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We have investigated the cellular basis for the clinical and epidemiologic linkage of hypertension, left ventricular hypertrophy (LVH), obesity, and non-insulin-dependent diabetes mellitus (NIDDM) and have studied cytosolic free calcium and free magnesium levels in these syndromes. Specifically, intracellular free calcium is elevated and free magnesium is deficient in hypertension, and both are related (directly and inversely, respectively) to the ambient level of blood pressure, to LV mass index (and thus to the degree of cardiac hypertrophy), and to the hyperinsulinemia and insulin resistance of essential hypertension. Dynamically, the ability of dietary salt loading to elevate blood pressure corresponds to its ability to elevate cytosolic free calcium and reciprocally to suppress free magnesium levels. Conversely, the ability of calcium channel blockade to reverse salt-induced hypertension is related to its ability to prevent these transmembrane ionic effects. Higher steady-state free calcium or lower free magnesium, or both, are also observed in clinical states linked to hypertension, such as obesity and NIDDM. Oral glucose loading in normal subjects itself elevates free calcium and suppresses free magnesium levels, as does hyperglycemia in vitro. These data suggest an ionic hypothesis of cardiovascular and metabolic disease, in which a generalized defect in cell ion handling is present in all tissues, resulting in higher steady-state free calcium and lower free magnesium levels. In pancreatic beta cells, this would produce hyperinsulinemia; in fat and skeletal muscle, cause peripheral insulin resistance; and in renal tissue, increase proximal sodium resorption and increase urinary calcium excretion--all features of essential hypertension. In vascular smooth muscle, high cytosolic free calcium would increase smooth muscle tone and cause vasoconstriction, and in heart muscle, independent of blood pressure, would increase contractility and predispose to LVH. Therefore, what may appear clinically to be the separate syndromes of hypertension, obesity, and NIDDM may pathophysiologically be different manifestations of the same underlying cellular defect, thus explaining their frequent clinical coexistence. Therapeutically, reversal of this excess free calcium accumulation and/or free magnesium deficit with ion-specific agents, such as calcium channel blocking drugs, may thus ameliorate not only the elevated blood pressure of hypertension but also the concurrent excess morbidity and mortality of the concurrent cardiac, vascular, and metabolic aspects of the hypertensive state.
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PMID:Cellular calcium and magnesium metabolism in the pathophysiology and treatment of hypertension and related metabolic disorders. 138 62

A spontaneously diabetic rat with polyuria, polydipsia, and mild obesity was discovered in 1984 in an outbred colony of Long-Evans rats, which had been purchased from Charles River Canada (St. Constant, Quebec, Canada) in 1982. A strain of rats developed from this rat by selective breeding has since been maintained at the Tokushima Research Institute (Otsuka Pharmaceutical, Tokushima, Japan) and named OLETF. The characteristic features of OLETF rats are 1) late onset of hyperglycemia (after 18 wk of age); 2) a chronic course of disease; 3) mild obesity; 4) inheritance by males; 5) hyperplastic foci of pancreatic islets; and 6) renal complication (nodular lesions). Histologically, the changes of pancreatic islets can be classified into three stages: 1) an early stage (6-20 wk of age) of cellular infiltration and degeneration; 2) a hyperplastic stage (20-40 wk of age); and 3) a final stage (at > 40 wk of age). These clinical and pathological features of disease in OLETF rats resemble those of human NIDDM.
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PMID:Spontaneous long-term hyperglycemic rat with diabetic complications. Otsuka Long-Evans Tokushima Fatty (OLETF) strain. 139 18

