scholarly journals Early enforcement of cell identity by a functional component of the terminally differentiated state

2020 ◽  
Author(s):  
Zahra Bahrami-Nejad ◽  
Tinghuan Chen ◽  
Stefan Tholen ◽  
Zhi-Bo Zhang ◽  
Atefeh Rabiee ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Positive Feedback ◽  
Feedback Loops ◽  
Second Phase ◽  
List Type ◽  
Fat Cells ◽  
Core Component ◽  
Cell Identity ◽  
Positive Feedbacks ◽  
Pparg Expression

ABSTRACTHow progenitor cells can attain a distinct differentiated cell identity is a challenging problem given that critical transcription factors are often not unique to a differentiation process and the fluctuating signaling environment in which cells exist. Here we test the hypothesis that a unique differentiated cell identity can result from a core component of the differentiated state doubling up as a signaling protein that also drives differentiation. Using live single-cell imaging in the adipocyte differentiation system, we show that progenitor fat cells (preadipocytes) can only commit to terminally differentiate after upregulating FABP4, a lipid buffer that is highly enriched in mature adipocytes. Upon induction of adipogenesis, we show that after a long delay, cells first abruptly start to engage a positive feedback between CEBPA and PPARG before then engaging, after a second delay, a positive feedback between FABP4 and PPARG. These sequential positive feedbacks both need to engage in order to drive PPARG levels past the threshold for irreversible differentiation. In the last step before commitment, PPARG transcriptionally increases FABP4 expression while fatty-acid loaded FABP4 binds to and increases PPARG activity. Together, our study suggests a control principle for robust cell identity whereby a core component of the differentiated state also promotes differentiation from its own progenitor state.HIGHLIGHTSFatty-acid loaded FABP4 binds to and increases PPARG expression, thereby turning on PPARG positive feedback loops that further increase PPARG expression.FABP4 critically controls the second phase of adipogenesis between activation of the feedback loops and reaching the threshold to differentiate.Only a small fraction (∼10%) of the FABP4 levels typically attained in mature fat cells is needed to commit cells to the differentiated state, thus providing an explanation for why maintenance of the mature adipocyte state is so robust.

scholarly journals Inflammation in children with cystic fibrosis: contribution of bacterial production of long-chain fatty acids

2021 ◽  
Author(s):  
Erin Felton ◽  
Aszia Burrell ◽  
Hollis Chaney ◽  
Iman Sami ◽  
Anastassios C. Koumbourlis ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Fatty Acid ◽  
Antibiotic Treatment ◽  
Bacterial Production ◽  
Clinical Status ◽  
Achromobacter Xylosoxidans ◽  
List Type ◽  
Future Studies ◽  
Long Chain

Abstract Background Cystic fibrosis (CF) affects >70,000 people worldwide, yet the microbiologic trigger for pulmonary exacerbations (PExs) remains unknown. The objective of this study was to identify changes in bacterial metabolic pathways associated with clinical status. Methods Respiratory samples were collected at hospital admission for PEx, end of intravenous (IV) antibiotic treatment, and follow-up from 27 hospitalized children with CF. Bacterial DNA was extracted and shotgun DNA sequencing was performed. MetaPhlAn2 and HUMAnN2 were used to evaluate bacterial taxonomic and pathway relative abundance, while DESeq2 was used to evaluate differential abundance based on clinical status. Results The mean age of study participants was 10 years; 85% received combination IV antibiotic therapy (beta-lactam plus a second agent). Long-chain fatty acid (LCFA) biosynthesis pathways were upregulated in follow-up samples compared to end of treatment: gondoate (p = 0.012), oleate (p = 0.048), palmitoleate (p = 0.043), and pathways of fatty acid elongation (p = 0.012). Achromobacter xylosoxidans and Escherichia sp. were also more prevalent in follow-up compared to PEx (p < 0.001). Conclusions LCFAs may be associated with persistent infection of opportunistic pathogens. Future studies should more closely investigate the role of LCFA production by lung bacteria in the transition from baseline wellness to PEx in persons with CF. Impact Increased levels of LCFAs are found after IV antibiotic treatment in persons with CF. LCFAs have previously been associated with increased lung inflammation in asthma. This is the first report of LCFAs in the airway of persons with CF. This research provides support that bacterial production of LCFAs may be a contributor to inflammation in persons with CF. Future studies should evaluate LCFAs as predictors of future PExs.

