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

Previous clinical studies reported elevated semicarbazide-sensitive amine oxidase (SSAO) activity in insulin-dependent diabetes mellitus (IDDM), but there are not sufficient data about SSAO in non-insulin-dependent diabetes mellitus (NIDDM). The present study was conducted to investigate serum SSAO activity in NIDDM patients compared with nondiabetic and IDDM patients. Serum SSAO activity in 61 patients with diabetes (n = 34 NIDDM and n = 27 IDDM) and 36 controls was determined using 14C-benzylamine as a substrate. NIDDM and IDDM patients exhibited higher SSAO activity compared with controls ([mean +/- SD] NIDDM, 164.60+/-69.43 pmol/mg protein/h, P<.0001; IDDM, 143.91+/-72.45 pmol/mg protein/h, P<.002; control, 91.46+/-28.11 pmol/mg protein/h). There was a significant positive correlation between serum SSAO activity and the body mass index (BMI), body weight, hemoglobin A1c (HbA1c), fasting plasma glucose, and triglycerides. Within the control group, SSAO correlated with total cholesterol levels. The progression and severity of diabetic complications such as angiopathy may be exacerbated by cytotoxic metabolites (e.g., formaldehyde and hydrogen peroxide) formed by SSAO. These results reveal the possibility that elevated serum SSAO activity in association with obesity and hyperlipidemia may be a cardiovascular risk factor in diabetes mellitus.
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PMID:Elevated serum semicarbazide-sensitive amine oxidase activity in non-insulin-dependent diabetes mellitus: correlation with body mass index and serum triglyceride. 992 Jan 54

Obesity is a complex syndrome that involves defective signaling by a number of different factors that regulate appetite and energy homeostasis. Treatment with exogenous leptin reverses hyperphagia and obesity in ob/ob mice, which have a mutation that causes leptin deficiency, proving the importance of this factor and its receptors in the obesity syndrome. Cells with leptin receptors have been identified outside of the appetite regulatory centers in the brain. Thus leptin has peripheral targets. Because macrophages express signaling-competent leptin receptors, these cells may be altered during chronic leptin deficiency. Consistent with this concept, the present study identifies several phenotypic abnormalities in macrophages from ob/ob mice, including decreased steady-state levels of uncoupling protein-2 mRNA, increased mitochondrial production of superoxide and hydrogen peroxide, constitutive activation of CCAAT enhancer binding protein (C/EBP)-beta, an oxidant-sensitive transcription factor, increased expression of interleukin-6 and cyclooxygenase (COX)-2, two C/EBP-beta target genes, and increased COX-2-dependent production of PGE2. Given the importance of macrophages in the general regulation of inflammation and immunity, these alterations in macrophage function may contribute to obesity-related pathophysiology.
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PMID:Phenotypic abnormalities in macrophages from leptin-deficient, obese mice. 995 Jul 66

Obesity is associated with hyperinsulinemia and elevated concentrations of tumor necrosis factor-alpha (TNF-alpha) in adipose tissue. TNF-alpha has been implicated as an inducer of the synthesis of plasminogen activator inhibitor-1 (PAI-1), the primary physiological inhibitor of fibrinolysis, mediated by plasminogen activators in cultured adipocytes. To identify mechanism(s) through which TNF-alpha induces PAI-1, 3T3-L1 preadipocytes were differentiated into adipocytes and exposed to TNF-alpha for 24 h. TNF-alpha selectively increased the synthesis of PAI-1 without increasing activity of plasminogen activators. Both superoxide (generated by xanthine oxidase plus hypoxanthine) and hydrogen peroxide were potent inducers of PAI-1, and hydroxyl radical scavengers completely abolished the TNF-alpha induction of PAI-1. Exposure of adipocytes to TNF-alpha or insulin alone over 5 days increased PAI-1 production. These agonists exert synergistic effects. Results obtained suggest that TNF-alpha stimulates PAI-1 production by adipocytes, an effect potentiated by insulin, and that adipocyte generation of reactive oxygen centered radicals mediates the induction of PAI-1 production by TNF-alpha. Because induction of PAI-1 by TNF-alpha is potentiated synergistically by insulin, both agonists appear likely to contribute to the impairment of fibrinolytic system capacity typical in obese, hyperinsulinemic patients.
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PMID:TNF-alpha and insulin, alone and synergistically, induce plasminogen activator inhibitor-1 expression in adipocytes. 1036 2

