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Pressure-induced injury (PI), such as a pressure ulcer, in patients with limited mobility is a healthcare issue worldwide. PI is an injury to skin and its underlying tissue such as skeletal muscle. Muscle compression, composed of mechanical deformation of muscle and external load, leads to localized ischemia and subsequent unloading reperfusion and, hence, a pressure ulcer in bed-bound patients. Although the gross factors involved in PI have been identified, little is known about the exact disease mechanism or its links to apoptosis, autophagy and inflammation. Here, we report that PI is mediated by intrinsic apoptosis and exacerbated by autophagy. Conditional ablation of Bax and Bak activates the Akt-mTOR pathway and Bnip3-mediated mitophagy and preserves mitochondrial contents in compressed muscle. Moreover, we find that the presence/absence of Bax and Bak alters the roles and functions of autophagy in PI. Our results suggest that manipulating apoptosis and autophagy are potential therapeutic targets for treatment and prevention of PI.

Central obesity and hypertension are common risk factors for the metabolic syndrome, cardiovascular and renal diseases. Studies have shown that it is more difficult to control blood pressure and prevent end-organ damage in obese individuals with hypertension compared to their non-obese counterparts, especially among women. Obese females have a 6 times higher risk of developing hypertension than non-obese females while obese males are at a 1.5 times higher risk of developing hypertension, compared to their non-obese counterparts. Indeed, the inter-relationship between obesity and hypertension is unclear. Adipokines have been proposed to play a mediating role in the relationship between obesity and hypertension and are involved in the pathogenesis of metabolic diseases. Therefore, this study sought to determine the role of adipokines (adiponectin, plasminogen activator inhibitor-1, leptin, and tumor necrosis factor-α) in hypertensive Hong Kong Chinese women with central obesity. A total of 387 women aged 58 ± 11 years who were examined with a 2 × 2 factorial design for central obesity (waist circumference ≥ 80 cm) and hypertension (blood pressure ≥ 140/90 mmHg), were recruited from a pool of 1,492 Hong Kong Chinese adults who were previously screened for metabolic syndrome. Subjects with hyperglycemia, hypertriglyceridemia, and dyslipidemia were excluded to eliminate confounding effects. Our findings revealed that hypertensive women with central obesity had a lower anti-inflammatory status (adiponectin) and a higher pro-inflammatory status (TNF-α) than obese alone or hypertensive alone women. Also, women with central obesity had higher circulatory PAI-1 and leptin concentrations than their non-obese counterparts. We conclude that obesity may shift toward a more pro-inflammatory state and may become more severe in the presence of hypertension or vice versa.

Objective Metabolic syndrome (MetS) or prediabetes is a complex disorder that is defined by a clustering of cardiometabolic risk factors, including obesity, hypertriglyceridemia, reduced high-density lipoprotein (HDL) cholesterol, hypertension, and insulin resistance. Among cardiometabolic risk factors, central obesity plays a key role in the development of MetS through alterations in the secretion of adipokines and interacts with other MetS risk factors to unfavorably influence overall cardiometabolic risk. Obesity has grasped epidemic proportions in Asia, which has the highest number of people with diabetes in the world. But, the importance of central obesity in the clustering of all four MetS risk factors or vice versa in predicting severity of MetS has not yet been investigated in Asian population. Therefore, the present study examined the influence of central obesity on circulating levels of adipokines through its interaction with the clustering of cardiometabolic risk factors of MetS including hyperglycemia, hypertriglyceridemia, dyslipidemia and hypertension in Hong Kong Chinese adults. Subjects Blood samples from 83 Hong Kong Chinese adults, who were previously screened for MetS according to the guideline of the United States National Cholesterol Education Program Expert Panel Adult Treatment Panel III criteria were selected. Insulin and adipokines, including visfatin, chemerin, plasminogen activator inhibitor-1 (PAI-1), resistin, C-C motif chemokine ligand 2 (CCL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumour necrosis factor-α (TNF-α), leptin and adiponectin were assessed. Results The interacting effect of central obesity with all of the other four MetS risk factors increased the proinflammatory status of adipokines (TNF-α, leptin) and decreased the anti-inflammatory status of adipokine (adiponectin). Conclusion Our results indicate that the inflammatory status of MetS may be more severe in the presence of central obesity. Adipokines, as biomarkers for pathophysiological changes, may help to improve early patient identification and to predict MetS-associated morbidity and mortality.