Glucoregulation and body composition were examined in 3-mo-old C57BL/6 ob/ob mice 6 wk after streptozotocin (STZ) or STZ plus adrenalectomy. STZ depressed somatic growth in ob/ob mice but did not cause hyperglycemia until immunoreactive insulin (IRI) was 40% (100 microU/ml) that of intact ob/ob mice. When IRI approached that of lean mice (40 microU/ml), ob/ob mice displayed severe hyperglycemia (800+ mg/dl) and other sequelae of type I diabetes but still maintained the same 50% body fat as untreated obese mice. In contrast, STZ diabetes in lean mice caused disproportionate reductions in body fat. Adrenalectomy before STZ led to the same insulinopenia, depressed growth, and hyperglycemia as STZ alone, but, after combined treatment, percent body fat declined in proportion to IRI. Thus a subgroup of severely diabetic adrenalectomized STZ obese mice with very low IRI (20 microU/ml) had body fat contents and fat-free masses equal to those of weight-matched lean mice. The data suggest that hypercorticoidism rather than hyperinsulinemia is largely responsible for obesity in ob/ob mice. However, in the absence of adrenal glucocorticoids, or perhaps with just their normalization, hyperinsulinemia appears necessary for maintaining excessive body energy stores.
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PMID:Interactions between insulin and glucocorticoids in the maintenance of genetic obesity. 141 35

An increased risk of developing premature atherosclerosis is associated with stress, diabetes, obesity, and hypertension. These conditions are associated with insulin resistance, hyperglycemia, hypertriglyceridemia and hypercholesterolemia. An alternative way of interpreting insulin resistance is to consider that metabolism in this condition would be regulated to a greater extent by stress hormones and in particular by cortisol. Glucocorticoids and fatty acids (which are produced in response to stress) antagonise the actions of insulin in promoting glucose uptake and protein synthesis, in decreasing gluconeogenesis and protein catabolism, and promoting the clearance of intermediate density lipoprotein and low density lipoprotein from the circulation by the liver. They also promote the secretion of very low density lipoprotein thus producing hypertriglyceridemia and hypercholesterolemia. By contrast to this antagonism, cortisol can also facilitate the action of insulin in stimulating the storage of energy via glycogen and fatty acid synthesis and through lipoprotein lipase in adipose tissue. These effects are significant in relation to obesity and to weight gain. An increased control of metabolism by cortisol therefore produces changes in metabolism that are potentially atherogenic and it is associated with insulin resistance and the other risk factors for atherosclerosis. Benfluorex treatment improves insulin sensitivity and has antihyperglycemic and hypolipidemic effects in human beings and in experimental animals. These effects can be observed independently of weight loss, but lowering food intake also produces a metabolic benefit. Long-term treatment with benfluorex can also decrease stress responses in terms of glucocorticoid release and the stimulation of lipolysis probably by its serotoninergic control of the hypothalamic-pituitary-adrenal axis. Such an action provides for an integrated treatment of the obese-diabetic-hyperlipidemic syndrome. Benfluorex produces overall changes in metabolism that tend to normalise the major risk factors associated with premature atherosclerosis. This provides a potential advantage over other therapies for atherosclerosis which may ameliorate a symptom (e.g., hyperlipidemia) without treating the underlying metabolic disturbance that predisposes to atherogenesis.
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PMID:[Mode of action of benfluorex. Recent data]. 143 2

The aim of this study was to evaluate the prevalence of arterial hypertension and other risk factors in patients suffering from peripheral arterial disease (PAD) in two clinical samples (1.: 102 patients with PAD 69 M, 33 F, studied in our angiology laboratory, matched for sex and age with 102 healthy volunteers; 2.: 184 hospitalized patients, 80 M, 104 F, mean age 57.2 +/- 10.8, with PAD) and in two epidemiological cohorts (1.: Trabia Study, 835 subjects; 2.: Casteldaccia Study, 723 subjects). All patients were subjected to a full clinical and laboratory examination, including the determination of the ankle/arm pressure ratio (Winsor index, positive for PAD when lower than 0.95). In the first clinical study we observed a significantly (p < 0.01) greater prevalence of arterial hypertension (51.9 vs 9.8%), hypercholesterolemia (48.2 vs 21.6%), hypertriglyceridemia (53.7 vs 26.1%), smoking habit (64.3 vs 44.2%), and hyperglycemia (26 vs 7,9%) in PAD patients than in controls. In the second clinical study considering separately the patients under and over 65 years, all risk factors resulted to be more prevalent in younger people than in the aged, except for diabetes and hypertension. In our epidemiological experience, the prevalence of PAD increases with aging, above all in males. In the Trabia Study the risk factors, more associated with PAD, were hypercholesterolemia, smoking and obesity (41.18%) in males and hypertension and hypercholesterolemia (33.3%) and obesity (25%) in females. In the Casteldaccia Study the most important risk factors were smoking (64.28%), hypercholesterolemia (42.86%) and hypertriglyceridemia (35.71%) in males, and obesity (60%), hypercholesterolemia (30%) and diabetes (20%) in females. Cholesterol levels and smoking were significantly higher in PAD patients than in the general population, whereas hypertriglyceridemia and glycemia were not. Arterial hypertension was significantly associated with PAD in the Trabia but not in the Casteldaccia Study. Obesity was significantly associated to PAD in females in both studies. In the Casteldaccia Study, lower HDL-cholesterol levels were observed in PAD patients, above all in males, whereas significantly greater Apo-B values and lower Apo-A1 levels (in males) were shown. The different levels of associated risk factors and their prevalence in PAD patients confirm the multifactorial pathogenesis of atherosclerosis. The exact role of each risk factor in the genesis of PAD is difficult to be evaluated due to the complex biological and statistical interrelationships among different risk factors. However, the management of associated risk factors may favourably influence the risk profile in each patient suffering from PAD.
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PMID:Prevalence of risk factors in patients with peripheral arterial disease. A clinical and epidemiological evaluation. 146 Mar 57

