Cardiovascular disease in diabetes: where does glucose fit in?

Serum/plasma biomarkers and the progression of cardiometabolic multimorbidity: a systematic review and meta-analysis

Background

The role of certain biomarkers in the development of single cardiometabolic disease (CMD) has been intensively investigated. Less is known about the association of biomarkers with multiple CMDs (cardiometabolic multimorbidity, CMM), which is essential for the exploration of molecular targets for the prevention and treatment of CMM. We aimed to systematically synthesize the current evidence on CMM-related biomarkers.

Methods

We searched PubMed, Embase, Web of Science, and Ebsco for relevant studies from inception until August 31st, 2022. Studies reported the association of serum/plasma biomarkers with CMM, and relevant effect sizes were included. The outcomes were five progression patterns of CMM: (1) no CMD to CMM; (2) type 2 diabetes mellitus (T2DM) followed by stroke; (3) T2DM followed by coronary heart disease (CHD); (4) T2DM followed by stroke or CHD; and (5) CHD followed by T2DM. Newcastle-Ottawa Quality Assessment Scale (NOS) was used to assess the quality of the included studies. A meta-analysis was conducted to quantify the association of biomarkers and CMM.

Results

A total of 68 biomarkers were identified from 42 studies, which could be categorized into five groups: lipid metabolism, glycometabolism, liver function, immunity, and others. Lipid metabolism biomarkers were most reported to associate with CMM, including TC, TGs, HDL-C, LDL-C, and Lp(a). Fasting plasma glucose was also reported by several studies, and it was particularly associated with coexisting T2DM with vascular diseases. According to the quantitative meta-analysis, HDL-C was negatively associated with CHD risk among patients with T2DM (pooled OR for per 1 mmol/L increase = 0.79, 95% CI = 0.77-0.82), whereas a higher TGs level (pooled OR for higher than 150 mg/dL = 1.39, 95% CI = 1.10-1.75) was positively associated with CHD risk among female patients with T2DM.

Conclusion

Certain serum/plasma biomarkers were associated with the progression of CMM, in particular for those related to lipid metabolism, but heterogeneity and inconsistent findings still existed among included studies. There is a need for future research to explore more relevant biomarkers associated with the occurrence and progression of CMM, targeted at which is important for the early identification and prevention of CMM.

Intermediate hyperglycaemia, diabetes and blood pressure in rural Bangladesh: five-year post-randomisation follow-up of the DMagic cluster-randomised controlled trial

Background

The DMagic trial showed that participatory learning and action (PLA) community mobilisation delivered through facilitated community groups, and mHealth voice messaging interventions improved diabetes knowledge in Bangladesh and the PLA intervention reduced diabetes occurrence. We assess intervention effects three years after intervention activities stopped.

Methods

Five years post-randomisation, we conducted a cross-sectional survey among a random sample of adults aged ≥30-years living in the 96 DMagic villages, and a cohort of individuals identified with intermediate hyperglycaemia at the start of the DMagic trial in 2016. Primary outcomes were: 1) the combined prevalence of intermediate hyperglycaemia and diabetes; 2) five-year cumulative incidence of diabetes among the 2016 cohort of individuals with intermediate hyperglycaemia. Secondary outcomes were: weight, BMI, waist and hip circumferences, blood pressure, knowledge and behaviours. Primary analysis compared outcomes at the cluster level between intervention arms relative to control.

Findings

Data were gathered from 1623 (82%) of the randomly selected adults and 1817 (87%) of the intermediate hyperglycaemia cohort. 2018 improvements in diabetes knowledge in mHealth clusters were no longer observable in 2021. Knowledge remains significantly higher in PLA clusters relative to control but no difference in primary outcomes of intermediate hyperglycaemia and diabetes prevalence (OR (95%CI) 1.23 (0.89, 1.70)) or five-year incidence of diabetes were observed (1.04 (0.78, 1.40)). Hypertension (0.73 (0.54, 0.97)) and hypertension control (2.77 (1.34, 5.75)) were improved in PLA clusters relative to control.

Interpretation

PLA intervention effect on intermediate hyperglycaemia and diabetes was not sustained at 3 years after intervention end, but benefits in terms of blood pressure reduction were observed.

Funding

Medical Research Council UK: MR/M016501/1 (DMagic trial); MR/T023562/1 (DClare study), under the Global Alliance for Chronic Diseases (GACD) Diabetes and Scale-up Programmes, respectively.

Evolution of the diagnostic value of "the sugar of the blood": hitting the sweet spot to identify alterations in glucose dynamics

In this paper, we provide an overview of the evolution of the definition of hyperglycemia during the past century and the alterations in glucose dynamics that cause fasting and postprandial hyperglycemia. We discuss how extensive mechanistic, physiological research into the factors and pathways that regulate the appearance of glucose in the circulation and its uptake and metabolism by tissues and organs has contributed knowledge that has advanced our understanding of different types of hyperglycemia, namely prediabetes and diabetes and their subtypes (impaired fasting plasma glucose, impaired glucose tolerance, combined impaired fasting plasma glucose, impaired glucose tolerance, type 1 diabetes, type 2 diabetes, gestational diabetes mellitus), their relationships with medical complications, and how to prevent and treat hyperglycemia.

Post-prandial effects of high-polyphenolic extra virgin olive oil on endothelial function in adults at risk for type 2 diabetes: A randomized controlled crossover trial

BACKGROUND

Effects of olive oil on cardiovascular risk have been controversial. We compared the effects of high-polyphenolic extra virgin olive oil (EVOO) and refined olive oil without polyphenols on endothelial function (EF) in adults at risk for Type 2 diabetes mellitus (T2DM).

METHODS

Randomized, controlled, double-blind, crossover trial of 20 adults (mean age 56.1 years; 10 women, 10 men) at risk for T2DM (i.e., as defined by either prediabetes or metabolic syndrome) assigned to one of two possible sequence permutations of two different single dose treatments (50 mL of high-polyphenolic EVOO or 50 mL of refined olive oil without polyphenols), with 1-week washout. Participants received their olive oils in a smoothie consisting of ½ cup frozen blueberries and 1 cup (8 oz) low-fat vanilla yogurt blended together. Primary outcome measure was EF measured as flow-mediated dilatation. Participants were evaluated before and 2 h after ingestion of their assigned olive oil treatment.

RESULTS

EVOO acutely improved EF as compared to refined olive oil (1.2 ± 6.5% versus -3.6 ± 3.8%; p = 0.0086). No significant effects on systolic or diastolic blood pressure were observed.

