Microglia Sirt6 modulates the transcriptional activity of NRF2 to ameliorate high-fat diet-induced obesity.

BACKGROUND: Microglia play a pivotal role in neuroinflammation, while obesity triggers hypothalamic microglia activation and inflammation. Sirt6 is an important regulator of energy metabolism in many peripheral tissues and hypothalamic anorexic neurons. However, the exact mechanism for microglia Sirt6 in controlling high-fat diet-induced obesity remain unknown. METHODS: Microglia Sirt6 expression levels under various nutritional conditions were measured in the hypothalamus of mice. Also, microglia Sirt6-deficient mice were provided various diets to monitor metabolic changes and hypothalamic inflammatory response. Besides, RNA-seq and Co-IP of microglia with Sirt6 alterations were conducted to further investigate the detailed mechanism by which Sirt6 modulated microglia activity. RESULTS: We found that Sirt6 was downregulated in hypothalamic microglia in mice given a high-fat diet (HFD). Additionally, knockout of microglia Sirt6 exacerbated high-fat diet-induced hypothalamic microglial activation and inflammation. As a result, mice were more prone to obesity, exhibiting a decrease in energy expenditure, impaired glucose tolerance, insulin and leptin resistance, and increased food intake. In vitro, Sirt6 overexpression in BV2 cells displayed protective effects against oleic acid and palmitic acid treatment-derived inflammatory response. Mechanically, Sirt6 deacetylated and stabilised NRF2 to increase the expression of anti-oxidative genes and defend against reactive oxygen species overload. Pharmacological inhibition of NRF2 eliminated the beneficial modulating effects of Sirt6 on microglial activity. CONCLUSION: Collectively, our results revealed that microglial Sirt6 was a primary contributor of microglial activation in the central regulation of obesity. Thus, microglial Sirt6 may be an important therapeutic target for obesity.

Sodium butyrate activates HMGCS2 to promote ketone body production through SIRT5-mediated desuccinylation.

Ketone bodies have beneficial metabolic activities, and the induction of plasma ketone bodies is a health promotion strategy. Dietary supplementation of sodium butyrate (SB) is an effective approach in the induction of plasma ketone bodies. However, the cellular and molecular mechanisms are unknown. In this study, SB was found to enhance the catalytic activity of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), a rate-limiting enzyme in ketogenesis, to promote ketone body production in hepatocytes. SB administrated by gavage or intraperitoneal injection significantly induced blood ß-hydroxybutyrate (BHB) in mice. BHB production was induced in the primary hepatocytes by SB. Protein succinylation was altered by SB in the liver tissues with down-regulation in 58 proteins and up-regulation in 26 proteins in the proteomics analysis. However, the alteration was mostly observed in mitochondrial proteins with 41% down- and 65% up-regulation, respectively. Succinylation status of HMGCS2 protein was altered by a reduction at two sites (K221 and K358) without a change in the protein level. The SB effect was significantly reduced by a SIRT5 inhibitor and in Sirt5-KO mice. The data suggests that SB activated HMGCS2 through SIRT5-mediated desuccinylation for ketone body production by the liver. The effect was not associated with an elevation in NAD+/NADH ratio according to our metabolomics analysis. The data provide a novel molecular mechanism for SB activity in the induction of ketone body production.

Association of sirtuins (SIRT1-7) with lung and intestinal diseases.

"Exterior-interior correlation between the lung and large intestine" is one of the important contents of traditional Chinese medicine. This theory describes the role of the lung and the intestine in association with disease treatment. The "lung-gut" axis is a modern extension of the "exterior-interior correlation between lung and large intestine" theory in TCM. Sirtuin (SIRT) is a nicotinamide adenine dinucleotide (NAD+)-dependent enzyme family with deacetylase properties, which is highly conserved from bacteria to humans. The sirtuin defines seven silencing regulatory proteins (SIRT1-7) in human cells. It can regulate aging, metabolism, and certain diseases. Current studies have shown that sirtuins have dual characteristics, acting as both tumor promoters and tumor inhibitors in cancers. This paper provides a comparative summary of the roles of SIRT1-7 in the intestine and lung (both inflammatory diseases and tumors), and the promoter/suppressor effects of targeting SIRT family microRNAs and modulators of inflammation or tumors. Sirtuins have great potential as drug targets for the treatment of intestinal and respiratory diseases. Meanwhile, it may provide new ideas of future drug target research.

