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Nature Metabolism Dec 2022Childhood obesity is a serious public health crisis and a critical factor that determines future obesity prevalence. Signals affecting adipocyte development in early...
Childhood obesity is a serious public health crisis and a critical factor that determines future obesity prevalence. Signals affecting adipocyte development in early postnatal life have a strong potential to trigger childhood obesity; however, these signals are still poorly understood. We show here that mitochondrial (mt)RNA efflux stimulates transcription of nuclear-encoded genes for mitobiogenesis and thermogenesis in adipocytes of young mice and human infants. While cytosolic mtRNA is a potential trigger of the interferon (IFN) response, young adipocytes lack such a response to cytosolic mtRNA due to the suppression of IFN regulatory factor (IRF)7 expression by vitamin D receptor signalling. Adult and obese adipocytes, however, strongly express IRF7 and mount an IFN response to cytosolic mtRNA. In turn, suppressing IRF7 expression in adult adipocytes restores mtRNA-induced mitobiogenesis and thermogenesis and eventually mitigates obesity. Retrograde mitochondrion-to-nucleus signalling by mtRNA is thus a mechanism to evoke thermogenic potential during early adipocyte development and to protect against obesity.
Topics: Child; Adult; Humans; Animals; Mice; Adipocytes, Beige; RNA, Mitochondrial; Pediatric Obesity; Adipocytes; Signal Transduction
PubMed: 36443525
DOI: 10.1038/s42255-022-00683-w -
Experimental & Molecular Medicine Feb 2014Brown adipose tissue (BAT) is a specialized thermoregulatory organ that has a critical role in the regulation of energy metabolism. Specifically, energy expenditure can... (Review)
Review
Brown adipose tissue (BAT) is a specialized thermoregulatory organ that has a critical role in the regulation of energy metabolism. Specifically, energy expenditure can be enhanced by the activation of BAT function and the induction of a BAT-like catabolic phenotype in white adipose tissue (WAT). Since the recent recognition of metabolically active BAT in adult humans, BAT has been extensively studied as one of the most promising targets identified for treating obesity and its related disorders. In this review, we summarize information on the developmental origin of BAT and the progenitors of brown adipocytes in WAT. We explore the transcriptional control of brown adipocyte differentiation during classical BAT development and in WAT browning. We also discuss the neuronal control of BAT activity and summarize the recently identified non-canonical stimulators of BAT that can act independently of β-adrenergic stimulation. Finally, we review new findings on the beneficial effects of BAT activation and development with respect to improving metabolic profiles. We highlight the therapeutic potential of BAT and its future prospects, including pharmacological intervention and cell-based therapies designed to enhance BAT activity and development.
Topics: Adipocytes; Adipogenesis; Adipose Tissue, Brown; Animals; Humans; Obesity
PubMed: 24556827
DOI: 10.1038/emm.2013.163 -
International Journal of Molecular... Feb 2022Enlarged, hypertrophic adipocytes are less responsive to insulin and are a hallmark feature of obesity, contributing to many of the negative metabolic consequences of...
Enlarged, hypertrophic adipocytes are less responsive to insulin and are a hallmark feature of obesity, contributing to many of the negative metabolic consequences of excess adipose tissue. Although the mechanisms remain unclear, the adipocyte size appears to be inversely correlated with insulin sensitivity and glucose tolerance, wherein smaller adipocytes are insulin-sensitive and larger adipocytes develop insulin resistance and exhibit an impaired glucose uptake. Thus, pharmacological strategies aimed at regulating adipocyte hypertrophy (increase in adipocyte size) in favor of promoting hyperplasia (increase in adipocyte number) have the potential to improve adipocyte insulin sensitivity and provide therapeutic benefits in the context of metabolic disorders. As white adipose tissue can metabolize large amounts of glucose to lactate, using transcriptomics and in vitro characterization we explore the functional consequences of inhibiting monocarboxylate transporter 1 (MCT1) activity in fully differentiated adipocytes. Our studies show that the pharmacological inhibition of MCT1, a key regulator of the cellular metabolism and proliferation, promotes the re-entry of mature adipocytes into the cell cycle. Furthermore, we demonstrate that inhibitor-treated adipocytes exhibit an enhanced insulin-stimulated glucose uptake as compared with untreated adipocytes, and that this outcome is dependent on the cyclin-dependent kinase 1 (CDK1) activity. In summary, we identify a mechanism though which MCT1 inhibition improves the insulin sensitivity of mature adipocytes by inducing cell cycle re-entry. These results provide the foundation for future studies investigating the role MCT1 plays in adipocyte hyperplasia, and its therapeutic potential as a drug target for obesity and metabolic disease.