CONCLUSIONS

High-polyphenolic EVOO acutely enhanced EF in the study cohort, whereas refined olive oil did not. Blood pressure effects were not observed. Reports on the vascular effects of olive oil ingestion should specify the characteristics of the oil.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04025281.

Fasting plasma glucose and subsequent cardiovascular disease among young adults: Analysis of a nationwide epidemiological database

BACKGROUND AND AIMS

Using a nationwide epidemiological database, we aimed to clarify the association of fasting plasma glucose (FPG) with subsequent cardiovascular disease (CVD) risk among young adults.

METHODS AND RESULTS

Medical records of 1,180,062 young adults (20-49 years old) without a prior history of CVD and who were not taking antidiabetic medications were extracted from the Japan Medical Data Center. We categorized the study population into four groups: normal, FPG level<100 mg/dL (1,007,747 individuals), normal-high, FPG level of 100-109 mg/dL (126,602 individuals), impaired fasting glucose (IFG), FPG level of 110-125 mg/dL (32,451 individuals), and diabetes mellitus (DM), FPG level ≥126 mg/dL (13,262 individuals). The mean age was 39.7 ± 6.9 years, and 57.0% of the study population were men. Mean follow-up period was 1201 ± 905 days on average. Multivariable Cox regression analysis showed that IFG (hazard ratio [HR]; 1.38) and DM (HR; 2.09) increased the risk of myocardial infarction. Normal-high (HR; 1.11), IFG (HR; 1.18), and DM (HR; 1.59) groups had an elevated angina pectoris risk. DM (HR; 1.31) increased the risk of stroke compared to normal FPG levels. Normal-high levels (HR; 1.10), IFG (HR; 1.22) and DM (HR; 1.58) elevated the risk of heart failure. DM (HR; 1.69) increased the risk of atrial fibrillation.

CONCLUSIONS

Our analysis of a nationwide epidemiological database demonstrated a close association of the FPG category with subsequent CVD risk. Our results exemplify the importance of optimal FPG maintenance for the primary prevention of CVD in young adults.

Repetitive Intermittent Hyperglycemia Drives the M1 Polarization and Inflammatory Responses in THP-1 Macrophages Through the Mechanism Involving the TLR4-IRF5 Pathway

Repetitive intermittent hyperglycemia (RIH) is an independent risk factor for complications associated with type-2 diabetes (T2D). Glucose fluctuations commonly occur in T2D patients with poor glycemic control or following intensive therapy. Reducing blood glucose as well as glucose fluctuations is critical to the control of T2D and its macro-/microvascular complications. The interferon regulatory factor (IRF)-5 located downstream of the nutrient sensor toll-like receptor (TLR)-4, is emerging as a key metabolic regulator. It remains unclear how glucose fluctuations may alter the IRF5/TLR4 expression and inflammatory responses in monocytes/macrophages. To investigate this, first, we determined IRF5 gene expression by real-time qRT-PCR in the white adipose tissue samples from 39 T2D and 48 nondiabetic individuals. Next, we cultured THP-1 macrophages in hypo- and hyperglycemic conditions and compared, at the protein and transcription levels, the expressions of IRF5, TLR4, and M1/M2 polarization profile and inflammatory markers against control (normoglycemia). Protein expression was assessed using flow cytometry, ELISA, Western blotting, and/or confocal microscopy. IRF5 silencing was achieved by small interfering RNA (siRNA) transfection. The data show that adipose IRF5 gene expression was higher in T2D than nondiabetic counterparts (P = 0.006), which correlated with glycated hemoglobin (HbA1c) (r = 0.47/P < 0.001), homeostatic model assessment of insulin resistance (HOMA-IR) (r = 0.23/P = 0.03), tumor necrosis factor (TNF)-α (r = 0.56/P < 0.0001), interleukin (IL)-1β (r = 0.40/P = 0.0009), and C-C motif chemokine receptor (CCR)-2 (r = 0.49/P < 0.001) expression. IRF5 expression in macrophages was induced/upregulated (P < 0.05) by hypoglycemia (3 mM/L), persistent hyperglycemia (15 mM/L-25 mM/L), and RIH/glucose fluctuations (3-15 mM/L) as compared to normoglycemia (5 mM/L). RIH/glucose fluctuations also induced M1 polarization and an inflammatory profile (CD11c, IL-1β, TNF-α, IL-6, and monocyte chemoattractant protein (MCP)-1) in macrophages. RIH/glucose fluctuations also drove the expression of matrix metalloproteinase (MMP)-9 (P < 0.001), which is a known marker for cardiovascular complication in T2D patients. Notably, all these changes were counteracted by IRF5 silencing in macrophages. In conclusion, RIH/glucose fluctuations promote the M1 polarization and inflammatory responses in macrophages via the mechanism involving TLR4-IRF5 pathway, which may have significance for metabolic inflammation.

Different physiological mechanisms underlie an adverse cardiovascular disease risk profile in men and women

CVD affect about one-third of the population and are the leading cause of mortality. The prevalence of CVD is closely linked to the prevalence of obesity because obesity is commonly associated with metabolic abnormalities that are important risk factors for CVD, including insulin resistance, pre-diabetes, and type-2 diabetes, atherosclerotic dyslipidaemia, endothelial dysfunction and hypertension. Women have a more beneficial traditional CVD risk profile (lower fasting plasma glucose, less atherogenic lipid profile) and a lower absolute risk for CVD than men. However, the relative risk for CVD associated with hyperglycaemia and dyslipidaemia is several-fold higher in women than in men. The reasons for the sex differences in CVD risk associated with metabolic abnormalities are unclear but could be related to differences in the mechanisms that cause hyperglycaemia and dyslipidaemia in men and women, which could influence the pathogenic processes involved in CVD. In the present paper, we review the influence of a person's sex on key aspects of metabolism involved in the cardiometabolic disease process, including insulin action on endogenous glucose production, tissue glucose disposal, and adipose tissue lipolysis, insulin secretion and insulin plasma clearance, postprandial glucose, fatty acid, and triglyceride kinetics, hepatic lipid metabolism and myocardial substrate use. We conclude that there are marked differences in many aspects of metabolism in men and women that are not all attributable to differences in the sex hormone milieu. The mechanisms responsible for these differences and the clinical implications of these observations are unclear and require further investigation.

The sweet spot: fasting glucose, cardiovascular disease, and mortality in older adults with diabetes: a nationwide population-based study

Background

Growing evidences shows that fasting glucose target should be different according to their health condition in older adults with diabetes. However, there are limited data regarding the relationship between fasting glucose level and health outcomes in Korean older people with diabetes. We aimed to examine the association of fasting glucose with mortality and cardiovascular events in Korean older adults with type 2 diabetes.

