Browsing by Subject "Sirtuins"

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  • Jokinen, Riikka; Pirnes-Karhu, Sini; Pietilainen, Kirsi H.; Pirinen, Eija (2017)
    Obesity, a chronic state of energy overload, is characterized by adipose tissue dysfunction that is considered to be the major driver for obesity associated metabolic complications. The reasons for adipose tissue dysfunction are incompletely understood, but one potential contributing factor is adipose tissue mitochondrial dysfunction. Derangements of adipose tissue mitochondrial biogenesis and pathways associate with obesity and metabolic diseases. Mitochondria are central organelles in energy metabolism through their role in energy derivation through catabolic oxidative reactions. The mitochondrial processes are dependent on the proper NAD(+)/NADH redox balance and NAD+ is essential for reactions catalyzed by the key regulators of mitochondrial metabolism, sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs). Notably, obesity is associated with disturbed adipose tissue NAD(+) homeostasis and the balance of SIRT and PARP activities. In this review we aim to summarize existing literature on the maintenance of intracellular NAD(+) pools and the function of SIRTs and PARPs in adipose tissue during normal and obese conditions, with the purpose of comprehending their potential role in mitochondrial derangements and obesity associated metabolic complications. Understanding the molecular mechanisms that are the root cause of the adipose tissue mitochondrial derangements is crucial for developing new effective strategies to reverse obesity associated metabolic complications.
  • Lensu, S.; Pekkala, S.P.; Mäkinen, A.; Karstunen, N.; Turpeinen, A.T.; Hulmi, J.J.; Silvennoinen, M.M.; Ma, H.; Kujala, U.M.; Karvinen, S.; Koch, L.G.; Britton, S.L.; Kainulainen, H. (2019)
    Background Physical activity and dietary intake of dairy products are associated with improved metabolic health. Dairy products are rich with branched chain amino acids that are essential for energy production. To gain insight into the mechanisms underlying the benefit of the sub-chronic effects of running and intake of milk protein supplements, we studied Low Capacity Runner rats (LCR), a rodent exercise model with risk for metabolic disorders. We especially focused on the role of Sirtuins, energy level dependent proteins that affect many cellular metabolic processes. Methods Forty-seven adult LCR female rats sedentary or running voluntarily in wheels were fed normal chow and given supplements of either whey or milk protein drink (PD)-supplemented water, or water only for 21 weeks. Physiological responses were measured in vivo. Blood lipids were determined from serum. Mitochondrial markers and Sirtuins (Sirt1-7) including downstream targets were measured in plantaris muscle by western blotting. Results For the first 10 weeks whey-drinking rats ran about 50% less compared to other groups; still, in all runners glucose tolerance improved and triglycerides decreased. Generally, running induced a ∼six-fold increase in running capacity and a ∼8% decrease in % body fat. Together with running, protein supplements increased the relative lean mass of the total body weight by ∼11%. In comparison with sedentary controls, running and whey increased HDL (21%) and whey, with or without running, lowered LDL (−34%). Running increased mitochondrial biogenesis and Sirtuins 3 and 4. When combined with exercise, both whey and milk protein drink induced about a 4-fold increase in Sirt3, compared to runners drinking water only, and about a 2-fold increase compared to the respective sedentary group. Protein supplements, with or without running, enhanced the phosphorylation level of the acetyl-coA-carboxylase, suggesting increased fat oxidation. Both supplemented diets increased Sirt5 and Sirt7 without an additional effect from exercise. Running diminished and PD supplement increased Sirt6. Conclusion We demonstrate in rats new sub-chronic effects of milk proteins on metabolism that involve Sirtuins and their downstream targets in skeletal muscle. The results show that running and milk proteins act on reducing the risk factors of metabolic disorders and suggest that the underlying mechanisms may involve Sirtuins. Notably, we found that milk protein supplements have some favorable effects on metabolism even without running.
  • Yoo, Bo Ram (Helsingfors universitet, 2017)
    Cardiovascular disease is one of the leading causes of mortality worldwide. Upon myocardial infarction, billions of cardiomyocytes are lost, a fibrotic scar forms, and the heart's contractile function is compromised. Mammalian cardiomyocytes lose most of their proliferative capacity shortly after birth. This decline in proliferative capacity is associated with a switch from glycolysis to oxidative phosphorylation, yielding more ATP, but also inevitably forming reactive oxygen species (ROS). Therefore, finding a way to extend the proliferative window seems crucial to cardiac repair. microRNAs (miRNAs) are short, single-stranded noncoding RNAs that repress gene expression after transcription by binding to their target mRNAs. SIRT1-7, mammalian homologs of the Sirt2 protein in yeast, have been implicated in the regulation of metabolic homeostasis, cell proliferation, cardiac hypertrophy, and aging. The objective of our research was to investigate the differential expression of SIRT1-7 between day 1 and day 7 neonatal mice. Since cells continue to divide until day 7, we wanted to compare the differences in sirtuin expression during the two time points. By doing so, we hoped to gain insight into ways we could regulate sirtuin protein expression by manipulating miRNA and sirtuin gene expression in diseased hearts, thereby promoting the fetal gene program and inducing cells to reenter the cell cycle. Proteins were isolated from whole cell lysates of cardiac tissue of day 1 and day 7 neonatal mice, and western blotting technique was used to analyze SIRT1-7 expression. Expression of SIRT3 and 7 was significantly higher in day 7 as opposed to day 1 in at least two of the three runs, with SIRT7 levels being higher in day 7 in all three runs. Our study provides a basis for carrying out more quantitative analysis to validate gene and protein expression and protein activity, since expression is different at the gene and protein levels and does not necessarily translate into activity.
