Modulation of SIRT1-foxo1 signaling axis by resveratrol: Implications in skeletal muscle aging and insulin resistance

© 2015 S. Karger AG, Basel. Aging individuals and diabetic patients often exhibit concomitant reductions of skeletal muscle mass/strength and insulin sensitivity, suggesting an intimate link between muscle aging and insulin resistance. Foxo1, a member of the FOXO transcription factor family, is an important player in insulin signaling due to its inhibitory role in glucose uptake and utilization in skeletal muscle. Phosphorylation of Foxo1 is thought to mitigate the transactivation of pyruvate dehydrogenase lipoamide kinase 4 (PDK4), which is a negative regulator of the glycolytic enzyme pyruvate dehydrogenase (PDH). In contrast, how aging would regulate acetylation/deacetylation machineries and glucose utilization in skeletal muscle through the Foxo1/PDH axis remains largely undetermined. Accumulating body of evidence have shown that resveratrol, a natural polyphenol in grapes and red wine, activates the longevity-related protein sirtuin 1 (SIRT1) and augments insulin sensitivity in addition to its well-documented effects on mitochondrial energetics. The present review summarizes the role of Foxo1/SIRT1 in insulin signaling in skeletal muscle and proposes the insight that activation of SIRT1 deacetylase activity to deacetylate and suppress the Foxo1-induced transactivation of PDK4 may represent an anti-hyperglycemic mechanism of resveratrol in aging skeletal muscle.Link_to_subscribed_fulltex

SIRT1-dependent myoprotective effects of resveratrol on muscle injury induced by compression

© 2015 Sin, Yung, Yip, Chan, Wong, Tam and Siu. Our current understanding on the molecular mechanisms by which sustained compression induces skeletal muscle injury is very limited. This study aimed to test the hypothesis that activation of SIRT1 by the natural antioxidant resveratrol could deactivate apoptotic and catabolic signaling in skeletal muscle exposed to moderate compression. Two cycles of 6-h constant pressure at 100 mmHg was applied to the tibialis region of right, but not left hindlimbs of Sprague Dawley rats pre-treated with DMSO (vehicle control) or resveratrol with/without sirtinol. Skeletal muscle tissues lying underneath and spatially corresponding to the compressed sites were collected for analyses. Resveratrol prevented the compression-induced manifestations of pathohistological damages including elevations of the number of interstitial nuclei and area of interstitial space and ameliorated oxidative damages measured as 4-hydroxy-2-nonenal (4HNE) and nitrotyrosine in skeletal muscle. In parallel, resveratrol augmented the expression level and activity of SIRT1 and phosphorylation levels of Foxo3a and Akt while suppressed the increases in protein abundances of p53, Bax, MAFbx, and ubiquitin, enzymatic activities of caspase 3 and 20S proteasome, and apoptotic DNA fragmentation in the compressed muscle. These favorable myoprotective effects of resveratrol were diminished upon pharmacological blockade of SIRT1 by using sirtinol. These novel data support the hypothesis that the anti-apoptotic and anti-catabolic effects of resveratrol on compression injury in skeletal muscle required the action of SIRT1.Link_to_subscribed_fulltex

Implications of MicroRNAs in the treatment of gefitinib-resistant non-small cell lung cancer

2015-2016 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

S100A8 and S100A9 Are Associated with Doxorubicin-Induced Cardiotoxicity in the Heart of Diabetic Mice

