Metabolic memory and chronic diabetes complications: potential role for epigenetic mechanisms

Activation of SIRT1 by silibinin improved mitochondrial health and alleviated the oxidative damage in experimental diabetic neuropathy and high glucose-mediated neurotoxicity

BACKGROUND

Silibinin (SBN), a sirtuin 1 (SIRT1) activator, has been evaluated for its anti-inflammatory activity in many inflammatory diseases. However, its role in diabetes-induced peripheral neuropathy (DPN) remains unknown. The SIRT1 activation convalesces nerve functions by improving mitochondrial biogenesis and mitophagy.

METHODS

DPN was induced by streptozotocin (STZ) at a dose of 55 mg/kg, i.p. in the male SD rats whereas neurotoxicity was induced in Neuro2A cells by 30 mM (high glucose) glucose. Neurobehavioural (nerve conduction velocity and nerve blood flow) western blot, immunohistochemistry, and immunocytochemistry were performed to evaluate the protein expression and their cellular localisation.

RESULTS

Two-week SBN treatment improved neurobehavioural symptoms, SIRT1, PGC-1α, and TFAM expression in the sciatic nerve and HG insulted N2A cells. It has also maintained the mitophagy by up-regulating PARL, PINK1, PGAM5, LC3 level and provided antioxidant defence by upregulating Nrf2.

CONCLUSION

SBN has shown neuroprotective potential in DPN through SIRT1 activation and antioxidant mechanism.

Cannabidiol and Beta-Caryophyllene Combination Attenuates Diabetic Neuropathy by Inhibiting NLRP3 Inflammasome/NFκB through the AMPK/sirT3/Nrf2 Axis

BACKGROUND

In this study, we investigated in detail the role of cannabidiol (CBD), beta-caryophyllene (BC), or their combinations in diabetic peripheral neuropathy (DN). The key factors that contribute to DN include mitochondrial dysfunction, inflammation, and oxidative stress.

METHODS

Briefly, streptozotocin (STZ) (55 mg/kg) was injected intraperitoneally to induce DN in Sprague-Dawley rats, and we performed procedures involving Randall Sellito calipers, a Von Frey aesthesiometer, a hot plate, and cold plate methods to determine mechanical and thermal hyperalgesia in vivo. The blood flow to the nerves was assessed using a laser Doppler device. Schwann cells were exposed to high glucose (HG) at a dose of 30 mM to induce hyperglycemia and DCFDA, and JC1 and Mitosox staining were performed to determine mitochondrial membrane potential, reactive oxygen species, and mitochondrial superoxides in vitro. The rats were administered BC (30 mg/kg), CBD (15 mg/kg), or combination via i.p. injections, while Schwann cells were treated with 3.65 µM CBD, 75 µM BC, or combination to assess their role in DN amelioration.

RESULTS

Our results revealed that exposure to BC and CBD diminished HG-induced hyperglycemia in Schwann cells, in part by reducing mitochondrial membrane potential, reactive oxygen species, and mitochondrial superoxides. Furthermore, the BC and CBD combination treatment in vivo could prevent the deterioration of the mitochondrial quality control system by promoting autophagy and mitochondrial biogenesis while improving blood flow. CBD and BC treatments also reduced pain hypersensitivity to hyperalgesia and allodynia, with increased antioxidant and anti-inflammatory action in diabetic rats. These in vivo effects were attributed to significant upregulation of AMPK, sirT3, Nrf2, PINK1, PARKIN, LC3B, Beclin1, and TFAM functions, while downregulation of NLRP3 inflammasome, NFκB, COX2, and p62 activity was noted using Western blotting.

CONCLUSIONS

the present study demonstrated that STZ and HG-induced oxidative and nitrosative stress play a crucial role in the pathogenesis of diabetic neuropathy. We find, for the first time, that a CBD and BC combination ameliorates DN by modulating the mitochondrial quality control system.

DNA Methylation Profiles of PSMA6, PSMB5, KEAP1, and HIF1A Genes in Patients with Type 1 Diabetes and Diabetic Retinopathy

We explored differences in the DNA methylation statuses of PSMA6, PSMB5, HIF1A, and KEAP1 gene promoter regions in patients with type 1 diabetes and different diabetic retinopathy (DR) stages. Study subjects included individuals with no DR (NDR, n = 41), those with non-proliferative DR (NPDR, n = 27), and individuals with proliferative DR or those who underwent laser photocoagulation (PDR/LPC, n = 46). DNA methylation was determined by Zymo OneStep qMethyl technique. The methylation of PSMA6 (NDR 5.9 (3.9-8.7) %, NPDR 4.5 (3.8-5.7) %, PDR/LPC 6.6 (4.7-10.7) %, p = 0.003) and PSMB5 (NDR 2.2 (1.9-3.7) %, NPDR 2.2 (1.9-3.0) %, PDR/LPC 3.2 (2.5-7.1) %, p < 0.01) differed across the groups. Consistent correlations were observed between the methylation levels of HIF1A and PSMA6 in all study groups. DNA methylation levels of PSMA6, PSMB5, and HIF1A genes were positively correlated with the duration of diabetes, HbA1c, and albuminuria in certain study groups. Univariate regression models revealed a significant association between the methylation level z-scores of PSMA6, PSMB5, and HIF1A and severe DR (PSMA6: OR = 1.96 (1.15; 3.33), p = 0.013; PSMB5: OR = 1.90 (1.14; 3.16), p = 0.013; HIF1A: OR = 3.19 (1.26; 8.06), p = 0.014). PSMB5 remained significantly associated with DR in multivariate analysis. Our findings suggest significant associations between the severity of DR and the DNA methylation levels of the genes PSMA6, PSMB5, and HIF1A, but not KEAP1 gene.

Smooth muscle NF90 deficiency ameliorates diabetic atherosclerotic calcification in male mice via FBXW7-AGER1-AGEs axis

Hyperglycemia accelerates calcification of atherosclerotic plaques in diabetic patients, and the accumulation of advanced glycation end products (AGEs) is closely related to the atherosclerotic calcification. Here, we show that hyperglycemia-mediated AGEs markedly increase vascular smooth muscle cells (VSMCs) NF90/110 activation in male diabetic patients with atherosclerotic calcified samples. VSMC-specific NF90/110 knockout in male mice decreases obviously AGEs-induced atherosclerotic calcification, along with the inhibitions of VSMC phenotypic changes to osteoblast-like cells, apoptosis, and matrix vesicle release. Mechanistically, AGEs increase the activity of NF90, which then enhances ubiquitination and degradation of AGE receptor 1 (AGER1) by stabilizing the mRNA of E3 ubiquitin ligase FBXW7, thus causing the accumulation of more AGEs and atherosclerotic calcification. Collectively, our study demonstrates the effects of VSMC NF90 in mediating the metabolic imbalance of AGEs to accelerate diabetic atherosclerotic calcification. Therefore, inhibition of VSMC NF90 may be a potential therapeutic target for diabetic atherosclerotic calcification.

Fibroblasts in Diabetic Foot Ulcers

Fibroblasts are stromal cells ubiquitously distributed in the body of nearly every organ tissue. These cells were previously considered to be "passive cells", solely responsible for ensuring the turnover of the extracellular matrix (ECM). However, their versatility, including their ability to switch phenotypes in response to tissue injury and dynamic activity in the maintenance of tissue specific homeostasis and integrity have been recently revealed by the innovation of technological tools such as genetically modified mouse models and single cell analysis. These highly plastic and heterogeneous cells equipped with multifaceted functions including the regulation of angiogenesis, inflammation as well as their innate stemness characteristics, play a central role in the delicately regulated process of wound healing. Fibroblast dysregulation underlies many chronic conditions, including cardiovascular diseases, cancer, inflammatory diseases, and diabetes mellitus (DM), which represent the current major causes of morbidity and mortality worldwide. Diabetic foot ulcer (DFU), one of the most severe complications of DM affects 40 to 60 million people. Chronic non-healing DFU wounds expose patients to substantial sequelae including infections, gangrene, amputation, and death. A complete understanding of the pathophysiology of DFU and targeting pathways involved in the dysregulation of fibroblasts are required for the development of innovative new therapeutic treatments, critically needed for these patients.

