Biology subjects

Cowart, L. A.

Publications and source records attributed to Cowart, L. A..

9 recordsLinked to original sources

bioRxiv2026

Impaired proteostasis is an early feature of the diabetic heart in humans and mice

Diabetes and obesity increase cardiac lipid levels leading to cardiomyopathy and heart failure. We hypothesized that intermittent fasting would reduce cardiac lipid levels. Surprisingly, intermittent fasting increased myocardial triglyceride content, but rescued mortality and attenuated cardiomyopathy in mice overexpressing cardiomyocyte acyl-CoA synthetase 1 (MHC-ACSL1). Lipid overload caused cardiomyocyte accumulation of polyubiquitinated protein aggregates containing desmin, a scaffolding intermediate filament protein, which intermittent fasting prevented. Furthermore, intermittent fasting reversed elevated myocardial C16:0 ceramide content, and knockdown of ceramide synthase CerS5 and CerS6 reduced palmitate-induced protein aggregation, highlighting a role for C16:0 ceramides in this pathology. Conversely, impairing aggrephagy with cardiomyocyte-specific p62 ablation induced heart failure in mice fed a high-fat diet, with paradoxically reduced cardiac lipid content. Crucially, non-failing diabetic human hearts also exhibited protein aggregate pathology. Taken together, these results demonstrate that impaired proteostasis characterizes cardiomyopathy from cardiac lipid overload and identify a promising new therapeutic target for this condition.

molecular biology↗

bioRxiv2026

Impact of the sphingolipid metabolizing enzyme β-galactosylceramidase on mitochondrial sphingolipid profile and energetic metabolism in human melanoma cells

Mitochondrial plasticity, characterized by the dynamic balance between glycolysis and oxidative phos-phorylation in response to genetic and microenvironmental changes, is a hallmark of melanoma progression. Sphingolipids play a significant role in various aspects of cancer cell biology, including metabolic reprogramming. Previous observations had shown that the lysosomal sphingolipid-metabolizing enzyme {beta}-galactosylceramidase (GALC) rewires the lipid profile of mouse melanoma cells, exerting pro-oncogenic functions, gene silencing leading to a decreased oncogenic activity in murine and human melanoma cells. Here, we have focused on the mitochondrial sphingolipid composition and energetic metabolism in GALC knockout (KO) A2058 human melanoma cells. Targeted analysis of the mitochondrial sphingolipid profile, transcriptomic data, and mitochondrial structural and functional studies indicate that GALC loss drives a sphingolipid-mediated reprogramming of mitochondrial metabolism in absence of major structural alterations, characterized by bioenergetic insufficiency possibly due to ceramide- and sphingomyelin-driven impairment of respiratory chain function. Overall, these data indicate that GALC KO leads to a sphin-golipid-driven mitochondrial metabolic suppression and may provide novel information for the development of efficacious approaches in mitochondrial targeting melanoma therapies.

cancer biology↗

bioRxiv2025

Depot-specific roles for sphingosine kinase 1 in conversion of white adipose to thermogenic adipose

BackgroundAs of 2023, approximately 100.1 million adults and 14.7 million children in the USA are obese. Many comorbidities develop with obesity, which impairs quality of life and burdens the health care system. Consequently, there is an urgent need for interventions and treatments to reverse obesity and its comorbidities and restore health. Sphingosine Kinase 1 (SphK1), a key enzyme in sphingolipid metabolism, produces sphingosine-1-phosphate (S1P), a bioactive lipid implicated in obesity and metabolic dysfunction. While global deletion of Sphk1 protects against diet-induced obesity, adipocyte-specific SPHK1 deficiency paradoxically promotes weight gain, glucose intolerance, and adipose inflammation. Given the known role of sphingolipids in adipose thermogenesis, we investigated whether Sphk1 regulates adipocyte beiging and mitochondrial function. MethodsWe assessed thermogenic responses in SphK1-deficient adipocytes and adipocyte-specific Sphk1 knockout (Ad-SphK1{Delta}) mice under basal and {beta}3-adrenergic stimulation using CL 316,243. Thermoneutral housing (30{degrees}C) and room temperature (23{degrees}C) conditions were used to minimize and assess ambient temperature effects on thermogenesis. Molecular, histological, and bioenergetic analyses were conducted across multiple adipose depots. Results{beta}3-adrenergic stimulation upregulated Sphk1 expression in mature white adipocytes, while SphK1-deficient adipocytes exhibited enhanced Ucp1 expression, indicating a suppressive role for SphK1 in beiging. In vivo, adipocyte-specific Sphk1 knockout (Ad-SphK1{Delta}) mice showed elevated Ucp1 expression in inguinal and gonadal white adipose tissue (iWAT, gWAT), both basally and after CL 316,243 treatment. These changes were accompanied by depot-specific alterations in adipocyte size and increased adiposity, independent of ambient temperature. Despite similar elevation of thermogenic markers, Sphk1 deletion had differential effect on mitochondrial function: iWAT showed increased mitochondrial content but reduced complex IV activity and ATP production, whereas gWAT showed reduced mitochondrial abundance without changes in respiration. ConclusionOur work suggests that Sphk1 may act as a negative regulator of thermogenic expression and affect mitochondrial function in a depot-specific manner. Loss of Sphk1 enhances beiging but compromises mitochondrial efficiency, revealing a complex role for the SphK1/S1P axis in adipose plasticity and metabolic regulation. These insights may inform future therapeutic strategies targeting sphingolipid pathways for obesity and metabolic disease.