Topics: 3T3-L1 Cells; Adipocytes; Animals; CDC2 Protein Kinase; Cell Cycle; Cell Proliferation; Down-Regulation; Glucose; Insulin Resistance; Mice; Models, Biological; Monocarboxylic Acid Transporters; Pyrimidinones; Symporters; Thiophenes
PubMed: 35163825
DOI: 10.3390/ijms23031901 -
PloS One 2019Lipid droplets are lipid-storage organelles with a key role in lipid accumulation pathologies such as diabetes, obesity and atherosclerosis. Despite their important...
Lipid droplets are lipid-storage organelles with a key role in lipid accumulation pathologies such as diabetes, obesity and atherosclerosis. Despite their important functions many aspects of lipid droplets biology are still unknown. This is partially due to the current use of exogenous labels to monitor their formation and remodelling by invasive imaging methods. Here, we apply stimulated Raman scattering microscopy to acquire images with high spatial resolution along with resolving capabilities of lipids and proteins and three-dimensional sectioning. Our images and data analysis demonstrate an increase in the number of large (>15μm2) lipid droplets in human adipocyte cells during differentiation process. In addition, spatially-resolved maps of lipids and proteins inside cells and three dimensional reconstructions of lipids at the initial and final steps of adipocyte differentiation are reported, too.
Topics: 3T3-L1 Cells; Adipocytes; Animals; Cell Differentiation; Imaging, Three-Dimensional; Lipid Droplets; Mice; Nonlinear Optical Microscopy
PubMed: 31112567
DOI: 10.1371/journal.pone.0216811 -
The Keio Journal of Medicine Dec 2005Alcoholic liver disease (ALD) is characterized by accumulation of neutral lipids in hepatocytes leading to micro and macro-vesicular steatosis and balloon cell... (Review)
Review
Alcoholic liver disease (ALD) is characterized by accumulation of neutral lipids in hepatocytes leading to micro and macro-vesicular steatosis and balloon cell degeneration. Hypercaloric alimentation and resultant obesity also cause similar changes as evident in non-alcoholic fatty liver disease (NAFLD). Thus, accumulation of lipids in hepatocytes is a pathologic hallmark of ALD and NAFLD. In contrast, quiescent hepatic stellate cells (HSC) are characterized by the intracellular content of not only vitamin A but also triglycerides, and HSC activation is associated with depletion of these lipids. In fact, our recent work demonstrates that adipogenic/ lipogenic transcriptional regulation rendered by PPARgamma, LXRa, and SREBP-1c is essential for the maintenance of the fat-storing, quiescence phenotype of HSC. Expression of these adipogenic transcription factors is lost in activated HSC and the treatment of the cells with the adipocyte differentiation cocktail or ectopic expression of PPARgamma or SREBP-1c causes a reversal of activated cells to the quiescent phenotype. In steatotic livers from ALD and NAFLD mouse models, the expression of these adipogenic transcription factors is induced while the normal control livers lack such expression. Thus, adipogenic regulation is essential for HSC quiescence while it makes hepatocytes steatotic. Interestingly, under the adipogenic conditions of ALD and NAFLD, HSC are still activated to cause fibrosis. This fat paradox in hepatocytes and HSC highlights contrasted significance of fat in these two cell types that depend on each other for their homeostatic control. It further suggests, activated HSC in steatotic livers may have defective insulin signaling or lipogenic regulation.