A pathological convergence theory for non-communicable diseases

The current paradigm considers the study of non-communicable diseases (NCDs), which are the main causes of mortality, as individual disorders. Nevertheless, this conception is being solidly challenged by numerous remarkable studies. The clear fact that the mortality, by virtually all NCDs, tends to cluster at old ages (with the exception of congenital malformations and certain types of cancer, among a few others); makes us intuitive to assume that the common convergence mechanism that exponentially increases mortality by almost all NCDs in older ages is cell aging. Moreover, when we study NCDs, we are not analyzing which disorders cause the mortality of the populations, rather that which disorders kill us before others do, because the aging of the individuals causes inevitably their death by one cause or another. This is not a defeatist perspective, but a challenging and efficient one. These intuitive assumptions have been supported by studies from the pathophysiologic, epidemiologic, and genetic fields, leading to the affirmation that, as NCDs share genetic and pathophysiological mechanisms (derived from mostly the same risk factors), they should no longer be considered independently. Those studies should make us reconsider our current conceptions of studying NCDs as individual disorders, and to hypothesize about a paradigm that would consider most NCDs (cancer, neurological pathologies, cardiovascular diseases, type II diabetes mellitus, chronic respiratory diseases, osteoarthritis, and osteoporosis, among others) different manifestations of the same process: the cell aging.

Applicability of mesenchymal stem cell-derived exosomes as a cell-free miRNA therapy and epigenetic modifiers for diabetes

Given that exosome nanovesicles constitute various growth factors, miRNAs and lncRNAs, they have implications for epigenetic modifications. Few studies have shown that exosomes from mesenchymal stem cells (MSCs) exhibit therapeutic effects on diabetic complications by substituting miRNAs and regulating histone modifications. Therefore, reversing epigenetic aberrations in diabetes may provide new insight into its treatment. This review discusses the impact of DNA and histone methylations on the development of diabetes and its complications. Further, we talk about miRNAs dysregulated in diabetic conditions and the possibility of utilizing mesenchymal stem cell (MSC) exosomes for the development of miRNA cell-free therapy and epigenetic modifiers in reversing diabetic-induced epigenetic alterations.

LncRNA HCG27 Promotes Glucose Uptake Ability of HUVECs by MiR-378a-3p/MAPK1 Pathway

OBJECTIVE

Gestational diabetes mellitus (GDM) is the most common metabolic disorder during pregnancy. LncRNA HLA complex group 27 (HCG27) plays a crucial role in various metabolic diseases. However, the relationship between lncRNA HCG27 and GDM is not clear. This study aimed to verify a competing endogenous RNA (ceRNA) interaction regulation axis of miR-378a-3p/mitogen-activated protein kinase 1 (MAPK1) regulated by HCG27 in GDM.

METHODS

LncRNA HCG27 and miR-378a-3p were detected by RT-qPCR. The expression of MAPK1 in umbilical vein endothelial cells (HUVECs) was detected by RT-qPCR and that in the placenta by Western blotting. To explore the relationship among lncRNA HCG27, miR-378a-3p, MAPK1 and the glucose uptake ability of HUVECs, vector HCG27, si-HCG27, miR-378a-3p mimic and inhibitor were transfected to achieve overexpression and inhibition of HCG27 or miR-378a-3p. The interaction between miR-378a-3p and lncRNA HCG27 or MAPK1 was confirmed by the dual-luciferase reporter assay. Besides, glucose consumption by HUVECs was detected by the glucose assay kit.

RESULTS

HCG27 expression was significantly decreased in both the placenta and primary umbilical vein endothelial cells, while the expression of miR-378a-3p was significantly increased in GDM tissues, and the expression of MAPK1 was decreased in GDM tissues. This ceRNA interaction regulation axis was proved to affect the glucose uptake function of HUVECs. The transfection of si-HCG27 could significantly reduce the expression of the MAPK1 protein. If the MAPK1 overexpression plasmid was transfected simultaneously with si-HCG27 transfection, the reduced glucose uptake in HUVECs resulting from the decrease in lncRNA HCG27 was reversed. MiR-378a-3p mimic can significantly reduce the mRNA expression of MAPK1 in HUVECs, whereas miR-378a-3p inhibitor can significantly increase the mRNA expression of MAPK1. The inhibition of miR-378a-3p could restore the decreased glucose uptake of HUVECs treated with si-HCG27. Besides, overexpression of lncRNA HCG27 could restore the glucose uptake ability of the palmitic acid-induced insulin resistance model of HUVECs to normal.

CONCLUSION

LncRNA HCG27 promotes glucose uptake of HUVECs by miR-378a-3p/MAPK1 pathway, which may provide potential therapeutic targets for GDM. Besides, the fetal umbilical cord blood and umbilical vein endothelial cells collected from pregnant women with GDM after delivery could be used to detect the presence of adverse molecular markers of metabolic memory, so as to provide guidance for predicting the risk of cardiovascular diseases and health screening of offspring.

Piceatannol promotes neuroprotection by inducing mitophagy and mitobiogenesis in the experimental diabetic peripheral neuropathy and hyperglycemia-induced neurotoxicity

Piceatannol (PCN), a SIRT1 activator, regulates multiple oxidative stress mechanism and has anti-inflammatory potential in various inflammatory conditions. However, its role in Diabetic insulted peripheral neuropathy (DN) remains unknown. Oxidative stress and mitochondrial dysfunction are major contributing factors to DN. Myriad studies have proven that sirtuin1 (SIRT1) stimulation convalesce nerve functions by activating mitochondrial functions like mitochondrial biogenesis and mitophagy. Diabetic neuropathy (DN) was provoked by injecting streptozotocin (STZ) at a dose of 55 mg/kg, i.p to male Sprague Dawley (SD) rats. Mechanical, thermal hyperalgesia was evaluated by using water immersion, Vonfrey Aesthesiometer, and Randall Sellito Calipers. Motor, sensory nerve conduction velocity was measured using Power Lab 4sp system whereas The Laser Doppler system was used to evaluate nerve blood flow. To induce hyperglycemia for the in vitro investigations, high glucose (HG) (30 mM) conditions were applied to Neuro2a cells. At doses of 5 and 10 µM, PCN was examined for its role in SIRT1 and Nrf2 activation. HG-induced N2A cells, reactive oxygen exposure, mitochondrial superoxides and mitochondrial membrane potentials were restored by PCN exposure, and their neurite outgrowth was enhanced. Peroxisome proliferator activated receptor-gamma coactivator-1α (PGC-1α) directed mitochondrial biogenesis was induced by increased SIRT1 activation by piceatannol. SIRT1 activation also enhanced Nrf2-mediated antioxidant signalling. Our study results inferred that PCN administration can counteract the decline in mitochondrial function and antioxidant activity in diabetic rats and HG-exposed N2A cells by increasing the SIRT1 and Nrf2 activities.

Association of nutritional glycaemic indices with global DNA methylation patterns: results from the Moli-sani cohort

BACKGROUND

High dietary glycaemic index (GI) and load (GL) have been associated with increased risk of various cardiometabolic conditions. Among the molecular potential mechanisms underlying this relationship, DNA methylation has been studied, but a direct link between high GI and/or GL of diet and global DNA methylation levels has not been proved yet. We analyzed the associations between GI and GL and global DNA methylation patterns within an Italian population.

RESULTS

Genomic DNA methylation (5mC) and hydroxymethylation (5hmC) levels were measured in 1080 buffy coat samples from participants of the Moli-sani study (mean(SD) = 54.9(11.5) years; 52% women) via ELISA. A 188-item Food Frequency Questionnaire was used to assess food intake and dietary GI and GL for each participant were calculated. Multiple linear regressions were used to investigate the associations between dietary GI and GL and global 5mC and 5hmC levels, as well as the proportion of effect explained by metabolic and inflammatory markers. We found negative associations of GI with both 5mC (β (SE) = - 0.073 (0.027), p = 0.007) and 5hmC (- 0.084 (0.030), p = 0.006), and of GL with 5mC (- 0.14 (0.060), p = 0.014). Circulating biomarkers did not explain the above-mentioned associations. Gender interaction analyses revealed a significant association of the gender-x-GL interaction with 5mC levels, with men showing an inverse association three times as negative as in women (interaction β (SE) = - 0.16 (0.06), p = 0.005).

CONCLUSIONS

Our findings suggest that global DNA methylation and hydroxymethylation patterns represent a biomarker of carbohydrate intake. Based on the differential association of GL with 5mC between men and women, further gender-based separate approaches are warranted.

Epigenetic changes associated with hyperglycaemia exposure in the longitudinal D.E.S.I.R. cohort

AIM

- Understanding DNA methylation dynamics associated with progressive hyperglycaemia exposure could provide early diagnostic biomarkers and an avenue for delaying type 2 diabetes mellitus (T2DM). We aimed to identify DNA methylation changes during a 6-year period associated with early hyperglycaemia exposure using the longitudinal D.E.S.I.R.

