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)

Albright hereditary osteodystrophy (AHO), a disorder characterized by skeletal abnormalities and obesity, is associated with heterozygous inactivating mutations in the gene for Gsalpha. A novel Gsalpha mutation encoding the substitution of tryptophan for a nonconserved arginine within the switch 3 region (Gsalpha R258W) was identified in an AHO patient. Although reverse transcription-polymerase chain reaction studies demonstrated that mRNA expression from wild type and mutant alleles was similar, Gsalpha expression in erythrocyte membranes from the affected patient was reduced by 50%. A Gsalpha R258W cDNA, as well as one with arginine replaced by alanine (Gsalpha R258A), was generated, and the biochemical properties of in vitro transcription/translation products were examined. When reconstituted with cyc- membranes, both mutant proteins were able to stimulate adenylyl cyclase normally in the presence of guanosine- 5'-O-(3-thiotriphosphate) (GTPgammaS) but had decreased ability in the presence of isoproterenol or AlF4- (a mixture of 10 microM AlCl3 and 10 mM NaF). The ability of each mutant to bind and be activated by GTPgammaS or AlF4- was assessed by trypsin protection assays. Both mutants were protected normally by GTPgammaS but showed reduced protection in the presence of AlF4-. The addition of excess GDP (2 mM) was able to rescue the ability of AlF4- to protect the mutants, suggesting that they might have reduced affinity for GDP. A Gsalpha R258A mutant purified from Escherichia coli had decreased affinity for GDP and an apparent rate of GDP release that was 10-fold greater than that of wild type Gsalpha. Sucrose density gradient analysis demonstrated that both Gsalpha R258W and Gsalpha R258A were thermolabile at higher temperatures and that denaturation of both mutants was prevented by the presence of 0.1 mM GTPgammaS or 2 mM GDP. The crystal structure of Gsalpha demonstrates that Arg258 interacts with a conserved residue in the helical domain (Gln170). Arg258 substitutions would be predicted to open the cleft between the GTPase and helical domains, allowing for increased GDP release in the inactive state, resulting in enhanced thermolability and reduced AlF4--induced adenylyl cyclase stimulation and trypsin protection, since activation by AlF4- requires bound GDP.
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PMID:A novel mutation in the switch 3 region of Gsalpha in a patient with Albright hereditary osteodystrophy impairs GDP binding and receptor activation. 972 13

Progressive osseous heteroplasia (POH) is a rare disorder characterized by dermal ossification beginning in infancy followed by increasing and extensive bone formation in deep muscle and fascia. We describe two unrelated girls with typical clinical, radiographic, and histological features of POH who also have findings of another uncommon heritable disorder, Albright hereditary osteodystrophy (AHO). One patient has mild brachydactyly but no endocrinopathy, whereas the other manifests brachydactyly, obesity, and target tissue resistance to thyrotropin and parathyroid hormone (PTH). Levels of the alpha-subunit of the G protein (Gsalpha) were reduced in erythrocyte membranes from both girls and a nonsense mutation (Q12X) in exon 1 of the GNAS1 gene was identified in genomic DNA from the mildly affected patient. Features of POH and AHO in two individuals suggest that these conditions share a similar molecular basis and pathogenesis and that isolated severe extraskeletal ossification may be another manifestation of Gsalpha deficiency.
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PMID:Deficiency of the alpha-subunit of the stimulatory G protein and severe extraskeletal ossification. 1109 90

Pseudohypoparathyroidism Ia (PHP-Ia), is an inherited disease with clinical hypoparathyroidism caused by parathyroid hormone resistance (PTH), and shows the phenotype of Albright hereditary osteodystrophy (AHO), including short stature, obesity, round face, brachydactyly, and subcutaneous ossification. This disease is caused by mutation that inactivates the alpha-subunit of Gs, the stimulatory regulator of adenylyl cyclase. Here, a novel frameshift mutation (delG at codon 88) in exon 4, and a missense mutation (R231H) in exon 9 of the Gsalpha gene were identified in two Japanese patients with sporadic PHP-Ia. Deletion of a G in exon 4 at codon 88 in the first patient produced a premature stop codon, resulting in the truncated protein. The second patient had a previously reported R231H mutation. Because this amino acid is located in a region, switch 2, that is thought to interact with the betagamma subunit of Gsalpha protein, this mutation may impair Gs protein function. We report here one novel Gsalpha mutation, and note that mutations in Japanese patients with PHP-Ia are probably heterogeneous.
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PMID:Two mutations of the Gsalpha gene in two Japanese patients with sporadic pseudohypoparathyroidism type Ia. 1145 Aug 52

