Circadian regulation of proteostasis, a key determinant of muscle health, remains poorly understood. Here, we identified DNAJB6, an Hsp40 (DnaJ) co-chaperone, as a substrate of the circadian E3 ligase FBXL21. FBXL21 mediated the ubiquitination-dependent proteasomal degradation of both DNAJB6 and its client proteins including Desmin; causative mutations of DNAJB6 in myopathies, however, rendered resistance to FBXL21-directed degradation. Fbxl21 KO C2C12 cells displayed aberrant accumulation of Desmin, and showed aggravated cytoplasmic accumulation of TDP-43, another DNAJB6 client protein, in heat shock response. Under timed exercise as a physiological stressor, WT mice displayed robust diurnal rhythms in the levels of stress granule markers (G3BP1 and FUS) and TDP-43 as a function of exercise timing. In contrast, the Fbxl21 hypomorph Psttm mutant mice showed elevated expression of these proteins without exercise, which was exacerbated under exercise-induced stress conditions; importantly, these abnormalities were rescued by skeletal muscle-specific FBXL21 expression. Our study elucidates a novel diurnal regulatory mechanism of skeletal muscle proteostasis via FBXL21 as a chaperone-linked E3 ligase, highlighting the FBXL21-DNAJB6 axis as a potential therapeutic target for myopathies.

Macrophages orchestrate tissue remodeling, inflammation, and metabolic dysfunction in obesity, but the role of macrophage-intrinsic extracellular proteolysis in immunometabolic regulation remains unclear. Matrix metalloproteinase-14 (MMP14), a membrane-bound protease, is strongly induced during monocyte-to-macrophage differentiation and further elevated in adipose tissue macrophages from high-fat diet (HFD)-fed mice. Pharmacological inhibition or myeloid-specific deletion of Mmp14 impaired macrophage differentiation, proliferation, migration, phagocytosis, and inflammatory activation in response to obesity-associated adipose tissue signals. Mechanistically, MMP14 promoted inflammatory programming by increasing endotrophin generation and enhancing TLR4-NFκB signaling. MMP14 also reprogrammed macrophage lipid metabolism by suppressing lipolysis and promoting lipid accumulation, altering metabolic communication with neighboring cells. In vivo, myeloid-specific Mmp14 deletion protected mice from HFD-induced insulin resistance, dyslipidemia, hepatic steatosis, adipose inflammation, and fibrosis. These findings identify macrophage MMP14 as a key mediator linking extracellular matrix remodeling with inflammatory and metabolic dysfunction in obesity.

Physiological processes such as the sleep-wake cycle, metabolism, hormone secretion, neurotransmitter release, sensory capabilities, and a variety of behaviors, including sleep, are controlled by a circadian rhythm adapted to 24-hour day-night periodicity. Disruption of circadian rhythm may lead to the risks of numerous diseases, including cancers. Several epidemiological and clinical data reveal a connection between the disruption of circadian rhythms and cancer. On the contrary, oncogenic processes may suppress the homeostatic balance imposed by the circadian clock. The integration of circadian biology into cancer research offers new options for making cancer treatment more effective, and the pharmacological modulation of core clock genes is a new approach in cancer therapy. This review highlights the role of the circadian clock in tumorigenesis, how clock disruption alters the tumor microenvironment, and discusses how pharmacological modulation of circadian clock genes can lead to new therapeutic options.

Inactivation of telomerase (TERT) in adipocyte progenitor cells (APC) expedites telomere attrition, and the onset of diabetes in mice fed high-fat diet (HFD), which promotes APC over-proliferation and replicative senescence. Here, we show that time-restricted feeding or caloric restriction in the postnatal development of mice subsequently subjected to HFD prevents telomere attrition but not glucose intolerance. This metabolic effect of dietary intervention was not observed for mice with TERT KO in endothelial or myeloid cells. To characterize the telomere-independent effects of TERT in the APC lineage, we analyzed mice with TERT knockout in mature adipocytes (AD-TERT-KO), which do not proliferate and avoid telomere attrition. Analysis of adipocytes from AD-TERT-KO mice indicated reliance on glycolysis and decreased mitochondrial oxidative metabolism. We show that AD-TERT-KO mice have reduced cold tolerance and metabolism abnormality indicating a defect in adaptive thermogenesis, characteristic of aging. Conversely, ectopic TERT expression in brown adipocytes-induced mitochondrial oxidation and thermogenic gene expression. We conclude that TERT plays an important non-canonical function in the mitochondria of adipocytes.

