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Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The local cerebral glucose utilization (LCGU) of control and 2 day corticosterone-administered rats was investigated using the method of Sokoloff (labelled 2-deoxy-D-glucose). The overall LCGU of both groups was similar, but discrete areas of the corticosterone-administered rat brains displayed both increases and decreases in their utilization of 2-deoxyglucose. These areas were associated with the limbic cortex and included the hippocampus, the septum and some thalamic and hypothalamic nuclei. It is well known that these regions are interconnected and that acetylcholine is one of the main neurotransmitters. Some of these pathways (as measured electrophysiologically) have reportedly inhibitory influences, whilst others have excitatory ones within the limbic region. It was therefore striking to observe that these inhibitory or stimulatory effects were corroborated by a selective, corticosterone-induced decrease or increase in 2-deoxyglucose uptake, respectively. This gives corticosterone a putative role in the regulation of the limbic system. As the latter has been reported to be abnormal in genetically obese hypercorticosteronemic fa/fa rats, it is suggested that these corticosterone-induced changes within the limbic system may contribute to the overall phenotypic expression of this obesity state.
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PMID:Effects of corticosterone administration on local cerebral glucose utilization of rats. 806 85

We have previously shown that the glucose intolerance and the hyperglycemic state in the GK rat, a new spontaneous model of non-insulin-dependent (type II) diabetes without obesity, are partly accounted for by an alteration of the pancreatic B cell response. On the other hand, the hyperglycemic-hyperinsulinemic pattern in these rats suggests a decrease of response to insulin in the basal state. In the present study, in vivo insulin action was assessed in 8-wk-old GK females at basal and submaximal (euglycemic clamp) insulin levels. Overall glucose utilization (OGU), individual tissue glucose utilization (ITGU, in vivo uptake of the glucose analogue 2-deoxy-D-glucose as the relative index of glucose metabolism), as well as hepatic glucose production (GP) and liver insulin receptor properties were determined under these two conditions. The basal OGU was significantly higher in the GK females, compared with that in control Wistar females. The hyperinsulinemic-euglycemic clamp experiments indicated that peripheral insulin resistance was installed at 8 wk of age in the GK females because 1) OGU was significantly lower and 2) in some peripheral tissues (epitrochlearis muscle, periovarian, and inguinal white adipose tissues), but not all, ITGU was significantly lower compared with corresponding ITGU in control rats. In the basal state GP was significantly higher in the GK rats. At submaximal hyperinsulinemia (and euglycemia), it was less effectively suppressed than in the controls, thus demonstrating liver insulin resistance. Under both basal state and clamp condition, binding of 125I-A14-insulin to liver membranes of GK rats was significantly decreased by 20-30%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Insulin resistance in the GK rat: decreased receptor number but normal kinase activity in liver. 823 7

The obese diabetic SHR/N-cp rat is a newly developed strain that inherits obesity as an autosomal recessive trait. These rats display early-onset hyperinsulinemia and hyperglycemia, which are hallmarks of type II diabetes. This study was undertaken to determine the expression and the subcellular distribution of the GLUT1 and GLUT4 glucose transporters in skeletal muscle of obese diabetic SHR rats. D-glucose-protectable cytochalasin-B binding to subcellular membrane fractions of hindlimb muscles was used to determine glucose transporter number. GLUT1 and GLUT4 glucose transporter isotypes were detected using antibodies to the COOH-terminal region of the GLUT1 and GLUT4 proteins. Glucose transporter number was significantly lower (-40%) in crude unfractionated membranes of obese diabetic SHR than of lean SHR muscles. When crude membranes were fractionated to separate plasma membranes and the intracellular membranes containing glucose transporters, the number of cytochalasin-B binding sites was found to be markedly lower (-50%) in intracellular membranes and slightly but not significantly reduced (-20%) in plasma membranes of muscle from obese diabetic SHR compared with lean SHR rats. Western blot analysis revealed that a lower GLUT4 protein abundance (-40%) accounts for the reduced glucose transporter number in intracellular membranes of obese diabetic SHR compared with lean SHR muscles. GLUT4 protein content was also reduced by 50% in plasma membranes from obese SHR muscles relative to lean rat muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential regulation of GLUT1 and GLUT4 glucose transporters in skeletal muscle of a new model of type II diabetes. The obese SHR/N-cp rat. 832 52