Topics: Adipocytes; Fatty Liver; Hepatocytes; Humans; PPAR gamma; Signal Transduction; Transcriptional Activation
PubMed: 16452829
DOI: 10.2302/kjm.54.190 -
Journal of Natural Medicines Apr 2014Recently people often suffer from unhealthy energy metabolism balance as they tend to take more energy than required. Normally, excess energy taken in is converted into... (Review)
Review
Recently people often suffer from unhealthy energy metabolism balance as they tend to take more energy than required. Normally, excess energy taken in is converted into triglyceride and stored in adipocyte as lipid droplets. Recent studies have suggested that irregular accumulation of triglyceride in adipocyte might be a cause of many metabolic diseases. Thus, the awareness of the detrimental effects on health of excessive lipid droplets accumulation (LDA) has urged the development or finding of drugs to counter this effect, including those from botanical origins. This review summarized recent progress in this field from the viewpoint of crude drug studies with references to their anti-LDA activity. Possible mechanisms involved in their anti-LDA effect and isolations of the relevant bioactive compounds were also discussed.
Topics: Adipocytes; Humans; Lipid Metabolism; Plant Extracts
PubMed: 24550097
DOI: 10.1007/s11418-014-0822-3 -
The Journal of Biological Chemistry Dec 2004MicroRNAs (miRNAs) are endogenously expressed 20-24 nucleotide RNAs thought to repress protein translation through binding to a target mRNA (1-3). Only a few of the more...
MicroRNAs (miRNAs) are endogenously expressed 20-24 nucleotide RNAs thought to repress protein translation through binding to a target mRNA (1-3). Only a few of the more than 250 predicted human miRNAs have been assigned any biological function. In an effort to uncover miRNAs important during adipocyte differentiation, antisense oligonucleotides (ASOs) targeting 86 human miRNAs were transfected into cultured human pre-adipocytes, and their ability to modulate adipocyte differentiation was evaluated. Expression of 254 miRNAs in differentiating adipocytes was also examined on a miRNA microarray. Here we report that the combination of expression data and functional assay results identified a role for miR-143 in adipocyte differentiation. miR-143 levels increased in differentiating adipocytes, and inhibition of miR-143 effectively inhibited adipocyte differentiation. In addition, protein levels of the proposed miR-143 target ERK5 (4) were higher in ASO-treated adipocytes. These results demonstrate that miR-143 is involved in adipocyte differentiation and may act through target gene ERK5.
Topics: Adipocytes; Base Sequence; Cell Differentiation; Cells, Cultured; DNA Probes; Humans; MicroRNAs; Oligodeoxyribonucleotides, Antisense; Oligonucleotide Array Sequence Analysis; Transfection
PubMed: 15504739
DOI: 10.1074/jbc.C400438200 -
American Journal of Physiology.... Aug 2015Adipose tissue has the largest capacity to store energy in the body and provides energy through the release of free fatty acids during times of energy need. Different... (Review)
Review
Adipose tissue has the largest capacity to store energy in the body and provides energy through the release of free fatty acids during times of energy need. Different types of immune cells are recruited to adipose tissue under various physiological conditions, indicating that these cells contribute to the regulation of adipose tissue. One major pathway influenced by a number of immune cells is the release of free fatty acids through lipolysis during both physiological (e.g., cold stress) and pathophysiological processes (e.g., obesity, type 2 diabetes). Adipose tissue expansion during obesity leads to immune cell infiltration and adipose tissue remodeling, a homeostatic process that promotes inflammation in adipose tissue. The release of proinflammatory cytokines stimulates lipolysis and causes insulin resistance, leading to adipose tissue dysfunction and systemic disruptions of metabolism. This review focuses on the interactions of cytokines and other inflammatory molecules that regulate adipose tissue lipolysis during physiological and pathophysiological states.
