Caloric restriction mimetic 2-deoxyglucose alleviated lethal liver injury induced by lipopolysaccharide/D-galactosamine in mice

Clearance of β-amyloid mediated by autophagy is enhanced by MTORC1 inhibition but not AMPK activation in APP/PSEN1 astrocytes

Proteostasis mechanisms mediated by macroautophagy/autophagy are altered in neurodegenerative diseases such as Alzheimer disease (AD) and their recovery/enhancement has been proposed as a therapeutic approach. From the two central nodes in the anabolism-catabolism balance, it is generally accepted that mechanistic target of rapamycin kinase complex 1 (MTORC1)_ activation leads to the inhibition of autophagy, whereas adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) has the opposite role. In AD, amyloid beta (Aβ) production disturbs the optimal neuronal/glial proteostasis. As astrocytes are essential for brain homeostasis, the purpose of this work was to analyze if the upregulation of autophagy in this cell type, either by MTORC1 inhibition or AMPK activation, could modulate the generation/degradation of β-amyloid. By using primary astrocytes from amyloid beta precursor protein (APP)/Presenilin 1 (PSEN1) mouse model of AD, we confirmed that MTORC1 inhibition reduced Aβ secretion through moderate autophagy induction. Surprisingly, pharmacologically increased activity of AMPK did not enhance autophagy but had different effects on Aβ secretion. Conversely, AMPK inhibition did not affect autophagy but reduced Aβ secretion. These puzzling data were confirmed through the overexpression of different mutant AMPK isoforms: while only the constitutively active AMPK increased autophagy, all versions augmented Aβ secretion. We conclude that AMPK has a significantly different role in primary astrocytes than in other reported cells, similar to our previous findings in neurons. Our data support that perhaps only a basal AMPK activity is needed to maintain autophagy whereas the increased activity, either physiologically or pharmacologically, has no direct effect on autophagy-dependent amyloidosis. These results shed light on the controversy about the therapeutic effect of AMPK activation on autophagy induction.

Research progress of hexokinase 2 in inflammatory-related diseases and its inhibitors

Hexokinase 2 (HK2) is a crucial enzyme involved in glycolysis, which converts glucose into glucose-6-phosphate and plays a significant role in glucose metabolism. HK2 can mediate glycolysis, which is linked to the release of inflammatory factors. The over-expression of HK2 increases the production of pro-inflammatory cytokines, exacerbating the inflammatory reaction. Consequently, HK2 is closely linked to various inflammatory-related diseases affecting multiple systems, including the digestive, nervous, circulatory, respiratory, reproductive systems, as well as rheumatoid arthritis. HK2 is regarded as a novel therapeutic target for inflammatory-related diseases, and this article provides a comprehensive review of its roles in these conditions. Furthermore, the development of potent HK2 inhibitors has garnered significant attention in recent years. Therefore, this review also presents a summary of potential HK2 inhibitors, offering promising prospects for the treatment of inflammatory-related diseases in the future.

Negative regulation of pro-apoptotic AMPK/JNK pathway by itaconate in mice with fulminant liver injury

Accumulating evidence indicates that metabolic responses are deeply integrated into signal transduction, which provides novel opportunities for the metabolic control of various disorders. Recent studies suggest that itaconate, a highly concerned bioactive metabolite catalyzed by immune responsive gene 1 (IRG1), is profoundly involved in the regulation of apoptosis, but the underlying mechanisms have not been fully understood. In the present study, the molecular mechanisms responsible for the apoptosis-modulatory activities of IRG1/itaconate have been investigated in mice with lipopolysaccharide (LPS)/D-galactosamine (D-Gal)-induced apoptotic liver injury. The results indicated that LPS/D-Gal exposure upregulated the level of IRG1 and itaconate. Deletion of IRG1 resulted in exacerbated hepatocytes apoptosis and liver injury. The phospho-antibody microarray analysis and immunoblot analysis indicated that IRG1 deletion enhanced the activation of AMP-activated protein kinase (AMPK)/c-jun-N-terminal kinase (JNK) pathway in LPS/D-Gal exposed mice. Mechanistically, IRG1 deficiency impaired the anti-oxidative nuclear factor erythroid-2 related factor 2 (Nrf2) signaling and then enhanced the activation of the redox-sensitive AMPK/JNK pathway that promotes hepatocytes apoptosis. Importantly, post-insult supplementation with 4-octyl itaconate (4-OI), a cell-permeable derivate of itaconate, resulted in beneficial outcomes in fulminant liver injury. Therefore, IRG1/itaconate might function as a negative regulator that controls AMPK-induced hepatocyte apoptosis in LPS/D-Gal-induced fulminant liver injury.

AMPK activation does not enhance autophagy in neurons in contrast to MTORC1 inhibition: different impact on β-amyloid clearance

