Molecular Mechanism of Lipotoxicity as an Interesting Aspect in the Development of Pathological States-Current View of Knowledge

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.

The role of perirenal adipose tissue deposition in chronic kidney disease progression: Mechanisms and therapeutic implications

Chronic kidney disease (CKD) represents a significant and escalating global health challenge, with morbidity and mortality rates rising steadily. Evidence increasingly implicates perirenal adipose tissue (PRAT) deposition as a contributing factor in the pathogenesis of CKD. This review explores how PRAT deposition may exert deleterious effects on renal structure and function. The anatomical proximity of PRAT to the kidneys not only potentially causes mechanical compression but also leads to the dysregulated secretion of adipokines and inflammatory mediators, such as adiponectin, leptin, visfatin, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and exosomes. Additionally, PRAT deposition may contribute to renal lipotoxicity through elevated levels of free fatty acids (FFA), triglycerides (TAG), diacylglycerol (DAG), and ceramides (Cer). PRAT deposition is also linked to the hyperactivation of the renin-angiotensin-aldosterone system (RAAS), which further exacerbates CKD progression. Recognizing PRAT deposition as an independent risk factor for CKD underscores the potential of targeting PRAT as a novel strategy for the prevention and management of CKD. This review further discusses interventions that could include measuring PRAT thickness to establish a baseline, managing metabolic risk factors that promote its deposition, and inhibiting key PRAT-induced signaling pathways.

Obesity, dyslipidemia, and cardiovascular disease: A joint expert review from the Obesity Medicine Association and the National Lipid Association 2024

Background

This joint expert review by the Obesity Medicine Association (OMA) and National Lipid Association (NLA) provides clinicians an overview of the pathophysiologic and clinical considerations regarding obesity, dyslipidemia, and cardiovascular disease (CVD) risk.

Methods

This joint expert review is based upon scientific evidence, clinical perspectives of the authors, and peer review by the OMA and NLA leadership.

Results

Among individuals with obesity, adipose tissue may store over 50% of the total body free cholesterol. Triglycerides may represent up to 99% of lipid species in adipose tissue. The potential for adipose tissue expansion accounts for the greatest weight variance among most individuals, with percent body fat ranging from less than 5% to over 60%. While population studies suggest a modest increase in blood low-density lipoprotein cholesterol (LDL-C) levels with excess adiposity, the adiposopathic dyslipidemia pattern most often described with an increase in adiposity includes elevated triglycerides, reduced high density lipoprotein cholesterol (HDL-C), increased non-HDL-C, elevated apolipoprotein B, increased LDL particle concentration, and increased small, dense LDL particles.

Conclusions

Obesity increases CVD risk, at least partially due to promotion of an adiposopathic, atherogenic lipid profile. Obesity also worsens other cardiometabolic risk factors. Among patients with obesity, interventions that reduce body weight and improve CVD outcomes are generally associated with improved lipid levels. Given the modest improvement in blood LDL-C with weight reduction in patients with overweight or obesity, early interventions to treat both excess adiposity and elevated atherogenic cholesterol (LDL-C and/or non-HDL-C) levels represent priorities in reducing the risk of CVD.

Pathogenesis of MASLD and MASH - role of insulin resistance and lipotoxicity

BACKGROUND

Insulin resistance and lipotoxicity are extremely interconnected but fundamental in setting the stage for the development of MASLD/MASH.

AIM/METHODS

A comprehensive literature search was performed and key themes were synthesised to provide insight into the underlying molecular mechanisms of insulin resistance and lipotoxicity in the liver, muscle, pancreas and adipose tissue and how organ cross-talk is fundamental to driving disease pathogenesis.

RESULTS

Classical thinking postulates that excess FFA load exceeds the storage capacity of adipose tissue, which is predicated upon both genetic and environmental factors. This results in insulin resistance and compensatory hyperinsulinaemia by pancreatic beta cells to overcome target organ insulin resistance. As adipocyte dysfunction worsens, not only are excess FFA delivered to other organs, including skeletal muscle, pancreas and liver but a pro-inflammatory milieu is established with increases in IL-6, TNF-α and changes in adipokine levels (increased leptin and decreased adiponectin). With increased intramuscular lipid accumulation, lipotoxic species decrease insulin signalling, reduce glucose uptake by downregulation of GLUT4 and decrease glycogen synthesis. With this additional reduced capacity, hyperglycaemia is further exacerbated and increased FFA are delivered to the liver. The liver has the largest capacity to oxidise fat and to adapt to these stressors and, therefore, has become the last line of defence for excess lipid storage and utilisation, the capacity of which may be impacted by genetic and environmental factors. However, when the liver can no longer keep up with increasing FFA delivery and DNL, lipotoxic species accumulate with ensuing mitochondrial dysfunction, increased ER stress, oxidant stress and inflammasome activation, all of which drive hepatocyte injury and apoptosis. The resulting wound healing response, marked by stellate cell activation, drives collagen accumulation, progressive fibrosis, and, ultimately, end organ failure and death. This vicious cycle and complex interplay between insulin resistance, hyperinsulinaemia, lipotoxicity and multi-directional cross-talk among different target organs are critical drivers of MASLD/MASH.

CONCLUSIONS

Targeting tissue-specific insulin resistance and hyperinsulinaemia while decreasing FFA load (lipotoxicity) through dietary and lifestyle changes remain the best upstream interventions.