Topics: Adipocytes; Animals; Cytokines; Humans; Insulin Resistance; Lipolysis; Macrophage Activation; Models, Biological; Panniculitis; Receptors, Pattern Recognition
PubMed: 26058863
DOI: 10.1152/ajpendo.00053.2015 -
Journal of Applied Physiology... Oct 2020Skeletal disuse can cause an accumulation of bone marrow adipose tissue (MAT) characterized by a combination of marrow adipocyte hyperplasia and/or hypertrophy. The...
Skeletal disuse can cause an accumulation of bone marrow adipose tissue (MAT) characterized by a combination of marrow adipocyte hyperplasia and/or hypertrophy. The malleability of MAT accumulation and of the hyperplasia and hypertrophy upon remobilization is unknown. In this study, we showed extensive hyperplasia and accelerated hypertrophy of bone marrow adipocytes in the proximal tibia epiphysis of rat knees immobilized for durations between 1 and 32 wk. Similar histomorphometric measures of adipocytes carried out in unoperated controls allowed distinguishing the effects of immobilization from the effects of aging. Although both knee immobilization and aging led to adipocyte hypertrophy, adipocyte hyperplasia was the hallmark signature effect of immobilization on MAT. Both bone marrow adipocyte hyperplasia and hypertrophy were sustained despite knee remobilization for durations up to four times the duration of immobilization. These results suggest that adipocyte hyperplasia is the predominant mechanism explaining MAT accumulation in skeletal disuse. In this model, the changes were unremitting for the investigated time points. Investigating the cellular and molecular mechanisms of marrow adipocyte mechanoregulation will be important to better understand how adipocytes adapt to changes in mechanical environments. This longitudinal study elucidates the response of marrow adipose tissue adipocytes in weight-bearing joints to changes in different mechanical environments, and we provide insight on the malleability of the changes over time. In a rat animal model, knee immobilization induced hyperplasia and accelerated the age-dependent hypertrophy of adipocytes. Changes in adipocyte number and size were sustained despite unassisted remobilization. Multimodal distributions of cell size were characteristic of bone marrow adipocytes.
Topics: Adipocytes; Animals; Bone Marrow; Hyperplasia; Hypertrophy; Longitudinal Studies; Rats
PubMed: 32853104
DOI: 10.1152/japplphysiol.00539.2020 -
Adipocyte Dec 2022Adipogenesis involves complex interactions between transcription and metabolic signalling. Exploration of the developmental characteristics of intramuscular adipocyte...
Adipogenesis involves complex interactions between transcription and metabolic signalling. Exploration of the developmental characteristics of intramuscular adipocyte will provide targets for enhancing beef cattle marbling without increasing obesity. Few reports have compared bovine perirenal and intramuscular adipocyte transcriptomes using the combined analysis of transcriptomes and lipid metabolism to explore differences in adipogenic characteristics. We identified perirenal preadipocytes (PRA) and intramuscular preadipocytes (IMA) in Qinchuan cattle. We found that IMA were highly prolific in the early stages of adipogenesis, while PRA shows a stronger adipogenic ability in the terminal differentiation. Bovine perirenal and intramuscular adipocytes were detected through the combined analysis of the transcriptome and metabolome. More triglyceride was found to be upregulated in perirenal adipocytes; however, more types and amounts of unsaturated fatty acids were detected in intramuscular adipocytes, including eicosapentaenoic acid (20:5 n-3; EPA) and docosahexaenoic acid (22:6 n-3; DHA). Furthermore, differentially expressed genes in perirenal and intramuscular adipocytes were positively correlated with the eicosanoid, phosphatidylcholine (PC), phosphatidyl ethanolamine (PE), and sphingomyelin contents. Associated differential metabolic pathways included the glycerolipid and glycerophospholipid metabolisms. Our research findings provide a basis for the screening of key metabolic pathways or genes and metabolites involved in intramuscular fat production in cattle.
Topics: Adipocytes; Adipogenesis; Animals; Cattle; Cell Differentiation; Lipid Metabolism; Lipidomics; RNA-Seq
PubMed: 35941812
DOI: 10.1080/21623945.2022.2106051