biochemistry↗

bioRxiv2025

Circulating Lipids are Associated with PTSD Severity and Predict Symptomatic PTSD in a Cohort of Veterans and Service Members

Post-traumatic stress disorder (PTSD) is characterized by chronic stress, alterations in mood, and avoidance after a traumatic event has occurred. While recovery can occur, many PTSD patients suffer life-long impairments. In combat veterans, high rates of PTSD contribute to increased rates of depression and anxiety and a higher likelihood of suicidal ideation. The lack of biological markers for psychiatric conditions such as PTSD highlights the need for omics-based approaches to diagnosis. Discovery of novel blood-based biomarkers could aid in the development of treatments or therapies, quantify groups for those at the highest risk of adverse events, and provide insight into the molecular underpinnings of PTSD. This study used untargeted lipidomics to analyze 602 circulating lipid species in blood from a cohort of 133 veterans and combat members with varying severities of PTSD. We discovered five circulating lipids, including serum total cholesterol, cholesterol ether (ChE(18:2)), and lipids associated with metabolic dysfunction (cardiolipin : CL(87:7), monolysocardiolipin : MLCL(50:4), and phosphatidylethanolamine plasmalogen/ether lipid : PE(18:1e_20:3)) that correlated significantly with increasing PTSD severity after adjustment for multiple comparisons. Additionally, we showed that symptomatic PTSD patients could be separated from asymptomatic controls using these lipid species. This study contributes to the limited research surrounding the role of circulating lipids in PTSD.

neuroscience↗

bioRxiv2024

Adipocyte sphingosine kinase 1 regulates histone modifiers to disrupt circadian function

Circadian rhythms align biological functions with the 24-hour day-night cycle, but modern artificial light disrupts these patterns, contributing to health issues like obesity and cardiovascular disease. The circadian clock operates through a transcriptional-translational feedback loop involving core components such as BMAL1 and CLOCK. Recent research has shown circadian variations in sphingolipid metabolism, specifically sphingosine-1-phosphate (S1P), which plays crucial signaling roles. This study investigates the sphingolipid enzyme, sphingosine kinase 1 (SphK1), which converts sphingosine to S1P, as a circadian-regulated gene in adipocytes. We find that SphK1 expression and activity follow a circadian rhythm, regulated by BMAL1 and CLOCK binding to its promoter. Adipocyte-specific SphK1 knockout mice exhibit disrupted circadian rhythms, and impaired adipocyte function. Additionally, SphK1 deficiency leads to reduced histone acetylation and altered histone deacetylase (HDAC) localization, affecting gene regulation. These results highlight the critical role of SphK1 in linking lipid metabolism with circadian biology.

biochemistry↗

bioRxiv2024

Sphingosine kinase 1 is induced by glucocorticoids in adipose derived stem cells and enhances glucocorticoid mediated signaling in adipose expansion.

Sphingosine kinase 1 (SphK1) plays a crucial role in regulating metabolic pathways within adipocytes and is elevated in the adipose tissue of obese mice. While previous studies have reported both pro- and inhibitory effects of SphK1 and its product, sphingosine-1-phosphate (S1P), on adipogenesis, the precise mechanisms remain unclear. This study explores the timing and downstream effects of SphK1/S1P expression and activation during in vitro adipogenesis. We demonstrate that the synthetic glucocorticoid dexamethasone robustly induces SphK1 expression, suggesting its involvement in glucocorticoid-dependent signaling during adipogenesis. Notably, the activation of C/EBP{delta}, a key gene in early adipogenesis and a target of glucocorticoids, is diminished in SphK1-/- adipose-derived stem cells (ADSCs). Furthermore, glucocorticoid administration promotes adipose tissue expansion via SphK1 in a depot-specific manner. Although adipose expansion still occurs in SphK1-/- mice, it is significantly reduced. These findings indicate that while SphK1 is not essential for adipogenesis, it enhances early gene activation, thereby facilitating adipose tissue expansion.

biochemistry↗

bioRxiv2023

Farnesoid X receptor agonism prevents neutrophil extracellular traps via reduced sphingosine-1-phosphate in chronic kidney disease