Positive Effects of Physical Activity on Insulin Signaling

Physical activity is integral to metabolic health, particularly in addressing insulin resistance and related disorders such as type 2 diabetes mellitus (T2DM). Studies consistently demonstrate a strong association between physical activity levels and insulin sensitivity. Regular exercise interventions were shown to significantly improve glycemic control, highlighting exercise as a recommended therapeutic strategy for reducing insulin resistance. Physical inactivity is closely linked to islet cell insufficiency, exacerbating insulin resistance through various pathways including ER stress, mitochondrial dysfunction, oxidative stress, and inflammation. Conversely, physical training and exercise preserve and restore islet function, enhancing peripheral insulin sensitivity. Exercise interventions stimulate β-cell proliferation through increased circulating levels of growth factors, further emphasizing its role in maintaining pancreatic health and glucose metabolism. Furthermore, sedentary lifestyles contribute to elevated oxidative stress levels and ceramide production, impairing insulin signaling and glucose metabolism. Regular exercise induces anti-inflammatory responses, enhances antioxidant defenses, and promotes mitochondrial function, thereby improving insulin sensitivity and metabolic efficiency. Encouraging individuals to adopt active lifestyles and engage in regular exercise is crucial for preventing and managing insulin resistance and related metabolic disorders, ultimately promoting overall health and well-being.

Overnutrition and Lipotoxicity: Impaired Efferocytosis and Chronic Inflammation as Precursors to Multifaceted Disease Pathogenesis

Overnutrition, driven by the consumption of high-fat, high-sugar diets, has reached epidemic proportions and poses a significant global health challenge. Prolonged overnutrition leads to the deposition of excessive lipids in adipose and non-adipose tissues, a condition known as lipotoxicity. The intricate interplay between overnutrition-induced lipotoxicity and the immune system plays a pivotal role in the pathogenesis of various diseases. This review aims to elucidate the consequences of impaired efferocytosis, caused by lipotoxicity-poisoned macrophages, leading to chronic inflammation and the subsequent development of severe infectious diseases, autoimmunity, and cancer, as well as chronic pulmonary and cardiovascular diseases. Chronic overnutrition promotes adipose tissue expansion which induces cellular stress and inflammatory responses, contributing to insulin resistance, dyslipidemia, and metabolic syndrome. Moreover, sustained exposure to lipotoxicity impairs the efferocytic capacity of macrophages, compromising their ability to efficiently engulf and remove dead cells. The unresolved chronic inflammation perpetuates a pro-inflammatory microenvironment, exacerbating tissue damage and promoting the development of various diseases. The interaction between overnutrition, lipotoxicity, and impaired efferocytosis highlights a critical pathway through which chronic inflammation emerges, facilitating the development of severe infectious diseases, autoimmunity, cancer, and chronic pulmonary and cardiovascular diseases. Understanding these intricate connections sheds light on potential therapeutic avenues to mitigate the detrimental effects of overnutrition and lipotoxicity on immune function and tissue homeostasis, thereby paving the way for novel interventions aimed at reducing the burden of these multifaceted diseases on global health.

Untargeted and temporal analysis of retinal lipidome in bacterial endophthalmitis

Bacterial endophthalmitis is a blinding infectious disease typically acquired during ocular surgery. We previously reported significant alterations in retinal metabolism during Staphylococcus (S) aureus endophthalmitis. However, the changes in retinal lipid composition during endophthalmitis are unknown. Here, using a mouse model of S. aureus endophthalmitis and an untargeted lipidomic approach, we comprehensively analyzed temporal alterations in total lipids and oxylipin in retina. Our data showed a time-dependent increase in the levels of lipid classes, sphingolipids, glycerolipids, sterols, and non-esterified fatty acids, whereas levels of phospholipids decreased. Among lipid subclasses, phosphatidylcholine decreased over time. The oxylipin analysis revealed increased prostaglandin-E2, hydroxyeicosatetraenoic acids, docosahexaenoic acid, eicosapentaenoic acid, and α-linolenic acid. In-vitro studies using mouse bone marrow-derived macrophages showed increased lipid droplets and lipid-peroxide formation in response to S. aureus infection. Collectively, these findings suggest that S. aureus-infection alters the retinal lipid profile, which may contribute to the pathogenesis of bacterial endophthalmitis.

Lipidome Changes Associated with a Diet-Induced Reduction in Hepatic Fat among Adolescent Boys with Metabolic Dysfunction-Associated Steatotic Liver Disease

Little is known about lipid changes that occur in the setting of metabolic-dysfunction-associated steatotic liver disease (MASLD) regression. We previously reported improvements in hepatic steatosis, de novo lipogenesis (DNL), and metabolomic profiles associated with oxidative stress, inflammation, and selected lipid metabolism in 40 adolescent boys (11-16 y) with hepatic steatosis ≥5% (98% meeting the definition of MASLD). Participants were randomized to a low-free-sugar diet (LFSD) (n = 20) or usual diet (n = 20) for 8 weeks. Here, we employed untargeted/targeted lipidomics to examine lipid adaptations associated with the LFSD and improvement of hepatic steatosis. Our LC-MS/MS analysis revealed decreased triglycerides (TGs), diacylglycerols (DGs), cholesteryl esters (ChE), lysophosphatidylcholine (LPC), and phosphatidylcholine (PC) species with the diet intervention (p < 0.05). Network analysis demonstrated significantly lower levels of palmitate-enriched TG species post-intervention, mirroring the previously shown reduction in DNL in response to the LFSD. Targeted oxylipins analysis revealed a decrease in the abundance of 8-isoprostane and 14,15-DiHET and an increase in 8,9-DiHET (p < 0.05). Overall, we observed reductions in TGs, DGs, ChE, PC, and LPC species among participants in the LFSD group. These same lipids have been associated with MASLD progression; therefore, our findings may indicate normalization of key biological processes, including lipid metabolism, insulin resistance, and lipotoxicity. Additionally, our targeted oxylipins assay revealed novel changes in eicosanoids, suggesting improvements in oxidative stress. Future studies are needed to elucidate the mechanisms of these findings and prospects of these lipids as biomarkers of MASLD regression.

SIRT1 activation attenuates palmitate induced apoptosis in C2C12 muscle cells

BACKGROUND

Type 2 diabetes is characterized by insulin resistance, which manifests mainly in skeletal muscles. SIRT1 has been found to play a role in the insulin signaling pathway. However, the molecular underpinnings of SIRT1's function in palmitate fatty acid-induced apoptosis still need to be better understood.