Nutraceutical and Dietary Strategies for Up-Regulating Macroautophagy.

Macroautophagy is a "cell cleansing" process that rids cells of protein aggregates and damaged organelles that may contribute to disease pathogenesis and the dysfunctions associated with aging. Measures which boost longevity and health span in rodents typically up-regulate macroautophagy, and it has often been suggested that safe strategies which can promote this process in humans may contribute to healthful aging. The kinase ULK1 serves as a trigger for autophagy initiation, and the transcription factors TFEB, FOXO1, ATF4 and CHOP promote expression of a number of proteins which mediate macroautophagy. Nutraceutical or dietary measures which stimulate AMPK, SIRT1, eIF5A, and that diminish the activities of AKT and mTORC1, can be expected to boost the activities of these pro-autophagic factors. The activity of AMPK can be stimulated with the phytochemical berberine. SIRT1 activation may be achieved with a range of agents, including ferulic acid, melatonin, urolithin A, N1-methylnicotinamide, nicotinamide riboside, and glucosamine; correction of ubiquinone deficiency may also be useful in this regard, as may dietary strategies such as time-restricted feeding or intermittent fasting. In the context of an age-related decrease in cellular polyamine levels, provision of exogenous spermidine can boost the hypusination reaction required for the appropriate post-translational modification of eIF5A. Low-protein plant-based diets could be expected to increase ATF4 and CHOP expression, while diminishing IGF-I-mediated activation of AKT and mTORC1. Hence, practical strategies for protecting health by up-regulating macroautophagy may be feasible.

BaZiBuShen alleviates cognitive deficits and regulates Sirt6/NRF2/HO-1 and Sirt6/P53-PGC-1α-TERT signaling pathways in aging mice.

ETHNOPHARMACOLOGICAL RELEVANCE: BaZiBuShen formula (BZBS) is clinically used to counteract mental fatigue and to retard the aging process. Brain aging echoes in major risks of human sufferings and has become one of the main challenges to our societies and the health-care systems. AIM OF THE STUDY: To investigate the effect and mode of action of BZBS on aging-associated cognitive impairments. MATERIALS AND METHODS: BZBS was orally administered to D-galactose and NaNO2-induced aging mice. Premature senescence was assessed using the Morris water maze, step-down type passive avoidance, and pole-climbing tests. Telomere length was examined by qPCR analysis. Telomerase activity was assessed using PCR ELISA assay. Mitochondrial complex IV activity was examined by biochemical test. The levels of redox and immune status were determined by ELISA or biochemical assay. The expressions of sirtuin 6 (Sirt6), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), P53, telomerase reverse transcriptase (TERT), heme oxygenase-1 (HO-1), phospho(p)-nuclear factor erythroid-2 related factor 2 (NRF2), caspase-3, Bcl-2 associated x (Bax), and B-cell lymphoma-2 (Bcl-2) in the cerebral cortex were examined by Western blot and/or immunohistochemical staining. RESULTS: BZBS intervention ameliorated reduced brain performances in aging mice, including memory, cognitive, and motor functions. In addition, BZBS administration to aging mice preserved redox homeostasis, attenuated immunosenescence, and maintained telomerase activity and telomere length. Moreover, BZBS treatment were associated with a declines in P53, caspase-3, Bax expressions and an increase in Sirt6, p-HO-1, p-NRF2, PGC-1α, and Bcl-2 expressions in the brains of this rapid aging mouse. CONCLUSIONS: BZBS attenuates premature senescence possibly via the preservation of redox homeostasis and telomere integrity, and inhibition of apoptosis in rapid aging mouse. The mechanism governing the alterations may be associated with through the activation of Sirt6/NRF2/HO-1 and Sirt6/P53-PGC-1α-TERT signaling pathways. The results suggest that BZBS may provide a novel strategy for confronting aging and age-associated diseases.

Total Sesquiterpene Glycosides from Loquat Leaves Ameliorate HFD-Induced Insulin Resistance by Modulating IRS-1/GLUT4, TRPV1, and SIRT6/Nrf2 Signaling Pathways.