COHORT

METHODS

- We selected individuals with progressive hyperglycaemia exposure based on T2DM diagnostic criteria: 27 with long-term exposure, 34 with short-term exposure and 34 normoglycaemic controls. DNA from blood at inclusion and at the 6-year visit was subjected to methylation analysis using 850K methylation-EPIC arrays. A linear mixed model was used to perform an epigenome-wide association study (EWAS) and identify methylated changes associated with hyperglycaemia exposure during a 6-year time-period.

RESULTS

- We did not identify differentially methylated sites that reached false discovery rate (FDR)-significance in our cohort. Based on EWAS, we focused our analysis on methylation sites that had a constant effect during the 6 years across the hyperglycaemia groups compared to controls and found the most statistically significant site was the reported cg19693031 probe (TXNIP). We also performed an EWAS with HbA1c, using the inclusion and the 6-year methylation data and did not identify any FDR-significant CpGs.

CONCLUSIONS

- Our study reveals that DNA methylation changes are not robustly associated with hyperglycaemia exposure or HbA1c during a short-term period, however, our top loci indicate potential interest and should be replicated in larger cohorts.

Genomic DNA Methylation in Diabetic Chronic Complications in Patients With Type 2 Diabetes Mellitus

AIM

To explore the relationship between genomic DNA methylation and diabetic chronic complications.

METHODS

299 patients with type 2 diabetes mellitus (T2DM) hospitalized in the Second Affiliated Hospital of Soochow University were enrolled. We divided the patients into different complications groups and corresponding non-complication groups. Clinical and biochemical parameters were compared between the two groups. The level of genomic DNA methylation in leukocytes was determined by high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

(1) Age, duration of diabetes, creatinine (Cr), blood urea nitrogen (BUN), genomic DNA methylation, 24- hour urine total protein (24-hUTP), and intima-media thickness (IMT) were significantly higher in the carotid plaque (CP) group. Waist-to-hip ratio (WHR), body mass index (BMI), estimated glomerular- filtration rate (eGFR), and albumin (Alb) were significantly lower in the CP group. Gender, age and BMI were the influencing factors of CP. (2) Age, duration, Cr, BUN, urinary microalbumin creatinine ratio (UACR), systolic blood pressure (SBP), TCSS, and 24- hUTP were significantly higher in the diabetic retinopathy (DR) group. eGFR, 2h postprandial C- peptide, and Alb were lower in the DR group. Age, duration, Cr, Alb, SBP, and the presence of DN were the influencing factors of DR. (3) Age, duration, HbA1c, BUN, TCSS, SBP, and IMT(R) were significantly higher in the diabetic nephropathy (DN) group. 2h postprandial C-peptide, and Alb were lower in the DN group. HbA1c, BUN, DR, and HBP were the influencing factors of DN. (4) Age, duration, total cholesterol (TC), low-density lipoprotein (LDL-C), triglyceride (TG), Cr, BUN, uric acid (UA), and SBP were significantly higher in the diabetic peripheral neuropathy (DPN) group. The level of genomic DNA methylation and eGFR were significantly lower in the DPN group. Age, duration, LDL-C, UA, the presence of DR, and the genomic DNA methylation level were the influencing factors for DPN. Incorporating the level of genomic DNA methylation into the prediction model could improve the ability to predict DPN on the basis of conventional risk factors.

CONCLUSION

Low level of genomic DNA methylation is a relatively specific risk factor for DPN in patients with T2DM and not a contributing factor to the other chronic complications.

miR-126 contributes to the epigenetic signature of diabetic vascular smooth muscle and enhances antirestenosis effects of Kv1.3 blockers

Objectives

Restenosis after vessel angioplasty due to dedifferentiation of the vascular smooth muscle cells (VSMCs) limits the success of surgical treatment of vascular occlusions. Type 2 diabetes (T2DM) has a major impact on restenosis, with patients exhibiting more aggressive forms of vascular disease and poorer outcomes after surgery. Kv1.3 channels are critical players in VSMC proliferation. Kv1.3 blockers inhibit VSMCs MEK/ERK signalling and prevent vessel restenosis. We hypothesize that dysregulation of microRNAs (miR) play critical roles in adverse remodelling, contributing to Kv1.3 blockers efficacy in T2DM VSMCs.

Methods and results

We used clinically relevant in vivo models of vascular risk factors (VRF) and vessels and VSMCs from T2DM patients.

Resukts

Human T2DM vessels showed increased remodelling, and changes persisted in culture, with augmented VSMCs migration and proliferation. Moreover, there were downregulation of PI3K/AKT/mTOR and upregulation of MEK/ERK pathways, with increased miR-126 expression. The inhibitory effects of Kv1.3 blockers on remodelling were significantly enhanced in T2DM VSMCs and in VRF model. Finally, miR-126 overexpression confered “diabetic” phenotype to non-T2DM VSMCs by downregulating PI3K/AKT axis.

Conclusions

miR-126 plays crucial roles in T2DM VSMC metabolic memory through activation of MEK/ERK pathway, enhancing the efficacy of Kv1.3 blockers in the prevention of restenosis in T2DM patients.

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Type 2 diabetes (T2DM) vessels show exacerbated remodeling in organ culture and increased Kv1.3 expression.

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The inhibition of vessel remodeling with Kv1.3 blockers is increased in T2DM vessels.

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VSMCs from T2DM patients retain epigenetic changes in primary cultures.

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Upregulation of miR-126 contributes to the metabolic memory of T2DM VSMCs.

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Upregulation of miR-126 potentiates Kv1.3-dependent mechanisms in T2DM VSMCs.

Historical HbA1c Values May Explain the Type 2 Diabetes Legacy Effect: UKPDS 88

OBJECTIVE

Type 2 diabetes all-cause mortality (ACM) and myocardial infarction (MI) glycemic legacy effects have not been explained. We examined their relationships with prior individual HbA1c values and explored the potential impact of instituting earlier, compared with delayed, glucose-lowering therapy.

RESEARCH DESIGN AND METHODS

Twenty-year ACM and MI hazard functions were estimated from diagnosis of type 2 diabetes in 3,802 UK Prospective Diabetes Study participants. Impact of HbA1c values over time was analyzed by weighting them according to their influence on downstream ACM and MI risks.

RESULTS

Hazard ratios for a one percentage unit higher HbA1c for ACM were 1.08 (95% CI 1.07-1.09), 1.18 (1.15-1.21), and 1.36 (1.30-1.42) at 5, 10, and 20 years, respectively, and for MI was 1.13 (1.11-1.15) at 5 years, increasing to 1.31 (1.25-1.36) at 20 years. Imposing a one percentage unit lower HbA1c from diagnosis generated an 18.8% (95% CI 21.1-16.0) ACM risk reduction 10-15 years later, whereas delaying this reduction until 10 years after diagnosis showed a sevenfold lower 2.7% (3.1-2.3) risk reduction. Corresponding MI risk reductions were 19.7% (22.4-16.5) when lowering HbA1c at diagnosis, and threefold lower 6.5% (7.4-5.3%) when imposed 10 years later.

CONCLUSIONS

The glycemic legacy effects seen in type 2 diabetes are explained largely by historical HbA1c values having a greater impact than recent values on clinical outcomes. Early detection of diabetes and intensive glucose control from the time of diagnosis is essential to maximize reduction of the long-term risk of glycemic complications.

Intralesional Infiltrations of Cell-Free Filtrates Derived from Human Diabetic Tissues Delay the Healing Process and Recreate Diabetes Histopathological Changes in Healthy Rats

Lower limb ulcers in type-2 diabetic patients are a frequent complication that tributes to amputation and reduces survival. We hypothesized that diabetic healing impairment and other histopathologic hallmarks are mediated by a T2DM-induced tissue priming/metabolic memory that can be transferred from humans to healthy recipient animals and consequently reproduce diabetic donor’s phenotypes. We examined the effect of human T2DM tissue homogenates injected into non-diabetic rat excisional wounds. Fresh granulation tissue, popliteal artery, and peroneal nerve of patients with T2DM were obtained following amputation. Post-mammoplasty granulation and post-traumatic amputation-tissue of normal subjects acted as controls. The homogenates were intralesionally injected for 6–7 days into rats’ excisional thickness wounds. Infiltration with the different homogenates caused impaired wound closure, inflammation, nerve degeneration, and arterial thickening (all P &lt; 0.01 vs relevant control) resembling histopathology of diabetic donor tissues. Control materials caused marginal inflammation only. Infiltration with glycated bovine albumin provoked inflammation and wound healing delay but did not induce arterial thickening. The reproduction of human diabetic traits in healthy recipient animals through a tissue homogenate support the notion on the existence of tissue metabolic memory-associated and transmissible factors, involved in the pathogenesis of diabetic complications. These may have futuristic clinical implications for medical interventions.