METHODS

In this research, skeletal muscle cells are treated with palmitate to be insulin resistant. It is approached that SIRT1 is downregulated in C2C12 muscle cells during palmitate-induced apoptosis and that activating SIRT1 mitigates this effect.

RESULTS

Based on these findings, palmitate-induced apoptosis suppressed mitochondrial biogenesis by lowering PGC-1 expression, while SIRT1 overexpression boosted. The SIRT1 inhibitor sirtinol, on the other hand, decreased mitochondrial biogenesis under the same conditions. This research also shows that ROS levels rise in the conditions necessary for apoptosis induction by palmitate, and ROS inhibitors can mitigate this effect. This work demonstrated that lowering ROS levels by boosting SIRT1 expression inhibited apoptotic induction in skeletal muscle cells.

CONCLUSION

This study's findings suggested that SIRT1 can improve insulin resistance in type 2 diabetes by slowing the rate of lipo-apoptosis and boosting mitochondrial biogenesis, among other benefits.

Lipotoxicity-polarised macrophage-derived exosomes regulate mitochondrial fitness through Miro1-mediated mitophagy inhibition and contribute to type 2 diabetes development in mice

AIMS/HYPOTHESIS

Insulin resistance is a major pathophysiological defect in type 2 diabetes and obesity. Numerous experimental and clinical studies have provided evidence that sustained lipotoxicity-induced mitophagy deficiency can exacerbate insulin resistance, leading to a vicious cycle between mitophagy dysfunction and insulin resistance, and thereby the onset of type 2 diabetes. Emerging evidence suggests that exosomes (Exos) from M2 macrophages play an essential role in modulating metabolic homeostasis. However, how macrophages are affected by lipotoxicity and the role of lipotoxicity in promoting macrophage activation to the M1 state have not been determined. The objective of this study was to determine whether M1 macrophage-derived Exos polarised by lipopolysaccharide (LPS) + palmitic acid (PA)-induced lipotoxicity contribute to metabolic homeostasis and impact the development of insulin resistance in type 2 diabetes.

METHODS

Lipotoxicity-polarised macrophage-derived M1 Exos were isolated from bone marrow (C57BL/6J mouse)-derived macrophages treated with LPS+PA. Exos were characterised by transmission electron microscopy, nanoparticle tracking analysis and western blotting. Flow cytometry, H&E staining, quantitative real-time PCR, immunofluorescence, glucose uptake and output assays, confocal microscopy imaging, western blotting, GTTs and ITTs were conducted to investigate tissue inflammation, mitochondrial function and insulin resistance in vitro and in vivo. The roles of miR-27-3p and its target gene Miro1 (also known as Rhot1, encoding mitochondrial rho GTPase 1) and relevant pathways were predicted and assessed in vitro and in vivo using specific miRNA mimic, miRNA inhibitor, miRNA antagomir and siRNA.

RESULTS

miR-27-3p was highly expressed in M1 Exos and functioned as a Miro1-inactivating miRNA through the miR-27-3p-Miro1 axis, leading to mitochondria fission rather than fusion as well as mitophagy impairment, resulting in NOD-like receptor 3 inflammatory activation and development of insulin resistance both in vivo and in vitro. Inactivation of miR-27-3p induced by M1 Exos prevented type 2 diabetes development in high-fat-diet-fed mice.

CONCLUSIONS/INTERPRETATION

These findings suggest that the miR-27-3p-Miro1 axis, as a novel regulatory mechanism for mitophagy, could be considered as a new therapeutic target for lipotoxicity-related type 2 diabetes disease development.

The Coumarin-Derivative Esculetin Protects against Lipotoxicity in Primary Rat Hepatocytes via Attenuating JNK-Mediated Oxidative Stress and Attenuates Free Fatty Acid-Induced Lipid Accumulation

Coumarin derivates have been proposed as a potential treatment for metabolic-dysfunction-associated fatty liver disease (MAFLD). However, the mechanisms underlying their beneficial effects remain unclear. In the present study, we explored the potential of the coumarin derivate esculetin in MAFLD, focusing on hepatocyte lipotoxicity and lipid accumulation. Primary cultures of rat hepatocytes were exposed to palmitic acid (PA) and palmitic acid plus oleic acid (OA/PA) as models of lipotoxicity and lipid accumulation, respectively. Esculetin significantly reduced oxidative stress in PA-treated hepatocytes, as shown by decreased total reactive oxygen species (ROS) and mitochondrial superoxide production and elevated expression of antioxidant genes, including Nrf2 and Gpx1. In addition, esculetin protects against PA-induced necrosis. Esculetin also improved lipid metabolism in primary hepatocytes exposed to nonlipotoxic OA/PA by decreasing the expression of the lipogenesis-related gene Srebp1c and increasing the expression of the fatty acid β-oxidation-related gene Ppar-α. Moreover, esculetin attenuated lipid accumulation in OA/PA-treated hepatocytes. The protective effects of esculetin against lipotoxicity and lipid accumulation were shown to be dependent on the inhibition of JNK and the activation of AMPK, respectively. We conclude that esculetin is a promising compound to target lipotoxicity and lipid accumulation in the treatment of MAFLD.

Rapid and sensitive determination of free fatty acids based on in-source microdroplet-driven derivatization coupled with high-resolution mass spectrometry

Accurate and sensitive measurements of free fatty acids (FFAs) in biological samples are valuable for diagnosing and prognosing diseases. In this study, an in-source microdroplet derivation strategy combined with high-resolution mass spectrometry was developed to analyze FFAs in lipid extracts of biological samples directly. FFAs were rapidly derivated with 2-picolylamine (PA) in the microdroplet which is derived by electrospray. With the proposed method, twelve typical FFAs were determined reliably with high sensitivity and acceptable linearities (R2 ≥ 0.94). The LODs and LOQs for the twelve FFAs were 9-76 pg mL-1 and 30-253 pg mL-1, respectively. The developed method was applied to analyze the alteration of FFAs in liver and kidney samples of rats induced by perfluorooctane sulfonate (PFOS) exposure. The good results demonstrate that the established analysis technique is dependable and has promising applications in detecting FFAs associated with complex biological samples.

