Identification of a SIRT1 mutation in a family with type 1 diabetes

Mesenchymal stromal cells ameliorate mitochondrial dysfunction in α cells and hyperglucagonemia in type 2 diabetes via SIRT1/FoxO3a signaling

Dysregulation of α cells results in hyperglycemia and hyperglucagonemia in type 2 diabetes mellitus (T2DM). Mesenchymal stromal cell (MSC)-based therapy increases oxygen consumption of islets and enhances insulin secretion. However, the underlying mechanism for the protective role of MSCs in α-cell mitochondrial dysfunction remains unclear. Here, human umbilical cord MSCs (hucMSCs) were used to treat 2 kinds of T2DM mice and αTC1-6 cells to explore the role of hucMSCs in improving α-cell mitochondrial dysfunction and hyperglucagonemia. Plasma and supernatant glucagon were detected by enzyme-linked immunosorbent assay (ELISA). Mitochondrial function of α cells was assessed by the Seahorse Analyzer. To investigate the underlying mechanisms, Sirtuin 1 (SIRT1), Forkhead box O3a (FoxO3a), glucose transporter type1 (GLUT1), and glucokinase (GCK) were assessed by Western blotting analysis. In vivo, hucMSC infusion improved glucose and insulin tolerance, as well as hyperglycemia and hyperglucagonemia in T2DM mice. Meanwhile, hucMSC intervention rescued the islet structure and decreased α- to β-cell ratio. Glucagon secretion from αTC1-6 cells was consistently inhibited by hucMSCs in vitro. Meanwhile, hucMSC treatment activated intracellular SIRT1/FoxO3a signaling, promoted glucose uptake and activation, alleviated mitochondrial dysfunction, and enhanced ATP production. However, transfection of SIRT1 small interfering RNA (siRNA) or the application of SIRT1 inhibitor EX-527 weakened the therapeutic effects of hucMSCs on mitochondrial function and glucagon secretion. Our observations indicate that hucMSCs mitigate mitochondrial dysfunction and glucagon hypersecretion of α cells in T2DM via SIRT1/FoxO3a signaling, which provides novel evidence demonstrating the potential for hucMSCs in treating T2DM.

Human SIRT5 variants with reduced stability and activity do not cause neuropathology in mice

SIRT5 is a sirtuin deacylase that removes negatively charged lysine modifications, in the mitochondrial matrix and elsewhere in the cell. In benign cells and mouse models, under basal conditions, the phenotypes of SIRT5 deficiency are quite subtle. Here, we identify two homozygous SIRT5 variants in patients suspected to have mitochondrial disease. Both variants, P114T and L128V, are associated with reduced SIRT5 protein stability and impaired biochemical activity, with no evidence of neomorphic or dominant negative properties. The crystal structure of the P114T enzyme was solved and shows only subtle deviations from wild-type. Via CRISPR-Cas9, we generated a mouse model that recapitulates the human P114T mutation; homozygotes show reduced SIRT5 levels and activity, but no obvious metabolic abnormalities, neuropathology, or other gross phenotypes. We conclude that these human SIRT5 variants most likely represent severe hypomorphs, but are likely not by themselves the primary pathogenic cause of the neuropathology observed in the patients.

Effect of SIRT1 gene single-nucleotide polymorphisms on susceptibility to type 1 diabetes in a Han Chinese population

AIMS

SIRT1 deficiency has been associated with diabetes, and a variant of the SIRT1 gene has been found to be involved in human autoimmune diabetes; however, it is unclear whether this genetic variation exists in Han Chinese with type 1 diabetes (T1D) and whether it contributes to development of T1D. Therefore, we aimed to explore the association of the SIRT1 gene single-nucleotide polymorphisms (SNPs) rs10997866 and rs3818292 in a Han Chinese population with T1D.

METHODS

This study recruited 2653 unrelated Han Chinese individuals, of whom 1289 had T1D and 1364 were healthy controls. Allelic and genotypic distributions of SIRT1 polymorphisms (rs10997866 and rs3818292) were determined by MassARRAY. Basic characteristics, genotype and allele frequencies of selected SNPs were compared between the T1D patients and healthy controls. Further genotype-phenotype association analysis of the SNPs was performed on the T1D patients divided into three groups according to genotype. Statistical analyses included the chi-square test, Mann‒Whitney U test, Kruskal‒Wallis H test and logistic regression.

RESULTS

The allelic (G vs. A) and genotypic (GA vs. AA) distributions of SIRT1 rs10997866 were significantly different in T1D patients and healthy controls (P = 0.039, P = 0.027), and rs10997866 was associated with T1D susceptibility under dominant, overdominant and additive models (P = 0.026, P = 0.030 and P = 0.027, respectively). Moreover, genotype-phenotype association analysis showed the GG genotype of rs10997866 and the GG genotype of rs3818292 to be associated with higher titers of IA-2A (P = 0.013 and P = 0.038, respectively).

CONCLUSION

SIRT1 rs10997866 is significantly associated with T1D susceptibility, with the minor allele G conferring a higher risk of T1D. Moreover, SIRT1 gene rs10997866 and rs3818292 correlate with the titer of IA-2A in Han Chinese individuals with T1D.

SIRT5 variants from patients with mitochondrial disease are associated with reduced SIRT5 stability and activity, but not with neuropathology

SIRT5 is a sirtuin deacylase that represents the major activity responsible for removal of negatively-charged lysine modifications, in the mitochondrial matrix and elsewhere in the cell. In benign cells and mouse models, under basal non-stressed conditions, the phenotypes of SIRT5 deficiency are generally quite subtle. Here, we identify two homozygous SIRT5 variants in human patients suffering from severe mitochondrial disease. Both variants, P114T and L128V, are associated with reduced SIRT5 protein stability and impaired biochemical activity, with no evidence of neomorphic or dominant negative properties. The crystal structure of the P114T enzyme was solved and shows only subtle deviations from wild-type. Via CRISPR-Cas9, we generate a mouse model that recapitulates the human P114T mutation; homozygotes show reduced SIRT5 levels and activity, but no obvious metabolic abnormalities, neuropathology or other gross evidence of severe disease. We conclude that these human SIRT5 variants most likely represent severe hypomorphs, and are likely not the primary pathogenic cause of the neuropathology observed in the patients.

Sirtuin family in autoimmune diseases

In recent years, epigenetic modifications have been widely researched. As humans age, environmental and genetic factors may drive inflammation and immune responses by influencing the epigenome, which can lead to abnormal autoimmune responses in the body. Currently, an increasing number of studies have emphasized the important role of epigenetic modification in the progression of autoimmune diseases. Sirtuins (SIRTs) are class III nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases and SIRT-mediated deacetylation is an important epigenetic alteration. The SIRT family comprises seven protein members (namely, SIRT1-7). While the catalytic core domain contains amino acid residues that have remained stable throughout the entire evolutionary process, the N- and C-terminal regions are structurally divergent and contribute to differences in subcellular localization, enzymatic activity and substrate specificity. SIRT1 and SIRT2 are localized in the nucleus and cytoplasm. SIRT3, SIRT4, and SIRT5 are mitochondrial, and SIRT6 and SIRT7 are predominantly found in the nucleus. SIRTs are key regulators of various physiological processes such as cellular differentiation, apoptosis, metabolism, ageing, immune response, oxidative stress, and mitochondrial function. We discuss the association between SIRTs and common autoimmune diseases to facilitate the development of more effective therapeutic strategies.

NAD+ Metabolism and Immune Regulation: New Approaches to Inflammatory Bowel Disease Therapies

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is a multifactorial systemic inflammatory immune response. Nicotinamide adenine dinucleotide (NAD⁺) is a co-enzyme involved in cell signaling and energy metabolism. Calcium homeostasis, gene transcription, DNA repair, and cell communication involve NAD⁺ and its degradation products. There is a growing recognition of the intricate relationship between inflammatory diseases and NAD⁺ metabolism. In the case of IBD, the maintenance of intestinal homeostasis relies on a delicate balance between NAD⁺ biosynthesis and consumption. Consequently, therapeutics designed to target the NAD⁺ pathway are promising for the management of IBD. This review discusses the metabolic and immunoregulatory processes of NAD⁺ in IBD to examine the molecular biology and pathophysiology of the immune regulation of IBD and to provide evidence and theoretical support for the clinical use of NAD⁺ in IBD.