Study of the exacerbating effects of chemotherapeutics, such as doxorubicin, on the impairment of insulin metabolic signaling in aged skeletal muscle is very limited. Here, we tested the hypothesis that activation of sirtuin 1 deacetylase activity by resveratrol would prevent the disruption of insulin signaling and augmentation of catabolic markers induced by doxorubicin in aged skeletal muscle. Two- and 10-month-old senescence-accelerated mice (prone 8) were randomized to receive saline, doxorubicin, doxorubicin and resveratrol, or a combination of doxorubicin, resveratrol, and sirtinol or EX527. Doxorubicin reduced the sirtuin 1 activity without affecting the phosphorylation levels of IRS1(Ser307), mTOR(Ser2481), Akt(Thr308/Ser473), membranous glucose transporter 4, protein abundance of PDK4, and enzymatic activity of pyruvate dehydrogenase in aged muscles. Intriguingly, resveratrol attenuated the doxorubicin-induced elevations of apoptotic and catabolic markers measured as Bax, caspase 3 activity, apoptotic DNA fragmentation, MuRF-1, ubiquitinated proteins, and proteasomal activity in aged muscles, whereas these beneficial effects were abolished on inhibition of sirtuin 1 by sirtinol or EX527. Markers of insulin signaling were not affected by doxorubicin or resveratrol in the senescent skeletal muscle. Nevertheless, the antiapoptotic and anticatabolic effects of resveratrol in aged skeletal muscle treated with doxorubicin were mediated in a sirtuin 1-dependent signaling manner.

Impairment of insulin signaling in skeletal muscle detrimentally affects insulin-stimulated disposal of glucose. Restoration of insulin signaling in skeletal muscle is important as muscle is one of the major sites for disposal of blood glucose. Recently, unacylated ghrelin (UnAG) has received attention in diabetic research due to its favorable actions on improving glucose tolerance, glycemic control, and insulin sensitivity. The investigation of UnAG has entered phase Ib clinical trial in type 2 diabetes and phase II clinical trial in hyperphagia in Prader-Willi syndrome. Nonetheless, the precise mechanisms responsible for the anti-diabetic actions of UnAG remain incompletely understood. In this study, we examined the effects of UnAG on restoring the impaired insulin signaling in skeletal muscle of db/db diabetic mice. Our results demonstrated that UnAG effectively restored the impaired insulin signaling in diabetic muscle. UnAG decreased insulin receptor substrate (IRS) phosphorylation, increased protein kinase B (Akt) phosphorylation, and, hence, suppressed mTOR signaling. Consequently, UnAG enhanced Glut4 localization and increased PDH activity in the diabetic skeletal muscle. Intriguingly, our data indicated that UnAG normalized the suppressed autophagic signaling in diabetic muscle. In conclusion, our findings illustrated that UnAG restored the impaired insulin and autophagic signaling in skeletal muscle of diabetic mice, which are valuable to understand the underlying mechanisms of the anti-diabetic action of UnAG at peripheral skeletal muscle level.