Pseudohypoparathyroidism (PHP) and Albright's hereditary osteodystrophy (AHO) are not interchangeable terms. AHO describes a constellation of physical features, including short adult stature, obesity, brachydactyly, and ectopic ossifications. PHP means end-organ resistance to PTH and is subclassified into types Ia, Ib, and Ic and type II. Pseudopseudohypoparathyroidism (PPHP) is a term used for individuals with AHO who have normal end-organ responses to PTH. Both the PHPIa and PPHP forms of AHO result from heterozygous deactivating mutations in the GNAS1 gene associated with a 50% reduction in bioactivity of the Gsalpha protein that it encodes. The GNAS1 gene is subject to tissue-specific genomic imprinting. Patients with mutations on their maternally derived allele are likely to have associated PHPIa, whereas mutations on the paternal allele usually cause PPHP. Isolated PTH resistance (PHPIb) can result from mutations within the GNAS1 gene but is more commonly caused by epigenetic imprinting abnormalities affecting the upstream exon 1A. The causes of PHP type Ic and PHP type II are not yet clear, and the latter is likely to be heterogeneous.
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PMID:Albright's hereditary osteodystrophy and pseudohypoparathyroidism. 1254 Nov 84

Mutations of the Gsalpha gene inherited from the mother lead to pseudohypoparathyroidism (PHP) type Ia (PHP Ia), in which Albright's hereditary osteodistrophy is associated to resistance to the action of different hormones, whereas the same mutations inherited from the father lead to isolated Albright's hereditary osteodistrophy [pseudo-PHP (PPHP)]. Accordingly, it has been suggested that Gsalpha is under tissue-specific imprinting control, and recent studies provided evidence for a predominant maternal origin of Gsalpha transcripts in different endocrine organs involved in the PHP Ia phenotype. To establish whether Gsalpha is imprinted also in tissues that are site of alteration both in PHP Ia and PPHP, we selected 20 bone and 10 adipose tissue samples, which were heterozygous for a known polymorphism in exon 5. Expression from both parental alleles was evaluated by RT-PCR and enzymatic digestion of the resulting fragments. By this approach, the great majority of the samples analyzed showed an equal expression of the two alleles. Our results provide evidence for the absence of Gsalpha imprinting in human bone and fat and suggest that the clinical finding of osteodystrophy and obesity in PHP Ia and PPHP patients despite the presence of a normal Gsalpha allele is likely due to Gsalpha haploinsufficiency in these tissues.
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PMID:Biallelic expression of the Gsalpha gene in human bone and adipose tissue. 1557 96

Impaired leptin signalling in obesity is increasingly implicated in cardiovascular pathophysiology. To explore mechanisms for leptin activity in the heart, we hypothesized that physiological leptin signalling participates in maintaining cardiac beta-adrenergic regulation of excitation-contraction coupling. We studied 10-week-old (before development of cardiac hypertrophy) leptin-deficient (ob/ob, n=12) and C57Bl/6 (wild-type (WT), n=15) mice at baseline and after recombinant leptin infusion (0.3 mg kg-1 day-1 for 28 days, n=6 in each group). Ob/ob-isolated myocytes had attenuated sarcomere shortening and calcium transients ([Ca2+]i) versus WT (P<0.01 for both) following stimulation of the beta-receptor (with isoproterenol (isoprenaline)) or at the post-receptor level (with forskolin and dibutryl-cAMP). In addition, sarcoplasmic reticulum (SR) Ca2+ stores were depressed. Leptin replenishment in ob/ob mice restored each of these abnormalities towards normal without affecting gross (wall thickness) or microscopic (cell size) measures of cardiac architecture. Immunoblots revealed alterations of several proteins involved in excitation-contraction coupling in the ob/ob mice, including decreased abundance of Gsalpha-52 kDa, as well as alterations in the expression of Ca2+ cycling proteins (increased SR Ca2+-ATPase, and depressed phosphorylated phospholamban). In addition, protein kinase A (PKA) activity in ob/ob mice was depressed at baseline and correctable towards the activity found in WT with leptin repletion, a finding that could account for impaired beta-adrenergic responsiveness. Taken together, these data reveal a novel link between the leptin signalling pathway and normal cardiac function and suggest a mechanism by which leptin deficiency or resistance may lead to cardiac depression.
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PMID:Leptin repletion restores depressed {beta}-adrenergic contractility in ob/ob mice independently of cardiac hypertrophy. 1576 Sep 36

