Sirtuins are a family of Class III epigenetic modifying enzymes involved in regulating cellular processes through the removal of acetyl groups from proteins. They rely on NAD+ as a coenzyme in contrast with classical HDACs (Class I, II, and IV) that depends on Zn+ for their activation, linking their function to cellular energy levels. There are seven mammalian sirtuin isoforms (SIRT1-7), each located in different subcellular compartments. Sirtuins act as master regulators of cellular homeostasis, responding to changes in nutrient availability and energy status. They play vital roles in diverse physiological and pathological conditions, making them promising therapeutic targets for various diseases, including cancer, neurodegenerative disorders, and metabolic diseases. High levels of SIRT6 are involved in the cancer progression of many tumor types and our previous studies revealed that sirtuin 6 was highly expressed in NSCLC cells and its inhibition potentially favored apoptosis and cell cycle arrest. Sirt6 emerged as a promising target and inhibitors of natural and synthetic sources are highly warranted. Imidazole derivatives are often investigated as sirtuin regulators due to their ability to interact with the binding site and modulate their activity. Imidazole bestows many possible substitutions on its ring and neighboring atoms, to design and synthesize derivatives with specific target selectivity and improved pharmacokinetic properties, optimizing drug development. We recently developed imidazole-based derivatives that potentially inhibited classical HDAC enzymes. Therefore, we evaluated the Sirtuin inhibition activity of our in-house compound comprised of imidazole derivatives and the strongest inhibition was observed with Ethyl 2-[5-(4-chlorophenyl)-2-methyl-1-H-Imidazole-4-yl) acetate against Sirt6 by in-silico and protein expression studies. Our results suggested that Ethyl 2-[5-(4-chlorophenyl)-2-methyl-1-H-Imidazole-4-yl) acetate could be a potential novel sirt6 inhibitor.

Cancer cells show an increased glutamine consumption. The glutaminase (GLS) enzyme controls a limiting step in the glutamine catabolism. Breast tumors, especially the triple negative subtype, have a high expression of GLS. Our recent study demonstrated that GLS activity and ammonia production are inhibited by Sirtuin 5 (SIRT5). We have developed MC3138, a selective SIRT5 activator. Treatment with MC3138 mimicked the deacetylation effect mediated by SIRT5 overexpression. Moreover, GLS activity is regulated by inorganic phosphate (Pi). Considering the interconnected role of GLS, SIRT5 and Pi for cancer growth, our hypothesis is that activation of SIRT5 and reduction of Pi could represent a valid anti-tumoral strategy. Treating cells with MC3138 and lanthanum acetate, a Pi chelator, decreased cell viability and clonogenicity. We also observed a modulation of LC3 and ULK1 with MC3138 and lanthanum acetate. Interestingly, inhibition of mitophagy marker BNIP3 was observed only in the presence of MC3138. Such autophagy and mitophagy modulation was accompanied by an increase of cytosolic and mitochondrial reactive oxygen species (ROS). In conclusion, our results show how SIRT5 activation and/or Pi binding can represent a valid strategy to inhibit cell proliferation by reducing glutamine metabolism and mitophagy leading to a deleterious accumulation of ROS.

Sirtuins, especially SIRT1, play a significant role in the regulation of inflammatory response, autophagy, and cell response to oxidative stress. Since their discovery, sirtuins have been regarded as anti-aging and longevity-promoting enzymes. Sirtuin-regulated processes seem to take part in most prevalent placental pathologies, such as preeclampsia. Furthermore, more and more research studies indicate that SIRT1 may prevent pre-eclampsia development, or at least alleviate its manifestations. Having taken this into consideration, we have made a review of recent studies on the role of sirtuins, especially SIRT1, in the regulation of processes determining normal or abnormal development and functioning of the placenta.

Alzheimer's disease (AD) has been the subject of extensive investigation as to its biological underpinnings. However, this has produced little of therapeutic benefit or indeed provided any accepted biomarkers that could tailor treatment. This chapter reviews data on the main pathophysiologic processes that have been widely shown to be altered in AD, including circadian dysregulation, mitochondrial dysfunction, gut dysbiosis, and immune-glia-platelet activation. It is proposed that alterations in the gut microbiome, including gut dysbiosis and increased gut permeability drive changes in mitochondrial function that are intimately associated with significant variations in sirtuin expression. Both mitochondria-located and nucleus/cytoplasm located sirtuins can act on mitochondrial function in different cells and body systems to co-ordinate the ageing-associated changes that underpin AD. The sirtuins are therefore key aspect to a developmental model of AD that is more 'holistic' in perspective, thereby providing a framework for the detection of earlier biomarkers and more successful treatment for the heterogenous nature of AD pathoetiology.

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into 4 different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting the novel interventional strategies for metabolic disorders/complications.