Dysfunction In Type 2 Diabetes Mellitus Research Articles

Association between glycemic control and morning blood surge with vascular endothelial dysfunction in type 2 diabetes mellitus patients.

Objective:Morning blood pressure surge (MBPS) is an independent predictor of cardiovascular events. However, little is known about the association between glycemic control and MBPS, and its effect on vascular injury in patients with type 2 diabetes mellitus (T2DM). The current study examined the association between glycemic control and MBPS and the involvement of MBPS in the development of vascular dysfunction in T2DM patients.Materials and Methods:One hundred and twenty-two consecutive T2DM outpatients from the Department of Cardiology and Endocrinology were enrolled in this study. We did MBPS in T2DM patients, 85 (male) (69.7%) patients and 37 (female) patients (30.3%); mean age 60.1 ± 9.39; (n = 122) using 24 h ambulatory blood pressure monitoring and assessed vascular function by brachial artery flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD).Results:The correlation between MBPS and various clinical variables were examined by single regression analysis in all subjects. MBPS showed significant and positive correlation with pulse rate (P = 0.01), fasting blood sugar (P = 0.002), and postprandial blood sugar (P = 0.05). To further confirm the association of insulin resistance (IR) with MBPS in T2DM patients, we examined the correlation between homeostasis model assessment-IR (HOMA-IR), an established marker of IR and MBPS in diabetic (DM) patients who were not taking insulin no significant association with MBPS in T2DM patients (P = 0.41), angiotensin-converting enzyme/angiotensin receptor blocker (P = 0.07). We examined the relationship between MBPS and vascular injury by measuring endothelium-dependent FMD and endothelium-independent NMD in T2DM patients. Among the various traditional risk factors for atherosclerosis such as DM duration (P = 0.04), platelet reactivity (P = 0.04) and morning surge (P = 0.002) emerged as significant factors. HOMA-IR was a negative correlation with FMD.Conclusions:The current study demonstrated that poor glycemic control and IR have predictive value for the occurrence of MBPS in T2DM patients, which might be significantly associated with endothelial dysfunction.

EVALUATION OF AUTONOMIC DYSFUNCTION BY HEART RATE VARIABILITY ANALYSIS IN TYPE 2 DIABETES MELLITUS

ABSTRACTObjective: Cardiac autonomic neuropathy (CAN) is a severe and common, yet highly underdiagnosed, complication of Type 2 diabetes mellitus(T2DM). Subclinical CAN may have reduced heart rate variability (HRV) but normal Ewing battery test. This study was performed to evaluate theimportance of 5 minutes HRV for the detection of autonomic dysfunction in T2DM without (CAN-T2DM).Methods: This cross-sectional observational study was conducted at the Department of Physiology, Bangabandhu Sheikh Mujib Medical University(BSMMU) on 30 recently diagnosed T2DM (RT2DM) and 54 long-term CAN-male T2DM patients (LT2DM), aged 45-55 years, from the EndocrinologyOut Patient Department of BSMMU, Dhaka. 30 age and body mass index matched apparently healthy male subjects were control. Ewing battery testwas used to rule out CAN positive T2DM. HRV data were recorded by a polyrite-D and analyzed by software. HRV was assessed by time domainmethod. For statistical analysis, ANOVA and unpaired t-test were used.Results: Mean RR, standard deviation of NN intervals (SDNN) (p<0.05), and root mean square of the successive differences (RMSSD) were significantly(p<0.001) lower, and mean HR and SDNN/RMSSD were (p<0.001) significantly higher in LT2DM compared to RT2DM and control. In addition, SDNNwas also significantly (p<0.05) lower in RT2DM than that of control.Conclusions: Results conclude that autonomic dysfunction may occur in both LT2DM and RT2DM patients without neuropathy and 5 minutes HRVtest is an important tool for detecting subclinical CAN.Keywords: Type 2 diabetes mellitus, Cardiac autonomic neuropathy, Heart rate variability.

