| 1. |
- Mishra, Devesh, et al.
(författare)
-
Parabrachial Interleukin-6 Reduces Body Weight and Food Intake and Increases Thermogenesis to Regulate Energy Metabolism
- 2019
-
Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 26:11
-
Tidskriftsartikel (refereegranskat)abstract
- Chronic low-grade inflammation and increased serum levels of the cytokine IL-6 accompany obesity. For brain-produced IL-6, the mechanisms by which it controls energy balance and its role in obesity remain unclear. Here, we show that brain-produced IL-6 is decreased in obese mice and rats in a neuro-anatomically and sex-specific manner. Reduced IL-6 mRNA localized to lateral parabrachial nucleus (IPBN) astrocytes, microglia, and neurons, including paraventricular hypothalamus-innervating IPBN neurons. IL-6 microinjection into IPBN reduced food intake and increased brown adipose tissue (BAT) thermogenesis in male lean and obese rats by increasing thyroid and sympathetic outflow to BAT. Parabrachial IL-6 interacted with leptin to reduce feeding. siRNA-mediated reduction of IPBN IL-6 leads to increased weight gain and adiposity, reduced BAT thermogenesis, and increased food intake. Ambient cold exposure partly normalizes the obesity-induced suppression of IPBN IL-6. These results indicate that IPBN-produced IL-6 regulates feeding and metabolism and pinpoints (patho)physiological contexts interacting with IPBN IL-6.
|
|
| 2. |
- Brännmark, Cecilia, et al.
(författare)
-
Mathematical modeling of white adipocyte exocytosis predicts adiponectin secretion and quantifies the rates of vesicle exo- and endocytosis
- 2017
-
Ingår i: Journal of Biological Chemistry. - : AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC. - 0021-9258 .- 1083-351X. ; 292:49, s. 20032-20043
-
Tidskriftsartikel (refereegranskat)abstract
- Adiponectin is a hormone secreted from white adipocytes and takes part in the regulation of several metabolic processes. Although the pathophysiological importance of adiponectin has been thoroughly investigated, the mechanisms controlling its release are only partly understood. We have recently shown that adiponectin is secreted via regulated exocytosis of adiponectin-containing vesicles, that adiponectin exocytosis is stimulated by cAMP-dependent mechanisms, and that Ca2+ and ATP augment the cAMP-triggered secretion. However, much remains to be discovered regarding the molecular and cellular regulation of adiponectin release. Here, we have used mathematical modeling to extract detailed information contained within our previously obtained high-resolution patch-clamp time-resolved capacitance recordings to produce the first model of adiponectin exocytosis/secretion that combines all mechanistic knowledge deduced from electrophysiological experimental series. This model demonstrates that our previous understanding of the role of intracellular ATP in the control of adiponectin exocytosis needs to be revised to include an additional ATP-dependent step. Validation of the model by introduction of data of secreted adiponectin yielded a very close resemblance between the simulations and experimental results. Moreover, we could show that Ca2+-dependent adiponectin endocytosis contributes to the measured capacitance signal, and we were able to predict the contribution of endocytosis to the measured exocytotic rate under different experimental conditions. In conclusion, using mathematical modeling of published and newly generated data, we have obtained estimates of adiponectin exo- and endocytosis rates, and we have predicted adiponectin secretion. We believe that our model should have multiple applications in the study of metabolic processes and hormonal control thereof.
|
|
| 3. |
- El Hachmane, Michael, et al.
(författare)
-
A mechanically activated TRPC1-like current in white adipocytes
- 2018
-
Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 498:4, s. 736-742
-
Tidskriftsartikel (refereegranskat)abstract
- © 2018 Elsevier Inc. Ca 2+ impacts a large array of cellular processes in every known cell type. In the white adipocyte, Ca 2+ is involved in regulation of metabolic processes such as lipolysis, glucose uptake and hormone secretion. Although the importance of Ca 2+ in control of white adipocyte function is clear, knowledge is still lacking regarding the control of dynamic Ca 2+ alterations within adipocytes and mechanisms inducing intracellular Ca 2+ changes remain elusive. Own work has recently demonstrated the existence of store-operated Ca 2+ entry (SOCE) in lipid filled adipocytes. We defined stromal interaction molecule 1 (STIM1) and the calcium release-activated calcium channel protein 1 (ORAI1) as the key players involved in this process and we showed that the transient receptor potential (TRP) channel TRPC1 contributed to SOCE. Here we have aimed to further characterised SOCE in the white adipocyte by use of single cell whole-cell patch clamp recordings. The electrophysiological measurements show the existence of a seemingly constitutively active current that is inhibited by known store-operated Ca 2+ channel (SOCC) blockers. We demonstrate that the mechanical force applied to the plasma membrane upon patching leads to an elevation of the cytoplasmic Ca 2+ concentration and that this elevation can be reversed by SOCC antagonists. We conclude that a mechanically activated current with properties similar to TRPC1 is present in white adipocytes. Activation of TRPC1 by membrane tension/stretch may be specifically important for the function of this cell type, since adipocytes can rapidly increase or decrease in size.
