Mechanisms and disease consequences of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide. Its more advanced subtype, nonalcoholic steatohepatitis (NASH), connotes progressive liver injury that can lead to cirrhosis and hepatocellular carcinoma. Here we provide an in-depth discussion of the underlying pathogenetic mechanisms that lead to progressive liver injury, including the metabolic origins of NAFLD, the effect of NAFLD on hepatic glucose and lipid metabolism, bile acid toxicity, macrophage dysfunction, and hepatic stellate cell activation, and consider the role of genetic, epigenetic, and environmental factors that promote fibrosis progression and risk of hepatocellular carcinoma in NASH.

Neuron-Astrocyte Metabolic Coupling Protects against Activity-Induced Fatty Acid Toxicity.

Metabolic coordination between neurons and astrocytes is critical for the health of the brain. However, neuron-astrocyte coupling of lipid metabolism, particularly in response to neural activity, remains largely uncharacterized. Here, we demonstrate that toxic fatty acids (FAs) produced in hyperactive neurons are transferred to astrocytic lipid droplets by ApoE-positive lipid particles. Astrocytes consume the FAs stored in lipid droplets via mitochondrial ß-oxidation in response to neuronal activity and turn on a detoxification gene expression program. Our findings reveal that FA metabolism is coupled in neurons and astrocytes to protect neurons from FA toxicity during periods of enhanced activity. This coordinated mechanism for metabolizing FAs could underlie both homeostasis and a variety of disease states of the brain.

Ceramides are fuel gauges on the drive to cardiometabolic disease.

Ceramides are signals of fatty acid excess that accumulate when a cell's energetic needs have been met and its nutrient storage has reached capacity. As these sphingolipids accrue, they alter the metabolism and survival of cells throughout the body including in the heart, liver, blood vessels, skeletal muscle, brain, and kidney. These ceramide actions elicit the tissue dysfunction that underlies cardiometabolic diseases such as diabetes, coronary artery disease, metabolic-associated steatohepatitis, and heart failure. Here, we review the biosynthesis and degradation pathways that maintain ceramide levels in normal physiology and discuss how the loss of ceramide homeostasis drives cardiometabolic pathologies. We highlight signaling nodes that sense small changes in ceramides and in turn reprogram cellular metabolism and stimulate apoptosis. Finally, we evaluate the emerging therapeutic utility of these unique lipids as biomarkers that forecast disease risk and as targets of ceramide-lowering interventions that ameliorate disease.

Lipid metabolism in sickness and in health: Emerging regulators of lipotoxicity.

Lipids play crucial roles in signal transduction, contribute to the structural integrity of cellular membranes, and regulate energy metabolism. Questions remain as to which lipid species maintain metabolic homeostasis and which disrupt essential cellular functions, leading to metabolic disorders. Here, we discuss recent advances in understanding lipid metabolism with a focus on catabolism, synthesis, and signaling. Technical advances, including functional genomics, metabolomics, lipidomics, lipid-protein interaction maps, and advances in mass spectrometry, have uncovered new ways to prioritize molecular mechanisms mediating lipid function. By reviewing what is known about the distinct effects of specific lipid species in physiological pathways, we provide a framework for understanding newly identified targets regulating lipid homeostasis with implications for ameliorating metabolic diseases.

Obesity cardiomyopathy: evidence, mechanisms, and therapeutic implications.

