Hepatitis C virus induced insulin resistance impairs response to anti viral therapy

Hepatitis C virus (HCV) infection is an important risk factor for insulin resistance (IR). The latter is the pathogenic foundation underlying metabolic syndrome, steatosis and cirrhosis, and possibly hepatocellular carcinoma (HCC). The interplay between genetic and environmental risk factors ultimately leads to the development of IR. Obesity is considered a major risk factor, with dysregulation of levels of secreted adipokines from distended adipose tissue playing a major role in IR. HCV-induced IR may be due to the HCV core protein inducing proteasomal degradation of insulin receptor substrates 1 and 2, blocking intracellular insulin signaling. The latter is mediated by increased levels of both tumour necrosis factor-α (TNF-α) and suppressor of cytokine signaling 3 (SOC-3). IR, through different mechanisms, plays a role in the development of steatosis and its progression to steatohepatitis, cirrhosis and even HCC. In addition, IR has a role in impairing TNF signaling cascade, which in turn blocks STAT-1 translocation and interferon stimulated genes production avoiding the antiviral effect of interferon.

Response and resistance of cereal crops to pathogens

The special topic of the two papers is the systemic acquired resistance （SAR） and pathogenesis-related protein genes （PR）. SAR is an enhanced resistance against further potential parasite beyond the initial infection site, which can be induced by either pathogen infection or exogenous inducer, including synthetic chemicals and natural prod- ucts. As a ＂whole-plant＂ resistance defense, SAR confers broad-spectrum immunity to widely diverse pathogenic microorganisms, such as viruses, bacteria and fungi for a relatively long lasting period. Convincingly, it is a promising way to prevent crop diseases by activating the plants＇ own natural defenses via application of chemical inducers or creating resistant wheat cultivars.

Redox-stress response resistance(RRR)mediated by hyperoxidation of peroxiredoxin 2 in senescent cells

Aging is closely related to redox regulation.In our previous work,we proposed a new concept,“redox-stress response capacity(RRC),”and found that the decline in RRC was a dynamic characteristic of aging.However,the mechanism of RRC decline during aging remains unknown.In this study,using the senescent human fibroblast cell model and Caenorhabditis elegans model,we identified that peroxiredoxin 2(PRDX2),as a hydrogen peroxide(H_(2)O_(2))sensor,was involved in mediating RRC.PRDX2 knockdown led to a decline of RRC and accelerated senescence in fibroblasts and prdx-2 mutant C.elegans also showed decreased RRC.The mechanism study showed that the decreased sensor activity of PRDX2 was related to the increase in hyperoxidation of PRDX2 in senescent cells.Moreover,the level of PRDX2 hyperoxidation also increased in old C.elegans.Simultaneous overexpression of both PRDX2 and sulfiredoxin(SRX)rescued the reduced RRC and delayed senescence.The increase in PRDX2 hyperoxidation in senescent cells led to a decrease in its sensor activity,resulting in the decreased cellular response to H_(2)O_(2),which is similar to the mechanism of insulin resistance due to the lower insulin receptor sensitivity.Treatment of young cells with a high level of H_(2)O_(2)to induce a higher level of PRDX2-SO_(3) resulted in mimicking the RRC decline in senescent cells,which is also similar to a model of insulin resistance induced by high levels of insulin.All these results thrillingly indicate that there is an insulin-resistance-like phenomenon in senescent cells,we named it redox-stress response resistance,RRR.RRR in senescent cells is an important new discovery that explains RRC decline during aging and reveals the internal relationship between redox regulation and aging from a new perspective.

Ab-Induced Insulin Resistance and the Effects of Insulin on the Cholesterol Synthesis Pathway and Ab Secretion in Neural Cells

Alzheimer＇s disease（AD） is characterized by amyloid-b（Ab） toxicity,tau pathology,insulin resistance,neuroinflammation,and dysregulation of cholesterol homeostasis,all of which play roles in neurodegeneration.Insulin has polytrophic effects on neurons and may be at the center of these pathophysiological changes.In this study,we investigated possible relationships among insulin signaling and cholesterol biosynthesis,along with the effects of Ab42 on these pathways in vitro.We found that neuroblastoma 2a（N2a） cells transfected with the human gene encoding amyloid-b protein precursor（Ab PP）（N2aAb PP） produced Ab and exhibited insulin resistance by reduced p-Akt and a suppressed cholesterol-synthesis pathway following insulin treatment,and by increased phosphorylation of insulin receptor subunit-1 at serine 612（p-IRS-S612） as compared to parental N2 a cells.Treatment of human neuroblastoma SH-SY5 Y cells with Ab42 also increased p-IRS-S612,suggesting that Ab42 is responsible for insulin resistance.The insulin resistance was alleviated when N2a-Ab PP cells were treated with higher insulin concentrations.Insulin increased Ab release from N2 aAb PP cells,by which it may promote Ab clearance.Insulin increased cholesterol-synthesis gene expression in SHSY5 Y and N2 a cells,including 24-dehydrocholesterol reductase（DHCR24） and 3-hydroxy-3-methyl-glutaryl-Co A reductase（HMGCR） through sterol-regulatory element-binding protein-2（SREBP2）.While Ab42-treated SH-SY5 Y cells exhibited increased HMGCR expression and c-Jun phosphorylation as pro-inflammatory responses,they also showed down-regulation of neuro-protective/antiinflammatory DHCR24.These results suggest that Ab42 may cause insulin resistance,activate JNK for c-Jun phosphorylation,and lead to dysregulation of cholesterol homeostasis,and that enhancing insulin signaling may relieve the insulin-resistant phenotype and the dysregulated cholesterol-synthesis pathway to promote Ab release for clearance from neural cells.