Origins and evolving functionalities of tRNA-derived small RNAs.

Transfer RNA (tRNA)-derived small RNAs (tsRNAs) are among the most ancient small RNAs in all domains of life and are generated by the cleavage of tRNAs. Emerging studies have begun to reveal the versatile roles of tsRNAs in fundamental biological processes, including gene silencing, ribosome biogenesis, retrotransposition, and epigenetic inheritance, which are rooted in tsRNA sequence conservation, RNA modifications, and protein-binding abilities. We summarize the mechanisms of tsRNA biogenesis and the impact of RNA modifications, and propose how thinking of tsRNA functionality from an evolutionary perspective urges the expansion of tsRNA research into a wider spectrum, including cross-tissue/cross-species regulation and harnessing of the 'tsRNA code' for precision medicine.

Down-regulation of Risa improves insulin sensitivity by enhancing autophagy.

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 Gsk3ß, 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 diseases.-Wang, Y., Hu, Y., Sun, C., Zhuo, S., He, Z., Wang, H., Yan, M., Liu, J., Luan, Y., Dai, C., Yang, Y., Huang, R., Zhou, B., Zhang, F., Zhai, Q. Down-regulation of Risa improves insulin sensitivity by enhancing autophagy.

A high-throughput quantitative approach reveals more small RNA modifications in mouse liver and their correlation with diabetes.

Studies of RNA modification are usually focused on tRNA. However the modification of other small RNAs, including 5.8S rRNA, 5S rRNA, and small RNA sized at 10-60 nt, is still largely unknown. In this study, we established an efficient method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) to simultaneously identify and quantify more than 40 different types of nucleosides in small RNAs. With this method, we revealed 23 modified nucleosides of tRNA from mouse liver, and 6 of them were observed for the first time in eukaryotic tRNA. Moreover, 5 and 4 modified nucleosides were detected for the first time in eukaryotic 5.8S and 5S rRNA, respectively, and 22 modified nucleosides were identified in the small RNAs sized at 30-60 or 10-30 nt. Interestingly, two groups of 5S rRNA peaks were observed when analyzed by HPLC, and the abundance of modified nucleosides is significantly different between the two groups of peaks. Further studies show that multiple modifications in small RNA from diabetic mouse liver are significantly increased or decreased. Taken together, our data revealed more modified nucleosides in various small RNAs and showed the correlation of small RNA modifications with diabetes. These results provide new insights to the role of modifications of small RNAs in their stability, biological functions, and correlation with diseases.

PANDORA-seq expands the repertoire of regulatory small RNAs by overcoming RNA modifications.

Although high-throughput RNA sequencing (RNA-seq) has greatly advanced small non-coding RNA (sncRNA) discovery, the currently widely used complementary DNA library construction protocol generates biased sequencing results. This is partially due to RNA modifications that interfere with adapter ligation and reverse transcription processes, which prevent the detection of sncRNAs bearing these modifications. Here, we present PANDORA-seq (panoramic RNA display by overcoming RNA modification aborted sequencing), employing a combinatorial enzymatic treatment to remove key RNA modifications that block adapter ligation and reverse transcription. PANDORA-seq identified abundant modified sncRNAs-mostly transfer RNA-derived small RNAs (tsRNAs) and ribosomal RNA-derived small RNAs (rsRNAs)-that were previously undetected, exhibiting tissue-specific expression across mouse brain, liver, spleen and sperm, as well as cell-specific expression across embryonic stem cells (ESCs) and HeLa cells. Using PANDORA-seq, we revealed unprecedented landscapes of microRNA, tsRNA and rsRNA dynamics during the generation of induced pluripotent stem cells. Importantly, tsRNAs and rsRNAs that are downregulated during somatic cell reprogramming impact cellular translation in ESCs, suggesting a role in lineage differentiation.

Author Correction: PANDORA-seq expands the repertoire of regulatory small RNAs by overcoming RNA modifications.