scholarly journals The regulation of glyceride synthesis in isolated white-fat cells. The effects of palmitate and lipolytic agents

1972 ◽  
Vol 128 (5) ◽  
pp. 1057-1067 ◽  
Author(s):  
E. D Saggerson
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acids ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Fat Cells ◽  
Glyceride Synthesis ◽  
Glucose Incorporation ◽  
High Concentrations ◽  
Stimulation Of

1. 0.5mm-Palmitate stimulated incorporation of [U-14C]glucose into glyceride glycerol and fatty acids in normal fat cells in a manner dependent upon the glucose concentration. 2. In the presence of insulin the incorporation of 5mm-glucose into glyceride fatty acids was increased by concentrations of palmitate, adrenaline and 6-N-2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate up to 0.5mm, 0.5μm and 0.5mm respectively. Higher concentrations of these agents produced progressive decreases in the rate of glucose incorporation into fatty acids. 3. The effects of palmitate and lipolytic agents upon the measured parameters of glucose utilization were similar, suggesting that the effects of lipolytic agents are mediated through increased concentrations of free fatty acids. 4. In fat cells from 24h-starved rats, maximal stimulation of glucose incorporation into fatty acids was achieved with 0.25mm-palmitate. Higher concentrations of palmitate were inhibitory. In fat cells from 72h-starved rats, palmitate only stimulated glucose incorporation into fatty acids at high concentrations of palmitate (1mm and above). 5. The ability of fat cells to incorporate glucose into glyceride glycerol in the presence of palmitate decreased with increasing periods of starvation. 6. It is suggested that low concentrations of free fatty acids stimulate fatty acid synthesis from glucose by increasing the utilization of ATP and cytoplasmic NADH for esterification of these free fatty acids. When esterification of free fatty acids does not keep pace with their provision, inhibition of fatty acid synthesis occurs. Provision of free fatty acids far in excess of the esterification capacity of the cells leads to uncoupling of oxidative phosphorylation and a secondary stimulation of fatty acid synthesis from glucose.

scholarly journals FGF2 Translationally Induced by Hypoxia Is Involved in Negative and Positive Feedback Loops with HIF-1α

PLoS ONE ◽  
2008 ◽  
Vol 3 (8) ◽  
pp. e3078 ◽  
Author(s):  
Caroline Conte ◽  
Elodie Riant ◽  
Céline Toutain ◽  
Françoise Pujol ◽  
Jean-François Arnal ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Feedback Loops

scholarly journals Understanding MAPK Signaling Pathways in Apoptosis

2020 ◽  
Vol 21 (7) ◽  
pp. 2346 ◽  
Author(s):  
Jicheng Yue ◽  
José M. López
Keyword(s):  
Signaling Pathways ◽  
Positive Feedback ◽  
Cell Model ◽  
Mapk Signaling ◽  
Feedback Loops ◽  
Mitogen Activated Protein Kinase ◽  
Cellular Mechanisms ◽  
Mitogen Activated Protein ◽  
Induced Apoptosis ◽  
Mapk Signaling Pathways

MAPK (mitogen-activated protein kinase) signaling pathways regulate a variety of biological processes through multiple cellular mechanisms. In most of these processes, such as apoptosis, MAPKs have a dual role since they can act as activators or inhibitors, depending on the cell type and the stimulus. In this review, we present the main pro- and anti-apoptotic mechanisms regulated by MAPKs, as well as the crosstalk observed between some MAPKs. We also describe the basic signaling properties of MAPKs (ultrasensitivity, hysteresis, digital response), and the presence of different positive feedback loops in apoptosis. We provide a simple guide to predict MAPKs’ behavior, based on the intensity and duration of the stimulus. Finally, we consider the role of MAPKs in osmostress-induced apoptosis by using Xenopus oocytes as a cell model. As we will see, apoptosis is plagued with multiple positive feedback loops. We hope this review will help to understand how MAPK signaling pathways engage irreversible cellular decisions.

scholarly journals Ultrasensitive gene regulation by positive feedback loops in nucleosome modification

2008 ◽  
Vol 4 (1) ◽  
pp. 182 ◽  
Author(s):  
Kim Sneppen ◽  
Mille A Micheelsen ◽  
Ian B Dodd
Keyword(s):  
Gene Regulation ◽  
Positive Feedback ◽  
Feedback Loops
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