Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

alpha2-HS glycoprotein (AHSG), also known as fetuin-A, inhibits insulin receptor autophosphorylation and tyrosine kinase activity in vitro and in vivo. Earlier we have shown that fetuin-null (KO) mice demonstrate improved insulin sensitivity and resistance to diet-induced obesity. Since aging is associated with insulin resistance and impaired glucose handling, we tested the hypothesis that fetuin-null (KO) mice are resilient to changes in insulin sensitivity associated with aging. Aged (80-week-old) fetuin-null mice were leaner and demonstrated significantly lower body weights compared to age- and sex-matched wild-type (WT) littermates. Leanness in aged fetuin KO mice was accompanied by a significant increase in dark-onset energy expenditure, without marked alteration of respiratory quotient. In comparison to WT mice, fetuin KO mice demonstrated a lower fasting insulin resistance index, and significantly lower blood glucose and insulin levels, following a 4h fast. Interestingly, despite significantly decreased insulin levels during a glucose tolerance test, aged fetuin-null mice demonstrated a similar glucose excursion as WT mice, indicative of improved insulin sensitivity. Analysis of aldehyde-fuchsin stained pancreas from aged fetuin KO mice indicated no difference in islet beta-cell size or number. An insulin tolerance test confirmed the increased insulin sensitivity of aged fetuin KO mice. Further, compared to WT mice, aged fetuin-null mice demonstrated increased skeletal muscle and liver IR autophosphorylation and TK activity. Taken together, this study suggests that the absence of fetuin may contribute to the improvement of insulin sensitivity associated with aging.
 ...
PMID:Fetuin-null mice are protected against obesity and insulin resistance associated with aging. 1701 19

Adipose tissue plays a critical role in energy homeostasis, not only in storing triglycerides, but also responding to nutrient, neural, and hormonal signals and secreting adipokines that control feeding, thermogenesis, immunity, and neuroendocrine function. A rise in leptin signals satiety to the brain through receptors in hypothalamic and brainstem neurons. Leptin activates tyrosine kinase, Janus kinase 2, and signal transducer and activator of transcription 3, leading to increased levels of anorexigenic peptides, e.g., alpha-melanocyte stimulating hormone and cocaine- and amphetamine-regulated transcript, and inhibition of orexigenic peptides, e.g., neuropeptide Y and agouti-related peptide. Obesity is characterized by hyperleptinemia and hypothalamic leptin resistance, partly caused by induction of suppressor of cytokine signaling-3. Leptin falls rapidly during fasting and potently stimulates appetite, reduces thermogenesis, and mediates the inhibition of thyroid and reproductive hormones and activation of the hypothalamic-pituitary-adrenal axis. These actions are integrated by the paraventicular hypothalamic nucleus. Leptin also decreases glucose and stimulates lipolysis through central and peripheral pathways involving AMP-activated protein kinase (AMPK). Adiponectin is secreted exclusively by adipocytes and has been linked to glucose, lipid, and cardiovascular regulation. Obesity, diabetes, and atherosclerosis have been associated with reduced adiponectin levels, whereas adiponectin treatment reverses these abnormalities partly through activation of AMPK in liver and muscle. Administration of adiponectin in the brain recapitulates the peripheral actions to increase fatty acid oxidation and insulin sensitivity and reduce glucose. Although putative adiponectin receptors are widespread in peripheral organs and brain, it is uncertain whether adiponectin acts exclusively through these targets. As with leptin, adiponectin requires the central melanocortin pathway. Furthermore, adiponectin stimulates fatty acid oxidation and reduces glucose and lipids, at least in part, by activating AMPK in muscle and liver.
Obesity (Silver Spring) 2006 Aug
PMID:Adipose tissue as an endocrine organ. 1702 75