|
|
| 4. |
- El Hachmane, Michael, et al.
(författare)
-
Cooling Reduces cAMP-Stimulated Exocytosis and Adiponectin Secretion at a Ca2+-Dependent Step in 3T3-L1 Adipocytes
- 2015
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 10:3
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated the effects of temperature on white adipocyte exocytosis (measured as increase in membrane capacitance) and short-term adiponectin secretion with the aim to elucidate mechanisms important in regulation of white adipocyte stimulus-secretion coupling. Exocytosis stimulated by cAMP (included in the pipette solution together with 3 mM ATP) in the absence of Ca2+ (10 mM intracellular EGTA) was equal at all investigated temperatures (23 degrees C, 27 degrees C, 32 degrees C and 37 degrees C). However, the augmentation of exocytosis induced by an elevation of the free cytosolic [Ca2+] to similar to 1.5 mu M (9mMCa(2+) + 10 mM EGTA) was potent at 32 degrees C or 37 degrees C but less distinct at 27 degrees C and abolished at 23 degrees C. Adiponectin secretion stimulated by 30 min incubations with the membrane permeable cAMP analogue 8-Br-cAMP (1 mM) or a combination of 10 mu M forskolin and 200 mu M IBMX was unaffected by a reduction of temperature from 32 degrees C to 23 degrees C. At 32 degrees C, cAMP-stimulated secretion was 2-fold amplified by inclusion of the Ca2+ ionophore ionomycin (1 mu M), an effect that was not observed at 23 degrees C. We suggest that cooling affects adipocyte exocytosis/adiponectin secretion at a Ca2+-dependent step, likely involving ATP-dependent processes, important for augmentation of cAMP-stimulated adiponectin release.
|
|
| 5. |
- El Hachmane, Michael, et al.
(författare)
-
Extracellular ATP activates store-operated Ca2+ entry in white adipocytes: functional evidence for STIM1 and ORAI1
- 2018
-
Ingår i: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 475, s. 691-704
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, we have applied ratiometric measurements of intracellular Ca2+ concentrations ([Ca2+](i)) to show that extracellularly applied ATP (adenosine triphosphate) (100 mM) stimulates store-operated Ca2+ entry (SOCE) in 3T3-L1 adipocytes. ATP produced a rapid increase in [Ca2+](i) consisting of an initial transient elevation followed by a sustained elevated phase that could be observed only in the presence of extracellular Ca2+. Gene expression data and [Ca2+](i) recordings with uridine-50-triphosphate or with the phospholipase C (PLC) inhibitor U73122 demonstrated the involvement of purinergic P2Y2 receptors and the PLC/inositol trisphosphate pathway. The [Ca2+](i) elevation produced by reintroduction of a Ca2+-containing intracellular solution to adipocytes exposed to ATP in the absence of Ca2+ was diminished by known SOCE antagonists. The chief molecular components of SOCE, the stromal interaction molecule 1 (STIM1) and the calcium release-activated calcium channel protein 1 (ORAI1), were detected at the mRNA and protein level. Moreover, SOCE was largely diminished in cells where STIM1 and/or ORAI1 had been silenced by small interfering (si) RNA. We conclude that extracellular ATP activates SOCE in white adipocytes, an effect predominantly mediated by STIM1 and ORAI1.
|
|
| 6. |
- Komai, Ali, 1987, et al.