This study compared the effects of aerobic exercise training and chronic administration of the selective beta 2-adrenergic agonist clenbuterol on whole body and skeletal muscle insulin resistance in obese (fa/fa) Zucker rats. Obese rats were randomly assigned to training, clenbuterol, or sedentary control groups. Lean littermates served as a second control group. After 4-5 wk of treatment, an oral glucose tolerance test was performed, followed 1 wk later by hindlimb perfusion, during which time the rates of glucose uptake and 3-O-methyl-D-glucose (3-MG) transport were assessed in the presence of a submaximal (500 microU/ml) insulin concentration. Training resulted in a significant increase in citrate synthase and cytochrome oxidase activity in the recruited muscles. Clenbuterol induced a large increase in muscle mass but provoked a significant decrease in oxidative enzyme activity and beta-adrenergic receptor density. Both treatments increased glucose tolerance and reduced the postglucose insulin response, with the improvements being more pronounced in the clenbuterol group. However, only exercise training improved insulin-stimulated hindlimb muscle glucose uptake (11.37 +/- 0.65, 8.73 +/- 0.77, and 8.27 +/- 0.41 mumol.g-1.h-1 for trained, clenbuterol, and sedentary control groups, respectively) and 3-MG transport. These results suggest that aerobic exercise training attenuated the insulin-resistant condition in the obese Zucker rat by a mechanism other than or in addition to beta 2-adrenergic receptor activation.
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PMID:Exercise training and clenbuterol reduce insulin resistance of obese Zucker rats. 838 91

GLUT2 underexpression has been reported in the beta-cells of Zucker diabetic fatty rats and db/db mice, models of spontaneously occurring NIDDM with antecedent obesity. To determine whether the beta-cells of a nonobese rodent model of NIDDM exhibit the same abnormalities in GLUT2, we studied Goto-Kakizaki rats. In these mildly diabetic animals glucose-stimulated insulin secretion was reduced at all ages examined from 8 to 48 wk. In normal control Wistar rats, immunostainable GLUT2 was present on all insulin-positive cells in the pancreatic islets. Only 85% of beta-cells were GLUT2-positive in GK rats at 12 wk of age, and only 34% were positive at 48 wk of age. GLUT2 mRNA was 50% of normal in 12-wk-old GK rats. In the latter age-group, glucose-stimulated insulin secretion was only 28% of normal at a time when 85% of beta-cells were GLUT2-positive and initial 3-O-methyl-D-glucose transport rate was 77% of the control value. We conclude that although GLUT2 is underexpressed, neither the magnitude of the underexpression of GLUT2 nor of the reduction in GLUT2 transport function in islets of GK rats is sufficient by itself to explain the profound reduction in glucose-stimulated insulin secretion.
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PMID:GLUT2 expression and function in beta-cells of GK rats with NIDDM. Dissociation between reductions in glucose transport and glucose-stimulated insulin secretion. 851 73

Defects of glucose transport and phosphorylation may underlie insulin resistance in obesity and non-insulin-dependent diabetes mellitus (NIDDM). To test this hypothesis, dynamic imaging of 18F-2-deoxy-glucose uptake into midthigh muscle was performed using positron emission tomography during basal and insulin-stimulated conditions (40 mU/m2 per min), in eight lean nondiabetic, eight obese nondiabetic, and eight obese subjects with NIDDM. In additional studies, vastus lateralis muscle was obtained by percutaneous biopsy during basal and insulin-stimulated conditions for assay of hexokinase and citrate synthase, and for immunohistochemical labeling of Glut 4. Quantitative confocal laser scanning microscopy was used to ascertain Glut 4 at the sarcolemma as an index of insulin-regulated translocation. In lean individuals, insulin stimulated a 10-fold increase of 2-deoxy-2[18F]fluoro-D-glucose (FDG) clearance into muscle and significant increases in the rate constants for inward transport and phosphorylation of FDG. In obese individuals, the rate constant for inward transport of glucose was not increased by insulin infusion and did not differ from values in NIDDM. Insulin stimulation of the rate constant for glucose phosphorylation was similar in obese and lean subjects but reduced in NIDDM. Insulin increased by nearly twofold the number and area of sites labeling for Glut 4 at the sarcolemma in lean volunteers, but in obese and NIDDM subjects translocation of Glut 4 was attenuated. Activities of skeletal muscle HK I and II were similar in lean, obese and NIDDM subjects. These in vivo and ex vivo assessments indicate that impaired glucose transport plays a key role in insulin resistance of NIDDM and obesity and that an additional impairment of glucose phosphorylation is evident in the insulin resistance of NIDDM.
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PMID:The effect of non-insulin-dependent diabetes mellitus and obesity on glucose transport and phosphorylation in skeletal muscle. 867 80