The impact of reactive oxygen species in the development of cardiometabolic disorders: a review

Oxidative stress, an alteration in the balance between reactive oxygen species (ROS) generation and antioxidant buffering capacity, has been implicated in the pathogenesis of cardiometabolic disorders (CMD). At physiological levels, ROS functions as signalling mediators, regulates various physiological functions such as the growth, proliferation, and migration endothelial cells (EC) and smooth muscle cells (SMC); formation and development of new blood vessels; EC and SMC regulated death; vascular tone; host defence; and genomic stability. However, at excessive levels, it causes a deviation in the redox state, mediates the development of CMD. Multiple mechanisms account for the rise in the production of free radicals in the heart. These include mitochondrial dysfunction and uncoupling, increased fatty acid oxidation, exaggerated activity of nicotinamide adenine dinucleotide phosphate oxidase (NOX), reduced antioxidant capacity, and cardiac metabolic memory. The purpose of this study is to discuss the link between oxidative stress and the aetiopathogenesis of CMD and highlight associated mechanisms. Oxidative stress plays a vital role in the development of obesity and dyslipidaemia, insulin resistance and diabetes, hypertension via various mechanisms associated with ROS-led inflammatory response and endothelial dysfunction.

Ethyl ferulate, a lipophilic phenylpropanoid, prevents diabetes-associated renal injury in rats by amelioration of hyperglycemia-induced oxidative stress via activation of nuclear factor erythroid 2-related factor 2

Diabetic nephropathy affects approximately 20%-40% of diabetes patients worldwide and is the leading cause of end-stage renal failure. Oxidative stress has been identified as a major causative factor in the development and progression of diabetic nephropathy; Nuclear factor erythroid 2-related factor 2 (Nrf2) activation protects the body against oxidative stress by induction of antioxidant enzymes. The renoprotective effect of ethyl ferulate was investigated in diabetes-induced renal injury. Ethyl ferulate was administered orally at three doses (50 mg/kg, 75 mg/kg, and 100 mg/kg). Metformin (500 mg/kg, p.o.) was used as a standard. Ethyl ferulate treatment decreased serum advanced glycation end products, glycosylated hemoglobin (HbA1c) levels, renal oxidative stress, tumor necrosis factor-α (TNF-α) level, and kidney hypertrophy index. It restored serum lipid profile, biomarkers of renal function, and mitigated histopathological signs of renal damage. Immunohistochemistry demonstrated higher Nrf2 protein levels in kidney sections of ethyl ferulate-treated rats. These findings suggest that ethyl ferulate ameliorated hyperglycemia-induced oxidative stress by increasing renal Nrf2 levels, thereby preventing diabetes-induced kidney injury. In conclusion, the present study endorses the usefulness of Nrf2 activators, such as ethyl ferulate, as adjuvant therapy for preventing the diabetic nephropathy. PRACTICAL APPLICATIONS: Ethyl ferulate (ethyl-3-hydroxyl-4-methoxycinnamate), a phenylpropanoid, is a naturally occurring ethyl ester of ferulic acid and is widely present in plants and especially grains, such as rice and maize. Our study has highlighted the renoprotective effect of ethyl ferulate in preventing diabetes-associated renal injury. The observed effect of ethyl ferulate is due to amelioration of diabetes-induced oxidative stress and inflammation, by activation of the Nrf2 pathway. These results indicate the potential of ethyl ferulate as a nutraceutical or adjuvant therapy in prevention of diabetic nephropathy.

The nephrological perspective on SGLT-2 inhibitors in type 1 diabetes

Prevalence of type 1 diabetes mellitus (T1DM) is globally continuously increasing. T1DM is accompanied by a high risk of developing cardiovascular and renal comorbidities and is one of the leading causes of end-stage renal disease (ESRD). However, current therapeutic approaches for chronic and/or diabetic kidney disease (CKD/DKD) existed for a long time, and offer room for improvement, particularly in T1DM. In 2019, the European Medicines Agency (EMA) approved a first sodium/glucose co-transporter 2 inhibitor (SGLT-2i) and a first dual SGLT-1/-2i to improve glycaemic control, as an adjunctive treatment to insulin in persons with T1DM and a body mass index ≥27 kg/m². Of note, SGLT-1/2is and SGLT-2is are not approved by the Food and Drug Administration (FDA) as an adjunct treatment in T1DM, nor approved for the treatment of CKD or DKD by EMA and FDA. SGLT is have shown to mediate different renoprotective effects in type 2 diabetes mellitus in corresponding cardiovascular and renal outcome trials. First efficacy trials offer insights into potential positive effects on renal function and kidney disease of SGLTis in T1DM. This review summarizes and discusses latest available data on SGLT inhibition and provides an update on the nephrological perspective on SGLTis, specifically in T1DM.

New insight in molecular mechanisms regulating SIRT6 expression in diabetes: Hyperglycaemia effects on SIRT6 DNA methylation

Conflicting data are reported on the relationship between hyperglycaemia, diabetes and SIRT6 expression. To elucidate hyperglycaemia-induced molecular mechanisms regulating SIRT6 expression, the effect of hyperglycaemia on DNA methylation and SIRT6 expression has been evaluated in human aortic endothelial cells exposed to high glucose. DNA methylation of SIRT6 and any potential clinical implication was also evaluated in type 2 diabetic patients and compared with healthy controls. Endothelial cells exposed to high glucose showed lower methylation levels in SIRT6 promoter and increased SIRT6 and TET2 expression. The high glucose-induced epigenetic changes persisted after 48 h of glucose normalization. Diabetic patients showed lower levels of SIRT6 DNA methylation compared with nondiabetic patients. SIRT6 DNA methylation levels inversely correlated with plasma glucose. Our results firstly demonstrate the involvement of epigenetic mechanisms in regulating SIRT6 expression. Further experiments are necessary to clarify metabolic memory mechanisms driving to diabetic complications and how SIRT6 is potentially involved.

Integrative Computational Approach Revealed Crucial Genes Associated With Different Stages of Diabetic Retinopathy

The increased incidence of diabetic retinopathy (DR) and the legacy effect associated with it has raised a great concern toward the need to find early diagnostic and treatment strategies. Identifying alterations in genes and microRNAs (miRNAs) is one of the most critical steps toward understanding the mechanisms by which a disease progresses, and this can be further used in finding potential diagnostic and prognostic biomarkers and treatment methods. We selected different datasets to identify altered genes and miRNAs. The integrative analysis was employed to find potential candidate genes (differentially expressed and aberrantly methylated genes that are also the target of altered miRNAs) and early genes (genes showing altered expression and methylation pattern during early stage of DR) for DR. We constructed a protein-protein interaction (PPI) network to find hub genes (potential candidate genes showing a greater number of interactions) and modules. Gene ontologies and pathways associated with the identified genes were analyzed to determine their role in DR progression. A total of 271 upregulated-hypomethylated genes, 84 downregulated-hypermethylated genes, 11 upregulated miRNA, and 30 downregulated miRNA specific to DR were identified. 40 potential candidate genes and 9 early genes were also identified. PPI network analysis revealed 7 hub genes (number of interactions >5) and 1 module (score = 5.67). Gene ontology and pathway analysis predicted enrichment of genes in oxidoreductase activity, binding to extracellular matrix, immune responses, leukocyte migration, cell adhesion, PI3K-Akt signaling pathway, ECM receptor interaction, etc., and thus their association with DR pathogenesis. In conclusion, we identified 7 hub genes and 9 early genes that could act as a potential prognostic, diagnostic, or therapeutic target for DR, and a few early genes could also play a role in metabolic memory phenomena.

Effects of "metabolic memory" on erectile function in diabetic men: A retrospective case-control study

OBJECTIVE

This study was performed to explore the effects of metabolic memory on diabetic erectile dysfunction (ED), especially the severity and response to treatment.

METHODS

Through medical records and follow-up by telephone, 67 patients meeting the criteria with a clinical diagnosis of ED and a diabetic history of more than 5 years were enrolled for erectile function analysis. They were divided into a glycemic control group, a glycemic non-control group and a metabolic memory group according to glycemic levels and treatments for diabetes in the past 5 years, and they were treated with phosphodiesterase type 5 (PDE5) inhibitors for 4 weeks. Erectile function and efficacy were assessed by the International Index for Erectile Function (IIEF), the Erection Hardness Score (EHS), and the Sexual Encounter Profile (SEP).

