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Endocrinology Oct 2022Excess circulating lipids increase total intramyocellular (IMC) lipid content and ectopic fat storage, resulting in lipotoxicity and insulin resistance in skeletal...
Excess circulating lipids increase total intramyocellular (IMC) lipid content and ectopic fat storage, resulting in lipotoxicity and insulin resistance in skeletal muscle. Consumption of a diet high in fat and refined sugars-a Western diet (WD)-has been shown to activate mineralocorticoid receptors (MRs) and promote insulin resistance. However, our understanding of the precise mechanisms by which enhanced MR activation promotes skeletal muscle insulin resistance remains unclear. In this study, we investigated the mechanisms by which enhanced MR signaling in soleus muscle promotes ectopic skeletal muscle lipid accumulation and related insulin resistance. Six-week-old C57BL/6J mice were fed either a mouse chow diet or a WD with or without spironolactone (1 mg/kg/day) for 16 weeks. Spironolactone attenuated 16 weeks of WD-induced in vivo glucose intolerance and insulin resistance, and improved soleus insulin metabolic signaling. Improved insulin sensitivity was accompanied by increased glucose transporter 4 (Glut4) expression in conjunction with decreased soleus free fatty acid and IMC lipid content, as well as CD36 expression. Additionally, spironolactone prevented WD-induced soleus mitochondria dysfunction. Furthermore, MR signaling also mediated WD/aldosterone-induced reductions in soleus microRNA (miR)-99a, which was identified to negatively target CD36 and prevented palmitic acid-induced increases in CD36 expression, lipid droplet formation, mitochondria dysfunction, and insulin resistance in C2C12 cells. These data indicate that inhibition of MR activation with spironolactone prevented diet-induced abnormal expression of miR-99a, which had the capacity to reduce CD36, leading to reduced IMC lipid content and improved soleus mitochondria function and insulin sensitivity.
Topics: Aldosterone; Animals; CD36 Antigens; Diet, High-Fat; Dietary Fats; Dietary Sugars; Fatty Acids, Nonesterified; Glucose Transport Proteins, Facilitative; Insulin; Insulin Resistance; Mice; Mice, Inbred C57BL; MicroRNAs; Muscle, Skeletal; Palmitic Acid; Receptors, Mineralocorticoid; Spironolactone
PubMed: 36039677
DOI: 10.1210/endocr/bqac145 -
Cell Communication and Signaling : CCS Aug 2020Metabolites produced via traditional biochemical processes affect intracellular communication, inflammation, and malignancy. Unexpectedly, acetyl-CoA, α-ketoglutarate... (Review)
Review
Metabolites produced via traditional biochemical processes affect intracellular communication, inflammation, and malignancy. Unexpectedly, acetyl-CoA, α-ketoglutarate and palmitic acid, which are chemical species of reactions catalyzed by highly abundant, gigantic enzymatic complexes, dubbed as "metabolons", have broad "nonmetabolic" signaling functions. Conserved unstructured regions within metabolons determine the yield of these metabolites. Unstructured regions tether functional protein domains, act as spatial constraints to confine constituent enzyme communication, and, in the case of acetyl-CoA production, tend to be regulated by intricate phosphorylation patterns. This review presents the multifaceted roles of these three significant metabolites and describes how their perturbation leads to altered or transformed cellular function. Their dedicated enzymatic systems are then introduced, namely, the pyruvate dehydrogenase (PDH) and oxoglutarate dehydrogenase (OGDH) complexes, and the fatty acid synthase (FAS), with a particular focus on their structural characterization and the localization of unstructured regions. Finally, upstream metabolite regulation, in which spatial occupancy of unstructured regions within dedicated metabolons may affect metabolite availability and subsequently alter cell functions, is discussed. Video abstract.
Topics: Acetyl Coenzyme A; Animals; Fatty Acid Synthases; Humans; Intrinsically Disordered Proteins; Ketoglutarate Dehydrogenase Complex; Ketoglutaric Acids; Models, Molecular; Palmitic Acid; Pyruvate Dehydrogenase Complex; Signal Transduction
PubMed: 32843078
DOI: 10.1186/s12964-020-00631-9 -
Kidney & Blood Pressure Research 2023Protein-energy waste (PEW) is a common complication in patients with chronic kidney disease (CKD), among which skeletal muscle atrophy is one of the most important...
