Abstract
Patients with type 2 diabetes mellitus (T2DM) are at high risk for macrovascular complications, which represent the major cause of mortality. Despite effective treatment of established ...cardiovascular (CV) risk factors (dyslipidemia, hypertension, procoagulant state), there remains a significant amount of unexplained CV risk. Insulin resistance is associated with a cluster of cardiometabolic risk factors known collectively as the insulin resistance (metabolic) syndrome (IRS). Considerable evidence, reviewed herein, suggests that insulin resistance and the IRS contribute to this unexplained CV risk in patients with T2DM. Accordingly, CV outcome trials with pioglitazone have demonstrated that this insulin-sensitizing thiazolidinedione reduces CV events in high-risk patients with T2DM. In this review the roles of insulin resistance and the IRS in the development of atherosclerotic CV disease and the impact of the insulin-sensitizing agents and of other antihyperglycemic medications on CV outcomes are discussed.
Type 2 diabetes mellitus (T2DM) is characterized by multiple pathophysiologic abnormalities. With time, multiple glucose-lowering medications are commonly required to reduce and maintain plasma ...glucose concentrations within the normal range. Type 2 diabetes mellitus individuals also are at a very high risk for microvascular complications and the incidence of heart attack and stroke is increased two- to three-fold compared with non-diabetic individuals. Therefore, when selecting medications to normalize glucose levels in T2DM patients, it is important that the agent not aggravate, and ideally even improve, cardiovascular risk factors (CVRFs) and reduce cardiovascular morbidity and mortality. In this review, we examine the effect of oral (metformin, sulfonylureas, meglitinides, thiazolidinediones, DPP4 inhibitors, SGLT2 inhibitors, and α-glucosidase inhibitors) and injectable (glucagon-like peptide-1 receptor agonists and insulin) glucose-lowering drugs on established CVRFs and long-term studies of cardiovascular outcomes. Firm evidence that in T2DM cardiovascular disease can be reversed or prevented by improving glycaemic control is still incomplete and must await large, long-term clinical trials in patients at low risk using modern treatment strategies, i.e., drug combinations designed to maximize HbA1c reduction while minimizing hypoglycaemia and excessive weight gain.
The SGLT2 inhibitors (SGLTi) and glucagon‐like‐1 receptor agonists (GLP‐1 RAs) effectively reduce HbA1c, but via very different mechanisms, making them an effective duet for combination therapy. ...Recently, drugs in both of these antidiabetic classes have been shown to reduce cardiovascular events, most probably by different mechanisms. SGLT2i appear to exert their CV protective actions by haemodynamic effects, while GLP‐1 RAs work via anti‐atherogenic/anti‐inflammatory mechanisms, raising the possibility that combined therapy with these 2 classes may produce additive CV benefits. The SGLT2i and GLP‐1 RAs also reduced macroalbuminuria, decreased the time for doubling of serum creatinine, and slowed the time to end‐stage renal disease. In this perspective, we review the potential benefit of combination SGLT2i/GLP‐1 RA therapy on metabolic‐cardiovascular‐renal disease in patients with type 2 diabetes mellitus.
In the transition from normal glucose tolerance (NGT) to type 2 diabetes mellitus (T2DM), the role of β-cell dysfunction and peripheral insulin resistance (IR) is well established. However, the ...impact of dysfunctional adipose tissue has not been fully elucidated. The aim of this study was to evaluate the role of resistance to the antilipolytic effect of insulin (adipose tissue IR Adipo-IR) in a large group of subjects with NGT, impaired glucose tolerance (IGT), and T2DM. Three hundred two subjects with varying glucose tolerance received an oral glucose tolerance test (OGTT) and euglycemic insulin clamp. We evaluated Adipo-IR (fasting and mean OGTT plasma free fatty acid FFA × insulin concentrations), peripheral IR (1/Matsuda index and (M/I)
value), and β-cell function (calculated as the ratio of the increment in plasma insulin to glucose OGTT/IR (ΔI/ΔG ÷ IR)). Fasting Adipo-IR was increased twofold in obese subjects with NGT and IGT versus lean subjects with NGT (8.0 ± 1.1 and 9.2 ± 0.7 vs. 4.1 ± 0.3, respectively) and threefold in subjects with T2DM (11.9 ± 0.6;
< 0.001). Progressive decline in ΔI/ΔG ÷ IR was associated with a progressive impairment in FFA suppression during OGTT, whereas the rise in mean plasma glucose concentration only became manifest when subjects became overtly diabetic. The progressive decline in β-cell function that begins in individuals with NGT is associated with a progressive increase in FFA and fasting Adipo-IR.
