Small molecule activators of SIRT1 replicate signaling pathways triggered by calorie restriction in vivo

<p>Abstract</p> <p>Background</p> <p>Calorie restriction (CR) produces a number of health benefits and ameliorates diseases of aging such as type 2 diabetes. The components of the pathways downstream of CR may provide intervention points for developing therapeutics for treating diseases of aging. The NAD⁺-dependent protein deacetylase SIRT1 has been implicated as one of the key downstream regulators of CR in yeast, rodents, and humans. Small molecule activators of SIRT1 have been identified that exhibit efficacy in animal models of diseases typically associated with aging including type 2 diabetes. To identify molecular processes induced in the liver of mice treated with two structurally distinct SIRT1 activators, SIRT501 (formulated resveratrol) and SRT1720, for three days, we utilized a systems biology approach and applied Causal Network Modeling (CNM) on gene expression data to elucidate downstream effects of SIRT1 activation.</p> <p>Results</p> <p>Here we demonstrate that SIRT1 activators recapitulate many of the molecular events downstream of CR <it>in vivo</it>, such as enhancing mitochondrial biogenesis, improving metabolic signaling pathways, and blunting pro-inflammatory pathways in mice fed a high fat, high calorie diet.</p> <p>Conclusion</p> <p>CNM of gene expression data from mice treated with SRT501 or SRT1720 in combination with supporting <it>in vitro </it>and <it>in vivo </it>data demonstrates that SRT501 and SRT1720 produce a signaling profile that mirrors CR, improves glucose and insulin homeostasis, and acts via SIRT1 activation <it>in vivo</it>. Taken together these results are encouraging regarding the use of small molecule activators of SIRT1 for therapeutic intervention into type 2 diabetes, a strategy which is currently being investigated in multiple clinical trials.</p

Efek Ekstrak Kemangi (Ocimum basilicum L) terhadap Ekspresi Sirtuin 1 (SIRT1), Peroxisome Proliferator Activated Receptors γ (PPARγ), dan Histologi Hepar pada Tikus Model Diabetes Melitus Gestasional

Diabetes Melitus Gestasional adalah penyakit kelainan metabolisme karbohidrat yang menyebabkan kondisi hiperglikemia dan resistensi insulin selama kehamilan. Sirtuin 1 (SIRT1) dan Peroxisome Proliferator Activated Receptorγ (PPARγ) adalah gen yang berperan dalam metabolisme glukosa dan disregulasi gen ini berasosiasi dengan kejadian Diabetes Melitus Gestasional (DMG). Ekstrak kemangi (Ocimum basilicum) dilaporkan dapat menurunkan kadar glukosa darah karena kandungan zat aktifnya. Penelitian ini bertujuan untuk melihat efekt ektrak kemangi (Ocimum basilicum) terhadap ekspresi SIRT 1 dan PPAR γ pada tikus model DMG. Penelitian ini dilakukan pada 24 ekor tikus hamil. Sampe dibagi menjadi 4 kelompok yaitu kelompok tikus hamil sehat, kelompok positif yang diinduksi streptozosin 40 mg/KgBB intraperitoneal, dan 2 kelompok tikus DMG yang diberi perlakuan 100 mg/KgBB (P1) dan 200 mg/KgBB (P2) ekstrak kemangi selama 14 hari. Kadar glukosa darah diperiksa dengan blood glucose meter, ekspresi SIRT 1 dan PPAR γ dinilai dengan metode RT-PCR. Penilaian histologi hati tikus model juga dilakukan dengan pewarnaan Hematoxyline Eosin untuk menilai efek ekstrak kamangi pada organ hati. Hasil penelitian menunjukan pemberian ekstrak kemangi (Ocimum basilicum) pada dosis 200 mg/KgBB terbukti dapat meningkatkan ekspresi SIRT 1 dengan nilai p= 0,035 (p <0,05) namun tidak terbukti berpengaruh terhadap ekspresi PPARγ. Pewarnaan HE pada organ hati memperlihatkan adanya kecenderungan perbaikan pada kelompok yang diberi ekstrak kemangi dimana persentase kerusakan sel cenderung menurun setelah pemberian ekstrak kemangi yaitu dari 70,0% pada kelompok tikus DMG menjadi 44,7% pada kelompok P1 dan 44,3 % pada perlakuan kelompok P2. Persentase porposi edema jaringan juga cenderung mengalami penurunan yaitu 49,5% pada kelompok tikus DMG menjadi 39,4% pada P1 dan 38,8% pada P2. Dapat disimpulkan bahwa ekstrak daun kemangi dapat meningkatkan ekspresi SIRT 1 dan berpotensi menjadi terapi hiperglikemia yang memberi efek hepataoprotktor. Kata kunci: Diabetes Melitus Gestasional, Glukosa, SIRT1, PPAR γ, Ocimum basilicum, metabolism