CD38 Inhibition Protects Fructose-Induced Toxicity in Primary Hepatocytes

A fructose-enriched diet is thought to contribute to hepatic injury in developing non-alcoholic steatohepatitis (NASH). However, the cellular mechanism of fructose-induced hepatic damage remains poorly understood. This study aimed to determine whether fructose induces cell death in primary hepatocytes, and if so, to establish the underlying cellular mechanisms. Our results revealed that treatment with high fructose concentrations for 48 h induced mitochondria-mediated apoptotic death in mouse primary hepatocytes (MPHs). Endoplasmic reticulum stress responses were involved in fructose-induced death as the levels of phosho-eIF2α, phospho-C-Jun-N-terminal kinase (JNK), and C/EBP homologous protein (CHOP) increased, and a chemical chaperone tauroursodeoxycholic acid (TUDCA) prevented cell death. The impaired oxidation metabolism of fatty acids was also possibly involved in the fructose-induced toxicity as treatment with an AMP-activated kinase (AMPK) activator and a PPAR-α agonist significantly protected against fructose-induced death, while carnitine palmitoyl transferase I inhibitor exacerbated the toxicity. However, uric acid-mediated toxicity was not involved in fructose-induced death as uric acid was not toxic to MPHs, and the inhibition of xanthine oxidase (a key enzyme in uric acid synthesis) did not affect cell death. On the other hand, treatment with inhibitors of the nicotinamide adenine dinucleotide (NAD)+-consuming enzyme CD38 or CD38 gene knockdown significantly protected against fructose-induced toxicity in MPHs, and fructose treatment increased CD38 levels. These data suggest that CD38 upregulation plays a role in hepatic injury in the fructose-enriched diet-mediated NASH. Thus, CD38 inhibition may be a promising therapeutic strategy to prevent fructose-enriched diet-mediated NASH.

DHA-Provoked Reduction in Adipogenesis and Glucose Uptake Could Be Mediated by Gps2 Upregulation in Immature 3T3-L1 Cells

The signaling pathway of fatty acids in the context of obesity is an extensively explored topic, yet their primary mechanism of action remains incompletely understood. This study aims to examine the effect of docosahexaenoic acid (DHA) on some crucial aspects of adipogenesis in differentiating 3T3-L1 cells, using palmitic acid-treated (PA), standard differentiated, and undifferentiated adipocytes as controls. Employing 60 µM DHA or PA, 3T3-L1 preadipocytes were treated from the onset of adipogenesis, with negative and positive controls included. After eight days, we performed microscopic observations, cell viability assays, the determination of adiponectin concentration, intracellular lipid accumulation, and gene expression analysis. Our findings demonstrated that DHA inhibits adipogenesis, lipolysis, and glucose uptake by suppressing peroxisome proliferator-activated receptor gamma (Pparg) and G-protein coupled receptor 120 (Gpr120) gene expression. Cell cytotoxicity was ruled out as a causative factor, and β-oxidation involvement was suspected. These results challenge the conventional belief that omega-3 fatty acids, acting as Pparg and Gpr120 agonists, promote adipogenesis and enhance insulin-dependent glucose cell flux. Moreover, we propose a novel hypothesis suggesting the key role of the co-repressor G protein pathway suppressor 2 in mediating this process. Additional investigations are required to elucidate the molecular mechanisms driving DHA's anti-adipogenic effect and its broader health implications.

Circulating Sphingolipids and Glucose Homeostasis: An Update

Sphingolipids are a family of lipid molecules produced through different pathways in mammals. Sphingolipids are structural components of membranes, but in response to obesity, they are implicated in the regulation of various cellular processes, including inflammation, apoptosis, cell proliferation, autophagy, and insulin resistance which favors dysregulation of glucose metabolism. Of all sphingolipids, two species, ceramides and sphingosine-1-phosphate (S1P), are also found abundantly secreted into the bloodstream and associated with lipoproteins or extracellular vesicles. Plasma concentrations of these sphingolipids can be altered upon metabolic disorders and could serve as predictive biomarkers of these diseases. Recent important advances suggest that circulating sphingolipids not only serve as biomarkers but could also serve as mediators in the dysregulation of glucose homeostasis. In this review, advances of molecular mechanisms involved in the regulation of ceramides and S1P association to lipoproteins or extracellular vesicles and how they could alter glucose metabolism are discussed.

Lipid oxidation dysregulation: an emerging player in the pathophysiology of sepsis

Sepsis is a life-threatening organ dysfunction caused by abnormal host response to infection. Millions of people are affected annually worldwide. Derangement of the inflammatory response is crucial in sepsis pathogenesis. However, metabolic, coagulation, and thermoregulatory alterations also occur in patients with sepsis. Fatty acid mobilization and oxidation changes may assume the role of a protagonist in sepsis pathogenesis. Lipid oxidation and free fatty acids (FFAs) are potentially valuable markers for sepsis diagnosis and prognosis. Herein, we discuss inflammatory and metabolic dysfunction during sepsis, focusing on fatty acid oxidation (FAO) alterations in the liver and muscle (skeletal and cardiac) and their implications in sepsis development.

