Objective

Circadian rhythms of metabolic, hormonal, and behavioral fluctuations and their alterations can impact health. An important gap in knowledge in the field is whether the time of the day of exercise and the age of onset of exercise exert distinct effects at the level of whole-body adipose tissue and body composition. The goal of the present study was to determine how exercise at different times of the day during adolescence impacts the adipose tissue transcriptome and content in a rodent model.

Methods

Rats were subjected to one of four conditions during their adolescence: early active phase control or exercise (EAC or EAE; ZT13), and late active phase control or exercise (LAC or LAE; ZT23). The effects of exercise timing were assessed at the level of subcutaneous and visceral adipose tissue transcriptome, body composition, hypothalamic expression of orexigenic and anorexigenic genes, blood serum markers and 24-hour core body temperature patterns.

Results

We found that late active phase exercise (ZT23) greatly upregulated pathways of lipid synthesis, glycolysis and NADH shuttles in LAE rats, compared to LAC or EAE. Conversely, LAE rats showed notably lower content of adipose tissue. In addition, LAE rats showed signs of impaired FGF21-adiponectin axis compared to other groups.

Conclusions

Finally, LAE rats showed higher post-exercise core body temperature compared to other groups. Our results thus indicate that our exercise protocol induced an unusual effect characterized by enhanced lipid synthesis but reduced adipose tissue content in late active phase but not early active phase exercise during adolescence.

Objective

Obesity-associated metabolic dysfunction is a major public health concern worldwide. Endothelial dysfunction is a hallmark of metabolic dysfunction, and endothelial cells affect metabolic functions. Because autophagy-related gene 7 (ATG7) is involved in various cellular physiology, we investigated the roles of endothelial cell-ATG7 (EC-ATG7) on high-fat diet-induced obesity and its related metabolic dysfunction.

Methods

We generated an endothelial-specific Atg7 knock-out mouse by breeding Atg7^flox/flox mouse with the Chd5-Cre mouse, and investigated the metabolic phenotypes associated with high-fat diet (HFD)-induced obesity. Body weight, food intake, glucose tolerance, insulin sensitivity, and liver fat accumulation were measured in endothelial Atg7 deficient (Atg7^ΔEnd) and control mice (Atg7^f/f). Adipose tissue inflammation was assessed by measuring the expression of pro-inflammatory genes. Furthermore, we performed indirect calorimetry and examined the insulin signaling pathway molecules.

Results

We found that deletion of EC-Atg7 ameliorated HFD-induced weight gain, fatty liver, and adipocyte hypertrophy and inflammatory response in adipose tissue, and improved insulin sensitivity without changing glucose tolerance. These metabolic effects seem to be due to the reduced food intake because there were no differences in energy expenditure, energy excretion to feces, and physical activity. Interestingly, the deletion of EC-Atg7 protected from HFD-induced vascular rarefaction, and the knock-down of Atg7 in endothelial cells protected from fatty acid-induced cell death.

Conclusions

Our results suggest that EC-Atg7 deletion ameliorates HFD-induced obesity and its related metabolic dysfunction, such as insulin resistance and fatty liver by attenuating appetite and vascular rarefaction. The EC-Atg7 deletion may protect the endothelial cells from lipotoxicity and impaired angiogenesis, which preserves the endothelial function in metabolic tissues. These findings may have implications for developing new therapeutic strategies for preventing and treating obesity and its associated health risks.

Objective

Increased fructose consumption contributes to type 2 diabetes (T2D) and metabolic dysfunction-associated steatotic liver disease (MASLD), but the mechanisms are ill-defined. Gut nutrient sensing involves enterohormones like Glucagon-like peptide (Glp)2, which regulates the absorptive capacity of luminal nutrients. While glucose is the primary dietary energy source absorbed in the gut, it is unknown whether excess fructose alters gut glucose sensing to impair blood glucose regulation and liver homeostasis.

Methods

Mice were fed diets where carbohydrates were either entirely glucose (70 %Kcal) or glucose partially replaced with fructose (8.5 %Kcal). Glp2 receptor (Glp2r) was inhibited with Glp2 (3-33) injections. Glucose tolerance, insulin sensitivity, and gut glucose absorption were concomitantly assessed, and enteric sugar transporters and absorptive surface were quantified by RT-qPCR and histological analysis, respectively.