The prevalence of heart failure is on the rise and imposes a major health threat, in part, due to the rapidly increased prevalence of overweight and obesity. To this point, epidemiological, clinical, and experimental evidence supports the existence of a unique disease entity termed "obesity cardiomyopathy," which develops independent of hypertension, coronary heart disease, and other heart diseases. Our contemporary review evaluates the evidence for this pathological condition, examines putative responsible mechanisms, and discusses therapeutic options for this disorder. Clinical findings have consolidated the presence of left ventricular dysfunction in obesity. Experimental investigations have uncovered pathophysiological changes in myocardial structure and function in genetically predisposed and diet-induced obesity. Indeed, contemporary evidence consolidates a wide array of cellular and molecular mechanisms underlying the etiology of obesity cardiomyopathy including adipose tissue dysfunction, systemic inflammation, metabolic disturbances (insulin resistance, abnormal glucose transport, spillover of free fatty acids, lipotoxicity, and amino acid derangement), altered intracellular especially mitochondrial Ca2+ homeostasis, oxidative stress, autophagy/mitophagy defect, myocardial fibrosis, dampened coronary flow reserve, coronary microvascular disease (microangiopathy), and endothelial impairment. Given the important role of obesity in the increased risk of heart failure, especially that with preserved systolic function and the recent rises in COVID-19-associated cardiovascular mortality, this review should provide compelling evidence for the presence of obesity cardiomyopathy, independent of various comorbid conditions, underlying mechanisms, and offer new insights into potential therapeutic approaches (pharmacological and lifestyle modification) for the clinical management of obesity cardiomyopathy.

Probing the Global Cellular Responses to Lipotoxicity Caused by Saturated Fatty Acids.

Excessive levels of saturated fatty acids are toxic to cells, although the basis for this lipotoxicity remains incompletely understood. Here, we analyzed the transcriptome, lipidome, and genetic interactions of human leukemia cells exposed to palmitate. Palmitate treatment increased saturated glycerolipids, accompanied by a transcriptional stress response, including upregulation of the endoplasmic reticulum (ER) stress response. A comprehensive genome-wide short hairpin RNA (shRNA) screen identified >350 genes modulating lipotoxicity. Among previously unknown genetic modifiers of lipotoxicity, depletion of RNF213, a putative ubiquitin ligase mutated in Moyamoya vascular disease, protected cells from lipotoxicity. On a broader level, integration of our comprehensive datasets revealed that changes in di-saturated glycerolipids, but not other lipid classes, are central to lipotoxicity in this model. Consistent with this, inhibition of ER-localized glycerol-3-phosphate acyltransferase activity protected from all aspects of lipotoxicity. Identification of genes modulating the response to saturated fatty acids may reveal novel therapeutic strategies for treating metabolic diseases linked to lipotoxicity.

Bridging lipid metabolism and mitochondrial genome maintenance.

Mitochondria are the nexus of cellular energy metabolism and major signaling hubs that integrate information from within and without the cell to implement cell function. Mitochondria harbor a distinct polyploid genome, mitochondrial DNA (mtDNA), that encodes respiratory chain components required for energy production. MtDNA mutation and depletion have been linked to obesity and metabolic syndrome in humans. At the cellular and subcellular levels, mtDNA synthesis is coordinated by membrane contact sites implicated in lipid transfer from the endoplasmic reticulum, tying genome maintenance to lipid storage and homeostasis. Here, we examine the relationship between mtDNA and lipid trafficking, the influence of lipotoxicity on mtDNA integrity, and how lipid metabolism may be disrupted in primary mtDNA disease.

SLC25A46 promotes mitochondrial fission and mediates resistance to lipotoxic stress in INS-1E insulin-secreting cells.

Glucose sensing in pancreatic ß-cells depends on oxidative phosphorylation and mitochondria-derived signals that promote insulin secretion. Using mass spectrometry-based phosphoproteomics to search for downstream effectors of glucose-dependent signal transduction in INS-1E insulinoma cells, we identified the outer mitochondrial membrane protein SLC25A46. Under resting glucose concentrations, SLC25A46 was phosphorylated on a pair of threonine residues (T44/T45) and was dephosphorylated in response to glucose-induced Ca2+ signals. Overexpression of SLC25A46 in INS-1E cells caused complete mitochondrial fragmentation, resulting in a mild mitochondrial defect associated with lowered glucose-induced insulin secretion. In contrast, inactivation of the Slc25a46 gene resulted in dramatic mitochondrial hyperfusion, without affecting respiratory activity or insulin secretion. Consequently, SLC25A46 is not essential for metabolism-secretion coupling under normal nutrient conditions. Importantly, insulin-secreting cells lacking SLC25A46 had an exacerbated sensitivity to lipotoxic conditions, undergoing massive apoptosis when exposed to palmitate. Therefore, in addition to its role in mitochondrial dynamics, SLC25A46 plays a role in preventing mitochondria-induced apoptosis in INS-E cells exposed to nutrient stress. By protecting mitochondria, SLC25A46 might help to maintain ß-cell mass essential for blood glucose control.