Src homology 2 (SH2) B adaptor protein 1 (SH2B1; originally named SH2-B) is a member of a family of adaptor proteins that influences a variety of signaling pathways mediated by Janus kinase (JAK) and receptor tyrosine kinases. Although SH2B1 performs classical adaptor functions, such as recruitment of specific proteins to activated receptors, it also demonstrates a unique ability to enhance the kinase activity of the cytokine receptor-associated tyrosine kinase JAK2, as well as that of several receptor tyrosine kinases. SH2B1 is also among a small number of adaptor proteins shown to undergo nucleocytoplasmic shuttling, although its exact role within the nucleus is not yet clear. Deletion of the SH2B1 gene results in severe obesity and both leptin and insulin resistance, as well as infertility, which might be a consequence of resistance to insulin-like growth factor I. Thus, knockout mice support a role for SH2B1 as a positive regulator of JAK2 signaling pathways initiated by leptin, as well as of pathways initiated by insulin and, potentially, by insulin-like growth factor I.
 ...
PMID:SH2B1 (SH2-B) and JAK2: a multifunctional adaptor protein and kinase made for each other. 1714 Aug 4

Visfatin (also known as pre-B cell colony-enhancing factor or PBEF) is a novel adipocytokine that is highly expressed in visceral fat and upregulated in obesity and type 2 diabetes mellitus. Visfatin binds to and activates the insulin receptor (IR), thereby exerting insulin-mimetic effects in various cell lines. IR has been detected in osteoblasts, which is consistent with the role of insulin as an important osteotropic hormone. This study investigated the actions of visfatin on human primary osteoblasts. The expression and tyrosine phosphorylation of IR, IR substrate-1 (IRS-1), and IRS-2 were determined by immunoprecipitation and immunoblotting. Cell proliferation was determined by measuring [(3)H]thymidine incorporation and cell number. Glucose uptake was determined by measuring 2-[(3)H]deoxyglucose incorporation. Real-time quantitative reverse-transcription polymerase chain reaction (PCR) was used for determining alkaline phosphatase (ALP), osteocalcin, and type I collagen mRNA expression. Enzyme-linked immunosorbent assay and radioimmunoassay were used for measuring ALP activity, osteocalcin secretion, and type I collagen production. We found that visfatin induced tyrosine phosphorylation of IR, IRS-1, and IRS-2. Moreover, the effects of visfatin - glucose uptake, proliferation, and type I collagen enhancement of cultured human osteoblast-like cells - bore a close resemblance to those of insulin and were inhibited by hydroxy-2-naphthalenylmethylphosphonic acid tris-acetoxymethyl ester, a specific inhibitor of IR tyrosine kinase activity. We also unexpectedly found that visfatin downregulated osteocalcin secretion from human osteoblast-like cells. These data indicate that the regulation of glucose uptake, proliferation, and type I collagen production by visfatin in human osteoblasts involves IR phosphorylation, the same signal-transduction pathway used by insulin.
 ...
PMID:Insulin-like effects of visfatin on human osteoblasts. 1734 Feb 25

The insulin resistance syndrome, also referred to as the metabolic syndrome or syndrome X, is associated with a primary cellular defect in insulin action (insulin resistance) and a compensatory increase in insulin secretion. The combination of insulin resistance and subsequent hyperinsulinaemia causes a number of metabolic and cardiovascular changes that result in a syndrome typically characterised by type 2 diabetes, obesity, dyslipidaemia, coronary artery disease and hypertension. Moreover, disturbances in sleep (sleep apnoea) and ovarian dysfunction are also characterised by insulin resistance. The pathophysiological basis for these disturbances reflects the impact of variable genetic and environmental influences. At a molecular level, insulin resistance involves defects of insulin signalling such as reduced insulin receptor tyrosine kinase activity and reduced post-receptor phosphorylation steps that impinge on metabolic and vascular effects of insulin.
 ...
PMID:The insulin resistance syndrome: physiological considerations. 1746 39