Results

High fructose feeding led to impairment of blood glucose disposal, ectopic fat accumulation in the liver, and hepatic (but not muscle or adipose tissue) insulin resistance independent of changes in fat mass. This was accompanied by increased gut glucose absorption, which preceded glucose intolerance and liver steatosis. Fructose upregulated glucose transporters and enlarged the gut surface, but these effects were prevented by Glp2r inhibition. Blocking Glp2r prevented fructose-induced impairments in glucose disposal and hepatic lipid handling.

Conclusion

Excess fructose impairs blood glucose and liver homeostasis by rewiring gut glucose sensing and exacerbating gut glucose absorption. Our findings are positioned to inform novel early diagnostic tools and treatments tailored to counter high fructose-induced metabolic derangements predisposing to T2D and MASLD.

Objective

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common cause of chronic liver disease, especially in patients with severe obesity. However, current mouse models for MASLD do not reflect the polygenetic background nor the metabolic changes in this population. Therefore, we investigated two novel mouse models of MASLD with a polygenetic background for the metabolic syndrome.

Methods

TALLYHO/JngJ mice and NONcNZO10/LtJ mice were fed a high-fat- high-carbohydrate (HF-HC) diet with a surplus of cholesterol diet. A second group of TH mice was additional treated with empagliflozin.

Results

After sixteen weeks of feeding, both strains developed metabolic syndrome with severe obesity and histological manifestation of steatohepatitis, which was associated with significantly increased intrahepatic CD8⁺cells, CD4⁺cells and Tregs, contributing to a significant increase in pro-inflammatory and pro-fibrotic gene activation as well as ER stress and oxidative stress. In comparison with the human transcriptomic signature, we could demonstrate a good metabolic similarity, especially for the TH mouse model. Furthermore, TH mice also developed signs of kidney injury as an extrahepatic comorbidity of MASLD. Additional treatment with empagliflozin in TH mice attenuates hepatic steatosis and improves histological manifestation of MASH.

Conclusions

Overall, we have developed two promising new mouse models that are suitable for preclinical studies of MASLD as they recapitulate most of the key features of MASLD.

Objective

Many cancer cells depend on exogenous methionine for proliferation, whereas non-tumorigenic cells can divide in media supplemented with the metabolic precursor homocysteine. This phenomenon is known as methionine dependence of cancer or methionine addiction. The underlying mechanisms driving this cancer-specific metabolic addiction are poorly understood. Here we find that methionine dependence is associated with severe dysregulation of pre-mRNA splicing.

Methods

We used triple-negative breast cancer cells and their methionine-independent derivatives R8 to compare RNA expression profiles in methionine and homocysteine growth media. The data set was also analyzed for alternative splicing.

Results

When tumorigenic cells were cultured in homocysteine medium, cancer cells failed to efficiently methylate the spliceosomal snRNP component SmD1, which resulted in reduced binding to the Survival-of-Motor-Neuron protein SMN leading to aberrant splicing. These effects were specific for cancer cells as neither Sm protein methylation nor splicing fidelity was affected when non-tumorigenic cells were cultured in homocysteine medium. Sm protein methylation is catalyzed by Protein Arginine Methyl Transferase 5 (Prmt5). Reducing methionine concentrations in the culture medium sensitized cancer cells to Prmt5 inhibition supporting a mechanistic link between methionine dependence of cancer and splicing.

Conclusions

Our results link nutritional demands to splicing changes and thereby provide a link between the cancer-specific metabolic phenomenon, described as methionine addiction over 40 years ago, with a defined cellular pathway that contributes to cancer cell proliferation.

Besides its thermogenic capacity, brown adipose tissue (BAT) performs important secretory functions that regulate metabolism. However, the BAT microenvironment and factors involved in BAT homeostasis and adaptation to cold remain poorly characterized. We therefore aimed to study brown adipocyte-derived secreted factors that may be involved in adipocyte function and/or may orchestrate intercellular communications. For this, mRNA levels in mature adipocytes from mouse adipose depots were assessed using RNA sequencing upon chronic cold acclimation, and bioinformatic analysis was used to identify secreted factors. Among 858 cold-sensitive transcripts in BAT adipocytes were 210 secreted factor-encoding genes, and Cxcl12 was the top brown adipocyte-enriched cytokine. Cxcl12 mRNA expression analysis by RT-qPCR and fluorescence in situ hybridization specified Cxcl12 distribution in various cell types, and indicated its enrichment in cold-acclimated brown adipocytes. We found that CXCL12 secretion from BAT was increased after chronic cold, yet its level in plasma remained unchanged, suggesting a local/paracrine function. Cxcl12 knockdown in mature brown adipocytes impaired thermogenesis, as assessed by norepinephrine (NE)-induced glycerol release and mitochondrial respiration. However, knockdown of Cxcl12 did not impact β-adrenergic signaling, suggesting that CXCL12 regulates adipocyte function downstream of the β-adrenergic pathway. Moreover, we provide evidence for CXCL12 to exert intercellular cross-talk via its capacity to promote macrophage chemotaxis and neurite outgrowth. Collectively, our results indicate that CXCL12 is a brown adipocyte-enriched, cold-induced secreted factor involved in adipocyte function and the BAT microenvironment communication network.