Case Report: A novel mutation in TNFAIP3 in a patient with type 1 diabetes mellitus and haploinsufficiency of A20

Background

Haploinsufficiency of A20 (HA20) is a monogenic autosomal-dominant genetic autoinflammatory disease caused by loss of function mutations in the TNFAIP3 gene. The predominant autoimmune phenotype associated with HA20 varies significantly, presenting with fever, recurrent oral and genital ulcers, skin rash, gastrointestinal and musculoskeletal symptoms, and other clinical manifestations, all of which indicate an early-onset of autoinflammatory disorder. Genetic linkage between TNFAIP3 and T1DM was reported in GWAS studies. However, only a few cases of HA20 combined with T1DM have been reported.

Case description

A 39-year-old man with a history of type 1 diabetes mellitus since 19 years was admitted to the Department of Endocrinology and Metabolism, First Affiliated Hospital of China Medical University. He also suffered from recurring and minor mouth ulcers since early childhood. His laboratory evaluation results revealed reduced islet function, normal lipid profile, HbA1c of 7%, elevated glutamate decarboxylase antibodies, elevated hepatic transaminases, and elevated thyroid-related antibodies with normal thyroid function. Notably, the patient was diagnosed in adolescence and never had ketoacidosis, the islets were functioning despite the long disease duration, his abnormal liver function could not be reasonably explained, and he had early onset Behcet's-like disease symptom. Hence, although he was on routine follow-up for diabetes, we communicated with him and obtained consent for genetic testing. Whole-exome sequencing revealed a novel c.1467_1468delinsAT heterozygous mutation in the gene TNFAIP3, which is located in exon 7, resulting in a stop-gained type mutation p.Q490*. With good but mild fluctuating glycemic control, the patient received intensive insulin therapy with long-acting and short-acting insulin. The liver function was improved by using ursodeoxycholic acid 0.75 mg/d during the follow-up.

Conclusion

We report a novel pathogenic mutation in TNFAIP3 that results in HA20 in a patient with T1DM. In addition, we analyzed the clinical feathers of such patients and summarized the cases of five patients with HA20 co-presented with T1DM. When T1DM co-occurs with autoimmune diseases or other clinical manifestations, such as oral and/or genital ulcers and chronic liver damage, the possibility of an HA20 must be considered. Early and definitive diagnosis of HA20 in such patients may inhibit the progression of late-onset autoimmune diseases, including T1DM.

Cellular and molecular biology of sirtuins in cardiovascular disease

Sirtuins (SIRTs) are a nicotinic adenine dinucleotide (+) -dependent histone deacetylase that regulates critical signaling pathways in prokaryotes and eukaryotes. Studies have identified seven mammalian homologs of the yeast SIRT silencing message regulator 2, namely, SIRT1-SIRT7. Recent in vivo and in vitro studies have successfully demonstrated the involvement of SIRTs in key pathways for cell biological function in physiological and pathological processes of the cardiovascular system, including processes including cellular senescence, oxidative stress, apoptosis, DNA damage, and cellular metabolism. Emerging evidence has stimulated a significant evolution in preventing and treating cardiovascular disease (CVD). Here, we review the important roles of SIRTs for the regulatory pathways involved in the pathogenesis of cardiovascular diseases and their molecular targets, including novel protein post-translational modifications of succinylation. In addition, we summarize the agonists and inhibitors currently identified to target novel specific small molecules of SIRTs. A better understanding of the role of SIRTs in the biology of CVD opens new avenues for therapeutic intervention with great potential for preventing and treating CVD.

β Cell and Autophagy: What Do We Know?

Pancreatic β cells are central to glycemic regulation through insulin production. Studies show autophagy as an essential process in β cell function and fate. Autophagy is a catabolic cellular process that regulates cell homeostasis by recycling surplus or damaged cell components. Impaired autophagy results in β cell loss of function and apoptosis and, as a result, diabetes initiation and progress. It has been shown that in response to endoplasmic reticulum stress, inflammation, and high metabolic demands, autophagy affects β cell function, insulin synthesis, and secretion. This review highlights recent evidence regarding how autophagy can affect β cells' fate in the pathogenesis of diabetes. Furthermore, we discuss the role of important intrinsic and extrinsic autophagy modulators, which can lead to β cell failure.

Novel Role of the SIRT1 in Endocrine and Metabolic Diseases

Silent information regulator 1 (SIRT1), a highly conserved NAD⁺-dependent deacetylase, is a cellular regulator that has received extensive attention in recent years and regarded as a sensor of cellular energy and metabolism. The accumulated evidence suggests that SIRT1 is involved in the development of endocrine and metabolic diseases. In a variety of organisms, SIRT1 regulates gene expression through the deacetylation of histone, transcription factors, and lysine residues of other modified proteins including several metabolic and endocrine signal transcription factors, thereby enhancing the therapeutic effects of endocrine and metabolic diseases. These evidences indicate that targeting SIRT1 has promising applications in the treatment of endocrine and metabolic diseases. This review focuses on the role of SIRT1 in endocrine and metabolic diseases. First, we describe the background and structure of SIRT1. Then, we outline the role of SIRT1 in endocrine and metabolic diseases such as hyperuricemia, diabetes, hypertension, hyperlipidemia, osteoporosis, and polycystic ovarian syndrome. Subsequently, the SIRT1 agonists and inhibitors in the above diseases are summarized and future research directions are proposed. Overall, the information presents here may highlight the potential of SIRT1 as a future biomarker and therapeutic target for endocrine and metabolic diseases.

Genetic Variants of SIRT1 Gene Promoter in Type 2 Diabetes

Type 2 diabetes (T2D) is a highly heterogeneous and polygenic disease. To date, genetic causes and underlying mechanisms for T2D remain unclear. SIRT1, one member of highly conserved NAD-dependent class III deacetylases, has been implicated in many human diseases. Accumulating evidence indicates that SIRT1 is involved in insulin resistance and impaired pancreatic β-cell function, the two hallmarks of T2D. Thus, we speculated that altered SIRT1 levels, resulting from the genetic variants within its regulatory region of SIRT1 gene, may contribute to the T2D development. In this study, the SIRT1 gene promoter was genetically analyzed in T2D patients (n = 218) and healthy controls (n = 358). A total of 20 genetic variants, including 7 single-nucleotide polymorphisms (SNPs), were identified. Five heterozygous genetic variants (g.4114-15InsA, g.4801G > A, g.4816G > C, g.4934G > T, and g.4963_64Ins17bp) and one SNP (g.4198A > C (rs35706870)) were identified in T2D patients, but in none of the controls. The frequencies of two SNPs (g.4540A > G (rs3740051) (OR: 1.75, 95% CI: 1.24-2.47, P < 0.001 in dominant genetic model) and g.4821G > T (rs35995735)) (OR: 3.58, 95% CI: 1.94-6.60, P < 0.001 in dominant genetic model) were significantly higher in T2D patients. Further association and haplotype analyses confirmed that these two SNPs were strongly linked, contributing to the T2D (OR: 1.442, 95% CI: 1.080-1.927, P < 0.05). Moreover, most of the genetic variants identified in T2D were disease-specific. Taken together, the genetic variants within SIRT1 gene promoter might contribute to the T2D development by altering SIRT1 levels. Underlying molecular mechanism needs to be further explored.

Insights on attenuating autophagy cellular and molecular pathways versus methotrexate-induced toxicity via liposomal turmeric therapy

Background

Methotrexate (MX), a competitive inhibitor of dihydrofolate reductase, can inhibit DNA and RNA production and is a powerful anticancer agent widely utilized in clinical practice for treating nonneoplastic maladies, as psoriasis and rheumatoid arthritis; meanwhile, its probable prescription dose and interval of administration are strictly limited due to dose-related organ damage. Former studies verified that kidney, brain, liver, and lung harms are prospective obstacles of methotrexate administration. To understand the machinery of methotrexate-prompt toxicity, various mechanisms were investigated. The former is an autophagy defense mechanism; autophagy is a self-digesting mechanism responsible for the removal of damaged organelles and malformed proteins by lysosome. The contemporary article hypothesized that turmeric or its liposomal analog could defeat autophagy of MX-induced acute toxicity. Methotrexate, in a dose of 1.5 mg/kg, was administered intravenously followed by turmeric and liposomal turmeric treatment in a dose of 5 mg/kg for 30 days in rats.