Methods

From the Korean National Health Insurance System, 227,938 subjects (aged ≥ 65 years) with type 2 diabetes but no history of cardiovascular events (myocardial infarction or stroke) who underwent ≥ 2 health examinations from 2009 to 2010 and who were followed up until 2017 were identified. The primary exposure variable was the mean fasting glucose level. We estimated the relationship between the baseline fasting glucose level and incidences of all-cause death and cardiovascular events. Comorbidity load was assessed using the Charlson comorbidity index.

Results

Fasting glucose levels and all-cause mortality risk showed a J-shaped relationship regardless of sex and number of comorbidities. Fasting glucose levels associated with the lowest mortality and cardiovascular events were 110–124 and 95–124 mg/dL, respectively. Stratified analysis by comorbidity load using the Charlson comorbidity index revealed higher optimal fasting glucose levels for the lowest cardiovascular events in subjects with Charlson comorbidity index ≥ 3 than in those with Charlson comorbidity index ≤ 2 (119 vs. 112 mg/dL, P = 0.04).

Conclusions

J-shaped relationship existed between fasting glucose and all-cause mortality and cardiovascular events in Korean older adults with diabetes. We identified that fasting glucose levels associated with the lowest mortality and cardiovascular events were 110–124 and 95–124 mg/dL respectively. Increased risk of cardiovascular events with low fasting glucose level (< 95 mg/dL) was noted, especially in patients with high comorbidity. These findings suggested that less stringent targets of fasting glucose may be beneficial especially in older adults with multiple comorbidities.

Naringenin-induced HO-1 ameliorates high glucose or free fatty acids-associated apoptosis via PI3K and JNK/Nrf2 pathways in human umbilical vein endothelial cells

Naringenin (NG), a flavanone extracted from various plants, has potent vasoprotective effects likely related to the induction of heme oxygenase-1 (HO-1). In the current study, we investigated mechanisms underlying the effect of NG on HO-1 expression and high glucose (HG)- or free fatty acids (FFA)-induced apoptosis in human umbilical vein endothelial cells (HUVECs). First, we found that HUVECs exposed to NG exhibited enhanced HO-1 expression in a concentration- and time-dependent manner. Moreover, HUVECs treated with NG exhibited activation of phosphoinositide 3 kinase (PI3K)/Akt, extracellular-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK). LY294002 (a PI3K inhibitor) and SP600125 (a JNK inhibitor) reduced NG-induced HO-1 expression, whereas BIRB796 (a p38 inhibitor) and PD98059 (an ERK inhibitor) had no effect. The cytoprotective effects of NG were correlated with activation of the transcription factor NF-E2-related factor 2 (Nrf2), a critical regulator of HO-1 expression. Indeed, the results of our experiments using LY294002 and SP600125 indicated that NG may stimulate Nrf2 through PI3K/Akt and JNK pathway activation. Moreover, treatment of HUVECs with Nrf2 siRNA decreased NG-induced HO-1 expression. Finally, pretreatment of HUVECs with NG remarkably reduced HG- or FFA-induced cell apoptosis, and this effect was greatly abrogated in the presence of SnPP (an HO-1 inhibitor). Above all, our data show that NG increased HO-1 expression and reduced HG- or FFA-induced cell apoptosis in HUVECs by upregulating PI3K, JNK, and Nrf2 pathways, which may confer an adaptive survival response in diabetes-induced vascular injury.

Learning from Longitudinal Data in Electronic Health Record and Genetic Data to Improve Cardiovascular Event Prediction

Current approaches to predicting a cardiovascular disease (CVD) event rely on conventional risk factors and cross-sectional data. In this study, we applied machine learning and deep learning models to 10-year CVD event prediction by using longitudinal electronic health record (EHR) and genetic data. Our study cohort included 109, 490 individuals. In the first experiment, we extracted aggregated and longitudinal features from EHR. We applied logistic regression, random forests, gradient boosting trees, convolutional neural networks (CNN) and recurrent neural networks with long short-term memory (LSTM) units. In the second experiment, we applied a late-fusion approach to incorporate genetic features. We compared the performance with approaches currently utilized in routine clinical practice - American College of Cardiology and the American Heart Association (ACC/AHA) Pooled Cohort Risk Equation. Our results indicated that incorporating longitudinal feature lead to better event prediction. Combining genetic features through a late-fusion approach can further improve CVD prediction, underscoring the importance of integrating relevant genetic data whenever available.

Targeting Select Cellular Stress Pathways to Prevent Hyperglycemia-Related Complications: Shifting the Paradigm

Despite the advances made in preventing complications of diabetes, there is still substantial residual risk. Hence the need for developing new therapeutic agents that target the various facets of the pathogenesis of complications in people with diabetes. Traditionally four general biochemical pathways had been recognized as major contributors to glucotoxicity. These include the polyol pathway, the protein kinase C (PKC) pathway, glycosylation pathway, and oxidative stress. The latter has been proposed as a common impetus of the other pathways of glucotoxicity. More recently, the cross talk between oxidative stress and other recognized cellular stresses such as endoplasmic reticulum (ER), inflammatory, and mitochondrial stresses has emerged as an important additional mechanism of glucotoxicity. The observation that targeting oxidative stress with antioxidants has been associated with unfavorable clinical outcomes and the recognition that in cell cultures antioxidants may aggravate ER stress, suggests that selective targeting of individual cellular stresses may not be sufficient for preventing glucotoxicity. Future efforts should focus on developing therapeutic agents that can ameliorate cellular stress globally by simultaneously targeting the oxidative, ER, mitochondrial, and inflammatory stresses.

Therapeutic Targeting of Cellular Stress to Prevent Cardiovascular Disease: A Review of the Evidence

The availability of effective drugs targeting the major risk factors of cardiovascular disease (CVD) has reduced morbidity and mortality. Cumulative relative risk of CVD events can be reduced by 75 % with a combination of aspirin, a β-adrenoceptor antagonist (β-blocker), an HMG-CoA reductase inhibitor (statin), and an angiotensin-converting enzyme inhibitor. The principal pharmacodynamics of these drugs cannot explain the entirety of their cardioprotective action, as other drugs with similar pharmacologic targets have not been associated with favorable clinical effects. This raises the possibility that the cardioprotective drugs have a unique pleiotropic activity that contributes to their clinical efficacy. Recent data suggest that reducing cellular stress such as oxidative, inflammatory, and endoplasmic reticulum stress, might be a common denominator of the drugs with proven efficacy in reducing CVD risk. In this communication, the evidence in favor of this hypothesis is discussed, and ongoing trials with therapeutic agents targeting cellular stresses are reviewed.

