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Query: UMLS:C0011849 (diabetes)
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Insulin resistance was already suspected in the thirties from clinical observations in diabetic patients, then better appreciated in the early sixties with the development of insulin radioimmunoassay, and finally confirmed in the last 20 years by using various sophisticated methods able to quantify insulin action. First demonstrated in obese and/or type 2 diabetic patients, the diminution of insulin sensitivity may in fact concern a much larger population. The concept of insulin sensitivity gained a considerable importance when Reaven, in 1988, emphasized the role of insulin resistance in different human diseases. The metabolic syndrome or syndrome X is characterized by the association of various cardiovascular risk factors (among which impaired glucose tolerance, arterial hypertension and dyslipidaemias), all closely linked to insulin resistance which is indeed the core of the syndrome. Even if insulin action signalling appears to be rather complex and the mechanisms leading to insulin resistance still largely unknown, it is essential to develop pharmacological or non pharmacological strategies to improve insulin sensitivity for treating insulin-resistant individuals. Such an approach should allow not only to provide a better blood glucose control in patients with type 2 diabetes, but also to improve the cardiovascular prognosis of numerous patients, with or without diabetes mellitus, who have the metabolic syndrome.
Diabetes Metab 2001 Apr
PMID:[The insulin sensitivity concept]. 1145 10

There is now much interest in the mechanisms by which altered lipid metabolism might contribute to insulin resistance as is found in Syndrome X or in Type II diabetes. This review considers recent evidence obtained in animal models and its relevance to humans, and also likely mechanisms and strategies for the onset and amelioration of insulin resistance. A key tissue for development of insulin resistance is skeletal muscle. Animal models of Syndrome X (eg high fat fed rat) exhibit excess accumulation of muscle triglyceride coincident with development of insulin resistance. This seems to also occur in humans and several studies demonstrate increased muscle triglyceride content in insulin resistant states. Recently magnetic resonance spectroscopy has been used to demonstrate that at least some of the lipid accumulation is inside the muscle cell (myocyte). Factors leading to this accumulation are not clear, but it could derive from elevated circulating free fatty acids, basal or postprandial triglycerides, or reduced muscle fatty acid oxidation. Supporting a link with adipose tissue metabolism, there appears to be a close association of muscle and whole body insulin resistance with the degree of abdominal obesity. While causal relationships are still to be clearly established, there are now quite plausible mechanistic links between muscle lipid accumulation and insulin resistance, which go beyond the classic Randle glucose-fatty acid cycle. In animal models, dietary changes or prior exercise which reduce muscle lipid accumulation also improve insulin sensitivity. It is likely that cytosolic accumulation of the active form of lipid in muscle, the long chain fatty acyl CoAs, is involved, leading to altered insulin signalling or enzyme activities (eg glycogen synthase) either directly or via chronic activation of mediators such as protein kinase C. Unless there is significant weight loss, short or medium term dietary manipulation does not alter insulin sensitivity as much in humans as in rodent models, and there is considerable interest in pharmacological intervention. Studies using PPARgamma receptor agonists, the thiazolidinediones, have supported the principle that reduced muscle lipid accumulation is associated with increased insulin sensitivity. Other potent systemic lipid-lowering agents such as PPARalpha receptor agonists (eg fibrates) or antilipolytic agents (eg nicotinic acid analogues) might improve insulin sensitivity but further work is needed, particularly to clarify implications for muscle metabolism. In conclusion, evidence is growing that excess muscle and liver lipid accumulation causes or exacerbates insulin resistance in Syndrome X and in Type II diabetes; development of strategies to prevent this seem very worthwhile.
Exp Clin Endocrinol Diabetes 2001
PMID:Triglycerides, fatty acids and insulin resistance--hyperinsulinemia. 1145 39

