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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ob gene encodes a protein that, in mutant form, is associated with obesity and type II diabetes in mice. Sequence analysis has revealed no similarities to other proteins, however, and no clues as to possible functions. The possibility nonetheless remains that ob is functionally or ancestrally related to other proteins, whose sequences are divergent to the point that only a comparison of three-dimensional structures might detect relationship. To explore this possibility, we conduct a 'threading' search of a 3-dimensional structure database, to determine whether the ob protein might adopt a fold similar to any known structure. This search reveals that the ob sequence is compatible, at a significance level of P < 0.05, with structures from the family of helical cytokines that includes interleukin-2 and growth hormone. A structural model of ob based upon these results is physically and biologically plausible and leads to testable predictions, including the prediction that ob may activate the JAK-STAT pathway, via binding to a receptor resembling those of the cytokine family.
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PMID:Threading analysis suggests that the obese gene product may be a helical cytokine. 758 24

The obese (ob) gene, the mutation of which results in severe hereditary obesity and diabetes in mice, has recently been isolated through positional cloning. In this study, we isolated a full-length human ob complementary DNA (cDNA) clone and examined the tissue distribution of ob gene expression in humans. The nucleotide sequences of the human ob cDNA coding region were 83% identical to those of the mouse and rat ob cDNA coding regions. Analysis of the deduced amino acid sequences revealed that the human ob protein is a 166-amino acid polypeptide with a putative signal sequence and is 84 and 83% homologous to the mouse and rat ob proteins, respectively. Northern blot analysis using the cloned human ob cDNA fragment as a probe identified a single messenger RNA (mRNA) species 4.5 kb in size found abundantly in the adipose tissues obtained from the subcutaneous, omental, retroperitoneal, perilymphatic, and mesenteric fat pads. However, no significant amount of ob mRNA was present in the brain, heart, lung, liver, stomach, pancreas, spleen, small intestine, kidney, prostate, testis, colon, or skeletal muscle. The ob mRNA level in the adipose tissue varied from region to region even in the same individual. Furthermore, in the human adipose tissue, ob gene expression occurred in mature adipocytes rather than in stromal-vascular cells. This study is the first report of the elucidation of ob gene expression in human tissues, thereby leading to better understanding of the physiological and clinical implications of the ob gene.
Diabetes 1995 Jul
PMID:Human obese gene expression. Adipocyte-specific expression and regional differences in the adipose tissue. 778 54

The mouse obese (ob) gene has recently been isolated through the positional cloning technique and has been proved to result in the obese and NIDDM phenotype in mice when mutated (Nature 372:425-432, 1994). More recently, it has been demonstrated, by experiments with recombinant ob protein, that ob gene product can cause mice, including ob/ob mice, diet-induced obesity mice, and normal mice, to lower their food intake and body weight (Science 269:540-549, 1995). To investigate the genetic and/or environmental influences underlying the development of NIDDM associated with obesity, we isolated and partially sequenced the human obese (OB) gene. The human OB gene isolated in this study encoded 167 amino acids and its open reading frame was revealed to be divided into two parts with an intermediate intron of approximately 2.4 kb. Using the single-strand conformation polymorphism (SSCP) technique, we screened Japanese and Asian Indian subjects for mutations in the protein coding regions of the OB gene. A total of 75 NIDDM patients with obesity (54 Japanese and 21 Asian Indians), 40 NIDDM patients without obesity (34 Japanese and 6 Asian Indians), and 34 Japanese patients with simple obesity showed no abnormal SSCP patterns in either component of the coding sequences. These results suggested that mutations in the coding regions of the OB gene are not likely to be commonly identifiable and that there would likely be a kind of obesity-associated NIDDM not caused by mutations of the OB gene.
Diabetes 1996 May
PMID:Human obese gene: molecular screening in Japanese and Asian Indian NIDDM patients associated with obesity. 862 Oct 21