Why is it important to understand the mechanisms controlling intestinal adaptation? There are two major answers to this question. Firstly, in establishing the cellular and molecular events associated with intestinal adaptation, we will formulate a general framework that may be applied to the understanding of adaptation of other cell membranes. For example, alterations in the synthesis of glucose carriers and their subsequent insertion into membranes may alter sugar entry across the intestinal brush border membrane (BBM) using the sodium-dependent D-glucose transporter, SGLT1, or the BBM sodium-independent facultative fructose transporter, GLUT5, and may alter facilitated sugar exit across the basolateral membrane (BLM) using GLUT2. The precise role of transcriptional and translational processes in the up- or down-regulation of sugar transport requires further definition. Alterations in enterocyte microsomal lipid metabolic enzyme expression occurring during the course of intestinal adaptation will direct the synthesis of lipids destined for trafficking to the BBM and BLM domains of the enterocyte. This will subsequently alter the passive permeability properties of these membranes and ultimately influence lipid absorption. Therefore, establishing the physiological, cellular and molecular mechanisms of adaptation in the intestine will define principles that may be applied to other epithelia. Secondly, enterocyte membrane adaptation is subject to dietary modification, and these may be exploited as a means to enhance a beneficial or to reduce a detrimental aspect of the intestinal adaptive process in disease states. Alterations in membrane function occur in association with changes in dietary lipids, and these are observed in a variety of cells and tissues including lymphocytes, testes, liver, adipocytes, nerve tissue, nuclear envelope and mitochondria. Therefore, the elucidation of the mechanisms of intestinal adaptation and the manner whereby dietary manipulation modulates these processes affords the future possibility of dietary engineering aimed at using food as a therapeutic agent. It is hoped this approach will form the centerpiece for future investigation that would focus on disease prevention, as well as on the development of better therapeutic strategies to prevent the development or to treat the complications of conditions such as diabetes mellitus, obesity, hyperlipidemia and inflammatory bowel diseases. This review deals with the physiology of glucose transport with specific emphasis on transporters of the brush border membrane (BBM) and the basolateral membrane (BLM). On the BBM the sodium (Na)/glucose transporters (SGLT1 and SGLT2), the Na-independent transporter (GLUT5), and on the BLM the hexose transporter (GLUT2) are discussed. The molecular biology of these transporters is also reviewed.
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PMID:Adaptation of intestinal nutrient transport in health and disease. Part I. 907 26

Impairments in intestinal absorptive and digestive processes have been described in several pathophysiological situations, such as in drug-induced diabetes, obesity and hypercholesterolaemia. Furthermore, there is evidence for the occurrence of beta 3-adrenoceptors in multiple regions of the gastrointestinal tract, but there are no data concerning their possible involvement on jejunal and ileal digestive and absorptive functions. In this work, we have measured the modifications of selective intestinal absorption and disaccharidase activities in alloxan-induced diabetic and in diet-induced obese and hypercholesterolaemic Wistar rats. The action of a beta 3-adrenergic agonist (Trecadrine) with hypoglycaemic and lipolytic properties on those gastrointestinal functions has been studied. Increases in the galactose uptake by intestinal rings and in both sucrase and maltase activities were found in diabetic rats. The results obtained after Trecadrine administration to diabetic rats led to an improvement of the altered values. On the other hand, our data show a decrease in sugar absorption and in disaccharidase activities in both obese and hypercholesterolaemic groups, probably related to the low carbohydrate and high fat content of these diets. An amelioration in sucrase activity was observed after treatment with Trecadrine. Finally, Trecadrine administration to control animals significantly inhibited galactose intestinal absorption, which was independently confirmed by additional in-vitro studies. Overall, these results could be attributed not only to an improvement in the pathophysiological condition (diabetes, obesity and hypercholesterolaemia), but also to a direct effect of the beta 3-adrenergic agonist on the intestinal absorption processes.
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PMID:Effects of trecadrine, a beta 3-adrenergic agonist, on intestinal absorption of D-galactose and disaccharidase activities in three physiopathological models. 930 54