RESULTS

The patients in the glycemic control group performed better in erectile function than those in the other groups. The patients in the glycemic control group received a significantly greater score on both the EHS and the five domains of the IIEF than did the patients in the glycemic non-control group and the metabolic memory group (all P < .001). There were also statistically significant differences favoring the glycemic control group (P < .05) in SEP2 and SEP3 success rates. However, there were no significant differences between the metabolic memory group and the glycemic non-control group in these erectile function assessments (P > .05). Significant negative correlations were seen between HbA1c levels at the time of consultation and the scores on the IIEF-EF and the EHS (Pearson r-values of -0.338 with P = .005 and -0.273 with P = .025, respectively). HbA1c levels at the first diagnosis of diabetes mellitus (DM) were also significantly negatively correlated with scores on the IIEF-EF and the EHS with greater Pearson correlation coefficients (Pearson r-values of -0.478 with P < .001 and -0.392 with P = .001, respectively). Significant improvements on each of the erectile function assessments were observed among diabetic patients with ED, but no significant difference in efficacy was observed between each group.

CONCLUSIONS

The phenomenon of metabolic memory did have a significant influence on ED in men with diabetes, associated with the severity of ED but not the response to medical treatment. Early hyperglycemia exposure would have long-term disadvantageous effects on erectile function in diabetic patients with ED, which would be sustained even after the patients achieve better glycemic control.

PATIENTS SUMMARY

In this report, we looked at the erectile functions of 67 patients with a clinical diagnosis of ED and a diabetic history of more than 5 years. We found that early hyperglycemia exposure would have long-term disadvantageous effects on erectile function in diabetic patients with ED, which would be sustained even after the patients achieve better glycemic control. We further found that the effects were associated with the severity of ED but not the response to medical treatment in men with diabetes.

Pregestational diet transition to normal-fat diet avoids the deterioration of pancreatic β-cell function in male offspring induced by maternal high-fat diet

Novel progress has been made to understand the adverse pathophysiology in the pancreas of offspring exposed to overnutrition in utero. Our study is the first to evaluate whether the adverse effects of maternal overnutrition on offspring β-cell function are reversible or preventable through preconception maternal diet interventions. Herein, offspring mice were exposed in utero to one of the following: maternal normal-fat diet (NF group), maternal high-fat diet (HF group) or maternal diet transition from an HF to NF diet 9 weeks before pregnancy (H9N group). Offspring mice were subjected to postweaning HF diet for 12 weeks. HF offspring, but not H9N, displayed glucose intolerance and insulin resistance. HF male offspring had enlarged islet β-cells with reduced β-cell density, whereas, H9N male offspring did not show these changes. Co-immunofluorescent (Co-IF) staining of glucose transporter 2 (Glut2) and insulin (Ins) revealed significantly more Glut2⁺Ins^- cells, indicative of insulin degranulation, in HF male offspring but not H9N. In addition, Co-IF of insulin and p-H3S10 indicated that β cells of HF male offspring, but not H9N, had proliferation defects likely due to inhibited protein kinase B (AKT) phosphorylation. In summary, our study demonstrates that maternal H9N diet effectively prevents functional deterioration of β cells seen in HF male offspring by avoiding β-cell proliferation defects and degranulation.

VCAM-1, ICAM-1 and selectins in gestational diabetes mellitus and the risk for vascular disorders

Aim: Levels of VCAM-1, ICAM-1 and selectins in gestational diabetes mellitus (GDM) subjects are an indication of endothelial dysfunction predicting the future metabolic consequence via metabolic memory effect. Materials & methods: This cross-sectional study was conducted in 92 pregnant women and serum endothelial cell adhesion molecules were measured using Randox biochip analyzer. Results: Significantly elevated serum level of VCAM-1 was found in GDM subjects and in greater than equal to one parity categorized GDM group when compared with control. The correlation of parity and P-selectin was statistically significant in GDM subjects. Conclusion: Elevated levels of endothelial cell adhesion molecules in GDM women indicate an imbalance in vascular function. Transient hyperglycemia during pregnancy may induce persistent modifications to the memory cells and GDM subjects are more prone to develop future consequences.

Resistance Training Modulates the Humoral Inflammatory (but Not the DNA Methylation) Profile of Diabetic Older Adults Using Metformin

BACKGROUND AND AIM

Inflammatory and methylation imbalances occur in patients with type 2 diabetes mellitus (T2DM). The aim of the present study was to analyze the effect of acute resistance exercise on the inflammatory profile and on DNA methylation of elderly patients with T2DM using metformin.

METHODS

For this purpose, we enrolled 22 male and female older adults (68.2 ± 5.3 years), of whom 13 had controlled T2DM (D) under metformin use and 9 were nondiabetics (ND). All subjects underwent a neuromuscular circuit (8 exercises in 40 min, with each exercise performed in 3 sets of 40 s each and a 20-s interval between repetitions).

RESULTS

The main results indicated a significant difference between groups for baseline interleukin (IL)-10, with a higher concentration in the D group compared to the ND group (p = 0.019). An increase in IL-6 concentration after intervention was observed in group D (p = 0.035). No effect was observed in total DNA methylation within or between groups.

CONCLUSIONS

The resistance training protocol applied in this study modulates the IL-10 and IL-6 concentrations in elderly people with T2DM and under metformin use, possibly as a result of physiological adaptations, with no effect on nondiabetic elderly. No effects on absolute levels of DNA methylation were observed.

Differentiation of diabetic foot ulcer-derived induced pluripotent stem cells reveals distinct cellular and tissue phenotypes

Diabetic foot ulcers (DFUs) are a major complication of diabetes, and there is a critical need to develop novel cell- and tissue-based therapies to treat these chronic wounds. Induced pluripotent stem cells (iPSCs) offer a replenishing source of allogeneic and autologous cell types that may be beneficial to improve DFU wound-healing outcomes. However, the biologic potential of iPSC-derived cells to treat DFUs has not, to our knowledge, been investigated. Toward that goal, we have performed detailed characterization of iPSC-derived fibroblasts from both diabetic and nondiabetic patients. Significantly, gene array and functional analyses reveal that iPSC-derived fibroblasts from both patients with and those without diabetes are more similar to each other than were the primary cells from which they were derived. iPSC-derived fibroblasts showed improved migratory properties in 2-dimensional culture. iPSC-derived fibroblasts from DFUs displayed a unique biochemical composition and morphology when grown as 3-dimensional (3D), self-assembled extracellular matrix tissues, which were distinct from tissues fabricated using the parental DFU fibroblasts from which they were reprogrammed. In vivo transplantation of 3D tissues with iPSC-derived fibroblasts showed they persisted in the wound and facilitated diabetic wound closure compared with primary DFU fibroblasts. Taken together, our findings support the potential application of these iPSC-derived fibroblasts and 3D tissues to improve wound healing.-Kashpur, O., Smith, A., Gerami-Naini, B., Maione, A. G., Calabrese, R., Tellechea, A., Theocharidis, G., Liang, L., Pastar, I., Tomic-Canic, M., Mooney, D., Veves, A., Garlick, J. A. Differentiation of diabetic foot ulcer-derived induced pluripotent stem cells reveals distinct cellular and tissue phenotypes.

Micro-RNAs 518d-3p and 618 Are Upregulated in Individuals With Type 1 Diabetes With Multiple Microvascular Complications

Objective: To compare the serum micro-RNAs (miRNAs) profile of individuals with type 1 diabetes without microvascular complications vs. those with multiple severe microvascular complications, in order to identify epigenetically modulated pathways in these two groups of individuals. Research Design and Methods: A total of 10 subjects were selected among individuals followed in the Diabetes Outpatient Clinic and sorted according to the absence or presence of all microvascular complications. Samples from these participants were used for evaluation of serum miRNA expression profile employing a qRT-PCR assay with hydrolysis probes based on the Taqman Low Density Arrays (TLDA) system. The top six most differentially expressed miRNAs between the aforementioned groups were validated by qRT-PCR in additional 47 type 1 diabetes individuals sorted according to the absence or presence of all microvascular complications and matched for age, sex, degree of metabolic control, diabetes duration, and age at diagnosis. Results: Twenty one out of three hundred and seventy seven miRNAs were upregulated in the group of individuals with all microvascular complications vs. the group without complications. The following miRs were validated: 518-3p, 34a-5p, 126-5p, 425-5p, 618, and 139-5p and logistic regression analyses showed that miRNA-518-3p and miRNA-618 were positively associated with multiple microvascular complications after adjustment for age, sex, diabetes duration, HbA₁c and use of statin, angiotensin-converting enzyme inhibitors and amlodipine. Conclusions: In this cohort of type 1 diabetes individuals, serum miR-518d-3p and miR-618 were upregulated in those with diabetes kidney disease, diabetes retinopathy, peripheral neuropathy, and cardiovascular autonomic neuropathy in comparison to individuals with no microvascular complications.