Obesity is one of the most significant risk factors for hypertension, coronary heart disease, and NIDDM (Frayn KN, Coppack SW: Insulin resistance, adipose tissue and coronary heart disease. Clin Sci 82:1-8, 1992; Kaplan NM: The deadly quartet: upper-body obesity, glucose intolerance, hypertriglyceridemia, and hypertension. Arch Intern Med 149:1514-1520, 1989). While family segregation, adoption, and twin studies have indicated that degree of adiposity has a significant genetic component (Stunkard AJ, Harris JR, Pedersen NL, McClearn GE: The body-mass index of twins who have been reared apart. N Engl J Med 322:1483-1487, 1990; Bouchard C, Despres J-P, Mauriege P: Genetic and nongenetic determinants of regional fat distribution. Endocr Rev 14:72-93, 1993), the genes and predisposing mutations remain poorly understood. This is in contrast to several well-defined genetic models for obesity in rodents, particularly the mouse obese (ob) gene, in which loss-of-function mutations cause severe obesity. Recent studies have demonstrated a substantial reduction in body fat when recombinant ob protein (leptin) is administered to mice. To test the relevance of these observations to human obesity, the location of the human homologue (OB) was established by radiation hybrid mapping and eight microsatellite markers spanning the OB gene region (7q3l.3) were genotyped in 101 obese French families. Affected-sib-pair analyses for extreme obesity, defined by BMI >35 kg/m2, revealed suggestive evidence for linkage to three markers located within 2 cM of the OB gene (D7S514, D7S680, and D7S530). The OB gene is therefore a candidate for genetic predisposition to extreme obesity in a subset of these families.
Diabetes 1996 May
PMID:Indication for linkage of the human OB gene region with extreme obesity. 862 Oct 24

Hyperinsulinemia. is associated with an overexpression of mRNA for the ob protein leptin in rodent models of genetic obesity, and insulin has been reported to directly stimulate leptin mRNA in rat adipocytes. Human obesity is also associated with increased leptin mRNA as well as plasma levels, but there have been no reports of the effect of insulin on leptin secretion. We, therefore, tested the hypothesis that insulin stimulates leptin secretion in humans. Using a newly developed leptin assay, immunoreactive leptin was measured in fasting and postprandial plasma samples from 27 healthy adults and in samples before and during euglycemic-hyperinsulinemic then stepped hypoglycemic (hourly steps at 85, 75, 65, 55, and 45 mg/dl) clamps from 10 healthy subjects and 11 patients with IDDM. Plasma leptin was correlated (r = 0.84, P = 0.0005) with BMI in obese but not nonobese subjects and with fasting (r = 0.75, P = 0.008) but not postprandial plasma insulin levels. (Leptin levels did not change postprandially.) Euglycemic hyperinsulinemia did not alter leptin levels, nor did hyperinsulinemic hypoglycemia. Thus, because circulating leptin levels are not increased during postprandial hyperinsulinemia or during euglycemic (or hypoglycemic) hyperinsulinemia, we conclude that, at least in the short term, insulin does not increase leptin secretion in humans and that hyperleptinemia in obese individuals is not likely the result of hyperinsulinemia.
Diabetes 1996 May
PMID:Plasma leptin and insulin relationships in obese and nonobese humans. 862 Oct 26

Studies of the obese gene are reviewed. Recessive mutations in the ob gene in homozygous state cause excessive weight and diabetes in mice. Cloning and expression of cDNA of the human and mouse ob genes revealed that the ob gene is only expressed in white adipose tissue. cDNA encodes the ob protein that consists of 167 amino acid residues, the homology between the mouse and human ob proteins being 84%. The peptide leptin, secreted into blood, consists of 145 amino acid residues and results from the cleavage of a signal peptide off the ob protein. Leptin was obtained by genetic engineering methods. Its injection into ob/ob mice decreases body weight and eliminates diabetes symptoms. Leptin also decreased body weight of healthy mice by activating the utilization of endogenous lipids in energy metabolism. Leptin was found in human and mouse blood and mouse adipose tissue but not in blood or adipose tissue of ob/ob mice. Based on the results obtained, it was postulated that leptin, a product of the ob gene, is a hormone that is secreted into blood in varying quantities by adipocytes and controls the adipose tissue weight by stimulating lipid metabolism in the organism.
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PMID:[Leptin--a peptide hormone from adipocytes. Sensation of the 23rd FEBS Meeting]. 868 12