Results

Increment in autophagy (AUTP) consent by MX administration was attenuated by concurrent treatment via turmeric and liposomal turmeric that was reliable on the alteration in apoptotic markers. The assembly of FOXO-3 in serum post methotrexate administration was suppressed by concurrent treatment via liposomal turmeric. Apoptosis/autophagic marker investigation was evaluated through the gene expression of Bax (BCL2-associated X protein)/Bcl2 (B-cell lymphoma 2)/P53 (tumor protein P53)/SiRT-1 (sirtuin silent mating-type information regulation 2 homolog 1) and FOXO-3 (forkhead box transcription factor-3)/ERDJ-4 (endoplasmic reticulum localized DnaJ homologs)/BNP (brain natriuretic peptide B) signaling. The cell death of all cells was categorized to achieve autophagy. Interestingly, Bax/Bcl2/P53/SiRT-1 signaling pathways were downregulated, contributing to inhibiting the initiation of autophagy. Meanwhile, FOXO-3/BNP/ERDJ-4 reduction-implicated noncanonical autophagy pathways were involved in methotrexate-induced autophagy, whereas this change was suppressed when turmeric was administered in liposomal form.

Conclusion

These outcomes recommended that liposomal turmeric prevents MX-induced acute toxicity through its autophagy, antioxidant, and antiapoptotic properties.

Polygenic autoimmune disease risk alleles impacting B cell tolerance act in concert across shared molecular networks in mouse and in humans

Most B cells produced in the bone marrow have some level of autoreactivity. Despite efforts of central tolerance to eliminate these cells, many escape to periphery, where in healthy individuals, they are rendered functionally non-responsive to restimulation through their antigen receptor via a process termed anergy. Broad repertoire autoreactivity may reflect the chances of generating autoreactivity by stochastic use of germline immunoglobulin gene segments or active mechanisms may select autoreactive cells during egress to the naïve peripheral B cell pool. Likewise, it is unclear why in some individuals autoreactive B cell clones become activated and drive pathophysiologic changes in autoimmune diseases. Both of these remain central questions in the study of the immune system(s). In most individuals, autoimmune diseases arise from complex interplay of genetic risk factors and environmental influences. Advances in genome sequencing and increased statistical power from large autoimmune disease cohorts has led to identification of more than 200 autoimmune disease risk loci. It has been observed that autoantibodies are detectable in the serum years to decades prior to the diagnosis of autoimmune disease. Thus, current models hold that genetic defects in the pathways that control autoreactive B cell tolerance set genetic liability thresholds across multiple autoimmune diseases. Despite the fact these seminal concepts were developed in animal (especially murine) models of autoimmune disease, some perceive a disconnect between human risk alleles and those identified in murine models of autoimmune disease. Here, we synthesize the current state of the art in our understanding of human risk alleles in two prototypical autoimmune diseases - systemic lupus erythematosus (SLE) and type 1 diabetes (T1D) along with spontaneous murine disease models. We compare these risk networks to those reported in murine models of these diseases, focusing on pathways relevant to anergy and central tolerance. We highlight some differences between murine and human environmental and genetic factors that may impact autoimmune disease development and expression and may, in turn, explain some of this discrepancy. Finally, we show that there is substantial overlap between the molecular networks that define these disease states across species. Our synthesis and analysis of the current state of the field are consistent with the idea that the same molecular networks are perturbed in murine and human autoimmune disease. Based on these analyses, we anticipate that murine autoimmune disease models will continue to yield novel insights into how best to diagnose, prognose, prevent and treat human autoimmune diseases.

Pharmacological Approaches to Decelerate Aging: A Promising Path

Biological aging or senescence is a course in which cellular function decreases over a period of time and is a consequence of altered signaling mechanisms that are triggered in stressed cells leading to cell damage. Aging is among the principal risk factors for many chronic illnesses such as cancer, cardiovascular disorders, and neurodegenerative diseases. Taking this into account, targeting fundamental aging mechanisms therapeutically may effectively impact numerous chronic illnesses. Selecting ideal therapeutic options in order to hinder the process of aging and decelerate the progression of age-related diseases is valuable. Along therapeutic options, life style modifications may well render the process of aging. The process of aging is affected by alteration in many cellular and signaling pathways amid which mTOR, SIRT1, and AMPK pathways are the most emphasized. Herein, we have discussed the mechanisms of aging focusing mainly on the mentioned pathways as well as the role of inflammation and autophagy in aging. Moreover, drugs and natural products with antiaging properties are discussed in detail.

A natural genetic variation screen identifies insulin signaling, neuronal communication, and innate immunity as modifiers of hyperglycemia in the absence of Sirt1

Variation in the onset, progression, and severity of symptoms associated with metabolic disorders such as diabetes impairs the diagnosis and treatment of at-risk patients. Diabetes symptoms, and patient variation in these symptoms, are attributed to a combination of genetic and environmental factors, but identifying the genes and pathways that modify diabetes in humans has proven difficult. A greater understanding of genetic modifiers and the ways in which they interact with metabolic pathways could improve the ability to predict a patient's risk for severe symptoms, as well as enhance the development of individualized therapeutic approaches. In this study, we use the Drosophila Genetic Reference Panel to identify genetic variation influencing hyperglycemia associated with loss of Sirt1 function. Through analysis of individual candidate functions, physical interaction networks, and gene set enrichment analysis, we identify not only modifiers involved in canonical glucose metabolism and insulin signaling, but also genes important for neuronal signaling and the innate immune response. Furthermore, reducing the expression of several of these candidates suppressed hyperglycemia, making them potential candidate therapeutic targets. These analyses showcase the diverse processes contributing to glucose homeostasis and open up several avenues of future investigation.

Activation of SIRT-1 Signalling in the Prevention of Bipolar Disorder and Related Neurocomplications: Target Activators and Influences on Neurological Dysfunctions

SIRT-1 (silent mating-type information regulation 2 homolog-1) is a protein found in neuronal nuclei, microglia, and astrocyte cells of the brain. It is sometimes referred to as NAD + -dependent deacetylase (nicotinamide adenine dinucleotide). The activation of sirtuins (SIRT-1-7) has been shown to protect against a wide range of disorders, including neurodegenerative and neuropsychiatric disorders. SIRT-1 has gained considerable interest from these families because of its early link to long-life expansion and calorie restriction involvement. SIRT-1 is necessary for gene silencing, cell cycle regulation, fat and glucose metabolism, oxidative stress, ageing, and memory formation. In this review, we investigate the role of SIRT-1 downregulation in the progression of bipolar disorder (BD) and neurological abnormalities, as well as related neurological alterations such as genetic dysfunction, neurotransmitter imbalance, oxidative stress-induced apoptosis, and mitochondrial dysfunction. BD is a psychiatric disease distinguished by extreme mood fluctuations that range from depressive lows to manic highs. BD is a complicated disorder with numerous clinical signs and neurocomplications that produce significant behavioural problems. SIRT-1 deficiency in the brain has been demonstrated to affect the activity of its transcription factors and molecular changes, including genetic defects. SIRT-1 is now being studied as a potential therapeutic target for a range of brain disorders. A recent study also found that activating SIRT-1 signalling performs a protective effect in avoiding depression and mania-like behaviours. Furthermore, this review investigates the potential mechanisms by which SIRT-1 regulates neuronal transmission and neurogenesis. As a result of our review, we revealed that SIRT-1 activators have neuroprotective potential in BD and related neurological dysfunctions.

N-terminal BET bromodomain inhibitors disrupt a BRD4-p65 interaction and reduce inducible nitric oxide synthase transcription in pancreatic β-cells

Chronic inflammation of pancreatic islets is a key driver of β-cell damage that can lead to autoreactivity and the eventual onset of autoimmune diabetes (T1D). In the islet, elevated levels of proinflammatory cytokines induce the transcription of the inducible nitric oxide synthase (iNOS) gene, NOS2, ultimately resulting in increased nitric oxide (NO). Excessive or prolonged exposure to NO causes β-cell dysfunction and failure associated with defects in mitochondrial respiration. Recent studies showed that inhibition of the bromodomain and extraterminal domain (BET) family of proteins, a druggable class of epigenetic reader proteins, prevents the onset and progression of T1D in the non-obese diabetic mouse model. We hypothesized that BET proteins co-activate transcription of cytokine-induced inflammatory gene targets in β-cells and that selective, chemotherapeutic inhibition of BET bromodomains could reduce such transcription. Here, we investigated the ability of BET bromodomain small molecule inhibitors to reduce the β-cell response to the proinflammatory cytokine interleukin 1 beta (IL-1β). BET bromodomain inhibition attenuated IL-1β-induced transcription of the inflammatory mediator NOS2 and consequent iNOS protein and NO production. Reduced NOS2 transcription is consistent with inhibition of NF-κB facilitated by disrupting the interaction of a single BET family member, BRD4, with the NF-κB subunit, p65. Using recently reported selective inhibitors of the first and second BET bromodomains, inhibition of only the first bromodomain was necessary to reduce the interaction of BRD4 with p65 in β-cells. Moreover, inhibition of the first bromodomain was sufficient to mitigate IL-1β-driven decreases in mitochondrial oxygen consumption rates and β-cell viability. By identifying a role for the interaction between BRD4 and p65 in controlling the response of β-cells to proinflammatory cytokines, we provide mechanistic information on how BET bromodomain inhibition can decrease inflammation. These studies also support the potential therapeutic application of more selective BET bromodomain inhibitors in attenuating β-cell inflammation.