INTRODUCTION
Protein-energy waste (PEW) is a common complication in patients with chronic kidney disease (CKD), among which skeletal muscle atrophy is one of the most important clinical features of PEW. Pyroptosis is a type of proinflammatory, programmed cell death associated with skeletal muscle disease. Irisin, as a novel myokine, has attracted extensive attention for its protective role in the complications associated with CKD, but its role in muscle atrophy in CKD is unclear.
METHODS
Palmitic acid (PA)-induced muscular atrophy was evaluated by a reduction in C2C12 myotube diameter. Muscle atrophy model was established in male C57BL/6J mice treated with 0.2% adenine for 4 weeks and then fed a 45% high-fat diet. Blood urea nitrogen and creatinine levels, body and muscle weight, and muscle histology were assessed. The expression of carnitine palmitoyltransferase 1A (CPT1A) and pyroptosis-related protein was analysed by Western blots or immunohistochemistry. The release of IL-1β was detected by enzyme-linked immunosorbent assay.
RESULTS
In this study, we showed that PA-induced muscular atrophy manifested as a reduction in C2C12 myotube diameter. During this process, PA can also induce pyroptosis, as shown by the upregulation of NLRP3, cleaved caspase-1 and GSDMD-N expression and the increased IL-1β release and PI-positive cell rate. Inhibition of caspase-1 or NLRP3 attenuated PA-induced pyroptosis and myotube atrophy in C2C12 cells. Importantly, irisin treatment significantly ameliorated PA-induced skeletal muscle pyroptosis and atrophy. In terms of mechanism, PA upregulated CPT1A, a key enzyme of fatty acid oxidation (FAO), and irisin attenuated this effect, which was consistent with etomoxir (CPT1A inhibitor) treatment. Moreover, irisin improved skeletal muscle atrophy and pyroptosis in adenine-induced mice by regulating FAO.
CONCLUSION
Our study firstly verifies that pyroptosis is a novel mechanism of skeletal muscle atrophy in CKD. Irisin ameliorates skeletal muscle atrophy by inhibiting FAO and pyroptosis in CKD, and irisin may be developed as a potential therapeutic agent for the treatment of muscle wasting in CKD patients.
Topics: Animals; Male; Mice; Adenine; Caspases; Fibronectins; Mice, Inbred C57BL; Muscle, Skeletal; Muscular Atrophy; NLR Family, Pyrin Domain-Containing 3 Protein; Palmitic Acid; Pyroptosis; Renal Insufficiency, Chronic
PubMed: 37717561
DOI: 10.1159/000533926 -
ELife May 2022In diabetic patients, dyslipidemia frequently contributes to organ damage such as diabetic kidney disease (DKD). Dyslipidemia is associated with both excessive...
In diabetic patients, dyslipidemia frequently contributes to organ damage such as diabetic kidney disease (DKD). Dyslipidemia is associated with both excessive deposition of triacylglycerol (TAG) in lipid droplets (LDs) and lipotoxicity. Yet, it is unclear how these two effects correlate with each other in the kidney and how they are influenced by dietary patterns. By using a diabetes mouse model, we find here that high-fat diet enriched in the monounsaturated oleic acid (OA) caused more lipid storage in LDs in renal proximal tubular cells (PTCs) but less tubular damage than a corresponding butter diet with the saturated palmitic acid (PA). This effect was particularly evident in S2/S3 but not S1 segments of the proximal tubule. Combining transcriptomics, lipidomics, and functional studies, we identify endoplasmic reticulum (ER) stress as the main cause of PA-induced PTC injury. Mechanistically, ER stress is caused by elevated levels of saturated TAG precursors, reduced LD formation, and, consequently, higher membrane order in the ER. Simultaneous addition of OA rescues the cytotoxic effects by normalizing membrane order and increasing both TAG and LD formation. Our study thus emphasizes the importance of monounsaturated fatty acids for the dietary management of DKD by preventing lipid bilayer stress in the ER and promoting TAG and LD formation in PTCs.