Ameliorative Effects of Lactobacillus paracasei L14 on Oxidative Stress and Gut Microbiota in Type 2 Diabetes Mellitus Rats

Bioprospecting of more novel probiotic strains has attained continuous interest. This study aimed to investigate the beneficial effects of Lactobacillus paracasei strain L14, an isolate from a traditional Chinese dairy product, on type 2 diabetes mellitus (T2DM) rats. Preventive supplementation of strain L14 showed excellent anti-diabetic effects on high-fat diet/low-dose streptozotocin (HFD/STZ)-induced T2DM rats. It significantly reduced hyperglycemia, protected pancreatic β-cell and liver function, and ameliorated oxidative stress while considerably improving dyslipidemia and inflammation. Furthermore, the strain modulated the gut microbiota to alleviate gut dysbiosis. Interestingly, most of these biochemical parameters could even restore to normal levels by the intervention of strain L14. The whole-genome sequencing of L14 was performed to provide a critical molecular basis for its probiotic activities. Genes related to antioxidant systems and other beneficial microbial metabolites like exopolysaccharides (EPS) biosynthesis were found. This study demonstrates that probiotic L. paracasei L14 has good potential for applications in functional food and pharmaceutical industries.

The Role of Oxidative Stress and Cellular Senescence in the Pathogenesis of Metabolic Associated Fatty Liver Disease and Related Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) represents a worryingly increasing cause of malignancy-related mortality, while Metabolic Associated Fatty Liver Disease (MAFLD) is going to become its most common cause in the next decade. Understanding the complex underlying pathophysiology of MAFLD-related HCC can provide opportunities for successful targeted therapies. Of particular interest in this sequela of hepatopathology is cellular senescence, a complex process characterised by cellular cycle arrest initiated by a variety of endogenous and exogenous cell stressors. A key biological process in establishing and maintaining senescence is oxidative stress, which is present in multiple cellular compartments of steatotic hepatocytes. Oxidative stress-induced cellular senescence can change hepatocyte function and metabolism, and alter, in a paracrine manner, the hepatic microenvironment, enabling disease progression from simple steatosis to inflammation and fibrosis, as well as HCC. The duration of senescence and the cell types it affects can tilt the scale from a tumour-protective self-restricting phenotype to the creator of an oncogenic hepatic milieu. A deeper understanding of the mechanism of the disease can guide the selection of the most appropriate senotherapeutic agent, as well as the optimal timing and cell type targeting for effectively combating HCC.

miR-10a-3p modulates adiposity and suppresses adipose inflammation through TGF-β1/Smad3 signaling pathway

Background

Obesity is a multifactorial disease characterized by an enhanced amount of fat and energy storage in adipose tissue (AT). Obesity appears to promote and maintain low-grade chronic inflammation by activating a subset of inflammatory T cells, macrophages, and other immune cells that infiltrate the AT. Maintenance of AT inflammation during obesity involves regulation by microRNAs (miRs), which also regulate the expression of genes implicated in adipocyte differentiation. This study aims to use ex vivo and in vitro approaches to evaluate the role and mechanism of miR-10a-3p in adipose inflammation and adipogenesis.

Methods

Wild-type BL/6 mice were placed on normal (ND) and high-fat diet (HFD) for 12 weeks and their obesity phenotype, inflammatory genes, and miRs expression were examined in the AT. We also used differentiated 3T3-L1 adipocytes for mechanistic in vitro studies.

Results

Microarray analysis allowed us to identify an altered set of miRs in the AT immune cells and Ingenuity pathway analysis (IPA) prediction demonstrated that miR-10a-3p expression was downregulated in AT immune cells in the HFD group as compared to ND. A molecular mimic of miR-10a-3p reduced expression of inflammatory M1 macrophages, cytokines, and chemokines, including transforming growth factor-beta 1 (TGF-β1), transcription factor Krüppel-like factor 4 (KLF4), and interleukin 17F (IL-17F) and induced expression of forkhead box P3 (FoxP3) in the immune cells isolated from AT of HFD-fed mice as compared to ND. In differentiated 3T3-L1 adipocytes, the miR-10a-3p mimics also reduced expression of proinflammatory genes and lipid accumulation, which plays a role in the dysregulation of AT function. In these cells, overexpression of miR-10a-3p reduced the expression of TGF-β1, Smad3, CHOP-10, and fatty acid synthase (FASN), relative to the control scramble miRs.

Conclusion

Our findings suggest that miR-10a-3p mimic mediates the TGF-β1/Smad3 signaling to improve metabolic markers and adipose inflammation. This study provides a new opportunity for the development of miR-10a-3p as a novel therapeutic for adipose inflammation, and its associated metabolic disorders.

Serum Fibroblast Growth Factor 21 Level After an Oral Fat Tolerance Test is Related to Postprandial Free Fatty Acid Level

Purpose

The relationship between blood lipids and fibroblast growth factor (FGF) 21 in the postprandial period remains unclear. To investigate this, we observed the changes in blood lipid levels after an oral fat tolerance test (OFTT) and examined the short-term effects on FGF21.

Patients and Methods

A total of 158 non-diabetic adult volunteers who underwent OFTT were randomly recruited from the Hebei General Hospital. Participants were stratified into three groups according to fasting and 4-h postprandial triglyceride levels: normal fat tolerance (NFT), impaired fat tolerance (IFT), and hypertriglyceridemia (HTG). Blood samples were collected at 2-h intervals for 6 h. Circulating total cholesterol levels, triglycerides, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, free fatty acids (FFA), and FGF21 were assessed.

Results

Fasting FGF21 levels increased progressively in the NFT, IFT, and HTG groups and were strongly correlated with FFA levels (r = 0.531, P < 0.001). During the OFTT, the FFA and FGF21 levels decreased and then increased after reaching a nadir at 2 and 4 h, respectively. After adjusting for potential risk factors, the FFA incremental area under the curve (iAUC) was an independent influencing factor of FGF21 iAUC (P = 0.005).

Conclusion

Fasting FGF21 levels showed a strong positive correlation with FFA. During OFTT, changes in FGF21 levels were closely associated with alterations in FFA exogenously changed by OFTT. Moreover, they were linearly related to each other. Therefore, the serum FGF21 level is positively correlated to the FFA level in the postprandial period.

