Microvascular endothelial function in subjects with Type 2 diabetes and the effect of lipid-lowering therapy

Benefits and harms of fibrate therapy in patients with type 2 diabetes: a systematic review and meta-analysis

PURPOSE

This systematic review aimed to evaluate the benefits and harms of fibrate therapy, alone or in combination with statins, in adult patients with type 2 diabetes (T2D).

METHODS

A comprehensive search was conducted in six databases, from inception to January 27, 2022. Clinical trials that compared fibrate therapy with other lipid-lowering interventions or placebo were included. Outcomes of interest comprised cardiovascular (CV) events, complications of T2D, metabolic profile, and adverse events. Random-effects meta-analyses were performed to estimate mean differences (MD) and risk ratios (RR), alongside 95% confidence intervals (CI).

RESULTS

A total of 25 studies were included, six comparing fibrates against statins, 11 against placebo, and eight evaluating the combination of fibrates with statins. Overall risk of bias was rated as moderate, and most outcomes rendered low confidence per GRADE approach. Fibrates showed reduction of serum triglycerides (TGs) (MD -17.81, CI -33.92 to -1.69) and a marginal increase of high-density lipoprotein cholesterol (HDL-c) (MD: 1.60, CI 0.29 to 2.90) in adults with T2D, but no differences were found in CV events when compared to statin therapy (RR 0.99, CI 0.76 to 1.09). When used in combination with statins, no major differences were exhibited regarding lipid profile and CV outcomes. Adverse events were comparable between fibrate and statin monotherapies (e.g., RR of 1.03 for rhabdomyolysis, and 0.90 for gastrointestinal events).

CONCLUSIONS

Fibrate therapy in patients with T2D results in a marginal improvement of TGs and HDL-c but without reducing the risk of CV events and mortality. Their use should be reserved for very specific scenarios after a deliberative dialogue between patients and clinicians regarding their benefits and harms.

Cerivastatin for lowering lipids

BACKGROUND

Cerivastatin was the most potent statin until it was withdrawn from the market due to a number of fatalities due to rhabdomyolysis, however, the dose-related magnitude of effect of cerivastatin on blood lipids is not known.

OBJECTIVES

Primary objective To quantify the effects of various doses of cerivastatin on the surrogate markers: LDL cholesterol, total cholesterol, HDL cholesterol and triglycerides in children and adults with and without cardiovascular disease. The aim of this review is to examine the pharmacology of cerivastatin by characterizing the dose-related effect and variability of the effect of cerivastatin on surrogate markers. Secondary objectives To quantify the effect of various doses of cerivastatin compared to placebo on withdrawals due to adverse effects. To compare the relative potency of cerivastatin with respect to fluvastatin, atorvastatin and rosuvastatin for LDL cholesterol, total cholesterol, HDL cholesterol and triglycerides.

SEARCH METHODS

The Cochrane Hypertension Information Specialist searched the following databases for RCTs up to March 2019: CENTRAL (2019, Issue 3), Ovid MEDLINE, Ovid Embase, the WHO International Clinical Trials Registry Platform, and ClinicalTrials.gov.We also searched the European Patent Office, FDA.gov, and ProQuest Dissertations & Theses, and contacted authors of relevant papers regarding further published and unpublished work. The searches had no language restrictions.

SELECTION CRITERIA

RCTs and controlled before-and-after studies evaluating the dose response of different fixed doses of cerivastatin on blood lipids over a duration of three to 12 weeks in participants of any age with and without cardiovascular disease.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility criteria for trials to be included and extracted data. We entered data from RCTs and controlled before-and-after studies into Review Manager 5 as continuous and generic inverse variance data respectively. We collected information on withdrawals due to adverse effects from the RCTs. We assessed all trials using the 'Risk of bias' tool under the categories of sequence generation, allocation concealment, blinding, incomplete outcome data, selective reporting, and other potential biases.

MAIN RESULTS

Fifty trials (19 RCTs and 31 before-and-after studies) evaluated the dose-related efficacy of cerivastatin in 12,877 participants who had their LDL cholesterol measured. The participants were of any age with and without cardiovascular disease and the trials studied cerivastatin effects within a treatment period of three to 12 weeks. Cerivastatin 0.025 mg/day to 0.8 mg/day caused LDL cholesterol decreases of 11.0% to 40.8%, total cholesterol decreases of 8.0% to 28.8% and triglyceride decreases of 9.0% to 21.4%. We judged the certainty of evidence for these effects to be high. Log dose-response data over doses of 2.5 mg to 80 mg revealed strong linear dose-related effects on LDL cholesterol, total cholesterol and triglycerides. When compared to fluvastatin, atorvastatin and rosuvastatin, cerivastatin was about 250-fold more potent than fluvastatin, 20-fold more potent than atorvastatin and 5.5-fold more potent than rosuvastatin at reducing LDL cholesterol; 233-fold more potent than fluvastatin, 18-fold more potent than atorvastatin and six-fold more potent than rosuvastatin at reducing total cholesterol; and 125-fold more potent than fluvastatin, 11-fold more potent than atorvastatin and 13-fold more potent than rosuvastatin at reducing triglycerides. There was no dose-related effect of cerivastatin on HDL cholesterol, but overall cerivastatin increased HDL cholesterol by 5%. There was a high risk of bias for the outcome withdrawals due to adverse effects, but a low risk of bias for the lipid measurements. Withdrawals due to adverse effects were not different between cerivastatin and placebo in 11 of 19 of these short-term trials (risk ratio 1.09, 95% confidence interval 0.68 to 1.74).