The anti-diabetic effects of betanin in streptozotocin-induced diabetic rats through modulating AMPK/SIRT1/NF-κB signaling pathway

Background

In the last few years, the effects of bioactive food components have received much attention because of their beneficial effects including decreasing inflammation, scavenging free radicals, and regulating cell signaling pathways. Betanin as a potent antioxidant has been previously reported to exhibit anti diabetic effects. The present study aimed to evaluate the effects of betanin on glycemic control, lipid profile, hepatic function tests, as well as the gene expression levels of 5′ adenosine monophosphate‑activated protein kinase (AMPK), sirtuin-1 (SIRT1), and nuclear factor kappa B (NF‑κB) in streptozocin (STZ) induced diabetic rats.

Methods

Diabetes was induced in male Sprague–Dawley rats by intraperitoneal administration of STZ. Different doses of betanin (10, 20 and 40 mg/kg.b.w) was administered to diabetic rats for 28 days. Fasting blood glucose and serum insulin were measured. The histopathology of liver and pancreas tissue evaluated. Real-time PCR was performed to assess gene expression levels.

Results

Treatment of diabetic rats with betanin (10 and 20 mg/kg.b.w) reduced FBG levels compared to the control diabetic rats (P < 0.001). Betanin at the dose of 20 mg/kg.b.w was most effective in increasing serum insulin levels (P < 0.001) improving glucose tolerance test (GTT) as well as improvement in lipid profile and liver enzymes levels. According to histopathologic assay, different damages induced by STZ to liver and pancreas tissues was largely eliminated by treatment with 10 and 20 mg/kg.b.w of betanin. Betanin also significantly upregulated the AMPK and SIRT1 and downregulated the NF-κB mRNA expression compared to the diabetic control rats (P < 0.05).

Conclusion

Betanin could modulate AMPK/SIRT1/NF-κB signaling pathway and this may be one of its anti-diabetic molecular mechanisms.

Molecular and Pathophysiological Links between Metabolic Disorders and Inflammatory Bowel Diseases

Despite considerable epidemiological evidence indicating comorbidity between metabolic disorders, such as obesity, type 2 diabetes, and non-alcoholic fatty liver disease, and inflammatory bowel diseases (IBD), such as Crohn’s disease and ulcerative colitis, as well as common pathophysiological features shared by these two categories of diseases, the relationship between their pathogenesis at molecular levels are not well described. Intestinal barrier dysfunction is a characteristic pathological feature of IBD, which also plays causal roles in the pathogenesis of chronic inflammatory metabolic disorders. Increased intestinal permeability is associated with a pro-inflammatory response of the intestinal immune system, possibly leading to the development of both diseases. In addition, dysregulated interactions between the gut microbiota and the host immunity have been found to contribute to immune-mediated disorders including the two diseases. In connection with disrupted gut microbial composition, alterations in gut microbiota-derived metabolites have also been shown to be closely related to the pathogeneses of both diseases. Focusing on these prominent pathophysiological features observed in both metabolic disorders and IBD, this review highlights and summarizes the molecular risk factors that may link between the pathogeneses of the two diseases, which is aimed at providing a comprehensive understanding of molecular mechanisms underlying their comorbidity.

SIRT1 single-nucleotide polymorphisms are associated with corticosteroid sensitivity in primary immune thrombocytopenia patients

BACKGROUND

Primary immune thrombocytopenia (ITP) is an autoimmune disorder characterized by decreased platelet count. While corticosteroids are a useful first-line therapy for ITP patients, their long-term effectiveness is limited, and the determinants of corticosteroid sensitivity in ITP patients remain largely unknown. Sirtuin 1 (SIRT1), a member of the mammalian sirtuin family, is related to the anti-inflammatory effects of corticosteroids. Here, we investigate the contribution of the SIRT1 single-nucleotide polymorphisms (SNPs) rs12778366 and rs4746720 to ITP susceptibility.

METHODS

We recruited 330 ITP patients and 309 healthy controls from Han population, and performed genotyping of SIRT1 rs12778366 and rs4746720 using a MassARRAY system. The results were validated in another 55 ITP patients from ethnic minorities.

RESULTS

Using clinical data of patients and controls from Han polulation, including corticosteroid sensitivity, susceptibility, refractoriness, and severity, our results revealed that the CC/TC genotypes of SIRT1 rs12778366 were associated with a 2.034-fold increased risk of corticosteroid resistance compared to the homozygous major TT genotype (dominant, CC/TC vs. TT, OR = 2.034, 95% CI = 1.039-3.984, p = 0.038). In contrast, the CC/CT genotype of SIRT1 rs4746720 showed a 0.560-fold decreased risk of corticosteroid resistance (dominant, 95% CI = 0.321-0.976, OR = 0.560, p = 0.041). The C allele substitute in SIRT1 rs12778366 was significantly associated with the corticosteroid sensitivity of ITP patients (p = 0.021). The similar results were obtained in minority ITP patients.

CONCLUSION

This study indicates that SIRT1 rs12778366 and rs4746720 may be genetic factors related to corticosteroid sensitivity in ITP patients.

Quercetin and metabolic syndrome: A review

Metabolic syndrome (MetS) is a complex of diseases that lead to mortality due to the development of cardiovascular problems. Quercetin, as an important flavonoid, has various properties such as decreasing blood pressure, anti-hyperlipidemia, anti-hyperglycemia, anti-oxidant, antiviral, anticancer, anti-inflammatory, anti-microbial, neuroprotective, and cardio-protective effects. In this review article, we collected original articles from different sources such as Google Scholar, Medline, Scopus, and Pubmed, which is related to the effect of quercetin on the improvement of the signs of MetS, including elevated glucose level, hyperlipidemia, obesity, and blood pressure. According to these data, quercetin may also have a role in the management of metabolic disorders via different mechanisms such as increasing adiponectin, decreasing leptin, anti-oxidant activity, reduction of insulin resistance, the elevation of insulin level, and blocking of calcium channel. We have attempted to make some recommendations on the quercetin application in patients. However, it needs to do further clinical trials and more investigations to show the real clinical value of quercetin on metabolic syndrome.

Epigenetic Remodeling in Obesity-Related Vascular Disease

Significance: The prevalence of obesity and cardiometabolic phenotypes is alarmingly increasing across the globe and is associated with atherosclerotic vascular complications and high mortality. In spite of multifactorial interventions, vascular residual risk remains high in this patient population, suggesting the need for breakthrough therapies. The mechanisms underpinning obesity-related vascular disease remain elusive and represent an intense area of investigation. Recent Advances: Epigenetic modifications-defined as environmentally induced chemical changes of DNA and histones that do not affect DNA sequence-are emerging as a potent modulator of gene transcription in the vasculature and might significantly contribute to the development of obesity-induced endothelial dysfunction. DNA methylation and histone post-translational modifications cooperate to build complex epigenetic signals, altering transcriptional networks that are implicated in redox homeostasis, mitochondrial function, vascular inflammation, and perivascular fat homeostasis in patients with cardiometabolic disturbances. Critical Issues: Deciphering the epigenetic landscape in the vasculature is extremely challenging due to the complexity of epigenetic signals and their function in regulating transcription. An overview of the most important epigenetic pathways is required to identify potential molecular targets to treat or prevent obesity-related endothelial dysfunction and atherosclerotic disease. This would enable the employment of precision medicine approaches in this setting. Future Directions: Current and future research efforts in this field entail a better definition of the vascular epigenome in obese patients as well as the unveiling of novel, cell-specific chromatin-modifying drugs that are able to erase specific epigenetic signals that are responsible for maladaptive transcriptional alterations and vascular dysfunction in obese patients. Antioxid. Redox Signal. 34, 1165-1199.

