bims-stacyt Biomed news on
Starvation pathways leading to cytokine regulation
Issue of 2018‒02‒04
two papers selected by
Cristina Muñoz Pinedo
L’Institut d’Investigació Biomèdica de Bellvitge

  1. Metabolism. 2018 Jan 25. doi: 10.1016/j.metabol.2018.01.013
    Abstract:  BACKGROUND: Obesity-induced chronic inflammation is critical in the pathogenesis of insulin resistance, and the recruitment and proinflammatory activation of adipose tissue macrophages (ATMs) is important for the development of this process. Here, we examined the effects of fibronectin type III domain-containing 5 (FNDC5) on inflammation and insulin resistance in high-fat diet-induced obese mice. MATERIALS AND METHODS: Male wild-type (WT) and FNDC5-/- mice were fed with standard chow (Ctrl) or high fat diet (HFD) for 20 weeks to induce obesity and insulin resistance. Firstly, effects of FNDC5 gene deletion on obesity, insulin resistance, macrophage accumulation and polarization and adipose tissue inflammation were determined in mice. Secondly, the macrophage polarity shift was further examined with flow cytometry in isolated stromal vascular fraction (SVF). Thirdly, the effects of exogenous FNDC5 on lipopolysaccharide (LPS)-induced macrophage polarization, inflammation and the underlying signaling mechanism were investigated in RAW264.7 macrophages and primary mouse peritoneal cavity macrophages (PMs). Finally, the therapeutic effects of FNDC5 overexpression were examined in HFD-induced obese WT and FNDC5-/- mice. RESULTS: FNDC5 gene deletion aggravated obesity, insulin resistance, fat accumulation and inflammation accompanied with enhanced AMPK inhibition, macrophages recruitment and M1 polarization in mice fed with HFD. Exogenous FNDC5 inhibits LPS-induced M1 macrophage polarization and inflammatory cytokine production via AMPK phosphorylation in both RAW264.7 macrophages and PMs. FNDC5 overexpression attenuates insulin resistance, AMPK inhibition, M1 macrophage polarization and inflammatory cytokine production in adipose tissue of obese WT and FNDC5-/- mice. CONCLUSIONS: FNDC5 attenuates adipose tissue inflammation and insulin resistance via AMPK-mediated macrophage polarization in HFD-induced obesity. FNDC5 plays several beneficial roles in obesity and may be used as a therapeutic regimen for preventing inflammation and insulin resistance in obesity and diabetes.
    Keywords:  Adipose tissue; FNDC5; Inflammation; Insulin resistance; Macrophages; Obesity
  2. JOJ Ophthalmol. 2017 ;doi: 10.19080/jojo.2017.04.5556434(4):
    Abstract:  Mitochondria are responsible for bioenergetics, metabolism and apoptosis signals in health and disease. The retina being a part of the central nervous system consumes large amounts of glucose and oxygen to generate ATP via the mitochondrial oxidative phosphorylation for its phototransduction and visual function. During ATP generation, electrons leak from the mitochondrial electron transport chain, which is captured by molecular oxygen to produce reactive oxygen species (ROS). These mtROS damage mitochondrial proteins, mtDNA, and membrane lipids and release them in the cytosol. Mitochondrial components are recognized as danger-associated molecular patterns (DAMPS) by cytosolic pattern recognition receptors such as NOD-like receptors, NLRP3 inflammasomes. They process pro-caspase-1 to active caspase-1, which cleaves pro-inflammatory IL-1β o mature IL-1β causing inflammation and cell death by pyroptosis. To counter the damaging action of mtROS and inflammasomes in fully differentiated cells in the retina, the removal of the damaged and dysfunctional mitochondria by a double-membrane autophagic process via lysosomal degradation called mitophagy is critical for mitochondrial homeostasis and cell survival. Nonetheless, under chronic diseases including diabetic retinopathy (DR), mitophagy dysregulation and NLRP3 inflammasome activation exist, which cause premature cell death and disease progression. Recently, the thioredoxin-interacting protein TXNIP, which is strongly induced by diabetes and inhibits anti-oxidant function of thioredoxin, has been implicated in mitochondrial dysfunction, mitophagic dysregulation and NLRP3 inflammasome activation in DR. Therefore, TXNIP silencing or pharmacological inhibition may normalize mitophagic flux and NLRP3 inflammasome activation, which will prevent or slow down the progression of DR.
    Keywords:  Diabetic retinopathy; Mitophagy; NLRP3 inflammasome; TXNIP; mt-Keima