A Correction to this paper has been published: https://doi.org/10.1038/s41556-021-00687-w.

Anti-oral Microbial Flavanes from Broussonetia papyrifera Under the Guidance of Bioassay.

A new flavane, bropapyriferol (1), and eleven known ones were isolated from the EtOAc part of Broussonetia papyrifera under the guidance of bioassay. The structure of compound 1 was determined by extensive 1D and 2D NMR, [α]D spectroscopic data and quantum computation. Daphnegiravan F (2) and 5,7,3',4'-tetrahydroxy-3-methoxy-8,5'-diprenylflavone (3) showed significantly anti-oral microbial activity against five Gram-positive strains and three Gram-negative strains in vitro. Especially, compound 3 was more potent in suppressing Actinomyces naeslundii and Porphyromonas gingivalis (MIC = 1.95 ppm) than the positive control, triclosan.

Sarm1 Gene Deficiency Attenuates Diabetic Peripheral Neuropathy in Mice.

Diabetic peripheral neuropathy (DPN) is the most common complication in both type 1 and type 2 diabetes, but any treatment toward the development of DPN is not yet available. Axon degeneration is an early feature of many peripheral neuropathies, including DPN. Delay of axon degeneration has beneficial effects on various neurodegenerative diseases, but its effect on DPN is yet to be elucidated. Deficiency of Sarm1 significantly attenuates axon degeneration in several models, but the effect of Sarm1 deficiency on DPN is still unclear. In this study, we show that Sarm1 knockout mice exhibit normal glucose metabolism and pain sensitivity, and deletion of the Sarm1 gene alleviates hypoalgesia in streptozotocin-induced diabetic mice. Moreover, Sarm1 gene deficiency attenuates intraepidermal nerve fiber loss in footpad skin; alleviates axon degeneration, the change of g-ratio in sciatic nerves, and NAD+ decrease; and relieves axonal outgrowth retardation of dorsal root ganglia from diabetic mice. In addition, Sarm1 gene deficiency markedly diminishes the changes of gene expression profile induced by streptozotocin in the sciatic nerve, especially some abundant genes involved in neurodegenerative diseases. These findings demonstrate that Sarm1 gene deficiency attenuates DPN in mice and suggest that slowing down axon degeneration is a potential promising strategy to combat DPN.

Short-term tamoxifen treatment has long-term effects on metabolism in high-fat diet-fed mice with involvement of Nmnat2 in POMC neurons.

Short-term tamoxifen treatment has effects on lipid and glucose metabolism in mice fed chow. However, its effects on metabolism in mice fed high-fat diet (HFD) and the underlying mechanisms are unclear. Here, we show that tamoxifen treatment for 5 days decreases fat mass for as long as 18 weeks in mice fed HFD. Tamoxifen alters mRNA levels of some genes involved in lipid metabolism in white adipose tissue and improves glucose and insulin tolerance as well as hepatic insulin signaling for 12-20 weeks. Proopiomelanocortin (POMC) neuron-specific deletion of nicotinamide mononucleotide adenylyltransferase 2 (Nmnat2) attenuates the effects of tamoxifen on glucose and insulin tolerance. These data demonstrate that short-term injection of tamoxifen has long-term effects on lipid and glucose metabolism in HFD mice with involvement of Nmnat2 in POMC neurons.

Dnmt2 mediates intergenerational transmission of paternally acquired metabolic disorders through sperm small non-coding RNAs.

