Evolution of insulin resistance in coronary artery disease patients on four different pharmacological therapies

THE IMPACT OF CARDIOVASCULAR DRUGS ON GLYCEMIC CONTROL: A REVIEW

OBJECTIVE

The prevalence of diabetes mellitus (DM) is steadily rising in the U.S., both in the general population and among those with cardiovascular disease (CVD). Understanding how to treat a patient with both conditions is becoming increasingly important. With multiple therapeutic options for CVD management, some medications will invariably impact glycemia in this group of patients. The concept of "DM-friendly" management of CVD is based on a treatment approach of selecting medications that do not impair glycemic control and provide equivalent cardioprotective effects. This article reviews the glycemic effects of various classes of medications commonly used to treat CVD.

METHODS

Data sources were all PubMed- and Google Scholar-referenced articles in English-language peer-reviewed journals from 1980 through April 2016. Studies selected could include observational studies or prospective clinical trials. Prospective clinical trials included in this review focused on investigating the association of the medication of interest with glycemic outcomes. Meta-analyses and systematic reviews were also included.

RESULTS

The data on glycemic effects were lacking for many of the medication classes and individual medications examined. However, in our review, certain beta-blockers and renin angiotensin aldosterone system inhibitors, and select calcium channel blockers were consistently shown to have favorable glycometabolic profiles when compared with other commonly used cardiovascular therapies.

CONCLUSION

Several commonly prescribed medications for the treatment of CVD, such as certain beta-blockers and renin angiotensin aldosterone system inhibiting agents, are associated with favorable glycometabolic effects. As clinicians are more often faced with the challenge of treating patients with DM and concomitant CVD, consideration of how common cardiovascular medications may affect glycemia should be incorporated into the clinical decision making process.

ABBREVIATIONS

A1C = hemoglobin A1C ACE = angiotensin-converting enzyme ARB = angiotensin II receptor blocker CCB = calcium channel blocker CI = confidence interval CVD = cardiovascular disease DM = diabetes mellitus MI = myocardial infarction RR = relative risk.

The role of the renin-angiotensin system in the development of insulin resistance in skeletal muscle

The canonical renin-angiotensin system (RAS) involves the initial action of renin to cleave angiotensinogen to angiotensin I (ANG I), which is then converted to ANG II by the angiotensin converting enzyme (ACE). ANG II plays a critical role in numerous physiological functions, and RAS overactivity underlies many conditions of cardiovascular dysregulation. In addition, ANG II, by acting on both endothelial and myocellular AT1 receptors, can induce insulin resistance by increasing cellular oxidative stress, leading to impaired insulin signaling and insulin-stimulated glucose transport activity. This insulin resistance associated with RAS overactivity, when coupled with progressive ß-cell dysfunction, eventually leads to the development of type 2 diabetes. Interventions that target RAS overactivity, including ACE inhibitors, ANG II receptor blockers, and, most recently, renin inhibitors, are effective both in reducing hypertension and in improving whole-body and skeletal muscle insulin action, due at least in part to enhanced Akt-dependent insulin signaling and insulin-dependent glucose transport activity. ANG-(1-7), which is produced from ANG II by the action of ACE2 and acts via Mas receptors, can counterbalance the deleterious actions of the ACE/ANG II/AT1 receptor axis on the insulin-dependent glucose transport system in skeletal muscle. This beneficial effect of the ACE2/ANG-(1-7)/Mas receptor axis appears to depend on the activation of Akt. Collectively, these findings underscore the importance of RAS overactivity in the multifactorial etiology of insulin resistance in skeletal muscle, and provide support for interventions that target the RAS to ameliorate both cardiovascular dysfunctions and insulin resistance in skeletal muscle tissue.

Blocking the renin-angiotensin-aldosterone system to prevent diabetes mellitus

Type 2 diabetes mellitus (DM) is increasing around the world, and the public health impact of DM, driven largely by cardiovascular disease complications, underpins the importance of continued efforts toward primary prevention of DM. Only a few interventions have been shown to prevent DM, with none of them yet proven to improve cardiovascular risk commensurately. Accumulating evidence suggest that drugs that block the renin-angiotensin-aldosterone system (RAAS), many of which have proven cardiovascular disease (CVD) benefit, also have favourable effects on parameters of glucose metabolism and incident diabetes. Here we review the evidence accumulated to date from animal studies, clinical mechanistic studies and clinical trials regarding the effect of RAAS inhibition and incident DM.

Modulation of metabolic control by angiotensin converting enzyme (ACE) inhibition

Angiotensin converting enzyme (ACE) inhibitors are a widely used intervention for blood pressure control, and are particularly beneficial in hypertensive type 2 diabetic subjects with insulin resistance. The hemodynamic effects of ACE inhibitors are associated with enhanced levels of the vasodilator bradykinin and decreased production of the vasoconstrictor and growth factor angiotensin II (ATII). In insulin-resistant conditions, ACE inhibitors can also enhance whole-body glucose disposal and glucose transport activity in skeletal muscle. This review will focus on the metabolic consequences of ACE inhibition in insulin resistance. At the cellular level, ACE inhibitors acutely enhance glucose uptake in insulin-resistant skeletal muscle via two mechanisms. One mechanism involves the action of bradykinin, acting through bradykinin B(2) receptors, to increase nitric oxide (NO) production and ultimately enhance glucose transport. A second mechanism involves diminution of the inhibitory effects of ATII, acting through AT(1) receptors, on the skeletal muscle glucose transport system. The acute actions of ACE inhibitors on skeletal muscle glucose transport are associated with upregulation of insulin signaling, including enhanced IRS-1 tyrosine phosphorylation and phosphatidylinositol-3-kinase activity, and ultimately with increased cell-surface GLUT-4 glucose transporter protein. Chronic administration of ACE inhibitors or AT(1) antagonists to insulin-resistant rodents can increase protein expression of GLUT-4 in skeletal muscle and myocardium. These data support the concept that ACE inhibitors can beneficially modulate glucose control in insulin-resistant states, possibly through a NO-dependent effect of bradykinin and/or antagonism of ATII action on skeletal muscle.