AUTHORS' CONCLUSIONS

The LDL cholesterol, total cholesterol, and triglyceride lowering effect of cerivastatin was linearly dependent on dose. Cerivastatin log dose-response data were linear over the commonly prescribed dose range. Based on an informal comparison with fluvastatin, atorvastatin and rosuvastatin, cerivastatin was about 250-fold more potent than fluvastatin, 20-fold more potent than atorvastatin and 5.5-fold more potent than rosuvastatin in reducing LDL cholesterol, and 233-fold greater potency than fluvastatin, 18-fold greater potency than atorvastatin and six-fold greater potency than rosuvastatin at reducing total cholesterol. This review did not provide a good estimate of the incidence of harms associated with cerivastatin because of the short duration of the trials and the lack of reporting of adverse effects in 42% of the RCTs.

Relationships Between Type 2 Diabetes, Neuropathy, and Microvascular Dysfunction: Evidence From Patients With Cryptogenic Axonal Polyneuropathy

OBJECTIVE

This study investigated whether the relationship between neuropathy and microvascular dysfunction in patients with type 2 diabetes is independent of diabetes-related factors. For this purpose, we compared skin microvascular function in patients with type 2 diabetes with that of patients with cryptogenic axonal polyneuropathy (CAP), a polyneuropathy of unknown etiology.

RESEARCH DESIGN AND METHODS

Cross-sectional information was collected from 16 healthy controls (HCs), 16 patients with CAP, 15 patients with type 2 diabetes with polyneuropathy (DPN), and 11 patients with type 2 diabetes without polyneuropathy. Axonal degeneration was assessed with skin biopsy and nerve conduction studies. Microvascular skin vasodilation was measured using laser Doppler fluxmetry combined with iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP).

RESULTS

Patients with CAP and DPN demonstrated a similar decrease in intraepidermal nerve fiber density and sural sensory nerve action potential compared with HCs. The vasodilator response to ACh was similar among patients with CAP (relative mean difference based on log values 13.3%; 95% CI -35.0 to 97.7%; P = 0.652) but was lower in the patients with diabetes with neuropathy (157.5%; 42.0-366.7%; P = 0.003) and without neuropathy (174.2%; 44.2-421.3%; P = 0.003) compared with HCs. No significant differences were found between the groups of patients with diabetes (P = 0.845). The vasodilator response to SNP was not significantly different among the groups (P = 0.082).

CONCLUSIONS

In this study, endothelium-dependent vasodilation was reduced in patients with type 2 diabetes regardless of the presence of polyneuropathy, whereas microvascular vasodilation was normal in patients with CAP. These data suggest that in type 2 diabetes, neuropathy does not contribute to impaired microvascular endothelium-dependent vasodilation and vice versa. In addition, this study suggests that impaired microvascular vasodilation does not contribute to CAP.

Pleiotropic effects of statins

Statins or 3-hydroxy-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors not only prevents the synthesis of cholesterol biosynthesis but also inhibits the synthesis of essential isoprenoid intermediates such as farnesyl pyrophosphate, geranylgeranyl pyrophosphate, isopentanyl adenosine, dolichols and polyisoprenoid side chains of ubiquinone, heme A, and nuclear lamins. These isoprenoid intermediates are required for activation of various intracellular/signaling proteins- small guanosine triphosphate bound protein Ras and Ras-like proteins like Rho, Rab, Rac, Ral, or Rap which plays an indispensible role in multiple cellular processes. Reduction of circulating isoprenoids intermediates as a result of HMG CoA reductase inhibition by statins prevents activation of these signalling proteins. Hence, the multiple effects of statins such as antiinflammatory effects, antioxidant effects, antiproliferative and immunomodulatory effects, plaque stability, normalization of sympathetic outflow, and prevention of platelet aggregation are due to reduction of circulating isoprenoids and hence inactivation of signalling proteins. These multiple lipid-independent effects of statins termed as statin pleiotropy would potentially open floodgates for research in multiple treatment domains catching attentions of researchers and clinician across the globe.

