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

Anitobesity drugs must increase the sensitivity of the hypothalamic satiety center towards leptin and antagonize the synthesis and action of NPY. The array of pharmacologic tools available is vast and presently ineffective. Among peptide analogs considered for evaluation [NPY-5 antagonists and CCK-A, bombesin, amylin and melanocyte-stimulating hormone-4 (or melanin-concentrating hormone?) agonists], is there a place for GLP-1 and PACAP? GLP-1 receptors present in ARC, PVN, VMN, and SON are the target for both central and blood-borne GLP-1 in those hypothalamic neurons endowed with GLUT-2 and glucokinase. GLP-1, hypersecreted by L-cells after a meal, is a potent insulinotropic agent and, together with glucose, reduces food intake and induces c-fos in the ARC. PACAP is present in the ARC, PVN, and SCH, and its hypothalamic type I receptor elevates cAMP and inositol triphosphate in the PVN, where it may perhaps antagonize NPY-induced food intake and hyperinsulinemia. However, irrelevant neuroendocrine, autonomic, and circadian functions are also activated by this peptide, making it a less than ideal base on which to build an obesity treatment.
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PMID:Is there appetite after GLP-1 and PACAP? 992 26

Uncoupling proteins (UCPs) are mitochondrial membrane transporters which are involved in dissipating the proton electrochemical gradient thereby releasing stored energy as heat. This implies a major role of UCPs in energy metabolism and thermogenesis which when deregulated are key risk factors for the development of obesity and other eating disorders. Recent studies have shown that the sympathetic nervous system, via norepinephrine (beta-adrenoceptors) and cAMP, as well as thyroid hormones and PPAR gamma ligands seem to be major regulators of UCP expression. From the three different UCPs identified so far by gene cloning UCP1 is expressed exclusively in brown adipocytes while UCP2 is widely expressed. The third analogue, UCP3, is expressed predominantly in human skeletal muscle and was found to exist in a long and a short form. At the amino acid level UCP2 has about 59% homology to UCP1 while UCP3 is 73% identical to UCP2. Both UCP2 and UCP3 were mapped in close proximity (75-150 kb) to regions of human chromosome 11 (11q13) that have been linked to obesity and hyper-insulinaemia. Furthermore, there is strong evidence that UCP2, by virtue of its ubiquitous expression, may be important for determining basal metabolic rate. Based on the published full-length cDNA sequence we have deduced the genomic structure of the human UCP2 (hUCP2) gene by PCR and direct sequence analysis. The hUCP2 gene spans over 8.4 kb distributed on 8 exons. The localization of the exon/intron boundaries within the coding region matches precisely the one found in the human UCP1 gene and is almost conserved in the recently discovered UCP3 gene as well. However, the size of each of the introns in the hUCP2 gene differs from its UCP1 and UCP3 counterparts. It varies from 81 bp (intron 5) to about 3 kb (intron 2). The high degree of homology at the nucleotide level and the conservation of the exon/intron boundaries among the three UCP genes suggests that they may have evolved from a common ancestor or are the result from gene duplication events. Mutational analysis of the hUCP2 gene in a cohort of 25 children of caucasian origin (aged 7-13) characterized by low BMR values revealed a point mutation in exon 4 (C to T transition at position 164 of the corresponding cDNA resulting in the substitution of an alanine residue by a valine at codon 55) and an insertion polymorphism in exon 8. The insertion polymorphism consists of a 45 bp repeat located 150 bp downstream of the stop codon in the 3'-UTR. The allele frequencies were 0.61 and 0.39 for the alanine and valine encoded alleles, respectively, and 0.71 versus 0.29 for the insertion polymorphism. Expression studies of the wildtype and mutant forms of UCP2 should clarify the functional consequences these mutations may have on energy metabolism and body weight regulation. In addition, mapping of the promoter region and the identification of putative promoter regulatory sequences should give insight into the transcriptional regulation of UCP2 expression--in particular by anyone of the above mentioned factors--in vitro and in vivo.
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PMID:Genomic organization and mutational analysis of the human UCP2 gene, a prime candidate gene for human obesity. 1007 61