Activation of Foxo1 is known to promote apoptosis and disturbances to insulin signalling. However, their modulating roles in aged skeletal muscle are not clear. The present study tested the hypothesis that long-term (i.e. 8 month) resveratrol supplementation would improve physical traits including exercise capacity and basal voluntary activity of aged mice and modulate insulin/apoptotic signalling in aged skeletal muscle. This study also examined whether these resveratrol-associated alterations would involve orchestration of the SIRT1-Foxo1 signalling axis.Two-month-old SAMP8 mice were randomly assigned to young, aged and aged with resveratrol treatment (AR) groups. The AR mice were supplemented with 4.9 mg(-1) kg(-1) day(-1) resveratrol for 8 months. All animals were subject to endurance capacity test and voluntary motor behaviour assessment. The lateral gastrocnemius muscle tissues were harvested for further analyses.Long-term resveratrol treatment significantly alleviated the age-associated reductions in exercise capacity and voluntary motor behaviour. The protein content, but not the deacetylase activity of SIRT1 was increased with concomitant elevations of p300 acetylase and acetylation of Foxo1 in aged muscle. The aged muscle also manifested signs of impaired insulin signalling including attenuated phosphorylation of Akt, activity of pyruvate dehydrogenase and membrane trafficking of GLUT4 and elevated levels of phosphorylated IRS1 and iNOS and apoptotic activation measured as Bim, p53 and apoptotic DNA fragmentation. Intriguingly, all these age-related adverse changes were mitigated with the activation of SIRT1 deacetylase activity after long-term resveratrol treatment.These data suggest that modulation of the SIRT1-Foxo1 axis by long-term resveratrol treatment enhances physical traits and alleviates the unfavourable changes in insulin and apoptotic signalling in aged muscle.

Key points Doxorubicin induced functional deteriorations and elevations of USP7-related apoptotic/catabolic signalling in the senescent heart Resveratrol protects against doxorubicin-induced alterations through the restoration of SIRT1 deacetylase activity Abstract A compromised cardiac function is often seen in elderly cancer patients receiving doxorubicin therapy. The present study tested the hypothesis that acute intervention with resveratrol, a natural anti-oxidant found in grapes and red wine, reduces the cardiotoxicity of doxorubicin through restoration of sirtuin 1 (SIRT1) deacetylase activity, and attenuation of the catabolic/apoptotic pathways orchestrated by USP7, a p53 deubiquitinating protein, using young (aged 2 months) and old (aged 10 months) senescence-accelerated mice prone 8 (SAMP8). Animals were randomised to receive saline, doxorubicin, and doxorubicin in combination with resveratrol, in the presence or absence of SIRT1 inhibitors, sirtinol or EX527. Resveratrol alone, but not in combination with either of the SIRT1 inhibitors, suppressed the doxorubicin-induced impairment of cardiac systolic function in aged animals. Doxorubicin reduced SIRT1 deacetylase activity, and elevated proteasomal activity and USP7; it also increased the protein level of p300 and ubiquitinated proteins in hearts from aged SAMP8. These doxorubicin-induced alterations were prevented by resveratrol, whereas the protective action of resveratrol was antagonised by sirtinol and EX527. In young SAMP8 hearts, resveratrol attenuated the doxorubicin-induced increases in acetylation of Foxo1 and transactivation of MuRF-1, whereas these mitigations were not found after treatment with SIRT1 inhibitors. However, the protein contents of acetylated Foxo1 and MuRF-1 were not affected by any of the drugs studied in aged SAMP8 hearts. Resveratrol also ameliorated the augmentation of pro-apoptotic markers including p53, Bax, caspase 3 activity and apoptotic DNA fragmentation induced by doxorubicin in hearts from aged animals, whereas these reductions were diminished by combined treatment with SIRT1 inhibitors. These data demonstrate that resveratrol ameliorates doxorubicin-induced cardiotoxicity in aged hearts through the restoration of SIRT1 activity to attenuate USP7-related catabolic/pro-apoptotic signalling.