A pilot study of ezetimibe vs. atorvastatin for improving peripheral microvascular endothelial function in stable patients with type 2 diabetes mellitus

BACKGROUND

Elevated cholesterol in type 2 diabetes mellitus (DM) can cause endothelial dysfunction. An effective clinical therapy to improve endothelial dysfunction remains to be established. Different cardiovascular actions between treatments for the inhibition of cholesterol absorption and the suppression of cholesterol synthesis for achieving improvement in endothelial function are unknown in DM.

METHODS

Stable patients with type 2 DM and mildly elevated low-density lipoprotein cholesterol were enrolled. We evaluated peripheral microvascular endothelial function using reactive hyperemia peripheral arterial tonometry (RH-PAT) examination and calculated a natural logarithmic transformed value for the RH-PAT index (LnRHI). We randomly assigned 33 patients to each monotherapy: cholesterol synthesis suppression using atorvastatin (5 mg/day, n=16) or cholesterol absorption inhibition using ezetimibe (10 mg/day, n=17). Patients were prospectively followed for 6 months. Serum lipids and LnRHI were repeatedly examined before and after each therapy.

RESULTS

LDL significantly decreased in both groups, but the percent changes of LDL showed a greater decrease in the atorvastatin group compared with the ezetimibe group (-34.5±7.8% vs. -21.9±9.6%, p<0.01). Serum levels of non-esterified free fatty acids (NEFA) significantly decreased in the ezetimibe group but not in the atorvastatin group (ezetimibe group: 561.1±236.8 to 429.7±195.9, p<0.01; atorvastatin group: 538.8±319.5 to 520.2±227.3, p=0.75). The percent decrease in NEFA was significantly greater in the ezetimibe group compared with the atorvastatin group (-19.9±27.4% vs. 11.3±44.1%, p<0.05). LnRHI showed a significant increase in the ezetimibe group but not in the atorvastatin group (ezetimibe group: 0.471±0.157 to 0.678±0.187, p<0.01; atorvastatin group: 0.552±0.084 to 0.558±0.202, p=0.64). The percent changes in LnRHI were significantly greater in the ezetimibe group compared with the atorvastatin group (63.3±89.2% vs. 7.4±41.2%, p<0.05).

CONCLUSIONS

In patients with type 2 DM, ezetimibe monotherapy significantly reduced LDL and NEFA, and improved peripheral microvascular endothelial dysfunction. Ezetimibe could potentially exhibit beneficial effects on lipid disorders and microvascular endothelial dysfunction in DM.

Diabetes mellitus-associated vascular impairment: novel circulating biomarkers and therapeutic approaches

It is widely accepted that diabetes mellitus (DM) impairs endothelial nitric oxide synthase activity as well as enhances the production of reactive oxygen species, thus resulting in diminished nitric oxide bioavailability and the consequent pro-atherogenetic alterations. Important biomarkers of the vasculature are related to endothelial dysfunction, to inflammatory and coagulation processes, and to oxidative stress in DM. Several therapeutic strategies might exert favorable effects on the vasculature of diabetic patients, such as insulin analogues, antihypertensive agents, statins, and hypoglycemic agents, whereas in spite of the prominent role of oxidative stress in diabetes, antioxidant therapy remains controversial. The use of specific biomarkers related to vascular function could be a useful therapeutic approach in such patients.

Safety and efficacy of statin treatment alone and in combination with fibrates in patients with dyslipidemia: a meta-analysis

BACKGROUND

Dyslipidemia is a major risk factor for cardiovascular disease and is treated with many effective lipid-lowering agents. Statins are often used alone or in combination with fibrates. Combination therapy is more effective due to their comparative actions, but the increased incidence of side effects should be considered carefully.

RESEARCH DESIGN AND METHODS

A meta-analysis of published data was conducted to compare the safety and efficacy of statins alone versus statins plus fibrates in patients with dyslipidemia. In total, nine articles were assessed for efficacy analysis and ten articles were assessed for safety analysis.

RESULTS

In the efficacy analysis, a combination of statins and fibrates provided significantly greater reductions in total cholesterol (SE = 0.430; 95% CI 0.315-0.545), LDL cholesterol (SE = 0.438; 95% CI 0.321-0.555) and triglycerides (SE = 0.747; 95% CI 0.618-0.876), and a significantly greater increase in HDL cholesterol (SE = 0.594; 95% CI 0.473-0.715) than treatment with statins alone. In the safety analysis, treatment with statins alone was associated with a significant reduction in the numbers of total adverse events (RR = 0.665; 95% CI 0.539-0.819), liver-related adverse events (RR = 0.396; 95% CI 0.206-0.760) and kidney-related adverse events (RR = 0.146; 95% CI 0.075-0.285).