Ceramide analog C2-cer induces a loss in insulin sensitivity in muscle cells through the salvage/recycling pathway.

Ceramides have been shown to play a major role in the onset of skeletal muscle insulin resistance and therefore in the prevalence of type 2 diabetes. However, many of the studies involved in the discovery of deleterious ceramide actions used a nonphysiological, cell-permeable, short-chain ceramide analog, the C2-ceramide (C2-cer). In the present study, we determined how C2-cer promotes insulin resistance in muscle cells. We demonstrate that C2-cer enters the salvage/recycling pathway and becomes deacylated, yielding sphingosine, re-acylation of which depends on the availability of long chain fatty acids provided by the lipogenesis pathway in muscle cells. Importantly, we show these salvaged ceramides are actually responsible for the inhibition of insulin signaling induced by C2-cer. Interestingly, we also show that the exogenous and endogenous monounsaturated fatty acid oleate prevents C2-cer to be recycled into endogenous ceramide species in a diacylglycerol O-acyltransferase 1-dependent mechanism, which forces free fatty acid metabolism towards triacylglyceride production. Altogether, the study highlights for the first time that C2-cer induces a loss in insulin sensitivity through the salvage/recycling pathway in muscle cells. This study also validates C2-cer as a convenient tool to decipher mechanisms by which long-chain ceramides mediate insulin resistance in muscle cells and suggests that in addition to the de novo ceramide synthesis, recycling of ceramide could contribute to muscle insulin resistance observed in obesity and type 2 diabetes.

The mTORC1-G9a-H3K9me2 axis negatively regulates autophagy in fatty acid-induced hepatocellular lipotoxicity.

Defective autophagy and lipotoxicity are the hallmarks of nonalcoholic fatty liver disease. However, the precise molecular mechanism for the defective autophagy in lipotoxic conditions is not fully known. In the current study, we elucidated that activation of the mammalian target of rapamycin complex 1 (mTORC1)-G9a-H3K9me2 axis in fatty acid-induced lipotoxicity blocks autophagy by repressing key autophagy genes. The fatty acid-treated cells show mTORC1 activation, increased histone methyltransferase G9a levels, and suppressed autophagy as indicated by increased accumulation of the key autophagic cargo SQSTM1/p62 and decreased levels of autophagy-related proteins LC3II, Beclin1, and Atg7. Our chromatin immunoprecipitation analysis showed that decrease in autophagy was associated with increased levels of the G9a-mediated repressive H3K9me2 mark and decreased RNA polymerase II occupancy at the promoter regions of Beclin1 and Atg7 in fatty acid-treated cells. Inhibition of mTORC1 in fatty acid-treated cells decreased G9a-mediated H3K9me2 occupancy and increased polymerase II occupancy at Beclin1 and Atg7 promoters. Furthermore, mTORC1 inhibition increased the expression of Beclin1 and Atg7 in fatty acid-treated cells and decreased the accumulation of SQSTM1/p62. Interestingly, the pharmacological inhibition of G9a alone in fatty acid-treated cells decreased the H3K9me2 mark at Atg7 and Beclin1 promoters and restored the expression of Atg7 and Beclin1. Taken together, our findings have identified the mTORC1-G9a-H3K9me2 axis as a negative regulator of the autophagy pathway in hepatocellular lipotoxicity and suggest that the G9a-mediated epigenetic repression is mechanistically a key step during the repression of autophagy in lipotoxic conditions.

Amphipathic Liponecrosis Impairs Bacterial Clearance and Causes Infection During Sterile Inflammation.