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths. Most patients present at advanced stages, and the effectiveness of tyrosine kinase inhibitors (TKIs) and immune checkpoint inhibitors is constrained by limited patient response. A subset of HCC shows elevated expression of the promoter 2 (“P2”)-driven hepatocyte nuclear factor 4 alpha (HNF4α) isoform, which directly transcriptionally represses the circadian brain and muscle ARNT-like protein 1 (BMAL1) transcription factor. This subtype of HCC is robustly inhibited by the plant-based flavonoid nobiletin (NOB), a circadian-fortifying compound. Using patient-matched human HCC and serum, we show that BMAL1-deficient HCC shows exaggerated carnitine palmitoyl transferase expression and related metabolite abundance and that P2-HNF4α regulates the carnitine palmitoyl transferase I gene. Finally, using different preclinical models, we show that the anti-tumor activity of TKIs, when they are co-administered with NOB, is maximal. Our results suggest that chronotherapy and combination therapy might provide improved clinical outcomes for individuals with BMAL1-deficient HCC.

Four-week dawn-to-dusk dry fasting (DDDF) was previously shown to have a potent anti-inflammatory effect and induce an anti-tumorigenic proteome in the serum and peripheral blood mononuclear cells in subjects without cancer. The study goal was to determine if serum obtained from these subjects without cancer who underwent 4-week DDDF has an anti-tumorigenic effect. HepG2 cells were treated with serum collected from four individuals with metabolic syndrome and metabolic dysfunction-associated steatotic liver disease (MASLD) and four healthy individuals who performed 4-week DDDF. The objective was to assess cell proliferation/viability in HepG2 cells treated with non-fasted and dry-fasted serum and determine proteomic changes in human serum. We comparatively performed 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) cell proliferation assay and untargeted proteomic analysis using nano ultra-high performance liquid chromatography coupled with tandem mass spectrometry. Serum collected from 3 out of 4 subjects with metabolic syndrome and MASLD at the end of 4-week DDDF (dry-fasted serum/V2) significantly reduced proliferation/viability in HepG2 cells compared with the serum collected before 4-week DDDF (non-fasted serum/V1). A similar reduction effect on cell proliferation was not observed when HepG2 cells were treated with dry-fasted serum collected from healthy subjects. In addition to the in vitro changes observed, the following circulating gene protein products (GP) demonstrated significant increases or decreases in subjects with metabolic syndrome and MASLD after a 4-week DDDF regimen, compared with their GP levels before the 4-week DDDF: CD248 molecule (mean log2 fold = 8.124, P = 0.001), dipeptidyl peptidase 4 (mean log2 fold = 0.937, P = 0.027), lymphatic vessel endothelial hyaluronan receptor 1 (mean log2 fold = 1.054, P = 0.029), LDL receptor related protein 1 (mean log2 fold = 1.401, P = 0.031), and beta-2-microglobulin (mean log2 fold= -0.977, P = 0.033) at the end of 4-week DDDF compared with the GP levels before 4-week DDDF. This study demonstrated that dry-fasted serum collected from subjects with metabolic syndrome and MASLD decreased HepG2 cell proliferation in vitro and showed that proteomic changes occurred in vivo. These findings suggest that DDDF may be an effective intervention for inducing proteomic responses that could assist in the prevention and adjunct treatment of cancers associated with metabolic syndrome.

Circadian rhythms are internal biological rhythms driving temporal tissue-specific, metabolic programs. Loss of the circadian transcription factor BMAL1 in the paraventricular nucleus (PVN) of the hypothalamus reveals its importance in metabolic rhythms, but its functions in individual PVN cells are poorly understood. Here, loss of BMAL1 in the PVN results in arrhythmicity of processes controlling energy balance and alters peripheral diurnal gene expression. BMAL1 chromatin immunoprecipitation sequencing (ChIP-seq) and single-nucleus RNA sequencing (snRNA-seq) reveal its temporal regulation of target genes, including oxytocin (OXT), and restoring circulating OXT peaks in BMAL1-PVN knockout (KO) mice rescues absent activity rhythms. While glutamatergic neurons undergo day/night changes in expression of genes involved in cell morphogenesis, astrocytes and oligodendrocytes show gene expression changes in cytoskeletal organization and oxidative phosphorylation. Collectively, our findings show diurnal gene regulation in neuronal and non-neuronal PVN cells and that BMAL1 contributes to diurnal OXT secretion, which is important for systemic diurnal rhythms.