The discovery of RNAs (for example, messenger RNAs, non-coding RNAs) in sperm has opened the possibility that sperm may function by delivering additional paternal information aside from solely providing the DNA 1 . Increasing evidence now suggests that sperm small non-coding RNAs (sncRNAs) can mediate intergenerational transmission of paternally acquired phenotypes, including mental stress2,3 and metabolic disorders4-6. How sperm sncRNAs encode paternal information remains unclear, but the mechanism may involve RNA modifications. Here we show that deletion of a mouse tRNA methyltransferase, DNMT2, abolished sperm sncRNA-mediated transmission of high-fat-diet-induced metabolic disorders to offspring. Dnmt2 deletion prevented the elevation of RNA modifications (m5C, m2G) in sperm 30-40 nt RNA fractions that are induced by a high-fat diet. Also, Dnmt2 deletion altered the sperm small RNA expression profile, including levels of tRNA-derived small RNAs and rRNA-derived small RNAs, which might be essential in composing a sperm RNA 'coding signature' that is needed for paternal epigenetic memory. Finally, we show that Dnmt2-mediated m5C contributes to the secondary structure and biological properties of sncRNAs, implicating sperm RNA modifications as an additional layer of paternal hereditary information.

Hemin Improves Insulin Sensitivity and Lipid Metabolism in Cultured Hepatocytes and Mice Fed a High-Fat Diet.

Hemin is a breakdown product of hemoglobin. It has been reported that the injection of hemin improves lipid metabolism and insulin sensitivity in various genetic models. However, the effect of hemin supplementation in food on lipid metabolism and insulin sensitivity is still unclear, and whether hemin directly affects cellular insulin sensitivity is yet to be elucidated. Here we show that hemin enhances insulin-induced phosphorylation of insulin receptors, Akt, Gsk3ß, FoxO1 and cytoplasmic translocation of FoxO1 in cultured primary hepatocytes under insulin-resistant conditions. Furthermore, hemin diminishes the accumulation of triglyceride and increases in free fatty acid content in primary hepatocytes induced by palmitate. Oral administration of hemin decreases body weight, energy intake, blood glucose and triglyceride levels, and improves insulin and glucose tolerance as well as hepatic insulin signaling and hepatic steatosis in male mice fed a high-fat diet. In addition, hemin treatment decreases the mRNA and protein levels of some hepatic genes involved in lipogenic regulation, fatty acid synthesis and storage, and increases the mRNA level and enzyme activity of CPT1 involved in fatty acid oxidation. These data demonstrate that hemin can improve lipid metabolism and insulin sensitivity in both cultured hepatocytes and mice fed a high-fat diet, and show the potential beneficial effects of hemin from food on lipid and glucose metabolism.

Sperm tsRNAs and acquired metabolic disorders.

Many findings support the hypothesis that metabolic changes associated with environmental factors can be transmitted from father to offspring. The molecular mechanisms underlying the intergenerational transmission of metabolic changes remain to be fully explored. These acquired metabolic disorders in offspring may be partially explained by some potential epigenetic information carriers such as DNA methylation, histone modification and small non-coding RNAs. Recent evidence shows that sperm tRNA-derived small RNAs (tsRNAs) as a type of paternal epigenetic information carrier may mediate intergenerational inheritance. In this review, we provide current knowledge of a father's influence on metabolic disorders in subsequent generations and discuss the roles of sperm tsRNAs and their modifications in paternal epigenetic information transmission.

CLOCK and BMAL1 Regulate Muscle Insulin Sensitivity via SIRT1 in Male Mice.

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.

Sperm tsRNAs contribute to intergenerational inheritance of an acquired metabolic disorder.

Increasing evidence indicates that metabolic disorders in offspring can result from the father's diet, but the mechanism remains unclear. In a paternal mouse model given a high-fat diet (HFD), we showed that a subset of sperm transfer RNA-derived small RNAs (tsRNAs), mainly from 5' transfer RNA halves and ranging in size from 30 to 34 nucleotides, exhibited changes in expression profiles and RNA modifications. Injection of sperm tsRNA fractions from HFD males into normal zygotes generated metabolic disorders in the F1 offspring and altered gene expression of metabolic pathways in early embryos and islets of F1 offspring, which was unrelated to DNA methylation at CpG-enriched regions. Hence, sperm tsRNAs represent a paternal epigenetic factor that may mediate intergenerational inheritance of diet-induced metabolic disorders.

WldS enhances insulin transcription and secretion via a SIRT1-dependent pathway and improves glucose homeostasis.