The physiological AKT-MTORC1 and AMPK signaling pathways are considered key nodes in the regulation of anabolism-catabolism, and particularly of macroautophagy/autophagy. Indeed, it is reported that these are altered processes in neurodegenerative proteinopathies such as Alzheimer disease (AD), mainly characterized by deposits of β-amyloid (Aβ) and hyperphosphorylated MAPT. These accumulations disrupt the optimal neuronal proteostasis, and hence, the recovery/enhancement of autophagy has been proposed as a therapeutic approach against these proteinopathies. The purpose of the present study was to characterize the modulation of autophagy by MTORC1 and AMPK signaling pathways in the highly specialized neurons, as well as their repercussions on Aβ production. Using a double transgenic mice model of AD, we demonstrated that MTORC1 inhibition, either in vivo or ex vivo (primary neuronal cultures), was able to reduce amyloid secretion through moderate autophagy induction in neurons. The pharmacological prevention of autophagy in neurons augmented the Aβ secretion and reversed the effect of rapamycin, confirming the anti-amyloidogenic effects of autophagy in neurons. Inhibition of AMPK with compound C generated the expected decrease in autophagy induction, though surprisingly did not increase the Aβ secretion. In contrast, increased activity of AMPK with metformin, AICAR, 2DG, or by gene overexpression did not enhance autophagy but had different effects on Aβ secretion: whereas metformin and 2DG diminished the secreted Aβ levels, AICAR and PRKAA1/AMPK gene overexpression increased them. We conclude that AMPK has a significantly different role in primary neurons than in other reported cells, lacking a direct effect on autophagy-dependent amyloidosis.Abbreviations: 2DG: 2-deoxy-D-glucose; Aβ: β-amyloid; ACACA: acetyl-CoA carboxylase alpha; ACTB: actin beta; AD: Alzheimer disease; AICAR: 5-aminoimidazole-4-carboxamide-1-β-riboside; AKT: AKT kinases group (AKT1 [AKT serine/threonine kinase 1], AKT2 and AKT3); AMPK: adenosine 5'-monophosphate (AMP)-activated protein kinase; APP: amyloid beta precursor protein; APP/PSEN1: B6.Cg-Tg (APP^Swe, PSEN1dE9) 85Dbo/J; ATG: autophagy related; ATP: adenosine triphosphate; BafA1: bafilomycin A₁; CA: constitutively active; CGN: cerebellar granule neuron; CoC/compound C: dorsommorphin dihydrochloride; ELISA: enzyme-linked immunosorbent assay; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; Gmax: GlutaMAX™; IN1: PIK3C3/VPS34-IN1; KI: kinase-inactive; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3; MAPT/TAU: microtubule associated protein tau; Metf: metformin; MRT: MRT68921; MTORC1: mechanistic target of rapamycin kinase complex 1; NBR1: NBR1 autophagy cargo receptor; PRKAA: 5'-AMP-activated protein kinase catalytic subunit alpha; PtdIns3K: phosphatidylinositol 3-kinase; Rapa: rapamycin; RPS6KB1/S6K: ribosomal protein S6 (RPS6) kinase polypeptide 1; SCR: scramble; SQSTM1/p62: sequestosome 1; ULK1/2: unc-51 like autophagy activating kinase 1/2; WT: wild type.

Caloric Restriction Mimetic 2-Deoxyglucose Alleviated Inflammatory Lung Injury via Suppressing Nuclear Pyruvate Kinase M2-Signal Transducer and Activator of Transcription 3 Pathway

Inflammation is an energy-intensive process, and caloric restriction (CR) could provide anti-inflammatory benefits. CR mimetics (CRM), such as the glycolytic inhibitor 2-deoxyglucose (2-DG), mimic the beneficial effects of CR without inducing CR-related physiologic disturbance. This study investigated the potential anti-inflammatory benefits of 2-DG and the underlying mechanisms in mice with lipopolysaccharide (LPS)-induced lethal endotoxemia. The results indicated that pretreatment with 2-DG suppressed LPS-induced elevation of tumor necrosis factor alpha and interleukin 6. It also suppressed the upregulation of myeloperoxidase, attenuated Evans blue leakage, alleviated histological abnormalities in the lung, and improved the survival of LPS-challenged mice. Treatment with 2-DG had no obvious effects on the total level of pyruvate kinase M2 (PKM2), but it significantly suppressed LPS-induced elevation of PKM2 in the nuclei. Prevention of PKM2 nuclear accumulation by ML265 mimicked the anti-inflammatory benefits of 2-DG. In addition, treatment with 2-DG or ML265 suppressed the phosphorylation of nuclear signal transducer and activator of transcription 3 (STAT3). Inhibition of STAT3 by stattic suppressed LPS-induced inflammatory injury. Interestingly, posttreatment with 2-DG at the early stage post-LPS challenge also improved the survival of the experimental animals. This study found that treatment with 2-DG, a representative CRM, provided anti-inflammatory benefits in lethal inflammation. The underlying mechanisms included suppressed nuclear PKM2-STAT3 pathway. These data suggest that 2-DG might have potential value in the early intervention of lethal inflammation.

Defective glycolysis and the use of 2-deoxy-D-glucose in polycystic kidney disease: from animal models to humans

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited renal disease characterized by bilateral renal cyst formation. ADPKD is one of the most common rare disorders, accounting for ~10% of all patients with end-stage renal disease (ESRD). ADPKD is a chronic disorder in which the gradual expansion of cysts that form in a minority of nephrons eventually causes loss of renal function due to the compression and degeneration of the surrounding normal parenchyma. Numerous deranged pathways have been identified in the cyst-lining epithelia, prompting the design of potential therapies. Several of these potential treatments have proved effective in slowing down disease progression in pre-clinical animal studies, while only one has subsequently been proven to effectively slow down disease progression in patients, and it has recently been approved for therapy in Europe, Canada and Japan. Among the affected cellular functions and pathways, recent investigations have described metabolic derangement in ADPKD as a major trait offering additional opportunities for targeted therapies. In particular, increased aerobic glycolysis (the Warburg effect) has been described as a prominent feature of ADPKD kidneys and its inhibition using the glucose analogue 2-deoxy-D-glucose (2DG) proved effective in slowing down disease progression in preclinical models of the disease. At the same time, previous clinical experiences have been reported with 2DG, showing that this compound is well tolerated in humans with minimal and reversible side effects. In this work, we review the literature and speculate that 2DG could be a good candidate for a clinical trial in humans affected by ADPKD.