Abstract 15814: Novel Protective Mechanism of Cu Transporter ATP7A for Extracellular SOD Against Endothelial Dysfunction in Type2 Diabetes Vascular Complications

Endothelial dysfunction induced by oxidative stress is the major vascular complication in diabetes mellitus (DM). Extracellular SOD (ecSOD), a secretory copper (Cu) enzyme, preserves endothelial function by scavenging extracellular superoxide, and its full activity requires Cu transporter ATP7A. We reported that reduced ATP7A-ecSOD pathway in vascular smooth muscle cells (VSMCs) is involved in endothelial dysfunction in type1 DM with hypoinsulinemia, but its role and mechanism in type2 DM with impaired insulin-Akt signaling is entirely unknown. Here we show that in VSMC, insulin increases ATP7A protein expression (1.8 fold) without affecting transcription by reducing ATP7A ubiquitination in a PI3K/Akt dependent manner. In organoid culture of mouse aorta, insulin increases ecSOD specific activity (47%) and ATP7A expression (1.9-fold). Insulin stimulation (2 hrs) promotes ATP7A translocation from TGN to caveolin (Cav) enriched lipid raft (C/LR) where it binds to ecSOD in PI3K/Akt dependent manner, reflecting Cu delivery to ecSOD through ATP7A at C/LR. Mechanistically, insulin increases pAkt binding to ATP7A to induce pSer-ATP7A, which is required for ATP7A translocation to C/LR. Mass spectrometry analysis identified Akt phosphorylation site of ATP7A at S1424/S1432/S1466. Of note, vascular ATP7A protein expression, ecSOD specific activity and endothelial function are impaired in Cav1 KO or Akt2 KO or ATP7Amut mice, but not Akt1 KO mice, suggesting the importance of Akt2-mediated ATP7A protein stabilization and its translocation to C/LR for ecSOD activation. Moreover, in aorta or VSMCs of high fat diet-induced type2 DM mice with impaired insulin-Akt pathway, ATP7A expression (57%) and ecSOD specific activity (53%), but not Cu/Zn SOD, are decreased. Acetylcholine-induced vasorelaxation is significantly impaired in resistant vessels of type2 DM mice, which is rescued in ATP7A-Tg/Type2 DM mice. In summary, insulin-Akt dependent ATP7A protein stabilization and translocation to C/LR promotes ecSOD activation, which prevents endothelial dysfunction in type2 DM. Thus, enhancing Akt2-ATP7A-ecSOD axis is potential therapeutic strategy for protecting against endothelial dysfunction in diabetes vascular complications.

Hippocampal insulin resistance and cognitive dysfunction.

Clinical studies suggest a link between type 2 diabetes mellitus (T2DM) and insulin resistance (IR) and cognitive dysfunction, but there are significant gaps in our knowledge of the mechanisms underlying this relationship. Animal models of IR help to bridge these gaps and point to hippocampal IR as a potential mediator of cognitive dysfunction in T2DM, as well as in Alzheimer disease (AD). This Review highlights these observations and discusses intervention studies which suggest that the restoration of insulin activity in the hippocampus may be an effective strategy to alleviate the cognitive decline associated with T2DM and AD.

Prevalence of thyroid dysfunction in patients with Type 2 diabetes mellitus and its correlation with insulin resistance and serum markers for autoimmune thyroiditis

Background: The term “THYROID DIABETES” was coined in early literature to depict the influence of thyroid hormone excess in deterioration of glucose control. Although autoimmune thyroid disease is more prevalent in Type1 Diabetes mellitus as a result of their common origin, the prevalence of hypothyroidism and hyperthyroidism is supposed to be similar to that of general population in patient with type2 DM. The purpose of the study was to evaluate the prevalence of thyroid dysfunction in patients with type2 diabetes mellitus and to correlate thyroid abnormalities with insulin resistance and serum markers for autoimmune thyroiditis. Methods: 120 cases of type2 diabetes mellitus patients satisfying WHO criteria without pre-existing thyroid disease were included in the study. Thyroid function test, fasting serum insulin was done.HOMA-IR & HOMA-B (HOMA-Homeostatic model assessment) was calculated. Serum antithyroid peroxidase anibody (anti-TPO) and antithyroglobulin antibodies (anti-TG) and ANA were done. Results: Prevalence of thyroid dysfunction in type2 diabetes mellitus was 28.33% according to our study, which included overt hypothyroidism (15%), subclinical hypothyroidism (8.33%), secondary hypothyroidism (0.83%), overt hyperthyroidism (1.67%) and subclinical hyperthyroidism (2.5%). Anti TPO and anti TG antibodies were elevated in 62.07% cases of hypothyroidism, 40% cases of hyperthyroidism and 6.9% euthyroid cases of type2 DM. Anti TPO and antiTG antibodies were significantly raised in type2DM patient with hypothroidism than that of euthyroid (p value<0.0001). Compared to euthyroid diabetics, hypothyroid cases had lower values of insulin resistance markers like fasting insulin, HOMA-IR and HOMA-B. Hyperthyoid cases had higher values. Conclusion: Hyperthyroid diabetics have higher insulin resistance as fasting insulin, HOMA-IR, HOMA-B showed negative correlation with TSH. (p value<0.05).DOI: http://dx.doi.org/10.3126/ajms.v6i6.12603 Asian Journal of Medical Sciences Vol.6(6) 2015 33-38

