Molecular circadian clock disruption in the leukocytes of individuals with type 2 diabetes and overweight, and its relationship with leukocyte-endothelial interactions

AIMS/HYPOTHESIS

Alterations in circadian rhythms increase the likelihood of developing type 2 diabetes and CVD. Circadian rhythms are controlled by several core clock genes, which are expressed in nearly every cell, including immune cells. Immune cells are key players in the pathophysiology of type 2 diabetes, and participate in the atherosclerotic process that underlies cardiovascular risk in these patients. The role of the core clock in the leukocytes of people with type 2 diabetes and the inflammatory process associated with it are unknown. We aimed to evaluate whether the molecular clock system is impaired in the leukocytes of type 2 diabetes patients and to explore the mechanism by which this alteration leads to an increased cardiovascular risk in this population.

METHODS

This is an observational cross-sectional study performed in 25 participants with type 2 diabetes and 28 healthy control participants. Clinical and biochemical parameters were obtained. Peripheral blood leukocytes were isolated using magnetic bead technology. RNA and protein lysates were obtained to assess clock-related gene transcript and protein levels using real-time PCR and western blot, respectively. Luminex XMAP technology was used to assess levels of inflammatory markers. Leukocyte-endothelial interaction assays were performed by perfusing participants' leukocytes or THP-1 cells (with/without CLK8) over a HUVEC monolayer in a parallel flow chamber using a dynamic adhesion system.

RESULTS

Participants with type 2 diabetes showed increased BMAL1 and NR1D1 mRNA levels and decreased protein levels of circadian locomotor output cycles kaput (CLOCK), cryptochrome 1 (CRY1), phosphorylated basic helix-loop-helix ARNT like 1 (p-BMAL1) and period circadian protein homologue 2 (PER2). Correlation studies revealed that these alterations in clock proteins were negatively associated with glucose, HbA1c, insulin and HOMA-IR levels and leukocyte cell counts. The leukocyte rolling velocity was reduced and rolling flux and adhesion were enhanced in individuals with type 2 diabetes compared with healthy participants. Interestingly, inhibition of CLOCK/BMAL1 activity in leukocytes using the CLOCK inhibitor CLK8 mimicked the effects of type 2 diabetes on leukocyte-endothelial interactions.

CONCLUSIONS/INTERPRETATION

Our study demonstrates alterations in the molecular clock system in leukocytes of individuals with type 2 diabetes, manifested in increased mRNA levels and decreased protein levels of the core clock machinery. These alterations correlated with the impaired metabolic and proinflammatory profile of the participants with type 2 diabetes. Our findings support a causal role for decreased CLOCK/BMAL1 activity in the increased level of leukocyte-endothelial interactions. Overall, our data suggest that alterations in core clock proteins accelerate the inflammatory process, which may ultimately precipitate the onset of CVD in patients with type 2 diabetes.

Circadian alignment of food intake and glycaemic control by time-restricted eating: A systematic review and meta-analysis

Daily rhythms of metabolic function are supported by molecular circadian clock systems that are strongly regulated by feeding and fasting. Intermittent fasting diets have been associated with weight loss and improved metabolism. However, the effects of time-restricted eating (TRE) on glycemic parameters are still under debate. In this review, we aim to systematically analyze the effects of TRE on glycemic parameters. We searched on PubMed, EMBASE, and the Cochrane Library for controlled studies in which subjects followed TRE for at least 4 weeks. 20 studies were included in the qualitative systematic review, and 18 studies (n = 1169 subjects) were included in the meta-analysis. Overall, TRE had no significant effect on fasting glucose (Hedges's g = -0.08; 95% CI:-0.31,0.16; p = 0.52), but it did reduce HbA1c levels (Hedges's g = -0.27; 95% CI: -0.47, -0.06; p = 0.01). TRE significantly reduced fasting insulin (Hedges's g = -0.40; 95% CI: -0.73,-0.08; p = 0.01) and showed a tendency to decrease HOMA-IR (Hedges's g = -0.32; 95% CI:-0.66,0.02; p = 0.06). Interestingly, a cumulative analysis showed that the beneficial effects of TRE regarding glucose levels were less apparent as studies with later TRE windows (lTRE) were being included. Indeed, a subgroup analysis of the early TRE (eTRE) studies revealed that fasting glucose was significantly reduced by eTRE (Hedges's g = -0.38; 95% CI:-0.62, -0.14; p < 0.01). Our meta-analysis suggests that TRE can reduce HbA1c and insulin levels, and that timing of food intake is a crucial factor in the metabolic benefit of TRE, as only eTRE is capable of reducing fasting glucose levels in subjects with overweight or obesity.PROSPERO registration number CRD42023405946.

