate levels and p38 mitogen-activated protein kinase signalling. Systemic glutaminase inhibition in male and female mice, or genetically in adipocytes of male mice, triggers the activation of thermogenic gene programs in inguinal adipocytes. Consequently, the knockout mice display higher energy expenditure and improved glucose tolerance compared to control littermates, even under high-fat diet conditions. Altogether, our findings highlight white adipocyte glutamine turnover as an important determinant of energy expenditure and metabolic health.

Defects in adipocyte lipolysis drive multiple aspects of cardiometabolic disease, but the transcriptional framework controlling this process has not been established. To address this, we performed a targeted perturbation screen in primary human adipocytes. Our analyses identified 37 transcriptional regulators of lipid mobilization, which we classified as (i) transcription factors, (ii) histone chaperones, and (iii) mRNA processing proteins. On the basis of its strong relationship with multiple readouts of lipolysis in patient samples, we performed mechanistic studies on one hit, ZNF189, which encodes the zinc finger protein 189. Using mass spectrometry and chromatin profiling techniques, we show that ZNF189 interacts with the tripartite motif family member TRIM28 and represses the transcription of an adipocyte-specific isoform of phosphodiesterase 1B (PDE1B2). The regulation of lipid mobilization by ZNF189 requires PDE1B2, and the overexpression of PDE1B2 is sufficient to attenuate hormone-stimulated lipolysis. Thus, our work identifies the ZNF189-PDE1B2 axis as a determinant of human adipocyte lipolysis and highlights a link between chromatin architecture and lipid mobilization.

A molecular clock network is crucial for daily physiology and maintaining organismal health. We examined the interactions and importance of intratissue clock networks in muscle tissue maintenance. In arrhythmic mice showing premature aging, we created a basic clock module involving a central and a peripheral (muscle) clock. Reconstituting the brain-muscle clock network is sufficient to preserve fundamental daily homeostatic functions and prevent premature muscle aging. However, achieving whole muscle physiology requires contributions from other peripheral clocks. Mechanistically, the muscle peripheral clock acts as a gatekeeper, selectively suppressing detrimental signals from the central clock while integrating important muscle homeostatic functions. Our research reveals the interplay between the central and peripheral clocks in daily muscle function and underscores the impact of eating patterns on these interactions.

A thorough understanding of the mechanisms controlling energy homeostasis is needed to prevent and treat metabolic morbidities. While the contribution of organs such as the liver, muscle, adipose tissue, and pancreas to the regulation of energy has received wide attention, less is known about the interplay with the nervous system. Here, we highlight the role of the nervous systems in regulating metabolism beyond the classic hypothalamic endocrine signaling models and discuss the contribution of circadian rhythms, higher brain regions, and sociodemographic variables in the energy equation. We infer that interdisciplinary approaches are key to conceptually advancing the current research frontier and devising innovative therapies to prevent and treat metabolic disease.

Physiology is regulated by interconnected cell and tissue circadian clocks. Disruption of the rhythms generated by the concerted activity of these clocks is associated with metabolic disease. Here we tested the interactions between clocks in two critical components of organismal metabolism, liver and skeletal muscle, by rescuing clock function either in each organ separately or in both organs simultaneously in otherwise clock-less mice. Experiments showed that individual clocks are partially sufficient for tissue glucose metabolism, yet the connections between both tissue clocks coupled to daily feeding rhythms support systemic glucose tolerance. This synergy relies in part on local transcriptional control of the glucose machinery, feeding-responsive signals such as insulin, and metabolic cycles that connect the muscle and liver. We posit that spatiotemporal mechanisms of muscle and liver play an essential role in the maintenance of systemic glucose homeostasis and that disrupting this diurnal coordination can contribute to metabolic disease.

In mammals, an integrated network of molecular oscillators drives daily rhythms of tissue-specific homeostatic processes. This circadian clock network is required for maintaining health and is compromised by disease and lifestyle choices, such as diet and exercise. However, critical properties of this systemic network, such as which tissues communicate to coordinate their respective programs of daily physiology, and the exact homeostatic processes requiring each communication pathway, remain undefined. To dissect daily inter-tissue communication, we have constructed in mice a minimal clock network comprising only two nodes: the peripheral epidermal clock and the central brain clock. By circadian transcriptomic and functional characterization of this isolated connection, we have identified a previously unknown gatekeeping function of the peripheral tissue clock with respect to systemic inputs. That is, the epidermal clock concurrently integrates and corrects brain signals to ensure timely execution of epidermal daily physiology. Specifying the integrative arm of the clock, we identify that timely cell cycle termination in the epidermal stem cell compartment is dependent upon incorporation of clock-driven signals originating from the brain. Unexpectedly, and in contrast, the epidermal clock corrects potentially disruptive feeding-related signals to ensure that DNA replication occurs at the optimum time of day. Together, we present a novel approach for cataloguing the systemic dependencies of a given tissue, and in turn identify an essential gate-keeping function of peripheral circadian clocks that guarantees tissue homeostasis.

