Circadian misalignment induces insulin resistance in both human and animal models, and skeletal muscle is the largest organ response to insulin. However, how circadian clock regulates muscle insulin sensitivity and the underlying molecular mechanisms are still largely unknown. Here we show circadian locomotor output cycles kaput (CLOCK) and brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein (BMAL)-1, two core circadian transcription factors, are down-regulated in insulin-resistant C2C12 myotubes and mouse skeletal muscle. Furthermore, insulin signaling is attenuated in the skeletal muscle of Clock(Δ19/Δ19) mice, and knockdown of CLOCK or BMAL1 by small interfering RNAs induces insulin resistance in C2C12 myotubes. Consistently, ectopic expression of CLOCK and BMAL1 improves insulin sensitivity in C2C12 myotubes. Moreover, CLOCK and BMAL1 regulate the expression of sirtuin 1 (SIRT1), an important regulator of insulin sensitivity, in C2C12 myotubes and mouse skeletal muscle, and two E-box elements in Sirt1 promoter are responsible for its CLOCK- and BMAL1-dependent transcription in muscle cells. Further studies show that CLOCK and BMAL1 regulate muscle insulin sensitivity through SIRT1. In addition, we find that BMAL1 and SIRT1 are decreased in the muscle of mice maintained in constant darkness, and resveratrol supplementation activates SIRT1 and improves insulin sensitivity. All these data demonstrate that CLOCK and BMAL1 regulate muscle insulin sensitivity via SIRT1, and activation of SIRT1 might be a potential valuable strategy to attenuate muscle insulin resistance related to circadian misalignment.

Changes in adenosine triphosphate (ATP) and peroxynitrite (ONOO − ) concentrations have been correlated in a number of diseases including ischemia-reperfusion injury and drug-induced liver injury. Herein, we report the development of a fluorescent probe ATP-LW, which enables the simultaneous detection of ONOO − and ATP. ONOO − selectively oxidizes the boronate pinacol ester of ATP-LW to afford the fluorescent 4-hydroxy-1,8-naphthalimide product NA-OH (λ ex = 450 nm, λ em = 562 nm or λ ex = 488 nm, λ em = 568 nm). In contrast, the binding of ATP to ATP-LW induces the spirolactam ring opening of rhodamine to afford a highly emissive product (λ ex = 520 nm, λ em = 587 nm). Due to the differences in emission between the ONOO − and ATP products, ATP-LW allows ONOO − levels to be monitored in the green channel (λ ex = 488 nm, λ em = 500−575 nm) and ATP concentrations in the red channel (λ ex = 514 nm, λ em = 575−650 nm). The use of ATP-LW as a combined ONOO − and ATP probe was demonstrated using hepatocytes (HL-7702 cells) in cellular imaging experiments. Treatment of HL-7702 cells with oligomycin A (an inhibitor of ATP synthase) resulted in a reduction of signal intensity in the red channel and an increase in that of the green channel as expected for a reduction in ATP concentrations. Similar fluorescence changes were seen in the presence of SIN-1 (an exogenous ONOO − donor).

Various compounds with sulfur or diamine structure have been served as efficient reducing agents to convert graphene oxide to reduced graphene oxide. In this work, we used thiourea with both sulfur and diamine structure to synthesize reduced graphene oxide by the general wet chemical reduction method. The effective deoxygenation of graphene oxide was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy analysis and Raman spectroscopy. The as-prepared reduced graphene oxide is consisted of few-layered (no more than seven) and over 60% single-layered graphene sheet determined by atomic force microscopy and transmission electron microscopy. It also exhibits good dispersion in organic solvents such as ethanol and N,N-dimethylformamide, which is useful for the further modification of graphene and preparation of novel nanocomposites. This newly found reducing agent is of low toxicity and nonvolatile, which makes the reduction much safer.

In this work, zero-valent iron powder (Fe(0)) was used to catalyze the polymerization of methyl methacrylate (MMA) in the presence of a reversible addition-fragmentation chain transfer (RAFT) agent, 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) without any ligand at ambient temperature. The polymerization behavior complied with the features of typical "living"/controlled radical polymerizations. The number-average molecular weights of poly(methyl methacrylate) increased linearly with monomer conversion, while maintaining narrow molecular weight distributions (M w /M n <1.50). Even at low concentration of Fe(0), such as at [MMA] 0 :[CPDN] 0 :[Fe(0)] 0 = 200:1:0.2, the polymerization was also controllable; however, it presented a depressed polymerization rate and a prolonged induction period (about 12 h). The polymerization rate also decreased with increasing of CPDN concentration. From experimental results, it was deduced that the initiating species were derived from the cooperative reaction of Fe(0) and CPDN, in which CPDN acted as a pseudohalide alkyl initiator. The control process was supposed to proceed via a synactic mechanism. One mechanism was the synergic mediation by Fe(0) and CPDN, in which Fe(III) formed in situ acted as an deactivator, however, this deactivation was supposed to be ineffective. The other was the RAFT mechanism with CPDN as the RAFT agent, which may dominate the whole control.

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