BACKGROUND & AIMS: Although transient bacteremia is common during dental and endoscopic procedures, infections developing during sterile diseases like acute pancreatitis (AP) can have grave consequences. We examined how impaired bacterial clearance may cause this transition. METHODS: Blood samples from patients with AP, normal controls, and rodents with pancreatitis or those administered different nonesterified fatty acids (NEFAs) were analyzed for albumin-unbound NEFAs, microbiome, and inflammatory cell injury. Macrophage uptake of unbound NEFAs using a novel coumarin tracer were done and the downstream effects-NEFA-membrane phospholipid (phosphatidylcholine) interactions-were studied on isothermal titration calorimetry. RESULTS: Patients with infected AP had higher circulating unsaturated NEFAs; unbound NEFAs, including linoleic acid (LA) and oleic acid (OA); higher bacterial 16S DNA; mitochondrial DNA; altered ß-diversity; enrichment in Pseudomonadales; and increased annexin V-positive myeloid (CD14) and CD3-positive T cells on admission. These, and increased circulating dead inflammatory cells, were also noted in rodents with unbound, unsaturated NEFAs. Isothermal titration calorimetry showed progressively stronger unbound LA interactions with aqueous media, phosphatidylcholine, cardiolipin, and albumin. Unbound NEFAs were taken into protein-free membranes, cells, and mitochondria, inducing voltage-dependent anion channel oligomerization, reducing ATP, and impairing phagocytosis. These were reversed by albumin. In vivo, unbound LA and OA increased bacterial loads and impaired phagocytosis, causing infection. LA and OA were more potent for these amphipathic interactions than the hydrophobic palmitic acid. CONCLUSIONS: Release of stored LA and OA can increase their circulating unbound levels and cause amphipathic liponecrosis of immune cells via uptake by membrane phospholipids. This impairs bacterial clearance and causes infection during sterile inflammation.

MCT4-dependent lactate transport: a novel mechanism for cardiac energy metabolism injury and inflammation in type 2 diabetes mellitus.

Diabetic cardiomyopathy (DCM) is a major contributor to mortality in diabetic patients, characterized by a multifaceted pathogenesis and limited therapeutic options. While lactate, a byproduct of glycolysis, is known to be significantly elevated in type 2 diabetes, its specific role in DCM remains uncertain. This study reveals an abnormal upregulation of monocarboxylate transporter 4 (MCT4) on the plasma membrane of cardiomyocytes in type 2 diabetes, leading to excessive lactate efflux from these cells. The disruption in lactate transport homeostasis perturbs the intracellular lactate-pyruvate balance in cardiomyocytes, resulting in oxidative stress and inflammatory responses that exacerbate myocardial damage. Additionally, our findings suggest increased lactate efflux augments histone H4K12 lactylation in macrophages, facilitating inflammatory infiltration within the microenvironment. In vivo experiments have demonstrated that inhibiting MCT4 effectively alleviates myocardial oxidative stress and pathological damage, reduces inflammatory macrophage infiltration, and enhances cardiac function in type 2 diabetic mice. Furthermore, a clinical prediction model has been established, demonstrating a notable association between peripheral blood lactate levels and diastolic dysfunction in individuals with type 2 diabetes. This underscores the potential of lactate as a prognostic biomarker for DCM. Ultimately, our findings highlight the pivotal involvement of MCT4 in the dysregulation of cardiac energy metabolism and macrophage-mediated inflammation in type 2 diabetes. These insights offer novel perspectives on the pathogenesis of DCM and pave the way for the development of targeted therapeutic strategies against this debilitating condition.

Circ_005077 accelerates myocardial lipotoxicity induced by high-fat diet via CyPA/p47PHOX mediated ferroptosis.

