Insulin and Its Cardiovascular Effects: What Is the Current Evidence?

PURPOSE OF REVIEW: In this article, we examine the nature of the complex relationship between insulin and cardiovascular disease. With metabolic abnormalities comes increased risk for cardiovascular complications. We discuss the key factors implicated in development and progression of cardiovascular disease, its relationship to insulin therapy, and what can be learned from large, recent cardiovascular outcome studies. RECENT FINDINGS: Preclinical studies suggest that insulin has positive effects of facilitating glucose entry into cells and maintaining euglycemia and negative effects of favoring obesity and atherogenesis under certain conditions. Confounding this relationship is that cardiovascular morbidity is linked closely to duration and control of diabetes, and insulin is often used in patients with diabetes of longer duration. However, more recent clinical studies examining the cardiovascular safety of insulin therapy have been reassuring. Diabetes and cardiovascular outcomes are closely linked. Many studies have implicated insulin resistance and hyperinsulinemia as a major factor for poor cardiovascular outcomes. Additional studies link the anabolic effects of therapeutic insulin to weight gain, along with hypoglycemia, which may further aggravate cardiovascular risk in this population. Though good glycemic control has been shown to improve microvascular risks in type 1 and type 2 diabetes, what are the known cardiovascular effects of insulin therapy? The ORIGIN trial suggests at least a neutral effect of the basal insulin glargine on cardiovascular outcomes. Recent studies have demonstrated that ultra-long-acting insulin analogs like insulin degludec are non-inferior to insulin glargine with regard to cardiovascular outcomes.

Conversion from intravenous insulin to subcutaneous insulin after cardiovascular surgery: transition to target study.

BACKGROUND: No study of transition from intravenous to subcutaneous insulin after cardiac surgery with dose based on percentage of intravenous total daily insulin (TDI) has reported a clearly superior regimen for achieving target blood glucose. We compared three first-dose transition strategies for insulin glargine: two based on TDI alone and one that also took body weight into account. METHODS: Mostly obese, type 1 and type 2 diabetes patients (n = 223) undergoing cardiac surgery were randomized to receive insulin glargine subcutaneously at 60% or 80% of TDI or in a dose based on TDI and body weight. RESULTS: Transition to subcutaneous insulin occurred 27.4 ± 6.6 h after surgery. Over the study period, mean proportion of blood glucose values within target range (80-140 mg/dL) were 0.34 ± 0.24, 0.35 ± 0.24, and 0.36 ± 0.22 in the 60% TDI, 80% TDI, and weight-based groups, respectively. This difference was not significant. Significantly more insulin corrections were needed in the 60% TDI group than in the weight-based group. There was only one incidence of hypoglycemia (blood glucose < 40 mg/dL). CONCLUSIONS: No subcutaneous insulin regimen implemented approximately 1 day after cardiac surgery showed significantly better control of blood glucose over the 3-day study period. Further studies are needed to determine optimal formulae for effecting an early transition to subcutaneous insulin after cardiac surgery or whether it is preferable and/or necessary to continue intravenous insulin therapy for an additional period of time.

Distinguishing among incretin-based therapies. Glucose-lowering effects of incretin-based therapies.

Extensive experience from randomized clinical trials demonstrates the efficacy of GLP-1 agonists and DPP-4 inhibitors as monotherapy and in combination with metformin and other agents, although reductions in FPG and PPG, and consequently A1C, are greater with GLP-1 agonists than with DPP-4 inhibitors. This difference may result from the pharmacologic levels of GLP-1 activity that are achieved with the GLP-1 agonists and their direct action on the GLP-1 receptor. The GLP-1 agonists have attributes that would make either of them an appropriate choice in the management of all 3 patients in our case studies, while either DPP-4 inhibitor would be an appropriate choice for Case 1. Differences in dosing, administration, safety, and tolerability should be considered.

Distinguishing among incretin-based therapies. Patient education and self-management.