Preeclampsia affects 3-5% of pregnancies and can have a significant impact on health for both mother and fetus. Risk factors include maternal co-morbidities such as obesity and chronic hypertension, paternal factors, and genetic factors. New hypertension and proteinuria during the second half of pregnancy are key diagnostic criteria, but the clinical features and associated prognostic implications are somewhat heterogeneous and may reflect different mechanisms of disease. Renal dysfunction and proteinuria correspond to the pathologic finding of glomerular endotheliosis, and generally resolve after cure of preeclampsia through fetal and placenta delivery. The molecular mechanisms behind this disease are being discovered and refined. The initial etiologic agents are currently unknown. Pathologic studies show abnormal development of an ischemic placenta with a high-resistance vasculature, which cannot deliver an adequate blood supply to the fetoplacental unit. Endothelial dysfunction plays a central role in the pathogenesis of the maternal syndrome. Dysfunctional endothelial cells produce altered quantities of vasoactive mediators, which lead to a tip in the balance towards vasoconstriction. An imbalance in circulating angiogenic factors is emerging as a prominent mechanism that mediates the endothelial dysfunction and the clinical signs and symptoms of preeclampsia. Soluble fms-like tyrosine kinase 1 (sFlt1), an endogenous anti-angiogenic factor that is a potent vascular endothelial growth factor (VEGF) antagonist, is highly elevated in preeclampsia. VEGF is not only important in angiogenesis, but also in maintaining endothelial health including the formation of endothelial fenestrae (a hallmark of the glomerular vascular endothelium). sFlt1 overexpression in animals induces glomerular endotheliosis with the loss of endothelial fenestrae that resembles the renal histological lesions of preeclampsia. More severe forms of preeclampsia, including the HELLP syndrome, may be explained by a concomitant elevation in both sFlt1 and soluble endoglin, another anti-angiogenic factor. Unraveling of the molecular mechanisms behind preeclampsia may help to expand our armamentarium to treat patients in a more directed fashion, as current management consists of supportive care and expedited delivery. Finally, long-term outcomes of women with preeclampsia include a significantly increased risk for hypertension and cardiovascular disease, including mortality, which may warrant more aggressive screening and treatment in this population.
 ...
PMID:Pre-eclampsia: clinical manifestations and molecular mechanisms. 1757 Sep 33

Almost every systemic vessel is surrounded by a layer of perivascular adipose tissue (PVAT), which had been mainly considered as a mechanical support for vasculature. However, recent advances have revealed that PVAT is an active player in controlling vessel function. PVAT releases relaxation factor(s) with unknown chemical identity (named perivascular adipocyte-derived relaxation factor, PVRF) that attenuates vasoconstriction to various agonists including phenylephrine, serotonin, angiotensin II, and U 46619 (a thromboxane A(2) mimic), through activation of K(+) channels. PVAT also promotes vasoconstriction to perivascular nerve stimulation by producing vasoconstrictor or facilitator (named perivascular adipocyte-derived constricting factor, PVCF), which includes superoxide and was mediated through activation of tyrosine kinase and MAPK/ERK pathways. Therefore, PVAT has a dual regulatory role in modulating vessel function, attenuating vasoconstriction to agonists by PVRF and promoting constriction to perivascular nerve excitation by PVCF. In vivo, normal amount of PVAT (total body fat as well) is likely to be important in maintaining the homeostasis of vascular tone and blood pressure, since lipoatrophic mice developed hypertension. On the other end, excessive accumulation of body fat (obesity) impaired PVRF production/action, despite an increase in the amount of PVAT. In spontaneously hypertensive rats, an animal model of hypertension without obesity, the ability of PVAT to attenuate vasoconstriction to agonists was reduced, and treatment with atorvastatin improved PVAT function. PVAT, vasodilating and constricting factors of PVAT origin, and signalling pathways of these factors may represent new targets for developing new strategies to treat vascular disorders associated with abnormal adiposity.
 ...
PMID:Dual modulation of vascular function by perivascular adipose tissue and its potential correlation with adiposity/lipoatrophy-related vascular dysfunction. 1762 51

