Molecular Mechanisms of Insulin Resistance That Impact Cardiovascular Biology
TL;DR: Some of the effects of insulin resistance and mechanisms of potentially detrimental influence of hyperinsulinemia in the presence of metabolic insulin resistance are discussed.
Abstract: Insulin resistance is concomitant with type 2 diabetes, obesity, hypertension, and other features of the metabolic syndrome. Because insulin resistance is associated with cardiovascular disease, both scientists and physicians have taken great interest in this disorder. Insulin resistance is associated with compensatory hyperinsulinemia, but individual contributions of either of these two conditions remain incompletely understood and a subject of intense investigation. One possibility is that in an attempt to overcome the inhibition within the metabolic insulin-signaling pathway, hyperinsulinemia may continue to stimulate the mitogenic insulin-signaling pathway, thus exerting its detrimental influence. Here we discuss some of the effects of insulin resistance and mechanisms of potentially detrimental influence of hyperinsulinemia in the presence of metabolic insulin resistance.
Citations
More filters
TL;DR: White adipose tissue is no longer considered an inert tissue mainly devoted to energy storage but is emerging as an active participant in regulating physiologic and pathologic processes, including immunity and inflammation.
Abstract: White adipose tissue is no longer considered an inert tissue mainly devoted to energy storage but is emerging as an active participant in regulating physiologic and pathologic processes, including immunity and inflammation. Macrophages are components of adipose tissue and actively participate in its activities. Furthermore, cross-talk between lymphocytes and adipocytes can lead to immune regulation. Adipose tissue produces and releases a variety of proinflammatory and anti-inflammatory factors, including the adipokines leptin, adiponectin, resistin, and visfatin, as well as cytokines and chemokines, such as TNF-α, IL-6, monocyte chemoattractant protein 1, and others. Proinflammatory molecules produced by adipose tissue have been implicated as active participants in the development of insulin resistance and the increased risk of cardiovascular disease associated with obesity. In contrast, reduced leptin levels might predispose to increased susceptibility to infection caused by reduced T-cell responses in malnourished individuals. Altered adipokine levels have been observed in a variety of inflammatory conditions, although their pathogenic role has not been completely clarified.
2,482 citations
TL;DR: Eight players comprise the ominous octet and dictate that treatment should be based upon reversal of known pathogenic abnormalities and not simply on reducing the A1C, and therapy must be started early to prevent/slow the progressive β-cell failure that already is well established in IGT subjects.
Abstract: Insulin resistance in muscle and liver and β-cell failure represent the core pathophysiologic defects in type 2 diabetes. It now is recognized that the β-cell failure occurs much earlier and is more severe than previously thought. Subjects in the upper tertile of impaired glucose tolerance (IGT) are maximally/near-maximally insulin resistant and have lost over 80% of their β-cell function. In addition to the muscle, liver, and β-cell (triumvirate), the fat cell (accelerated lipolysis), gastrointestinal tract (incretin deficiency/resistance), α-cell (hyperglucagonemia), kidney (increased glucose reabsorption), and brain (insulin resistance) all play important roles in the development of glucose intolerance in type 2 diabetic individuals. Collectively, these eight players comprise the ominous octet and dictate that: 1 ) multiple drugs used in combination will be required to correct the multiple pathophysiological defects, 2 ) treatment should be based upon reversal of known pathogenic abnormalities and not simply on reducing the A1C, and 3 ) therapy must be started early to prevent/slow the progressive β-cell failure that already is well established in IGT subjects. A treatment paradigm shift is recommended in which combination therapy is initiated with diet/exercise, metformin (which improves insulin sensitivity and has antiatherogenic effects), a thiazolidinedione (TZD) (which improves insulin sensitivity, preserves β-cell function, and exerts antiatherogenic effects), and exenatide (which preserves β-cell function and promotes weight loss). Sulfonylureas are not recommended because, after an initial improvement in glycemic control, they are associated with a progressive rise in A1C and progressive loss of β-cell function.