Association between miRNAs expression and signaling pathways of oxidative stress in diabetic retinopathy

Diabetic retinopathy (DR) is a major cause of vision reduction in diabetic patients. Hyperglycemia is a known instigator for the development of DR, even though the role of oxidative stress pathways in the pathogenesis of DR is established. The studies indicate that microRNAs (miRNAs) are significant to the etiology of DR; changes in miRNAs expression levels may be associated with onset and progression of DR. In addition, miRNAs have emerged as a useful disease marker due to their availability and stability in detecting the severity of DR. The relationship between miRNAs expression levels and oxidative stress pathways has been investigated in several studies. The aim of this study is the examination of function and expression levels of target miRNAs in oxidative stress pathway and pathogenesis of diabetic retinopathy.

A long-term maternal diet intervention is necessary to avoid the obesogenic effect of maternal high-fat diet in the offspring

Although a pre-pregnancy dietary intervention is believed to be able to prevent offspring obesity, research evidence is absent. We hypothesize that a long period of pre-pregnancy maternal diet transition from a high-fat (HF) diet to a normal-fat (NF) diet effectively prevents offspring obesity, and this preventive effect is independent of maternal body weight change. In our study, female mice were either continued on an NF diet (NF group) or an HF diet (HF group) until weaning, or switched from an HF to an NF for 1 week (H1N group), 5 weeks (H5N group) or 9 weeks (H9N group) before pregnancy. After weaning, the offspring were given the HF diet for 12 weeks to promote obesity. The mothers, regardless of which group, did not display maternal body weight change and glucose intolerance either before pregnancy or after weaning. Compared to the HF group, the H1N and H5N, but not the H9N, offspring developed glucose intolerance earlier, with more severely imbalanced glucose homeostasis. These offspring also displayed hepatocyte degeneration and significant adipocyte hypertrophy associated with higher expression of lipogenesis genes. The molecular mechanistic study showed blunted insulin signaling, overactivated adipocyte Akt signaling and hepatic AMPK signaling with enhanced lipogenesis genes in the H1N and H5N versus the NF offspring. However, maternal H9N diets normalized glucose and lipid metabolism of the offspring via resensitized insulin signaling and normalized Akt and AMPK signaling. In summary, we showed that a long-term maternal diet intervention effectively released the intergenerational obesogenic effect of maternal HF diet independent of maternal weight management.

HDAC3 inhibition in diabetic mice may activate Nrf2 preventing diabetes-induced liver damage and FGF21 synthesis and secretion leading to aortic protection

Vascular complications are common pathologies associated with type 1 diabetes. In recent years, histone deacetylation enzyme (HDAC) inhibitors have been shown to be successful in preventing atherosclerosis. To investigate the mechanism for HDAC3 inhibition in preventing diabetic aortic pathologies, male OVE26 type 1 diabetic mice and age-matched wild-type (FVB) mice were given the HDAC3-specific inhibitor RGFP-966 or vehicle for 3 mo. These mice were then euthanized immediately or maintained for an additional 3 mo without treatment. Levels of aortic inflammation and fibrosis and plasma and fibroblast growth factor 21 (FGF21) levels were determined. Because the liver is the major organ for FGF21 synthesis in diabetic animals, the effects of HDAC3 inhibition on hepatic FGF21 synthesis were examined. Additionally, hepatic miR-200a and kelch-like ECH-associated protein 1 (Keap1) expression and nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation were measured. HDAC3 inhibition significantly reduced aortic fibrosis and inflammation in OVE26 mice at both 3 and 6 mo. Plasma FGF21 levels were significantly higher in RGFP-966-treated OVE26 mice compared with vehicle-treated mice at both time points. It also significantly reduced hepatic pathologies associated with diabetes, accompanied by increased FGF21 mRNA and protein expression. HDAC3 inhibition also increased miR-200a expression, reduced Keap1 protein levels, and increased Nrf2 nuclear translocation with an upregulation of antioxidant gene and FGF21 transcription. Our results support a model where HDAC3 inhibition may promote Nrf2 activity by increasing miR-200a expression with a concomitant decrease in Keap1 to preserve hepatic FGF21 synthesis. The preservation of hepatic FGF21 synthesis ultimately leads to a reduction in diabetes-induced aorta pathologies.

Resolvin D1 promotes corneal epithelial wound healing and restoration of mechanical sensation in diabetic mice

PURPOSE

To investigate the effect and mechanism of proresolving lipid mediator resolvin D1 (RvD1) on the corneal epithelium and the restoration of mechanical sensation in diabetic mice.

METHODS

Type 1 diabetes was induced in mice with intraperitoneal streptozocin injections. The healthy and diabetic mice underwent removal of the central corneal epithelium, and then 100 ng/ml RvD1 or its formyl peptide receptor 2 (FPR2) antagonist WRW4 was used to treat the diabetic mice. Regeneration of the corneal epithelium and nerves was observed with sodium fluorescein staining and whole-mount anti-β3-tubulin fluorescence staining. The inflammatory response level was measured with hematoxylin and eosin staining (inflammatory cell infiltration), enzyme-linked immunosorbent assay (tumor necrosis factor alpha and interleukin-1 beta content), myeloperoxidase activity, and fluorescence staining (macrophage content). The reactive oxygen species (ROS) and glutathione (GSH) levels were examined with incubation with fluorescent probes, and oxidative stress-related protein expression levels were evaluated with fluorescence staining and western blotting.

RESULTS

Topical application of RvD1 promoted regeneration of the corneal epithelium in diabetic mice, accompanied by the reactivation of signaling and inflammation resolution related to regeneration of the epithelium. Furthermore, RvD1 directly attenuated the accumulation of ROS and nicotinamide adenine dinucleotide phosphate oxidase 2/4 expression, while RvD1 enhanced GSH synthesis and reactivated the Nrf2-ARE signaling pathway that was impaired in the corneal epithelium in the diabetic mice. More interestingly, topical application of RvD1 promoted regeneration of corneal nerves and completely restored impaired mechanical sensitivity of the cornea in diabetic mice. In addition, the promotion of corneal epithelial wound healing by RvD1 in diabetic mice was abolished by its FPR2 antagonist WRW4.

CONCLUSIONS

Topical application of RvD1 promotes corneal epithelial wound healing and the restoration of mechanical sensation in diabetic mice, which may be related to the lipid mediator's regulation of inflammation resolution, the reactivation of regenerative signaling in the epithelium, and the attenuation of oxidative stress.

NADPH oxidase 4 and endothelial nitric oxide synthase contribute to endothelial dysfunction mediated by histone methylations in metabolic memory

"Metabolic memory" is identified as a phenomenon that transient hyperglycemia can be remembered by vasculature for quite a long term even after reestablishment of normoglycemia. NADPH oxidases (Noxs) and endothelial nitric oxide synthase (eNOS) are important enzymatic sources of reactive oxygen species (ROS) in diabetic vasculature. The aim of this study is to explore the roles of epigenetics and ROS derived from Noxs and eNOS in the metabolic memory. In this study, we demonstrated that vascular ROS was continuously activated in endothelium induced by transient high glucose, as well as sustained vascular endothelial dysfunction. The Nox4 and uncoupled eNOS are the major sources of ROS, while inhibition of Nox4 and eNOS significantly attenuated oxidative stress and almost recovered the endothelial function in metabolic memory. Furthermore, the aberrant histone methylation (H3K4me1, H3K9me2, and H3K9me3) at promoters of Nox4 and eNOS are the main causes for the persistent up-regulation of these two genes. Modifying the histone methylation could reduce the expression levels of Nox4 and eNOS, thus obviously attenuating endothelial dysfunction. These results indicate that histone methylation of Nox4 and eNOS play a key role in metabolic memory and may be the potential intervention targets for metabolic memory.

Stable Oxidative Cytosine Modifications Accumulate in Cardiac Mesenchymal Cells From Type2 Diabetes Patients

Rationale:

Human cardiac mesenchymal cells (CMSCs) are a therapeutically relevant primary cell population. Diabetes mellitus compromises CMSC function as consequence of metabolic alterations and incorporation of stable epigenetic changes.