Identification of a definite diabetic cardiomyopathy in type 2 diabetes by comprehensive echocardiographic evaluation: A cross‐sectional comparison with non‐diabetic weight‐matched controls

Subclinical left ventricular (LV) dysfunction is prevalent in type 2 diabetes (T2DM). As obesity has been proposed as one causal factor in the disease process, this could bias the reported prevalences. We wanted to characterize echocardiographic LV dysfunction in obese T2DM subjects as compared to non-diabetic obese controls. One hundred patients with T2DM without clinical signs of heart failure (29% females, mean ± SD age 58.4 ± 10.5 years, body mass index (BMI) 30.1 ± 5.5 kg/m(2), blood pressure (BP) 141 ± 18/83 ± 9 mmHg) and 100 non-diabetic controls (29% females) matched for age (58.6 ± 10.5 years), BMI (29.8 ± 4.0 kg/m(2) and systolic BP (140 ± 14 mmHg) underwent echocardiography and color tissue Doppler imaging (TDI). Diastolic function was evaluated with conventional Doppler recordings and early (e') and late (a') myocardial velocities. The ratio between early transmitral filling (E) and the corresponding myocardial tissue velocity (e') served as an index of LV filling pressure. T2DM patients had more concentric hypertrophy with a relative wall thickness of 0.42 ± 0.07 vs controls 0.38 ± 0.07, P < 0.001. The T2DM group had signs of diastolic dysfunction with lower E/A ratio (0.91 ± 0.27 vs. 1.12 ± 0.38, P < 0.001), deceleration time (195 ± 49 vs 242 ± 72 ms, P < 0.001), e' (5.7 ± 2.0 vs. 6.6 ± 1.8 cm/s, P = 0.001), and a' (6.5 ± 2.0 vs. 7.6 ± 1.5 cm/s, P < 0.001) compared to the controls, and higher E/e' (13.3 ± 4.7 vs. 11.1 ± 3.5, P < 0.001). Thus, there were indications of pseudo normalization and increased filling pressure in the T2DM group, whereas the controls had evidence for relaxation abnormalities without elevated filling pressure. Compared to a non-diabetic obese group, more advanced subclinical impairment of diastolic function was seen in T2DM.

Geniposide protects pancreatic INS-1E β cells from hIAPP-induced cell damage: potential involvement of insulin degrading-enzyme.

Islet amyloid deposition is increasingly seen as a pathogenic feature of type 2 diabetes mellitus (T2DM), with the deposits containing the unique amyloidogenic peptide islet amyloid polypeptide (IAPP, also known as amylin). The fibril precursors of IAPP contribute to its cytotoxicity on pancreatic β cells and be important in causing β-cell dysfunction in T2DM. However, the development of effective this study, inhibitors against the toxicity of IAPP has been extremely challenging. We have found that pre-incubation with geniposide dose-dependently prevented human IAPP (hIAPP)-induced cell damage in INS-1E cells, and bacitracin, an inhibitor of IDE activity, prevented significantly the protective effects of geniposide in pancreatic INS-1E cells significantly. Geniposide induced the expression of insulin-degrading enzyme (IDE), a key degrading protein of hIAPP, but had no significant effect on the aggregation of hIAPP. These findings indicate that geniposide prevents hIAPP-induced cytotoxicity in INS-1E cells involving upregulation of IDE expression.

The compensatory enrichment of sphingosine -1- phosphate harbored on glycated high-density lipoprotein restores endothelial protective function in type 2 diabetes mellitus.