The purpose of this experiment was to determine if Osborne-Mendel (OM) rats, which are susceptible to dietary-induced obesity, and S5B/PL (S5B) rats, which are resistant to dietary-induced obesity, differ in their feeding responses to mercaptoacetate (MA), which blocks fatty acid oxidation, or 2-deoxy-D-glucose (2DG), which blocks glucose utilization. 2DG (100 mg/kg or 200 mg/kg) increased food intake in both strains of rats on a high-fat diet (56% energy from fat). Mercaptoacetate (600 mumol/kg) increased food intake in OM but not S5B rats on a high-fat diet. When maintained on a low-fat diet (10% energy from fat), MA (400 mumol/kg or 600 mumol/kg) stimulated food intake in OM rats, whereas S5B rats increased food intake only after the highest dose of MA (600 mumol/kg). MA stimulated carbohydrate and protein intake in OM rats maintained on a macronutrient selection diet, whereas S5B rats maintained on this diet did not significantly increase intake of any macronutrient after MA. These results demonstrate that OM and S5B rats have a similar food intake response to 2DG but a dissimilar response to MA. The variable response to MA in these strains may be due to a difference in peripheral or central signaling systems related to fatty acid oxidation or a difference in metabolic environments between the strains, which in turn affects the feeding response to MA. These studies suggest that a difference in control of fatty acid oxidation may account for the difference in susceptibility to obesity when eating a high-fat diet.
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PMID:Feeding response to mercaptoacetate in Osborne-Mendel and S5B/PL rats. 944 44

1. Metabolic disorders, such as obesity and non-insulin-dependent diabetes mellitus, and cardiovascular disorders, such as essential hypertension, congestive cardiac failure and atherosclerosis, have two features in common, namely relative resistance to insulin-mediated glucose uptake and vascular endothelial dysfunction. 2. Significant increases in limb blood flow occur in response to systemic hyperinsulinaemia, although there is marked variation in the results due to a number of confounding factors, including activation of the sympathetic nervous system. Local hyperinsulinaemia has a less marked vasodilator action despite similar plasma concentrations, but this can be augmented by co-infusing D-glucose. 3. Insulin may stimulate endothelial nitric oxide production or may act directly on vascular smooth muscle via stimulation of the Na+-H+ exchanger and Na+/K+-ATPase, leading to hyperpolarization of the cell membrane and consequent closure of voltage-gated Ca2+ channels. 4. There is evidence both for and against the existence of a functional relationship between insulin-mediated glucose uptake (insulin sensitivity) and insulin-mediated vasodilation (which can be regarded as a surrogate measure for endothelial function). 5. If substrate delivery is the rate-limiting step for insulin-mediated glucose uptake (in other words, if skeletal muscle blood flow is a determinant of glucose uptake), then endothelial dysfunction, resulting in a relative inability of mediators, including insulin, to stimulate muscle blood flow, may be the underlying mechanism accounting for the association of atherosclerosis and other cardiovascular disorders with insulin resistance. 6. Glucose uptake may determine peripheral blood flow via stimulation of ATP-dependent ion pumps with consequent vasorelaxation. 7. A 'third factor' may cause both insulin resistance and endothelial dysfunction in cardiovascular disease. Candidates include skeletal muscle fibre type and capillary density, distribution of adiposity and endogenous corticosteroid production. 8. A complex interaction between endothelial dysfunction, abnormal skeletal muscle blood flow and reduced insulin-mediated glucose uptake may be central to the link between insulin resistance, blood pressure, impaired glucose tolerance and the risk of cardiovascular disease. An understanding of the primary mechanisms resulting in these phenotypes may reveal new therapeutic targets in metabolic and cardiovascular disease.
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PMID:Insulin as a vascular hormone: implications for the pathophysiology of cardiovascular disease. 959 May 66


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