Objective

The capacity of mature adipocytes to de-differentiate into fibroblast-like cells has been demonstrated in vitro and a few, rather specific in vivo conditions. A detailed comparison between de-differentiated fat (DFAT) cells and adipose stem and progenitor cells (ASPCs) from different adipose depots is yet to be conducted. Moreover, whether de-differentiation of mature adipocytes from classical subcutaneous and visceral depots occurs under physiological conditions remains unknown.

Methods

Here, we used in vitro "ceiling culture", single cell/nucleus RNA sequencing, epigenetic anaysis and genetic lineage tracing to address these unknowns.

Results

We show that in vitro-derived DFAT cells have lower adipogenic potential and distinct cellular composition compared to ASPCs. In addition, DFAT cells derived from adipocytes of inguinal origin have dramatically higher adipogenic potential than DFAT cells of the epididymal origin, due in part to enhanced NF-KB signaling in the former. We also show that high-fat diet (HFD) feeding enhances DFAT cell colony formation and re-differentiation into adipocytes, while switching from HFD to chow diet (CD) only reverses their re-differentiation. Moreover, HFD deposits epigenetic changes in DFAT cells and ASPCs that are not reversed after returning to CD. Finally, combining genetic lineage tracing and single cell/nucleus RNA sequencing, we demonstrate the existence of DFAT cells in inguinal and epididymal adipose depots in vivo, with transcriptomes resembling late-stage ASPCs.

Conclusions

These data uncover the cell type- and depot-specific properties of DFAT cells, as well as their plasticity in response to dietary intervention. This knowledge may shed light on their role in life style change-induced weight loss and regain.

Objectives

The rapid growth that occurs during Drosophila larval development requires a dramatic rewiring of central carbon metabolism to support biosynthesis. Larvae achieve this metabolic state, in part, by coordinately up-regulating the expression of genes involved in carbohydrate metabolism. The resulting metabolic program exhibits hallmark characteristics of aerobic glycolysis and establishes a physiological state that supports growth. To date, the only factor known to activate the larval glycolytic program is the Drosophila Estrogen-Related Receptor (dERR). However, dERR is dynamically regulated during the onset of this metabolic switch, indicating that other factors must be involved. Here we examine the possibility that the Drosophila ortholog of Hypoxia inducible factor 1α (Hif1α) is also required to activate the larval glycolytic program.

Methods

CRISPR/Cas9 was used to generate new loss-of-function alleles in the Drosophila gene similar (sima), which encodes the sole fly ortholog of Hif1α. The resulting mutant strains were analyzed using a combination of metabolomics and RNAseq for defects in carbohydrate metabolism.

Results

Our studies reveal that sima mutants fail to activate aerobic glycolysis and die during larval development with metabolic phenotypes that mimic those displayed by dERR mutants. Moreover, we demonstrate that dERR and Sima/Hif1α protein accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance of the other protein.

Conclusions

These findings demonstrate that Sima/HIF1α is required during embryogenesis to coordinately up-regulate carbohydrate metabolism in preparation for larval growth. Notably, our study also reveals that the Sima/HIF1α-dependent gene expression program shares considerable overlap with that observed in dERR mutant, suggesting that Sima/HIF1α and dERR cooperatively regulate embryonic and larval glycolytic gene expression.

Objective

Cardiac function declines with age, impairing exercise tolerance and negatively impacting healthy aging. However, mechanisms driving age-related declines in cardiac function are not fully understood.

Methods

We examined mechanisms underlying age-related cardiac dysfunction using 3- and 24-month-old wild-type mice fed ad libitum or 24-month-old wild-type mice subjected to 70% calorie restriction (CR) starting at 2-month-old. In addition, cardiac aging phenotypes and mitochondrial biogenesis were also analyzed in 25-month-old cardiac-specific Hint1 knockout mice, 24-month-old CAG-Caren Tg mice, and 24-month-old wild-type mice injected with AAV6-Caren.