Leptin, a protein encoded by the ob gene, is an adipose tissue-derived signaling factor involved in body weight homeostasis. The hypothalamus is a major site of central action for leptin. However, mounting evidence indicates expression of leptin receptor mRNA in various peripheral organs including the adrenal medulla. Therefore, we investigated the effects of leptin on catecholamine secretion and synthesis in cultured porcine adrenal medullary chromaffin cells. We initially confirmed the expression of leptin receptor (Ob-Rb) mRNA in cultured porcine adrenal medullary cells. Murine recombinant leptin (>==50 nM) strongly induced the release of both epinephrine (E) and norepinephrine (NE) from chromaffin cells. Removal of external Ca(2+) significantly suppressed these effects. Also, leptin (>==1 nM) enhanced nicotine-induced increases in E- and NE. Leptin (1, 10, 100 nM) significantly increased tyrosine hydroxylase (TH) (a rate-limiting enzyme in the biosynthesis of catecholamine) mRNA levels in a concentration-dependent manner. Furthermore, leptin (1, 10, 100 nM) significantly induced increases in cAMP levels, suggesting that the stimulatory effects on TH mRNA are mediated, at least in part, by the cAMP/protein kinase A pathway. These results indicate that leptin directly stimulates catecholamine release and synthesis, which in turn may potentiate the anti-obesity effects of leptin.
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PMID:Leptin directly stimulates catecholamine secretion and synthesis in cultured porcine adrenal medullary chromaffin cells. 1042 1

Recent studies have shown that genetic deficiency of the adipocyte fatty acid-binding protein (aP2) results in minor alterations of plasma lipids and adipocyte development but provides significant protection from dietary obesity-induced hyperinsulinemia and insulin resistance. To identify potential mechanisms responsible for this phenotype, we examined lipolysis and insulin secretion in aP2-/- mice. Beta-adrenergic stimulation resulted in a blunted rise of blood glycerol levels in aP2-/- compared with aP2+/+ mice, suggesting diminished lipolysis in aP2-/- adipocytes. Confirming this, primary adipocytes isolated from aP2-/- mice showed attenuated glycerol and free fatty acid (FFA) release in response to dibutyryl cAMP. The decreased lipolytic response seen in the aP2-/- mice was not associated with altered expression levels of hormone-sensitive lipase or perilipin. The acute insulin secretory response to beta-adrenergic stimulation was also profoundly suppressed in aP2-/- mice despite comparable total concentrations and only minor changes in the composition of systemic FFAs. To address whether levels of specific fatty acids are different in aP2-/- mice, the plasma FFA profile after beta-adrenergic stimulation was determined. Significant reduction in both stearic and cis-11-eicoseneic acids and an increase in palmitoleic acid were observed. The response of aP2-/- mice to other insulin secretagogues such as arginine and glyburide was similar to that of aP2+/+ mice, arguing against generally impaired function of pancreatic beta-cells. Finally, no aP2 expression was detected in isolated pancreatic islet cells. These results provide support for the existence of an adipo-pancreatic axis, the proper action of which relies on the presence of aP2. Consequently, aP2's role in the pathogenesis of type 2 diabetes might involve regulation of both hyperinsulinemia and insulin resistance through its impact on both lipolysis and insulin secretion.
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PMID:Altered insulin secretion associated with reduced lipolytic efficiency in aP2-/- mice. 1051 63