CONCLUSION

We suggest that treatment with statins plus fibrates provides clinical benefits over treatment with statins alone but increased risks, especially of hepatic or renal side effects, should be monitored carefully.

Fenofibrate ameliorates insulin resistance, hypertension and novel oxidative stress markers in patients with metabolic syndrome

SUMMARY

OBJECTIVE

The benefits of fenofibrate, a peroxisome proliferator-activated receptor α agonist, against cardiovascular risk factors have been established. To clarify the underlying mechanisms of these benefits, we examined the effects of fenofibrate on insulin resistance, hypertension, inflammation, oxidative stress and coagulation markers in patients with metabolic syndrome.

METHODS

Eleven Japanese patients with metabolic syndrome underwent physical examinations and blood tests before and after treatment with fenofibrate 200 mg daily for 8 weeks.

RESULTS

Fenofibrate significantly decreased systolic blood pressure, pulse wave velocity, serum insulin, insulin resistance (calculated from the homeostasis model assessment), total cholesterol, triglyceride, remnant-like particles cholesterol, uric acid, D-dimer, fibrinogen, serum amyloid A/low-density lipoprotein (LDL) and apoA1/LDL levels. It also significantly increased levels of high molecular weight adiponectin, thrombomodulin and high-density lipoprotein cholesterol in these patients. Plasminogen activator inhibitor-1, C-reactive protein, fasting plasma glucose and thrombin-antithrombin complex levels did not change.

LIMITATION

Small sample size.

CONCLUSION

Short-term fenofibrate administration not only improved lipid profiles, but also ameliorated insulin resistance, hypertension and oxidative stress markers in patients with metabolic syndrome, suggesting that fenofibrate can decrease the risk of arteriosclerosis through various pathways.

Endothelial dysfunction in diabetes: pathogenesis, significance, and treatment

Type 2 diabetes (T2D) markedly increases the risk of cardiovascular disease. Endothelial dysfunction (ED), an early indicator of diabetic vascular disease, is common in T2D and independently predicts cardiovascular risk. Although the precise pathogenic mechanisms for ED in T2D remain unclear, at inception they probably involve uncoupling of both endothelial nitric oxide synthase activity and mitochondrial oxidative phosphorylation, as well as the activation of vascular nicotinamide adenine dinucleotide phosphate oxidase. The major contributing factors include dyslipoproteinemia, oxidative stress, and inflammation. Therapeutic interventions are designed to target these pathophysiological factors that underlie ED. Therapeutic interventions, including lifestyle changes, antiglycemic agents and lipid-regulating therapies, aim to correct hyperglycemia and atherogenic dyslipidemia and to improve ED. However, high residual cardiovascular risk is seen in both research and clinical practice settings. Well-designed studies of endothelial function in appropriately selected volunteers afford a good opportunity to test new therapeutic interventions, paving the way for clinical trials and utilization in the care of the diabetic patient. However, based on the results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled low-density lipoprotein cholesterol.

Do heat events pose a greater health risk for individuals with type 2 diabetes?

Chronic medical conditions such as type 2 diabetes may alter the body's normal response to heat. Evidence suggests that the local heat loss response of skin blood flow (SkBF) is affected by diabetes-related impairments in both endothelium-dependent and non-endothelium-dependent mechanisms, resulting in lower elevations in SkBF in response to a heat or pharmacological stimulus. Thermoregulatory sweating may also be diminished by type 2 diabetes, impairing the body's ability to transfer heat from its core to the environment. Diabetes-associated co-morbidities and the medications (particularly those affecting fluid balance) required to treat these conditions may exacerbate the risk of heat-related illness by decreasing SkBF and sweating further. Unfortunately, the majority of studies measure local heat loss responses in the hands and feet and lack measures of core temperature. Therefore, the impact of these impairments on whole-body heat loss remains unknown. This review addresses heat-related vulnerability in individuals with type 2 diabetes by examining the literature related to heat loss responses in this population. Type 2 diabetes, its associated co-morbidities, and the medications required in their treatment may cause dehydration, lower SkBF, and reduced sweating, which could consequently impair thermoregulation. This effect is most evident in individuals with poor blood glucose control. Although type 2 diabetes can be associated with impairments in SkBF and sweating, more physically active individuals requiring fewer medications and having good blood glucose control may be able to tolerate heat as well as those of similar age and body composition.