Cardiovascular benefits of SGLT2 inhibitors and GLP-1 receptor agonists through effects on mitochondrial function and oxidative stress

Overloaded glucose levels in several metabolic diseases such as type 2 diabetes (T2D) can lead to mitochondrial dysfunction and enhanced production of reactive oxygen species (ROS). Oxidative stress and altered mitochondrial homeostasis, particularly in the cardiovascular system, contribute to the development of chronic comorbidities of diabetes. Diabetes-associated hyperglycemia and dyslipidemia can directly damage vascular vessels and lead to coronary artery disease or stroke, and indirectly damage other organs and lead to kidney dysfunction, known as diabetic nephropathy. The new diabetes treatments include Na+-glucose cotransporter 2 inhibitors (iSGLT2) and glucagon-like 1 peptide receptor agonists (GLP-1RA), among others. The iSGLT2 are oral anti-diabetic drugs, whereas GLP-1RA are preferably administered through subcutaneous injection, even though GLP-1RA oral formulations have recently become available. Both therapies are known to improve both carbohydrate and lipid metabolism, as well as to improve cardiovascular and cardiorenal outcomes in diabetic patients. In this review, we present an overview of current knowledge on the relationship between oxidative stress, mitochondrial dysfunction, and cardiovascular therapeutic benefits of iSGLT2 and GLP-1RA. We explore the benefits, limits and common features of the treatments and remark how both are an interesting target in the prevention of obesity, T2D and cardiovascular diseases, and emphasize the lack of a complete understanding of the underlying mechanism of action.

Effect of a Very Low-Calorie Diet on Oxidative Stress, Inflammatory and Metabolomic Profile in Metabolically Healthy and Unhealthy Obese Subjects

The purpose of the study was to determine the impact of weight loss through calorie restriction on metabolic profile, and inflammatory and oxidative stress parameters in metabolically healthy (MHO) and unhealthy (MUHO) obese individuals. A total of 74 subjects (34 MHO and 40 MUHO) received two cycles of a very low-calorie diet, alternating with a hypocaloric diet for 24 weeks. Biochemical, oxidative stress, and inflammatory markers, as well as serum metabolomic analysis by nuclear magnetic resonance, were performed at baseline and at the end of the intervention. After the diet, there was an improvement in insulin resistance, as well as a significant decrease in inflammatory parameters, enhancing oxidative damage, mitochondrial membrane potential, glutathione, and antioxidant capacity. This improvement was more significant in the MUHO group. The metabolomic analysis showed a healthier profile in lipoprotein profile. Lipid carbonyls also decrease at the same time as unsaturated fatty acids increase. We also display a small decrease in succinate, glycA, alanine, and BCAAs (valine and isoleucine), and a slight increase in taurine. These findings show that moderate weight reduction leads to an improvement in lipid profile and subfractions and a reduction in oxidative stress and inflammatory markers; these changes are more pronounced in the MUHO population.

Effects of GLP-1 receptor agonists on mitochondrial function, inflammatory markers and leukocyte-endothelium interactions in type 2 diabetes

OBJECTIVE

Type 2 diabetes (T2D) is linked to metabolic, mitochondrial and inflammatory alterations, atherosclerosis development and cardiovascular diseases (CVDs). The aim was to investigate the potential therapeutic benefits of GLP-1 receptor agonists (GLP-1 RA) on oxidative stress, mitochondrial respiration, leukocyte-endothelial interactions, inflammation and carotid intima-media thickness (CIMT) in T2D patients.