In recent decades, obesity has become a worldwide epidemic. As a result, the importance of adipose tissue (AT) as a metabolically active storage depot for lipids and a key mediator of body-wide metabolism and energy balance has been increasingly recognized. Emerging from the studies of AT in metabolic disease is a recognition of the importance of the adipocyte progenitor cell (APC) population of AT being the gatekeeper of adipocyte function. APCs have the capability to self-renew and undergo adipogenesis to propagate new adipocytes capable of lipid storage, which is important for maintaining a healthy fat pad, devoid of dysfunctional lipid droplet hypertrophy, inflammation, and fibrosis, which is linked to metabolic diseases, including type 2 diabetes. Like other dividing cells, APCs are at risk for undergoing cell senescence, a state of irreversible cell proliferation arrest that occurs under a variety of stress conditions, including DNA damage and telomere attrition. APC proliferation is controlled by a variety of factors, including paracrine and endocrine factors, quality and timing of energy intake, and the circadian clock system. Therefore, alteration in any of the underlying signaling pathways resulting in excessive proliferation of APCs can lead to premature APC senescence. Better understanding of APCs senescence mechanisms will lead to new interventions extending metabolic health.

It has remained unclear how aging of endothelial cells (EC) contributes to pathophysiology of individual organs. Cell senescence results in part from inactivation of telomerase (TERT). Here, we analyzed mice with Tert knockout specifically in EC. Tert loss in EC induced transcriptional changes indicative of senescence and tissue hypoxia in EC and in other cells. We demonstrate that EC-Tert-KO mice have leaky blood vessels. The blood-brain barrier of EC-Tert-KO mice is compromised, and their cognitive function is impaired. EC-Tert-KO mice display reduced muscle endurance and decreased expression of enzymes responsible for oxidative metabolism. Our data indicate that Tert-KO EC have reduced mitochondrial content and function, which results in increased dependence on glycolysis. Consistent with this, EC-Tert-KO mice have metabolism changes indicative of increased glucose utilization. In EC-Tert-KO mice, expedited telomere attrition is observed for EC of adipose tissue (AT), while brain and skeletal muscle EC have normal telomere length but still display features of senescence. Our data indicate that the loss of Tert causes EC senescence in part through a telomere length-independent mechanism undermining mitochondrial function. We conclude that EC-Tert-KO mice is a model of expedited vascular senescence recapitulating the hallmarks aging, which can be useful for developing revitalization therapies.

BackgroundAcute myeloid leukemia (AML) with an internal tandem duplication in the fms-like tyrosine kinase receptor 3 gene (FLT3-ITD) is associated with poor survival, and few studies have examined the impact of modifiable behaviors, such as nutrient quality and timing, in this subset of acute leukemia.MethodsThe influence of diet composition (low-sucrose and/or low-fat diets) and timing of diet were tested in tandem with anthracycline treatment in orthotopic xenograft mouse models. A pilot clinical study to test receptivity of pediatric leukemia patients to macronutrient matched foods was conducted. A role for the circadian protein, BMAL1 (brain and muscle ARNT-like 1), in effects of diet timing was studied by overexpression in FLT3-ITD-bearing AML cells.ResultsReduced tumor burden in FLT3-ITD AML-bearing mice was observed with interventions utilizing low-sucrose and/or low-fat diets, or time-restricted feeding (TRF) compared to mice fed normal chow ad libitum. In a tasting study, macronutrient matched low-sucrose and low-fat meals were offered to pediatric acute leukemia patients who largely reported liking the meals. Expression of the circadian protein, BMAL1, was heightened with TRF and the low-sucrose diet. BMAL1 overexpression and treatment with a pharmacological inducer of BMAL1 was cytotoxic to FLT3-ITD AML cells.ConclusionsMouse models for FLT3-ITD AML show that diet composition and timing slows progression of FLT3-ITD AML growth in vivo, potentially mediated by BMAL1. These interventions to enhance therapy efficacy show preliminary feasibility, as pediatric leukemia patients responded favorable to preparation of macronutrient matched meals. Low-fat and low-sucrose diets (positively received by pediatric patients) enhanced anthracycline efficacy compared to mice fed normal chow. Time-restricted feeding slows tumor progression compared to mice fed ad libitum and correlates with increased BMAL1 expression.image

the study results can be extrapolated to the eating habits and patterns of humans, and the deleterious effects that timing can have on metabolism and energy balance. Circadian disruption is associated with metabolic disease, including obesity and diabetes. 6 In this context, time-restricted eating can be considered a form of circadian medicine, wherein timed application of intervention (in this case energy intake) can be used to target and exploit the circadian clock. 7 The quote by Hippocrates, “Let food by thy medicine and medicine by thy food,” is often cited to emphasize the powerful impact of nutrition on health. Increasingly understood is the extent to which the timing of energy intake may be important for delaying metabolic disease and its progression. This study underscores that even the timing of snacks with sufficient calories to alter insulin secretion and blood glucose may be important for maintaining energy balance in the long term.