Animal models for insulin resistance and type 2 diabetes are required for the study of the mechanism of these phenomena and for a better understanding of diabetes complications in human populations. Type 2 diabetes is a syndrome that affects 5-10% of the adult population. Hyperinsulinaemia, hypertriglyceridaemia, decreased high-density lipoprotein (HDL) cholesterol levels, obesity and hypertension, all form a cluster of risk factors that increase the risk of coronary artery disease, and are known as insulin resistance syndrome or syndrome X. The gerbil, Psammomys obesus is characterized by primary insulin resistance and is a well-defined model for dietary induced type 2 diabetes. Weanling Psammomys and Albino rats were held individually for several weeks on high energy (HE) and low energy (LE) diets in order to determine the development of metabolic changes leading to diabetes. Feeding Psammomys on HE diet resulted in hyperglycaemia (303 +/- 40 mg/dl), hyperinsulinaemia (194 +/- 31 microU/ml) and a moderate elevation in body weight, obesity and plasma triglycerides. Albino rats on HE diet demonstrated an elevation in plasma insulin (30 +/- 4 microU/ml), hypertriglyceridaemia (170 +/- 11 mg/dl), an elevation in body weight and obesity, but maintained normoglycaemia (98 +/- 6 mg/dl). Psammomys represent a model that is similar to human populations, with primary insulin resistance expressed in young age, which leads to a high percentage of adult type 2 diabetes. Examples for such populations are the Pima Indians, Australian Aborigines and many other Third World populations. The results indicate that the metabolism of Psammomys is well adapted towards life in a low energy environment, where Psammomys takes advantage of its capacity for a constant accumulation of adipose tissue that will serve for maintenance and breeding in periods of scarcity. This metabolism known as 'thrifty metabolism', is compromised at a high nutrient intake.
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PMID:Psammomys obesus and the albino rat--two different models of nutritional insulin resistance, representing two different types of human populations. 1166 19

Resistin, the peptide specifically secreted from adipocytes, is a hormone antagonistic to insulin action and, thus, may serve as a link between human obesity due to adiposity and insulin resistance associated with type 2 diabetes. To test this hypothesis, we studied the gene expression of resistin in adipocytes isolated from rats fed with a fructose diet which induced insulin resistance. Compared to the control rats (C) on a normal chow diet, the fructose-fed rats (F) developed hyperinsulinemia, glucose intolerance, hypertriglyceridemia and hypertension, a profile reminiscent of the syndrome X of patients with non-insulin-dependent diabetes mellitus (NIDDM). The F rats had significantly elevated plasma free fatty acids (FFA), enlarged epididymal fat pads, and increased adipocyte size compared with the C rats. We examined the glucose transport and the relative quantity of resistin mRNA produced in the adipocytes of these two groups of rats. Compared to the C rats, the F rats had a clearly reduced insulin-stimulated glucose transport. The gene expression of resistin and other adipocyte peptides was measured on the mRNA by semiquantitative RT-PCR; the validity of this technique was established in advance with a rat-fasting and then refeeding experiment. The F rats showed a decreased expression of the resistin gene, whereas gene expression of leptin and angiotensinogen in contrast increased. Free fatty acids were found to suppress the expression of resistin gene in normal rat adipocytes. These results demonstrate that an insulin-resistant instance in the fructose diet rat model exists with the decreased gene expression of resistin.
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PMID:Suppressed gene expression of adipocyte resistin in an insulin-resistant rat model probably by elevated free fatty acids. 1174 41

A major debate is currently taking place on the world diabetes scene on the merits of fasting versus 2-hour postprandial glucose concentrations as a reference point for the diagnosis of diabetes. Other time points of the oral glucose tolerance test on the other hand, seem to attract little attention. In Saudi Arabia however, we have been intrigued by the scale and severity of hyperglycemia observed at one-hour following glucose load. Plasma glucose concentration one-hour postprandially is strikingly abnormal amongst native Saudis and interestingly, is associated with insulin resistance and features of syndrome X. Such observations have prompted us to call into question the wisdom of current practices, namely of excluding the one-hour plasma glucose concentration in the diagnosis of diabetes. In the proceeding article therefore, we describe in detail our local observations and debate the wider scientific and historical issues surrounding the place of one-hour glucose concentration as a potentially useful diagnostic point in the detection and classification of glucose intolerance.
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PMID:The diagnosis of diabetes mellitus. A contest between 3 points! 1174 37