RESEARCH DESIGN AND METHODS

Type 2 diabetic patients (255) and control subjects (175) were recruited, paired by age and sex, and separated into two groups: without GLP-1 RA treatment (196) and treated with GLP-1 RA (59). Peripheral blood polymorphonuclear leukocytes (PMNs) were isolated to measure reactive oxygen species (ROS) production by flow cytometry and oxygen consumption with a Clark electrode. PMNs were also used to assess leukocyte-endothelial interactions. Circulating levels of adhesion molecules and inflammatory markers were quantified by Luminex's technology, and CIMT was measured as surrogate marker of atherosclerosis.

RESULTS

Treatment with GLP-1 RA reduced ROS production and recovered mitochondrial membrane potential, oxygen consumption and MPO levels. The velocity of leukocytes rolling over endothelial cells increased in PMNs from GLP-1 RA-treated patients, whereas rolling and adhesion were diminished. ICAM-1, VCAM-1, IL-6, TNFα and IL-12 protein levels also decreased in the GLP-1 RA-treated group, while IL-10 increased. CIMT was lower in GLP-1 RA-treated T2D patients than in T2D patients without GLP-1 RA treatment.

CONCLUSIONS

GLP-1 RA treatment improves the redox state and mitochondrial respiration, and reduces leukocyte-endothelial interactions, inflammation and CIMT in T2D patients, thereby potentially diminishing the risk of atherosclerosis and CVDs.

Metformin and its redox-related mechanisms of action in type 2 diabetes

Type 2 diabetes (T2D) is a long-term metabolic disease characterized by progressive β-cell functional decline and insulin resistance, which increases the risk of cardiovascular complications as well as associated-morbidity and mortality. Evidence suggests a strong relationship between hyperglycaemia, oxidative stress and the development and progression of T2D. Indeed, a hyperglycaemic state can reduce the activity of antioxidant enzymes and increase lipid peroxidation and protein oxidation products, as well as DNA damage. At present, metformin is the recommended first-line glucose-lowering agent in patients with T2D. Despite the vast clinical experience gained over several decades of use, several mechanisms of action of metformin have yet to be fully elucidated. This review provides an overview of the existing literature concerning the complicated interplay between oxidative stress and T2D and the molecular mechanisms underlying the redox-related mechanisms of action of metformin, which include (but are not limited to) interaction with AMP-activated protein kinase (AMPK)-dependent and AMPK-independent mechanisms, inhibition of gluconeogenesis and action on leukocyte–endothelium interactions.

Mitochondrial redox impairment and enhanced autophagy in peripheral blood mononuclear cells from type 1 diabetic patients

Type 1 diabetes (T1D) involves critical metabolic disturbances that contribute to an increased cardiovascular risk. Leukocytes are key players in the onset of atherosclerosis due to their interaction with the endothelium. However, whether mitochondrial redox impairment, altered bioenergetics and abnormal autophagy in leukocytes contribute to T1D physiopathology is unclear. In this study we aimed to evaluate the bioenergetic and redox state of peripheral blood mononuclear cells (PBMCs) from T1D patients in comparison to those from healthy subjects, and to assess autophagy induction and leukocyte-endothelial interactions. T1D patients presented lower levels of fast-acting and total antioxidants in their blood, and their leukocytes produced higher amounts of total reactive oxygen species (ROS) and superoxide radical with respect to controls. Basal and ATP-linked respiration were similar in PBMCs from T1D and controls, but T1D PBMCs exhibited reduced spare respiratory capacity and a tendency toward decreased maximal respiration and reduced non-mitochondrial respiration, compared to controls. The autophagy markers P-AMPK, Beclin-1 and LC3-II/LC3-I were increased, while P62 and NBR1 were decreased in T1D PBMCs versus those from controls. Leukocytes from T1D patients displayed lower rolling velocity, higher rolling flux and more adhesion to the endothelium versus controls. Our findings show that T1D impairs mitochondrial function and promotes oxidative stress and autophagy in leukocytes, and suggest that these mechanisms contribute to an increased risk of atherosclerosis by augmenting leukocyte-endothelial interactions.