Loquat (Eriobotrya japonica Lindl.), a subtropical fruit tree native to Asia, is not only known to be nutritive but also beneficial for the treatment of diabetes in the south of China. To expand its development, this study was undertaken concerning the potential therapeutic role of total sesquiterpene glycosides (TSGs) from loquat leaves in insulin resistance (IR), the major causative factor of type 2 diabetes mellitus (T2DM). Male C57BL/6 mice were fed on high-fat diet (HFD) to induce IR and then were given TSG by oral administration at 25 and 100 mg/kg/day, respectively. TSG notably improved metabolic parameters including body weight, serum glucose, and insulin levels and prevented hepatic injury. Moreover, inflammatory response and oxidative stress were found to be remarkably alleviated in IR mice with TSG supplement. Further research in liver of IR mice demonstrated that TSG repaired the signalings of insulin receptor substrate-1 (IRS-1)/glucose transporter member 4 (GLUT4) and AMP-activated protein kinase (AMPK), which improved glucose and lipid metabolism and prevented lipid accumulation in liver. It was also observed that TSG suppressed the expression of transient receptor potential vanilloid 1 (TRPV1), whereas the signaling pathway of sirtuin-6 (SIRT6)/nuclear factor erythroid 2-related factor 2 (Nrf2) was significantly promoted. Based on the results, the current study demonstrated that TSG from loquat leaves potentially ameliorated IR in vivo by enhancing IRS-1/GLUT4 signaling and AMPK activation and modulating TRPV1 and SIRT6/Nrf2 signaling pathways.

SIRT 3 was involved in Lycium barbarum seed oil protection testis from oxidative stress: in vitro and in vivo analyses.

CONTEXT: Lycium barbarum L. (Solanaceae) seed oil (LBSO) exerts LBSO exerts protective effects in the testis in vivo and in vitro via upregulating SIRT3. OBJECTIVE: This study evaluates the effects and mechanism of LBSO in the d-galactose (d-gal)-induced ageing testis. MATERIALS AND METHODS: Male Sprague Dawley (SD) rats (n = 30, 8-week-old) were randomly divided into three groups: LBSO group (n = 10) where rats received subcutaneous injection of d-gal at 125 mg/kg/day for 8 weeks and intragastric administration of LBSO at 1000 mg/kg/day for 4 weeks, ageing model group (n = 10) received 8-week-sunbcutaneous injection of d-gal, and control group (n = 10) with same administration of normal saline. Lentivirus had established TM4 cells with SIRT3 overexpression or silencing before LBSO intervened in vitro. RESULTS: Treatment with LBSO, the levels of INHB and testosterone both increased, compared to ageing model. In vitro, we found the ED50 of LBSO was 86.72 ± 1.49 and when the concentration of LBSO at 100 µg/mL to intervene TM4 cells, the number of cells increased from 8120 ± 676.2 to 15251 ± 1119, and the expression of SIRT3, HO-1, and SOD upregulated. However, HO-1 and SOD were dysregulated by silencing SIRT3. On the other hand, the expression of AMPK and PGC-1α upregulated as an effect of SIRT3 overexpression by lentivirus, meanwhile the same increasing trend of that being found in cells treated with LBSO, compared to control group. DISCUSSION AND CONCLUSIONS: LBSO alleviated oxidative stress in d-gal-induced sub-acutely ageing testis and TM4 cells by suppressing the oxidative stress to mitochondria via SIRT3/AMPK/PGC-1α.

HSF-1 and SIR-2.1 linked insulin-like signaling is involved in goji berry (Lycium spp.) extracts promoting lifespan extension of Caenorhabditis elegans.

The anti-cancer, vision-improving, and reproduction-enhancing effects of goji berry have been generally recognized, but its role in anti-aging is rarely studied in depth. Therefore, two widely-circulated goji berries, Lycium ruthenicum Murr. (LRM) and Lycium Barbarum. L (LB), were selected to explore their effects on extending lifespan and enhancing defense against extrinsic stress and to uncover the mechanism of action through genetic study. The results showed that supplementation with high-dose LRM (10 mg mL-1) and LB (100 mg mL-1) extracts significantly extended the lifespan of Caenorhabditis elegans (C. elegans) by 25.19% and 51.38%, respectively, accompanied by the improved stress tolerance of C. elegans to paraquat-induced oxidation, UV-B irradiation and heat shock. Furthermore, LRM and LB extracts remarkably enhanced the activities of antioxidant enzymes including SOD and CAT in C. elegans, while notably decreased the lipofuscin level. Further genetic research demonstrated that the expression levels of key genes daf-16, sod-2, sod-3, sir-2.1 and hsp-16.2 in C. elegans were up-regulated by the intervention with LRM and LB, while that of the age-1 level was down-regulated. Moreover, the daf-16 (mu86) I, sir-2.1 (ok434) IV and hsf-1 (sy441) I mutants reversed the longevity effect brought about by LRM or LB, which confirmed that these genes were required in goji berry-mediated lifespan extension. Therefore, we conclude that HSF-1 and SIR-2.1 act collaboratively with the insulin/IGF signaling pathway (IIS) in a daf-16-independent mode. The present study indicated goji berry as a potential functional food to alleviate the symptoms of aging.