The kidney has a pivotal role in maintaining glucose homeostasis by using glucose as a metabolic fuel, by producing glucose through gluconeogenesis, and by reabsorbing all filtered glucose through ...the sodium-glucose cotransporters SGLT1 and SGLT2 located in the proximal tubule. In patients with diabetes, the maximum glucose reabsorptive capacity (Tm
) of the kidney, as well as the threshold for glucose spillage into the urine, are elevated, contributing to the pathogenesis of hyperglycaemia. By reducing the Tm
and, more importantly, the threshold of glucosuria, SGLT2 inhibitors enhance glucose excretion, leading to a reduction in fasting and postprandial plasma glucose levels and improvements in both insulin secretion and insulin sensitivity. The beneficial effects of SGLT2 inhibition extend beyond glycaemic control, however, with new studies demonstrating that inhibition of renal glucose reabsorption reduces blood pressure, ameliorates glucotoxicity and induces haemodynamic effects that lead to improved cardiovascular and renal outcomes in patients with type 2 diabetes mellitus. In this Review we examine the role of SGLT2 and SGLT1 in the regulation of renal glucose reabsorption in health and disease and the effect of SGLT2 inhibition on renal function, glucose homeostasis, and cardiovascular disease.
Individuals with impaired glucose tolerance (IGT) and/or impaired fasting glucose (IFG) are at high risk, not only to develop diabetes mellitus, but also to experience an adverse cardiovascular (CV) ...event (myocardial infarction, stroke, CV death) later in life. The underlying pathophysiologic disturbances (insulin resistance and impaired β-cell function) responsible for the development of type 2 diabetes are maximally/near maximally expressed in subjects with IGT/IFG. These individuals with so-called prediabetes manifest all of the same CV risk factors (dysglycemia, dyslipidemia, hypertension, obesity, physical inactivity, insulin resistance, procoagulant state, endothelial dysfunction, inflammation) that place patients with type 2 diabetes at high risk for macrovascular complications. The treatment of these CV risk factors should follow the same guidelines established for patients with type 2 diabetes, and should be aggressively followed to reduce future CV events.
Although cardiovascular (CV) mortality is the principal cause of death in individuals with type 2 diabetes (T2DM), reduction of plasma glucose concentration has little effect on CV disease (CVD) ...risk. Thus, novel strategies to reduce CVD risk in T2DM patients are needed. The recently published BI 10773 (Empagliflozin) Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients (EMPA-REG OUTCOME) study demonstrated that in T2DM patients with high CVD risk empagliflozin reduced the primary major adverse cardiac event end point (CV death, nonfatal myocardial infarction, nonfatal stroke) by 14%. This beneficial effect was driven by a 38% reduction in CV mortality with no significant decrease in nonfatal myocardial infarction or stroke. Empagliflozin also caused a 35% reduction in hospitalization for heart failure without affecting hospitalization for unstable angina. Although sodium-glucose cotransporter 2 inhibitors exert multiple metabolic benefits (decreases in HbA1c, body weight, and blood pressure and an increase in HDL cholesterol), all of which could reduce CVD risk, it is unlikely that the reduction in CV mortality can be explained by empagliflozin's metabolic effects. More likely, hemodynamic effects, specifically reduced blood pressure and decreased extracellular volume, are responsible for the reduction in CV mortality and heart failure hospitalization. In this Perspective, we will discuss possible mechanisms for these beneficial effects of empagliflozin and their implications for the care of T2DM patients.
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