Low nanomolar caffeic acid attenuates high glucose-induced endothelial dysfunction in primary human umbilical-vein endothelial cells by affecting NF-κB and Nrf2 pathways

Hyperglycemia contributes to dysregulate endothelial function associated with diabetes, leading to initiation and propagation of vascular complications and dysfunction. Caffeic acid (CA), a dietary hydroxycinnamic acid abundant in coffee, has been reported to exert antidiabetic effects in rat models. Herein, we investigated the molecular effects of physiological concentrations of CA (10 nM) against endothelial dysfunction induced by high glucose (HG) in human endothelial cells (HUVECs). HUVECs were exposed to HG 25 mM, to mimic diabetic condition, in presence of CA. Intracellular redox status (reduced glutathione, superoxide dismutase (SOD) and total antioxidant activity levels), and NF-κB pathway were examined. We also evaluated the involvement of NF-E2-related factor 2 (Nrf2)/electrophile responsive element (EpRE) pathway. Our data show that CA inhibits HG-induced nuclear translocation of NF-κB and the downstream expression of endothelial adhesion molecule 1 and restores antioxidant levels by upregulating Nrf2/EpRE pathway. Our data suggest that CA can suppress several aspects of HG-induced endothelial dysfunction through the modulation of intracellular redox status controlled by the transcription factor Nrf2. These findings highlight that low physiological concentration of CA achievable specifically upon food consumption are able to prevent endothelial dysfunction associated with inflammation and oxidative stress induced by high concentration of glucose. © 2016 BioFactors, 43(1):54-62, 2017.

Clinical Update: Cardiovascular Disease in Diabetes Mellitus: Atherosclerotic Cardiovascular Disease and Heart Failure in Type 2 Diabetes Mellitus - Mechanisms, Management, and Clinical Considerations

Cardiovascular disease remains the principal cause of death and disability among patients with diabetes mellitus. Diabetes mellitus exacerbates mechanisms underlying atherosclerosis and heart failure. Unfortunately, these mechanisms are not adequately modulated by therapeutic strategies focusing solely on optimal glycemic control with currently available drugs or approaches. In the setting of multifactorial risk reduction with statins and other lipid-lowering agents, antihypertensive therapies, and antihyperglycemic treatment strategies, cardiovascular complication rates are falling, yet remain higher for patients with diabetes mellitus than for those without. This review considers the mechanisms, history, controversies, new pharmacological agents, and recent evidence for current guidelines for cardiovascular management in the patient with diabetes mellitus to support evidence-based care in the patient with diabetes mellitus and heart disease outside of the acute care setting.

Use of insulin in type 2 diabetes: what we learned from recent clinical trials on the benefits of early insulin initiation

The majority of people with type 2 diabetes mellitus (T2DM) require insulin therapy to maintain HbA(1c) levels < 7% during the first decade of diagnosis. Large prospective trials investigating the cardiovascular (CV) benefits of intensive glycaemic control have produced inconsistent results; however, meta-analyses have suggested that intensive glycaemic control provides both micro- and macrovascular benefits. The ORIGIN study investigated the impact of basal insulin glargine therapy targeting ≤ 5.3 mmol/L for fasting plasma glucose compared with standard care on CV outcomes in people with pre- or early diabetes, and demonstrated a neutral effect on CV outcomes with long-term use of insulin glargine early in the course of diabetes, with a low rate of severe hypoglycaemia and modest weight gain. The EARLY, GLORY and EASIE studies also demonstrated that insulin use earlier in the treatment pathway led to improved glycaemic control, reduced weight gain and fewer hypoglycaemic episodes than when insulin was added later in the course of disease. The beneficial effect of early transient intensive insulin therapy (TIIT) at diagnosis has been demonstrated in a number of trials; it rapidly limits the damage caused by gluco- and lipotoxicity, improving residual β-cell function and potentially slowing disease progression. The evidence suggests that people newly diagnosed with T2DM and HbA(1c) > 9% should be given early TIIT to achieve normoglycaemia within weeks, after which standard care should then be adopted. Insulin use earlier in the treatment pathway should be considered, as it reduces the risk of hypoglycaemia as well as allows β-cell rest, which can help preserve β-cell function.

Impaired mitochondrial energy supply coupled to increased H2O2 emission under energy/redox stress leads to myocardial dysfunction during Type I diabetes

In Type I diabetic (T1DM) patients, both peaks of hyperglycaemia and increased sympathetic tone probably contribute to impair systolic and diastolic function. However, how these stressors eventually alter cardiac function during T1DM is not fully understood. In the present study, we hypothesized that impaired mitochondrial energy supply and excess reactive oxygen species (ROS) emission is centrally involved in T1DM cardiac dysfunction due to metabolic/redox stress and aimed to determine the mitochondrial sites implicated in these alterations. To this end, we used isolated myocytes and mitochondria from Sham and streptozotocin (STZ)-induced T1DM guinea pigs (GPs), untreated or treated with insulin. Relative to controls, T1DM myocytes exhibited higher oxidative stress when challenged with high glucose (HG) combined with β-adrenergic stimulation [via isoprenaline (isoproterenol) (ISO)], leading to contraction/relaxation deficits. T1DM mitochondria had decreased respiration with complex II and IV substrates and markedly lower ADP phosphorylation rates and higher H2O2 emission when challenged with oxidants to mimic the more oxidized redox milieu present in HG + ISO-treated cardiomyocytes. Since in T1DM hearts insulin-sensitivity is preserved and a glucose-to-fatty acid (FA) shift occurs, we next tested whether insulin therapy or acute palmitate (Palm) infusion prevents HG + ISO-induced cardiac dysfunction. We found that insulin rescued proper cardiac redox balance, but not mitochondrial respiration or contractile performance. Conversely, Palm restored redox balance and preserved myocyte function. Thus, stressors such as peaks of HG and adrenergic hyperactivity impair mitochondrial respiration, hampering energy supply while exacerbating ROS emission. Our study suggests that an ideal therapeutic measure to treat metabolically/redox-challenged T1DM hearts should concomitantly correct energetic and redox abnormalities to fully maintain cardiac function.

Protective mechanisms of mitochondria and heart function in diabetes

SIGNIFICANCE

The heart depends on continuous mitochondrial ATP supply and maintained redox balance to properly develop force, particularly under increased workload. During diabetes, however, myocardial energetic-redox balance is perturbed, contributing to the systolic and diastolic dysfunction known as diabetic cardiomyopathy (DC).

CRITICAL ISSUES

How these energetic and redox alterations intertwine to influence the DC progression is still poorly understood. Excessive bioavailability of both glucose and fatty acids (FAs) play a central role, leading, among other effects, to mitochondrial dysfunction. However, where and how this nutrient excess affects mitochondrial and cytoplasmic energetic/redox crossroads remains to be defined in greater detail.