[D-Lys3]-GHRP-6 is regarded as a highly selective growth-hormone secretagogue receptor (GHSR) antagonist and has been widely used to investigate the dependency of GHSR-1a signalling mediated by acylated ghrelin. However, [D-Lys3]-GHRP-6 has been reported to influence other cellular processes which are unrelated to GHSR-1a. This study aimed to examine the effects of [D-Lys3]-GHRP-6 on autophagic and apoptotic cellular signalling in skeletal muscle. [D-Lys3]-GHRP-6 enhanced the autophagic signalling demonstrated by the increases in protein abundances of beclin-1 and LC3 II-to-LC3 1 ratio in both normal muscle and doxorubicin-injured muscle. [D-Lys3]-GHRP-6 reduced the activation of muscle apoptosis induced by doxorubicin. No histological abnormalities were observed in the [D-Lys3]-GHRP-6-treated muscle. Intriguingly, the doxorubicin-induced increase in centronucleated muscle fibres was not observed in muscle treated with [D-Lys3]-GHRP-6, suggesting the myoprotective effects of [D-Lys3]-GHRP-6 against doxorubicin injury. The [D-Lys3]-GHRP-6-induced activation of autophagy was found to be abolished by the co-treatment of CXCR4 antagonist, suggesting that the pro-autophagic effects of [D-Lys3]-GHRP-6 might be mediated through CXCR4. In conclusion, [D-Lys3]-GHRP-6 exhibits pro-autophagic effects on skeletal muscle under both normal and doxorubicin-injured conditions.

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.

Objectives Metabolic syndrome (MetS) is associated with diabetes mellitus and cardiovascular diseases. Our previous study indicated that people with MetS showed a decrease in waist circumference and a decreasing trend in blood pressure after 1 year of yoga. This study investigated the effect of yoga on MetS people with high-normal blood pressure by exploring modulations in pro-inflammatory adipokines (leptin, chemerin, visfatin and plasminogen activator inhibitor-1 or PAI-1) and an anti-inflammatory adipokine (adiponectin). Design & Methods A total of 97 Hong Kong Chinese individuals aged 57.6 ± 9.1 years with MetS and high-normal blood pressure were randomly assigned to control (n = 45) and yoga groups (n = 52). Participants in the control group were not given any intervention but were contacted monthly to monitor their health status. Participants in the yoga group underwent a yoga training programme with three 1-hour yoga sessions weekly for 1 year. The participants’ sera were harvested and assessed for adipokines. Generalized estimating equation (GEE) was used to examine the interaction effect between 1 year of time (pre vs. post) and intervention (control vs. yoga). Results GEE analyses revealed significant interaction effects between 1-year of time and yoga intervention for the decreases in leptin and chemerin and the increase in adiponectin concentration in the sera examined. Conclusion These results demonstrated that 1 year of yoga training decreased pro-inflammatory adipokines and increased anti-inflammatory adipokine in adults with MetS and high-normal blood pressure. These findings support the beneficial role of yoga in managing MetS by favourably modulating adipokines. This article is protected by copyright. All rights reserved.

Elevations of cardiomyocyte apoptosis and fibrotic deposition are major characteristics of the ageing heart. Resveratrol, a polyphenol in grapes and red wine, is known to improve insulin resistance and increase mitochondrial biogenesis through the SIRT1-PGC-1α signalling axis. Recent studies attempted to relate SIRT1 activation by resveratrol to the regulation of apoptosis in various disease models of cardiac muscle. In the present study, we tested the hypothesis that long-term (8-month) treatment of resveratrol would activate SIRT1 and improve the cardiac function of senescent mice through suppression of Foxo1-associated pro-apoptotic signalling. Our echocardiographic measurements indicated that the cardiac systolic function measured as fractional shortening and ejection fraction was significantly reduced in aged mice when compared with the young mice. These reductions, however, were not observed in resveratrol-treated hearts. Ageing significantly reduced the deacetylase activity, but not the protein abundance of SIRT1 in the heart. This reduction was accompanied by increased acetylation of the Foxo1 transcription factor and transactivation of its target, pro-apoptotic Bim. Subsequent analyses indicated that pro-apoptotic signalling measured as p53, Bax and apoptotic DNA fragmentation was up-regulated in the heart of aged mice. In contrast, resveratrol restored SIRT1 activity and suppressed elevations of Foxo1 acetylation, Bim and pro-apoptotic signalling in the aged heart. In parallel, resveratrol also attenuated the ageing-induced elevations of fibrotic collagen deposition and markers of oxidative damage including 4HNE and nitrotyrosine. In conclusion, these novel data demonstrate that resveratrol mitigates pro-apoptotic signalling in senescent heart through a deacetylation mechanism of SIRT1 that represses the Foxo1-Bim-associated pro-apoptotic signalling axis.