Endothelial dysfunction and diabetes: effects on angiogenesis, vascular remodeling, and wound healing

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by inappropriate hyperglycemia due to lack of or resistance to insulin. Patients with DM are frequently afflicted with ischemic vascular disease or wound healing defect. It is well known that type 2 DM causes amplification of the atherosclerotic process, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. These complications ultimately lead to impairment of neovascularization and diabetic wound healing. Therapeutic angiogenesis remains an attractive treatment modality for chronic ischemic disorders including PAD and/or diabetic wound healing. Many experimental studies have identified better approaches for diabetic cardiovascular complications, however, successful clinical translation has been limited possibly due to the narrow therapeutic targets of these agents or the lack of rigorous evaluation of pathology and therapeutic mechanisms in experimental models of disease. This paper discusses the current body of evidence identifying endothelial dysfunction and impaired angiogenesis during diabetes.

Effects of fibrates on C-reactive protein concentrations: a meta-analysis of randomized controlled trials

The effects of fibrates on C-reactive protein (CRP) are controversial. This meta-analysis was conducted to synthesize the available clinical trial evidence and summarize the effects of fibrates on CRP concentrations. In addition, this study assessed the relationship between changes in CRP and lipid measures.

A systematic search was conducted of randomized controlled trials on the effects of fibrates on CRP concentrations in the PubMed, Embase and Cochrane Library Database up to January 2011. A meta-analysis was performed using a random effect model. Meta-regression analysis was employed to assess the relationships between average change in CRP and lipid profiles.

Sixteen randomized controlled trials were included in the meta-analysis. Compared with placebo, treatment with fibrates significantly decreased CRP concentrations (weighted mean difference –0.47 mg/L, 95% confidence interval –0.93 to –0.01 mg/L, p=0.046). Fibrates significantly reduced CRP concentrations in trials with a higher baseline CRP concentrations (≥3 mg/L). There was a significant correlation between change in CRP and change in high-density lipoprotein cholesterol (regression coefficient or slope=–2.03, 95% CI –3.20 to –0.87, p=0.001).

Fibrates can reduce CRP concentrations and change in CRP was correlated with change in high-density lipoprotein cholesterol but not with triglyceride. These findings suggest that patients with dyslipidemia could benefit from fibrates treatment by CRP lowering and this benefit is associated with lipid profile improving.

Short-term effect of fenofibrate on C-reactive protein: A meta-analysis of randomized controlled trials

BACKGROUND

C-reactive protein (CRP) is positively associated with risk for cardiovascular disease and all-cause mortality. Some but not all randomized and non-randomized clinical trials found significant associations between fenofibrate therapy and CRP but the direction and magnitude of the association varied across studies. The duration of treatment, patient populations and sample sizes varied greatly, and most short-term studies (i.e., ≤ 12 weeks) had fewer than 50 patients. In this study we meta-analyzed randomized clinical trials to determine the short-term effect of fenofibrate on CRP.

METHODS

Two reviewers independently searched PubMed and other online databases for short-term randomized clinical trials that reported CRP concentrations before and after fenofibrate treatment. Of the 81 studies examined, 14 studies with 540 patients were found eligible. Data for the change in CRP and corresponding measures of dispersion were extracted for use in the meta-analysis.

RESULTS

The weighted mean CRP concentrations before and after fenofibrate therapy were 2.15 mg/L and 1.53 mg/L (-28.8% change), respectively. Inverse-variance weighted random effects meta-analysis revealed that short-term fenofibrate treatment significantly lowers CRP by 0.58 mg/L (95% CI: 0.36-0.80). There was significant heterogeneity between studies (Q statistic = 64.5, P< 0.0001, I2 = 79.8%). There was no evidence of publication bias and sensitivity analysis revealed that omitting any of the 14 studies did not lead to a different conclusion from the overall meta-analysis result.

CONCLUSION

Short-term treatment with fenofibrate significantly lowers CRP concentration. Randomized trials that will recruit patients based with high baseline CRP concentrations and with change in CRP as a primary outcome are needed.

Non-invited review: prevention of microvascular diabetic complications by fenofibrate: lessons from FIELD and ACCORD

Microvascular complications are common in type 2 diabetes in primary care. Intensified management of glycaemia or blood pressure had little effect on microvascular complication rates in recent large trials (ADVANCE, VADT, ACCORD). In 2005, the FIELD study demonstrated a significant reduction in the need for laser treatment for retinopathy, and of progression of renal dysfunction, with fenofibrate versus placebo. The FIELD ophthalmology sub-study showed that fenofibrate reduced the risk of new retinopathy and progression of retinopathy. Also, fenofibrate versus placebo significantly reduced the risk of non-traumatic, diabetes-related amputations in a post-hoc analysis from FIELD. Recently, the results of the ACCORD Lipid study were consistent with these findings, as fenofibrate significantly reduced progression of retinopathy and albuminuria, apparently independent of effects on lipids. These findings suggest a role for fenofibrate in the prevention of major diabetic microvascular complications.

