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Query: UMLS:C0028754 (obesity)
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Insulin resistance is seen in several pathophysiological conditions, such as obesity, diabetes mellitus, and essential hypertension. This means that a greater than normal amount of insulin is needed to give a normal biological response. A major biochemical defect in insulin resistance seems to be a defect in the intracellular nonoxidative metabolism of glucose in muscle cells. However, in many individuals, there is also increased hepatic glucose output. The result of insulin resistance in individuals with normal insulin-secreting capacity is hyperinsulinemia, a potential risk factor for cardiovascular disease.
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PMID:Carbohydrate metabolism, insulin resistance, and metabolic cardiovascular syndrome. 128 63

Diabetes mellitus is commonly associated with systolic and diastolic hypertension, and a wealth of epidemiological data suggest that this association is independent of age and obesity. Much evidence indicates that the link between diabetes and essential hypertension is hyperinsulinemia. Thus, when hypertensive patients, whether obese or of normal body weight, are compared with age- and weight-matched normotensive controls, a heightened plasma insulin response to a glucose challenge is found consistently. A state of cellular resistance to insulin action subtends the observed hyperinsulinism. Using the insulin/glucose clamp technique in combination with tracer glucose infusion and indirect calorimetry, it has been demonstrated that the insulin resistance of essential hypertension is located in peripheral tissues (muscle), is limited to nonoxidative pathways of glucose disposal (glycogen synthesis), and correlates directly with the severity of hypertension. The reasons for the association of insulin resistance and essential hypertension can be sought in at least four general types of mechanisms: sodium retention, sympathetic nervous system overactivity, disturbed membrane ion transport, and proliferation of vascular smooth-muscle cells. Physiological maneuvers, such as caloric restriction (in the overweight patient) and regular physical exercise, can improve tissue sensitivity to insulin; good evidence indicates that these maneuvers also can lower blood pressure in both normotensive and hypertensive individuals. Insulin resistance and hyperinsulinemia also are associated with an atherogenic plasma lipid profile. Elevated plasma insulin concentrations enhance very-low-density lipoprotein (VLDL) synthesis, leading to hypertriglyceridemia. Progressive elimination of lipid and apolipoproteins from the VLDL particle leads to an increased formation of intermediate density and low-density lipoproteins, both of which are atherogenic. Last, insulin per se, independent of its effects on blood pressure and plasma lipids, is known to be atherogenic. The hormone enhances cholesterol transport into arteriolar smooth-muscle cells and increases endogenous lipid synthesis by these cells. Insulin also stimulates the proliferation of arteriolar smooth-muscle cells, augments collagen synthesis in the vascular wall, increases the formation of and decreases the regression of lipid plaques, and stimulates the production of a variety of growth factors. In summary, insulin resistance appears to be a syndrome that is associated with a clustering of metabolic disorders, including type II diabetes mellitus, obesity, hypertension, lipid abnormalities, and atherosclerotic cardiovascular disease.
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PMID:Insulin resistance, hyperinsulinemia, and coronary artery disease: a complex metabolic web. 128 37

Insulin resistance is a frequent phenomenon and a marker of increased risk for non-insulin-dependent diabetes mellitus (NIDDM) and atherosclerosis. According to recent estimations, not only individuals with obesity, NIDDM, and impaired glucose tolerance (IGT) but also one fourth of the "healthy" glucose tolerant and the majority of the hypertensive population are insulin resistant. Insulin resistance describes a tissue- and pathway-specific defect of glucose metabolism that is compensated for by hyperinsulinemia, leading to a cluster of undesirable hypertensiogenic, diabetogenic, and atherogenic processes. The initial defect can be directly measured by glucose clamp and other sophisticated techniques; the clinical syndrome may be derived from a network of related variables known to be associated with reduced insulin action. Because neither clamps nor serum insulin screenings will be available on a widespread basis, early diagnosis based on clinical criteria is crucial. A new interpretation of the "thrifty" genotype hypothesis may explain why insulin resistance, which formerly apparently represented an advantage in the evolutionary selection process, is such a frequent phenomenon. Improvement of impaired insulin action as a therapeutic principle may play a future central role in an integrated lifestyle approach of primary prevention of noncommunicable diseases such as NIDDM, hypertension, and atherosclerosis.
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PMID:What is the clinical significance of insulin resistance? 128 40