RECENT ADVANCES

We review how high glucose alters cellular redox balance and affects mitochondrial DNA. Next, we address how lipid excess, either stored in lipid droplets or utilized by mitochondria, affects performance in diabetic hearts by influencing cardiac energetic and redox assets. Finally, we examine how the reciprocal energetic/redox influence between mitochondrial and cytoplasmic compartments shapes myocardial mechanical activity during the course of DC, focusing especially on the glutathione and thioredoxin systems.

FUTURE DIRECTIONS

Protecting mitochondria from losing their ability to generate energy, and to control their own reactive oxygen species emission is essential to prevent the onset and/or to slow down DC progression. We highlight mechanisms enforced by the diabetic heart to counteract glucose/FAs surplus-induced damage, such as lipid storage, enhanced mitochondria-lipid droplet interaction, and upregulation of key antioxidant enzymes. Learning more on the nature and location of mechanisms sheltering mitochondrial functions would certainly help in further optimizing therapies for human DC.

Elevated risk of an intermediate or high SYNTAX score in subjects with impaired fasting glucose

OBJECTIVE

This study was designed to determine the SYNTAX score under different fasting plasma glucose (FPG) states in Chinese patients undergoing coronary angiography, particularly subjects with impaired FPG.

METHODS

Four hundred and forty-six subjects undergoing coronary angiography were enrolled in this study and divided into four groups based on the FPG level or a history of type 2 diabetes mellitus (T2DM): normal FPG, impaired FPG, known and previously unknown T2DM.

RESULTS

The angiographic SYNTAX scores were higher in the subjects with known (p<0.001) or previously unknown (p<0.001) T2DM than in those with normal FPG. There were significant differences in the number of diseased coronary artery vessels between the subjects with known (p<0.01) or unknown T2DM (p<0.05) and the subjects with normal FPG. However, there were no significant differences in the SYNTAX score or the number of diseased coronary artery vessels between the subjects with impaired FPG and those with normal FPG. The subjects with impaired FPG (2.917-fold, p=0.004) and known (3.064-fold, p=0.000) or previously unknown (3.301-fold, p=0.000) T2DM exhibited a significantly elevated risk of having an intermediate or high SYNTAX score compared with the subjects with normal FPG.

CONCLUSION

Chinese subjects with impaired FPG have a significantly elevated risk of having an intermediate or high SYNTAX score, indicating a risk of severe coronary artery lesions. Subjects with known or previously unknown T2DM may have severe coronary artery lesions. These findings suggest the importance of achieving better glycemic control in order to prevent coronary atherosclerosis and improve the cardiovascular prognosis.

Timed Bromocriptine-QR Therapy Reduces Progression of Cardiovascular Disease and Dysglycemia in Subjects with Well-Controlled Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes (T2DM) patients, including those in good glycemic control, have an increased risk of cardiovascular disease (CVD). Maintaining good glycemic control may reduce long-term CVD risk. However, other risk factors such as elevated vascular sympathetic tone and/or endothelial dysfunction may be stronger potentiators of CVD. This study evaluated the impact of bromocriptine-QR, a sympatholytic dopamine D2 receptor agonist, on progression of metabolic disease and CVD in T2DM subjects in good glycemic control (HbA1c ≤ 7.0%).

METHODS

1834 subjects (1219 bromocriptine-QR; 615 placebo) with baseline HbA1c ≤ 7.0% derived from the Cycloset Safety Trial (this trial is registered with ClinicalTrials.gov Identifier: NCT00377676), a 12-month, randomized, multicenter, placebo-controlled, double-blind study in T2DM, were evaluated. Treatment impact upon a prespecified composite CVD endpoint (first myocardial infarction, stroke, coronary revascularization, or hospitalization for angina/congestive heart failure) and the odds of losing glycemic control (HbA1c >7.0% after 52 weeks of therapy) were determined.

RESULTS

Bromocriptine-QR reduced the CVD endpoint by 48% (intention-to-treat; HR: 0.52 [0.28-0.98]) and 52% (on-treatment analysis; HR: 0.48 [0.24-0.95]). Bromocriptine-QR also reduced the odds of both losing glycemic control (OR: 0.63 (0.47-0.85), p = 0.002) and requiring treatment intensification to maintain HbA1c ≤ 7.0% (OR: 0.46 (0.31-0.69), p = 0.0002).

CONCLUSIONS

Bromocriptine-QR therapy slowed the progression of CVD and metabolic disease in T2DM subjects in good glycemic control.

Understanding the type 2 diabetes mellitus and cardiovascular disease risk paradox

Patients with diabetes have approximately a 2-fold increase in the risk for coronary heart disease, stroke, and death from vascular causes compared with patients who do not have diabetes. Interventions targeted at modifiable risk factors, such as smoking cessation and management of hypertension and dyslipidemia, reduce the risk of cardiovascular disease (CVD) in patients with type 2 diabetes mellitus (T2DM). Paradoxically, large randomized studies have failed to conclusively show that intensively lowering glucose reduces CVD event rates in patients with T2DM, despite pathophysiologic and epidemiologic evidence suggesting that hyperglycemia contributes to CVD. Although initiation of intensive glycemic control early in the disease course may be associated with a reduction in the long-term risk of cardiovascular (CV) events, this approach in those with long-standing or complicated T2DM is not of clear benefit and may even be harmful in some. Failure to mitigate risk with antihyperglycemic therapy and the potential for some treatments to increase CVD risk underlies a treatment paradox. New glucose-lowering therapies are now subject to close scrutiny for CV safety before and after drug approval. Results from the first trials designed to meet the recent CV regulatory requirements have shown no increased risk of major adverse CV events but also no CV benefit from dipeptidyl peptidase-4 inhibitor therapy, as well as a potentially increased risk of hospitalization for heart failure. Conclusive evidence of CV risk reduction with glucose-lowering therapy is still lacking and scrutiny of additional agents is necessary. Type 2 diabetes mellitus is a heterogeneous disease, for which patient-centered, individualized care, and goal-setting is appropriate. Interventions that focus on the management of CV risk factors and glucose lowering with medications that are not cardiotoxic represent an optimal and attainable treatment approach.