BackgroundActivation of the farnesoid X receptor (FXR) reduces renal inflammation, but the underlying mechanisms remain elusive. Neutrophil extracellular traps (NETs) are webs of DNA formed when neutrophils undergo specialized programmed cell death (NETosis). Sphingosine-1-phosphate (S1P) is a signaling lipid that stimulates NETosis via its receptor on neutrophils. Here, we identify FXR as a negative regulator of kidney NETosis via repressing S1P signaling in male but not female mice. MethodsWe determined the effects of the FXR agonist obeticholic acid (OCA) in mouse models of adenosine phosphoribosyltransferase deficiency and Alport syndrome. We assessed renal NETosis by immunofluorescence in these models and in biopsies from patients with Alport syndrome (6 male, 9 female). We also inhibited de novo sphingosine production in Alport mice to show a causal relationship between S1P signaling and renal NETosis. ResultsRenal FXR activity is greatly reduced in both models, and OCA prevents kidney fibrosis, inflammation, and lipotoxicity. OCA reduces renal neutrophilic inflammation and NETosis in male adenine and Alport mice, but not in female adenine mice. Extensive NETosis was also identified in human Alport kidney biopsies. Kidney sphingosine kinase 1 (Sphk1) expression is increased in mice with kidney disease and reduced by OCA in male but not female mice. Also, Sphk1 expression correlates with NETosis in male but not female mice. Short-term inhibition of sphingosine synthesis reduces neutrophilic inflammation and NETosis. ConclusionFXR agonism represses kidney Sphk1 expression in male but not female mice. This inhibits renal S1P signaling, thereby reducing neutrophilic inflammation and NETosis in a sex-dependent manner.

pharmacology and toxicology↗

bioRxiv2022

Dynamic changes in the mouse hepatic lipidome following warm ischemia reperfusion injury

Liver failure secondary to nonalcoholic fatty liver disease (NAFLD) has become the most common cause for liver transplantation in many parts of the world. Moreover, the prevalence of NAFLD not only increases the demand for liver transplantation, but also limits the supply of suitable donor organs because steatosis predisposes grafts to ischemia-reperfusion injury (IRI). There are currently no pharmacological interventions to limit hepatic IR injury because the mechanisms by which steatosis leads to increased injury are unclear. To identify potential novel mediators of IR injury, we used liquid chromatography and mass spectrometry to assess temporal changes in the hepatic lipidome in steatotic and non-steatotic livers after warm IRI in mice. Our untargeted analyses revealed distinct differences between the steatotic and non-steatotic response to IRI and highlighted dynamic changes in lipid composition with marked changes in glycerolipids and glycerophospholipids. These findings enhance our knowledge of the lipidomic changes that occur following IRI and provide a foundation for future mechanistic studies. A better understanding of the mechanisms underlying such changes will lead to novel therapeutic strategies to combat IR injury.

biochemistry↗

bioRxiv2021

Apolipoprotein M attenuates doxorubicin cardiotoxicity by regulating transcription factor EB

ObjectivesDetermine the role of apolipoprotein M (ApoM) in anthracycline (Dox) cardiotoxicity. BackgroundApoM binds the cardioprotective sphingolipid sphingosine-1-phosphate (S1P). Circulating ApoM is inversely associated with mortality in human heart failure (HF). MethodsIn the Penn HF Study (PHFS), we tested the relationship between ApoM and mortality in a subset with anthracycline-induced cardiomyopathy. We measured ApoM in humans and mice treated with Dox and utilized hepatic ApoM transgenic (ApomTG), ApoM knockout (ApomKO), ApoM knock-in mice with impaired S1P binding, and S1P receptor 3 (S1PR3) knockout mice in Dox cardiotoxicity. We assayed autophagy in left ventricular tissue from anthracycline-induced HF patients versus donor controls. ResultsApoM was inversely associated with mortality in PHFS, and Dox reduced circulating ApoM in mice and breast cancer patients. ApomTG mice were protected from Dox-induced cardiac dysfunction and loss of left ventricular mass. ApomTG attenuated Dox-induced impairment in autophagic flux in vivo and accumulation of insoluble p62, which was also observed in the myocardium of patients with anthracycline-induced HF. In vehicle-treated mice, ApoM negatively regulated transcription factor EB (TFEB), a master regulator of autophagy and lysosomal biogenesis. The effect of ApoM on TFEB required both S1P binding and S1PR3. In the presence of Dox, ApoM preserved TFEB and cardiomyocyte lysosomal abundance assessed as lysosomal associated membrane protein 1 positive structures in vivo, while S1P mimetic pretreatment of cardiomyocytes prevented Dox-induced changes in lysosomal pH. ConclusionsApoM attenuates Dox cardiotoxicity via the autophagy-lysosome pathway. The association between ApoM and reduced mortality may be explained by its role in sustaining autophagy. HighlightsO_LICirculating ApoM is inversely associated with survival in human anthracycline-induced cardiomyopathy C_LIO_LIAnthracycline treatment reduces circulating ApoM in humans and mice C_LIO_LIIncreasing ApoM attenuates doxorubicin cardiotoxicity, lysosomal injury and preserves myocardial autophagic flux, but does not impact doxorubicin anti-neoplastic efficacy C_LIO_LIAutophagic impairment is characteristic of human anthracycline cardiomyopathy C_LI

pharmacology and toxicology↗