Obesity is a major risk factor for the development of hypertension. Recent studies have suggested that leptin, a 167-amino acid peptide hormone produced by white adipose tissue, is related to the pathogenesis of obesity-related hypertension. However, the signaling mechanisms underlying the effects of leptin remain to be extensively examined. In this study, we found that leptin induced extracellular signal-regulated kinase phosphorylation and endothelin-1 expression in rat aortic smooth muscle cells. Both PD98059 and U0126, inhibitors of the upstream activator of mitogen-activated protein kinase kinase, inhibited augmentation of endothelin-1 expression stimulated with leptin. Leptin induced significant tyrosine phosphorylation of epidermal growth factor receptor, which was significantly attenuated by two inhibitors, an epidermal growth factor receptor tyrosine kinase inhibitor, AG1478, and a broad-spectrum matrix metalloproteinase inhibitor, GM6001. This indicates that the pathway of epidermal growth factor receptor transactivation induced by leptin is dependent on proteolytically released epidermal growth factor receptor ligands. Pretreatment of cells with AG1478 significantly reduced the degree of phosphorylation of extracellular signal-regulated kinase and endothelin-1 expression. Our results reveal that epidermal growth factor receptor transactivation is involved in the leptin signaling pathway in vascular smooth muscle cells, which may be related to the increased risk of hypertension and other cardiovascular diseases in obese subjects.
 ...
PMID:Leptin stimulates endothelin-1 expression via extracellular signal-regulated kinase by epidermal growth factor receptor transactivation in rat aortic smooth muscle cells. 1767 88

Pancreatic beta-cell dysfunction is an important pathological change in type 2 diabetes, which is tightly related to obesity. However, the direct role of adipose tissue in beta-cell dysfunction has not been well understood. In this study, we examined the effects of 3T3-L1 adipocytes on MIN6 insulin-secreting cells in a co-culture system. MIN6 cells used here kept most of beta-cell functions but less sensitive to glucose stimulation. Tolbutamide, the KATP channel blocker, was therefore used to stimulate insulin secretion in this report. MIN6 cells co-cultured with 3T3-L1 adipocytes had significantly reduced intracellular calcium concentration ([Ca2+]i) and lost the ability to secrete insulin in response to tolbutamide, compared to the control cells. 3T3-L1 adipocytes significantly decreased the expression of insulin, glucokinase and Kir6.2 genes but increased the expression of uncoupling protein-2 (UCP-2) in MIN6 cells after one week of co-culture, as measured by semi-quantitative RT-PCR. 3T3-L1 adipocyte-conditioned medium also significantly decreased insulin secretion and the expression of insulin, glucokinase and Kir6.2 genes in MIN6 cells. The conditioned medium also reduced tyrosine kinase activity in MIN6 cells. The inhibitor of protein tyrosine kinase, genistein, decreased the expression of glucokinase and Kir6.2 in MIN6 cells, while two free fatty acids, oleic acid and linoleic acids, were found to increase UCP-2 expression. The present study demonstrates that 3T3-L1 adipocytes directly impair insulin secretion and the expression of important genes in MIN6 cells. The effects of T3-L1 adipocytes on MIN6 cells are ascribed to secreted bioactive factors and may be mediated via multiple pathways, which include the upregulation of UCP-2 expression via free fatty acids, and downregulation of glucokinase and Kir6.2 expression via decreasing protein tyrosine kinase activity.
 ...
PMID:3T3-L1 adipocytes induce dysfunction of MIN6 insulin-secreting cells via multiple pathways mediated by secretory factors in a co-culture system. 1770 98

Insulin controls carbohydrate and lipid metabolism. Among other things, it stimulates glucose storage as glycogen and lipid storage as triglycerides. Insulin acts through a membrane receptor which is a tyrosine kinase. When activated by insulin binding, the tyrosine kinase will recruit and phosphorylate intracellular substrates called IRS (insulin receptor substrate). Phosphorylated IRS will be used as docking sites for proteins which will transmit the insulin signal through several systems (e.g. PI3-kinase). The insulin resistance which is concomitant with type 2 diabetes and obesity is linked to an increased intracellular availability of fatty acids which are precursors of lipid mediators inducing a decreased efficiency of insulin signal transmission. Therapies aimed at improving insulin sensitivity could then target proteins involved in the regulation of intacellular fatty acid availibility.
 ...
PMID:[Insulin signaling and insulin resistance]. 1798 53


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>