Working closely with patients and providing ongoing education, ideally in conjunction with a diabetes care team, can help ensure that the best treatment options are selected for an individual patient and that the patient is capable of effective self-management.

Distinguishing among incretin-based therapies. Safety, tolerability, and nonglycemic effects of incretin-based therapies.

The overall safety profiles of GLP-1 agonists and DPP-4 inhibitors are favorable, with a low incidence of hypoglycemia. This attribute, along with their weight and cardiovascular benefits, particularly with the GLP-1 agonists, make them appropriate choices in our 3 patient cases. Ongoing safety investigations with GLP-1 agonists and DPP-4 inhibitors will provide further clarity to the complete safety profiles of these agents.

Distinguishing among incretin-based therapies. Pathophysiology of type 2 diabetes mellitus: potential role of incretin-based therapies.

The multifactorial nature of the pathogenesis of T2DM provides an opportunity to combine treatments that act upon different mechanisms. In addition to improving insulin resistance and pancreatic ß-cell dysfunction, the GLP-1 agonists and DPP-4 inhibitors improve the impaired incretin response, as well as increase insulin secretion and reduce glucagon secretion, both in a glucose-dependent manner. As a result of these multiple actions, the GLP-1 agonists and DPP-4 inhibitors lower both fasting and postprandial glucose levels. The effects of GLP-1 agonists tend to be greater, probably because they produce pharmacologic levels of GLP-1 compared to physiologic levels with the DPP-4 inhibitors. Another difference is that unlike the DPP-4 inhibitors, the GLP-1 agonists also slow gastric emptying and promote satiety.

Distinguishing among incretin-based therapies. Introduction.

The "treat to target" approach is to quickly achieve the target glycosylated hemoglobin (AIC) goal of <7% in most people, and then intensify or change therapy as needed to maintain glycemic control. Results of an online survey demonstrate uncertainty regarding the clinical differences between glucagon-like peptide (GLP-1) agonists and dipeptidyl peptidase (DPP)-4 inhibitors. The increasingly important roles of the GLP-1 agonists and DPP-4 inhibitors stem from their overall good efficacy and safety profiles compared with other treatment options.

Practical applications of therapy with a glucagon-like peptide-1 receptor agonist.

Patients such as ML represent a common challenge in the primary care management of patients with T2DM. After some response to initial therapy with lifestyle management and metformin, the A1C goal of <7.0% after 2 to 3 months was not achieved, necessitating the initiation of combination therapy. The 4 groups of medications recommended by the ADA/EASD panel as the preferred therapies are basal insulin, the sulfonylureas, the TZD pioglitazone, and GLP-1 receptor agonists. In addition to considering efficacy, safety, cost, and other medication-related factors, the treatment plan must take into account the patient's individual needs, concerns, and capabilities. These additional considerations help to foster increased patient self-management and greater treatment adherence. To achieve these objectives, comprehensive patient education is essential. The unique mechanism of action of the GLP-1 receptor agonist class of medications makes these agents a desirable choice as add-on therapy to metformin.

Effectiveness of the novel anti-diabetes medication exenatide in everyday practice: Comparison with clinical trials.

We evaluated effectiveness of exenatide in 81 unselected patients and compared the results with clinical trials. Patients achieved a similar reduction in A1C and lost more weight than patients in the clinical trials. Thirty-seven (46%) were treated off-label. Exenatide was effective on and off-label in this unselected patient group.

Medical therapy of gonadotropin-producing and nonfunctioning pituitary adenomas.

Clinically nonfunctioning pituitary adenomas are one of the most common types of pituitary tumors. Unless they present with symptoms related to local mass effect, most tumors are detected incidentally when imaging studies are performed for other reasons. Although clinically nonfunctioning, most of these tumors have evidence, in vitro, of gonadotropin hormone or glycoprotein subunit production. The gonadotropins or their monomer submits rarely cause clinically identifiable effects. When these tumors present as macroadenomas, often with associated mass effect and hypopituitarism, primary therapy is neurosurgery. The role for medical therapy will be reviewed here.