Atherosclerosis and Inflammation: Insights from the Theory of General Pathological Processes

Recent advances have greatly improved our understanding of the molecular mechanisms behind atherosclerosis pathogenesis. However, there is still a need to systematize this data from a general pathology perspective, particularly with regard to atherogenesis patterns in the context of both canonical and non-classical inflammation types. In this review, we analyze various typical phenomena and outcomes of cellular pro-inflammatory stress in atherosclerosis, as well as the role of endothelial dysfunction in local and systemic manifestations of low-grade inflammation. We also present the features of immune mechanisms in the development of productive inflammation in stable and unstable plaques, along with their similarities and differences compared to canonical inflammation. There are numerous factors that act as inducers of the inflammatory process in atherosclerosis, including vascular endothelium aging, metabolic dysfunctions, autoimmune, and in some cases, infectious damage factors. Life-critical complications of atherosclerosis, such as cardiogenic shock and severe strokes, are associated with the development of acute systemic hyperinflammation. Additionally, critical atherosclerotic ischemia of the lower extremities induces paracoagulation and the development of chronic systemic inflammation. Conversely, sepsis, other critical conditions, and severe systemic chronic diseases contribute to atherogenesis. In summary, atherosclerosis can be characterized as an independent form of inflammation, sharing similarities but also having fundamental differences from low-grade inflammation and various variants of canonical inflammation (classic vasculitis).

Cardamom (Elettaria cardamomum (L.) Maton) Seeds Intake Increases Energy Expenditure and Reduces Fat Mass in Mice by Modulating Neural Circuits That Regulate Adipose Tissue Lipolysis and Mitochondrial Oxidative Metabolism in Liver and Skeletal Muscle

Cardamom seed (Elettaria cardamomum (L.) Maton; EC) is consumed in several countries worldwide and is considered a nutraceutical spice since it exerts antioxidant, anti-inflammatory, and metabolic activities. In obese individuals, EC intake also favors weight loss. However, the mechanism for these effects has not been studied. Here, we identified that EC modulates the neuroendocrine axis that regulates food intake, body weight, mitochondrial activity, and energy expenditure in mice. We fed C57BL/6 mice with diets containing 3%, 6%, or 12% EC or a control diet for 14 weeks. Mice fed the EC-containing diets gained less weight than control, despite slightly higher food intake. The lower final weight of EC-fed mice was due to lesser fat content but increased lean mass than control. EC intake increased lipolysis in subcutaneous adipose tissue, and reduced adipocyte size in subcutaneous, visceral, and brown adipose tissues. EC intake also prevented lipid droplet accumulation and increased mitochondrial content in skeletal muscle and liver. Accordingly, fasting and postprandial oxygen consumption, as well as fasting fat oxidation and postprandial glucose utilization were higher in mice fed with EC than in control. EC intake reduced proopiomelanocortin (POMC) mRNA content in the hypothalamic arcuate nucleus, without an impact on neuropeptide Y (NPY) mRNA. These neuropeptides control food intake but also influence the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-adrenal (HPA) axes. Thyrotropin-releasing hormone (TRH) mRNA expression in the hypothalamic paraventricular nucleus (PVN) and circulating triiodothyronine (T₃) were lower in EC-fed mice than in control. This effect was linked with decreased circulating corticosterone and weight of adrenal glands. Our results indicate that EC modulates appetite, increases lipolysis in adipose tissue and mitochondrial oxidative metabolism in liver and skeletal muscle, leading to increased energy expenditure and lower body fat mass. These metabolic effects were ascribable to the modulation of the HPT and HPA axes. LC-MS profiling of EC found 11 phenolic compounds among which protocatechuic acid (23.8%), caffeic acid (21.06%) and syringic acid (29.25%) were the most abundant, while GC-MS profiling showed 16 terpenoids among which costunolide (68.11%), ambrial (5.3%) and cis-α-terpineol (7.99%) were identified. Extrapolation of mice-to-human EC intake was performed using the body surface area normalization equation which gave a conversion equivalent daily human intake dose of 76.9-308.4 mg bioactives for an adult of 60 kg that can be obtained from 14.5-58.3 g of cardamom seeds (18.5-74.2 g cardamom pods). These results support further exploration of EC as a coadjuvant in clinical practice.

Diagnostic performance of hypoechoic perinephric fat as a predictor of prediabetes and diabetes

PURPOSE

To evaluate prevalence and predictive value of hypoechoic perinephric fat (HPF) in patients with prediabetes and diabetes compared to non-diabetics.

METHODS

Of 240 patients with renal ultrasound and hemoglobin A1c (HbA1c) measurements, 114 patients had either prediabetes (HbA1c 5.7-6.4%) or diabetes (HbA1c ≥ 6.5%), and 126 patients did not. Two radiologists (blinded to diagnosis) reviewed images and discrepancies were resolved by a third. Inter-reader agreement was compared using free-marginal kappa and intraclass correlation coefficient. Fisher's exact test, Mann-Whitney test, multivariable logistic regression, and Spearman's rank correlation test with two-tailed p < 0.05 were used to determine statistical significance.

RESULTS

HPF was exclusively identified in prediabetic and diabetic patients with a prevalence of 23% (vs 0%; p < 0.001). Identification of HPF had almost perfect inter-reader agreement (k = 0.94) and was statistically significant (p = 0.034) while controlling for body mass index (BMI) and estimated glomerular filtration rate in multivariable analysis. HPF had extremely high specificity and positive predictive value (100% for both) in patients with prediabetes and diabetes although it was not a sensitive finding (23% sensitivity). In patients with prediabetes and diabetes, those with HPF were statistically significantly more likely to have chronic kidney disease (CKD) (p = 0.003). There was no statistically significant difference in BMI, stages of CKD, and types of diabetes.

CONCLUSION

Hypoechoic perirenal fat has almost perfect inter-reader agreement and is highly specific for and predictive of prediabetes and diabetes. Its presence may also help identify those with chronic kidney disease among prediabetic and diabetic patients.