Effect of LX4211 on glucose homeostasis and body composition in preclinical models

Treatments that lower blood glucose levels and body weight should benefit patients with type 2 diabetes mellitus (T2DM). We developed LX4211 [(2S,3R,4R,5S,6R)-2-(4-chloro-3-(4-ethoxybenzyl)phenyl)-6-(methylthio)tetrahydro-2H-pyran-3,4,5-triol], an orally available small molecule that decreases postprandial glucose excursions by inhibiting intestinal sodium/glucose cotransporter 1 (SGLT1) and increases urinary glucose excretion (UGE) by inhibiting renal SGLT2. In clinical studies of patients with T2DM, LX4211 appears to act through dual SGLT1/SGLT2 inhibition to improve glycemic control and promote weight loss. Here, we present preclinical studies that explored the ability of LX4211 to improve glycemic control and promote weight loss. We found that 1) LX4211 inhibited in vitro glucose transport mediated by mouse, rat, and dog SGLT1 and SGLT2; 2) a single daily LX4211 dose markedly increased UGE for >24 hours in mice, rats, and dogs; and 3) in the KK.Cg-Ay/J heterozygous (KKA(y)) mouse model of T2DM, LX4211 lowered A1C and postprandial glucose concentrations while increasing postprandial glucagon-like peptide 1 concentrations. Also, long-term LX4211 treatment 1) decreased oral glucose tolerance test (OGTT) glucose excursions, increased OGTT 30-minute insulin concentrations and increased pancreatic insulin content in KKA(y) mice; and 2) decreased weight gain in dogs and rats but not in KKA(y) mice while increasing food consumption in dogs, rats, and KKA(y) mice; in these KKA(y) mice, calories lost through UGE were completely offset by calories gained through hyperphagia. These findings suggest that LX4211 improves glycemic control by dual SGLT1/SGLT2 inhibition in mice as in humans, and that the LX4211-mediated weight loss observed in patients with T2DM may be attenuated by LX4211-mediated hyperphagia in some of these individuals.

Sudden cardiac death and diabetes mellitus

Sudden cardiac death (SCD) affects a significant percentage of diabetic patients. SCD in these patients can be due to several factors, such as diastolic dysfunction, heart failure, altered platelet function, inflammation, sympathetic nervous stimulation and other factors. In the present review, we discuss the association between diabetes mellitus and SCD.

A role for diallyl trisulfide in mitochondrial antioxidative stress contributes to its protective effects against vascular endothelial impairment

Persistent hyperglycemia increases a systemic oxidative stress, causing the onset of vascular endothelial dysfunction and atherosclerosis. Diallyl trisulfide (DAT), a natural organosulfur compound in garlic, has been reported to have actions of dilating blood vessels and antibacteria, etc. In this study, models of obese diabetic rat in vivo and high glucose concentration (HG)-induced endothelial cell injury in vitro were used to investigate the protective effects of DAT on vascular endothelial injury and its underlying mechanisms. In the in vivo model, the obese diabetic rats were injected venously with DAT (5.0 mg kg(-1)d(-1)) and Vitamin E (1.0 mg kg(-1)d(-1)) respectively, once daily for 7 consecutive days. In the in vitro model, HG-injured HUVEC were treated with or without DAT (25 µmol L(-1), 50 µmol L(-1), 100 µmol L(-1)) or Vitamin E (25 µmol L(-1)) respectively for 24h. The extents of vascular endothelial injury and protective effects of DAT were evaluated. The results both in vivo and in vitro displayed that DAT-treatment significantly attenuated the endothelial cell impairments. Besides, DAT-treatment markedly decreased the levels of malondialdehyde (MDA) and reactive oxygen species, whereas elevated the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in mitochondrium. Moreover, DAT-treatment considerably improved mitochondrial respiration function. Taken together, our results suggest that DAT protects vascular endothelium from HG or hyperglycemia induced-injury by reducing mitochondrial oxidative stress. The findings provide a novel insight for DAT to potentially treat the oxidative stress diseases, i.e., atherosclerosis, diabetes, and neurodegenerative diseases.

Glutathione prevents free fatty acids-induced oxidative stress and apoptosis in human brain vascular endothelial cells through Akt pathway

AIMS

The damage of human brain vascular endothelial cells (HBVECs) is the key pathogenesis of diabetes-associated cerebral vascular complications. The aim of this study was to elucidate the effects of glutathione (GSH) on free fatty acids (FFAs)-induced HBVECs apoptosis, oxidative stress, and the involved possible signaling pathway.

METHODS

After culturing HBVECs for 72 h with GSH and FFAs, we determined cell proliferation by CCK8, detected apoptosis by caspase-3 and Annexin V-FITC/PI staining, and judged oxygen stress by determining the reactive oxygen species (ROS) and the mitochondrial membrane potential (MMP). We investigated whether the Akt pathway was involved in FFAs-induced signaling pathway alteration and whether GSH influenced the above effects.

RESULTS

After being cultured in 200 μM FFAs for 72 h, the HBVECs proliferation significantly decreased; HBVECs apoptosis increased; the ROS levels increased; and the HBVECs MMP subsequently decreased. FFAs induced a significant decrease in phosphorylated active Akt. These alterations were obviously prevented when 1 mM GSH was added to culture medium containing FFAs, and the above effects of GSH were blocked by Akt inhibitor.

CONCLUSION

GSH may prevent FFAs-induced HBVECs damage, oxidative stress, and apoptosis through activating the Akt pathway.

Hyperglycemia impairs atherosclerosis regression in mice

Diabetic patients are known to be more susceptible to atherosclerosis and its associated cardiovascular complications. However, the effects of hyperglycemia on atherosclerosis regression remain unclear. We hypothesized that hyperglycemia impairs atherosclerosis regression by modulating the biological function of lesional macrophages. HypoE (Apoe(h/h)Mx1-Cre) mice express low levels of apolipoprotein E (apoE) and develop atherosclerosis when fed a high-fat diet. Atherosclerosis regression occurs in these mice upon plasma lipid lowering induced by a change in diet and the restoration of apoE expression. We examined the morphological characteristics of regressed lesions and assessed the biological function of lesional macrophages isolated with laser-capture microdissection in euglycemic and hyperglycemic HypoE mice. Hyperglycemia induced by streptozotocin treatment impaired lesion size reduction (36% versus 14%) and lipid loss (38% versus 26%) after the reversal of hyperlipidemia. However, decreases in lesional macrophage content and remodeling in both groups of mice were similar. Gene expression analysis revealed that hyperglycemia impaired cholesterol transport by modulating ATP-binding cassette A1, ATP-binding cassette G1, scavenger receptor class B family member (CD36), scavenger receptor class B1, and wound healing pathways in lesional macrophages during atherosclerosis regression. Hyperglycemia impairs both reduction in size and loss of lipids from atherosclerotic lesions upon plasma lipid lowering without significantly affecting the remodeling of the vascular wall.