The Lifespan Extension Effects of Resveratrol are Conserved in the Honey Bee and May Be Driven by a Mechanism Related to Caloric Restriction

Our interest in healthy aging and in evolutionarily conserved mechanisms of lifespan extension prompted us to investigate whether features of age-related decline in the honey bee could be attenuated with resveratrol. Resveratrol is regarded as a caloric restriction mimetic known to extend lifespan in some but not all model species. The current, prevailing view is that resveratrol works largely by activating signaling pathways. It has also been suggested that resveratrol may act as an antioxidant and confer protection against nervous system impairment and oxidative stress. To test whether honey bee lifespan, learning performance, and food perception could be altered by resveratrol, we supplemented the diets of honey bees and measured lifespan, olfactory learning, and gustatory responsiveness to sucrose. Furthermore, to test the effects of resveratrol under metabolic challenge, we used hyperoxic environments to generate oxidative stress. Under normal oxygen conditions, two resveratrol treatments—30 and 130 μM—lengthened average lifespan in wild-type honey bees by 38% and 33%, respectively. Both resveratrol treatments also lengthened maximum and median lifespan. In contrast, hyperoxic stress abolished the resveratrol life-extension response. Furthermore, resveratrol did not affect learning performance, but did alter gustation. Honey bees that were not fed resveratrol exhibited greater responsiveness to sugar, while those supplemented with resveratrol were less responsive to sugar. We also discovered that individuals fed a high dose of resveratrol—compared to controls—ingested fewer quantities of food under ad libitum feeding conditions

Resveratrol-induced cytotoxicity in human Burkitt's lymphoma cells is coupled to the unfolded protein response

<p>Abstract</p> <p>Background</p> <p>Resveratrol (RES), a natural phytoalexin found at high levels in grapes and red wine, has been shown to induce anti-proliferation and apoptosis of human cancer cell lines. However, the underlying molecular mechanisms are at present only partially understood.</p> <p>Method</p> <p>The effects of RES on activation of unfolded protein responses (UPR) were evaluated using Western blotting, semi-quantitative and real-time RT-PCR. Cell death was evaluated using Annexin V/PI staining and subsequent FACS.</p> <p>Results</p> <p>Similar as tunicamycin, treatment with RES lead to the activation of all 3 branches of the UPR, with early splicing of XBP-1 indicative of IRE1 activation, phosphorylation of eIF2α consistent with ER resident kinase (PERK) activation, activating transcription factor 6 (ATF6) splicing, and increase in expression levels of the downstream molecules GRP78/BiP, GRP94 and CHOP/GADD153 in human Burkitt's lymphoma Raji and Daudi cell lines. RES was shown to induce cell death, which could be attenuated by thwarting upregulation of CHOP.</p> <p>Conclusions</p> <p>Our data suggest that activation of the apoptotic arm of the UPR and its downstream effector CHOP/GADD153 is involved, at least in part, in RES-induced apoptosis in Burkitt's lymphoma cells.</p

Comparative Transcriptional Network Modeling of Three PPAR-α/γ Co-Agonists Reveals Distinct Metabolic Gene Signatures in Primary Human Hepatocytes