Topics: Animals; Diabetes Mellitus; Endoplasmic Reticulum Stress; Fatty Acids; Fatty Acids, Monounsaturated; Humans; Kidney; Kidney Tubules, Proximal; Lipid Bilayers; Mice; Palmitic Acid; Triglycerides
PubMed: 35550039
DOI: 10.7554/eLife.74391 -
Analytical Chemistry Oct 2022Mid-infrared photothermal (MIP) microscopy is a valuable tool for sensitive and fast chemical imaging with high spatial resolution beyond the mid-infrared diffraction...
Mid-infrared photothermal (MIP) microscopy is a valuable tool for sensitive and fast chemical imaging with high spatial resolution beyond the mid-infrared diffraction limit. The highest sensitivity is usually achieved with heterodyne MIP employing photodetector point-scans and lock-in detection, while the fastest systems use camera-based widefield MIP with pulsed probe light. One challenge is to simultaneously achieve high sensitivity, spatial resolution, and speed in a large field of view. Here, we present widefield mid-infrared photothermal heterodyne (WIPH) imaging, where a digital frequency-domain lock-in (DFdLi) filter is used for simultaneous multiharmonic demodulation of MIP signals recorded by individual camera pixels at frame rates up to 200 kHz. The DFdLi filter enables the use of continuous-wave probe light, which, in turn, eliminates the need for synchronization schemes and allows measuring MIP decay curves. The WIPH approach is characterized by imaging potassium ferricyanide microparticles and applied to detect lipid droplets (alkyne-palmitic acid) in 3T3-L1 fibroblast cells, both in the cell-silent spectral region around 2100 cm using an external-cavity quantum cascade laser. The system achieved up to 4000 WIPH images per second at a signal-to-noise ratio of 5.52 and 1 μm spatial resolution in a 128 × 128 μm field of view. The technique opens up for real-time chemical imaging of fast processes in biology, medicine, and material science.
Topics: Alkynes; Lasers, Semiconductor; Microscopy; Palmitic Acid; Signal-To-Noise Ratio
PubMed: 36197677
DOI: 10.1021/acs.analchem.2c02548 -
Nucleic Acids Research Jan 2022Tricyclo-DNA (tcDNA) is a conformationally constrained oligonucleotide analog that has demonstrated great therapeutic potential as antisense oligonucleotide (ASO) for...
Tricyclo-DNA (tcDNA) is a conformationally constrained oligonucleotide analog that has demonstrated great therapeutic potential as antisense oligonucleotide (ASO) for several diseases. Like most ASOs in clinical development, tcDNA were modified with phosphorothioate (PS) backbone for therapeutic purposes in order to improve their biodistribution by enhancing association with plasma and cell protein. Despite the advantageous protein binding properties, systemic delivery of PS-ASO remains limited and PS modifications can result in dose limiting toxicities in the clinic. Improving extra-hepatic delivery of ASO is highly desirable for the treatment of a variety of diseases including neuromuscular disorders such as Duchenne muscular dystrophy. We hypothesized that conjugation of palmitic acid to tcDNA could facilitate the delivery of the ASO from the bloodstream to the interstitium of the muscle tissues. We demonstrate here that palmitic acid conjugation enhances the potency of tcDNA-ASO in skeletal and cardiac muscles, leading to functional improvement in dystrophic mice with significantly reduced dose of administered ASO. Interestingly, palmitic acid-conjugated tcDNA with a full phosphodiester backbone proved effective with a particularly encouraging safety profile, offering new perspectives for the clinical development of PS-free tcDNA-ASO for neuromuscular diseases.
Topics: Animals; Genetic Therapy; Male; Mice; Mice, Inbred C57BL; Mice, Inbred mdx; Muscle, Skeletal; Muscular Dystrophy, Duchenne; Myocardium; Oligonucleotides, Antisense; Palmitic Acid; Tissue Distribution
PubMed: 34893881
DOI: 10.1093/nar/gkab1199 -
Biomedicine & Pharmacotherapy =... Jan 2021Nosocomial Candida colonization causes Systemic candidiasis in human with invasive infections in immunocompromised patients. Of all Candida spp., C. albicans is dominant...