BackgroundGlycation of high-density lipoprotein (HDL) decreases its ability to induce cyclooxygenase-2 (COX-2) expression and prostacyclin I-2 (PGI-2) release in endothelial cells. Whether lipid content of HDL, especially sphingosine-1-phosphate (S1P), plays any specific role in restoring the protective function of HDL in type 2 diabetes mellitus (T2DM) is still unknown.Methods and resultsImmunochemical techniques demonstrated that glycated HDL loses its protective function of regulating COX-2 expression compared with diabetic HDL. We proved that the lipid content, especially phospholipid content differed between diabetic HDL and glycated HDL. Levels of HDL-c-bound S1P were increased in T2DM compared with control subjects as detected by UPLC-MS/MS (HDL-c-bound S1P in control subjects vs. T2DM: 309.1 ± 13.71 pmol/mg vs. 382.1 ± 24.45 pmol/mg, P < 0.05). Additionally, mRNA levels of S1P lyase enzymes and S1P phosphatase 1/2 were decreased in peripheral blood by real-time PCR. Antagonist of S1P receptor 1 and 3 (S1PR1/3) diminished the functional difference between apoHDL&PL (HDL containing the protein components and phospholipids) and diabetic apoHDL&PL (diabetic HDL containing the protein components and phospholipids). With different doses of S1P reconstituted on glycated HDL, its function in inducing the COX-2 expression was restored to the same level as diabetic HDL. The mechanism of S1P reconstituted HDL (rHDL) in the process of regulating COX-2 expression involved the phosphorylation of ERK/MAPK-CREB signal pathway.Conclusion/SignificanceS1P harbored on HDL is the main factor which restores its protective function in endothelial cells in T2DM. S1P and its receptors are potential therapeutic targets in ameliorating the vascular dysfunction in T2DM.

Abstract 230: Evaluation of Hyperglycemia-Driven Alterations on Vascular Endothelial Function

Type 2 diabetes mellitus (T2DM) afflicts ~25 million people in the United States and hyperglycemia is a major causative factor contributing to vascular dysfunction among this population. This study evaluated the hypothesis that hyperglycemia-induced changes in endothelial glycoproteome leads to alterations of important homeostatic signaling pathways that result in vascular dysfunction. Utilizing targeted glycoprotein enrichment coupled with tandem mass spectrometry for protein identification and quantification, the cell surface glycoproteins were assessed from rat microvascular endothelial cells (RMVECs) cultured in ‘normal’ glucose (5 mM) or ‘high’ glucose (25 mM). Altogether, 273 N-glycosylation modified proteins were identified; 65 proteins uniquely N-glycosylated and 22 proteins significantly increased in N-glycosylation (p&lt;0.05) from ‘high’ glucose RMVECs. Additionally, 499 O-glycoproteins were identified; 78 proteins uniquely O-glycosylated and 65 proteins significantly increased in O-glycoslyation (p&lt;0.05) from ‘high’ glucose RMVECs. The type-1A angiotensin II receptor (AT1; p=0.029), along with numerous cell adhesion molecules, had increased N-glycosylation in ‘high’ glucose RMVECs. Numerous ion channels important for vascular function and the 5-HT2A serotonin receptor (p=5.3e-28), recently shown to contribute to vascular dysfunction in T2DM, had elevated O-glycosylation in ‘high’ glucose RMVECs. In order to evaluate these targets, functional assays were developed to measure endothelial and vascular function. Immobilization assays in a parallel plate flow chamber (PPFC) indicated that ‘high’ glucose significantly increased RMVEC adhesion to gelatin substrate under laminar flow (p&lt;0.05). In addition, incubation of RMVECs under ‘high’ glucose conditions increased the adherence of healthy platelets to RMVECs, suggesting the importance of adhesion protein glycosylation in endothelial dysfunction. Finally, studies in human subcutaneous arterioles demonstrated that acute exposure to ‘high’ glucose impaired acetylcholine-induced vasodilation. Utilizing these assays, differentially hyperglycemia-regulated targets will be functionally evaluated for potential therapeutic intervention.

Modulation of Skeletal Muscle Performance and SERCA by Exercise and Adiponectin Gene Therapy in Insulin-Resistant Rat

This study addresses the potential application of adiponectin gene therapy and exercise in protection against skeletal muscle dysfunction in type 2 diabetes mellitus (T2DM) while focusing on the role of sarco and endoplasmic reticulum Ca(+2) ATPase (SERCA) and Glut4. 50 rats were divided into five groups: control, T2DM, T2DM treated with either adiponectin gene or exercise or a combination of both. Serum glucose, insulin, HOMA index, triglycerides, and cholesterol were measured. Weight gain%, muscle contractile parameters {(peak twitch tension (Pt), peak tetanic tension (PTT), half relaxation time (HRT)}, and gene expression of SERCA, Glut4, and adiponectin were assessed in gastrocnemius muscle. Diabetic rats treated with either adiponectin gene or exercise showed significant reduction in all serum parameters and wt gain%. There was significant elevation in Pt and PTT with shortening in HRT. Furthermore, a significant increase in SERCA, Glut4, and adiponectin gene expression was noticed in both groups. Combination therapy caused marked gene expression of SERCA, GLUT4, and greater improvement in muscle contractility than either of the monotherapies. Skeletal muscle dysfunction in T2DM is mediated via impaired SERCA and Glut 4. Combination therapy offered best protection against muscle dysfunction and provides a novel promising strategy for a complete cure of muscle dysfunction in T2DM.