Aging and pathological aging signatures of the brain: through the focusing lens of SIRT6.

Brain-specific SIRT6-KO mice present increased DNA damage, learning impairments, and neurodegenerative phenotypes, placing SIRT6 as a key protein in preventing neurodegeneration. In the aging brain, SIRT6 levels/activity decline, which is accentuated in Alzheimer's patients. To understand SIRT6 roles in transcript pattern changes, we analyzed transcriptomes of young WT, old WT and young SIRT6-KO mice brains, and found changes in gene expression related to healthy and pathological aging. In addition, we traced these differences in human and mouse samples of Alzheimer's and Parkinson's diseases, healthy aging and calorie restriction (CR). Our results define four gene expression categories that change with age in a pathological or non-pathological manner, which are either reversed or not by CR. We found that each of these gene expression categories is associated with specific transcription factors, thus serving as potential candidates for their category-specific regulation. One of these candidates is YY1, which we found to act together with SIRT6 regulating specific processes. We thus argue that SIRT6 has a pivotal role in preventing age-related transcriptional changes in brains. Therefore, reduced SIRT6 activity may drive pathological age-related gene expression signatures in the brain.

BaZiBuShen alleviates altered testicular morphology and spermatogenesis and modulates Sirt6/P53 and Sirt6/NF-κB pathways in aging mice induced by D-galactose and NaNO2.

ETHNOPHARMACOLOGICAL RELEVANCE: Sperm infertility and testicular atrophy are symptoms associated with aging. BaZiBuShen formula (BZBS), a patented Chinese herbal prescription composed of Semen Cuscutae, Fructus Lycii, Epimedii Folium, Fructus Schisandrae Sphenantherae, Fructus Cnidii, Fructus Rosae Laevigatae, Semen Allii Tuberosi., Radix Morindae Officinalis, Herba Cistanches, Fructus Rubi, Radix Rehmanniae Recens, Radix Cyathulae, Radix Ginseng, Cervi Cornu Pantotrichum, Hippocampus, and Fuctus Toosendan, has been used as a kidney-tonifying and anti-aging drug as well as for the treatment of impotence and male infertility in traditional Chinese medicine. AIM OF THE STUDY: We aimed at investigating whether BZBS preserves sperm and testes morphology in aging mice, and to explore the underlying mechanisms. MATERIALS AND METHODS: BZBS was orally administered to aging mice induced by D-galactose (D-gal) and NaNO2 for 65 days. Sperm quality and testes pathophysiological alterations were examined by a Semen Analysis System, hematoxylin-eosin staining, transmission electron microscopy, and mitochondrial complex IV activity. In addition, serum levels of total antioxidant capacity (TAC), malondialdehyde (MDA), 8-hydroxy-desoxyguanosine (8-OH-dG), reduced glutathione (GSH), oxidized glutathione disulfide (GSSG), testosterone (T), follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and tumor necrosis factor-α (TNF-α) were determined by ELISA. The expressions of P450 aromatase (CYP19), sirtuin 6 (Sirt6), P53, inducible nitric oxide synthase (iNOS), nuclear factor-kappa B (NF-κB)-p65, and phospho-NF-κB-p65 (NF-κB-pp65) in the testes were examined by western blot and/or immunohistochemical staining. RESULTS: Sustained exposure to D-gal/NaNO2 caused a deterioration of sperm quality and testes morphology in this rapid aging mouse model. BZBS treatment curtailed these alterations. These beneficial effects were associated with increased serum levels of TAC, GSH/GSSG, T, E2, and FSH, and decreased levels of MDA, TNF-α, and 8-OH-dG. BZBS treatment also downregulated the expressions of P53, iNOS, and NF-κB-pp65, as well as upregulated the expressions of Sirt6 and CYP19 in aging testes. CONCLUSIONS: BZBS preserves testicular morphology and spermatogenesis possibly via inhibition of oxidative stress and the modulation of the Sirt6/P53 and Sirt6/NF-κB signaling pathways. The results shed light on the beneficial effect of BZBS on sperm quality and fertility in aging males.