The Versatility of Sirtuin-1 in Endocrinology and Immunology

Sirtuins belong to the class III family of NAD-dependent histone deacetylases (HDAC) and are involved in diverse physiological processes that range from regulation of metabolism and endocrine function to coordination of immunity and cellular responses to stress. Sirtuin-1 (SIRT1) is the most well-studied family member and has been shown to be critically involved in epigenetics, immunology, and endocrinology. The versatile roles of SIRT1 include regulation of energy sensing metabolic homeostasis, deacetylation of histone and non-histone proteins in numerous tissues, neuro-endocrine regulation via stimulation of hypothalamus-pituitary axes, synthesis and maintenance of reproductive hormones via steroidogenesis, maintenance of innate and adaptive immune system via regulation of T- and B-cell maturation, chronic inflammation and autoimmune diseases. Moreover, SIRT1 is an appealing target in various disease contexts due to the promise of pharmacological and/or natural modulators of SIRT1 activity within the context of endocrine and immune-related disease models. In this review we aim to provide a broad overview on the role of SIRT1 particularly within the context of endocrinology and immunology.

Understanding Dietary Intervention-Mediated Epigenetic Modifications in Metabolic Diseases

The global prevalence of metabolic disorders, such as obesity, diabetes and fatty liver disease, is dramatically increasing. Both genetic and environmental factors are well-known contributors to the development of these diseases and therefore, the study of epigenetics can provide additional mechanistic insight. Dietary interventions, including caloric restriction, intermittent fasting or time-restricted feeding, have shown promising improvements in patients' overall metabolic profiles (i.e., reduced body weight, improved glucose homeostasis), and an increasing number of studies have associated these beneficial effects with epigenetic alterations. In this article, we review epigenetic changes involved in both metabolic diseases and dietary interventions in primary metabolic tissues (i.e., adipose, liver, and pancreas) in hopes of elucidating potential biomarkers and therapeutic targets for disease prevention and treatment.

SIRT1 Activation by Natural Phytochemicals: An Overview

Sirtuins are class III histone deacetylases, whose enzymatic activity is dependent on NAD⁺ as a cofactor. Sirtuins are reported to modulate numerous activities by controlling gene expression, DNA repair, metabolism, oxidative stress response, mitochondrial function, and biogenesis. Deregulation of their expression and/or action may lead to tissue-specific degenerative events involved in the development of several human pathologies, including cancer, neurodegeneration, and cardiovascular disease. The most studied member of this class of enzymes is sirtuin 1 (SIRT1), whose expression is associated with increasing insulin sensitivity. SIRT1 has been implicated in both tumorigenic and anticancer processes, and is reported to regulate essential metabolic pathways, suggesting that its activation might be beneficial against disorders of the metabolism. Via regulation of p53 deacetylation and modulation of autophagy, SIRT1 is implicated in cellular response to caloric restriction and lifespan extension. In recent years, scientific interest focusing on the identification of SIRT1 modulators has led to the discovery of novel small molecules targeting SIRT1 activity. This review will examine compounds of natural origin recently found to upregulate SIRT1 activity, such as polyphenolic products in fruits, vegetables, and plants including resveratrol, fisetin, quercetin, and curcumin. We will also discuss the potential therapeutic effects of these natural compounds in the prevention and treatment of human disorders, with particular emphasis on their metabolic impact.

Overexpression of Sirtuin 1 protein in neurons prevents and reverses experimental diabetic neuropathy

In diabetic neuropathy, there is activation of axonal and sensory neuronal degeneration pathways leading to distal axonopathy. The nicotinamide-adenine dinucleotide (NAD+)-dependent deacetylase enzyme, Sirtuin 1 (SIRT1), can prevent activation of these pathways and promote axonal regeneration. In this study, we tested whether increased expression of SIRT1 protein in sensory neurons prevents and reverses experimental diabetic neuropathy induced by a high fat diet (HFD). We generated a transgenic mouse that is inducible and overexpresses SIRT1 protein in neurons (nSIRT1OE Tg). Higher levels of SIRT1 protein were localized to cortical and hippocampal neuronal nuclei in the brain and in nuclei and cytoplasm of small to medium sized neurons in dorsal root ganglia. Wild-type and nSIRT1OE Tg mice were fed with either control diet (6.2% fat) or a HFD (36% fat) for 2 months. HFD-fed wild-type mice developed neuropathy as determined by abnormal motor and sensory nerve conduction velocity, mechanical allodynia, and loss of intraepidermal nerve fibres. In contrast, nSIRT1OE prevented a HFD-induced neuropathy despite the animals remaining hyperglycaemic. To test if nSIRT1OE would reverse HFD-induced neuropathy, nSIRT1OE was activated after mice developed peripheral neuropathy on a HFD. Two months after nSIRT1OE, we observed reversal of neuropathy and an increase in intraepidermal nerve fibre. Cultured adult dorsal root ganglion neurons from nSIRT1OE mice, maintained at high (30 mM) total glucose, showed higher basal and maximal respiratory capacity when compared to adult dorsal root ganglion neurons from wild-type mice. In dorsal root ganglion protein extracts from nSIRT1OE mice, the NAD+-consuming enzyme PARP1 was deactivated and the major deacetylated protein was identified to be an E3 protein ligase, NEDD4-1, a protein required for axonal growth, regeneration and proteostasis in neurodegenerative diseases. Our results indicate that nSIRT1OE prevents and reverses neuropathy. Increased mitochondrial respiratory capacity and NEDD4 activation was associated with increased axonal growth driven by neuronal overexpression of SIRT1. Therapies that regulate NAD+ and thereby target sirtuins may be beneficial in human diabetic sensory polyneuropathy.

Sirtuins and NAD+ in the Development and Treatment of Metabolic and Cardiovascular Diseases

The sirtuin family of nicotinamide adenine dinucleotide-dependent deacylases (SIRT1-7) are thought to be responsible, in large part, for the cardiometabolic benefits of lean diets and exercise and when upregulated can delay key aspects of aging. SIRT1, for example, protects against a decline in vascular endothelial function, metabolic syndrome, ischemia-reperfusion injury, obesity, and cardiomyopathy, and SIRT3 is protective against dyslipidemia and ischemia-reperfusion injury. With increasing age, however, nicotinamide adenine dinucleotide levels and sirtuin activity steadily decrease, and the decline is further exacerbated by obesity and sedentary lifestyles. Activation of sirtuins or nicotinamide adenine dinucleotide repletion induces angiogenesis, insulin sensitivity, and other health benefits in a wide range of age-related cardiovascular and metabolic disease models. Human clinical trials testing agents that activate SIRT1 or boost nicotinamide adenine dinucleotide levels are in progress and show promise in their ability to improve the health of cardiovascular and metabolic disease patients.

GABAergic regulation of pancreatic islet cells: Physiology and antidiabetic effects

Diabetes occurs when pancreatic β-cell death exceeds β-cell growth, which leads to loss of β-cell mass. An effective therapy must have two actions: promotion of β-cell replication and suppression of β-cell death. Previous studies have established an important role for γ-aminobutyric acid (GABA) in islet-cell hormone homeostasis, as well as the maintenance of the β-cell mass. GABA exerts paracrine actions on α cells in suppressing glucagon secretion, and it has autocrine actions on β cells that increase insulin secretion. Multiple studies have shown that GABA increases the mitotic rate of β cells. In mice, following β-cell depletion with streptozotocin, GABA therapy can restore the β-cell mass. Enhanced β-cell replication appears to depend on growth and survival pathways involving Akt activation. Some studies have also suggested that it induces transdifferentiation of α cells into β cells, but this has been disputed and requires further investigation. In addition to proliferative effects, GABA protects β cells against injury and markedly reduces their apoptosis under a variety of conditions. The antiapoptotic effects depend at least in part on the enhancement of sirtuin-1 and Klotho activity, which both inhibit activation of the NF-κB inflammatory pathway. Importantly, in xenotransplanted human islets, GABA therapy stimulates β-cell replication and insulin secretion. Thus, the intraislet GABAergic system is a target for the amelioration of diabetes therapy, including β-cell survival and regeneration. GABA (or GABAergic drugs) can be combined with other antidiabetic drugs for greater effect.