Anti-cancer agent doxorubicin (DOX) has been demonstrated to worsen insulin signaling, engender muscle atrophy, trigger pro-inflammation, and induce a shift to anaerobic glycolytic metabolism in skeletal muscle. The myotoxicity of DOX in diabetic skeletal muscle remains largely unclear. This study examined the effects of DOX on insulin signaling, muscle atrophy, pro-/anti-inflammatory microenvironment, and glycolysis metabolic regulation in skeletal muscle of db/db diabetic and db/+ non-diabetic mice. Non-diabetic db/+ mice and diabetic db/db mice were randomly assigned to the following groups: db/+CON, db/+DOX, db/dbCON, and db/dbDOX. Mice in db/+DOX and db/dbDOX groups were intraperitoneally injected with DOX at a dose of 15 mg per kg body weight whereas mice in db/+CON and db/dbCON groups were injected with the same volume of saline instead of DOX. Gastrocnemius was immediately harvested, weighed, washed with cold phosphate buffered saline, frozen in liquid nitrogen, and stored at -80°C for later analysis. The effects of DOX on diabetic muscle were neither seen in insulin signaling markers (Glut4, pIRS1Ser(636∕639), and pAktSer(473)) nor muscle atrophy markers (muscle mass, MuRF1 and MAFbx). However, DOX exposure resulted in enhancement of pro-inflammatory favoring microenvironment (as indicated by TNF-α, HIFα and pNFκBp65) accompanied by diminution of anti-inflammatory favoring microenvironment (as indicated by IL15, PGC1α and pAMPKβ1Ser108). Metabolism of diabetic muscle was shifted to anaerobic glycolysis after DOX exposure as demonstrated by our analyses of PDK4, LDH and pACCSer(79). Our results demonstrated that there might be a link between inflammatory modulation and the dysregulation of aerobic glycolytic metabolism in DOX-injured diabetic skeletal muscle. These findings help to understand the pathogenesis of DOX-induced myotoxicity in diabetic muscle.

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 signalling in skeletal muscle exposed to moderate compression. Two cycles of 6-hour 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 favourable 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.

Doxorubicin induced functional deteriorations and elevations of USP7-related apoptotic/catabolic signalling in the senescent heart Resveratrol protects against doxorubicin-induced alterations through the restoration of SIRT1 deacetylase activityA compromised cardiac function is often seen in elderly cancer patients receiving doxorubicin therapy. The present study tested the hypothesis that acute intervention with resveratrol, a natural anti-oxidant found in grapes and red wine, reduces the cardiotoxicity of doxorubicin through restoration of sirtuin 1 (SIRT1) deacetylase activity, and attenuation of the catabolic/apoptotic pathways orchestrated by USP7, a p53 deubiquitinating protein, using young (aged 2 months) and old (aged 10 months) senescence-accelerated mice prone 8 (SAMP8). Animals were randomised to receive saline, doxorubicin, and doxorubicin in combination with resveratrol, in the presence or absence of SIRT1 inhibitors, sirtinol or EX527. Resveratrol alone, but not in combination with either of the SIRT1 inhibitors, suppressed the doxorubicin-induced impairment of cardiac systolic function in aged animals. Doxorubicin reduced SIRT1 deacetylase activity, and elevated proteasomal activity and USP7; it also increased the protein level of p300 and ubiquitinated proteins in hearts from aged SAMP8. These doxorubicin-induced alterations were prevented by resveratrol, whereas the protective action of resveratrol was antagonised by sirtinol and EX527. In young SAMP8 hearts, resveratrol attenuated the doxorubicin-induced increases in acetylation of Foxo1 and transactivation of MuRF-1, whereas these mitigations were not found after treatment with SIRT1 inhibitors. However, the protein contents of acetylated Foxo1 and MuRF-1 were not affected by any of the drugs studied in aged SAMP8 hearts. Resveratrol also ameliorated the augmentation of pro-apoptotic markers including p53, Bax, caspase 3 activity and apoptotic DNA fragmentation induced by doxorubicin in hearts from aged animals, whereas these reductions were diminished by combined treatment with SIRT1 inhibitors. These data demonstrate that resveratrol ameliorates doxorubicin-induced cardiotoxicity in aged hearts through the restoration of SIRT1 activity to attenuate USP7-related catabolic/pro-apoptotic signalling.