Uncoupling protein 1 (UCP1) dissipates energy and generates heat by catalyzing back-flux of protons into the mitochondrial matrix, probably by a fatty acid cycling mechanism. If the newly discovered UCP2 and UCP3 function similarly, they will enhance peripheral energy expenditure and are potential molecular targets for the treatment of obesity. We expressed UCP2 and UCP3 in Escherichia coli and reconstituted the detergent-extracted proteins into liposomes. Ion flux studies show that purified UCP2 and UCP3 behave identically to UCP1. They catalyze electrophoretic flux of protons and alkylsulfonates, and proton flux exhibits an obligatory requirement for fatty acids. Proton flux is inhibited by purine nucleotides but with much lower affinity than observed with UCP1. These findings are consistent with the hypothesis that UCP2 and UCP3 behave as uncoupling proteins in the cell.
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PMID:Transport function and regulation of mitochondrial uncoupling proteins 2 and 3. 1047 45

In mitochondria ATP synthesis is not perfectly coupled to oxygen consumption due to proton leak across the mitochondrial inner membrane. Quantitative studies have shown that proton leak contributes to approximately 25% of the resting oxygen consumption of mammals. Proton leak plays a role in accounting for differences in basal metabolic rate. Thyroid studies, body mass studies, phylogenic studies and obesity studies have all shown that increased mass-specific metabolic rate is linked to increased mitochondrial proton leak. The mechanism of the proton leak is unclear. Evidence suggests that proton leak occurs by a non-specific diffusion process across the mitochondrial inner membrane. However, the high degree of sequence homology of the recently cloned uncoupling proteins UCP 2 and UCP 3 to brown adipose tissue UCP 1, and their extensive tissue distribution, suggest that these novel uncoupling proteins play a role in proton leak. Early indications from reconstitution experiments and several in vitro expression studies suggest that the novel uncoupling proteins uncouple mitochondria. Furthermore, mice overexpressing UCP 3 certainly show a phenotype consistent with increased metabolism. The evidence for a role for these novel UCPs in mitochondrial proton leak is reviewed.
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PMID:Mitochondrial proton leak: a role for uncoupling proteins 2 and 3? 1123 89

Semicarbazide-sensitive amine oxidases (SSAO) are widely distributed enzymes scavenging biogenic or exogenous amines and generating hydrogen peroxide. We asked whether human adipose tissue could express SSAO. Since hydrogen peroxide exhibits pharmacological insulin-like effects, we also tested whether its endogenous production by SSAO could mimic several insulin effects on adipocytes, such as stimulation of glucose uptake and inhibition of lipolysis. The benzylamine oxidation by human adipose tissue was inhibited by semicarbazide or hydralazine and resistant to pargyline or selegiline. It was due to an SSAO activity localized in adipocyte membranes. A protein of 100-kDa and a 4-kb mRNA corresponding to SSAO were identified in either mammary or abdominal subcutaneous fat depots. In isolated adipocytes, SSAO oxidized similarly benzylamine and methylamine that dose dependently stimulated glucose transport in a semicarbazide-sensitive manner. Antioxidants also inhibited the benzylamine and methylamine effects. Moreover, the ability of diverse substrates to be oxidized by adipocytes was correlated to their effect on glucose transport. Benzylamine and methylamine exerted antilipolytic effects with a maximum attained at 1 mM. These results show that human adipocytes express a membrane-bound SSAO that not only readily oxidizes exogenous amines and generates H(2)O(2), but that also interplays with glucose and lipid metabolism by exerting insulin-like actions. Based on these results and the fact that variations in plasma levels of the soluble form of SSAO have been previously reported in diabetes, we propose that determination of adipocyte SSAO, feasible on subcutaneous microbiopsies, could bring relevant information in pathologies such as obesity or diabetes.
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PMID:Semicarbazide-sensitive amine oxidase substrates stimulate glucose transport and inhibit lipolysis in human adipocytes. 1130 44

Renal sodium retention, as a result of increased abundance of sodium transporters, may play a role in the development and/or maintenance of the increased blood pressure in obesity. To address this hypothesis, we evaluated the relative abundances of renal sodium transporters in lean and obese Zucker rats at 2 and 4 mo of age by semiquantitative immunoblotting. Mean systolic blood pressure was higher in obese rats relative to lean at 3 mo, P < 0.02. Furthermore, circulating insulin levels were 6- or 13-fold higher in obese rats compared with lean at 2 or 4 mo of age, respectively. The abundances of the alpha(1)-subunit of Na-K-ATPase, the thiazide-sensitive Na-Cl cotransporter (NCC or TSC), and the beta-subunit of the epithelial sodium channel (ENaC) were all significantly increased in the obese rats' kidneys. There were no differences for the sodium hydrogen exchanger (NHE3), the bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2 or BSC1), the type II sodium-phosphate cotransporter (NaPi-2), or the alpha-subunit of ENaC. These selective increases could possibly increase sodium retention by the kidney and therefore could play a role in obesity-related hypertension.
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PMID:Increased renal Na-K-ATPase, NCC, and beta-ENaC abundance in obese Zucker rats. 1155 10