KLF11 variant in a family clinically diagnosed with early childhood-onset type 1B diabetes

KLF11 is the causative gene for maturity-onset diabetes of the young 7 (MODY7). KLF11 regulates insulin gene expression through binding to the GC box in the promoter. To date, only two KLF11 mutations have been identified in three families with early-onset type 2 diabetes. Here, we report a novel KLF11 variant associated with early childhood-onset type 1B diabetes. The proband and his younger sister exhibited hyperglycemia at age 1 year, and their mother developed diabetes at age 4 years. These three individuals required insulin injection from the initial phase of the disease. Being negative for islet cell autoantibodies, they were diagnosed with type 1B diabetes. Mutation screening for 30 diabetes-associated genes identified a heterozygous KLF11 variant (p.His418Gln) in the proband and his sister. The variant was also detected in the affected mother, as well as in the allegedly unaffected maternal grandmother. In silico analyses indicated that this variant involves a highly conserved histidine residue in the first C₂ H₂ zinc finger domain which ligates a zinc ion. In vitro analyses showed that expression levels and intracellular localization of His418Gln-KLF11 were comparable to those of wildtype (WT)-KLF11. Luciferase assays demonstrated that while WT-KLF11 suppressed the activity of a 6 × GC box-containing reporter, His418Gln-KLF11 lacked the suppressive effect. Notably, His418Gln-KLF11 canceled the suppressive effect of co-transfected WT-KLF11. Such a dominant-negative effect was absent in the previously reported Ala347Ser-KLF11 variant. These results indicate that specific variants of KLF11 (MODY7) with a dominant-negative effect underlie early childhood-onset type 1B diabetes with incomplete penetrance. This study documents a novel monogenic mutation associated with diabetes in children.

Combined effect of GABA and glucagon-like peptide-1 receptor agonist on cytokine-induced apoptosis in pancreatic β-cell line and isolated human islets

BACKGROUND

Treatment with GABA or glucagon-like peptide-1 (GLP-1) can preserve pancreatic β-cell mass and prevent diabetes. Recently, we reported that the combination of GABA and sitagliptin (a dipeptidyl peptidase-4 inhibitor that increases endogenous GLP-1) was more effective than either agent alone in reducing drug-induced β-cell damage and promoting β-cell regeneration in mice. However, in human islets, it remains unclear whether GABA and GLP-1 exert similar effects.

METHODS

To investigate GABA and GLP-1 interactions, human islets or INS-1 cells were treated with GABA and/or exendin-4, a GLP-1 receptor agonist (GLP-1RA) in clinical use, and incubated with a cytokine mixture for 24 hours. Cleaved caspase-3 and annexin V binding were measured by western blot and flow cytometry analysis, respectively, to investigate effects on cytokine-induced apoptosis.

RESULTS

Cytokine-induced apoptosis was reduced by either GABA or exendin-4 alone. This was markedly improved by combining GABA and exendin-4, resulting in a reversal of apoptosis. The combination notably increased Akt pathway signaling. Furthermore, sirtuin-1 (SIRT1) and α-Klotho, both reported to have protective effects on β-cells, were increased. Importantly, the combination ameliorated insulin secretion by human β-cells.

CONCLUSIONS

The combination of GABA and a GLP-1RA exerted additive effects on β-cell survival and function, suggesting that this combination may be superior to either drug alone in the treatment of diabetes.

Mitophagy and Oxidative Stress in Cancer and Aging: Focus on Sirtuins and Nanomaterials

Mitochondria are the cellular center of energy production and of several important metabolic processes. Mitochondrion health is maintained with a substantial intervention of mitophagy, a process of macroautophagy that degrades selectively dysfunctional and irreversibly damaged organelles. Because of its crucial duty, alteration in mitophagy can cause functional and structural adjustment in the mitochondria, changes in energy production, loss of cellular adaptation, and cell death. In this review, we discuss the dual role that mitophagy plays in cancer and age-related pathologies, as a consequence of oxidative stress, evidencing the triggering stimuli and mechanisms and suggesting the molecular targets for its therapeutic control. Finally, a section has been dedicated to the interplay between mitophagy and therapies using nanoparticles that are the new frontier for a direct and less invasive strategy.

The expression of sirtuins, superoxide dismutase, and lipid peroxidation status in peripheral blood from patients with diabetes and hypothyroidism

BACKGROUND

Sirtuin 1 (SIRT1) and sirtuin 3 (SIRT3) proteins have an important role in counteracting oxidative stress. Although diabetes and hypothyroidism (HT) are both characterized by oxidative stress, the mechanisms are not fully understood. This study investigated the effects of type 1 diabetes (T1D), type 2 diabetes (T2D), and HT on the expression levels of SIRT1, SIRT3, and manganese superoxide dismutase (SOD2).

METHODS

Gene expression of SIRT1, SIRT3, and SOD2 was measured using real-time PCR. The protein expression of SOD2 and lipid peroxidation (thiobarbituric acid reactive substances) was measured by the TBARS Assay kit and enzyme-linked immunosorbent assay (ELISA) respectively.

RESULTS

The results showed that the SIRT1 and SIRT3 levels were lower in peripheral blood samples from patients with T1D, T2D, or HT than in healthy individuals. Interestingly, the mRNA and protein expression levels of SOD2 were higher in all three patient groups. Lipid peroxidation was higher in the patients with HT than in the healthy individuals.

CONCLUSIONS

These results indicate alterations in the expression levels of sirtuins and superoxide dismutase in diabetes and HT, which may be related, at least in part, to the oxidative stress. Identifying such alterations in those patients will pave the way towards the development of drugs to enhance SIRT1 and SIRT3 expression and their activity to prevent the damaging effect of oxidative stress.

SIRT1 activation attenuates α cell hyperplasia, hyperglucagonaemia and hyperglycaemia in STZ-diabetic mice

The NAD⁺-dependent lysine deacetylase, Sirtuin 1 (SIRT1), plays a central role in metabolic regulation. With type 1 diabetes a disease that is characterised by metabolic dysregulation, we sought to assess the impact of SIRT1 activation in experimental, streptozotocin (STZ)-induced diabetes. CD1 mice with and without STZ-induced diabetes were randomized to receive the SIRT1 activating compound, SRT3025, or vehicle over 20 weeks. Vehicle treated STZ-CD1 mice developed severe hyperglycaemia with near-absent circulating insulin and widespread beta cell loss in association with hyperglucagonaemia and expanded islet alpha cell mass. Without affecting ß-cell mass or circulating insulin, diabetic mice that received SRT3025 had substantially improved glycaemic control with greatly reduced islet α cell mass and lower plasma glucagon concentrations. Consistent with reduced glucagon abundance, the diabetes-associated overexpression of key gluconeogenic enzymes, glucose-6-phosphatase and PEPCK were also lowered by SRT3025. Incubating cultured α cells with SRT3025 diminished their glucagon secretion and proliferative activity in association with a reduction in the α cell associated transcription factor, Aristaless Related Homeobox (Arx). By reducing the paradoxical increase in glucagon, SIRT1 activation may offer a new, α-cell centric approach to the treatment of type 1 diabetes.

β-Cell Autophagy in Diabetes Pathogenesis

Nearly 100 years have passed since Frederick Banting and Charles Best first discovered and purified insulin. Their discovery and subsequent improvements revolutionized the treatment of diabetes, and the field continues to move at an ever-faster pace with respect to unique treatments for both type 1 and type 2 diabetes. Despite these advances, we still do not fully understand how apoptosis of the insulin-producing β-cells is triggered, presenting a challenge in the development of preventative measures. In recent years, the process of autophagy has generated substantial interest in this realm due to discoveries highlighting its clear role in the maintenance of cellular homeostasis. As a result, the number of studies focused on islet and β-cell autophagy has increased substantially in recent years. In this review, we will discuss what is currently known regarding the role of β-cell autophagy in type 1 and type 2 diabetes pathogenesis, with an emphasis on new and exciting developments over the past 5 years. Further, we will discuss how these discoveries might be translated into unique treatments in the coming years.

Comprehensive screening for monogenic diabetes in 89 Japanese children with insulin-requiring antibody-negative type 1 diabetes

BACKGROUND

Mutations in causative genes for neonatal diabetes or maturity-onset diabetes of the young have been identified in multiple patients with autoantibody-negative type 1 diabetes (T1D).

OBJECTIVES

We aimed to clarify the prevalence and phenotypic characteristics of monogenic abnormalities among 89 children with autoantibody-negative insulin-requiring T1D.

METHODS

Mutations in 30 genes were screened using next-generation sequencing, and copy-number alterations of 4 major causative genes were examined using multiplex-ligation-dependent probe amplification. We compared the clinical characteristics between mutation carriers and non-carriers.

