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

The role of adipocyte-secreted resistin/adipocyte-specific secretory factor (ADSF)/FIZZ3 in obesity and diabetes has been controversial at best. Recently generated resn knockout mice showed normal glucose and insulin sensitivity with lower fasting glucose levels. Upon feeding with a high-fat diet, the knockout mice exhibited increased glucose tolerance with decreased hepatic glucose output, possibly due to phosphorylation and activation of AMP-activated protein kinase and suppression of gluconeogenic genes. In comparison, transgenic mice overexpressing a dominant negative form of resistin/ADSF/FIZZ3 showed increased adiposity with elevated leptin and adiponectin levels, accompanying enhanced glucose tolerance and insulin sensitivity both on chow and high-fat diets. Although its underlying mechanisms need further elucidation, the in vivo studies demonstrate a role of resistin/ADSF/FIZZ3 in obesity and insulin resistance.
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PMID:Resistin/ADSF/FIZZ3 in obesity and diabetes. 1535 76

Glucose-dependent insulinotropic polypeptide (GIP) regulates glucose homeostasis and high-fat diet-induced obesity and insulin resistance. Therefore, elucidating the mechanisms that regulate GIP release is important. GIP is produced by K cells, a specific subtype of small intestinal enteroendocrine (EE) cell. Bombesin-like peptides produced by enteric neurons and luminal nutrients stimulate GIP release in vivo. We previously showed that PMA, bombesin, meat hydrolysate, glyceraldehyde, and methylpyruvate increase hormone release from a GIP-producing EE cell line (GIP/Ins cells). Here we demonstrate that bombesin and nutrients additively stimulate hormone release from GIP/Ins cells. In various cell systems, bombesin and PMA regulate cell physiology by activating PKD signaling in a PKC-dependent fashion, whereas nutrients regulate cell physiology by inhibiting AMPK signaling. Western blot analyses of GIP/Ins cells using antibodies specific for activated and/or phosphorylated forms of PKD and AMPK and one substrate for each kinase revealed that bombesin and PMA, but not nutrients, activated PKC, but not PKD. Conversely, nutrients, but not bombesin or PMA, inhibited AMPK activity. Pharmacological studies showed that PKC inhibition blocked bombesin- and PMA-stimulated hormone release, but AMPK activation failed to suppress nutrient-stimulated hormone secretion. Forced expression of constitutively active vs. dominant negative PKDs or AMPKs failed to perturb bombesin- or nutrient-stimulated hormone release. Thus, in GIP/Ins cells, PKC regulates bombesin-stimulated hormone release, whereas nutrients may control hormone release by regulating the activity of AMPK-related kinases, rather than AMPK itself. These results strongly suggest that K cells in vivo independently respond to neuronal vs. nutritional stimuli via two distinct signaling pathways.
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PMID:Bombesin and nutrients independently and additively regulate hormone release from GIP/Ins cells. 1538 72

Patients with diabetes and other obesity-linked conditions have increased susceptibility to cardiovascular disorders. The adipocytokine adiponectin is decreased in patients with obesity-linked diseases. Here, we found that pressure overload in adiponectin-deficient mice resulted in enhanced concentric cardiac hypertrophy and increased mortality that was associated with increased extracellular signal-regulated kinase (ERK) and diminished AMP-activated protein kinase (AMPK) signaling in the myocardium. Adenovirus-mediated supplemention of adiponectin attenuated cardiac hypertrophy in response to pressure overload in adiponectin-deficient, wild-type and diabetic db/db mice. In cultures of cardiac myocytes, adiponectin activated AMPK and inhibited agonist-stimulated hypertrophy and ERK activation. Transduction with a dominant-negative form of AMPK reversed these effects, suggesting that adiponectin inhibits hypertrophic signaling in the myocardium through activation of AMPK signaling. Adiponectin may have utility for the treatment of hypertrophic cardiomyopathy associated with diabetes and other obesity-related diseases.
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PMID:Adiponectin-mediated modulation of hypertrophic signals in the heart. 1555 58