Recent development in pleiotropic effects of statins on cardiovascular disease through regulation of transforming growth factor-beta superfamily

BACKGROUND

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, also known as statins, are a drug class that reduce the level of cholesterol in the blood. As a result, statins are used to suppress the progression of cardiovascular disease. Evidence points to another component of statins involving the non-lipid effects of the drug class in preventing cardiovascular disease. One specific mediator of this action is the transforming growth factor β (TGF-β) superfamily. The TGF-β superfamily consists of proteins that include TGF-β and bone morphogenetic proteins (BMPs). These proteins regulate cellular pathways to mediate effects including immunomodulation, cell cycling, and angiogenesis. One pathway that mediates these effects is Ras. Moreover, within this pathway, different functions are possible depending on the activation of the specific receptor subtype. This review discusses the recent development of the non-lipid effects of statins in preventing cardiovascular disease progression by regulating Ras pathway of the TGF-β superfamily, especially RhoA/ROCK pathway.

METHODS

A systematic PubMed database search of all English-language articles up to 2011 was conducted using the following terms: statin, TGF-β, Ras, ROCK, GGPP, inducible nitric oxide synthase, endothelial nitric oxide synthase, actin filament formation, PPARγ, MMP-2, and human trials.

CONCLUSION

With better understanding of the pathway, various mediators were identified; some of these mediators are important biomarkers producing more specific and accurate assessment of the pleiotropic effects of statins. The review of human trials also highlights that more specific biomarkers are employed in recent studies, and the non-lipid effects on human subjects are more accurately documented. Confirmation of the accuracy of these biomarkers by further large-scale studies and further development of new biomarkers may prove an important path leading to better patient selection for treatment, and thus better cost-effectiveness may be achieved.

Functional dilator capacity is independently associated with insulin sensitivity and age in central obesity and is not improved by high dose statin treatment

OBJECTIVE

To test the hypothesis that: (i) functional microvascular dilator capacity is independently associated with insulin sensitivity and age in individuals with central adiposity at risk of cardiovascular disease (CVD); and (ii) functional microvascular dilator capacity is improved by high dose statin treatment.

METHODS

Functional dilator capacity (measured as change in laser Doppler blood flux from baseline during post occlusive reactive hyperemia [peak flux%resting flux; PF%RF] and flowmotion (power spectral density [PSD] analysis)) were assessed in 40 people with central adiposity and one or more other CVD risk factors. Measurements were made at rest and during acute hyperinsulinaemia before and six months after high dose atorvastatin (40 mg daily) or placebo.

RESULTS

Insulin-induced change in PF%RF was independently associated with insulin sensitivity (M/I) (r = 0.46 p = 0.02) and age (r = -0.46 p = 0.02), which together explained almost half of the variance in PF%RF (adjusted r² = 0.37, p = 0.008). Whilst atorvastatin decreased LDL cholesterol by 51% (p < 0.001), PF%RF and flowmotion remained unchanged.

CONCLUSIONS

Insulin sensitivity and age are independently associated with an insulin-induced change in functional microvascular dilator capacity in individuals with central adiposity at risk of CVD. Dilator capacity is not improved by six months high dose statin treatment.

Reviewing statin therapy in diabetes--towards the best practise

Statin therapy is considered critical both in primary and secondary prevention of cardiovascular disease in diabetes. Cholesterol Treatment Trialists' Collaborators meta-analysis of 14 randomised trials of statins in 18686 people with diabetes provides the latest and largest evidence showing a significant 21% reduction in major vascular events per mmol/l reduction in LDL cholesterol. Importantly, the risk reduction was similar in both types of diabetes. Growing evidence supports the view that statin therapy reduces microvascular complications as well. This review updates the current knowledge of statin therapy in preventing micro- and macrovascular complications in both type 1 and type 2 diabetes.

Current pharmacotherapeutic concepts for the treatment of cardiovascular disease in diabetics

With the growing worldwide obesity epidemic, obesity, type 2 diabetes mellitus and hypertension leading to premature cardiovascular events, are increasingly prevalent. Diabetes mellitus is a significant public health concern and more aggressive management of the condition and its complications, particularly cardiovascular disease, is warranted. Endothelial cell dysfunction is now known to be present at the earliest stages of metabolic syndrome, and insulin resistance and may precede the clinical diagnosis of type 2 diabetes mellitus by several years. The current focus on endothelial cell function as a potential target of pharmacotherapy in the management of cardiovascular disease in diabetics seems warranted, though not all drugs currently prescribed target endothelial cell function equally. In this review, we consider the six classes of drugs currently prescribed for the treatment of hypertension as they impact endothelial cell function and advocate for the development of novel drugs that can repair the endothelium and enhance nitric oxide availability thus preventing future cardiovascular events.

Lipid lowering versus pleiotropic effects of statins on skin microvascular function in patients with dysglycaemia and coronary artery disease

OBJECTIVES

To investigate the impact of lipid lowering therapy by different means on skin microvascular function in patients with dysglycaemia and coronary artery disease (CAD).