Gold Nanoparticles Supported on Ceria Nanoparticles Modulate Leukocyte-Endothelium Cell Interactions and Inflammation in Type 2 Diabetes

Gold-ceria nanoparticles (Au/CeO2) are known to have antioxidant properties. However, whether these nanoparticles can provide benefits in type 2 diabetes mellitus (T2D) remains unknown. This work aimed to study the effects of Au/CeO2 nanoparticles at different rates of gold purity (10, 4.4, 1.79 and 0.82) on leukocyte-endothelium interactions and inflammation in T2D patients. Anthropometric and metabolic parameters, leukocyte-endothelium interactions, ROS production and NF-κB expression were assessed in 57 T2D patients and 51 healthy subjects. T2D patients displayed higher Body Mass Index (BMI) and characteristic alterations in carbohydrate and lipid metabolism. ROS production was increased in leukocytes of T2D patients and decreased by Au/CeO2 at 0.82% gold. Interestingly, Au/CeO2 0.82% modulated leukocyte-endothelium interactions (the first step in the atherosclerotic process) by increasing leukocyte rolling velocity and decreasing rolling flux and adhesion in T2D. A static adhesion assay also revealed diminished leukocyte-endothelium interactions by Au/CeO2 0.82% treatment. NF-κB (p65) levels increased in T2D patients and were reduced by Au/CeO2 treatment. Cell proliferation, viability, and apoptosis assays demonstrated no toxicity produced by Au/CeO2 nanoparticles. These results demonstrate that Au/CeO2 nanoparticles at 0.82% exert antioxidant and anti-inflammatory actions in the leukocyte-endothelium interaction of T2D patients, suggesting a protective role against the appearance of atherosclerosis and cardiovascular diseases when this condition exists.

Targeting mitochondria: a great boon to fight type 2 diabetes

Type 2 diabetes is a chronic metabolic disease characterized by the development of low-grade systemic inflammation, hyperglycaemia, and hyperlipidaemia. These pathogenic traits have a profound impact on mitochondrial function as mitochondria serve as intermediary organelles between nutrients and energy production. Moreover, the mitochondrial quality control system is also altered and rendered defective by type 2 diabetes. These alterations entail the accumulation of defective mitochondria, which causes the diabetic background to deteriorate further. In this context, it is of paramount importance to improve mitochondrial function and ameliorate the consequences of mitochondrial dysfunction. This review assesses different treatments that target mitochondrial dysfunction as a way of treating type 2 diabetes. Lifestyle interventions and pharmacological treatments such as biguanides, thiazolidinediones, a-glucosidase inhibitors, glucagon-like peptide 1 receptor agonists, or sodium-glucose co-transporter-2 inhibitors protect mitochondrial function, while novel mitochondria-targeted molecules including natural compounds, mitochondria-targeted antioxidants, inhibitors of mitochondria pore transition pore opening, NO and H2S donors, and inhibitors of mitochondrial fission positively impact on mitochondrial function and its quality control mechanisms. Most of these therapeutic tools require more research, but they already show promising therapeutic mechanisms that improve type 2 diabetes and its cellular consequences.

Exercise Training Promotes Sex-Specific Adaptations in Mouse Inguinal White Adipose Tissue

Recent studies demonstrate that adaptations to white adipose tissue (WAT) are important components of the beneficial effects of exercise training on metabolic health. Exercise training favorably alters the phenotype of subcutaneous inguinal WAT (iWAT) in male mice, including decreasing fat mass, improving mitochondrial function, inducing beiging, and stimulating the secretion of adipokines. In this study, we find that despite performing more voluntary wheel running compared with males, these adaptations do not occur in the iWAT of female mice. Consistent with sex-specific adaptations, we report that mRNA expression of androgen receptor coactivators is upregulated in iWAT from trained male mice and that testosterone treatment of primary adipocytes derived from the iWAT of male, but not female mice, phenocopies exercise-induced metabolic adaptations. Sex specificity also occurs in the secretome profile, as we identify cysteine-rich secretory protein 1 (Crisp1) as a novel adipokine that is only secreted from male iWAT in response to exercise. Crisp1 expression is upregulated by testosterone and functions to increase glucose and fatty acid uptake. Our finding that adaptations to iWAT with exercise training are dramatically greater in male mice has potential clinical implications for understanding the different metabolic response to exercise training in males and females and demonstrates the importance of investigating both sexes in studies of adipose tissue biology.