DATA REPORT article Front. Cell Dev. Biol., 07 December 2023Sec. Molecular and Cellular Pathology Volume 11 - 2023 | https://doi.org/10.3389/fcell.2023.1295072

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A growing number of studies reveal that disruption of the endogenous, circadian (i.e., 24-hour) clock increases the risk for acquiring several diseases, including specific cancers. Significantly more work needs to be done to understand the molecular substrates involved in the mechanistic links between circadian clock disruption and cancer initiation and progression. Of particular complexity remains the contribution of the circadian clock in individual cells during the process of transformation (cancer initiation) versus its function in tumor-surrounding stroma and how this affects the process of tumor progression or metastasis. This chapter reviews some of the basic mechanisms understood to link circadian disruption and cancer at the level of gene expression and metabolism, while highlighting human studies supporting the association between circadian disruption and cancer incidence. In light of what is currently known, tremendous opportunites exist to use circadian approaches for future prevention and treatment strategies in the context of organ-specific cancer.

The circadian clock plays a prominent role in neurons during development and throughout aging. This review covers topics pertinent to the role of 24-h rhythms in neuronal development and function, and their tendency to decline with aging. Pharmacological or behavioral modification that augment the function of our internal clock may be central to decline of cognitive disease and to future chronotherapy for aging-related diseases of the central nervous system.

Hepatocyte Nuclear Factor 4α (HNF4α), a master regulator of hepatocyte differentiation, is regulated by two promoters (P1 and P2) which drive the expression of different isoforms. P1-HNF4α is the major isoform in the adult liver while P2-HNF4α is thought to be expressed only in fetal liver and liver cancer. Here, we show that P2-HNF4α is indeed expressed in the normal adult liver at Zeitgeber time (ZT)9 and ZT21. Using exon swap mice that express only P2-HNF4α we show that this isoform orchestrates a distinct transcriptome and metabolome via unique chromatin and protein-protein interactions, including with different clock proteins at different times of the day leading to subtle differences in circadian gene regulation. Furthermore, deletion of the Clock gene alters the circadian oscillation of P2- (but not P1-)HNF4α RNA, revealing a complex feedback loop between the HNF4α isoforms and the hepatic clock. Finally, we demonstrate that while P1-HNF4α drives gluconeogenesis, P2-HNF4α drives ketogenesis and is required for elevated levels of ketone bodies in female mice. Taken together, we propose that the highly conserved two-promoter structure of the Hnf4a gene is an evolutionarily conserved mechanism to maintain the balance between gluconeogenesis and ketogenesis in the liver in a circadian fashion.

There is growing evidence that disruption of our 24-h clock increases our risk for acquiring several diseases and disorders. One of these diseases is cancer. While the mechanistic links between circadian clock disruption and cancer initiation or progression are an active area of study, significantly more work needs to be done to understand the molecular substrates involved. Of particular complexity remains the functions of the clock in individual cells during the process of transformation (cancer initiation) versus the functions of the clock in tumour-surrounding stroma in the process of tumour progression or metastasis. Indeed, the nexus of cellular circadian dynamics, metabolism and carcinogenesis is drawing more attention, and many new studies are now highlighting the critical role of circadian rhythms and clock proteins in cancer prevention. In this brief review, we cover some of the basic mechanisms reported to link circadian disruption and cancer at the level of gene expression and metabolism. We also review some of the human studies addressing circadian disruption and cancer incidence as well as some controlled laboratory studies connecting the two in pre-clinical models. Finally, we discuss the tremendous opportunity to use circadian approaches for future prevention and treatment in the context of cancer in specific organs.

White adipose tissue (WAT) is a metabolic organ with flexibility to retract and expand based on energy storage and utilization needs, processes that are driven via the coordination of different cells within adipose tissue. WAT is comprised of mature adipocytes (MA) and cells of the stromal vascular cell fraction (SVF), which include adipose progenitor cells (APCs), adipose endothelial cells (AEC) and infiltrating immune cells. APCs have the ability to proliferate and undergo adipogenesis to form MA, the main constituents of WAT being predominantly composed of white, triglyceride-storing adipocytes with unilocular lipid droplets. While adiposity and adipose tissue health are controlled by diet and aging, the endogenous circadian (24-h) biological clock of the body is highly active in adipose tissue, from adipocyte progenitor cells to mature adipocytes, and may play a unique role in adipose tissue health and function. To some extent, 24-h rhythms in adipose tissue rely on rhythmic energy intake, but individual circadian clock proteins are also thought to be important for healthy fat. Here we discuss how and why the clock might be so important in this metabolic depot, and how temporal and qualitative aspects of energy intake play important roles in maintaining healthy fat throughout aging.