Biology subjects

Musovic, S.

Publications and source records attributed to Musovic, S..

3 recordsLinked to original sources

bioRxiv2022

Adipocyte-specific ablation of the Ca2+ pump SERCA2 impairs whole-body metabolic function and reveals the diverse metabolic flexibility of white and brown adipose tissue.

ObjectiveSarco/endoplasmic reticulum Ca2+-ATPase (SERCA) transports Ca2+ from the cytosol into the ER and is essential for appropriate regulation of intracellular Ca2+ homeostasis. The objective of this study was to test the hypothesis that SERCA pumps are involved in the regulation of white adipocyte hormone secretion and other aspects of adipose tissue function and that this control is disturbed in obesity-induced type-2 diabetes. MethodsSERCA expression was measured in isolated human and mouse adipocytes as well as in whole mouse adipose tissue by Western blot and RT-qPCR. To test the significance of SERCA2 in adipocyte functionality and whole-body metabolism, we generated adipocyte-specific SERCA2 knockout mice. The mice were metabolically phenotyped by glucose tolerance and tracer studies, histological analyses, measurements of glucose- stimulated insulin release in isolated islets, and gene/protein expression analyses. We also tested the effect of pharmacological SERCA inhibition and genetic SERCA2 ablation in cultured adipocytes. Intracellular and mitochondrial Ca2+ levels were recorded with dual-wavelength ratio imaging and mitochondrial function was assessed by Seahorse technology. ResultsWe demonstrate that SERCA2 is downregulated in white adipocytes from patients with obesity and type-2 diabetes as well as in adipocytes from diet-induced obese mice. SERCA2-ablated adipocytes display disturbed Ca2+ homeostasis associated with upregulated ER stress markers and impaired hormone release. These adipocyte alterations are linked to mild lipodystrophy, reduced adiponectin levels, and impaired glucose tolerance. Interestingly, adipocyte-specific SERCA2 ablation leads to increased glucose uptake in white adipose tissue while glucose uptake is reduced in brown adipose tissue. This dichotomous effect on glucose uptake is due to differently regulated mitochondrial function. In white adipocytes, SERCA2 deficiency triggers an adaptive increase in Fgf21, increased mitochondrial UCP1 levels, and increased oxygen consumption rate (OCR). In contrast, brown SERCA2 null adipocytes display reduced OCR despite increased mitochondrial content and UCP1 levels compared to wild type controls. ConclusionsOur data suggest causal links between reduced white adipocyte SERCA2 levels, deranged adipocyte Ca2+ homeostasis, adipose tissue dysfunction and type-2 diabetes. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/483886v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@ce9737org.highwire.dtl.DTLVardef@129abaeorg.highwire.dtl.DTLVardef@c63342org.highwire.dtl.DTLVardef@4f47fe_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIAdipocyte SERCA2 is downregulated in human subjects with type-2 diabetes C_LIO_LILoss of SERCA2 disturbs the intracellular Ca2+ homeostasis in adipocytes C_LIO_LIImpaired metabolism and altered adipokine levels in adipocyte-SERCA2 null mice C_LIO_LILoss of SERCA2 accelerates metabolic processes in white adipocytes C_LIO_LILoss of SERCA2 impairs the mitochondrial function of brown adipocytes C_LI

physiology↗

bioRxiv2021

Noradrenaline and ATP regulate white adipocyte adiponectin exocytosis: disturbed adrenergic and purinergic signalling in obesity-associated diabetes.