Nosocomial Candida colonization causes Systemic candidiasis in human with invasive infections in immunocompromised patients. Of all Candida spp., C. albicans is dominant in morbidity of all systemic candidiasis but C. tropicalis is phenomenal in mortality, virulence aspects and resistance development against antifungal drugs. The present study investigated the synergistic anti-virulent activity of myristic acid (MA) and palmitic acid (PA) against insidious dimorphic Candida spp. (C. albicans and C. tropicalis). In vitro and qPCR results revealed the mechanisms of MA-PA combination effectively inhibiting various virulence aspects such as biofilm, hyphal formation, secreted aspartyl proteases, lipases, ergosterol biosynthesis and drug effluxes. Further, in Danio rerio (Zebrafish), the MA-PA treatment increased the survival of animals and also the treated groups showed decreased level of fungal burden compared to the infected controls, after 3 day of post infection. Histopathology of vital organs and SEM analysis of skin revealed a drastic recovery and reduced the inflammation of both Candida spp. infections in MA-PA treated animals. In addition, MA-PA treatment reduced the haemolysin and increased the susceptibility of Candida spp. in human blood model. Hence, this study suggested the therapeutic utilization of MA-PA as synergistic combination for their anti-inflammatory potency against systemic candidiasis and candidemia.
Topics: Animals; Anti-Inflammatory Agents; Antifungal Agents; Candida albicans; Candida tropicalis; Candidiasis; Disease Models, Animal; Drug Synergism; Drug Therapy, Combination; Humans; Microbial Viability; Myristic Acid; Palmitic Acid; Virulence; Zebrafish
PubMed: 33378951
DOI: 10.1016/j.biopha.2020.111043 -
Biomolecules Oct 2021Elevated level of palmitic acid (PA), a long-chain saturated fatty acid (SFA), is lipotoxic to many different types of cells including Neuro-2a (N2a) neuroblastoma...
Elevated level of palmitic acid (PA), a long-chain saturated fatty acid (SFA), is lipotoxic to many different types of cells including Neuro-2a (N2a) neuroblastoma cells. CD36 is a multifunctional membrane glycoprotein that acts as a fatty acid translocase (FAT) facilitating the transport of long-chain free fatty acids (FFAs) into cells, serves a fatty acid (FA) sensing function in areas including taste buds and the proximal gut, and acts as a scavenger receptor that binds to many ligands, including FAs, collagen, oxidized low-density lipoproteins, and anionic phospholipids. However, the involvement of CD36 in FA uptake and PA lipotoxicity in N2a cells remains unclear. In this study, we examined FA uptake in BSA- and PA-treated N2a cells and investigated the involvement of CD36 in FA uptake and PA lipotoxicity in N2a cells. Our data showed that PA treatment promoted FA uptake in N2a cells, and that treatment with sulfo-N-succinimidyl oleate (SSO), a CD36 inhibitor, significantly decreased FA uptake in BSA- and PA-treated N2a cells, and ameliorated PA-induced decrease of cell viability, decrease of diploid cells, and increase of tetraploid cells. We also found that CD36 knockdown significantly decreased FA uptake in both BSA- and PA-treated cells as compared to their corresponding wild-type controls, and dramatically attenuated PA-induced cell cycle defects in N2a cells. Our data suggest that CD36 may play a critical role in FA uptake and PA lipotoxicity in N2a cells. CD36 may therefore represent a regulatory target against pathologies caused by excess FAs.
Topics: CD36 Antigens; Fatty Acids; Lipoproteins, LDL; Palmitic Acid
PubMed: 34827565
DOI: 10.3390/biom11111567 -
International Journal of Molecular... Aug 2021Obesity and metabolic syndrome are associated with cognitive decline and dementia. Palmitic acid (PA) is increased in the cerebrospinal fluid of obese patients with...