Aconitine attenuates mitochondrial dysfunction of cardiomyocytes via promoting deacetylation of cyclophilin-D mediated by sirtuin-3.

ETHNOPHARMACOLOGICAL RELEVANCE: Aconite is a processed product of seminal root of perennial herbaceous plant Aconitum Carmichaclii Debx. of Ranunculaceae. It has the effects of warming and tonifying heart yang and restoring yang to save from collapse. Aconitine is the main effective constituent of aconite and used to prevent and treat heart disease. However, how aconitine exerts myocardial protection is still poorly understood. AIM OF THE STUDY: The present study aimed to investigate the effects of aconitine on mitochondrial dysfunction and explore its mechanism of action. MATERIALS AND METHODS: The model of myocardial injury was induced by Angiotensin II (Ang II) (1 × 10-6 mol L-1), and H9c2 cells were incubated with different concentrations of aconitine. The effect of aconitine on mitochondrial was determined by flow cytometry, transmission electron microscopy, luciferase, Seahorse technique and Western blot. The effects of aconitine on sirtuin-3 (Sirt3) activity and Cyclophilin D (CypD) acetylation were detected by immunofluorescence, RT-PCR and co-immunoprecipitation. RESULTS: We demonstrate that aconitine alleviates the energy metabolic dysfunction of H9c2 cells by activating Sirt3 to deacetylate CypD and inhibiting mitochondrial permeability transition pore (mPTP) opening. In cardiomyocytes, aconitine significantly reduced mitochondrial fragmentation, inhibited acetylation of CypD, suppressed the mPTP opening, mitigated mitochondrial OXPHOS disorders, and improved the synthesis ability of ATP. In contrast, Sirt3 deficiency abolished the effects of aconitine on mPTP and OXPHOS, indicating that aconitine improves mitochondrial function by activating Sirt3. CONCLUSIONS: These results showed that aconitine attenuated the energy metabolism disorder by promoting Sirt3 expression and reducing CypD-mediated mPTP excess openness, rescuing mitochondrial function. Improve mitochondrial function may be a therapeutic approach for treating heart disease, which will generate fresh insight into the cardioprotective of aconitine.

Impaired mitochondrial medium-chain fatty acid oxidation drives periportal macrovesicular steatosis in sirtuin-5 knockout mice.

Medium-chain triglycerides (MCT), containing C8-C12 fatty acids, are used to treat several pediatric disorders and are widely consumed as a nutritional supplement. Here, we investigated the role of the sirtuin deacylase Sirt5 in MCT metabolism by feeding Sirt5 knockout mice (Sirt5KO) high-fat diets containing either C8/C10 fatty acids or coconut oil, which is rich in C12, for five weeks. Coconut oil, but not C8/C10 feeding, induced periportal macrovesicular steatosis in Sirt5KO mice. 14C-C12 degradation was significantly reduced in Sirt5KO liver. This decrease was localized to the mitochondrial ß-oxidation pathway, as Sirt5KO mice exhibited no change in peroxisomal C12 ß-oxidation. Endoplasmic reticulum ω-oxidation, a minor fatty acid degradation pathway known to be stimulated by C12 accumulation, was increased in Sirt5KO liver. Mice lacking another mitochondrial C12 oxidation enzyme, long-chain acyl-CoA dehydrogenase (LCAD), also developed periportal macrovesicular steatosis when fed coconut oil, confirming that defective mitochondrial C12 oxidation is sufficient to induce the steatosis phenotype. Sirt5KO liver exhibited normal LCAD activity but reduced mitochondrial acyl-CoA synthetase activity with C12. These studies reveal a role for Sirt5 in regulating the hepatic response to MCT and may shed light into the pathogenesis of periportal steatosis, a hallmark of human pediatric non-alcoholic fatty liver disease.

Effects of Piceatannol and Resveratrol on Sirtuins and Hepatic Inflammation in High-Fat Diet-Fed Mice.