RESULTS

We identified 11 probable pathogenic substitutions (6 in INS , 2 in HNF1A , 2 in HNF4A , and 1 in HNF1B ) in 11 cases, but no copy-number abnormalities. Only 2 mutation carriers had affected parents. De novo occurrence was confirmed for 3 mutations. The non-carrier group, but not the carrier group, was enriched with susceptible HLA alleles. Mutation carriers exhibited comparable phenotypes to those of non-carriers, except for a relatively normal body mass index (BMI) at diagnosis.

CONCLUSIONS

This study demonstrated significant genetic overlap between autoantibody-negative T1D and monogenic diabetes. Mutations in INS and HNF genes, but not those in GCK and other monogenic diabetes genes, likely play critical roles in children with insulin-requiring T1D. This study also suggests the relatively high de novo rates of INS and HNF mutations, and the etiological link between autoimmune abnormalities and T1D in the non-carrier group. Carriers of monogenic mutations show non-specific phenotypes among all T1D cases, although they are more likely to have a normal BMI at diagnosis than non-carriers.

Distinctive Roles of Sirtuins on Diabetes, Protective or Detrimental?

Dysregulation of metabolic pathways leads to type 2 diabetes, characteristic of high glucose concentration caused by insulin resistance. The histone deacetylases sirtuins exhibit remarkable enzymatic activities. Accumulating evidence indicates that sirtuins can be pharmacologically activated to ameliorate diabetes. Here, we evaluated different roles of sirtuins (SIRT1-SIRT7) in diabetes progression and described their involvement in metabolic pathways of skeletal muscle, adipose tissue and liver. The nuclear sirtuins, SIRT1, SIRT6, and SIRT7, regulate the activity of key transcription factors and cofactors in almost all tissues with the cellular responses to energy demands. The mitochondrial sirtuins, SIRT3, SIRT4, and SIRT5, regulate the activity of mitochondrial enzymes in response to fasting and calorie restriction. Moreover, genetic polymorphisms of SIRT1 and SIRT2 have been reported to associate with diabetes development. It's worth noting that SIRT1, SIRT2, SIRT3, and SIRT6 are positive regulators of insulin resistance in most cases. In the opposite, SIRT4 and SIRT7 inhibit insulin secretion and fatty acid oxidation. Identification of SIRT1 activators for diabetes has gained wide attention, such as metformin, resveratrol, and resveratrol derivatives. Randomized, prospective, and large-scale clinical trials are warrant to uncover the responsibilities of SIRTs modulators on diabetes progress.

Intestinal Epithelial Sirtuin 1 Regulates Intestinal Inflammation During Aging in Mice by Altering the Intestinal Microbiota

BACKGROUND & AIMS

Intestinal epithelial homeostasis is maintained by complex interactions among epithelial cells, commensal gut microorganisms, and immune cells. Disruption of this homeostasis is associated with disorders such as inflammatory bowel disease (IBD), but the mechanisms of this process are not clear. We investigated how Sirtuin 1 (SIRT1), a conserved mammalian NAD+-dependent protein deacetylase, senses environmental stress to alter intestinal integrity.

METHODS

We performed studies of mice with disruption of Sirt1 specifically in the intestinal epithelium (SIRT1 iKO, villin-Cre+, Sirt1flox/flox mice) and control mice (villin-Cre-, Sirt1flox/flox) on a C57BL/6 background. Acute colitis was induced in some mice by addition of 2.5% dextran sodium sulfate to drinking water for 5-9 consecutive days. Some mice were given antibiotics via their drinking water for 4 weeks to deplete their microbiota. Some mice were fed with a cholestyramine-containing diet for 7 days to sequester their bile acids. Feces were collected and proportions of microbiota were analyzed by 16S rRNA amplicon sequencing and quantitative PCR. Intestines were collected from mice and gene expression profiles were compared by microarray and quantitative PCR analyses. We compared levels of specific mRNAs between colon tissues from age-matched patients with ulcerative colitis (n=10) vs without IBD (n=8, controls).

RESULTS

Mice with intestinal deletion of SIRT1 (SIRT1 iKO) had abnormal activation of Paneth cells starting at the age of 5-8 months, with increased activation of NF-κB, stress pathways, and spontaneous inflammation at 22-24 months of age, compared with control mice. SIRT1 iKO mice also had altered fecal microbiota starting at 4-6 months of age compared with control mice, in part because of altered bile acid metabolism. Moreover, SIRT1 iKO mice with defective gut microbiota developed more severe colitis than control mice. Intestinal tissues from patients with ulcerative colitis expressed significantly lower levels of SIRT1 mRNA than controls. Intestinal tissues from SIRT1 iKO mice given antibiotics, however, did not have signs of inflammation at 22-24 months of age, and did not develop more severe colitis than control mice at 4-6 months.

CONCLUSIONS

In analyses of intestinal tissues, colitis induction, and gut microbiota in mice with intestinal epithelial disruption of SIRT1, we found this protein to prevent intestinal inflammation by regulating the gut microbiota. SIRT1 might therefore be an important mediator of host-microbiome interactions. Agents designed to activate SIRT1 might be developed as treatments for IBDs.

Resolution of inflammation in inflammatory bowel disease

Treatment of inflammatory bowel disease at present mainly targets mediators of inflammation to stop or suppress pro-inflammatory processes. Typical examples are steroids, suppression of T cells by thioguanine nucleotides, or antibodies against cytokines such as tumour necrosis factor, interleukin 12, or interleukin 23. In addition to suppression of inflammation, development of therapeutic strategies that support resolution of inflammation or that actively resolve inflammation might be desirable. Resolution of inflammation is now seen as an active process involving specific mediators (eg, lipid mediators or specific cytokines) that is mandatory to restore organ function and completely shut down inflammation. The molecular pathways involved in resolution of inflammation have been investigated in recent years and could be adopted in treatment strategies for inflammatory bowel disease. Among these approaches are anti-integrin strategies and means to produce or locally increase restitution or resolution factors, such as restoration of the activity of transforming growth factor-β by anti-SMAD7 antisense oligonucleotides. The potential role of inflammation-resolving lipid mediators (eg, resolvins), however, still warrants further study and clinical development. This Review focuses on the specific role of active resolution of inflammation in inflammatory bowel disease pathophysiology. Potential therapeutic targets based on these pathways are also discussed.

Oxidative Stress-Related Mechanisms and Antioxidant Therapy in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and is the leading cause of blindness in young adults. Oxidative stress has been implicated as a critical cause of DR. Metabolic abnormalities induced by high-glucose levels are involved in the development of DR and appear to be influenced by oxidative stress. The imbalance between reactive oxygen species (ROS) production and the antioxidant defense system activates several oxidative stress-related mechanisms that promote the pathogenesis of DR. The damage caused by oxidative stress persists for a considerable time, even after the blood glucose concentration has returned to a normal level. Animal experiments have proved that the use of antioxidants is a beneficial therapeutic strategy for the treatment of DR, but more data are required from clinical trials. The aims of this review are to highlight the improvements to our understanding of the oxidative stress-related mechanisms underlying the development of DR and provide a summary of the main antioxidant therapy strategies used to treat the disease.

Quercetin Improves Glucose and Lipid Metabolism of Diabetic Rats: Involvement of Akt Signaling and SIRT1

Glucose and lipid metabolism disorder in diabetes mellitus often causes damage to multiple tissues and organs. Diabetes mellitus is beneficially affected by quercetin. However, its concrete mechanisms are yet to be fully elucidated. In our study, diabetes was induced in Sprague-Dawley rats by STZ injection. The rats were randomly divided into normal control, diabetic model, low-dose quercetin treatment, high-dose quercetin treatment, and pioglitazone treatment groups. Fasting blood glucose was collected to evaluate diabetes. Immunohistochemistry and fluorometric assay were performed to explore SIRT1. Akt levels were measured through immunoprecipitation and Western blot. After 12 weeks of quercetin treatment, the biochemical parameters of glucose and lipid metabolism improved to varying degrees. Hepatic histomorphological injury was alleviated, and hepatic glycogen content was increased. The expression and activity of hepatic SIRT1 were enhanced, and Akt was activated by phosphorylation and deacetylation. These results suggested that the beneficial effects of quercetin on glucose and lipid metabolism disorder are probably associated with the upregulated activity and protein level of SIRT1 and its influence on Akt signaling pathway. Hence, quercetin shows potential for the treatment of glucose and lipid metabolism disorder in diabetes mellitus.

Elevations in the Fasting Serum Proinsulin-to-C-Peptide Ratio Precede the Onset of Type 1 Diabetes

OBJECTIVE

We tested whether an elevation in the serum proinsulin-to-C-peptide ratio (PI:C), a biomarker of β-cell endoplasmic reticulum (ER) dysfunction, was associated with progression to type 1 diabetes.