Metformin reduces the incidence of progression to type 2 diabetes in humans with obesity or impaired glucose tolerance. We used an animal model to investigate whether metformin could prevent acute lipid-induced insulin resistance and the mechanisms involved. Metformin or vehicle was administered to rats daily for 1 week. Rats were studied basally, after 3.75 h of intralipid-heparin or glycerol infusion, or after 5 h of infusion with a hyperinsulinemic-euglycemic clamp between 3 and 5 h. Metformin had no effect on plasma triacylglycerol or nonesterified fatty acid concentrations and did not alter glucose turnover or gluconeogenic enzyme mRNA after lipid infusion. However, metformin normalized hepatic glucose output and increased liver glycogen during lipid infusion and clamp. Basal liver (but not muscle or fat) AMP-activated protein kinase activity was increased by metformin (by 310%; P < 0.01), associated with increased phosphorylation of acetyl CoA carboxylase. Postclamp liver but not muscle phosphorylated/total Akt protein was increased, whereas basal c-Jun NH2-terminal kinase-1 and -2 protein expression were reduced (by 39 and 53%, respectively; P < 0.05). Metformin also increased hepatic basal IkappaBalpha levels (by 260%; P < 0.001) but had no effect on tyrosine phosphorylation or expression of insulin receptor substrate-1 (IRS-1). In summary, metformin opposes the development of acute lipid-induced insulin resistance in the liver through alterations in multiple signaling pathways.
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PMID:Metformin prevents the development of acute lipid-induced insulin resistance in the rat through altered hepatic signaling mechanisms. 1556 58

Obesity shortens life expectancy and is a risk factor for hypertension and Type 2 diabetes. When added to the standard chow of Sprague-Dawley or Otsuka Long-Evans Tokushima Fatty rats, alpha-lipoic acid (0.5% weight/weight) reduced body weight and food intake. Alpha-lipoic acid also increased whole-body energy expenditure. It exerts its effects by suppressing hypothalamic AMP-activated protein kinase. Long-term studies to determine whether these anti-obesity effects are maintained in animals are required before alpha-lipoic acid is considered for clinical trial in human obesity.
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PMID:Alpha-lipoic acid, an anti-obesity agent? 1556 20

As indicated by in vitro studies, both lipogenesis and lipolysis in adipocytes depend on the cellular ATP levels. Ectopic expression of mitochondrial uncoupling protein 1 (UCP1) in the white adipose tissue of the aP2-Ucp1 transgenic mice reduced obesity induced by genetic or dietary manipulations. Furthermore, respiratory uncoupling lowered the cellular energy charge in adipocytes, while the synthesis of fatty acids (FA) was inhibited and their oxidation increased. Importantly, the complex metabolic changes triggered by ectopic UCP1 were associated with the activation of AMP-activated protein kinase (AMPK), a metabolic master switch, in adipocytes. Effects of several typical treatments that reduce adiposity, such as administration of leptin, beta-adrenoceptor agonists, bezafibrate, dietary n-3 polyunsaturated FA or fasting, can be compared with a phenotype of the aP2-Ucp1 mice. These situations generally lead to the upregulation of mitochondrial UCPs and suppression of the cellular energy charge and FA synthesis in adipocytes. On the other hand, FA oxidation is increased. Moreover, it has been shown that AMPK in adipocytes can be activated by adipocyte-derived hormones leptin and adiponectin, and also by insulin-sensitizes thiazolidinediones. Thus, it is evident that metabolism of adipose tissue itself is important for the control of body fat content and that the cellular energy charge and AMPK are involved in the control of lipid metabolism in adipocytes. The reciprocal link between synthesis and oxidation of FA in adipocytes represents a prospective target for the new treatment strategies aimed at reducing obesity.
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PMID:Role of energy charge and AMP-activated protein kinase in adipocytes in the control of body fat stores. 1559 85

Skeletal muscle is a major mass peripheral tissue that accounts for approximately 40% of total body weight and 50% of energy expenditure and is a primary site of glucose disposal and fatty acid oxidation. Consequently, muscle has a significant role in insulin sensitivity, obesity, and the blood-lipid profile. Excessive caloric intake is sensed by the brain and induces beta-adrenergic receptor (beta-AR)-mediated adaptive thermogenesis. Beta-AR null mice develop severe obesity on a high fat diet. However, the target gene(s), target tissues(s), and molecular mechanism involved remain obscure. We observed that 30-60 min of beta-AR agonist (isoprenaline) treatment of C2C12 skeletal muscle cells strikingly activated (>100-fold) the expression of the mRNA encoding the nuclear hormone receptor, Nur77. In contrast, the expression of other nuclear receptors that regulate lipid and carbohydrate metabolism was not induced. Stable transfection of Nur77-specific small interfering RNAs (siNur77) into skeletal muscle cells repressed endogenous Nur77 mRNA expression. Moreover, we observed attenuation of gene and protein expression associated with the regulation of energy expenditure and lipid homeostasis, for example AMP-activated protein kinase gamma3, UCP3, CD36, adiponectin receptor 2, GLUT4, and caveolin-3. Attenuation of Nur77 expression resulted in decreased lipolysis. Finally, in concordance with the cell culture model, injection and electrotransfer of siNur77 into mouse tibialis cranialis muscle resulted in the repression of UCP3 mRNA expression. This study demonstrates regulatory cross-talk between the nuclear hormone receptor and beta-AR signaling pathways. Moreover, it suggests Nur77 modulates the expression of genes that are key regulators of skeletal muscle lipid and energy homeostasis. In conclusion, we speculate that Nur77 agonists would stimulate lipolysis and increase energy expenditure in skeletal muscle and suggest selective activators of Nur77 may have therapeutic utility in the treatment of obesity.
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PMID:Nur77 regulates lipolysis in skeletal muscle cells. Evidence for cross-talk between the beta-adrenergic and an orphan nuclear hormone receptor pathway. 1564 Jan 43