Relation of Heart-Rate Recovery to New Onset Heart Failure and Atrial Fibrillation in Patients With Diabetes Mellitus and Preserved Ejection Fraction

Diabetic autonomic neuropathy is a possible link between abnormal metabolism in type 2 diabetes mellitus (T2DM) and risk for atrial fibrillation (AF) and heart failure (HF). The aim of this study was to elucidate the association between attenuated heart rate recovery (HRR) and these manifestations of myocardial dysfunction in T2DM. Nine hundred fourteen consecutive patients with T2DM (mean age 56 ± 11 years, 508 men) without diabetes mellitus complications, with negative results on stress echocardiography, were enrolled. Patients with known cardiac disease were excluded. Demographics, clinical assessment, co-morbidities, and insulin use were collected prospectively. The association of HRR with new-onset HF and AF was sought using a Cox proportional-hazards model. There were 47 events (22 HF and 25 AF) during a median follow-up period of 7.8 years. Events were associated with age, exercise capacity, HRR, and left atrial volume index but not with baseline glycosylated hemoglobin, left ventricular mass index, or standard markers of diastolic function. In sequential Cox models for the combined outcomes, the model based on clinical data (age and gender; overall chi-square = 5.5) was not significantly improved by left atrial volume index (chi-square = 8.6, p = 0.10) or maximum METs (chi-square = 8.7, p = 0.07) but was significantly improved by adding HRR (chi-square = 19.7, p = 0.004). In addition, HRR provided significant incremental prognostic value regarding the composite end point (net reclassification improvement 19.2%, p = 0.04; integrated discrimination improvement 1.58%, p = 0.004). In conclusion, the association of HRR with subsequent HF and AF, independent of and incremental to left atrial volume index and other markers of abnormal cardiac structure and function, indicates a role for autonomic neuropathy as the link between metabolic and cardiac risk in patients with T2DM.

Adverse Alterations in Mitochondrial Function Contribute to Type 2 Diabetes Mellitus–Related Endothelial Dysfunction in Humans

Mitochondrial dysfunction plays a key pathophysiological role in type 2 diabetes mellitus (T2DM). Data delineating relationships between mitochondrial and endothelial dysfunction in humans with T2DM are lacking. In 122 human subjects (60 with T2DM, 62 without T2DM), we measured endothelial function by brachial artery ultrasound (flow mediated dilation) and digital pulse amplitude tonometery. Endothelial function in arterioles isolated from gluteal subcutaneous adipose was measured by videomicroscopy. In arterioles and mononuclear cells, we measured inner mitochondrial membrane potential (Δψ(m)), mitochondrial mass, and mitochondrial superoxide production using fluorophores. Endothelial function was impaired in T2DM subjects versus control subjects. Δψ(m) magnitude was larger and mitochondrial mass was lower in arterioles and mononuclear cells in T2DM. Mononuclear mitochondrial mass correlated with flow-mediated dilation and pulse amplitude tonometery (ρ=0.38 and 0.33, P=0.001 and 0.02, respectively), and mononuclear mitochondrial superoxide production inversely correlated with flow-mediated dilation (ρ=-0.58, P=0.03). Low doses of 2 different mitochondrial uncoupling agents (carbonyl cyanide m-chlorophenyl hydrazone and 2,4-dinitrophenol) that reduce Δψ(m) magnitude and a mitochondrial-targeted antioxidant (MitoTEMPOL) improved endothelial function and reduced mitochondrial superoxide levels in T2DM arterioles. Mitochondrial dysfunction may play a central role in the impairment of endothelial dysfunction in T2DM.