Piceatannol (PIC) is a natural hydroxylated analog of resveratrol (RSV) and considered as a potential metabolic regulator. The purpose of this study was to compare the effects of PIC and RSV on parameters affecting inflammation, oxidative stress, and sirtuins (Sirt). Male C57BL/6J mice, 20 weeks old, were assigned to the following groups; (1) lean control, (2) high-fat diet control (HF), (3) HF_PIC, and (4) HF_RSV. Oral administration of PIC and RSV (10 mg/kg/day) for 4 weeks improved glucose control as shown by decreasing levels of area under the curve (AUC) during the oral glucose tolerance test compared with HF group. PIC improved glycemic control by increasing hepatic levels of insulin receptor and AMP-activated protein kinase. PIC increased the levels of Sirt1, Sirt3, and Sirt6 and also increased two downstream targets of Sirt, peroxisome proliferator-activated receptor gamma coactivator 1-alpha and forkhead box O1, in the liver. The inflammatory markers, interleukin (IL)-1 and IL-6, in the liver were downregulated by RSV treatment. Exposure to PIC and RSV significantly lowered hepatic levels of tumor necrosis factor-alpha. However, PIC and RSV treatments showed minimal effects on hepatic markers of oxidative stress. The levels of antioxidant enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), were only increased in livers of RSV-treated mice compared with HF control mice. In conclusion, PIC was superior to an equal concentration of RSV in the regulation of Sirt and its downstream targets as well as insulin signaling-related parameters, while RSV potentially suppressed levels of proinflammatory markers and increased NQO1 protein levels.

Cardioprotective effects of Aconiti Lateralis Radix Praeparata combined with Zingiberis Rhizoma on doxorubicin-induced chronic heart failure in rats and potential mechanisms.

BACKGROUND: The combined use of Aconiti Lateralis Radix Praeparata (ALRP) and Zingiberis Rhizoma (ZR) are classic compatibilities in China for the treatment of cardiovascular diseases such as increasing myocardial contractility, anti-arrhythmia, reducing myocardial oxygen consumption, and dilating organ blood vessels, etc, thereby exerting anti-heart failure (HF) effects in traditional Chinese herbal medicine. However, comprehensive approaches for understanding the therapeutic effects and mechanisms underlying chronic heart failure (CHF) from the perspective of energy metabolism have not been pursued. AIM: This research was aimed to investigate the effectiveness and potential mechanism of ALRP combined with ZR (1:1) on doxorubicin (DOX)-induced CHF in rats based on an integrated approach that combines network pharmacology analyses and molecular biology. MATERIAL AND METHODS: CHF model was established by the intraperitoneal injection of DOX. ALRP and ZR were intragastrically administrated for three weeks. The detection indices including hemodynamic measurements, myocardial injury marker, and myocardial pathological changes were measured. Network pharmacology analysis was used to illustrate the pathways and network of ALRP and ZR against HF. Mitochondrial energy metabolism pathway associated gene and protein levels of PPARα, PGC-1α and Sirt3 in myocardial tissue were detected by real-time PCR and western blotting, respectively. RESULTS: The results indicated that ALRP-ZR herbal couple significantly improved the left ventricular function and cardiac enzyme activities in comparison with their single use. Network pharmacology analysis results showed that the pharmacological mechanisms of ALRP-ZR may be related to PPAR energy metabolism pathway. Besides, the outcomes of western-blot and real-time PCR analysis showed that ALRP-ZR significantly upregulates the protein and gene level of PPARα, PGC-1α, and Sirt3. CONCLUSIONS: Network pharmacology analysis would be an effective network analyze workflow which was feasible for evaluating the pharmacological effect of a multi-drug complex system. The Chinese herbal couple ALRP-ZR had a better therapeutic effect than their single-use against DOX-induced CHF, which may be related to enhancing left ventricular function by activating the PPARα/PGC-1α/Sirt3 pathway.

Hydrogen sulfide attenuates lung ischemia-reperfusion injury through SIRT3-dependent regulation of mitochondrial function in type 2 diabetic rats.

