The mechanisms leading to higher risks of infection in diabetics remain unknown despite recent advances in the understanding of associated immunological and metabolic aberrations. Hyperglycemia and hyperlipidemia in diabetics not only contribute to altered metabolism but glucose and free fatty acids can directly activate inflammation and the production of the proinflammatory cytokine interleukin 1β (IL-1β). Long-chain saturated fatty acids activate toll-like receptor 4 (TLR4), generating diacylglycerol and activating protein kinase C to upregulate the Akt/mammalian target of rapamycin complex 1 (mTORC1) pathway. High glucose uptake switches cell metabolism from oxidative phosphorylation to glycolysis and deactivates AMP-activated protein kinase (AMPK), a critical sensor of nutrient and cellular energy, leading to mTORC1 activation. A deleterious consequence of mTORC1 activation is the suppression of autophagy which is a catabolic process for the lysosomal degradation of damaged organelles, protein aggregates and intracellular pathogens. In addition, high glucose concentration and fatty acids independently activate inflammasome, an intracellular multi-protein complex that promotes the proteolytic activation of caspase 1, leading to the processing and secretion of IL-1β. Other caspases induced by inflammasome can trigger apoptotic cell death. A common upstream signal for the activation of inflammasome and mTORC1 is oxidative stress, which generates reactive oxygen species (ROS) from dysregulated mitochondria. Increased flux of glucose and lipids activates stress kinases, enhances electron transport, and generates ROS in mitochondria. Mitochondrial stress arising from increased mitochondrial respiration and permeability damages mitochondria, activates caspases, which then induce apoptosis via the intrinsic cell death pathway releasing mitochondrial DNA. Normally apoptosis is down-regulated by autophagy as autophagy removes damaged organelles as a result of danger and stress signals. However, in diabetics, hyperactivation of mTORC1 disrupts the host autophagic degradation of microbes and damaged mitochondria which in turn exacerbates inflammasome activation and alters cell resistance to infection. Recognition of viral lipids and bacterial components by host cell pattern recognition receptors including TLR activates NFκB and stress kinase c-jun N-terminal kinase (JNK) signaling. The transcription factor NFκB and JNK independently induce inflammatory cytokines, chemokines, and further activate inflammasome. The convergence of inflammasome and mTORC1 activation with metabolic stress and vascular dysfunction in diabetics prevents pathogen clearance and contributes to an increased risk of infection.
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http://dx.doi.org/10.1016/j.mehy.2015.08.019 | DOI Listing |
J Am Soc Nephrol
January 2025
Nephrology Division, Department of Medicine, the Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China.
Background: Peritoneal fibrosis is a serious complication of long-term peritoneal dialysis (PD) and abdominal surgeries, yet effective treatments remain elusive. Given the known roles of mucosal-associated invariant T (MAIT) cells in immune responses and fibrotic diseases, we investigated their involvement in PD-induced peritoneal fibrosis to identify potential therapeutic targets.
Methods: We employed single-cell RNA sequencing (scRNA-seq) and flow cytometry to characterize the activation and function of peritoneal MAIT cells in patients undergoing long-term PD.
Life Med
June 2024
Cancer Institute (Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education) of the Second Affiliated Hospital, and Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou 310029, China.
SHOC2 is a scaffold protein that activates the RAS-MAPK signal. Our recent study showed that SHOC2 is also a negative regulator of the mTORC1 signal in lung cancer cells. Whether and how SHOC2 differentially regulates the RAS-MAPK vs.
View Article and Find Full Text PDFAm J Physiol Cell Physiol
January 2025
Department of Kinesiology and Nutrition, University of Illinois Chicago, Chicago, IL, USA.
Hepatic lipotoxicity, resulting from excessive lipid accumulation in hepatocytes, plays a central role in the pathogenesis of various metabolic liver diseases. Despite recent progress, the precise mechanisms remain incompletely understood. Employing excessive exposure to palmitate in hepatocytes as our primary experimental model and mice studies, we aimed to uncover the mechanisms behind hepatic lipotoxicity, thereby developing potential treatments.
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January 2025
Aging and Metabolism Research Program, Oklahoma City, OK, United States.
Sulforaphane (SFN) is an isothiocyanate derived from cruciferous vegetables that has demonstrated anti-cancer, anti-microbial and anti-oxidant properties. SFN ameliorates various disease models in rodents (e.g.
View Article and Find Full Text PDFSci Rep
January 2025
Department of Cardiology, Angiology and Pneumology, University Hospital Heidelberg, Heidelberg, Germany.
Pathological cardiac remodeling is a maladaptive response that leads to changes in the size, structure, and function of the heart. These changes occur due to an acute or chronic stress on the heart and involve a complex interplay of hemodynamic, neurohormonal and molecular factors. As a critical regulator of cell growth, protein synthesis and autophagy mechanistic target of rapamycin complex 1 (mTORC1) is an important mediator of pathological cardiac remodeling.
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