White adipocyte adiponectin exocytosis is triggered by cAMP and a concomitant increase of cytosolic Ca2+ potentiates its release. White adipose tissue is richly innervated by sympathetic nerves co-releasing noradrenaline (NA) and ATP that may act on receptors in the adipocyte plasma membrane to increase cAMP via adrenergic receptors and Ca2+ via purinergic receptors, respectively. Here we determine the importance of NA and ATP for the regulation of white adipocyte adiponectin exocytosis, at the cellular and molecular level, and we specifically detail the ATP signalling pathway. Immunohistochemical staining demonstrates that tyrosine hydroxylase (enzyme involved in catecholamine synthesis) is dramatically reduced in inguinal white adipose tissue (IWAT) isolated from mice with diet-induced obesity; this is associated with diminished levels of NA in IWAT and with lowered serum adiponectin. Adiponectin exocytosis (measured as increase in plasma membrane capacitance and as secreted product) is triggered by NA or ATP alone in cultured and primary mouse IWAT adipocytes, and enhanced by a combination of the two secretagogues. The ATP-induced adiponectin exocytosis is largely Ca2+-dependent and activated via P2Y2 receptors (P2Y2Rs) and the Gq11/PLC pathway. Adiponectin release induced by the nucleotide is abrogated in adipocytes isolated from obese/diabetic mice and this is associated with [~]70% reduced abundance of P2Y2Rs. The NA-triggered adiponectin exocytosis is likewise abolished in "obese adipocytes", concomitant with a 50% lower gene expression of beta 3 adrenergic receptors ({beta}3ARs). The NA-stimulated adiponectin secretion does not contain Ca2+-dependent components. Collectively, our data suggest that sympathetic innervation is a principal regulator of adiponectin exocytosis and that disruptions of this control are associated with the obesity-associated reduction of circulating levels of HMW adiponectin. Key point listO_LIWhite adipose tissue is richly innervated by sympathetic nerves that co-release noradrenaline (NA) and ATP. C_LIO_LIProtein levels of tyrosine hydroxylase and NA are dramatically decreased in white adipose tissue from obese/diabetic mice, concomitant with reduced serum levels of high-molecular weight (HMW) adiponectin. C_LIO_LINA and ATP stimulate white adipocyte adiponectin exocytosis via beta adrenergic and purinergic receptors respectively. The ATP-induced adiponectin secretion is chiefly Ca2+-dependent and activated via the P2Y2/Gq11/PLC pathway. C_LIO_LIThe purinergic signalling is abrogated in adipocytes from obese/diabetic mice, due to reduced abundance of P2Y2Rs. The response to NA is likewise abolished in "obese adipocytes", associated with lowered gene expression of beta 3 adrenergic receptors ({beta}3ARs). C_LIO_LIWe propose that sympathetic innervation is central in regulation of adiponectin exocytosis via co-secretion of NA and ATP and that this control is disrupted in obesity-associated diabetes, leading to lower circulating levels of HMW adiponectin. C_LI

physiology↗

bioRxiv2020

Conjugative dissemination of plasmids in rapid sand filters: a trojan horse strategy to enhance pesticide degradation in groundwater treatment

The supply of clean water for human consumption is being challenged by the appearance of pesticide pollutants in groundwater ecosystems. Biological rapid sand filtration is a commonly employed method for the removal of organic and inorganic impurities in water which relies on the degradative properties of microorganisms for the removal of diverse contaminants, including pesticides. Although sustainable and relatively inexpensive, the bioremediation capabilities of rapid sand filters vary greatly across waterworks. Bioaugmentation efforts with degradation-proficient bacteria have proven difficult due to the inability of the exogenous microbes to stably colonize the sand filters. Pesticide degrading genes, however, are often encoded naturally by plasmids--extrachromosomal DNA elements that can transfer between bacteria--yet their ability to spread within rapid sand filters have remained unknown. To evaluate the potential use of plasmids for the dissemination of pesticide degrading genes, we examined the permissiveness of rapid sand filter communities towards four environmental transmissible plasmids; RP4, RSF1010, pKJK5 and TOL (pWWO), using a dual-fluorescent bioreporter platform combined with FACS and 16S rRNA gene amplicon sequencing. Our results reveal that plasmids can transfer at high frequencies and across distantly related taxa from rapid sand filter communities, emphasizing their suitability for introducing pesticide degrading determinants in the microbiomes of underperforming water purification plants.

microbiology↗