It has been reported that some small noncoding RNAs are involved in the regulation of insulin sensitivity. However, whether long noncoding RNAs also participate in the regulation of insulin sensitivity is still largely unknown. We identified and characterized a long noncoding RNA, regulator of insulin sensitivity and autophagy (Risa), which is a poly(A) + cytoplasmic RNA. Overexpression of Risa in mouse primary hepatocytes or C2C12 myotubes attenuated insulin-stimulated phosphorylation of insulin receptor, Akt, and Gsk3b, and knockdown of Risa alleviated insulin resistance. Further studies showed that overexpression of Risa in hepatocytes or myotubes decreased autophagy, and knockdown of Risa up-regulated autophagy. Moreover, knockdown of Atg7 or -5 significantly inhibited the effect of knockdown of Risa on insulin resistance, suggesting that knockdown of Risa alleviated insulin resistance via enhancing autophagy. In addition, tail vein injection of adenovirus to knock down Risa enhanced insulin sensitivity and hepatic autophagy in both C57BL/6 and ob/ob mice. Taken together, the data demonstrate that Risa regulates insulin sensitivity by affecting autophagy and suggest that Risa is a potential target for treating insulin-resistance-related
Cadmium (Cd), a toxic environmental contaminant, induces neurodegenerative disorders. Resveratrol, a natural product, has been found to exert neuroprotective effects. However, little is known regarding the effect of resveratrol on Cd-evoked neurotoxicity. Here, we show that resveratrol effectively reversed Cd-elicited cell viability reduction, morphological change, nuclear fragmentation and condensation, as well as activation of caspase-3 in neuronal cells, implying neuroprotection against Cd-poisoning by resveratrol. Further research revealed that both c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinases 1/2 (Erk1/2) were involved in the inhibitory effect of resveratrol on Cd-induced cell death, as selective inhibitors of Erk1/2 (U0126) and JNK (SP600125), or over-expression of dominant negative mitogen-activated protein kinase kinase 1 (MKK1) or dominant negative c-Jun potentiated resveratrol's prevention of Cd-induced phosphorylation of JNK and Erk1/2, as well as cell death in neuronal cells. Interestingly, resveratrol potently rescued the cells from Cd-induced suppression of protein phosphatases 2A (PP2A) and 5 (PP5) activity. Over-expression of PP2A or PP5 strengthened the inhibitory effects of resveratrol on Cd-induced activation of Erk1/2 and/or JNK, as well as cell death. The results indicate that resveratrol prevents Cd-induced activation of Erk1/ 2 and JNK pathways and neuronal cell death in part via activating PP2A and PP5. Our findings strongly support the notion that resveratrol may serve as a potential therapeutic agent in the prevention of Cd-induced neurodegenerative diseases. Keywords: cadmium, mitogen-activated protein kinase, neuronal cells, protein phosphatase 2A, protein phosphatase 5, resveratrol.
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