Characterization of Differentially Expressed Circulating miRNAs in Metabolically Healthy versus Unhealthy Obesity

Obese individuals without metabolic comorbidities are categorized as metabolically healthy obese (MHO). MicroRNAs (miRNAs) may be implicated in MHO. This cross-sectional study explores the link between circulating miRNAs and the main components of metabolic syndrome (MetS) in the context of obesity. We also examine oxidative stress biomarkers in MHO vs. metabolically unhealthy obesity (MUO). We analysed 3536 serum miRNAs in 20 middle-aged obese individuals: 10 MHO and 10 MUO. A total of 159 miRNAs were differentially expressed, of which, 72 miRNAs (45.2%) were higher and 87 miRNAs (54.7%) were lower in the MUO group. In addition, miRNAs related to insulin signalling and lipid metabolism pathways were upregulated in the MUO group. Among these miRNAs, hsa-miR-6796-5p and hsa-miR-4697-3p, which regulate oxidative stress, showed significant correlations with glucose, triglycerides, HbA1c and HDLc. Our results provide evidence of a pattern of differentially expressed miRNAs in obesity according to MetS, and identify those related to insulin resistance and lipid metabolism pathways.

Metformin induces lipid changes on sphingolipid species and oxidized lipids in polycystic ovary syndrome women

Metformin is one of the treatments used for PCOS pathology decreasing body weight, plasma androgen, FSH and glucose levels. Unfortunately, there is little known about metformin's effects on lipid metabolism, a crucial process in PCOS pathology. We have employed a lipidomic approach to explore alterations in the plasma lipid profile of patients with PCOS following metformin treatment. The aim is to offer new insights about the effect of metformin in PCOS patients. Plasma samples were obtained from 27 subjects prior to and following 12 weeks of metformin treatment. A detailed biochemical characterization and lipidomic profile was performed. Metformin reduces BMI, HOMA-IR, FSH and androstenedione and increases DHEA-S but no changes were found in glucose levels after treatment. Multivariate statistics revealed a specific lipidomic signature due to the effect of 12 weeks of metformin treatment in PCOS patients. This signature includes changes in sphingolipid metabolism suggesting a crosstalk between these lipid species and the androgenic metabolism and a decrease in oxidized lipids reinforcing that metformin treatment improves oxidative stress status. Our study confirms the specific effect of metformin in lipid metabolism on women with PCOS after 12 weeks of treatment.

The SGLT2 Inhibitor Empagliflozin Ameliorates the Inflammatory Profile in Type 2 Diabetic Patients and Promotes an Antioxidant Response in Leukocytes

Sodium-glucose co-transporter 2 inhibitors (iSGLT2) have been linked to a considerable reduction in cardiovascular risk in patients with type 2 diabetes (T2D), but the precise molecular mechanisms are still elusive. We aimed to evaluate the effects of the iSGLT2 empagliflozin on systemic inflammation and its potential antioxidant properties. This is an observational, prospective follow-up study of a cohort of fifteen patients with T2D who received 10 mg/day of empagliflozin according to standard clinical care. Measures at baseline, 12 and 24 weeks were taken. Metabolic and anthropometric parameters were evaluated. Production of mitochondrial superoxide, glutathione content, and glutathione s-reductase and catalase mRNA levels were measured in leukocytes. Serum levels of myeloperoxidase, hs-CRP and IL-10 were determined. In addition to decreased body weight and reduced glucose and HbA1c levels, we observed a reduction in superoxide production in leukocytes of diabetic patients and increased glutathione content, prominently after 24 weeks of empagliflozin treatment. Leukocyte expression of glutathione s-reductase and catalase, and serum levels of IL-10 were enhanced at 24 weeks of empagliflozin treatment. Concomitantly, reduced hs-CRP and myeloperoxidase levels were seen. This study provides evidence of the antioxidant and anti-inflammatory properties of empagliflozin treatment in humans, which may contribute to its beneficial cardiovascular effects.