L-carnitine attenuated hyperuricemia-associated left ventricular remodeling through ameliorating cardiomyocytic lipid deposition

Hyperuricemia (HUA) is associated with left ventricular remodeling (LVR) and thereby causes the initiation and development of a large number of cardiovascular diseases. LVR is typically accompanied by cardiomyocyte energy metabolic disorder. The energy supply of cardiomyocytes is provided by glucose and fatty acid (FA) metabolism. Currently, the effect of HUA on cardiomyocytic FA metabolism is unclear. In this study, we demonstrate that UA-induced cardiomyocyte injury is associated with cytoplasmic lipid deposition, which can be ameliorated by the FA metabolism-promoting drug L-carnitine (LC). UA suppresses carnitine palmitoyl transferase 1B (CPT1B), thereby inhibiting FA transport into the mitochondrial inner matrix for elimination. LC intervention can ameliorate HUA-associated left ventricular anterior wall thickening in mice. This study showed that FA transport dysfunction plays is a critical mechanism in both cardiomyocytic injury and HUA-associated LVR and promoting cytoplasmic FA transportation through pharmacological treatment by LC is a valid strategy to attenuate HUA-associated LVR.

Prevention of Metabolic Syndrome by Phytochemicals and Vitamin D

In recent years, attention has focused on the roles of phytochemicals in fruits and vegetables in maintaining and improving the intestinal environment and preventing metabolic syndrome. A high-fat and high-sugar diet, lack of exercise, and excess energy accumulation in the body can cause metabolic syndrome and induce obesity, diabetes, and disorders of the circulatory system and liver. Therefore, the prevention of metabolic syndrome is important. The current review shows that the simultaneous intake of phytochemicals contained in citruses and grapes together with vitamin D improves the state of gut microbiota and immunity, preventing metabolic syndrome and related diseases. Phytochemicals contained in citruses include polyphenols such as hesperidin, rutin, and naringin; those in grapes include quercetin, procyanidin, and oleanolic acid. The intake of these phytochemicals and vitamin D, along with prebiotics and probiotics, nurture good gut microbiota. In general, Firmicutes are obese-prone gut microbiota and Bacteroidetes are lean-prone gut microbiota; good gut microbiota nurture regulatory T cells, which suppress inflammatory responses and upregulate immunity. Maintaining good gut microbiota suppresses TNF-α, an inflammatory cytokine that is also considered to be a pathogenic contributor adipokine, and prevents chronic inflammation, thereby helping to prevent metabolic syndrome. Maintaining good gut microbiota also enhances adiponectin, a protector adipokine that prevents metabolic syndrome. For the prevention of metabolic syndrome and the reduction of various disease risks, the intake of phytochemicals and vitamin D will be important for human health in the future.

Plasma metabolomic characterization of premature ovarian insufficiency

BACKGROUND

Premature ovarian insufficiency (POI) patients are predisposed to metabolic disturbances, including in lipid metabolism and glucose metabolism, and metabolic disorders appear to be a prerequisite of the typical long-term complications of POI, such as cardiovascular diseases or osteoporosis. However, the metabolic changes underlying the development of POI and its subsequent complications are incompletely understood, and there are few studies characterizing the disturbed metabolome in POI patients. The aim of this study was to characterize the plasma metabolome in POI by using ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) metabolomics and to evaluate whether these disturbances identified in the plasma metabolome relate to ovarian reserve and have diagnostic value in POI.

METHODS

This observational study recruited 30 POI patients and 30 age- and body mass index (BMI)-matched controls in the Center for Reproductive Medicine, Department of Gynecology and Obstetrics, Nanfang Hospital, Southern Medical University, from January 2018 to October 2020. Fasting venous blood was collected at 9:00 am on days 2-4 of the menstrual cycle and centrifuged for analysis. An untargeted quantitative metabolomic analysis was performed using UHPLC-MS/MS.

RESULTS

Our study identified 48 upregulated and 21 downregulated positive metabolites, and 13 upregulated and 48 downregulated negative metabolites in the plasma of POI patients. The differentially regulated metabolites were involved in pathways such as caffeine metabolism and ubiquinone and other terpenoid-quinone biosynthesis. Six metabolites with an AUC value > 0.8, including arachidonoyl amide, 3-hydroxy-3-methylbutanoic acid, dihexyl nonanedioate, 18-HETE, cystine, and PG (16:0/18:1), were correlated with ovarian reserve and thus have the potential to be diagnostic biomarkers of POI.

CONCLUSION

This UHPLC-MS/MS untargeted metabolomics study revealed differentially expressed metabolites in the plasma of patients with POI. The differential metabolites may not only be involved in the aetiology of POI but also contribute to its major complications. These findings offer a panoramic view of the plasma metabolite changes caused by POI, which may provide useful diagnostic and therapeutic clues for POI disease.

The crucial role and mechanism of insulin resistance in metabolic disease

Insulin resistance (IR) plays a crucial role in the development and progression of metabolism-related diseases such as diabetes, hypertension, tumors, and nonalcoholic fatty liver disease, and provides the basis for a common understanding of these chronic diseases. In this study, we provide a systematic review of the causes, mechanisms, and treatments of IR. The pathogenesis of IR depends on genetics, obesity, age, disease, and drug effects. Mechanistically, any factor leading to abnormalities in the insulin signaling pathway leads to the development of IR in the host, including insulin receptor abnormalities, disturbances in the internal environment (regarding inflammation, hypoxia, lipotoxicity, and immunity), metabolic function of the liver and organelles, and other abnormalities. The available therapeutic strategies for IR are mainly exercise and dietary habit improvement, and chemotherapy based on biguanides and glucagon-like peptide-1, and traditional Chinese medicine treatments (e.g., herbs and acupuncture) can also be helpful. Based on the current understanding of IR mechanisms, there are still some vacancies to follow up and consider, and there is also a need to define more precise biomarkers for different chronic diseases and lifestyle interventions, and to explore natural or synthetic drugs targeting IR treatment. This could enable the treatment of patients with multiple combined metabolic diseases, with the aim of treating the disease holistically to reduce healthcare expenditures and to improve the quality of life of patients to some extent.