DESIGN AND SETTING

Thirty-six patients were randomized to simvastatin 80 mg daily (S80, n = 19) or ezetimibe 10 mg and simvastatin 10 mg daily (E10/S10, n = 17) for 6 weeks. Skin microvascular function was assessed by laser Doppler fluxmetry (LDF) at rest, following arterial occlusion (peak postocclusive LDF) and following local heating on the forearm (heat arm LDF) and foot (heat foot LDF). LDF parameters and serum lipids were evaluated at baseline and follow-up.

RESULTS

At follow-up, LDL cholesterol had decreased from 3.1 (2.7-3.5) to 1.6 (1.5-1.8) (mmol L(-1)) and 3.0 (2.4-3.9) to 1.3 (1.1-1.8) (mmol L(-1)) in the E10/S10 and S80 groups respectively. In the entire study group (n = 32), LDF parameters increased significantly; postocclusive LDF from 22 (17-27) to 26 (21-32) perfusion units (PU) (P < 0.001), heat foot LDF from 61 (44-82) to 66 (45-83) PU (P < 0.001) and heat arm LDF from 60 (48-121) to 75 (54-125) PU (P < 0.01). The changes in LDF parameters did not differ between the E10/S10 and S80 groups.

CONCLUSIONS

Lipid lowering improves microvascular function in patients with dysglycaemia and CAD. The data suggest that lipid lowering per se is more important than pleiotropic effects of statins for this effect.

Muscle microvascular dysfunction in central obesity is related to muscle insulin insensitivity but is not reversed by high-dose statin treatment

OBJECTIVE

To test the hypotheses that decreased insulin-mediated glucose disposal in muscle is associated with a reduced muscle microvascular exchange capacity (Kf) and that 6 months of high-dose statin therapy would improve microvascular function in people with central obesity.

RESEARCH DESIGN AND METHODS

We assessed skeletal muscle microvascular function, visceral fat mass, physical activity levels, fitness, and insulin sensitivity in skeletal muscle in 22 female and 17 male volunteers with central obesity whose age (mean +/- SD) was 51 +/- 9 years. We tested the effect of atorvastatin (40 mg daily) on muscle microvascular function in a randomized, double-blind, placebo-controlled trial lasting 6 months.

RESULTS

Kf was negatively associated with a measure of glycemia (A1C; r = -0.44, P = 0.006) and positively associated with insulin sensitivity (the ratio of insulin-stimulated glucose effectiveness, or M value, to the mean insulin concentration, or I value; r = 0.39, P = 0.02). In regression modeling, A1C, visceral fat mass, and M:I explained 38% of the variance in Kf (in a linear regression model with Kf as the outcome [R2 = 0.38, P = 0.005]). M:I was associated with Kf independently of visceral fat mass (B coefficient 3.13 [95% CI 0.22-6.02], P = 0.036). Although 6 months' treatment with atorvastatin decreased LDL cholesterol by 51% (P < 0.001) and plasma high-sensitivity C-reactive protein by 75% (P = 0.02), microvascular function was unchanged.

CONCLUSIONS

Decreased insulin-mediated glucose uptake in skeletal muscle is associated with impaired muscle microvascular exchange capacity (Kf), independently of visceral fat mass. Muscle microvascular function is not improved by 6 months of high-dose statin treatment, despite marked statin-mediated improvements in lipid metabolism and decreased inflammation.

Endothelial dysfunction in diabetes mellitus

Diabetes mellitus is associated with an increased risk of cardiovascular disease, even in the presence of intensive glycemic control. Substantial clinical and experimental evidence suggest that both diabetes and insulin resistance cause a combination of endothelial dysfunctions, which may diminish the anti-atherogenic role of the vascular endothelium. Both insulin resistance and endothelial dysfunction appear to precede the development of overt hyperglycemia in patients with type 2 diabetes. Therefore, in patients with diabetes or insulin resistance, endothelial dysfunction may be a critical early target for preventing atherosclerosis and cardiovascular disease. Microalbuminuria is now considered to be an atherosclerotic risk factor and predicts future cardiovascular disease risk in diabetic patients, in elderly patients, as well as in the general population. It has been implicated as an independent risk factor for cardiovascular disease and premature cardiovascular mortality for patients with type 1 and type 2 diabetes mellitus, as well as for patients with essential hypertension. A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. The role of chronic hyperglycemia in the development of diabetic microvascular complications and in neuropathy has been clearly established. However, the biochemical or cellular links between elevated blood glucose levels, and the vascular lesions remain incompletely understood. A number of trials have demonstrated that statins therapy as well as angiotensin converting enzyme inhibitors is associated with improvements in endothelial function in diabetes. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes. In the present review we provide the up to date details on this subject.