The long-term high-fat diet (HFD) can cause myocardial lipotoxicity, which is characterized pathologically by myocardial hypertrophy, fibrosis, and remodeling and clinically by cardiac dysfunction and heart failure in patients with obesity and diabetes. Circular RNAs (circRNAs), a novel class of noncoding RNA characterized by a ring formation through covalent bonds, play a critical role in various cardiovascular diseases. However, few studies have been conducted to investigate the role and mechanism of circRNA in myocardial lipotoxicity. Here, we found that circ_005077, formed by exon 2-4 of Crmp1, was significantly upregulated in the myocardium of an HFD-fed rat. Furthermore, we identified circ_005077 as a novel ferroptosis-related regulator that plays a role in palmitic acid (PA) and HFD-induced myocardial lipotoxicity in vitro and in vivo. Mechanically, circ_005077 interacted with Cyclophilin A (CyPA) and inhibited its degradation via the ubiquitination proteasome system (UBS), thus promoting the interaction between CyPA and p47phox to enhance the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase responsible for ROS generation, subsequently inducing ferroptosis. Therefore, our results provide new insights into the mechanisms of myocardial lipotoxicity, potentially leading to the identification of a novel therapeutic target for the treatment of myocardial lipotoxicity in the future.

Luminal H2 O2 promotes ER Ca2+ dysregulation and toxicity of palmitate in insulin-secreting INS-1E cells.

The endoplasmic reticulum (ER) lumen is not only the major site for the assembly and folding of newly synthesized proteins but also the main intracellular Ca2+ store. Ca2+ ions are involved in versatile biochemical processes, including posttranslational processing and folding of nascent proteins. Disruption of ER Ca2+ homeostasis is usually accompanied by an ER stress response that can ultimately lead to apoptosis if unresolved. Abnormal ER Ca2+ depletion has been linked to pancreatic ß-cell dysfunction and death under lipotoxic conditions. However, the underlying mechanisms how the ß-cell toxic saturated free fatty acid palmitate perturbs ER Ca2+ homeostasis and its interplay with other organelles are not fully understood. In the present study, we demonstrate that treatment of insulin-secreting INS-1E cells with palmitate diminished ER Ca2+ levels, elevated cytosolic/mitochondrial Ca2+ content, lowered the mitochondrial membrane potential, and ATP content. In addition, palmitate-pretreated ß-cells contained significantly less luminal Ca2+ , revealed a severely impaired ER Ca2+ reuptake rate, and substantially lower insulin content. Importantly, detoxification of luminal H2 O2 by expression of the ER-resident glutathione peroxidase 8 (GPx8) abrogated the lipotoxic effects of palmitate. Moreover, GPx8 supported oxidative protein folding and preserved insulin content under lipotoxic conditions. A direct involvement of luminal H2 O2 in palmitate-mediated ER Ca2+ depletion could be corroborated by the ectopic expression of an ER-luminal active catalase. Our data point to the critical role of luminal H2 O2 in palmitate-mediated depletion of ER Ca2+ through redox-dependent impairment of Ca2+ ATPase pump activity upstream of mitochondrial dysfunction in insulin-secreting INS-1E cells.

Fish oil minimises feed intake and improves insulin sensitivity in Zucker fa/fa rats.

Long-chain n-3 PUFA (LC n-3 PUFA) prevent, in rodents, insulin resistance (IR) induced by a high-fat and/or fructose diet but not IR induced by glucocorticoids. In humans, contrasting effects have also been reported. We investigated their effects on insulin sensitivity, feed intake (FI) and body weight gain in genetically insulin resistant male obese (fa/fa) Zucker (ZO) rats during the development of obesity. ZO rats were fed a diet supplemented with 7 % fish oil (FO) + 1 % corn oil (CO) (wt/wt) (ZOFO), while the control group was fed a diet containing 8 % fat from CO (wt/wt) (ZOCO). Male lean Zucker (ZL) rats fed either FO (ZLFO) or CO (ZLCO) diet were used as controls. FO was a marine-derived TAG oil containing EPA 90 mg/g + DHA 430 mg/g. During an oral glucose tolerance test, glucose tolerance remained unaltered by FO while insulin response was reduced in ZOFO only. Liver insulin sensitivity (euglycaemic-hyperinsulinaemic clamp + 2 deoxyglucose) was improved in ZOFO rats, linked to changes in phosphoenolpyruvate carboxykinase expression, activity and glucose-6-phosphatase activity. FI in response to intra-carotid insulin/glucose infusion was decreased similarly in ZOFO and ZOCO. Hypothalamic ceramides levels were lower in ZOFO than in ZOCO. Our study demonstrates that LC n-3 PUFA can minimise weight gain, possibly by alleviating hypothalamic lipotoxicity, and liver IR in genetically obese Zucker rats.