We investigated the beta-adrenergic receptor (AR) agonistic activities in rats and humans, and the anti-obesity and anti-diabetic activities in KK-Ay mice, of a new beta3-AR agonist, SWR-0342SA ((S)-(Z)-[4-[[1-[2-[(2-hydroxy-3-phenoxypropyl)]amino]ethyl]-1-pro penyl]phenoxy] acetic acid ethanedioic acid). With regards to its beta-AR agonistic activity in rats, SWR-0342SA stimulated the atrial beating rate (beta1-AR activity) and white adipocyte lipolysis (beta3-AR activity), but did not induce uterine muscle relaxation (beta2-AR activity). The beta3-AR agonistic activity of SWR-0342SA was about 20 times stronger than its beta1-AR agonistic activity. Similarly, SWR-0342SA enhanced the accumulation of cAMP in Chinese hamster ovary (CHO) cells expressing human beta1- and beta3-ARs, while having no effect in CHO cells expressing beta2-ARs. Adenylyl cyclase stimulation by SWR-0342SA in CHO cells expressing beta3-ARs was about 35 times higher than that in CHO cells expressing beta1-ARs. With regards to anti-obesity and anti-diabetic activities, SWR-0342SA had no effect on body weight or food intake, but slightly decreased the fat pads weight in KK-Ay mice, an animal model of obesity and non-insulin-dependent diabetes mellitus (NIDDM). On the other hand, SWR-0342SA significantly decreased both blood glucose (to about 46% of control) and serum insulin levels (to about 40% of control) in KK-Ay mice. These results indicated that SWR-0342SA is a selective beta3-AR agonist, and possesses potent anti-diabetic activity, and that the anti-obesity activity is inferior to the anti-diabetic activity.
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PMID:Anti-obesity and anti-diabetic activities of a new beta3 adrenergic receptor agonist, (S)-(Z)-[4-[[1-[2-[(2-hydroxy-3-phenoxypropyl)]amino]ethyl]-1-propenyl] phenoxy] acetic acid ethanedioic acid (SWR-0342SA), in KK-Ay mice. 1054 58

Plasma levels of type 1 plasminogen activator inhibitor (PAI-1), a risk factor for cardiovascular disease, are elevated in obese subjects, especially those with omental fat accumulation. We investigated the hormonal control of PAI-1 gene expression and secretion in cultured human adipose tissue. We more particularly focused on the effects of glucocorticoids, insulin, cAMP, and catecholamines in explants from the omental region. The addition of dexamethasone to the culture medium increased PAI-1 secretion in a time-dependent manner for up to 24 h. The stimulation by the glucocorticoid was preceded by a 2-fold rise in PAI-1 messenger ribonucleic acid levels between 4-8 h of culture. The effectiveness of the glucocorticoid was concentration dependent, with a half-maximal effect within a physiological range. This stimulation was also observed in sc fat, but dexamethasone-stimulated as well as basal PAI-1 secretion rates were always higher in omental fat. Unlike dexamethasone, 24-h insulin did not modify PAI-1 secretion while accelerating glucose consumption. In contrast, 24-h cAMP inhibited PAI-1 gene expression and protein production under basal conditions and in the presence of dexamethasone. This inhibition was already detectable after 1 h and was maximal after 4 h at the level of gene expression. It occurred in both omental and sc adipose tissues. Importantly, epinephrine dose dependently inhibited PAI-1 parameters, an effect that was reproduced by isoproterenol. Dexamethasone- and cAMP-induced changes in PAI-1 messenger ribonucleic acid abundance were similar in explants and isolated fat cells. In isolated stromal-vascular cells, only dexamethasone was effective. In conclusion, we provide evidence for a reciprocal regulation of PAI-1 by dexamethasone (positive effector) and cAMP/catecholamines (negative effectors) in cultured human adipose tissue. The stimulation by glucocorticoids could contribute to enhanced production of PAI-1 by adipose tissue and high plasma levels of PAI-1 associated with central obesity and thereby be a link between this disorder and cardiovascular disease. Impaired inhibition by catecholamines could also contribute, as in vivo adipose tissue responses to these hormones are usually blunted in obese individuals.
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PMID:Hormonal control of plasminogen activator inhibitor-1 gene expression and production in human adipose tissue: stimulation by glucocorticoids and inhibition by catecholamines. 1056 56

Targeted disruption of the RIIbeta subunit of protein kinase A (PKA) produces lean mice that resist diet-induced obesity. In this report we examine the effects of the RIIbeta knockout on white adipose tissue physiology. Loss of RIIbeta is compensated by an increase in the RIalpha isoform, generating an isoform switch from a type II to a type I PKA. Type I holoenzyme binds cAMP more avidly and is more easily activated than the type II enzyme. These alterations are associated with increases in both basal kinase activity and the basal rate of lipolysis, possibly contributing to the lean phenotype. However, the ability of both beta(3)-selective and nonspecific beta-adrenergic agonists to stimulate lipolysis is markedly compromised in mutant white adipose tissue. This defect was found in vitro and in vivo and does not result from reduced expression of beta-adrenergic receptor or hormone-sensitive lipase genes. In contrast, beta-adrenergic stimulated gene transcription remains intact, and the expression of key genes involved in lipid metabolism is normal under both fasted and fed conditions. We suggest that the R subunit isoform switch disrupts the subcellular localization of PKA that is required for efficient transduction of signals that modulate lipolysis but not for those that mediate gene expression.
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PMID:Mutation of the RIIbeta subunit of protein kinase A differentially affects lipolysis but not gene induction in white adipose tissue. 1059 17