Results

We observed inactivation of mitochondrial biogenesis in hearts of aged mice. We also showed that activity of the BAF chromatin remodeling complex is repressed by HINT1, whose expression in heart increases with age, leading to decreased transcription of Tfam, which promotes mitochondrial biogenesis. Interestingly, CR not only suppressed age-related declines in cardiac function and mitochondrial biogenesis but blocked concomitant increases in cardiac HINT1 protein levels and maintained Tfam transcription. Furthermore, expression of the lncRNA Caren, which inhibits Hint1 mRNA translation, decreased with age in heart, and CR suppressed this effect. Finally, decreased HINT1 expression due to Caren overexpression antagonized age-related declines in mitochondrial biogenesis, ameliorating age-related cardiac dysfunction, exercise intolerance, and exercise-induced cardiac damage and subsequent death of mice.

Conclusion

Our findings suggest that mitochondrial biogenesis in cardiomyocytes decreases with age and could underlie cardiac dysfunction, and that the Caren-HINT1-mitochondrial biogenesis axis may constitute a mechanism linking CR to resistance to cardiac aging. We also show that ameliorating declines in mitochondrial biogenesis in cardiomyocytes could counteract age-related declines in cardiac function, and that this strategy may improve exercise tolerance and extend so-called "healthy life span".

Objective

This study aims to investigate how reproductive experience (RE) alters thermal preference and thermoregulation in female mice, with a focus on estrogen receptor alpha (ERα)-expressing neurons in the preoptic area (POA).

Methods

Thermal preference and body temperature were measured in female mice with and without RE, and virgin female mice with selective deletion of ERα from the POA (ERα^POA-KO). The number and activity of ERα-expressing POA neurons (ERα^POA) were assessed using immunohistochemistry and in vitro electrophysiology in response to temperature changes and ERα agonist.

Results

We showed that female mice prefer a cooler environment starting from late pregnancy and persisting long term postpartum. Female mice with RE (>4 weeks post-weaning) displayed lower body temperature and a lower thermal preferred temperature, and lost preference for warm environments (30 °C) but preserved avoidance of cold environments (15 °C). This was associated with a significant decrease in the number of ERα^POA neurons. Importantly, virgin female ERα^POA-KO mice displayed lower thermal preferred temperature and impaired warm preference, mimicking RE mice. We further found that distinct ERα^POA subpopulations can be regulated by temperature changes with or without presynaptic blockers, and by ERα agonist. More importantly, RE decreased the number of warm-activated ERα^POA neurons and reduced the excitatory effects of warmth and estrogen-ERα signaling, while cold-activated ERα^POA neurons were slightly enhanced in female mice with RE.

Conclusion

Our results support that the thermosensing ability and estrogenic effects in ERα^POA neurons are regulated by reproductive experience, altering thermal preference.

Objective

There is growing evidence that sleep deprivation promotes cancer progression. In addition, colon cancer patients often experience sleep deprivation due to factors such as cancer pain and side effects of treatment. The occurrence of liver metastases is an important factor in the mortality of colon cancer patients. However, the relationship between sleep deprivation and liver metastases from colon cancer has not been elucidated.

Methods

A sleep deprivation liver metastasis model was constructed to evaluate the effect of sleep deprivation on liver metastasis of colon cancer. Subsequently, mice feces were collected for untargeted metabolomics to screen and identify the key mediator, Kynurenic acid (KynA). Furthermore, HILPDA was screened by transcriptomics, and its potential mechanism was explored through ChIP, co-IP, ubiquitination experiments, phenotyping experiments, etc.

Results

Sleep deprivation promotes liver metastases in colon cancer. Functionally, sleep deprivation aggravates lipid accumulation and decreases the production of the microbiota metabolite KynA. In contrast, KynA inhibited colon cancer progression in vitro. In vivo, KynA supplementation reversed the promoting effects of sleep deprivation on liver metastases from colon cancer. Mechanistically, KynA downregulates the expression of P4HA2 to promote the ubiquitination and degradation of HIF-1α, which leads to a decrease in the transcription of HILPDA, and ultimately leads to an increase in lipolysis of colon cancer cells.

Conclusions

Our findings reveal that sleep deprivation impairs intracellular lipolysis by KynA, leading to lipid droplets accumulation in colon cancer cells. This process ultimately promotes colon cancer liver metastasis. This suggests a promising strategy for colon cancer treatment.