RESEARCH DESIGN AND METHODS

Fasting total PI and C levels were measured in banked serum samples obtained from TrialNet Pathway to Prevention (PTP) participants, a cohort of autoantibody-positive relatives without diabetes of individuals with type 1 diabetes. Samples were obtained ∼12 months before diabetes onset from PTP progressors in whom diabetes developed (n = 60), and were compared with age-, sex-, and BMI-matched nonprogressors who remained normoglycemic (n = 58). PI:C ratios were calculated as molar ratios and were multiplied by 100% to obtain PI levels as a percentage of C levels.

RESULTS

Although absolute PI levels did not differ between groups, PI:C ratios were significantly increased in antibody-positive subjects in whom there was progression to diabetes compared with nonprogressors (median 1.81% vs. 1.17%, P = 0.03). The difference between groups was most pronounced in subjects who were ≤10 years old, where the median progressor PI:C ratio was nearly triple that of nonprogressors; 90.0% of subjects in this age group within the upper PI:C quartile progressed to the development of diabetes. Logistic regression analysis, adjusted for age and BMI, demonstrated increased odds of progression for higher natural log PI:C ratio values (odds ratio 1.44, 95% CI 1.02, 2.05).

CONCLUSIONS

These data suggest that β-cell ER dysfunction precedes type 1 diabetes onset, especially in younger children. Elevations in the serum PI:C ratio may have utility in predicting the onset of type 1 diabetes in the presymptomatic phase.

The role of FOXP3 in autoimmunity

FOXP3 controls the development and function of T regulatory cells (Tregs). Autoimmunity is linked to changes in FOXP3 activity that can occur at multiple levels and lead to Treg dysfunction. For example, changes in IL-2 signaling, FOXP3 transcription and/or post-translational modifications can all contribute to loss of self-tolerance. As additional pathways of FOXP3 regulation are elucidated, new therapeutic approaches to increase Treg activity either by cell therapy or pharmacological intervention are being tested. Early success from pioneering studies of Treg-based therapy in transplantation has promoted the undertaking of similar studies in autoimmunity, with emerging evidence for the effectiveness of these approaches, particularly in the context of type 1 diabetes.

Caspase-1 as a multifunctional inflammatory mediator: noncytokine maturation roles

Caspase-1 is an inflammatory caspase that is activated through formation of inflammasome complexes in response to both pathogen-derived and endogenous mediators. The most well-known function of active caspase-1 is to cleave the proforms of inflammatory cytokines IL-1β and -18 into their active forms in response to inflammatory stimuli in immune cells. However, recent evidence suggests that caspase-1 has multiple functions in addition to this cytokine maturation role and that it is at the center of many cell responses to stress and inflammation. The current review focuses on roles for caspase-1, and the closely related caspase-11, in inflammatory forms of cell death and protein cleavage and also in protein secretion. These alternative caspase-1 functions can influence inflammatory responses, not just in immune cells but in other cell types, such as epithelia, where inflammatory cytokine production may not be a primary cell function.

The glucagon like peptide 1 analogue, exendin-4, attenuates oxidative stress-induced retinal cell death in early diabetic rats through promoting Sirt1 and Sirt3 expression

This study was aimed to further investigate the possible mechanisms by which the glucagon like peptide 1 analogue, exendin-4 (EX4), protects rat retinal cells at the early stage of diabetes. EX4 was injected intravitreally into normal and early-stage streptozotocin-diabetic rats. Cell death, reactive oxygen species (ROS), and electroretinogram (ERG) were measured. Sirtuin (Sirt) mRNA and protein were analyzed. In retinas of diabetic rats 1 month after diabetes onset, cell death and ROS level increased significantly, and the b-wave amplitudes and OPs were significantly reduced. Four days after intravitreal EX4 treatment, retinal cell death and ROS level in retinas reduced significantly, and visual function was recovered. In the retinas of early-stage diabetic rats, the expressions of Sirt1 and Sirt3 were also found to be significantly decreased, and both were back to normal levels after intravitreal injection of EX4. In R28 cells, hydrogen peroxide (H2O2) treatment increased ROS and cell death and decreased Sirt1 and Sirt3. With the addition of EX4 into the culture system, the expressions of Sirt1 and Sirt3 were increased, and the H2O2-induced ROS and cell death were significantly reduced. These results confirm a mechanism for EX4 to protect retinal cells from diabetic damage and oxidative injury. EX4 reduces retinal cell death and ROS generation by upregulating Sirt1 and Sirt3 expressions in the retina of early-stage diabetic rats as well as in H2O2-treated R28 cells.

Autoimmune regulator and self-tolerance - molecular and clinical aspects

The establishment of central tolerance in the thymus is critical for avoiding deleterious autoimmune diseases. Autoimmune regulator (AIRE), the causative gene in autoimmune polyendocrine syndrome type-1 (APS-1), is crucial for the establishment of self-tolerance in the thymus by promoting promiscuous expression of a wide array of tissue-restricted self-antigens. This step is critical for elimination of high-affinity self-reactive T cells from the immunological repertoire, and for the induction of a specific subset of Foxp3(+) T-regulatory (Treg ) cells. In this review, we discuss the most recent advances in our understanding of how AIRE operates on molecular and cellular levels, as well as of how its loss of function results in breakdown of self-tolerance mechanisms characterized by a broad and heterogeneous repertoire of autoimmune phenotypes.

Infancy-Onset T1DM, Short Stature, and Severe Immunodysregulation in Two Siblings With a Homozygous LRBA Mutation

CONTEXT

Type 1 diabetes mellitus (T1DM) is caused by autoimmunity against pancreatic β-cells. Although a significant number of T1DM patients have or will develop further autoimmune disorders during their lifetime, coexisting severe immunodysregulation is rare.

OBJECTIVE

Presuming autosomal-recessive inheritance in a complex immunodysregulation disorder including T1DM and short stature in two siblings, we performed whole-exome sequencing.

CASE PRESENTATION

Two Libyan siblings born to consanguineous parents were presented to our diabetology department at ages 12 and 5 years, respectively. Apart from T1DM diagnosed at age 2 years, patient 1 suffered from chronic restrictive lung disease, mild enteropathy, hypogammaglobulinemia, and GH deficiency. Fluorescence-activated cell sorting analysis revealed B-cell deficiency. In addition, CD4(+)/CD25(+) and CD25(high)/FoxP3(+) cells were diminished, whereas an unusual CD25(-)/FoxP3(+) population was detectable. The younger brother, patient 2, also developed T1DM during infancy. Although his enteropathy was more severe and electrolyte derangements repeatedly led to hospitalization, he did not have significant pulmonary problems. IgG levels and B-lymphocytes were within normal ranges.

RESULTS

By whole-exome sequencing we identified a homozygous truncating mutation (c.2445_2447del(C)3ins(C)2, p.P816Lfs*4) in the lipopolysaccharide-responsive beige-like anchor (LRBA) gene in both siblings. The diagnosis of LRBA deficiency was confirmed by a fluorescence-activated cell sorting-based immunoassay showing the absence of LRBA protein in phytohemagglutinin-stimulated peripheral blood mononuclear cells.

CONCLUSION

We identified a novel truncating LRBA mutation in two siblings with T1DM, short stature, and severe immunodysregulation. LRBA mutations have previously been reported to cause multiorgan autoimmunity and immunodysfunction. In light of the variable phenotypes reported so far in LRBA-mutant individuals, LRBA deficiency should be considered in all patients presenting with T1DM and signs of severe immunodysregulation.

Chromosome 18q deletion syndrome with autoimmune diabetes mellitus: putative genomic loci for autoimmunity and immunodeficiency

A girl with 18q deletion syndrome was diagnosed with autoimmune diabetes mellitus and Hashimoto's thyroiditis at the age of 3 yr. In addition, the girl suffered from recurrent infections due to immunoglobulin A and IgG4 deficiency. She was also found to have CD3+CD4+FoxP3+, CD3+CD4+FoxP3+CD25+, and CD3+CD4+CD25+CD127 regulatory T cells deficiency. The exceptional coincidence of the two autoimmune disorders occurring at an early age, and associated with immune deficiency, implies that genes located on deleted 19.4 Mbp region at 18q21.32-q23 (chr18:58,660,699-78,012,870) might play a role in the pathogenesis of autoimmunity leading to β cell destruction and diabetes.