© 2016 Pei, Tam, Sin, Wang, Yung, Chan, Wong, Ying, Lai and Siu. Cardiomyopathy is a clinical problem that occurs in the hearts of type 2 diabetic patients as well as cancer patients undergoing doxorubicin chemotherapy. The number of diabetic cancer patients is increasing but surprisingly the cardiac damaging effects of doxorubicin, a commonly used chemotherapeutic drug, on diabetic hearts have not been well-examined. As the signaling mechanisms of the doxorubicin-induced cardiomyopathy in type 2 diabetic heart are largely unknown, this study examined the molecular signaling pathways that are responsible for the doxorubicin-induced cardiotoxicity in type 2 diabetic hearts. Male 14- to 18-week-old db/db mice were used as the type 2 diabetic model, and age-matched non-diabetic db/+ mice served as controls. The db/+ non-diabetic and db/db diabetic mice were randomly assigned to the following groups: db/+CON, db/+DOX-5d, db/+DOX-7d, db/dbCON, db/dbDOX-5d, and db/dbDOX-7d. Mice assigned to doxorubicin (DOX) group were exposed to an intraperitoneal (i.p.) injection of DOX at a dose of 15 mg/kg to induce cardiomyopathy. Mice in control (CON) groups were i.p. injected with the same volume of saline instead of DOX. Mice were euthanized by overdose of ketamine and xylazine 5 or 7 days after the DOX injection. Microarray analysis was adopted to examine the changes of the whole transcriptional profile in response to doxorubicin exposure in diabetic hearts. Ventricular fractional shortening was examined as an indicator of cardiac function by transthoracic echocardiography. The presence of diabetic cardiomyopathy in db/db mice was evident by the reduction of fractional shortening. There was a further impairment of cardiac contractile function 7 days after the DOX administration in db/db diabetic mice. According to our microarray analysis, we identified a panel of regulatory genes associated with cardiac remodeling, inflammatory response, oxidative stress, and metabolism in the DOX-induced cardiac injury in diabetic heart. The microarray results of selected genes were confirmed by real time PCR. Notably, S100A8 and S100A9 were found to have a unique specific expression pattern that was coincident with the DOX-induced cardiomyopathy in diabetic hearts. Correspondingly, NF-κB expression in diabetic hearts was increased together with the elevation of S100A8/9 and activation of p38 MAPK signaling after DOX administration, which induced cardiac inflammation as demonstrated by the elevation of cardiac IL-6 level. These findings provide novel pre-clinical information for revealing the S100A8/A9-associated molecular signaling pathways that mediate the doxorubicin-induced cardiotoxicity in diabetic hearts.Link_to_subscribed_fulltex

Green synthesis of Fe3O4 nanoparticles stabilized by a Garcinia mangostana fruit peel extract for hyperthermia and anticancer activities

Fe3O4 nanoparticles (Fe3O4 NPs) with multiple functionalities are intriguing candidates for various biomedical applications. Materials and Methods: This study introduced a simple and green synthesis of Fe3O4 NPs using a low-cost stabilizer of plant waste extract rich in polyphenols content with a well-known antioxidant property as well as anticancer ability to eliminate colon cancer cells. Herein, Fe3O4 NPs were fabricated via a facile co-precipitation method using the crude extract of Garcinia mangostana fruit peel as a green stabilizer at different weight percentages (1, 2, 5, and 10 wt.%). The samples were analyzed for magnetic hyperthermia and then in vitro cytotoxicity assay was performed. Results: The XRD planes of the samples were corresponding to the standard magnetite Fe3O4 with high crystallinity. From TEM analysis, the green synthesized NPs were spherical with an average size of 13.42±1.58 nm and displayed diffraction rings of the Fe3O4 phase, which was in good agreement with the obtained XRD results. FESEM images showed that the extract covered the surface of the Fe3O4 NPs well. The magnetization values for the magnetite samples were ranging from 49.80 emu/g to 69.42 emu/g. FTIR analysis verified the functional groups of the extract compounds and their interactions with the NPs. Based on DLS results, the hydrodynamic sizes of the Fe3O4 nanofluids were below 177 nm. Furthermore, the nanofluids indicated the zeta potential values up to −34.92±1.26 mV and remained stable during four weeks of storage, showing that the extract favorably improved the colloidal stability of the Fe3O4 NPs. In the hyperthermia experiment, the magnetic nanofluids showed the acceptable specific absorption rate (SAR) values and thermosensitive performances under exposure of various alternating magnetic fields. From results of in vitro cytotoxicity assay, the killing effects of the synthesized samples against HCT116 colon cancer cells were mostly higher compared to those against CCD112 colon normal cells. Remarkably, the Fe3O4 NPs containing 10 wt.% of the extract showed a lower IC50 value (99.80 μg/mL) in HCT116 colon cancer cell line than in CCD112 colon normal cell line (140.80 μg/mL). Discussion: This research, therefore, introduced a new stabilizer of Garcinia mangostana fruit peel extract for the biosynthesis of Fe3O4 NPs with desirable physiochemical properties for potential magnetic hyperthermia and colon cancer treatment

Disruption of the pro-oncogenic c-RAF–PDE8A complex represents a differentiated approach to treating KRAS–c-RAF dependent PDAC