The effect of glibenclamide on cutaneous laser-Doppler flux

The K(ATP) channels play a crucial role in regulation of vascular tone in conditions of hypoxia. Whether they contribute to peripheral blood flow regulation in human cutaneous microcirculation during a non-hypoxic state is the matter of conflicting in vivo studies that have used plethysmographic method. Our aim was therefore to elucidate the role of K(ATP) channels in human skin microcirculation in three different conditions that evoke different interplays of vascular mechanisms; during resting conditions, during the postocclusive vasodilatation and in the vasoconstriction response to local cold exposure. The laser-Doppler (LD) skin response was monitored in 12 healthy volunteers on the skin of the fingertips of both hands at rest, after the release of an 8-min digital arteries occlusion, and during local cooling of one hand at 15 degrees C. We compared the direct (at the measuring site) and the indirect (at the contralateral non-cooled hand) LD flux response after intradermal microinjection of saline solution (1 mul) and after a microinjection of the K(ATP) channel blocker glibenclamide (8 muM saturated solution) at the measuring site after obtaining the dose-dependent effect of glibenclamide. The effect of the saline solution was used as a reference value. There was a statistically significant lower resting LD flux after the microinjection of glibenclamide 273.6+/-36 PU when compared to the values obtained after the application of the saline solution 375.8+/-31 PU (paired t-test, p=0.016). Glibenclamide also significantly reduced the relative area under the LD flux curve during the PRH response 14551+/-2508 PU*s vs. 6402+/-1476 PU*s (paired t-test, p=0.01) and increased the principal frequency of postocclusive PRH oscillations 0.0931+/-0.01 Hz vs. 0.1309+/-0.02 Hz (p=0.01). In addition, glibenclamide significantly decreased the LD flux during both the direct and indirect response to local cold exposure when compared to the application of saline solution (paired t-test, p<0.01). Our results support the conjecture that ATP sensitive K(+) channels are importantly involved in blood flow regulation of human skin microcirculation in PRH response, in resting conditions as well as in microvascular local cold response.

Therapeutic regulation of endothelial dysfunction in type 2 diabetes mellitus

Endothelial dysfunction is universal in diabetes, being intimately involved with the development of cardiovascular disease. The pathogenesis of endothelial dysfunction in diabetes is complex. It is initially related to the effects of fatty acids and insulin resistance on 'uncoupling' of both endothelial nitric oxide synthase activity and mitochondrial function. Oxidative stress activates protein kinase C (PKC), polyol, hexosamine and nuclear factor kappa B pathways, thereby aggravating endothelial dysfunction. Improvements in endothelial function in the peripheral circulation in diabetes have been demonstrated with monotherapies, including statins, fibrates, angiotensin-converting enzyme (ACE) inhibitors, metformin and fish oils. These observations are supported by large clinical end point trials. Other studies show benefits with certain antioxidants, L-arginine, folate, PKC-inhibitors, peroxisome proliferator activated receptor (PPAR)-alpha and -gamma agonists and phosphodiesterase (PDE-5) inhibitors. However, the benefits of these agents remain to be shown in clinical end point trials. Combination treatments, for example, statins plus ACE inhibitors and statins plus fibrates, have also been demonstrated to have additive benefits on endothelial function in diabetes, but there are no clinical outcome data to date. Measurement of endothelial dysfunction in cardiovascular research can provide fresh opportunities for exploring the mechanism of benefit of new therapeutic regimens and for planning and designing large clinical trials.

Hyperglycemia and hyperlipidemia are associated with endothelial dysfunction during the development of type 2 diabetes

Diabetes mellitus impairs endothelial function, which can be considered as the hallmark in the development of cardiovascular diseases. Hyperglycemia, hyperinsulinemia, and hyperlipidemia are believed to contribute to endothelial dysfunction. In the present study, we investigated the possible links among these plasma metabolic markers and endothelial function in a mouse model during the development of type 2 diabetes. C57BL/6J-Lepob/ob mice at 8, 12, and 16 weeks were used to study endothelial function during the establishment of type 2 diabetes. Endothelial function was accessed in vitro in the thoracic aorta by measuring acetylcholine (ACh)-stimulated vasodilatation. Blood plasma was obtained for the measurements of glucose, insulin, triglycerides, and cholesterol levels. Correlation and multiple regression analysis revealed strong negative associations between the ACh responsiveness and the plasma levels of glucose, insulin, and lipid profiles at the age of 8 weeks. Associations were observed at neither older age nor in C57BL/6J mice. In conclusion, the increase in plasma levels of glucose, insulin, and lipids is associated with the impairment of the endothelial function during the early stage of the development of type 2 diabetes. The loss of correlation at an older age suggests multifactorial regulation of endothelial function and cardiovascular complications at later stages of the disease.