The natural history of type 2 diabetes has been well described in multiple populations (1–16) (rev. in (17,18). Individuals destined to develop type 2 diabetes inherit a set of genes from their parents that make their tissues resistant to insulin (1,16,19–24). In liver, the insulin resistance is manifested by …
2,184 citations
01 May 2005
TL;DR: Despite the incomplete understanding of the complex biological mechanisms of insulin action and insulin resistance, the dramatic social changes of the past century with respect to physical activity, diet, work, socialisation and sleep patterns must be considered.
Abstract: As obesity and diabetes reach epidemic proportions in the developed world, the role of insulin resistance and its consequences are gaining prominence. Understanding the role of insulin in wide-ranging physiological processes and the influences on its synthesis and secretion, alongside its actions from the molecular to the whole body level, has significant implications for much chronic disease seen in Westernised populations today. This review provides an overview of insulin, its history, structure, synthesis, secretion, actions and interactions followed by a discussion of insulin resistance and its associated clinical manifestations. Specific areas of focus include the actions of insulin and manifestations of insulin resistance in specific organs and tissues, physiological, environmental and pharmacological influences on insulin action and insulin resistance as well as clinical syndromes associated with insulin resistance. Clinical and functional measures of insulin resistance are also covered. Despite our incomplete understanding of the complex biological mechanisms of insulin action and insulin resistance, we need to consider the dramatic social changes of the past century with respect to physical activity, diet, work, socialisation and sleep patterns. Rapid globalization, urbanisation and industrialization have spawned epidemics of obesity, diabetes and their attendant co-morbidities, as physical inactivity and dietary imbalance unmask latent predisposing genetic traits.
1,360 citations
TL;DR: A review of the mechanisms involved in the maintenance of normal glucose homeostasis in the basal or postabsorptive state (10−12 h overnight fast) and following ingestion of a typical mixed meal can be found in this article.
1,276 citations
TL;DR: It can be concluded that insulin resistance in the myocardium generates damage by at least three different mechanisms: (1) signal transduction alteration, (2) impaired regulation of substrate metabolism, and (3) altered delivery of substrates to theMyocardium.
Abstract: For many years, cardiovascular disease (CVD) has been the leading cause of death around the world. Often associated with CVD are comorbidities such as obesity, abnormal lipid profiles and insulin resistance. Insulin is a key hormone that functions as a regulator of cellular metabolism in many tissues in the human body. Insulin resistance is defined as a decrease in tissue response to insulin stimulation thus insulin resistance is characterized by defects in uptake and oxidation of glucose, a decrease in glycogen synthesis, and, to a lesser extent, the ability to suppress lipid oxidation. Literature widely suggests that free fatty acids are the predominant substrate used in the adult myocardium for ATP production, however, the cardiac metabolic network is highly flexible and can use other substrates, such as glucose, lactate or amino acids. During insulin resistance, several metabolic alterations induce the development of cardiovascular disease. For instance, insulin resistance can induce an imbalance in glucose metabolism that generates chronic hyperglycemia, which in turn triggers oxidative stress and causes an inflammatory response that leads to cell damage. Insulin resistance can also alter systemic lipid metabolism which then leads to the development of dyslipidemia and the well-known lipid triad: (1) high levels of plasma triglycerides, (2) low levels of high-density lipoprotein, and (3) the appearance of small dense low-density lipoproteins. This triad, along with endothelial dysfunction, which can also be induced by aberrant insulin signaling, contribute to atherosclerotic plaque formation. Regarding the systemic consequences associated with insulin resistance and the metabolic cardiac alterations, it can be concluded that insulin resistance in the myocardium generates damage by at least three different mechanisms: (1) signal transduction alteration, (2) impaired regulation of substrate metabolism, and (3) altered delivery of substrates to the myocardium. The aim of this review is to discuss the mechanisms associated with insulin resistance and the development of CVD. New therapies focused on decreasing insulin resistance may contribute to a decrease in both CVD and atherosclerotic plaque generation.
867 citations
Cites background from "Molecular Mechanisms of Insulin Res..."
...In insulin resistance, the target cells fail to respond to ordinary levels of circulating insulin thus higher concentrations of insulin are required for a normal response [34]....