Pancreatic ductal adenocarcinoma (PDAC) is considered the third leading cause of cancer mortality in the western world, offering advanced stage patients with few viable treatment options. Consequently, there remains an urgent unmet need to develop novel therapeutic strategies that can effectively inhibit pro-oncogenic molecular targets underpinning PDACs pathogenesis and progression. One such target is c-RAF, a downstream effector of RAS that is considered essential for the oncogenic growth and survival of mutant RAS-driven cancers (including KRASMT PDAC). Herein, we demonstrate how a novel cell-penetrating peptide disruptor (DRx-170) of the c-RAF–PDE8A protein–protein interaction (PPI) represents a differentiated approach to exploiting the c-RAF–cAMP/PKA signaling axes and treating KRAS–c-RAF dependent PDAC. Through disrupting the c-RAF–PDE8A protein complex, DRx-170 promotes the inactivation of c-RAF through an allosteric mechanism, dependent upon inactivating PKA phosphorylation. DRx-170 inhibits cell proliferation, adhesion and migration of a KRASMT PDAC cell line (PANC1), independent of ERK1/2 activity. Moreover, combining DRx-170 with afatinib significantly enhances PANC1 growth inhibition in both 2D and 3D cellular models. DRx-170 sensitivity appears to correlate with c-RAF dependency. This proof-of-concept study supports the development of DRx-170 as a novel and differentiated strategy for targeting c-RAF activity in KRAS–c-RAF dependent PDAC

Protein-coding variants implicate novel genes related to lipid homeostasis contributing to body-fat distribution.

Body-fat distribution is a risk factor for adverse cardiovascular health consequences. We analyzed the association of body-fat distribution, assessed by waist-to-hip ratio adjusted for body mass index, with 228,985 predicted coding and splice site variants available on exome arrays in up to 344,369 individuals from five major ancestries (discovery) and 132,177 European-ancestry individuals (validation). We identified 15 common (minor allele frequency, MAF ≥5%) and nine low-frequency or rare (MAF <5%) coding novel variants. Pathway/gene set enrichment analyses identified lipid particle, adiponectin, abnormal white adipose tissue physiology and bone development and morphology as important contributors to fat distribution, while cross-trait associations highlight cardiometabolic traits. In functional follow-up analyses, specifically in Drosophila RNAi-knockdowns, we observed a significant increase in the total body triglyceride levels for two genes (DNAH10 and PLXND1). We implicate novel genes in fat distribution, stressing the importance of interrogating low-frequency and protein-coding variants

Neuron-oligodendrocyte potassium shuttling at nodes of Ranvier protects against

Multiple sclerosis (MS) is a progressive inflammatory demyelinating disease of the CNS. Increasing evidence suggests that vulnerable neurons in MS exhibit fatal metabolic exhaustion over time, a phenomenon hypothesized to be caused by chronic hyperexcitability. Axonal Kv7 (outward-rectifying) and oligodendroglial Kir4.1 (inward-rectifying) potassium channels have important roles in regulating neuronal excitability at and around the nodes of Ranvier. Here, we studied the spatial and functional relationship between neuronal Kv7 and oligodendroglial Kir4.1 channels and assessed the transcriptional and functional signatures of cortical and retinal projection neurons under physiological and inflammatory demyelinating conditions. We found that both channels became dysregulated in MS and experimental autoimmune encephalomyelitis (EAE), with Kir4.1 channels being chronically downregulated and Kv7 channel subunits being transiently upregulated during inflammatory demyelination. Further, we observed that pharmacological Kv7 channel opening with retigabine reduced neuronal hyperexcitability in human and EAE neurons, improved clinical EAE signs, and rescued neuronal pathology in oligodendrocyte-Kir4.1-deficient (OL-Kir4.1-deficient) mice. In summary, our findings indicate that neuron-OL compensatory interactions promoted resilience through Kv7 and Kir4.1 channels and identify pharmacological activation of nodal Kv7 channels as a neuroprotective strategy against inflammatory demyelination

Hundreds of variants clustered in genomic loci and biological pathways affect human height

Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P < 0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways.

The Subcutaneous Air-Pouch Model of Synovium and the Inflammatory Response to Heat Aggregated Gammaglobulin

Subcutaneous injection of sterile air in rodents results in the formation of an air pouch with a lining morphologically similar to synovium (Edwards et al., 1981). We extended the comparison between pouch and synovial tissue and confirmed broad similarities in structure and function but also noted important differences. The air pouch was used to study the time course of the acute inflammatory response to heat aggregated human IgG. Saline washout of the pouch allowed simultaneous measurement of cellular and mediator components of the inflammatory exudate. The aggregates were rapidly phagocytosed by the pouch lining cells, resulting in acute inflammation characterised by polymorphonuclear leucocyte infiltration with peak numbers in the exudate at 12 hours, temporally dissociated from the earlier peak of PGE2 at 3 hours