Insulin resistance and hyperinsulinemia is now recognized in non-insulin-dependent diabetes, essential hypertension, obesity, atherosclerotic heart disease, dyslipidemia, heart failure, and in heavy smokers. Several mechanisms have been proposed to explain hyperinsulinemia, insulin resistance and its relationship to hypertension; reduced sodium excretion, activation of the sympathetic nervous system, increased activity of the sodium/hydrogen pump, and stimulation of cellular growth. Some of the nonpharmacological methods to control hyperinsulinemia are of benefit in the management of hypertension, most notably weight loss, exercise program, and reduced salt intake. High-fiber and reduced-protein diets also reduce hyperinsulinemia. Thiazide diuretics can result in insulin resistance, and insulin secretion may be inhibited, possibly associated with concomitant hypokalemia. beta-Blockers result in some reduction of glucose tolerance and mask some of the features of hypoglycemia. Angiotensin-converting enzyme (ACE) inhibitors and alpha-receptor blockers do not effect insulin resistance; probably the same is true for calcium antagonists. Although the effect on risk factors should not be discounted, it is the effect of treatment on hard end points, cerebrovascular accidents, myocardial infarction, or death that is most important. Evidence in hypertension is at present restricted to diuretics and beta-blocking drugs.
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PMID:Hypertension and insulin resistance. 128 47

Insulin sensitivity of insulin dependent tissues (muscle, adipose tissue, liver) is subject to a variety of influences. Any change in insulin sensitivity is compensated in healthy subjects by a dynamic change in insulin secretion, which will decrease following a rise in insulin sensitivity and increase if insulin sensitivity is impaired (i.e. during insulin resistance induced by obesity, pregnancy, oral contraceptives, dehydration, saturated fatty acids, fever, drugs, etc.). In contrast to secondary insulin resistance idiopathic insulin resistance in type 2 diabetic individuals is associated with impaired insulin secretion, which thus is unable to overcome impaired insulin sensitivity. Idiopathic insulin resistance in type 2 diabetes is additionally characterized by reduced glucose storage, the basis of which may reside in an insulin receptor defect, in the presence of insulin receptor antibodies, in a postreceptor defect or in the synthesis of abnormal insulin molecules.
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PMID:[Insulin resistance]. 129 Mar 22

Socioeconomic development and changes in lifestyles have been accompanied by the emergence of diabetes as a major problem in Eastern Mediterranean countries, but reliable epidemiological data are still scarce and comparability is generally poor. For non-insulin-dependent diabetes (NIDDM) in adults, risk is higher in urban than in rural subjects, and in all populations prevalence increases with advancing age. Whereas several surveys have reported prevalence of the order of 5%, a recent national survey in Oman, which used the full WHO criteria for diagnosis, based upon the 2 hour blood glucose concentration after a 75 g oral glucose load in all subjects, reported a prevalence of diabetes of 10% in those aged 20 years and over. A further 8% of men and 13% of women had impaired glucose tolerance (IGT). Insulin-dependent diabetes (IDDM) was reported to be considerably rarer in Kuwait than in Europe and North America, but some more recent data suggest variability in frequency within the region. IDDM is frequently accompanied by ketoacidosis at diagnosis. For NIDDM, 75% of cases are associated with obesity. Long-term complications appear to occur to the same extent as in Western countries. A recent WHO Task Force meeting has set goals and targets for diabetes prevention and control within the Eastern Mediterranean Region.
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PMID:Diabetes in the eastern Mediterranean region. 129 77

Insulin resistance was investigated in three obese boys with acanthosis nigricans and their results were compared to those obtained in non-acanthotic obese patients. Blood glucose immune reactive serum insulin and C-peptide during oral glucose tolerance test and 125I-insulin binding investigated. Obese patients with acanthosis nigricans were more insulin resistant than simple obese controls. Insulin binding studies performed in two acanthotic patients suggested that one of them had insulin resistance type A, and the second patient had insulin resistance type B. According to the results acanthosis nigricans can serve as a marker for severe insulin resistance in obesity.
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PMID:Insulin resistance in obese boys with acanthosis nigricans. 130 90