Oleic acid improves hepatic lipotoxicity injury by alleviating autophagy dysfunction.

Lipotoxicity caused by excess free fatty acids, particularly saturated fatty acids (SFAs) such as palmitic acid (PA), is one of the most important pathogenesis of nonalcoholic fatty liver disease (NAFLD). However, unsaturated fatty acids (UFAs), such as oleic acid (OA), are nontoxic and can combat SFA-induced toxicity through alleviation of cell apoptosis, endoplasmic reticulum stress (ER stress) and lipids metabolism disorder. However, whether OA is able to regulate autophagy is largely unknown. So, this study aims to investigate the mechanism underlying OA mediated modulation of autophagy in hepatocytes and mice with NAFLD. In vitro, human hepatoma cell line HepG2 cells, human normal liver cells L-02 and mouse normal liver cells AML12 were treated with palmitic acid (PA)/tunicamycin (TM) or/and OA for 48 h. In vivo, C57/BL6 mice were fed with high fat diet (HFD) to induce NAFLD. And the HFD was partial replaced by olive oil to observe the protective effects of olive oil. We demonstrated that PA/TM impaired cell viability and induced cellular apoptosis in HepG2 cells and L-02 cells. Moreover, PA/TM induced autophagy impairment by reducing the nuclear translocation of transcription factor EB (TFEB) and inhibiting the activity of CTSB. However, OA substantially alleviated PA/TM induced cellular apoptosis and autophagy dysfunction in hepatocytes. Additionally, restoring autophagy function is able to reduce ER stress. Similarly, HFD for 20 weeks successfully established NAFLD model in C57/BL6 mice, and significant autophagy impairment were observed in liver tissues. Noteworthily, 30% replacement of HFD with olive oil had profoundly reversed NAFLD. It significantly impoved steatosis, and reduced autophagy dysfunction, ER stress and apoptosis in liver tissue. Conclusively, these data demonstrated that OA is able to effectively impove autophagy dysfunction under the context of both PA and ER stress inducer induced lipotoxicity, and OA mediated regulation of lysosome dysfunction through TFEB plays an important role, suggesting that the regulation of ER stress-autophagy axis is a critical mechanism in OA driven protection in NAFLD.

Lipotoxicity as a therapeutic target in obesity and diabetic cardiomyopathy.

Unhealthy sources of fats, ultra-processed foods with added sugars, and a sedentary lifestyle make humans more susceptible to developing overweight and obesity. While lipids constitute an integral component of the organism, excessive and abnormal lipid accumulation that exceeds the storage capacity of lipid droplets disrupts the intracellular composition of fatty acids and results in the release of deleterious lipid species, thereby giving rise to a pathological state termed lipotoxicity. This condition induces endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory responses, and cell death. Recent advances in omics technologies and analytical methodologies and clinical research have provided novel insights into the mechanisms of lipotoxicity, including gut dysbiosis, epigenetic and epitranscriptomic modifications, dysfunction of lipid droplets, post-translational modifications, and altered membrane lipid composition. In this review, we discuss the recent knowledge on the mechanisms underlying the development of lipotoxicity and lipotoxic cardiometabolic disease in obesity, with a particular focus on lipotoxic and diabetic cardiomyopathy.

Updated mechanisms of MASLD pathogenesis.

Metabolic dysfunction-associated steatotic liver disease (MASLD) has garnered considerable attention globally. Changing lifestyles, over-nutrition, and physical inactivity have promoted its development. MASLD is typically accompanied by obesity and is strongly linked to metabolic syndromes. Given that MASLD prevalence is on the rise, there is an urgent need to elucidate its pathogenesis. Hepatic lipid accumulation generally triggers lipotoxicity and induces MASLD or progress to metabolic dysfunction-associated steatohepatitis (MASH) by mediating endoplasmic reticulum stress, oxidative stress, organelle dysfunction, and ferroptosis. Recently, significant attention has been directed towards exploring the role of gut microbial dysbiosis in the development of MASLD, offering a novel therapeutic target for MASLD. Considering that there are no recognized pharmacological therapies due to the diversity of mechanisms involved in MASLD and the difficulty associated with undertaking clinical trials, potential targets in MASLD remain elusive. Thus, this article aimed to summarize and evaluate the prominent roles of lipotoxicity, ferroptosis, and gut microbes in the development of MASLD and the mechanisms underlying their effects. Furthermore, existing advances and challenges in the treatment of MASLD were outlined.