Vitamin E in the prevention of cardiovascular disease: the importance of proper patient selection

Vitamin E is a naturally occurring fat-soluble antioxidant which has been proposed as a treatment for both primary and secondary protection against cardiovascular (CV) events. Promising data from observational epidemiological studies associating higher vitamin E dietary intake with lower risk of CV events have not been validated in randomized controlled clinical trials assessing the effect of vitamin E on CV outcomes. While the pendulum of medical opinion has swung to suggest that high dose vitamin E supplements have no place in the treatment and prevention of CV disease, new data is emerging that allows identification of a specific target population for this treatment, namely patients with diabetes mellitus and the haptoglobin genotype 2-2. This review details the scientific basis and clinical evidence related to the effect of vitamin E on CV outcomes, and the importance of proper patient selection in gaining therapeutic benefit from this intervention.

The vascular smooth muscle cell: a therapeutic target in Type 2 diabetes?

The rising epidemic of T2DM (Type 2 diabetes mellitus) worldwide is of significant concern. The inherently silent nature of the disease in its early stages precludes early detection; hence cardiovascular disease is often established by the time diabetes is diagnosed. This increased cardiovascular risk leads to significant morbidity and mortality in these individuals. Progressive development of complications as a result of previous exposure to metabolic disturbances appears to leave a long-lasting impression on cells of the vasculature that is not easily reversed and is termed 'metabolic memory'. SMCs (smooth muscle cells) of blood vessel walls, through their inherent ability to switch between a contractile quiescent phenotype and an active secretory state, maintain vascular homoeostasis in health and development. This plasticity also confers SMCs with the essential capacity to adapt and remodel in pathological states. Emerging clinical and experimental studies propose that SMCs in diabetes may be functionally impaired and thus contribute to the increased incidence of macrovascular complications. Although this idea has general support, the underlying molecular mechanisms are currently unknown and hence are the subject of intense research. The aim of the present review is to explore and evaluate the current literature relating to the problem of vascular disease in T2DM and to discuss the critical role of SMCs in vascular remodelling. Possibilities for therapeutic strategies specifically at the level of T2DM SMCs, including recent novel advances in the areas of microRNAs and epigenetics, will be evaluated. Since restoring glucose control in diabetic patients has limited effect in ameliorating their cardiovascular risk, discovering alternative strategies that restrict or reverse disease progression is vital. Current research in this area will be discussed.

High-intensity endurance training results in faster vessel-specific rate of vasorelaxation in type 1 diabetic rats

This study examined the effects of 6 weeks of moderate- (MD) and high-intensity endurance training (HD) and resistance training (RD) on the vasorelaxation responsiveness of the aorta, iliac, and femoral vessels in type 1 diabetic (D) rats. Vasorelaxation to acetylcholine was modeled as a mono-exponential function. A potential mediator of vasorelaxation, endothelial nitric oxide synthase (e-NOS) was determined by Western blots. Vessel lumen-to-wall ratios were calculated from H&E stains. The vasorelaxation time-constant (τ) (s) was smaller in control (C) (7.2±3.7) compared to D (9.1±4.4) and it was smaller in HD (5.4±1.5) compared to C, D, RD (8.3±3.7) and MD (8.7±3.8) (p<0.05). The rate of vasorelaxation (%·s⁻¹) was larger in HD (2.7±1.2) compared to C (2.0±1.2), D (2.0±1.5), RD (2.0±1.0), and MD (2.0±1.2) (p<0.05). τ vasorelaxation was smaller in the femoral (6.9±3.7) and iliac (6.9±4.7) than the aorta (9.0±5.0) (p<0.05). The rate of vasorelaxation was progressively larger from the femoral (3.1±1.4) to the iliac (2.0±0.9) and to the aorta (1.3±0.5) (p<0.05). e-NOS content (% of positive control) was greater in HD (104±90) compared to C (71±64), D (85±65), RD (69±43), and MD (76±44) (p<0.05). e-NOS normalized to lumen-to-wall ratio (%·mm⁻¹) was larger in the femoral (11.7±11.1) compared to the aorta (3.2±1.9) (p<0.05). Although vasorelaxation responses were vessel-specific, high-intensity endurance training was the most effective exercise modality in restoring the diabetes-related loss of vascular responsiveness. Changes in the vasoresponsiveness seem to be endothelium-dependent as evidenced by the greater e-NOS content in HD and the greater normalized e-NOS content in the smaller vessels.

Effect of low dose mineralocorticoid receptor antagonist eplerenone on glucose and lipid metabolism in healthy adult males

Mineralocorticoid Receptor (MR) activation is involved in blood pressure regulation and the pathogenesis of cardiovascular diseases, such as cardiac fibrosis, vascular inflammation and arterial aging. Recent investigations suggest a role for MR activation in metabolic dysregulation.

OBJECTIVE

To test the effect of MR blockade on basal and postprandial glucose and lipid levels after a meal high in fat and glucose in healthy males.

SUBJECTS AND METHODS

A prospective, self-controlled study was performed in 13 healthy adult males aged 18-45years. Blood was drawn before, 2h, and 4h after a high fat/high glucose meal (50g fat, 75g glucose), followed by low-dose eplerenone treatment (50mg daily) for 14days. Subjects returned for a second high fat/high glucose meal after the medication period. Basal and postprandial blood glucose and lipid levels were compared before and after eplerenone treatment.

RESULTS

Eplerenone treatment affected neither basal nor postprandial glucose and lipid levels in our study population.

CONCLUSION

Our results suggest that low-dose, non-blood pressure-affecting, MR blockade does not alter postprandial lipid and glucose homeostasis in healthy adult subjects.

Vessel-specific rate of vasorelaxation is slower in diabetic rats

The rate of adjustment of endothelium-dependent vasorelaxation was examined in the aorta, iliac and femoral arteries of eight control and eight diabetic rats with and without supplementation with vitamin C. Vessels were constricted using 10(-5) M phenylephrine (PE) and relaxed with 10(-4) M acetylcholine (ACh condition) or 10(-4) M ACh plus 10(-4) M vitamin C (ACh + vitamin C condition) in a myography system. Vasorelaxation was modelled as a mono-exponential function using a non-linear regression analysis. The adjustment (τ) of vasorelaxation was faster in control (6.6 ± 3.2 s) compared to diabetic rats (8.4 ± 3.4 s) (p < 0.05). The time-to-steady-state tended to be shorter in control (32.0 ± 13.9 s) compared to diabetic rats (38.0 ± 15.0 s) (p = 0.1). ACh + vitamin C did not speed the vasorelaxation response. The τ for vasorelaxation was shorter in the femoral (6.5 ± 2.7 s) and iliac (6.8 ± 2.5 s) compared to the aorta (9.2 ± 4.2 s) (p < 0.05). The rate of vasorelaxation was greater in the femoral (3.2 ± 1.4%·s(-1)) compared to the iliac (2.0 ± 1.0%·s(-1)) and aorta (1.1 ± 0.4%·s(-1)) in both groups and in the iliac compared to the aorta (p < 0.05) in the control group. In conclusion, the vasorelaxation response was vessel specific with a slower rate of adjustment in diabetic compared to control animals.