Role of ER Stress in Ventricular Contractile Dysfunction in Type 2 Diabetes

BackgroundDiabetes mellitus (DM) is associated with an increased risk of ischemic heart disease and of adverse outcomes following myocardial infarction (MI). Here we assessed the role of endoplasmic reticulum (ER) stress in ventricular dysfunction and outcomes after MI in type 2 DM (T2DM).Methodology and Principal FindingsIn hearts of OLETF, a rat model of T2DM, at 25∼30 weeks of age, GRP78 and GRP94, markers of ER stress, were increased and sarcoplasmic reticulum calcium ATPase (SERCA)2a protein was reduced by 35% compared with those in LETO, a non-diabetic control. SERCA2a mRNA levels were similar, but SERCA2a protein was more ubiquitinated in OLETF than in LETO. Left ventricular (LV) end-diastolic elastance (Eed) was higher in OLETF than in LETO (53.9±5.2 vs. 20.2±5.6 mmHg/µl), whereas LV end-systolic elastance and positive inotropic responses to β-adrenergic stimulation were similar in OLETF and LETO. 4-Phenylbutyric acid (4-PBA), an ER stress modulator, suppressed both GRP up-regulation and SERCA2a ubiquitination and normalized SERCA2a protein level and Eed in OLETF. Sodium tauroursodeoxycholic acid, a structurally different ER stress modulator, also restored SERCA2a protein level in OLETF. Though LV dysfunction was modest, mortality within 48 h after coronary occlusion was markedly higher in OLETF than in LETO (61.3% vs. 7.7%). Telemetric recording showed that rapid progression of heart failure was responsible for the high mortality rate in OLETF. ER stress modulators failed to reduce the mortality rate after MI in OLETF.ConclusionsER stress reduces SERCA2a protein via its augmented ubiquitination and degradation, leading to LV diastolic dysfunction in T2DM. Even at a stage without systolic LV dysfunction, susceptibility to lethal heart failure after infarction is markedly increased, which cannot be explained by ER stress or change in myocardial response to sympathetic nerve activation.

Poly(ADP-Ribose) Polymerase 1 Inhibition Improves Coronary Arteriole Function in Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is associated with microvascular dysfunction. We hypothesized that increased poly(ADP-ribose) polymerase 1 (PARP-1) activity contributes to microvascular dysfunction in T2DM. T2DM (db(-)/db(-)) and nondiabetic control (db(-)/db(+)) mice were treated with 2 different PARP-1 inhibitors (INO-1001, 5 mg/kg per day and ABT-888, 15 mg/kg per day) for 2 weeks. Isolated coronary arterioles were mounted in an arteriograph. Pressure-induced myogenic tone was significantly potentiated, whereas endothelium-dependent relaxation was significantly attenuated in diabetic mice compared with control mice. These results were associated with decreased endothelial NO synthase phosphorylation and cGMP level and increased PARP-1 activity in coronary arterioles from diabetic mice compared with control mice. Interestingly, PARP-1 inhibitors significantly reduced the potentiation of myogenic tone, improved endothelium-dependent relaxation, restored endothelial NO synthase phosphorylation and cGMP, and attenuated cleaved PARP-1. These results were supported by in vitro studies indicating that downregulation of PARP-1 in mesenteric resistance arteries using PARP-1 short hairpin RNA lentiviral particles significantly improved endothelium-dependent relaxation in mesenteric resistance arteries from diabetic mice compared with control mice. The inhibition of NO synthesis by N(G)-nitro-L-arginine methyl ester (L-NAME) significantly reduced the endothelium-dependent relaxation in coronary arterioles and mesenteric resistance arteries from control and diabetic mice treated with PARP-1 inhibitors and PARP-1 short hairpin RNA lentiviral particles. In addition, we demonstrated that enhanced cleaved PARP-1, its binding to DNA, and DNA damage were reduced after PARP-1 inhibition in cultured endothelial cells stimulated with high glucose. We provide evidence that T2DM impairs microvascular function by an enhanced PARP-1 activity-dependent mechanism. Therefore, PARP-1 could be a potential target for overcoming diabetic microvascular complications.

