srt1460 and Diabetes-Mellitus--Type-2

Sirtuins catalyze NAD(+)-dependent protein deacetylation and are critical regulators of transcription, apoptosis, metabolism, and aging. There are seven human sirtuins (SIRT1-7), and SIRT1 has been implicated as a key mediator of the pathways downstream of calorie restriction that have been shown to delay the onset and reduce the incidence of age-related diseases such as type 2 diabetes. Increasing SIRT1 activity, either by transgenic overexpression of the Sirt1 gene in mice or by pharmacological activation by small molecule activators resveratrol and SRT1720, has shown beneficial effects in rodent models of type 2 diabetes, indicating that SIRT1 may represent an attractive therapeutic target. Herein, we have assessed purported SIRT1 activators by employing biochemical assays utilizing native substrates, including a p53-derived peptide substrate lacking a fluorophore as well as the purified native full-length protein substrates p53 and acetyl-CoA synthetase1. SRT1720, its structurally related compounds SRT2183 and SRT1460, and resveratrol do not lead to apparent activation of SIRT1 with native peptide or full-length protein substrates, whereas they do activate SIRT1 with peptide substrate containing a covalently attached fluorophore. Employing NMR, surface plasmon resonance, and isothermal calorimetry techniques, we provide evidence that these compounds directly interact with fluorophore-containing peptide substrates. Furthermore, we demonstrate that SRT1720 neither lowers plasma glucose nor improves mitochondrial capacity in mice fed a high fat diet. SRT1720, SRT2183, SRT1460, and resveratrol exhibit multiple off-target activities against receptors, enzymes, transporters, and ion channels. Taken together, we conclude that SRT1720, SRT2183, SRT1460, and resveratrol are not direct activators of SIRT1.

Topics: Acetylation; Allosteric Regulation; Animals; Blood Glucose; Calorimetry; Diabetes Mellitus, Type 2; Dietary Fats; Enzyme Activation; Enzyme Inhibitors; Heterocyclic Compounds, 4 or More Rings; Humans; Mice; Mice, Obese; Nuclear Magnetic Resonance, Biomolecular; Resveratrol; Rhodamines; Sirtuin 1; Stilbenes; Substrate Specificity; Surface Plasmon Resonance; Tumor Suppressor Protein p53

A series of imidazo[1,2-b]thiazole derivatives is shown to activate the NAD(+)-dependent deacetylase SIRT1, a potential new therapeutic target to treat various metabolic disorders. This series of compounds was derived from a high throughput screening hit bearing an oxazolopyridine core. Water-solubilizing groups could be installed conveniently at either the C-2 or C-3 position of the imidazo[1,2-b]thiazole ring. The SIRT1 enzyme activity could be adjusted by modifying the amide portion of these imidazo[1,2-b]thiazole derivatives. The most potent analogue within this series, namely, compound 29, has demonstrated oral antidiabetic activity in the ob/ob mouse model, the diet-induced obesity (DIO) mouse model, and the Zucker fa/fa rat model.

Topics: Animals; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Enzyme Activators; Hypoglycemic Agents; Imidazoles; Mice; Quinoxalines; Rats; Rats, Zucker; Sirtuin 1; Structure-Activity Relationship; Thiazoles

Calorie restriction extends lifespan and produces a metabolic profile desirable for treating diseases of ageing such as type 2 diabetes. SIRT1, an NAD+-dependent deacetylase, is a principal modulator of pathways downstream of calorie restriction that produce beneficial effects on glucose homeostasis and insulin sensitivity. Resveratrol, a polyphenolic SIRT1 activator, mimics the anti-ageing effects of calorie restriction in lower organisms and in mice fed a high-fat diet ameliorates insulin resistance, increases mitochondrial content, and prolongs survival. Here we describe the identification and characterization of small molecule activators of SIRT1 that are structurally unrelated to, and 1,000-fold more potent than, resveratrol. These compounds bind to the SIRT1 enzyme-peptide substrate complex at an allosteric site amino-terminal to the catalytic domain and lower the Michaelis constant for acetylated substrates. In diet-induced obese and genetically obese mice, these compounds improve insulin sensitivity, lower plasma glucose, and increase mitochondrial capacity. In Zucker fa/fa rats, hyperinsulinaemic-euglycaemic clamp studies demonstrate that SIRT1 activators improve whole-body glucose homeostasis and insulin sensitivity in adipose tissue, skeletal muscle and liver. Thus, SIRT1 activation is a promising new therapeutic approach for treating diseases of ageing such as type 2 diabetes.

Topics: Acetylation; Allosteric Site; Animals; Blood Glucose; Caloric Restriction; Catalytic Domain; Cell Line; Diabetes Mellitus, Type 2; Dietary Fats; Disease Models, Animal; Drosophila melanogaster; Heterocyclic Compounds, 4 or More Rings; Humans; Insulin; Male; Mice; Mitochondria; Rats; Rats, Sprague-Dawley; Rats, Zucker; Resveratrol; Sirtuin 1; Sirtuins; Stilbenes