(författare)
-
White Adipocyte Adiponectin Exocytosis Is Stimulated via beta(3)-Adrenergic Signaling and Activation of Epac1: Catecholamine Resistance in Obesity and Type 2 Diabetes
- 2016
-
Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 65:11, s. 3301-3313
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated the physiological regulation of adiponectin exocytosis in health and metabolic disease by a combination of membrane capacitance patch-clamp recordings and biochemical measurements of short-term (30-min incubations) adiponectin secretion. Epinephrine or the beta(3)-adrenergic receptor (AR) agonist CL 316,243 (CL) stimulated adiponectin exocytosis/secretion in cultured 3T3-L1 and in primary subcutaneous mouse adipocytes, and the stimulation was inhibited by the Epac (Exchange Protein directly Activated by cAMP) antagonist ESI-09. The beta(3)AR was highly expressed in cultured and primary adipocytes, whereas other ARs were detected at lower levels. 3T3-L1 and primary adipocytes expressed Epac1, whereas Epac2 was undetectable. Adiponectin secretion could not be stimulated by epinephrine or CL in adipocytes isolated from obese/type 2 diabetic mice, whereas the basal (unstimulated) adiponectin release level was elevated twofold. Gene expression of beta(3)AR and Epac1 was reduced in adipocytes from obese animals, and corresponded to a respective similar to 35% and similar to 30% reduction at the protein level. Small interfering RNA-mediated knockdown of beta(3)AR (similar to 60%) and Epac1 (similar to 50%) was associated with abrogated catecholamine-stimulated adiponectin secretion. We propose that adiponectin exocytosis is stimulated via adrenergic signaling pathways mainly involving beta(3)ARs. We further suggest that adrenergically stimulated adiponectin secretion is disturbed in obesity/type 2 diabetes as a result of the reduced expression of beta(3)ARs and Epac1 in a state we define as "catecholamine resistance."
|
|
| 7. |
- Peris, Eduard, et al.
(författare)
-
Antioxidant treatment induces reductive stress associated with mitochondrial dysfunction in adipocytes
- 2019
-
Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294:7, s. 2340-2352
-
Tidskriftsartikel (refereegranskat)abstract
- beta-Adrenergic stimulation of adipose tissue increases mitochondrial density and activity (browning) that are associated with improved whole-body metabolism. Whereas chronically elevated levels of reactive oxygen species (ROS) in adipose tissue contribute to insulin resistance, transient ROS elevation stimulates physiological processes such as adipogenesis. Here, using a combination of biochemical and cell and molecular biology-based approaches, we studied whether ROS or antioxidant treatment affects beta 3-adrenergic receptor (beta 3-AR) stimulation-induced adipose tissue browning. We found that beta 3-AR stimulation increases ROS levels in cultured adipocytes, but, unexpectedly, pretreatment with different antioxidants (N-acetylcysteine, vitamin E, or GSH ethyl ester) did not prevent this ROS increase. Using fluorescent probes, we discovered that the antioxidant treatments instead enhanced beta 3-AR stimulation-induced mitochondrial ROS production. This pro-oxidant effect of antioxidants was, even in the absence of beta 3-AR stimulation, associated with decreased oxygen consumption and increased lactate production in adipocytes. We observed similar antioxidant effects in WT mice: N-acetylcysteine blunted beta 3-AR stimulation-induced browning of white adipose tissue and reduced mitochondrial activity in brown adipose tissue even in the absence of beta 3-AR stimulation. Furthermore, N-acetylcysteine increased the levels of peroxiredoxin 3 and superoxide dismutase 2 in adipose tissue, indicating increased mitochondrial oxidative stress. We interpret this negative impact of antioxidants on oxygen consumption in vitro and adipose tissue browning in vivo as essential adaptations that prevent a further increase in mitochondrial ROS production. In summary, these results suggest that chronic antioxidant supplementation can produce a paradoxical increase in oxidative stress associated with mitochondrial dysfunction in adipocytes.
|
|
| 8. |
- Rajan, M. R., et al.