Objective:

To investigate the role of α-ketoglutarate (αKG) in the epimetabolic control of DNA demethylation in CMSCs.

Methods and Results:

Quantitative global analysis, methylated and hydroxymethylated DNA sequencing, and gene-specific GC methylation detection revealed an accumulation of 5-methylcytosine, 5-hydroxymethylcytosine, and 5-formylcytosine in the genomic DNA of human CMSCs isolated from diabetic donors. Whole heart genomic DNA analysis revealed iterative oxidative cytosine modification accumulation in mice exposed to high-fat diet (HFD), injected with streptozotocin, or both in combination (streptozotocin/HFD). In this context, untargeted and targeted metabolomics indicated an intracellular reduction of αKG synthesis in diabetic CMSCs and in the whole heart of HFD mice. This observation was paralleled by a compromised TDG (thymine DNA glycosylase) and TET1 (ten–eleven translocation protein 1) association and function with TET1 relocating out of the nucleus. Molecular dynamics and mutational analyses showed that αKG binds TDG on Arg275 providing an enzymatic allosteric activation. As a consequence, the enzyme significantly increased its capacity to remove G/T nucleotide mismatches or 5-formylcytosine. Accordingly, an exogenous source of αKG restored the DNA demethylation cycle by promoting TDG function, TET1 nuclear localization, and TET/TDG association. TDG inactivation by CRISPR/Cas9 knockout or TET/TDG siRNA knockdown induced 5-formylcytosine accumulation, thus partially mimicking the diabetic epigenetic landscape in cells of nondiabetic origin. The novel compound (S)-2-[(2,6-dichlorobenzoyl)amino]succinic acid (AA6), identified as an inhibitor of αKG dehydrogenase, increased the αKG level in diabetic CMSCs and in the heart of HFD and streptozotocin mice eliciting, in HFD, DNA demethylation, glucose uptake, and insulin response.

Conclusions:

Restoring the epimetabolic control of DNA demethylation cycle promises beneficial effects on cells compromised by environmental metabolic changes.

Effect of diabetes status and hyperglycemia on global DNA methylation and hydroxymethylation

Type 2 diabetes mellitus (T2DM) is characterized by oxidative stress that could lead to chronic micro- and macrovascular complications. We hypothesized that some of the target organ damage is mediated by oxidative alterations in epigenetic mechanisms involving DNA methylation (5mC) and DNA hydroxymethylation (5hmC). We analyzed global DNA methylation and hydroxymethylation in peripheral blood cells in well-controlled and poorly controlled patients with T2DM and compared them with healthy controls. We also analyzed microarrays of DNA methylation and gene expression of other important tissues in the context of diabetes from the GEO database repository and then compared these results with our experimental gene expression data. DNA methylation and, more importantly, DNA hydroxymethylation levels were increased in poorly controlled patients compared to well-controlled and healthy individuals. Both 5mC and 5hmC measurements were correlated with the percentage of glycated hemoglobin, indicating a direct impact of hyperglycemia on changes over the epigenome. The analysis of methylation microarrays was concordant, and 5mC levels were increased in the peripheral blood of T2DM patients. However, the DNA methylation levels were the opposite of those in other tissues, such as the pancreas, adipose tissue and skeletal muscle. We hypothesize that a process of DNA oxidation associated with hyperglycemia may explain the DNA demethylation in which the activity of ten-eleven translocation (TET) proteins is not sufficient to complete the process. High levels of glucose lead to cellular oxidation, which triggers the process of DNA demethylation aided by TET enzymes, resulting in epigenetic dysregulation of the damaged tissues.

Oxidative Stress and Cardiovascular Risk: Obesity, Diabetes, Smoking, and Pollution: Part 3 of a 3-Part Series

Oxidative stress occurs whenever the release of reactive oxygen species (ROS) exceeds endogenous antioxidant capacity. In this paper, we review the specific role of several cardiovascular risk factors in promoting oxidative stress: diabetes, obesity, smoking, and excessive pollution. Specifically, the risk of developing heart failure is higher in patients with diabetes or obesity, even with optimal medical treatment, and the increased release of ROS from cardiac mitochondria and other sources likely contributes to the development of cardiac dysfunction in this setting. Here, we explore the role of different ROS sources arising in obesity and diabetes, and the effect of excessive ROS production on the development of cardiac lipotoxicity. In parallel, contaminants in the air that we breathe pose a significant threat to human health. This paper provides an overview of cigarette smoke and urban air pollution, considering how their composition and biological effects have detrimental effects on cardiovascular health.

Inhibition of HDAC3 prevents diabetic cardiomyopathy in OVE26 mice via epigenetic regulation of DUSP5-ERK1/2 pathway

Inhibition of total histone deacetylases (HDACs) was phenomenally associated with the prevention of diabetic cardiomyopathy (DCM). However, which specific HDAC plays the key role in DCM remains unclear. The present study was designed to determine whether DCM can be prevented by specific inhibition of HDAC3 and to elucidate the mechanisms by which inhibition of HDAC3 prevents DCM. Type 1 diabetes OVE26 and age-matched wild-type (WT) mice were given the selective HDAC3 inhibitor RGFP966 or vehicle for 3 months. These mice were then killed immediately or 3 months later for cardiac function and pathological examination. HDAC3 activity was significantly increased in the heart of diabetic mice. Administration of RGFP966 significantly prevented DCM, as evidenced by improved diabetes-induced cardiac dysfunction, hypertrophy, and fibrosis, along with diminished cardiac oxidative stress, inflammation, and insulin resistance, not only in the mice killed immediately or 3 months later following the 3-month treatment. Furthermore, phosphorylated extracellular signal-regulated kinases (ERK) 1/2, a well-known initiator of cardiac hypertrophy, was significantly increased, while dual specificity phosphatase 5 (DUSP5), an ERK1/2 nuclear phosphatase, was substantially decreased in diabetic hearts. Both of these changes were prevented by RGFP966. Chromatin immunoprecipitation (ChIP) assay showed that HDAC3 inhibition elevated histone H3 acetylation on the DUSP5 gene promoter at both two time points. These findings suggest that diabetes-activated HDAC3 inhibits DUSP5 expression through deacetylating histone H3 on the primer region of DUSP5 gene, leading to the derepression of ERK1/2 and the initiation of DCM. The present study indicates the potential application of HDAC3 inhibitor for the prevention of DCM.

Transcription Factor CREM Mediates High Glucose Response in Cardiomyocytes and in a Male Mouse Model of Prolonged Hyperglycemia

This study aims at investigating the epigenetic landscape of cardiomyocytes exposed to elevated glucose levels. High glucose (30 mM) for 72 hours determined some epigenetic changes in mouse HL-1 and rat differentiated H9C2 cardiomyocytes including upregulation of class I and III histone deacetylase protein levels and activity, inhibition of histone acetylase p300 activity, increase in histone H3 lysine 27 trimethylation, and reduction in H3 lysine 9 acetylation. Gene expression analysis focused on cardiotoxicity revealed that high glucose induced markers associated with tissue damage, fibrosis, and cardiac remodeling such as Nexilin (NEXN), versican, cyclic adenosine 5'-monophosphate-responsive element modulator (CREM), and adrenoceptor α2A (ADRA2). Notably, the transcription factor CREM was found to be important in the regulation of cardiotoxicity-associated genes as assessed by specific small interfering RNA and chromatin immunoprecipitation experiments. In CD1 mice, made hyperglycemic by streptozotoicin (STZ) injection, cardiac structural alterations were evident at 6 months after STZ treatment and were associated with a significant increase of H3 lysine 27 trimethylation and reduction of H3 lysine 9 acetylation. Consistently, NEXN, CREM, and ADRA2 expression was significantly induced at the RNA and protein levels. Confocal microscopy analysis of NEXN localization showed this protein irregularly distributed along the sarcomeres in the heart of hyperglycemic mice. This evidence suggested a structural alteration of cardiac Z-disk with potential consequences on contractility. In conclusion, high glucose may alter the epigenetic landscape of cardiac cells. Sildenafil, restoring guanosine 3', 5'-cyclic monophosphate levels, counteracted the increase of CREM and NEXN, providing a protective effect in the presence of hyperglycemia.