Diabetic cardiomyopathy is a specific complication of type 2 diabetes mellitus, which causes progressive cardiac dysfunction. Desacyl ghrelin has been preliminarily demonstrated to have beneficial effects on cardiovascular system and glucose metabolism, which are both related to diabetic cardiomyopathy. The aim of this study was to investigate the protective effects of desacyl ghrelin on cardiac dysfunction, cardiac fibrosis, and cellular autophagy in a type 2 diabetic mouse model. Fourteen- to eighteen-week-old db/db diabetic and db/+ non-diabetic mice were intraperitoneally treated with desacyl ghrelin at a dosage of 100 μg/kg for ten consecutive days. Ventricular fractional shortening was examined as an indicator of cardiac function by transthoracic echocardiography. The presence of diabetic cardiomyopathy was evident by the reduction in fractional shortening shown in our examined db/db mice. Intriguingly, this reduction in fractional shortening was not observed in the hearts of db/db mice treated with desacyl ghrelin. Cardiac fibrosis (indicated by excessive collagen deposition, decreased by Adiponectin and Mmp13 expression, and up-regulated by Mmp8 expression) and impairment of autophagic signalling (indicated by decreases in Foxo3 and LC3 II-to-LC3 I ratio) were shown in the hearts of diabetic mice. All these cellular and molecular alterations were alleviated by desacyl ghrelin treatment. The key cardiac pro-survival cellular signals including AMPK, Akt, ERK1/2, and GSK3α/β were impaired in the diabetic hearts, but the administration of desacyl ghrelin attenuated these signalling impairments. These results collectively demonstrate that desacyl ghrelin protects the heart against cardiac dysfunction in type 2 diabetic mice by inhibiting excessive collagen deposition and enhancing cardiac autophagic signalling via the pro-survival cellular AMPK/ERK1/2 signalling pathways.

Elevations of cardiomyocyte apoptosis and fibrotic deposition are major characteristics of the ageing heart. Resveratrol, a polyphenol in grapes and red wine, is known to improve insulin resistance and increase mitochondrial biogenesis through the SIRT1–PGC-1α signalling axis. Recent studies attempted to relate SIRT1 activation by resveratrol to the regulation of apoptosis in various disease models of cardiac muscle. In the present study, we tested the hypothesis that long-term (8-month) treatment of resveratrol would activate SIRT1 and improve the cardiac function of senescent mice through suppression of Foxo1-associated pro-apoptotic signalling. Our echocardiographic measurements indicated that the cardiac systolic function measured as fractional shortening and ejection fraction was significantly reduced in aged mice when compared with the young mice. These reductions, however, were not observed in resveratrol-treated hearts. Ageing significantly reduced the deacetylase activity, but not the protein abundance of SIRT1 in the heart. This reduction was accompanied by increased acetylation of the Foxo1 transcription factor and transactivation of its target, pro-apoptotic Bim. Subsequent analyses indicated that pro-apoptotic signalling measured as p53, Bax and apoptotic DNA fragmentation was up-regulated in the heart of aged mice. In contrast, resveratrol restored SIRT1 activity and suppressed elevations of Foxo1 acetylation, Bim and pro-apoptotic signalling in the aged heart. In parallel, resveratrol also attenuated the ageing-induced elevations of fibrotic collagen deposition and markers of oxidative damage including 4HNE and nitrotyrosine. In conclusion, these novel data demonstrate that resveratrol mitigates pro-apoptotic signalling in senescent heart through a deacetylation mechanism of SIRT1 that represses the Foxo1–Bim-associated pro-apoptotic signalling axis.