Obesity is the result of numerous, interacting behavioral, physiological, and biochemical factors. One increasingly important factor is the generation of additional fat cells, or adipocytes, in response to excess feeding and/or large increases in body fat composition. The generation of new adipocytes is controlled by several "adipocyte-specific" transcription factors that regulate preadipocyte proliferation and adipogenesis. Generally these adipocyte-specific factors are expressed only following the induction of adipogenesis. The transcription factor(s) that are involved in initiating adipocyte differentiation have not been identified. Here we demonstrate that the transcription factor, CREB, is constitutively expressed in preadipocytes and throughout the differentiation process and that CREB is stimulated by conventional differentiation-inducing agents such as insulin, dexamethasone, and dibutyryl cAMP. Stably transfected 3T3-L1 preadipocytes were generated in which we could induce the expression of either a constitutively active CREB (VP16-CREB) or a dominant-negative CREB (KCREB). Inducible expression of VP16-CREB alone was sufficient to initiate adipogenesis as determined by triacylglycerol storage, cell morphology, and the expression of two adipocyte marker genes, peroxisome proliferator activated receptor gamma 2, and fatty acid binding protein. Alternatively, KCREB alone blocked adipogenesis in cells treated with conventional differentiation-inducing agents. These data indicate that activation of CREB was necessary and sufficient to induce adipogenesis. Finally, CREB was shown to bind to putative CRE sequences in the promoters of several adipocyte-specific genes. These data firmly establish CREB as a primary regulator of adipogenesis and suggest that CREB may play similar roles in other cells and tissues.
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PMID:CREB activation induces adipogenesis in 3T3-L1 cells. 1062 58

The thermogenic effect of tea is generally attributed to its caffeine content. We report here that a green tea extract stimulates brown adipose tissue thermogenesis to an extent which is much greater than can be attributed to its caffeine content per se, and that its thermogenic properties could reside primarily in an interaction between its high content in catechin-polyphenols and caffeine with sympathetically released noradrenaline (NA). Since catechin-polyphenols are known to be capable of inhibiting catechol-O-methyl-transferase (the enzyme that degrades NA), and caffeine to inhibit trancellular phosphodiesterases (enzymes that break down NA-induced cAMP), it is proposed that the green tea extract, via its catechin-polyphenols and caffeine, is effective in stimulating thermogenesis by relieving inhibition at different control points along the NA-cAMP axis. Such a synergistic interaction between catechin-polyphenols and caffeine to augment and prolong sympathetic stimulation of thermogenesis could be of value in assisting the management of obesity. International Journal of Obesity (2000) 24, 252-258
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PMID:Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity. 1070 79

The type RIIbeta regulatory subunit of protein kinase A is primarily expressed in adipose tissue and brain. Knockout mice suggest a role for RIIbeta in regulating energy balance and adipose-tissue content, thus making it a potential target for therapeutic intervention in obesity. A truncated version of the RIalpha subunit has been used in a crystallographic study and was used here to design an analogous RIIbeta construct. Despite substantial screening, conditions were not found for the crystallization of the truncated RIIbeta subunit. However, limited proteolysis of the full-length RIIbeta subunit identified boundaries of the 'hinge' region and a fragment containing the two cAMP-binding domains which did crystallize. A recombinant version of the fragment was expressed and crystallized for X-ray diffraction studies. The crystals belong to the orthorhombic space group C222, with unit-cell parameters a = 91.6, b = 105.9, c = 85.8 A, and diffracted to at least 2.3 A.
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PMID:A crystallizable form of RIIbeta regulatory domain obtained by limited proteolysis. 1094 47


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