Diabetes and cardiovascular disease: changing the focus from glycemic control to improving long-term survival

Diabetes mellitus (DM) is the fifth-leading cause of death worldwide and contributes to leading causes of death, cancer and cardiovascular disease, including CAD, stroke, peripheral vascular disease, and other vascular disease. While glycemic management remains a cornerstone of DM care, the co-management of hypertension, atherosclerosis, cardiovascular risk reduction, and prevention of long-term consequences associated with DM are now well recognized as essential to improve long-term survival. Clinical trial evidence substantiates the importance of glycemic control, low-density cholesterol-lowering therapy, blood pressure lowering, control of albuminuria, and comprehensive approaches targeting multiple risk factors to reduce cardiovascular risk. This article presents a review of the role of DM in the pathogenesis of atherosclerosis and cardiac dysfunction, recent evidence on the degree of glycemic control and mortality, and available evidence for a multifaceted approach to improve long-term outcomes for patients.

Interferon regulatory factor-1 as a positive regulator for high glucose-induced proliferation of vascular smooth muscle cells

High glucose-induced proliferation of vascular smooth muscle cells (VSMCs) plays an important role in the development of diabetic vascular diseases. However, molecular mediators responding for the proliferation of VSMCs remain to be determined. In this study, VSMCs were isolated from the rat thoracic aorta, and two cell models with Irf-1 knockdown and overexpression were established by transfecting cells with pGCsi-FU-Irf-1 and pGC-FU-Irf-1, respectively. Subsequently, high glucose was added to cells to induce proliferation. Proliferation assays were performed to see whether Irf-1 was involved in high glucose-induced proliferation of VSMCs. In addition, the expression of Irf-1 was detected in VSMCs stimulated with high glucose and the thoracic aorta of diabetic rats to confirm the relationship between Irf-1 expression and the proliferation of hyperglycemia-dependent VSMCs. The results showed that Irf-1 expression was significantly higher in the thoracic aorta of diabetic rats and VSMCs stimulated with high glucose than that in nondiabetic rats and untreated cells. Overexpression of Irf-1 accelerated the proliferation of VSMCs, and down-regulation of Irf-1 expression significantly depressed the proliferative ability of VSMCs under high-glucose conditions, indicating that Irf-1 was a positive regulator for high glucose-induced proliferation of VSMCs. It could be presumed that Irf-1 is associated with the accelerated proliferation of VSMCs in diabetic vascular diseases and may prove to be a potential target gene for disease treatment.

Glucose control in diabetes: which target level to aim for?

The most important goal in the treatment of patients with diabetes is to lower the risk of long-term diabetes complications. Hyperglycaemia is the most important risk factor for microvascular complications in diabetes, but, in addition to hyperglycaemia, several other risk factors, particularly dyslipidaemia, elevated blood pressure and smoking, also determine the risk of macrovascular complications. In this review, we present evidence from longitudinal population-based studies that hyperglycaemia is an important risk factor for long-term complications of diabetes and discuss the results from clinical trials of the effects of the treatment of hyperglycaemia on the prevention of long-term micro- and macrovascular complications in type 1 and type 2 diabetes. An HbA(1c) target of <7.0% for the treatment of diabetes is generally accepted on the basis of evidence from several trials, whereas a target of <6.5% may be reasonable for patients with a short duration of type 2 diabetes and without extensive atherosclerosis.

Endothelial cell and platelet bioenergetics: effect of glucose and nutrient composition

It has been suggested that cells that are independent of insulin for glucose uptake, when exposed to high glucose or other nutrient concentrations, manifest enhanced mitochondrial substrate oxidation with consequent enhanced potential and generation of reactive oxygen species (ROS); a paradigm that could predispose to vascular complications of diabetes. Here we exposed bovine aortic endothelial (BAE) cells and human platelets to variable glucose and fatty acid concentrations. We then examined oxygen consumption and acidification rates using recently available technology in the form of an extracellular oxygen and proton flux analyzer. Acute or overnight exposure of confluent BAE cells to glucose concentrations from 5.5 to 25 mM did not enhance or change the rate of oxygen consumption (OCR) under basal conditions, during ATP synthesis, or under uncoupled conditions. Glucose also did not alter OCR in sub-confluent cells, in cells exposed to low serum, or in cells treated with added pyruvate. Likewise, overnight exposure to fatty acids of varying saturation had no such effects. Overnight exposure of BAE cells to low glucose concentration decreased maximal uncoupled respiration, but not basal or ATP related oxygen consumption. Labeled glucose oxidation to CO₂ increased, but only marginally after high glucose exposure while oleate oxidation to CO₂ decreased. Overnight exposure to linolenic acid, but not oleic or linoleic acid increased extracellular acidification consistent with enhanced glycolytic metabolism. We were unable to detect an increase in production of reactive oxygen species (ROS) from BAE cells exposed to high medium glucose. Like BAE cells, exposure of human platelets to glucose did not increase oxygen consumption. As opposed to BAE cells, platelet mitochondria demonstrate less respiratory reserve capacity (beyond that needed for basal metabolism). Our data do not support the concept that exposure to high glucose or fatty acids accelerates mitochondrial oxidative metabolism in endothelial cells or platelets.

Is it time to screen for the haptoglobin genotype to assess the cardiovascular risk profile and vitamin E therapy responsiveness in patients with diabetes?

Diabetes mellitus (DM) carries an increased risk for cardiovascular complications. Haptoglobin (Hp) is an abundant plasma protein with an antioxidant function by virtue of its ability to block the oxidative activity of extracorpuscular hemoglobin. There exist two common functional alleles at the Hp genetic locus, denoted 1 and 2, with three Hp genotypes (Hp 1-1, 2-1, and 2-2). The Hp protein expressed in Hp 2-2 individuals is markedly inferior in protecting against hemoglobin-induced oxidative stress. Hp 2-2 DM individuals have been shown to be at increased risk for the development of diabetes complications, particularly diabetic cardiovascular disease (CVD). We review the biological mechanisms underlying the interaction between the Hp genotype and DM on CVD and the accumulating evidence in favor of Hp genotyping all individuals with DM and providing antioxidant vitamin E supplementation specifically to Hp 2-2 DM individuals to reduce their CVD morbidity and mortality.