Doxorubicin is an effective chemotherapeutic agent used to treat malignancies, but it causes cardiomyopathy. Preliminary evidence suggests that desacyl ghrelin might have protective effects on doxorubicin cardiotoxicity. This study examined the cellular effects of desacyl ghrelin on myocardial fibrosis and apoptosis in a doxorubicin cardiomyopathy experimental model. Adult C57BL/6 mice received an intraperitoneal injection of doxorubicin to induce cardiomyopathy, followed by 4-day treatment of saline (control) or desacyl ghrelin with or without [d-Lys3]-GHRP-6 (a growth hormone secretagogue receptor or GHSR1a antagonist). Ventricular structural and functional parameters were evaluated by transthoracic echocardiography. Molecular and cellular measurements were performed in ventricular muscle to examine myocardial fibrosis and apoptosis. Cardiac dysfunction was induced by doxorubicin, as indicated by significant decreases in ventricular fractional shortening and ejection fraction. This doxorubicin-induced cardiac dysfunction was prevented by the treatment of desacyl ghrelin no matter with or without the presence of [d-Lys3]-GHRP-6. Doxorubicin induced fibrosis (accumulated collagen deposition and increased CTGF), activated apoptosis (increased TUNEL index, apoptotic DNA fragmentation, and caspase-3 activity and decreased Bcl-2/Bax ratio), and suppressed phosphorylation status of prosurvival signals (ERK1/2 and Akt) in ventricular muscles. All these molecular and cellular alterations induced by doxorubicin were not found in the animals treated with desacyl ghrelin. Notably, the changes in the major markers of apoptosis, fibrosis, and Akt phosphorylation were found to be similar in the animals following the treatment of desacyl ghrelin with and without GHSR antagonist [d-Lys3]-GHRP-6. These findings demonstrate clearly that desacyl ghrelin protects the cardiomyocytes against the doxorubicin-induced cardiomyopathy by preventing the activation of cardiac fibrosis and apoptosis, and the effects are probably mediated through GHSR-independent mechanism.

The molecular mechanisms that contribute to the pathogenesis of pressure-induced deep tissue injury are largely unknown. This study tested the hypothesis that oxidative stress and DNA damage signalling mechanism in skeletal muscle are involved in deep tissue injury. Adult Sprague Dawley rats were subject to an experimental protocol to induce deep tissue injury. Two compression cycles with a static pressure of 100 mmHg was applied to an area of 1.5 cm(2) over the mid-tibialis region of right limb of the rats. The left uncompressed limb served as intra-animal control. Muscle tissues underneath compression region were collected for examination. Our analyses indicated that pathohistological characteristics including rounding contour of myofibres and extensive nuclei accumulation were apparently shown in compressed muscles. The elevation of 8OHdG immunopositively stained nuclei indicated the presence of oxidative DNA damage. Increase in oxidative stress was revealed by showing significant elevation of 4HNE and decreases in mRNA abundance of SOD1, catalase and GPx, and protein content of SOD2 in compressed muscles relative to control muscles. Increase in nitrosative stress was demonstrated by significant elevation of nitrotyrosine and NOS2 mRNA content. The activation of tumor suppressor p53 signalling was indicated by the remarkable increases in protein contents of total p53 and serine-15 phosphorylated p53. The transcript expression of the DNA-repairing enzyme, Rad23A, was significantly suppressed in compressed muscles. Our time-course study indicated that increased oxidative/nitrosative stress and proapoptotic signalling were maintained in muscles receiving increasing amount of compression cycles and post-compression time. Furthermore, resveratrol was found to attenuate the histological damage, oxidative/nitrosative stress and proapoptotic signalling in response to prolonged moderate compression. In conclusion, our findings are consistent with the hypothesis that oxidative stress and DNA damage signalling in skeletal muscle are involved in the underlying mechanisms responsible for the pathogenesis of pressure-induced deep tissue injury.