We have cloned the rhesus monkey obese cDNA and have analyzed its expression in monkeys with a wide range of body weights (lean to very obese) and with or without non-insulin-dependent diabetes mellitus to examine the relationship of ob gene expression to obesity and non-insulin-dependent diabetes mellitus. The sequence of monkey ob protein, excluding the signal peptide, showed 91% identity with the human protein. We observed a significant correlation between the level of ob mRNA and body weight. We also found a significant relationship between ob mRNA and fasting plasma insulin concentration; however, insulin stimulation during a 100-140-min euglycemic/hyperinsulinemic clamp did not result in any changes in ob mRNA levels. Circulating levels of the ob gene product leptin were also significantly correlated with body weight. These results show that ob gene expression is related to body weight and is not acutely regulated by insulin.
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PMID:Regulation of obese (ob) mRNA and plasma leptin levels in rhesus monkeys. Effects of insulin, body weight, and non-insulin-dependent diabetes mellitus. 881 Feb 96

A brief review of the studies on the obese (ob) gene is given. The ob gene is a mouse gene, the mutations of which are associated with altered metabolism and increased lipid deposits in adipose tissue. Recessive ob gene mutations in homozygous mice result in obesity and diabetes mellitus. Both mouse and human ob cDNAs were cloned and sequenced using positional cloning, exon trapping, and PCR. Of ten tested tissues, the ob gene was expressed only in white adipose tissue. The ob gene cDNA has a region of the nucleotide sequence with an opening reading frame and encodes the ob protein consisting of 167 amino acid residues. Mouse and human ob proteins showed a 85% homology. The 145-amino acid peptide termed as leptin and derived from ob protein after cleavage of signal peptide is secreted in the blood and stimulates fat consumption in energy metabolism. The biologically active ob peptide has been obtained by gene engineering methods. Administration of the ob protein to ob/ob mice reduced body weight and abolished symptoms of diabetes. The ob protein lowered body weight also in healthy animals. It was biologically effective both upon parenteral and intravenous administration and also when injected into lateral ventricle of the brain. With a polyclonal antiserum against the peptide the ob protein was shown to be present in human and mouse plasma and mouse adipose tissue. Based on the data obtained, it is postulated that the ob gene protein product leptin, is a hormone, which is secreted by adipocytes in the blood in varying amounts and regulates the mass of adipose tissue by stimulating lipid metabolism. Similarly to adipocytes, many other organs and tissues are presumably endocrine and may secrete peptide hormones in the blood. This considerably extends the scope of endocrinology and makes it necessary to review the existing concepts and views.
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PMID:[ob protein--product of expressing an obesity gene and some aspects of modern-day endocrinology]. 901 Dec 50