Albright hereditary osteodystrophy (AHO) is characterized by a symptom complex including short stature, brachymetacarpia, obesity, round facies, cutaneous osteomas, and mental retardation. AHO is caused by mutations in the GNAS-gene localized on chromosome 20 encoding for Gsalpha protein, a signal transducer of endocrine pathways. Therefore, AHO is often associated with endocrinopathy such as pseudohypoparathyroidism or hypothyroidism. A nine-month-old boy presented with typical features of this syndrome. The diagnosis was confirmed by biochemical and molecular analyses. An unusual feature was calcinosis cutis at such an early age, which led to extensive differential diagnostic procedures.
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PMID:[Calcinosis cutis in Albright hereditary osteodystrophy: pseudohypoparathyroidism type Ia]. 1627 Feb 3

Pseudohypoparathyroidism type Ia (PHP-Ia) is characterized by Albright's hereditary osteodistrophy (AHO) and resistance to hormones that act via the alpha subunit of the Gs protein (Gsalpha) protein, ie PTH, TSH, FSH/LH, and, as recently described in limited series, GHRH. However, the current lack of data on GHRH secretion, obesity and short stature included in the AHO phenotype hampers interpretation of GH secretory status and its effects on these subjects. We evaluated GH secretion after GHRH plus arginine (Arg) stimulus, IGF-I levels and anthropometric features in an exclusively pediatric population of 10 PHP-Ia subjects. Of our PHP-Ia children, 5 out of 10 (50%) showed impaired GH responsiveness to the provocative test, with a lower prevalence than the 75-100% previously reported. A negative correlation (p=0.024) was found between GH secretion and body mass index (BMI), whereas no correlation emerged between GH and IGF-I values (p=0.948). Height and growth velocity did not significantly differ between GH-deficient and GH-sufficient subjects. In the 5 GH-deficient patients, GHRH resistance could arguably be responsible for hormonal impairment; however, 3 of them were obese, showing normal stature and IGF-I levels: the increased BMI in these subjects could influence GH secretion and its effects. In conclusion, GH deficiency is frequent among PHP-Ia children and its prevalence is variable, two factors indicating that GH secretory testing should be part of the routine management of this patient group. It could be argued that GHRH resistance is the pathogenetic mechanism in most patients, but further studies on GHRH secretion are needed to define which values can be considered as raised. Lastly, because BMI has been indicated as a major determinant of evoked adult GH response to provocative testing, GH levels related to increased BMI also in childhood could be helpful in defining GH assessment in obese or overweight PHP-Ia children.
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PMID:GH secretion in a cohort of children with pseudohypoparathyroidism type Ia. 1739 98

Pseudopseudohypoparathyroidism (PPHP) is caused by the paternally-derived mutation in the coding region of GNAS gene. The phenotype of PPHP is produced by the sum of both decreased Gsalpha protein in biallelically expressed tissues and other proteins or non-coding RNAs by mutated paternal-allele specific expression. It has been believed that the haploinsufficiency of Gsalpha in non-imprinted tissues is responsible for the Albright hereditary dystrophy (AHO) phenotype. Recently it was reported that obesity is a more prominent feature in pseudohypoparathyroidism type I a than in PPHP. This result implicates paternal imprinting in the development of obesity in pseudohypoparathyroidism type I a. In this review, recent advances in clinical and experimental knowledge in genomic imprinting of GNAS gene were summarized.
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PMID:[Pseudopseudohypoparathyroidism and genomic imprinting]. 1766 Jun 20

Albright hereditary osteodystrophy (AHO), also known as Martin-Albright syndrome (MAS), is a rare autosomal dominantly transmitted disease characterized by short stature, obesity, mental retardation, a round facies, and brachymetacarpia and -tarsia, as well as cutaneous calcification. The disease is caused by mutations in the GNAS gene localized on chromosome 20q13.2 encoding for an adenyl-cyclase-stimulating protein (Gsalpha). A 58-year-old patient presented with small stature since childhood, moderate mental retardation, round facies and soft tissue masses on the thighs. A biopsy of the latter showed subcutaneous ossification. Laboratory results showed hypocalcemia, as well as increased plasma levels of PTH and calcitonin. The clinical diagnosis was confirmed by detection of reduced activity of Gsalpha. In patients with cutaneous calcification and disturbed calcium metabolism, AHO is an important differential diagnostic consideration.
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PMID:First diagnosis of Martin-Albright syndrome in a 58-year-old patient. 1913 95


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