The occurrence of insulin resistance syndrome (syndrome X) is common in the general population. However, information is scant on the childhood predictors of syndrome X. This study examined the relative contribution of childhood adiposity and insulin to the adulthood risk of developing syndrome X in a biracial (black-white) community-based longitudinal cohort (n = 745; baseline age, 8-17 years; mean +/- SD follow-up period, 11.6 +/- 3.4 years). The four criterion risk variables considered were the highest quartile (specific for age, race, sex, and study year) of 1) BMI, 2) fasting insulin, 3) systolic or mean arterial blood pressure, and 4) total cholesterol to HDL cholesterol ratio or triglycerides to HDL cholesterol ratio. Clustering was defined as the combination of all four risk variables. In addition to the criterion risk variables, clustered adults had adverse levels of total cholesterol, triglycerides, LDL cholesterol, HDL cholesterol, diastolic blood pressure, and glucose compared with those who did not cluster (P < 0.001). Childhood variables, except glucose, showed adverse trends with increasing number of criterion risk variables present in adulthood (P for trend, 0.01-0.0001). The proportion of individuals who developed clustering as adults increased across childhood BMI (P for trend <0.0001) and insulin (P for trend <0.01) quartiles. The relationship to childhood BMI remained significant even after adjusting for childhood insulin. In contrast, corresponding association with childhood insulin disappeared after adjusting for childhood BMI. In a logistic regression model, childhood BMI and insulin were significant predictors of adulthood clustering, with BMI being the strongest and showing a curvilinear relationship. Using an insulin resistance index instead of insulin did not change the above findings. These results indicate that childhood obesity is a powerful predictor of development of syndrome X and underscore the importance of weight control early in life.
Diabetes 2002 Jan
PMID:Predictability of childhood adiposity and insulin for developing insulin resistance syndrome (syndrome X) in young adulthood: the Bogalusa Heart Study. 1175 42

Type II diabetes and hypertension are two pathologies which are frequently associated in adults, especially in developed countries. All the more so when patients are also obese: obesity is today, and will be in the next future, a true epidemic in these countries. These three pathologies imply a risk for cardiovascular complications much higher than that due to an isolated arterial hypertension. This increased risk is probably due to many factors: hyperglycemia, a dismetabolic syndrome (hyperlipemia, hyperuricemia, thrombophilia, altered Na(+)-H+ membrane exchanges = syndrome X) and hyperinsulinemia which favor atherosclerosis and clinical events. Consequently non-pharmacological and aggressive pharmacological therapy is necessary. Even if the trials done in the last years are questionable and not totally convincing, all researchers agree that lowering blood pressure to normality is the best way to improve prognosis of these patients. Usually for this purpose we need a therapy with more than one drug. Among the antihypertensive drugs, ACE-inhibitors (and perhaps also angiotensin receptor blockers) are preferred, especially in those hypertensives with diabetes who have also microalbuminuria or a frank proteinuria.
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PMID:[Diabetes and arterial hypertension]. 1177 8

Human hypertension is a common and complex disease and is associated with diabetes, cardiovascular, and renal disease. Therefore, it is important to understand the genetic basis of this disease. Specific genetic mutations leading to monogenic forms of hypertension have been identified in Liddle's syndrome and glucocorticoid-remediable hypertension and in some syndromes in which blood pressure is lowered. Because essential hypertension is a polygenic disease, elucidating a genotype that is causally related to essential hypertension will be difficult. To date, no genotype has been conclusively linked to essential hypertension except in certain populations. However, there has been progress in finding genetic variations that are associated with hypertension in patients with components of the metabolic syndrome (or Syndrome X). Future discoveries in this area should enhance our ability to intervene earlier and more effectively and therefore lessen the complications of this common disease.
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PMID:The genetics of human hypertension. 1178 66