Early after lesion of the ventromedial hypothalamus nuclei (VMH), insulin-induced glucose utilization is increased in white adipose tissue (WAT), whereas oxidative and glycolytic muscles are, respectively, normoresponsive or resistant to insulin. Five weeks later, all of the muscles are resistant, whereas WAT returns to normal responsiveness. The aim of this study was to characterize the insulin receptor kinase activity in WAT and muscles 1 and 6 wk after lesion. The number and affinity of insulin receptors were not modified in any of the tissues studied. Autophosphorylation and phosphorylation of an exogenous substrate were similar in oxidative and glycolytic muscles of VMH and control rats both 1 and 6 wk after the lesion. Insulin receptors from WAT of 1-wk VMH rats exhibited a 2.5-fold increase in insulin-stimulated autophosphorylation and phosphorylation. Six weeks after the lesion, both autophosphorylation and phosphorylation returned to normal values. This suggests that insulin receptor tyrosine kinase activity does not play a significant role in the insulin resistance of skeletal muscles but has a crucial role in mediating the variations of insulin action on WAT observed during the development of VMH obesity.
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PMID:Insulin receptor kinase activity in muscles and white adipose tissue during course of VMH obesity. 131 7

In both humans and rodents the occurrence and severity of obesity-associated non-insulin dependent diabetes mellitus (NIDDM) may be influenced by both gonadal hormones and genetic background. Early gonadectomy (at 3-5 days of age) of female and male Wistar diabetic fatty (WDF) rats and of male Zucker rats allowed us to examine these effects in genetically obese rats carrying the fatty (fa) gene. Impairment of glucose tolerance and insulin sensitivity by obesity, and amelioration or exacerbation (in the case of female rats) of this impairment by gonadectomy were assessed by intragastric glucose tolerance tests when the rats reached adulthood. Both glucose tolerance and insulin sensitivity were significantly deranged in obese WDF rats of both sexes and in obese male Zucker rats compared to lean controls of the same sex and strain. Obese male WDF rats were less glucose tolerant and insulin sensitive than were obese male Zucker rats. Glucose intolerance was not ameliorated by castration in lean or obese male WDF or Zucker rats. Insulin sensitivity was significantly improved by castration in obese male rats of both strains, as fasting plasma insulin levels and total areas under the insulin curves were significantly reduced compared to obese sham-operated controls. This effect was greater in the Zucker than in the WDF male rats. Castration significantly decreased the insulin response areas in obese male Zucker rats, but did not alter those of the obese male WDF rats. Ovariectomy did not alter glucose homeostasis of obese female WDF rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The effects of gonadectomy on glucose tolerance of genetically obese (fa/fa) rats: influence of sex and genetic background. 131 24

Points of agreement: (1) In IDDM, hypertension occurs in patients who have already developed nephropathy, probably in the microalbuminuric phase. (2) Hypertension is an important accelerator of the development of diabetic nephropathy. (3) Hypertension, obesity and NIDDM are often associated, and insulin resistance is commonly observed in all three states. (4) Antihypertensive therapy retards the development of diabetic nephropathy in IDDM and reduces proteinuria in NIDDM. (5) The choice of antihypertensive agent in the diabetic patient must be based upon the efficacy of the drug as well as avoidance of side effects including deleterious influence on glucose, insulin and lipid levels and renoprotection. (6) Carefully conducted long-term comparative trials between different classes of antihypertensive drugs in microalbuminuric IDDM and NIDDM patients are essential. Points of major controversy: (1) Detection of IDDM patients prone to the development of diabetic nephropathy can be performed by measuring specific parameters such as erythrocyte Na(+)-Li+ countertransport activity. (2) Insulin resistance is a pathogenic mechanism rather than purely an association with hypertension and obesity. (3) A certain class of antihypertensive agents--ACE inhibitors--confers a specific renoprotective effect in diabetic nephropathy, in addition to its effects upon systemic blood pressure. (4) Reduction of blood pressure should be considered in the normotensive microalbuminuric diabetic patient. (5) Microalbuminuria is a sufficient 'surrogate endpoint' for the progression of renal failure.
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PMID:Meeting report of the International Society of Hypertension Conference on Hypertension and Diabetes. 131 6


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