  • Demyanenko, Svetlana; Gantsgorn, Elena; Rodkin, Stanislav; Sharifulina, Svetlana (2020)
    Sirtuins, class III histone deacetylases, are involved in the regulation of tissue repair processes and brain functions after a stroke. The ability of some isoforms of sirtuins to circulate between the nucleus and cytoplasm may have various pathophysiological effects on the cells. In present work, we focused on the role of non-mitochondrial sirtuins SIRT1, SIRT2, and SIRT6 in the restoration of brain cells following ischemic stroke. Here, using a photothrombotic stroke (PTS) model in mice, we studied whether local stroke affects the level and intracellular localization of SIRT1, SIRT2, and SIRT6 in neurons and astrocytes of the intact cerebral cortex adjacent to the ischemic ipsilateral hemisphere and in the analogous region of the contralateral hemisphere at different time points during the recovery period after a stroke. We evaluated the co-localization of sirtuins with growth-associated protein-43 (GAP 43), the presynaptic marker synaptophysin (SYN) and acetylated a-tubulin (Aca-Tub), that are associated with brain plasticity and are known to be involved in brain repair after a stroke. The results show that during the recovery period, an increase in SIRT1 and SIRT2 levels occurred. The increase of SIRT1 level was associated with an increase in synaptic plasticity proteins, whereas the increase of SIRT2 level was associated with an acetylated of a-tubulin, that can reduce the mobility of neurites. SIRT6 co-localized with GAP-43, but not with SYN. Moreover, we showed that SIRT1, SIRT2, and SIRT6 are not involved in the PTS-induced apoptosis of pen umbra cells. Taken together, our results suggest that sirtuins functions differ depending on cell type, intracellular localization, specificity of sirtuins isoforms to different substrates and nature of post-translational modifications of enzymes.
  • Heiskanen, Vladimir; Pirinen, Eija (2020)
    Viime vuosina on julkaistu uusia havaintoja mitokondrioiden toimintahäiriöistä yhtenä osana lihavuuden ja sen liitännäissairauksien patofysiologista profiilia. Mitokondrioiden määrän, toiminnan ja rakenteen muutokset liittyvät sairaustilojen syntymiseen, ja mitokondriot todennäköisesti myötävaikuttavat aineenvaihdunnan häiriöiden kehittymisessä. Koe-eläimillä näitä muutoksia on onnistuttu ehkäisemään aktivoimalla solunsisäisiä sirtuiinientsyymejä (SIRT1 - 7), jotka säätelevät solussa laajasti mitokondrioiden toimintaa, tulehdusprosesseja ja antioksidanttipuolustusta muokkaamalla proteiinien aktiivisuutta ja geenien luentaa. B3-vitamiinien on havaittu lisäävän sirtuiinien substraattina toimivan nikotiiniamidiadeniinidinukleotidin (NAD+) pitoisuutta solun sisällä, mikä on sirtuiinien aktiivisuutta lisäämällä parantanut terveyttä lihavuuden, diabeteksen sekä muiden kroonisten aineenvaihduntasairauksien eläinmalleissa. B3-vitamiinien vaikutuksia näihin sairauksiin arvioidaan myös käynnissä olevissa kliinisissä tutkimuksissa. Ensimmäisten kliinisten kokeiden perusteella B3-vitamiinien vaikutukset ihmisillä ovat lupaavia mutta kokonaisvaikutukset ovat vielä epäselvät.
  • Jukarainen, Sakari; Heinonen, Sini; Rämö, Joel; Rinnankoski-Tuikka, Rita; Rappou, Elisabeth; Tummers, Mark; Muniandy, Maheswary; Hakkarainen, Antti; Lundbom, Jesper; Lundbom, Nina; Kaprio, Jaakko; Rissanen, Aila; Pirinen, Eija; Pietiläinen, Kirsi (Helsingfors universitet, 2016)
    Context: Sirtuins (SIRTs) regulate cellular metabolism and mitochondrial function according to the energy state of the cell reflected by NAD+‚ levels. Objective: Our aim was to determine whether expressions of SIRTs and NAD+‚ biosynthesis genes are affected by acquired obesity and how possible alterations are connected with metabolic dys-function while controlling for genetic and familial factors. Design and Participants: We studied a cross-sectional sample of 40 healthy pairs of monozygotic twins, including 26 pairs who were discordant for body mass index (within-pair difference +ƒ 3 kg/m2), from the FinnTwin12 and FinnTwin16 cohorts. Main Outcome Measures: Subcutaneous adipose tissue (SAT) transcriptomics was analyzed by using Affymetrix U133 Plus 2.0 chips, total SAT (poly-ADP) ribose polymerase (PARP) activity by an ELISA kit, body composition by dual-energy x-ray absorptiometry and magnetic resonance imaging/spectroscopy, and insulin sensitivity by an oral glucose tolerance test. Results: SIRT1, SIRT3, SIRT5, NAMPT, NMNAT2, NMNAT3, and NRK1 expressions were significantly down-regulated and the activity of main cellular NAD+‚ consumers, PARPs, trended to be higher in the SAT of heavier cotwins of body mass index–discordant pairs. Controlling for twin-shared factors, SIRT1, SIRT3, NAMPT, NMNAT3, and NRK1 were significantly negatively correlated with adiposity, SIRT1, SIRT5, NMNAT2, NMNAT3, and NRK1 were negatively correlated with inflammation, and SIRT1 and SIRT5 were positively correlated with insulin sensitivity. Expressions of genes involved in mitochondrial unfolded protein response were also significantly down-regulated in the heavier cotwins. Conclusions: Our data highlight a strong relationship of reduced NAD+‚/SIRT pathway expression with acquired obesity, inflammation, insulin resistance, and impaired mitochondrial protein homeostasis in SAT.