Recent evidence from the United Kingdom Prospective Diabetes Study convincingly demonstrates that good glycaemic control is difficult to achieve and, despite its positive impact on microvascular complications, is not sufficient to reduce the risk of coronary heart disease (CHD). Syndrome X--a cluster of abnormalities associated with resistance to insulin-mediated glucose uptake that have been implicated in accelerating atherogenesis--provides a useful clinical concept to prevent CHD in patients with type 2 diabetes. Components of syndrome X can include hypertension, hyperinsulinaemia, dyslipidaemia, and a procoagulant state, changes that contribute to the development of atherosclerosis. Low-density lipoprotein cholesterol (LDL-C) levels are usually close to normal, but the LDL-C is present in abnormally small and dense particles. Triglyceride levels are elevated and are associated with an increase in postprandial accumulation of atherogenic, remnant lipoprotein particles. High-density lipoprotein cholesterol levels are typically low. This particular dyslipidaemia, along with hyperinsulinaemia, induces expression of plasminogen activator inhibitor-1, contributing to a prothrombotic state. In addition, plaque formation may be accelerated in insulin-resistant subjects by increased expression of adhesion molecules on endothelial cells and increased rate of monocyte adhesion to cultured endothelial cells. Syndrome X and type 2 diabetes are associated with multiple abnormalities that enhance the atherosclerotic process. The opportunities for new therapeutic approaches to reduce cardiovascular risk will undoubtedly evolve along with our understanding of the complex factors responsible for insulin resistance, compensatory hyperinsulinaemia, and CHD.
Diabetes Obes Metab 2002 Jan
PMID:Multiple CHD risk factors in type 2 diabetes: beyond hyperglycaemia. 1184 50

Metabolic Syndrome X defined by Reaven is caused by peripheral insuline receptor resistance, leads to hyperinsulinemia regarded as a cause of secondary dyslipidemia, hypertension, hemostatic disturbances, atherosclerosis and insulin as a growth factor takes part in carcinogenesis. Depending on a contribution of the primary risk factors of type 2 Diabetes Mellitus (2-DM) mainly genetic factors and obesity--an independent cause of insulin receptor resistance--glucose intolerance and 2-DM may overlap the Syndrome X. The aims of these studies were to determine in cross-sectional investigation a plasma insulin concentration in subjects aged over 35 years and to assess the clinical usefulness of insulinemia in early diagnosis of diabetes type 2. Investigations were carried out in Krakow town's district with 200,000 inhabitants, out of those 3060 randomly selected subjects (1720 females and 1340 males aged over 35 years) took part in the Polish Multicenter Study on Diabetes Epidemiology (PMSDE) with protocol and methods previously presented. Glucose concentration was determine by enzymatic method, insuline in plasma by IRMA method using ready kits produced by the Swierk-Poland. Logistic multiple regression model was used to estimate the effect of risk factors on the development of glucose intolerance, Chi square test, Fisher test and Mann-Whitney test were used for statistical analysis by means of statistical package BMPD. Fasting insulinemia in persons with normal glucose tolerance and body weight (BMI < 25 and glycemia < 6.1 mmol/l) in subpopulation aged over 35 years was 5.73 (SD = 3.99) in men and 7.05 (SD = 4.67) microU/ml in women. These values were positively correlated with BMI and at the range 25-30 and > 30 increased by 50 and 100% responsively and in 2-nd h in OGTT by five-times. In the persons with glucose intolerance and new-diagnosed 2-DM insulinemia increased 2-3 fold depending on BMI, and gender. In the subgroup with 2-DM and BMI > 30, insulinemia in 2 h-OGTT treated values 152 (SD = 90) in women and 112 (SD = 83.4) microU/ml in men. Obesity and insulinemia in 2 h-OGTT in multiple analysis have been identified as a strong predictors and risk factors of impaired glucose intolerance (IGT) 2-DM fasting insulinemia may be useful as an indicator of the peripheric insulin receptor resistance. The results lead to the conclusions that determination of the plasma insulin concentration may be useful in early diagnosis of IGT and diabetes type 2, and should be monitored in the course of non-pharmacological and pharmacological treatment 2-DM. One of the main goals in the course of treatment of obesity and early phases of the 2-DM should be normalization or at least reduction of hyperinsulinemia. Insulinemia may be regarded also as an important criterion for selection of the oral antidiabetic drugs.
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PMID:[Insulinemia--a marker of early diagnosis and control of efficacy of treatment of type II diabetes]. 1192 88


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