Oxidative stress in blood vessels and the kidney in hypertension can be induced by diverse vasoconstrictor mechanisms, including blockade of nitric oxide synthase and activation of angiotensin II type I receptors and thromboxane receptors. It can cause vasoconstriction via bioinactivation of nitric oxide, and by nitric oxide synthase independent mechanisms that include increased generation of endothelin-1 and the effects of superoxide anion and hydrogen peroxide on vascular smooth muscle cells. Oxidative stress can accompany hypertension in many models including the spontaneously hypertensive rat, the angiotensin II-infused rat, renovascular hypertension, the deoxycorticosterone acetate-salt model, and obesity-related hypertension. In the kidney, NADPH oxidase-generating superoxide anion is expressed in the vasculature, interstitium, juxtaglomerular apparatus, and the distal nephron. Much progress has been made in defining the pathways that intervene between agonist stimulation of blood vessels and reactive oxygen species-mediated contractile and renal functional responses in animal models in hypertension.
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PMID:Reactive oxygen species: roles in blood pressure and kidney function. 1188 72

Nuclear and isotopic techniques are valuable tools in human nutritional research studies. Isotopes, both radioactive and nonradioactive, enable detailed evaluations of nutrient intake, body composition, energy expenditure, status of micronutrients, and nutrient bioavailability. In recent times, isotopic methods have been widely used in a number of coordinated research projects and technical cooperation projects of the International Atomic Energy Agency's Nutrition Programme. The doubly labeled water technique combines the use of the stable isotopes oxygen-18 and hydrogen-2 (deuterium) to measure total energy expenditure in free-living human subjects, and to investigate the magnitude and causes of both undernutrition and the emergence of obesity in developing countries. The deuterium dilution technique is a reliable tool to measure breastmilk intake and thereby infant growth and development. In collaboration with the World Health Organization's Growth Monitoring Program, this technique is being used to generate new data on growth standards for children in developing countries. This technique is also used in the measurement of body composition by the estimation of lean body mass and fat mass in individuals. Stable isotopes of iron and zinc have been successfully used to assess the nutritional impact of several nationwide food supplementation-programs conducted on pregnant and lactating women and children in both industrialized and developing countries. Isotopic techniques are especially suitable for monitoring changes in body composition, energy metabolism, and mineral status (with particular reference to osteoporosis) in the elderly. Nuclear methods have also served to develop models for a physiological reference man in Asia in support of radiological health and safety issues, for establishing elemental composition of foods, and for measurement of pollutants in the environment.
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PMID:Nuclear and isotopic techniques for addressing nutritional problems, with special reference to current applications in developing countries. 1197 66

Obese and diabetic patients may benefit from foodstuffs that are poorly absorbed and/or digested at a slower rate. Prowashonupana (PW) is a cultivar of barley, whose grains are enriched in beta-glucans, and thus may be less digestible than standard barley (barley cultivar (BZ) 594.35.e). To test this, both kinds of barley were grown in a chamber into which (13)CO(2) was injected. On two occasions, 10 healthy hydrogen (H(2))-producing adults consumed in random order one 35-g portion of each of the cooked, dehulled (13)C-enriched grains. CO(2) production was measured in a whole-body direct calorimeter, and H(2) and (13)CO(2) were measured in breath at baseline and intermittently for 450 min. The percentage of the (13)C dose recovered in breath was calculated. Results were compared by repeated measures analysis of variance (ANOVA). The percentage of the (13)C dose oxidized was greater after BZ than after PW consumption (P < 0.05). The area under the curve for H(2) was greater after PW (mean +/- SD, 8658 +/- 6582) than after BZ (5178 +/- 4759) intake (P < 0.05), whereas there was no difference in CO(2) production. We conclude that absorption of PW is significantly lower than that of BZ, making the modified barley appropriate for obese and diabetic patients.
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PMID:Carbohydrate digestion in humans from a beta-glucan-enriched barley is reduced. 1222 Dec 14


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