The Mitochondria-Targeted Antioxidant MitoQ Modulates Mitochondrial Function and Endoplasmic Reticulum Stress in Pancreatic β Cells Exposed to Hyperglycaemia

BACKGROUND/AIMS

Mitochondria-targeted antioxidants such as mitoquinone (MitoQ) have demonstrated protective effects against oxidative damage in several diseases. The increase in reactive oxygen species (ROS) production during glucose metabolism in β cells can be exacerbated under hyperglycaemic conditions such as type 2 diabetes (T2D), thus contributing to β cell function impairment. In the present work, we aimed to evaluate the effect of MitoQ on insulin secretion, oxidative stress, endoplasmic reticulum (ER) stress and nuclear factor kappa B (NFκB) signalling in a pancreatic β cell line under normoglycaemic (NG, 11.1 mM glucose), hyperglycaemic (HG, 25 mM glucose) and lipidic (palmitic acid (PA), 0.5mM) conditions.

METHODS

We incubated the pancreatic β cell line INS-1E with or without MitoQ (0.5µM) under NG, HG and PA conditions. We then assessed the following parameters: glucose-induced insulin secretion, O₂ consumption (with a Clark-type electrode); mitochondrial function, oxidative stress parameters and calcium levels (by fluorescence microscopy); ER stress markers and NFκB-p65 protein levels (by western blotting).

RESULTS

MitoQ increased insulin secretion and prevented the enhancement of ROS production and O₂ consumption and decrease in GSH levels that are characteristic under HG conditions. MitoQ also reduced protein levels of ER stress markers (GRP78 and P-eIF2α) and the proinflammatory nuclear transcription factor NFκB-p65, both of which increased under HG. MitoQ did not significantly alter ER stress markers under lipidic conditions.

CONCLUSION

Our findings suggest that treatment with MitoQ modulates mitochondrial function, which in turn ameliorates endoplasmic reticulum stress and NFκB activation, thereby representing potential benefits for pancreatic β cell function.

Does Glycemic Control Modulate the Impairment of NLRP3 Inflammasome Activation in Type 2 Diabetes?

Since mitochondrial dysfunction is associated with NOD-like receptor family protein 3 (NLRP3) activation in type 2 diabetes (T2D), which can eventually lead to an impaired immune response, we set out to determine if glycemic control modulates the effects of T2D on the NLRP3 inflammasome. We have studied leukocytes from 61 diabetic patients [25 with glycated hemoglobin (HbA_1c) ≤7% and 36 with HbA_1c ≥8%] and 40 healthy controls. Total and mitochondrial reactive oxygen species (ROS) production was enhanced in T2D patients, and mitochondrial ROS was more pronounced in those with poor glycemic control. Levels of gene and protein expression of NLRP3 were decreased in both diabetic groups and more so in those with HbA_1c ≥8%. In addition, there was a decrease in gene expression and serum concentrations of interleukin (IL)-1β, IL-12, and caspase-1 in line with inhibition of the NLRP3 inflammasome. Our data also suggest negative correlations between HbA_1c levels and NLRP3 protein expression, serum levels of IL-12 and IL-1β, and caspase-1 messenger RNA expression. Our findings lead us to raise the hypothesis of an association between poor glycemic control in T2D and an impairment of the NLRP3 inflammasome, suggesting that glycemic control plays an important role in the immune response of diabetic subjects.

Pinitol alleviates systemic inflammatory cytokines in human obesity by a mechanism involving unfolded protein response and sirtuin 1

BACKGROUND & AIMS

It is known that pinitol acts as a mediator of the insulin-signaling pathway, though little is known about its anti-inflammatory effect in human obesity. Therefore, this study aimed to evaluate the effect of pinitol on peripheral blood mononuclear cells (PBMCs) and visceral (VAT) and subcutaneous adipose tissues (SAT), focusing on the involvement of endoplasmic reticulum (ER) stress and sirtuin 1 (SIRT1).