UNLABELLED: OBJECTIVE Wld(S) (Wallerian degeneration slow), a fusion protein from a spontaneous mutation containing full-length nicotinamide mononucleotide adenylyltransferase 1, has NAD biosynthesis activity and protects axon from degeneration robustly. NAD biosynthesis is also implicated in insulin secretion in ß-cells. The aim of this study was to investigate the effect of Wld(S) on ß-cells and glucose homeostasis. RESEARCH DESIGN AND METHODS: Using the Wld(S) mice, we measured the expression of Wld(S) in pancreas and analyzed the effect of Wld(S) on glucose homeostasis. The direct effect of Wld(S) on insulin transcription and secretion and the related mechanisms was measured in isolated islets or ß-cell lines. Silent information regulator 1 (SIRT1), an NAD-dependent protein deacetylase, is involved in insulin secretion. Thus, Wld(S) mice with SIRT1 deficiency were generated to study whether the SIRT1-dependent pathway is involved. RESULTS: Wld(S) is highly expressed in the pancreas and improves glucose homeostasis. Wld(S) mice are resistant to high-fat diet-induced glucose intolerance and streptozotocin (STZ)-induced hyperglycemia. Wld(S) increases insulin transcription dependent on its NAD biosynthesis activity and enhances insulin secretion. SIRT1 is required for the improved insulin transcription, secretion, and resistance to STZ-induced hyperglycemia caused by Wld(S). Moreover, Wld(S) associates with SIRT1 and increases NAD levels in the pancreas, causing the enhanced SIRT1 activity to downregulate uncoupling protein 2 (UCP2) expression and upregulate ATP levels. CONCLUSIONS: Our results demonstrate that Wld(S) combines an insulinotropic effect with protection against ß-cell failure and suggest that enhancing NAD biosynthesis in ß-cells to increase SIRT1 activity could be a potential therapeutic approach for diabetes.

Periglaucines A-D, anti-HBV and -HIV-1 alkaloids from Pericampylus glaucus.

Four new hasubanane-type alkaloids, periglaucines A-D (1-4), and three known alkaloids, norruffscine (5), (-)-8-oxotetrahydropalmatine (6), and (-)-8-oxocanadine (7), were isolated from the aerial parts of Pericampylus glaucus. Their structures were elucidated on the basis of extensive NMR and EIMS data, and that of periglaucine A (1) was confirmed by single-crystal X-ray diffraction. Alkaloids 1-4 inhibited hepatitis B virus (HBV) surface antigen (HBsAg) secretion in Hep G2.2.15 cells. (-)-8-Oxotetrahydropalmatine (6) possessed a high selectivity index (SI = 22.4) for HBsAg secretion of the Hep G2.2.15 cell line with an IC(50) value of 0.14 mM. Norruffscine (5) and (-)-8-oxotetrahydropalmatine (6) exhibited inhibitory activity against human immunodeficiency virus (HIV-1) with EC(50) values of 10.9 and 14.1 microM in C8166 cells (SI = 45.7 and 18.8), respectively.

Two new alkaloids and active anti-hepatitis B virus constituents from Hypserpa nitida.

Two new alkaloids, hypserpanines A and B (1, 11), together with eleven known compounds, phenolbetain (2), acutumine (3), acutumidine (4), dechloroacutumine (5), dauricumine (6), dauricumidine (7), pronuciferine (8), glaziovine (9), S-reticuline (10), magnoflorine (12) and laurifoline(13), were isolated from Hypserpa nitida Miers. (Menispermaceae) and chemically elucidated through spectral analyses. All the isolated alkaloids were evaluated for their anti-HBV activities in vitro using the HBV transfected Hep G2.2.15 cell line. The most active compound, dauricumidine (7), exhibited an IC(50) value of 0.450 mM (SI=4.13) on hepatitis B virus (HBV) surface antigen (HBsAg) secretion of the Hep G2.2.15 cell line.