We are what we eat: The role of lipids in metabolic diseases

Lipids play a fundamental role, both structurally and functionally, for the correct functioning of the organism. In the last two decades, they have evolved from molecules involved only in energy storage to compounds that play an important role as components of cell membranes and signaling molecules that regulate cell homeostasis. For this reason, their interest as compounds involved in human health has been gaining weight. Indeed, lipids derived from dietary sources and endogenous biosynthesis are relevant for the pathophysiology of numerous diseases. There exist pathological conditions that are characterized by alterations in lipid metabolism. This is particularly true for metabolic diseases, such as liver steatosis, type 2 diabetes, cancer and cardiovascular diseases. The main issue to be considered is lipid homeostasis. A precise control of fat homeostasis is required for a correct regulation of metabolic pathways and safe and efficient energy storage in adipocytes. When this fails, a deregulation occurs in the maintenance of systemic metabolism. This happens because an increased concentrations of lipids impair cellular homeostasis and disrupt tissue function, giving rise to lipotoxicity. Fat accumulation results in many alterations in the physiology of the affected organs, mainly in metabolic tissues. These alterations include the activation of oxidative and endoplasmic reticulum stress, mitochondrial dysfunction, increased inflammation, accumulation of bioactive molecules and modification of gene expression. In this chapter, we review the main metabolic diseases in which alterations in lipid homeostasis are involved and discuss their pathogenic mechanisms.

Kidney and lipids: novel potential therapeutic targets for dyslipidemia in kidney disease?

INTRODUCTION

Altered lipid distribution and metabolism may lead to the development and/or progression of chronic kidney disease (CKD). Dyslipidemia is a major risk factor for CKD and increases the risk of cardiovascular events and mortality. Therefore, lipid-lowering treatments may decrease cardiovascular risk and prevent death.

AREAS COVERED

Key players involved in regulating lipid accumulation in the kidney; contribution of lipids to CKD progression, lipotoxicity, and mitochondrial dysfunction in kidney disease; recent therapeutic approaches for dyslipidemia.

EXPERT OPINION

The precise mechanisms for regulating lipid metabolism, particularly in kidney disease, are poorly understood. Guidelines for lipid-lowering therapy for CKD are controversial. Several hypolipemic therapies are available, but compared to others, statin therapy is the most common. No clinical trial has evaluated the efficacy of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) in preventing cardiovascular events or improving kidney function among patients with CKD or kidney transplant recipients. Attractive alternatives, such as PCSK9-small interfering RNA (siRNA) molecules or evinacumab are available. Additionally, several promising agents, such as cyclodextrins and the FXR/TGR5 dual agonist, INT-767, can improve renal lipid metabolism disorders and delay CKD progression. Drugs targeting mitochondrial dysfunction could be an option for the treatment of dyslipidemia and lipotoxicity, particularly in renal diseases.

The Contribution of Lipotoxicity to Diabetic Kidney Disease

Lipotoxicity is a fundamental pathophysiologic mechanism in diabetes and non-alcoholic fatty liver disease and is now increasingly recognized in diabetic kidney disease (DKD) pathogenesis. This review highlights lipotoxicity pathways in the podocyte and proximal tubule cell, which are arguably the two most critical sites in the nephron for DKD. The discussion focuses on membrane transporters and lipid droplets, which represent potential therapeutic targets, as well as current and developing pharmacologic approaches to reduce renal lipotoxicity.

Free Fatty Acid Overload Targets Mitochondria: Gene Expression Analysis of Palmitic Acid-Treated Endothelial Cells

Lipotoxicity is known to cause cellular dysfunction and death in non-adipose tissue. A major cause of lipotoxicity is the accumulation of saturated free fatty acids (FFA). Palmitic acid (PA) is the most common saturated fatty acid found in the human body. Endothelial cells form the blood vessels and are the first non-adipose cells to encounter FFA in the bloodstream. FFA overload has a direct impact on metabolism, which is evident through the changes occurring in mitochondria. To study these changes, the PA-treated human coronary artery endothelial cell (HCAEC) dataset was obtained from the Gene Expression Omnibus (GEO), and it was analyzed to obtain differentially expressed genes (DEGs) from the nucleus and mitochondria. Functional and pathway enrichment analyses were performed on DEGs. Results showed that nuclear and mitochondrial DEGs were implicated in several processes, e.g., reactive oxygen species (ROS) production, mitochondrial fusion and fission, Ca2+ sequestering, membrane transport, the electron transport chain and the process of apoptosis. To better understand the role of FFA in endothelial cell damage, these DEGs can lead to future experiments based on these findings.

Lipid Metabolism in Glioblastoma: From De Novo Synthesis to Storage

Glioblastoma (GBM) is the most lethal primary brain tumor. With limited therapeutic options, novel therapies are desperately needed. Recent studies have shown that GBM acquires large amounts of lipids for rapid growth through activation of sterol regulatory element-binding protein 1 (SREBP-1), a master transcription factor that regulates fatty acid and cholesterol synthesis, and cholesterol uptake. Interestingly, GBM cells divert substantial quantities of lipids into lipid droplets (LDs), a specific storage organelle for neutral lipids, to prevent lipotoxicity by increasing the expression of diacylglycerol acyltransferase 1 (DGAT1) and sterol-O-acyltransferase 1 (SOAT1), which convert excess fatty acids and cholesterol to triacylglycerol and cholesteryl esters, respectively. In this review, we will summarize recent progress on our understanding of lipid metabolism regulation in GBM to promote tumor growth and discuss novel strategies to specifically induce lipotoxicity to tumor cells through disrupting lipid storage, a promising new avenue for treating GBM.