[...]
References
More filters
Journal Article•
TL;DR: In this article, the effects of intensive blood-glucose control with either sulphonylurea or insulin and conventional treatment on the risk of microvascular and macrovascular complications in patients with type 2 diabetes in a randomised controlled trial were compared.
17,108 citations
TL;DR: The possibility is raised that resistance to insulin-stimulated glucose uptake and hyperinsulinemia are involved in the etiology and clinical course of three major related diseases— NIDDM, hypertension, and CAD.
Abstract: Resistance to insulin-stimulated glucose uptake is present in the majority of patients with impaired glucose tolerance (IGT) or non-insulin-dependent diabetes mellitus (NIDDM) and in ∼25% of nonobese individuals with normal oral glucose tolerance. In these conditions, deterioration of glucose tolerance can only be prevented if the β-cell is able to increase its insulin secretory response and maintain a state of chronic hyperinsulinemia. When this goal cannot be achieved, gross decompensation of glucose homeostasis occurs. The relationship between insulin resistance, plasma insulin level, and glucose intolerance is mediated to a significant degree by changes in ambient plasma free-fatty acid (FFA) concentration. Patients with NIDDM are also resistant to insulin suppression of plasma FFA concentration, but plasma FFA concentrations can be reduced by relatively small increments in insulin concentration.Consequently, elevations of circulating plasma FFA concentration can be prevented if large amounts of insulin can be secreted. If hyperinsulinemia cannot be maintained, plasma FFA concentration will not be suppressed normally, and the resulting increase in plasma FFA concentration will lead to increased hepatic glucose production. Because these events take place in individuals who are quite resistant to insulinstimulated glucose uptake, it is apparent that even small increases in hepatic glucose production are likely to lead to significant fasting hyperglycemia under these conditions. Although hyperinsulinemia may prevent frank decompensation of glucose homeostasis in insulin-resistant individuals, this compensatory response of the endocrine pancreas is not without its price. Patients with hypertension, treated or untreated, are insulin resistant, hyperglycemic, and hyperinsulinemic. In addition, a direct relationship between plasma insulin concentration and blood pressure has been noted. Hypertension can also be produced in normal rats when they are fed a fructose-enriched diet, an intervention that also leads to the development of insulin resistance and hyperinsulinemia. The development of hypertension in normal rats by an experimental manipulation known to induce insulin resistance and hyperinsulinemia provides further support for the view that the relationship between the three variables may be a causal one. However, even if insulin resistance and hyperinsulinemia are not involved in the etiology of hypertension, it is likely that the increased risk of coronary artery disease (CAD) in patients with hypertension and the fact that this risk if not reduced with antihypertensive treatment are due to the clustering of risk factors for CAD, in addition to high blood pressure, associated with insulin resistance. These include hyperinsulinemia, IGT, increased plasma triglyceride concentration, and decreased high-density lipoprotein cholesterol concentration, all of which are associated with increased risk for CAD. It is likely that the same risk factors play a significant role in the genesis of CAD in the population as a whole. Based on these considerations the possibility is raised that resistance to insulin-stimulated glucose uptake and hyperinsulinemia are involved in the etiology and clinical course of three major related diseases— NIDDM, hypertension, and CAD.
12,460 citations
"Molecular Mechanisms of Insulin Res..." refers background in this paper
...Insulin resistance has elicited great interest in medical and scientific communities because of its association with cardiovascular disease (3,4)....
[...]
TL;DR: Ramipril significantly reduces the rates of death, myocardial infarction, and stroke in a broad range of high-risk patients who are not known to have a low ejection fraction or heart failure.