Obesity and metabolic syndrome are associated with cognitive decline and dementia. Palmitic acid (PA) is increased in the cerebrospinal fluid of obese patients with cognitive impairment. This study was therefore designed to examine fatty acid (FA) lipotoxicity in BV2 microglia cells. We found that PA induced time- and dose-dependent decrease in cell viability and increase in cell death without affecting the cell cycle profile and that PA lipotoxicity did not depend on cell surface free fatty acid receptors but rather on FA uptake. Treatment with sulfosuccinimidyl oleate (SSO), an irreversible inhibitor of fatty acid translocase CD36, significantly inhibited FA uptake in BSA- and PA-treated cells and blocked PA-induced decrease in cell viability. Inhibition of ER stress or treatment with N-acetylcysteine was not able to rescue PA lipotoxicity. Our study also showed that unsaturated fatty acids (UFAs), such as linoleic acid (LA), oleic acid (OA), α-linolenic acid (ALA), and docosahexaenoic acid (DHA), were not lipotoxic but instead protected microglia against PA-induced decrease in cell viability. Co-treatment of PA with LA, OA, and DHA significantly inhibited FA uptake in PA-treated cells. All UFAs tested induced the incorporation of FAs into and the amount of neutral lipids, while PA did not significantly affect the amount of neutral lipids compared with BSA control.
Topics: Animals; Cell Death; Cell Survival; Fatty Acids, Nonesterified; Fatty Acids, Unsaturated; Lipids; Mice; Microglia; Palmitic Acid
PubMed: 34445796
DOI: 10.3390/ijms22169093 -
The American Journal of Clinical... May 2021Interesterified (IE) fats are widely used in place of trans fats; however, little is known about their metabolism. (Randomized Controlled Trial)
Randomized Controlled Trial
Palmitic acid-rich oils with and without interesterification lower postprandial lipemia and increase atherogenic lipoproteins compared with a MUFA-rich oil: A randomized controlled trial.
BACKGROUND
Interesterified (IE) fats are widely used in place of trans fats; however, little is known about their metabolism.
OBJECTIVES
To test the impact of a commonly consumed IE compared with a non-IE equivalent fat on in vivo postprandial and in vitro lipid metabolism, compared with a reference oil [rapeseed oil (RO)].
METHODS
A double-blinded, 3-phase crossover, randomized controlled trial was performed in healthy adults (n = 20) aged 45-75 y. Postprandial plasma triacylglycerol and lipoprotein responses (including stable isotope tracing) to a test meal (50 g fat) were evaluated over 8 h. The test fats were IE 80:20 palm stearin/palm kernel fat, an identical non-IE fat, and RO (control). In vitro, mechanisms of digestion were explored using a dynamic gastric model (DGM).
RESULTS
Plasma triacylglycerol 8-h incremental area under the curves were lower following non-IE compared with RO [-1.7 mmol/L⋅h (95% CI: -3.3, -0.0)], but there were no differences between IE and RO or IE and non-IE. LDL particles were smaller following IE and non-IE compared with RO (P = 0.005). Extra extra large, extra large, and large VLDL particle concentrations were higher following IE and non-IE compared with RO at 6-8 h (P < 0.05). No differences in the appearance of [13C]palmitic acid in plasma triacylglycerol were observed between IE and non-IE fats. DGM revealed differences in phase separation of the IE and non-IE meals and delayed release of SFAs compared with RO.
CONCLUSIONS
Interesterification did not modify fat digestion, postprandial lipemia, or lipid metabolism measured by stable isotope and DGM analysis. Despite the lower lipemia following the SFA-rich fats, increased proatherogenic large triacylglycerol-rich lipoprotein remnant and small LDL particles following the SFA-rich fats relative to RO adds a new postprandial dimension to the mechanistic evidence linking SFAs to cardiovascular disease risk.
Topics: Aged; Apolipoprotein B-48; Atherosclerosis; Chylomicrons; Cross-Over Studies; Dietary Fats, Unsaturated; Double-Blind Method; Fatty Acids, Monounsaturated; Female; Humans; Hyperlipidemias; Lipoproteins; Male; Middle Aged; Palmitic Acid; Postprandial Period; Triglycerides
PubMed: 33675343
DOI: 10.1093/ajcn/nqaa413