BACKGROUND: Lung ischemia-reperfusion injury is a complex pathophysiologic process associated with high morbidity and mortality. We have demonstrated elsewhere that diabetes mellitus aggravated ischemia-induced lung injury. Oxidative stress and mitochondrial dysfunction are drivers of diabetic lung ischemia-reperfusion injury; however, the pathways that mediate these events are unexplored. In this study using a high-fat diet-fed model of streptozotocin-induced type 2 diabetes in rats, we determined the effect of hydrogen sulfide on lung ischemia-reperfusion injury with a focus on Sirtuin3 signaling. METHODS: Rats with type 2 diabetes were exposed to GYY4137, a slow release donor of hydrogen sulfide with or without administration of the Sirtuin3 short hairpin ribonucleic acid plasmid, and then subjected to a surgical model of ischemia-reperfusion injury of the lung (n = 8). Lung function, oxidative stress, inflammation, cell apoptosis, and mitochondrial function were measured. RESULTS: Compared with nondiabetic rats, animals with type 2 diabetes at baseline exhibited significantly decreased Sirtuin3 signaling in lung tissue and increased oxidative stress, apoptosis, inflammation, and mitochondrial dysfunction (P < .05 each). In addition, further impairment in Sirtuin3 signaling was found in diabetic rats subjected to this model of lung ischemia-reperfusion. Simultaneously, the indexes showed further aggravation. Treatment with hydrogen sulfide restored Sirtuin3 expression and decreased lung ischemia-reperfusion injury in animals with type 2 diabetes mellitus by improving lung functional recovery, decreasing oxidative damage, suppressing inflammation, ameliorating cell apoptosis, and preserving mitochondrial function (P < .05). Conversely, these protective effects were largely reversed in Sirtuin3 knockdown rats. CONCLUSION: Impaired lung Sirtuin3 signaling associated with type 2 diabetic conditions was further attenuated by an ischemia-reperfusion insult. Hydrogen sulfide ameliorated reperfusion-induced oxidative stress and mitochondrial dysfunction via activation of Sirtuin3 signaling, thereby decreasing lung ischemia-reperfusion damage in rats with a model of type II diabetes.

Impact of dietary lipoic acid supplementation on liver mitochondrial bioenergetics and oxidative status on normally fed Wistar rats.

The aim of this study was to examine the effects of α-lipoic acid (α-LA) on liver mitochondrial bioenergetics and oxidative status for 8 weeks in normal-healthy animals. A pair-fed group was included to differentiate between α-LA direct effects and those changes due to reduced food intake. α-LA decreased body weight gain, liver weight and insulin levels with no differences compared to its pair-fed group. α-LA significantly reduced energy efficiency, the activity of the electron transport chain complexes and induced a lower efficiency of oxidative phosphorylation with reduced ATP production. α-LA supplementation directly decreased plasma triglycerides (TGs), free fatty acids and ketone bodies levels. A significant reduction in hepatic TG content was also observed. A significant up-regulation of Cpt1a, Acadl and Sirt3, all ß-oxidation genes, along with a significant deacetylation of the forkhead transcription factor 3a (FOXO3A) was found in α-LA-treated animals. Thus, α-LA along with a standard chow diet has direct actions on lipid metabolism and liver by modulating mitochondrial function in normal-weight rats. These results should be taken into account when α-LA is administered or recommended to a healthy population.

Sir-2.1 mediated attenuation of α-synuclein expression by Alaskan bog blueberry polyphenols in a transgenic model of Caenorhabditis elegans.

Misfolding and accumulation of cellular protein aggregates are pathological hallmarks of aging and neurodegeneration. One such protein is α-synuclein, which when misfolded, forms aggregates and disrupts normal cellular functions of the neurons causing Parkinson's disease. Nutritional interventions abundant in pharmacologically potent polyphenols have demonstrated a therapeutic role for combating protein aggregation associated with neurodegeneration. The current study hypothesized that Alaskan bog blueberry (Vaccinum uliginosum), which is high in polyphenolic content, will reduce α-synuclein expression in a model of Caenorhabditis elegans (C. elegans). We observed that blueberry extracts attenuated α-synuclein protein expression, improved healthspan in the form of motility and restored lipid content in the transgenic strain of C. elegans expressing human α-synuclein. We also found reduced gene expression levels of sir-2.1 (ortholog of mammalian Sirtuin 1) in blueberry treated transgenic animals indicating that the beneficial effects of blueberries could be mediated through partial reduction of sirtuin activity. This therapeutic effect of the blueberries was attributed to its xenohormetic properties. The current results highlight the role of Alaskan blueberries in mediating inhibition of sir-2.1 as a novel therapeutic approach to improving pathologies of protein misfolding diseases. Finally, our study warrants further investigation of the structure, and specificity of such small molecules from indigenous natural compounds and its role as sirtuin regulators.

NAD+ supplementation normalizes key Alzheimer's features and DNA damage responses in a new AD mouse model with introduced DNA repair deficiency.