Rhythmic locomotor activity is a commonly used readout of general circadian function in animals. For instance, measuring the activity of rodents in their home cages can provide information about circadian phase and period in response to genetic, pharmacological, and environmental manipulations. Herein, the use of infrared light sensors to measure circadian locomotor activity is described. Furthermore, we provide information about data handling, analysis and software use as well as points to consider when performing the experiment.

The gut microbiome influences cognition and behavior in mammals, yet its metabolic impact on the brain is only starting to be defined. Using metabolite profiling of antibiotics-treated mice, we reveal the microbiome as a key input controlling circadian metabolic cycles in the brain. Intra and inter-region analyses characterise the influence of the microbiome on the suprachiasmatic nucleus, containing the central clockwork, as well as the hippocampus and cortex, regions involved in learning and behavior.

Life on Earth anticipates recurring 24-hour environmental cycles via genetically encoded molecular clocks active in all mammalian organs. Communication between these clocks controls circadian homeostasis. Intertissue communication is mediated, in part, by temporal coordination of metabolism. Here, we characterize the extent to which clocks in different organs control systemic metabolic rhythms, an area that remains largely unexplored. We analyzed the metabolome of serum from mice with tissue-specific expression of the clock gene Bmal1. Having functional hepatic and muscle clocks can only drive a minority (13%) of systemic metabolic rhythms. Conversely, limiting Bmal1 expression to the central pacemaker in the brain restores rhythms to 57% of circulatory metabolites. Rhythmic feeding imposed on clockless mice resulted in a similar rescue, indicating that the central clock mainly regulates metabolic rhythms via behavior. These findings explicate the circadian communication between tissues and highlight the importance of the central clock in governing those signals.

Objective: The circadian clock aligns physiology with the 24-hour rotation of Earth. Light and food are the main environmental cues (zeitgebers) regulating circadian rhythms in mammals. Yet, little is known about the interaction between specific dietary components and light in coordinating circadian homeostasis. Herein, we focused on the role of essential amino acids. Methods: Mice were fed diets depleted of specific essential amino acids and their behavioral rhythms were monitored and tryptophan was selected for downstream analyses. The role of tryptophan metabolism in modulating circadian homeostasis was studied using isotope tracing as well as transcriptomic- and metabolomic- analyses. Results: Dietary tryptophan depletion alters behavioral rhythms in mice. Furthermore, tryptophan metabolism was shown to be regulated in a time- and light- dependent manner. A multi-omics approach and combinatory diet/light interventions demonstrated that tryptophan metabolism modulates temporal regulation of metabolism and transcription programs by buffering photic cues. Specifically, tryptophan metabolites regulate central circadian functions of the suprachiasmatic nucleus and the core clock machinery in the liver. Conclusions: Tryptophan metabolism is a modulator of circadian homeostasis by integrating environmental cues. Our findings propose tryptophan metabolism as a potential point for pharmacologic intervention to modulate phenotypes associated with disrupted circadian rhythms.

Expressed throughout the body, the circadian clock system achieves daily metabolic homeostasis at every level of physiology, with clock disruption associated with metabolic disease ( 1 , 2 ). Molecular clocks present in the brain, liver, adipose, pancreas and skeletal muscle each contribute to glucose homeostasis ( 3 ). However, it is unclear; 1) which organ clocks provide the most essential contributions, and 2) if these contributions depend on inter-organ communication. We recently showed that the liver clock alone is insufficient for most aspects of daily liver glucose handling and requires connections with other clocks ( 4 ). Considering the pathways that link glucose metabolism between liver and skeletal muscle, we sought to test whether a clock connection along this axis is important. Using our previous published methodology for tissue-specific rescue of Bmal1 in vivo ( 4 , 5 ), we now show that in the absence of feeding-fasting cycles, liver and muscle clocks are not sufficient for systemic glucose metabolism, nor do they form a functional connection influencing local glucose handling or daily transcriptional rhythms in each tissue. However, the introduction of a daily feeding-fasting rhythm enables a synergistic state between liver and muscle clocks that leads to restoration of systemic glucose tolerance. These findings reveal limited autonomous capabilities of liver and muscle clocks and highlight the need for inter-organ clock communication for glucose homeostasis which involves at least two peripheral metabolic organs.

The inner workings of the clock system rely on communicating signals between distal tissues to maintain daily metabolism.