Abstract: Angiotensin-converting-enzyme inhibitors improve the outcome among patients with left ventricular dysfunction, whether or not they have heart failure. We assessed the role of an angiotensin-converting-enzyme inhibitor, ramipril, in patients who were at high risk for cardiovascular events but who did not have left ventricular dysfunction or heart failure.A total of 9297 high-risk patients (55 years of age or older) who had evidence of vascular disease or diabetes plus one other cardiovascular risk factor and who were not known to have a low ejection fraction or heart failure were randomly assigned to receive ramipril (10 mg once per day orally) or matching placebo for a mean of five years. The primary outcome was a composite of myocardial infarction, stroke, or death from cardiovascular causes. The trial was a two-by-two factorial study evaluating both ramipril and vitamin E. The effects of vitamin E are reported in a companion paper.A total of 651 patients who were assigned to receive ramipril (14.0 percent) reached the primary end point, as compared with 826 patients who were assigned to receive placebo (17.8 percent) (relative risk, 0.78; 95 percent confidence interval, 0.70 to 0.86; P<0.001). Treatment with ramipril reduced the rates of death from cardiovascular causes (6.1 percent, as compared with 8.1 percent in the placebo group; relative risk, 0.74; P<0.001), myocardial infarction (9.9 percent vs. 12.3 percent; relative risk, 0.80; P<0.001), stroke (3.4 percent vs. 4.9 percent; relative risk, 0.68; P<0.001), death from any cause (10.4 percent vs. 12.2 percent; relative risk, 0.84; P=0.005), revascularization procedures (16.3 percent vs. 18.8 percent; relative risk, 0.85; P<0.001), cardiac arrest (0.8 percent vs. 1.3 percent; relative risk, 0.62; P=0.02), [corrected] heart failure (9.1 percent vs. 11.6 percent; relative risk, 0.77; P<0.001), and complications related to diabetes (6.4 percent vs. 7.6 percent; relative risk, 0.84; P=0.03).Ramipril significantly reduces the rates of death, myocardial infarction, and stroke in a broad range of high-risk patients who are not known to have a low ejection fraction or heart failure.
7,828 citations
"Molecular Mechanisms of Insulin Res..." refers background in this paper
...Finally, the role of RAAS in the development of insulin resistance is suggested by a reduced incidence of type 2 diabetes in animal models and in individuals in clinical trials of ACE inhibitors and ARBs (48,55)....
[...]
...It is important to note that the HOPE trial demonstrated that despite almost identical levels of blood pressure, patients with diabetes treated with an ACE inhibitor (ramipril) displayed a significant reduction in cardiovascular events (48)....
[...]
...Two additional trials (the Reduction of End Points in Noninsulin Dependent Diabetes Mellitus with the Angiotensin II Antagonist Losartan [RENAAL] trial and the Irbesartan Diabetic Nephropathy Trial [IDNT]) have provided convincing evidence that angiotensin receptor blockers (ARBs) significantly reduce the rate of death and development of end-stage renal disease (53,54)....
[...]
...4) RAAS The pathophysiological link between angiotensin II and atherosclerosis has been firmly established (48)....
[...]
Journal Article•
TL;DR: Since intensive glucose control with metformin appears to decrease the risk of diabetes-related endpoints in overweight diabetic patients, and is associated with less weight gain and fewer hypoglycaemic attacks than are insulin and sulphonylureas, it may be the first-line pharmacological therapy of choice in these patients.
7,395 citations
TL;DR: Losartan conferred significant renal benefits in patients with type 2 diabetes and nephropathy, and it was generally well tolerated.
Abstract: Background Diabetic nephropathy is the leading cause of end-stage renal disease. Interruption of the renin–angiotensin system slows the progression of renal disease in patients with type 1 diabetes, but similar data are not available for patients with type 2, the most common form of diabetes. We assessed the role of the angiotensin-II–receptor antagonist losartan in patients with type 2 diabetes and nephropathy. Methods A total of 1513 patients were enrolled in this randomized, double-blind study comparing losartan (50 to 100 mg once daily) with placebo, both taken in addition to conventional antihypertensive treatment (calcium-channel antagonists, diuretics, alpha-blockers, beta-blockers, and centrally acting agents), for a mean of 3.4 years. The primary outcome was the composite of a doubling of the base-line serum creatinine concentration, end-stage renal disease, or death. Secondary end points included a composite of morbidity and mortality from cardiovascular causes, proteinuria, and the rate of prog...
6,547 citations