METHODS

In the intervention study, thirteen obese subjects consumed a pinitol-enriched beverage (PEB) for 12 weeks. In the ex vivo study, a biopsy of VAT and SAT was removed from thirty-four obese patients and incubated with D-pinitol for 48 h.

RESULTS

The consumption of a PEB reduced circulating levels of IL6 and TNFα and increased SIRT1 protein expression in PBMCs. Ex vivo experiments showed a decline in gene expression and protein levels of IL6 and TNFα in SAT and a reduction in ER stress parameters (ATF6 and CHOP), while VAT markers remained unaltered. Differential gene expression profiles revealed an up-regulation of SIRT1 and insulin-signaling pathways in SAT with respect to VAT.

CONCLUSIONS

Our results suggests that pinitol down-regulates the inflammatory pathway which may lead to novel treatment options for obesity and its metabolic disorders.

The mitochondrial antioxidant SS-31 increases SIRT1 levels and ameliorates inflammation, oxidative stress and leukocyte-endothelium interactions in type 2 diabetes

There is growing focus on mitochondrial impairment and cardiovascular diseases (CVD) in type 2 diabetes (T2D), and the development of novel therapeutic strategies in this context. It is unknown whether mitochondrial-targeting antioxidants such as SS-31 protect sufficiently against oxidative damage in diabetes. We aimed to evaluate if SS-31 modulates SIRT1 levels and ameliorates leukocyte-endothelium interactions, oxidative stress and inflammation in T2D patients. Anthropometric and metabolic parameters were studied in 51 T2D patients and 57 controls. Production of mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential, glutathione content, leukocyte-endothelium interactions, NFκB-p65, TNFα and SIRT1 levels was measured in leukocytes treated or not with SS-31. We observed increased mitochondrial ROS production that was restored by SS-31 treatment. SS-31 also increased mitochondrial membrane potential, glutathione content, SIRT1 levels and leukocyte rolling velocity and reduced rolling flux and adhesion in T2D patients. NFκB-p65 and TNFα, which were enhanced in diabetic patients, were also reduced by SS-31 treatment. Our results reveal that SS-31 exerts beneficial effects on the leukocytes of T2D patients by reducing oxidative stress, leukocyte-endothelium interactions, NFκB and TNFα and by increasing SIRT1 levels. These actions support its use as a potential agent against CVD risk.

Moderate weight loss attenuates chronic endoplasmic reticulum stress and mitochondrial dysfunction in human obesity

OBJECTIVE

In obese patients undergoing caloric restriction, there are several potential mechanisms involved in the improvement of metabolic outcomes. The present study further explores whether caloric restriction can modulate endoplasmic reticulum (ER) stress and mitochondrial function, as both are known to be mechanisms underlying inflammation and insulin resistance (IR) during obesity.

METHODS

A total of 64 obese patients with BMI ≥35 kg/m² underwent a dietary program consisting of 6 weeks of a very-low-calorie diet followed by 18 weeks of low-calorie diet. We evaluated changes in the metabolic and inflammatory markers -TNFα, hsCRP, complement component 3 (C3c), and retinol binding protein 4 (RBP4)-, in the ER stress markers and modulators -eIF2α-P, sXBP1, ATF6, JNK-P, CHOP, GRP78, and SIRT1-, and in mitochondrial function parameters -mitochondrial reactive oxygen species (mROS), glutathione peroxidase 1 (GPX1), cytosolic Ca²⁺, and mitochondrial membrane potential.

RESULTS

The dietary intervention produced an 8.85% weight loss associated with enhanced insulin sensitivity, a less marked atherogenic lipid profile, and a decrease in systemic inflammation (TNFα, hsCRP) and adipokine levels (RBP4 and C3c). Chronic ER stress was significantly reduced (ATF6-CHOP, JNK-P) and expression levels of SIRT1 and GRP78 - a Ca²⁺-dependent chaperone - were increased and accompanied by the restoration of Ca²⁺ depots. Furthermore, mROS production and mitochondrial membrane potential improvement were associated with the up-regulation of the antioxidant enzyme GPX1.