Effects of Low-Intensity Pulsed Ultrasound on the Regulation of Free Fatty Acid Release in 3T3-L1 Cells.

OBJECTIVES: To investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the proliferation, differentiation, and tumor necrosis factor-α (TNF-α)-induced lipolysis of 3T3-L1 cells, and to explore the feasibility of regulating the release of free fatty acids (FFA) to prevent lipotoxicity. METHODS: Different intensities (30, 60, 90, and 120 mW/cm2) of LIPUS were applied to 3T3-L1 preadipocytes for different durations (5, 10, 15, 20, 25, and 30 minutes). Appropriate parameters for subsequent experiments were selected by assessing cell viability. The effect of LIPUS on the proliferation and differentiation of 3T3-L1 cells was evaluated by microscope observation, flow cytometry, and lipid content determination. After treated with LIPUS and TNF-α (50 ng/mL), the degree of lipolysis was assessed by measuring the extracellular FFA content. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the mRNA expression of relevant genes. RESULTS: Different parameters of LIPUS significantly enhance the viability of 3T3-L1 cells (P < .05), with 20 minutes and 30 mW/cm2 as the most suitable settings. After LIPUS treatment, 3T3-L1 cell proliferation accelerated, apoptosis rate and G1 phase cell proportion decreased, the content of lipid droplets and TG was increased in differentiated cells, while FFA release decreased (P < .05). The expression of PCNA, PPARγ, C/EBPα, Perilipin A mRNA increased, and the expression of TNF-α, ATGL, HSL mRNA decreased (P < .05). CONCLUSIONS: LIPUS could promote the proliferation and differentiation of 3T3-L1 cells and inhibit TNF-α-induced lipolysis, indicating its potential as a therapy for mitigating lipotoxicity caused by decompensated adipocytes.

Bioinformatic analyses reveal lysosomal-associated protein transmembrane 5 as a potential therapeutic target in lipotoxicity-induced injury in diabetic kidney disease.

Emerging data have revealed that damage to tubular epithelial cell is a driving force in the progression of diabetic kidney disease (DKD). However, the specific mechanisms by which lipotoxicity contributes to the injury of these cells, thereby influencing the development of DKD, are yet to be fully understood. Here, we analyzed the GSE 30529 microarray datasets of human tubulointerstitial tissue samples from the Gene Expression Omnibus database (GEO). Concurrently, we conducted RNA-sequencing on palmitic acid (PA)-treated human renal proximal tubule epithelial cells (HK2 cells). After normalization, the differentially expressed genes (DEGs) were screened by R software and gene ontology (GO) enrichment analysis was conducted, and lysosomal-associated protein transmembrane 5 (LAPTM5) was finally selected. Our findings indicate that the expression of LAPTM5 was obviously increased in DKD patients, and the correlation between LAPTM5, and other clinical parameters of DKD was analyzed using the Spearman correlation analysis. The potential of LAPTM5 as a prognostic biomarker for DKD was further consolidated through receiver operating characteristic (ROC) analysis. To further verify the function of LAPTM5, we established mouse or in vitro systems mimicking DKD. The results showed that a consistent upregulation of LAPTM5, which was also found to be linked with inflammatory mediators within the context of DKD. Additionally, LAPTM5 silencing significantly downregulated mRNA expression of inflammatory factors in PA-treated HK2 cells. These results indicate that LAPTM5 is a potential biomarker and therapeutic treatment target for DKD. This discovery paves the way for future research and development of targeted interventions aimed at mitigating the progression of this prevalent condition.