DNA methylation and its role in the pathogenesis of diabetes

Although the factors responsible for the recent increase in the prevalence of diabetes worldwide are not entirely known, the morbidity associated with this disease results in substantial health and economic burden on society. Epigenetic modifications, including DNA methylation have been identified as one mechanism by which the environment interacts with the genome and there is evidence that alterations in DNA methylation may contribute to the increased prevalence of both type 1 and type 2 diabetes. This review provides a summary of DNA methylation and its role in gene regulation, and includes descriptions of various techniques to measure site-specific and genome-wide DNA methylation changes. In addition, we review current literature highlighting the complex relationship between DNA methylation, gene expression, and the development of diabetes and related complications. In studies where both DNA methylation and gene expression changes were reported, DNA methylation status had a strong inverse correlation with gene expression, suggesting that this interaction may be a potential future therapeutic target. We highlight the emerging use of genome-wide DNA methylation profiles as a biomarker to predict patients at risk of developing diabetes or specific complications of diabetes. The development of a predictive model that incorporates both genetic sequencing and DNA methylation data may be an effective diagnostic approach for all types of diabetes and could lead to additional innovative therapies.

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.

Glycation and cardiovascular disease in diabetes: A perspective on the concept of metabolic memory

Epidemiological studies have suggested that cumulative diabetic exposure, namely prolonged exposure to chronic hyperglycemia, contributes to the increased risk of cardiovascular disease (CVD) in diabetes. The formation and accumulation of advanced glycation end-products (AGEs) have been known to progress under hyperglycemic conditions. Because AGEs-modified collagens are hardly degraded and remain in diabetic vessels, kidneys and the heart for a long time, even after glycemic control has been achieved, AGEs could become a marker reflecting cumulative diabetic exposure. Furthermore, there is a growing body of evidence that an interaction between AGEs and the receptor for AGEs (RAGE) plays a role in the pathogenesis of CVD. In addition, AGEs induce the expression of RAGE, thus leading to sustained activation of the AGEs-RAGE axis in diabetes. Herein we review the pathological role of the AGEs-RAGE axis in CVD, focusing particularly on the phenomenon of metabolic memory, and discuss the potential clinical usefulness of measuring circulating and tissue levels of AGEs accumulation to evaluate diabetic macrovascular complications.

Dynamin-related protein 1 mediates low glucose-induced endothelial dysfunction in human arterioles

Intensive glycemic regulation has resulted in an increased incidence of hypoglycemia. Hypoglycemic burden correlates with adverse cardiovascular complications and contributes acutely and chronically to endothelial dysfunction. Prior data indicate that mitochondrial dysfunction contributes to hypoglycemia-induced endothelial dysfunction, but the mechanisms behind this linkage remain unknown. We attempt to determine whether clinically relevant low-glucose (LG) exposures acutely induce endothelial dysfunction through activation of the mitochondrial fission process. Characterization of mitochondrial morphology was carried out in cultured endothelial cells by using confocal microscopy. Isolated human arterioles were used to explore the effect LG-induced mitochondrial fission has on the formation of detrimental reactive oxygen species (ROS), bioavailability of nitric oxide (NO), and endothelial-dependent vascular relaxation. Fluorescence microscopy was employed to visualize changes in mitochondrial ROS and NO levels and videomicroscopy applied to measure vasodilation response. Pharmacological disruption of the profission protein Drp1 with Mdivi-1 during LG exposure reduced mitochondrial fragmentation among vascular endothelial cells (LG: 0.469; LG+Mdivi-1: 0.276; P = 0.003), prevented formation of vascular ROS (LG: 2.036; LG+Mdivi-1: 1.774; P = 0.005), increased the presence of NO (LG: 1.352; LG+Mdivi-1: 1.502; P = 0.048), and improved vascular dilation response to acetylcholine (LG: 31.6%; LG+Mdivi-1; 78.5% at maximum dose; P < 0.001). Additionally, decreased expression of Drp1 via siRNA knockdown during LG conditions also improved vascular relaxation. Exposure to LG imparts endothelial dysfunction coupled with altered mitochondrial phenotypes among isolated human arterioles. Disruption of Drp1 and subsequent mitochondrial fragmentation events prevents impaired vascular dilation, restores mitochondrial phenotype, and implicates mitochondrial fission as a primary mediator of LG-induced endothelial dysfunction.NEW & NOTEWORTHY Acute low-glucose exposure induces mitochondrial fragmentation in endothelial cells via Drp1 and is associated with impaired endothelial function in human arterioles. Targeting of Drp1 prevents fragmentation, improves vasofunction, and may provide a therapeutic target for improving cardiovascular complications among diabetics.Listen to this article's corresponding podcast @ http://ajpheart.podbean.com/e/mitochondrial-dynamics-impact-endothelial-function/.

Persistent Insulin Resistance in Podocytes Caused by Epigenetic Changes of SHP-1 in Diabetes

Poor glycemic control profoundly affects protein expression and the cell signaling action that contributes to glycemic memory and irreversible progression of diabetic nephropathy (DN). We demonstrate that SHP-1 is elevated in podocytes of diabetic mice, causing insulin unresponsiveness and DN. Thus, sustained SHP-1 expression caused by hyperglycemia despite systemic glucose normalization could contribute to the glycemic memory effect in DN. Microalbuminuria, glomerular filtration rate, mesangial cell expansion, and collagen type IV and transforming growth factor-β expression were significantly increased in diabetic Ins2^+/C96Y mice compared with nondiabetic Ins2^+/+ mice and remained elevated despite glucose normalization with insulin implants. A persistent increase of SHP-1 expression in podocytes despite normalization of systemic glucose levels was associated with sustained inhibition of the insulin signaling pathways. In cultured podocytes, high glucose levels increased mRNA, protein expression, and phosphatase activity of SHP-1, which remained elevated despite glucose concentration returning to normal, causing persistent insulin receptor-β inhibition. Histone posttranslational modification analysis showed that the promoter region of SHP-1 was enriched with H3K4me1 and H3K9/14ac in diabetic glomeruli and podocytes, which remained elevated despite glucose level normalization. Hyperglycemia induces SHP-1 promoter epigenetic modifications, causing its persistent expression and activity and leading to insulin resistance, podocyte dysfunction, and DN.

The development of a charcot foot after significant weight loss in people with diabetes: three cautionary tales

Medication to aid weight loss and weight loss surgery are becoming more commonly available for people with diabetes. As a result of profound weight loss, diabetes may go into remission and many biochemical and physical parameters improve. However, some of the end organ damage associated with diabetes may not improve, peripheral neuropathy being an example. We present three cases in people with diabetes and pre-existing peripheral neuropathy who had lost significant weight. They became more mobile and developed a Charcot foot despite their diabetes improving significantly. People who have lost significant weight should continue to monitor their feet because the risks of foot disease remain even if diabetes goes into remission.

Clinical implications of oxidative stress and potential role of natural antioxidants in diabetic vascular complications

AIMS

The possible link between hyperglycaemia-induced oxidative stress (OxS) and diabetic complications is suggested by many in vitro studies. However, not much attention has been paid to the clinical evidence supporting this hypothesis, as well as to their possible therapeutic implications.

DATA SYNTHESIS

Some prospective studies show a direct correlation between an increase in OxS biomarkers and the appearance of diabetes complications. This is consistent with the evidence that any acute increase of glycaemia, particularly post-prandial, and hypoglycaemia causes endothelial dysfunction and inflammation, through the generation of an OxS. However, the detection of free radicals is difficult as they are highly reactive molecules with a short half-life. Instead, the metabolites of OxS are measured. Interventional trials with supplemented antioxidants have failed to show any beneficial effects. Conversely, natural foods show very promising results.

CONCLUSIONS

The "new antioxidant" approach includes the possibility of controlling free radical production and increasing intracellular antioxidant defence, a concept different from the old one, when antioxidant activities implied scavenging the free radicals already produced. A synergistic action in this respect could convincingly be obtained with a balanced 'Mediterranean Diet' (MedD) type. Early intensive glucose control is still the best strategy to avoid OxS and its associated diabetes complications.

Doxorubicin cardiotoxicity and target cells: a broader perspective

The cardiotoxicity of doxorubicin is becoming an interdisciplinary point of interest given a growing population of cancer survivors. The complex and not completely understood pathogenesis of this complication makes difficult to design successful preventive or curative measures. Although cardiomyocyte has been considered a classical cellular target, other cells including various types of undifferentiated cells are involved in myocardial homeostasis. Such perspective may shed light on previously unrecognized aspects of cardiotoxicity and promote new experimental and clinical cardioprotective strategies. In this review, different cellular targets of doxorubicin are discussed with the focus on cardiac progenitor cells, oxidative stress, DNA damage, senescence and apoptosis all of which contribute to their compromised functional properties.