CONCLUSIONS

Our data provide evidence that moderate weight loss attenuates systemic inflammation and IR and promotes the amelioration of ER stress and mitochondrial dysfunction, increasing the expression of chaperones, SIRT1 and antioxidant GPX1.

Mitochondria, the NLRP3 Inflammasome, and Sirtuins in Type 2 Diabetes: New Therapeutic Targets

SIGNIFICANCE

Type 2 diabetes mellitus and hyperglycemia can lead to the development of comorbidities such as atherosclerosis and microvascular/macrovascular complications. Both type 2 diabetes and its complications are related to mitochondrial dysfunction and oxidative stress. Type 2 diabetes is also a chronic inflammatory condition that leads to inflammasome activation and the release of proinflammatory mediators, including interleukins (ILs) IL-1β and IL-18. Moreover, sirtuins are energetic sensors that respond to metabolic load, which highlights their relevance in metabolic diseases, such as type 2 diabetes. Recent Advances: Over the past decade, great progress has been made in clarifying the signaling events regulated by mitochondria, inflammasomes, and sirtuins. Nod-like receptor family pyrin domain containing 3 (NLRP3) is the best characterized inflammasome, and the generation of oxidant species seems to be critical for its activation. NLRP3 inflammasome activation and altered sirtuin levels have been observed in type 2 diabetes. Critical Issue: Despite increasing evidence of the relationship between the NLRP3 inflammasome, mitochondrial dysfunction, and oxidative stress and of their participation in type 2 diabetes physiopathology, therapeutic strategies to combat type 2 diabetes that target NLRP3 inflammasome and sirtuins are yet to be consolidated.

FUTURE DIRECTIONS

In this review article, we attempt to provide an overview of the existing literature concerning the crosstalk between mitochondrial impairment and the inflammasome, with particular attention to cellular and mitochondrial redox metabolism and the potential role of the NLRP3 inflammasome and sirtuins in the pathogenesis of type 2 diabetes. In addition, we discuss potential targets for therapeutic intervention based on these molecular interactions. Antioxid. Redox Signal. 29, 749-791.

Does Metformin Modulate Endoplasmic Reticulum Stress and Autophagy in Type 2 Diabetic Peripheral Blood Mononuclear Cells?

Since type 2 diabetes (T2D) is associated with oxidative stress and metformin has been shown to exert a protective role against the said stress, we wondered whether metformin treatment might also modulate endoplasmic reticulum (ER) stress and autophagy in leukocytes of T2D patients. We studied 53 T2D patients (37 of whom had been treated with metformin 1700 mg for at least 1 year) and 30 healthy volunteers. Leukocytes from both groups of T2D patients exhibited increased protein levels of 78-kDa glucose-regulated protein (GRP78) with respect to controls, whereas activating transcription factor 6 (ATF6) was enhanced specifically in nonmetformin-treated T2D, and (s-xbp1) and phosphorylated eukaryotic initiation factor 2α (p-eIF2α) increased only in the metformin-treated group. The autophagy markers beclin1 (becn1), autophagy-related 7 (atg7), and microtubule-associated protein 1A/1B-light chain 3II/I (LC3 II/I) increased in nonmetformin-treated T2D, and metformin treatment reduced mitochondrial superoxide and increased glutathione (GSH) levels. Our observations raise the question of whether metformin treatment could reduce oxidative stress and act as an ER stress modulator in T2D patients by promoting an adaptive unfolded protein response (s-xbp1 and p-eIF2α) in their leukocytes; this was in contrast with nonmetformin-treated patients whose response could be driven by the ATF6-dependent pro-apoptotic pathway. Further, our findings lead to us to form the hypothesis of an autophagy-dependent clearance of misfolded proteins in nonmetformin-treated T2D patients that could be repressed by metformin treatment.-Antioxid. Redox Signal. 28, 1562-1569.