Patients with diabetes mellitus are at increased risk of morbidity and mortality from macrovascular disease manifesting as coronary heart disease, cerebrovascular accidents, and peripheral vascular disease. Increased frequency of dyslipidemia, hyperglycemia, obesity, hypertension, and associated nephropathy may contribute to accelerated atherogenesis in diabetic patients. Therefore, besides intensive control of hyperglycemia, management of dyslipidemia, hypertension, and obesity should also be emphasized in diabetic patients. Those who smoke should be strongly encouraged to quit smoking. Besides attempts to achieve normal levels of plasma lipoproteins, consideration also should be given to normalization of compositional abnormalities of various lipoproteins in patients with diabetes mellitus. The therapeutic goals for cholesterol reduction should be lower in diabetic patients than nondiabetic subjects. The first step is to achieve good metabolic control of diabetes mellitus by diet, exercise, and weight reduction and, if needed, with sulfonylureas or insulin therapy. Because most of the patients with insulin-dependent diabetes mellitus achieve normal levels of plasma lipoproteins with intensive insulin therapy, lipid-lowering medications are rarely needed. In patients with non-insulin-dependent diabetes mellitus, however, dyslipidemia often persists despite good glycemic control. Lipid-lowering medications should be considered in such patients. Because nicotinic acid can cause marked deterioration in glycemic control, and bile acid-binding resins may accentuate hypertriglyceridemia, these agents are less desirable for use by diabetic patients. Inhibitors of hydroxymethylglutaryl coenzyme A reductase may be preferred in patients with elevated LDL cholesterol and mld hypertriglyceridemia. For diabetic patients with marked hypertriglyceridemia, however, fibric acid derivatives should be the drug of choice.
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PMID:Lipid-lowering therapy and macrovascular disease in diabetes mellitus. 152 29

By the term "insulin resistance" we understand the attenuation of insulin-stimulated glucose uptake, which is mainly due to attenuated glycogen synthesis in skeletal muscle and is partially compensated with regard to plasma glucose homeostasis by hyperinsulinemia. Other mechanisms of insulin are either not attenuated or are less so and may contribute via hyperinsulinemia to the prevalence of hypertension, obesity, dyslipoproteinemia and type-II diabetes. At the level of insulin receptors, resistance can be due to muscle-specific, preferential expression of the low-affinity B-isoform of the insulin receptors. In rare cases of extreme resistance, it can also be due to several mutations at the insulin receptor gene or due to insulin-receptor autoantibodies. At the postreceptor level, the translocation and or expression of the insulin-responsive glucose carrier GluT-4 can be down-regulated via the hexosamine pathway by hyperglycemia plus hyperinsulinemia. Furthermore, Glut-4 can be inhibited and/or down-regulated by sustained insulin deficiency, partially via c-AMP-dependent pathways. Additionally, the insulin-induced glycogen synthesis in skeletal muscle can be attenuated by the endogenous peptides amylin and calcitonin-gene-related peptide, and by modulations of endothelial function, perfusion and capillary recruitment in the microcirculation of skeletal muscle. Epidemiological data indicate a genetic predisposition for insulin resistance. However, among the many mechanisms potentially contributing to the complex syndrome of insulin resistance, no specific localization of that predisposition can be proposed at present.
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PMID:[The mechanisms of insulin resistance]. 153 3

Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages.
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PMID:Timed bromocriptine administration reduces body fat stores in obese subjects and hyperglycemia in type II diabetics. 154 54

The development of the obesity-associated hyperglycemic syndrome in ob/ob mice, genetically determined, was observed over time by a combined functional and structural study of pancreatic islets. Islet areas increased with advancing age in ob/ob mice from 2 times at 1 month to 30 times at 6 months of age the size of lean mouse islets. Islet areas apparently increased more than pancreatic insulin content in ob/ob mice. Glucose and insulin tolerance tests were performed to study in vivo responses to glucose and insulin, respectively, in 1-, 3-, and 6-month-old mice. With ob/ob mice, glucose tolerance tests revealed more elevation of plasma glucose than in lean mice, the lean mice revealing more elevated plasma insulin than the obese mice. In insulin tolerance tests, lean mice presented marked hypoglycemia, whereas ob/ob mice revealed slightly higher plasma glucose at 1 month of age but three to four times higher amounts than that of lean mice at 6 months of age. Thus, increasing insulin resistance in ob/ob mice older than 3 months is associated with progressively increasing islet area, which contains proportionally less insulin than that of lean mouse pancreas. The data suggest that insulin resistance in ob/ob mice progressively develops up to 6 months of age and that marked islet hyperplasia is likely in response to sustained hyperglycemia, leading to hyperinsulinemia and eventual marked obesity.
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PMID:Pancreatic islets of obese hyperglycemic mice (ob/ob). 159 59

Non-insulin-dependent diabetes (NIDDM) has long been recognized as being associated with a cluster of disorders including obesity, hypertension, dyslipidemia, and atherosclerotic heart disease. It was only recently, however, that Reaven, DeFronzo, and Ferrannini with techniques to quantitate insulin resistance suggested that this represents a common factor in this group of disorders and that hyperinsulinemia resulting from insulin resistance could be the cause of the hypertension, dyslipidemia, and atherosclerosis. The names syndrome X or the insulin-resistance syndrome have been used to identify this pathological entity, and considerable investigations have been done and are in progress to establish whether or not these coexisting disorders represent an as yet unexplained association of cardiovascular risk factors or if, indeed, insulin resistance and hyperinsulinism represent the primary cause for most of the other disorders. To paraphrase a philosophical comment, if syndrome X did not exist, we probably would have had to invent it. In addition to the intellectual satisfaction of being able to "lump" these diverse ills under a single etiology, the main value of grouping these disorders as a syndrome is to continually remind physicians that the therapeutic goals are not only to correct hyperglycemia in NIDDM but also to manage the elevated blood pressure and dyslipidemia that cause cerebrovascular and cardiac morbidity as well as mortality in these patients. Having a syndrome X reduces the fragmentation of medical care among subspecialties and decreases the likelihood of prescribing drugs that correct hypertension but raise lipids or drugs that lower lipids but raise blood glucose. Finally, it encourages the selection of drugs that reduce hyperglycemia without increasing insulin secretion and to the development of new drugs for this purpose. Unfortunately, the concept of insulin resistance with hyperinsulinism being a cause of the other associated disorders is still unproved but continues to be open to experimental investigation. The remainder of this article reviewed the use of sulfonylureas in the management of NIDDM, discussed new molecular and cellular mechanisms by which they promote insulin secretion, and reviewed the controversy as to whether an extrapancreatic action contributes to their glucose-lowering effects in NIDDM. A closing section listed some other oral drugs that can lower blood glucose without stimulating the pancreatic beta cell. Their insulin-sparing hypoglycemic effect makes them potentially useful in NIDDM therapy, particularly if the fundamental premise of syndrome X is substantiated, which implicates hyperinsulinemia as contributing to the morbidity and mortality from atherosclerotic vascular disease.
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PMID:Type II diabetes and syndrome X. Pathogenesis and glycemic management. 161 69


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