Quantitative Imaging of Electron Transfer Flavoprotein Autofluorescence Reveals Lipid Partitioning Dynamics in Pancreatic Islets

Pancreatic islet beta-cells are sensitive to plasma nutrients in the body. Excess levels of glucose and fatty acids lead to glucolipotoxicity, resulting in declined beta-cell function and survival - a major component of type 2 diabetes mellitus (T2DM). Despite significant knowledge of glucose-stimulated insulin secretion, the effect of fatty acids remains uncertain. Here we show a novel way to measure a response from fatty acids in ex vivo pancreatic islets using quantitative autofluorescence imaging of a Complex II flavin, electron transfer flavoprotein (ETF). Together with two-photon imaging of NAD(P)H and our previously reported lipoamide dehydrogenase (LipDH) autofluorescence, we found that the electron transport chain is nutrient supply-driven and dominated by Complex I rather than Complex II. These data are consistent with beta-cells being predominantly glucose responsive. Furthermore, we found an oxidized ETF redox response in the presence of excess glucose-stimulation, suggesting a shift in lipid partitioning from fatty acid oxidization to synthesis above 10 mM glucose. Our results demonstrate that ETF autofluorescence can in part be used as readout of islet response to fat. Overall, we anticipate our ETF imaging platform to be a starting point for more sophisticated biological studies that will explore mechanisms of mitochondrial dysfunction in T2DM.

Role and clinical significance of lymphocyte mitochondrial dysfunction in type 2 diabetes mellitus

Lymphocyte homeostasis in type 2 diabetes mellitus (T2DM) is associated with increased susceptibility to infections. Mitochondrial oxidative stress is implicated primarily in the immune pathophysiology of diabetes; however, the molecular underpinnings of lymphocyte mitochondrial dysfunction and ensuing downstream cellular effects are hitherto unreported. Both in early diagnosed patients and patients with late complications, we observed an inverse correlation between mitochondrial DNA content in lymphocytes and hemoglobin A1 (HbA1c) levels. This relation established for the first time might serve as a general, yet direct, predictor or indicator for mitochondrial dysfunction in T2DM. Compared with controls, nuclear DNA damage response was higher (P ≤ 0.001) in diabetic subjects with increased accumulation of phospho-ataxia-telangiectasia (ATM), γ-H2AX, along with active recruitment of repair proteins (Mre11, Rad50, and Nbs1). A higher frequency (>2%) of stable chromosomal anomalies with loss of telomere integrity was observed in cases with late complications. A significant decrease (P ≤ 0.001) in enzyme activity of complex II, III, and IV of mitochondrial respiratory chain was evident in both diabetic groups in comparison with healthy controls. Activation in the cascade of nuclear factor kappa-beta (NF-κβ)-mediated feed-forward proinflammatory cytokine response was noted among T2DM subjects. Increased oxidative stress, mitochondrial membrane depolarization, activation of caspase-3, and PARP observed in diabetic groups indicated bax triggered mitochondrial mediated cellular apoptosis. Our results provide the first insights of lymphocyte mitochondrial dysfunction that might be helpful in explaining the clinical significance of immunologic perturbation observed in type 2 diabetic conditions. Our data also indicate that maneuvering through the mitochondrial function might be a viable, indirect method to modulate lymphocyte homeostasis in T2DM.

Pioglitazone and alogliptin combination therapy in type 2 diabetes: a pathophysiologically sound treatment.

Insulin resistance and islet (beta and alpha) cell dysfunction are major pathophysiologic abnormalities in type 2 diabetes mellitus (T2DM). Pioglitazone is a potent insulin sensitizer, improves pancreatic beta cell function and has been shown in several outcome trials to lower the risk of atherosclerotic and cardiovascular events. Glucagon-like peptide-1 deficiency/resistance contributes to islet cell dysfunction by impairing insulin secretion and increasing glucagon secretion. Dipeptidyl peptidase-4 (DPP-4) inhibitors improve pancreatic islet function by augmenting glucose-dependent insulin secretion and decreasing elevated plasma glucagon levels. Alogliptin is a new DPP-4 inhibitor that reduces glycosylated hemoglobin (HbA(1c)), is weight neutral, has an excellent safety profile, and can be used in combination with oral agents and insulin. Alogliptin has a low risk of hypoglycemia, and serious adverse events are uncommon. An alogliptin-pioglitazone combination is advantageous because it addresses both insulin resistance and islet dysfunction in T2DM. HbA(1c) reductions are significantly greater than with either monotherapy. This once-daily oral combination medication does not increase the risk of hypoglycemia, and tolerability and discontinuation rates do not differ significantly from either monotherapy. Importantly, measures of beta cell function and health are improved beyond that observed with either monotherapy, potentially improving durability of HbA(1c) reduction. The alogliptin-pioglitazone combination represents a pathophysiologically sound treatment of T2DM.