(författare)
-
Inhibition of FOXO1 transcription factor in primary human adipocytes mimics the insulin-resistant state of type 2 diabetes
- 2018
-
Ingår i: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 475:10, s. 1807-1820
-
Tidskriftsartikel (refereegranskat)abstract
- Type 2 diabetes is characterized by insulin resistance in the expanding adipose tissue of obesity. The insulin resistance manifests in human adipocytes as system-wide impairment of insulin signalling. An exception is the regulation of transcription factor FOXO1 (forkhead box protein O1), which is phosphorylated downstream of mTORC2 (mammalian/mechanistic target of rapamycin in complex with raptor) and is therefore not exhibiting impaired response to insulin. However, the abundance, and activity, of FOXO1 is reduced by half in adipocytes from patients with diabetes. To elucidate the effect of reduced FOXO1 activity, we here transduced human adipocytes with a dominant-negative construct of FOXO1 (DN-FOXO1). Inhibition of FOXO1 reduced the abundance of insulin receptor, glucose transporter-4, ribosomal protein S6, mTOR and raptor. Functionally, inhibition of FOXO1 induced an insulin-resistant state network-wide, a state that qualitatively and quantitatively mimicked adipocytes from patients with type 2 diabetes. In contrast, and in accordance with these effects of DN-FOXO1, overexpression of wild-type FOXO1 appeared to augment insulin signalling. We combined experimental data with mathematical modelling to show that the impaired insulin signalling in FOXO1-inhibited cells to a large extent can be explained by reduced mTORC1 activity - a mechanism that defines much of the diabetic state in human adipocytes. Our findings demonstrate that FOXO1 is critical for maintaining normal insulin signalling of human adipocytes.
|
|
| 9. |
- Saliha, Musovic, 1990, et al.
(författare)
-
Adrenergic stimulation of adiponectin secretion in visceral mouse adipocytes is blunted in high-fat diet induced obesity
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- The hormone adiponectin is secreted by white adipocytes and has been put forward as a key mediator of obesity-linked insulin resistance and the metabolic syndrome. Although adiponectin was discovered two decades ago, the knowledge about the molecular and cellular regulation of its secretion is incomplete. Here we have investigated the adrenergic regulation of adiponectin secretion in primary visceral (gonadal) adipocytes isolated from lean or obese/diabetic mice. We show that visceral adipocyte adiponectin release is triggered by cAMP/catecholamines via signalling pathways involving adrenergic beta-3-receptors (beta(3)ARs) and Exchange Protein directly Activated by cAMP, isoform 1 (Epac1). The adrenergically stimulated adiponectin secretion is blunted in visceral adipocytes isolated from obese and diabetic mice and our results suggest the existence of a secretory defect. We have previously shown that adiponectin secretion in subcutaneous adipocytes is abolished in the obese/diabetic state due to reduced abundance of beta(3)ARs and Epac1. However, here we show that protein levels of beta(3)ARs and Epac1 are maintained in visceral adipocytes from obese/diabetic mice proposing that other molecular defects underlie the blunted adiponectin release. Gene expression analysis indicate diabesity-associated disturbances of the signalling downstream of Epac1 and/or the exocytotic process itself. Our study proposes that visceral adipocytes partake in the regulated secretion of adiponectin and may thus influence circulating levels of the hormone, in health and in metabolic disease.
|
|
| 10. |
- Svennerholm, Kristina, 1981, et al.
(författare)
-
Escherichia coli outer membrane vesicles can contribute to sepsis induced cardiac dysfunction.
- 2017
-
Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Sepsis induced cardiac dysfunction (SIC) is a severe complication to sepsis which significantly worsens patient outcomes. It is known that bacteria have the capacity to release outer membrane vesicles (OMVs), which are nano-sized bilayered vesicles composed of lipids and proteins, that can induce a fatal inflammatory response. The aim of this study was to determine whether OMVs from a uropathogenic Escherichia coli strain can induce cardiac dysfunction, and to elucidate any mechanisms involved. OMVs induced irregular Ca2+ oscillations with a decreased frequency in cardiomyocytes through recordings of intracellular Ca2+ dynamics. Mice were intraperitoneally injected with bacteria-free OMVs, which resulted in increased concentration of pro-inflammatory cytokine levels in blood. Cytokines were increased in heart lysates, and OMVs could be detected in the heart after OMVs injection. Troponin T was significantly increased in blood, and echocardiography showed increased heart wall thickness as well as increased heart rate. This study shows that E. coli OMVs induce cardiac injury in vitro and in vivo, in the absence of bacteria, and may be a causative microbial signal in SIC. The role of OMVs in clinical disease warrant further studies, as bacterial OMVs in addition to live bacteria may be good therapeutic targets to control sepsis.
|
|