Aims: To compare the molecular and biologic signatures of a balanced dual peroxisome proliferator-activated receptor (PPAR)-α/γ agonist, aleglitazar, with tesaglitazar (a dual PPAR-α/γ agonist) or a combination of pioglitazone (Pio; PPAR-γ agonist) and fenofibrate (Feno; PPAR-α agonist) in human hepatocytes. Methods and Results: Gene expression microarray profiles were obtained from primary human hepatocytes treated with EC50-aligned low, medium and high concentrations of the three treatments. A systems biology approach, Causal Network Modeling, was used to model the data to infer upstream molecular mechanisms that may explain the observed changes in gene expression. Aleglitazar, tesaglitazar and Pio/Feno each induced unique transcriptional signatures, despite comparable core PPAR signaling. Although all treatments inferred qualitatively similar PPAR-α signaling, aleglitazar was inferred to have greater effects on high- and low-density lipoprotein cholesterol levels than tesaglitazar and Pio/Feno, due to a greater number of gene expression changes in pathways related to high-density and low-density lipoprotein metabolism. Distinct transcriptional and biologic signatures were also inferred for stress responses, which appeared to be less affected by aleglitazar than the comparators. In particular, Pio/Feno was inferred to increase NFE2L2 activity, a key component of the stress response pathway, while aleglitazar had no significant effect. All treatments were inferred to decrease proliferative signaling. Conclusions: Aleglitazar induces transcriptional signatures related to lipid parameters and stress responses that are unique from other dual PPAR-α/γ treatments. This may underlie observed favorable changes in lipid profiles in animal and clinical studies with aleglitazar and suggests a differentiated gene profile compared with other dual PPAR-α/γ agonist treatments

SRT1720 improves survival and healthspan of obese mice

Sirt1 is an NAD+-dependent deacetylase that extends lifespan in lower organisms and improves metabolism and delays the onset of age-related diseases in mammals. Here we show that SRT1720, a synthetic compound that was identified for its ability to activate Sirt1 in vitro, extends both mean and maximum lifespan of adult mice fed a high-fat diet. This lifespan extension is accompanied by health benefits including reduced liver steatosis, increased insulin sensitivity, enhanced locomotor activity and normalization of gene expression profiles and markers of inflammation and apoptosis, all in the absence of any observable toxicity. Using a conditional SIRT1 knockout mouse and specific gene knockdowns we show SRT1720 affects mitochondrial respiration in a Sirt1- and PGC-1α-dependent manner. These findings indicate that SRT1720 has long-term benefits and demonstrate for the first time the feasibility of designing novel molecules that are safe and effective in promoting longevity and preventing multiple age-related diseases in mammals

Utilizing small nutrient compounds as enhancers of exercise-induced mitochondrial biogenesis.

Endurance exercise, when performed regularly as part of a training program, leads to increases in whole-body and skeletal muscle-specific oxidative capacity. At the cellular level, this adaptive response is manifested by an increased number of oxidative fibers (Type I and IIA myosin heavy chain), an increase in capillarity and an increase in mitochondrial biogenesis. The increase in mitochondrial biogenesis (increased volume and functional capacity) is fundamentally important as it leads to greater rates of oxidative phosphorylation and an improved capacity to utilize fatty acids during sub-maximal exercise. Given the importance of mitochondrial biogenesis for skeletal muscle performance, considerable attention has been given to understanding the molecular cues stimulated by endurance exercise that culminate in this adaptive response. In turn, this research has led to the identification of pharmaceutical compounds and small nutritional bioactive ingredients that appear able to amplify exercise-responsive signaling pathways in skeletal muscle. The aim of this review is to discuss these purported exercise mimetics and bioactive ingredients in the context of mitochondrial biogenesis in skeletal muscle. We will examine proposed modes of action, discuss evidence of application in skeletal muscle in vivo and finally comment on the feasibility of such approaches to support endurance-training applications in humans