The ob protein, termed leptin, is produced by adipocytes and is thought to act as an afferent satiety signal regulating weight through suppressing appetite and stimulating energy expenditure in humans and/or rodents. Insulin has been found to be a potent stimulator of leptin expression in rodents. It is unclear at present whether this insulin action is a direct or an indirect effect. To investigate whether leptin concentrations in children and adolescents with type 1 diabetes (IDDM) were related to metabolic status, body weight, body mass index and insulin treatment, we have measured leptin concentrations in serum from 13 newly diagnosed IDDM patients before the beginning of insulin treatment (8 girls, 5 boys, aged 4.7-17.5 years) and in 134 patients with IDDM during treatment (64 girls, 70 boys, aged 2.6-20.1 years) using a specific radioimmunoassay. The data from patients with diabetes were compared with normative data that were derived from a large cohort of healthy children and adolescents. Serum from children with newly diagnosed diabetes had significantly lower levels of leptin (mean 1.28+/-1.60 ng/ml, range 0.14-6.13 ng/ml) compared with healthy children (n=710) (mean 2.2 ng/ml, range 0.26-14.4ng/ml) and compared with insulin-treated children and adolescents (mean 5.18+/-5.48 ng/ml, range 0.26-29.77 ng/ml) (P<0.0001) even after adjustment for gender and body mass index (BMI). Serum leptin levels in patients with IDDM were significantly correlated with BMI (r=0.42, P<0.0001). Multiple regression analysis showed that age and BMI were significantly correlated with leptin levels, while duration of diabetes, mean HbA1c levels, insulin dose and plasma glucose, triglyceride and cholesterol levels were not. Females had higher serum leptin concentrations than males even when adjusted for BMI (P<0.0001). Surprisingly and most importantly, leptin levels in insulin-treated young adult (Tanner stage 5) patients were significantly higher than values found in the healthy nondiabetic reference population when adjusted for sex, Tanner stage and BMI. These findings suggest that leptin levels in IDDM patients show a similar dependency on adipose tissue and age as in healthy, normal children. The data provide evidence that insulin may be of importance as a regulator of serum leptin levels in vivo not only in rodents but also in humans. It is hypothesized that the elevated BMI-adjusted leptin levels in adolescents with IDDM could indicate either that these patients may be oversubstituted by the intensified insulin therapy that they are receiving or that their body composition and body fat content may differ from that of healthy adolescents in the sense that they have a relative increase in fat mass.
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PMID:Serum leptin levels in children and adolescents with insulin-dependent diabetes mellitus in relation to metabolic control and body mass index. 962 60

In humans, production of the adipocyte-derived peptide leptin has been linked to adiposity, insulin, and insulin sensitivity. We therefore considered that alterations in plasma leptin concentrations could constitute an additional component of a metabolic syndrome of cardiovascular risk. To explore this hypothesis, we employed factor analysis, a multivariate statistical technique that allows reduction of large numbers of highly intercorrelated variables to composite, biologically meaningful factors. Seventy-four men [age, 48.4+/-1.3 years (mean+/-SEM); body mass index (BMI), 25.6+/-0.3 kg/m2] who were free of coronary heart disease and diabetes underwent anthropometric measurements (subscapular-to-triceps [S:T] and subscapular-to-biceps [S:B] skinfold thickness ratios, measurement of fasting plasma leptin, and an intravenous glucose tolerance test (IVGTT) for assessment of insulin sensitivity. Plasma leptin concentrations were correlated with BMI (r=0.57, P<0.001), S:T (r=0.34, P=0.003), S:B (r=0.37, P<0.001), systolic and diastolic blood pressures (both r=0.24, P=0.044), fasting triglycerides (r=0.31, P=0.007), serum uric acid (r=0.35, P=0.003), fasting glucose (r=0.32, P=0.003) and insulin (r=0.33, P=0.004), and IVGTT insulin (r=0.63, P<0.001). A negative correlation was observed between leptin and insulin sensitivity (r=-0.32, P=0.006). No significant correlations emerged between plasma leptin concentrations and age, high density lipoprotein cholesterol, or IVGTT glucose. In multivariate regression analyses, BMI (standardized coefficient [SC]=0.40, P=0.001), fasting insulin (SC=0.23, P=0.036), and IVGTT insulin (SC=0.51, P<0.001) emerged as independent predictors of plasma leptin concentrations (R2=0.56, P<0.001). After adjustment for BMI, only IVGTT insulin emerged as a significant predictor of plasma leptin concentrations (SC=0.56, P<0.001, R2=0.45, P<0.001). Factor analysis of plasma leptin concentrations and the variables that are considered relevant to the insulin resistance syndrome revealed a clustering of plasma leptin concentrations with a factor dominated by insulin resistance and high IVGTT insulin, separate from a high IVGTT glucose/central obesity factor and a high triglyceride/low high density lipoprotein cholesterol factor. Together, these factors accounted for 55.9% of the total variance in the dataset. In conclusion, interindividual variations in plasma leptin concentrations are strongly related to the principal components of the insulin resistance syndrome. Further studies are needed to determine whether the insulin-leptin axis plays a coordinating role in this syndrome and whether plasma leptin concentrations could provide an additional measure of cardiovascular risk.
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PMID:Hyperleptinemia as a component of a metabolic syndrome of cardiovascular risk. 963 33


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