Blood pressure levels in pre‐diabetic stages are associated with worse cognitive functioning in patients with type 2 diabetes

Type 2 diabetes mellitus (T2DM) is associated with mild decrements in cognitive functioning, but the relation of these decrements to metabolic and vascular risk factors is unclear. The present study compared the vascular risk factor profile over the preceding 16 years between T2DM patients with good cognitive functioning and those with poor cognitive functioning. The Hoorn study is a population-based cohort study on glucose metabolism and vascular disease initiated in 1989, with follow-up examinations in 1996-1998, 2000-2001 and 2005-2007. Cognitive functioning was assessed in 2005-2007. Patients who developed T2DM between 1989 and 2000-2001 (n = 64) were divided in tertiles (lowest tertile = 'poor cognition', highest tertile = 'good cognition') according to a sum score for performance across cognitive domains (SUM) and the domain score for information-processing speed (IPS). The time course of vascular risk factors from 1989 to 2005-2007 was compared between these tertiles with linear mixed models adjusted for age, sex and estimated IQ. Present levels (2005-2007) of vascular risk factors did not differ between patients with relatively poor or good cognition. However, patients with poor cognition had a 14-18 mmHg higher systolic blood pressure in 1989 than patients with good cognition. There were no differences in lipid profile and body weight at any time during the study between the groups. For IPS the T2DM patients with poor cognition even had a lower baseline HbA(1c) level than patients with good cognition. Cognitive dysfunction in T2DM is related to the cumulative effects of long-term exposure to hypertension, even in pre-DM stages.

Reappraising the stereotypes of diabetes in the modern diabetogenic environment

The prevailing concentration of blood glucose is a result of the integrated regulation of insulin secretion and insulin action. Nevertheless, the classic stereotypes of diabetes are dichotomous: type 1 diabetes mellitus (T1DM) is attributed to impaired insulin secretion, and type 2 diabetes mellitus (T2DM) is primarily attributed to impaired insulin action (insulin resistance). The available evidence indicates that this view is overly simplistic. Impaired insulin secretion (beta-cell dysfunction) is also a feature of T2DM, and insulin resistance is also a risk factor for the development of T1DM. Moreover, with the increasing incidence of T2DM and T1DM in both developed and developing countries, attributed to environmental factors, the existence of 'hybrid' diabetes types that have clinical and pathogenetic features of both conditions is becoming clearly evident. A common thread across the spectrum of diabetes might be the activation of innate immunological and inflammatory pathways by a proinflammatory environment, which leads to beta-cell dysfunction in T2DM, insulin resistance in both T2DM and T1DM, and enhanced adaptive immunity that kills beta cells in T1DM. Embracing a holistic view of the diabetes syndrome will help us to understand the environmental basis for the epidemic of diabetes and improve preventative strategies.

Retinopathy in type 2 diabetes mellitus is associated with increased intima‐media thickness and endothelial dysfunction

Microangioathy and macroangiopathy in type 2 diabetes mellitus (T2DM) frequently coexist. Both types of vascular complications share traditional risk factors. It is not clear whether the presence of microangiopathy, such as diabetic retinopathy (DR), constitutes a predictor of atherosclerosis in T2DM. Here we described the search for the association between DR and intima-media thickness (IMT) in T2DM. We also compared endothelial function in subjects with and without DR. We examined 182 consecutive patients with T2DM for at least 5 years (mean age at examination 56.3 +/- 6.52 years). We assessed (i) IMT of carotid artery by ultrasound and (ii) endothelial function by flow-mediated dilatation (FMD) method as well as by measurement of concentrations of von Willebrand factor (vWF) and s-ICAM-1. All patients underwent ophthalmological examination. Statistical analysis included Student's, Mann-Whitney, chi-square, Fisher tests and multiple regression. DR was found in 71 (39.0%) subjects. IMT was higher in patients with DR than those without DR (0.87 mm vs. 0.79 mm, respectively, P = 0.0001). FMD was lower in the complication group than in subjects without DR (8.38% vs. 10.45%, respectively, P = 0.0023). Concentrations of s-ICAM-1 and vWF were not different between the groups. In multiple regression analysis, DR was among the predictors of increased IMT (P = 0.016) and decreased FMD (P = 0.002). We did not find a significant association of DR with vWF and s-ICAM-1 (P = 0.09 and P = 0.11, respectively). DR is associated with increased IMT and endothelial dysfunction in T2DM. Impaired endothelial function may be a common denominator of pathogenesis of microvascular complications and atherosclerosis in T2DM.