Emerging findings suggest that compromised cellular bioenergetics and DNA repair contribute to the pathogenesis of Alzheimer's disease (AD), but their role in disease-defining pathology is unclear. We developed a DNA repair-deficient 3xTgAD/Polß+/- mouse that exacerbates major features of human AD including phosphorylated Tau (pTau) pathologies, synaptic dysfunction, neuronal death, and cognitive impairment. Here we report that 3xTgAD/Polß+/- mice have a reduced cerebral NAD+/NADH ratio indicating impaired cerebral energy metabolism, which is normalized by nicotinamide riboside (NR) treatment. NR lessened pTau pathology in both 3xTgAD and 3xTgAD/Polß+/- mice but had no impact on amyloid ß peptide (Aß) accumulation. NR-treated 3xTgAD/Polß+/- mice exhibited reduced DNA damage, neuroinflammation, and apoptosis of hippocampal neurons and increased activity of SIRT3 in the brain. NR improved cognitive function in multiple behavioral tests and restored hippocampal synaptic plasticity in 3xTgAD mice and 3xTgAD/Polß+/- mice. In general, the deficits between genotypes and the benefits of NR were greater in 3xTgAD/Polß+/- mice than in 3xTgAD mice. Our findings suggest a pivotal role for cellular NAD+ depletion upstream of neuroinflammation, pTau, DNA damage, synaptic dysfunction, and neuronal degeneration in AD. Interventions that bolster neuronal NAD+ levels therefore have therapeutic potential for AD.

Sesamin extends lifespan through pathways related to dietary restriction in Caenorhabditis elegans.

PURPOSE: Sesamin, a polyphenolic compound found in sesame seeds, has been reported to exert a variety of beneficial health effects. We have previously reported that sesamin increases the lifespan of Caenorhabditis elegans. In this study, we investigated the molecular mechanisms underlying the longevity effect of sesamin in C. elegans. METHODS: Starting from three days of age, Caenorhabditis elegans animals were fed a standard diet alone or supplemented with sesamin. A C. elegans genome array was used to perform a comprehensive expression analysis. Genes that showed differential expression were validated using real-time PCR. Mutant or RNAi-treated animals were fed sesamin, and the lifespan was determined to identify the genes involved in the longevity effects of sesamin. RESULTS: The microarray analysis revealed that endoplasmic reticulum unfolded protein response-related genes, which have been reported to show decreased expression under conditions of SIR-2.1/Sirtuin 1 (SIRT1) overexpression, were downregulated in animals supplemented with sesamin. Sesamin failed to extend the lifespan of sir-2.1 knockdown animals and of sir-2.1 loss-of-function mutants. Sesamin was also ineffective in bec-1 RNAi-treated animals; bec-1 is a key regulator of autophagy, and is necessary for longevity induced by sir-2.1 overexpression. Furthermore, the heterozygotic mutation of daf-15, which encodes the target of rapamycin (TOR)-binding partner Raptor, abolished lifespan extension by sesamin. Moreover, sesamin did not prolong the lifespan of loss-of-function mutants of aak-2, which encodes the AMP-activated protein kinase (AMPK). CONCLUSIONS: Sesamin extends the lifespan of C. elegans through several dietary restriction-related signaling pathways, including processes requiring SIRT1, TOR, and AMPK.

Arctiin regulates collagen type 1α chain 1 mRNA expression in human dermal fibroblasts via the miR­378b­SIRT6 axis.

Arctiin, a lignin isolated from Arctium lappa, exhibits a variety of biological effects, including anti­viral, anti­inflammatory, and anti­proliferative actions, in mammalian cells. In a previous study, arctiin was demonstrated to induce procollagen type I synthesis and exhibited protective effects against ultraviolet B (UVB) radiation in normal human dermal fibroblasts (nHDFs). However, the underlying molecular mechanism of arctiin­mediated collagen synthesis remains unknown. In the present study, the mechanism for increased expression of collagen type 1α 1 chain (COL1A1) mRNA in arctiin­induced nHDFs was identified. The expression of microRNA­378b (miR­378b), downregulated by arctiin, was correlated with the expression of sirtuin­6 (SIRT6) mRNA, a regulator of COL1A1 mRNA. Furthermore, it was revealed that arctiin protected the UVB radiation­mediated decrease in COL1A1 mRNA expression, through the miR­378b/SIRT6 signaling pathway. In conclusion, these results suggest that arctiin regulates COL1A1 through the miR­378b­SIRT6 axis.