The occurrence of Type II (non-insulin-dependent) diabetes and obesity and their associated morbidities continue to increase and they are rapidly reaching epidemic proportions. AMPK (AMP-activated protein kinase) was initially thought of as an intracellular 'fuel gauge' responding to a decrease in the level of ATP by increasing energy production and decreasing energy utilization. Recent studies have shown that AMPK plays a role in controlling the whole body energy homoeostasis, including the regulation of plasma glucose levels, fatty acid oxidation and glycogen metabolism. In addition to its effects on the periphery, AMPK has been found to play a key role in the control of food intake through its regulation by hormones, including leptin, within the hypothalamus. The control of AMPK activity, therefore, provides an attractive target for therapeutic intervention in metabolic disorders such as obesity and Type II diabetes. Indeed, a number of physiological and pharmacological factors that are beneficial in these disorders have been shown to act, at least in part, through the activation of AMPK.
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PMID:AMP-activated protein kinase and the metabolic syndrome. 1578 7

Obesity, a state of apparent "leptin resistance" is well known to be associated with insulin resistance. In diet-induced obesity (DIO), hepatic insulin signaling is impaired but the link between leptin and insulin signaling pathways is only incompletely defined. The aim of the present study was to evaluate the effects of DIO on leptin and insulin cross-signaling in the liver. Leptin receptor expression was measured by in situ hybridization with pan-leptin receptor probes and by immunoblotting. Furthermore, intracellular signaling was investigated in vivo under basal conditions and at 45 and 360 min after stimulation with a bolus of human recombinant leptin (hrec-leptin; 1 mg/kg body wt) or saline. At baseline, all forms of the leptin receptor were markedly to completely down-regulated in DIO rats. Hrec-leptin bolus injection stimulated leptin-dependent signaling with a fivefold increase in JAK-2pY in lean but not in DIO rats. Basal IRpY, IRS-1pY, IRS-1p85, IRS-2pY, IRSp85, and PKBpT308 levels were reduced (P<0.01) in DIO rats as compared with lean controls. Basal GSK-3beta serine phosphorylation (S9) was higher (P<0.01) in lean animals along with lower basal PEPCK activity compared with DIO rats consistent with the insulin and leptin resistance of the latter. Only in lean animals phosphorylation of PKB (T308) and GSK-3beta (S9) was acutely stimulated by leptin at 45 min followed by inhibition at 6 h after application. AMPKalpha protein levels as well as basal and leptin-stimulated total and alpha-specific AMPK activity were comparable in both groups. These data show that in a model of dietary-induced obesity 1) leptin receptors and subsequent signaling events are down-regulated, 2) basal insulin signaling is impaired, and 3) the cross-talk between leptin and insulin signaling is differentially regulated by the nutritional status, which is sensed by AMPK in rat liver. Thus, the liver seems to play a major role in the modulation of the leptin signal and insulin resistance in obesity.
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PMID:Hepatic leptin signaling in obesity. 1578 47

Lifestyle interventions including exercise programs are cornerstones in the prevention of obesity-related diabetes. The AMP-activated protein kinase (AMPK) has been proposed to be responsible for many of the beneficial effects of exercise on glucose and lipid metabolism. The effects of long-term exercise training or 5-aminoimidazole-4-carboxamide-1-beta-d-riboruranoside (AICAR) treatment, both known AMPK activators, on the development of diabetes in male Zucker diabetic fatty (ZDF) rats were examined. Five-week-old, pre-diabetic ZDF rats underwent daily treadmill running or AICAR treatment over an 8-week period and were compared with an untreated group. In contrast to the untreated, both the exercised and AICAR-treated rats did not develop hyperglycemia during the intervention period. Whole-body insulin sensitivity, as assessed by a hyperinsulinemic-euglycemic clamp at the end of the intervention period, was markedly increased in the exercised and AICAR-treated animals compared with the untreated ZDF rats (P < 0.01). In addition, pancreatic beta-cell morphology was almost normal in the exercised and AICAR-treated animals, indicating that chronic AMPK activation in vivo might preserve beta-cell function. Our results suggest that activation of AMPK may represent a therapeutic approach to improve insulin action and prevent a decrease in beta-cell function associated with type 2 diabetes.
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PMID:Long-term AICAR administration and exercise prevents diabetes in ZDF rats. 1579 29


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