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Insulin

About: Insulin is a research topic. Over the lifetime, 124295 publications have been published within this topic receiving 5129734 citations. The topic is also known as: human insulin.


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Journal ArticleDOI
TL;DR: The data show that ghrelin is not critically required for viability, fertility, growth, appetite, bone density, and fat deposition and not likely to be a direct regulator of leptin and insulin, and antagonists of gh Relin are unlikely to have broad utility as antiobesity agents.
Abstract: Pharmacological studies show that ghrelin stimulates growth hormone release, appetite, and fat deposition, but ghrelin's physiological role in energy homeostasis has not been established Ghrelin was also proposed to regulate leptin and insulin release and to be important for the normal function of stomach, heart, kidney, lung, testis, and placenta To help determine a definable physiological role for ghrelin, we generated ghrelin-null mice In contrast to predictions made from the pharmacology of ghrelin, ghrelin-null mice are not anorexic dwarfs; their size, growth rate, food intake, body composition, reproduction, gross behavior, and tissue pathology are indistinguishable from wild-type littermates Fasting produces identical decreases in serum leptin and insulin in null and wild-type mice Ghrelin-null mice display normal responses to starvation and diet-induced obesity As in wild-type mice, the administration of exogenous ghrelin stimulates appetite in null mice Our data show that ghrelin is not critically required for viability, fertility, growth, appetite, bone density, and fat deposition and not likely to be a direct regulator of leptin and insulin Therefore, antagonists of ghrelin are unlikely to have broad utility as antiobesity agents

642 citations

Journal ArticleDOI
TL;DR: Characterizes the abnormalities in insulin and IGF gene expression and receptor binding in brains with different Braak stage severities of AD and provides further evidence that AD represents a neuro-endocrine disorder that resembles a unique form of diabetes mellitus and progresses with severity of neurodegeneration.
Abstract: Reduced glucose utilization and energy metabolism occur early in the course of Alzheimer's disease (AD) and correlate with impaired cognition. Glucose utilization and energy metabolism are regulated by insulin and insulin-like growth factor I (IGF-I), and correspondingly, studies have shown that cognitive impairment may be improved by glucose or insulin administration. Recently, we demonstrated significantly reduced levels of insulin and IGF-I polypeptide genes and their corresponding receptors in advanced AD relative to aged control brains. The abnormalities in gene expression were accompanied by impaired survival signaling downstream through PI3 kinase-Akt. The present work characterizes the abnormalities in insulin and IGF gene expression and receptor binding in brains with different Braak stage severities of AD. Realtime quantitative RT-PCR analysis of frontal lobe tissue demonstrated that increasing AD Braak Stage was associated with progressively reduced levels of mRNA corresponding to insulin, IGF-I, and IGF-II polypeptides and their receptors, tau, which is regulated by insulin and IGF-I, and the Hu D neuronal RNA binding protein. In contrast, progressively increased levels of amyloid beta protein precursor (AbetaPP), glial fibrillary acidic protein, and the IBA1/AIF1 microglial mRNA transcripts were detected with increasing AD Braak Stage. Impairments in growth factor and growth factor receptor expression and function were associated with increasing AD Braak stage dependent reductions in insulin, IGF-I, and IGF-II receptor binding, ATP levels, and choline acetyltransferase (ChAT) expression. Further studies demonstrated that: 1) ChAT expression increases with insulin or IGF-I stimulation; 2) ChAT is expressed in insulin and IGF-I receptor-positive cortical neurons; and 3) ChAT co-localization in insulin or IGF-I receptor-positive neurons is reduced in AD. Together, these data provide further evidence that AD represents a neuro-endocrine disorder that resembles a unique form of diabetes mellitus (? Type 3) and progresses with severity of neurodegeneration.

642 citations

Journal ArticleDOI
TL;DR: Structural predictions and likely C-peptide cleavage sites typical of mammalian insulins suggest thatins-1 is most closely related to insulin, and overexpression of ins-1 causes partially penetrant arrest at the dauer stage and enhances dauer arrest in weak daf-2 mutants, suggesting that INS-1 and human insulin antagonize DAF-2 insulin-like signaling.
Abstract: The activity of the DAF-2 insulin-like receptor is required for Caenorhabditis elegans reproductive growth and normal adult life span. Informatic analysis identified 37 C. elegans genes predicted to encode insulin-like peptides. Many of these genes are divergent insulin superfamily members, and many are clustered, indicating recent diversification of the family. The ins genes are primarily expressed in neurons, including sensory neurons, a subset of which are required for reproductive development. Structural predictions and likely C-peptide cleavage sites typical of mammalian insulins suggest that ins-1 is most closely related to insulin. Overexpression of ins-1, or expression of human insulin under the control of ins-1 regulatory sequences, causes partially penetrant arrest at the dauer stage and enhances dauer arrest in weak daf-2 mutants, suggesting that INS-1 and human insulin antagonize DAF-2 insulin-like signaling. A deletion of the ins-1 coding region does not enhance or suppress dauer arrest, indicating a functional redundancy among the 37 ins genes. Of five other ins genes tested, the only other one bearing a predicted C peptide also antagonizes daf-2 signaling, whereas four ins genes without a C peptide do not, indicating functional diversity within the ins family.

642 citations

Journal ArticleDOI
14 Nov 1985-Nature
TL;DR: Ppl85 is maximal within seconds after exposure of the cells to insulin and exhibits a dose–response curve similar to that of receptor autophosphorylation, suggesting that this protein represents the endogenous substrate for the insulin receptor kinase.
Abstract: Phosphotyrosine-containing proteins are minor components of normal cells which appear to be associated primarily with the regulation of cellular metabolism and growth. The insulin receptor is a tyrosine-specific protein kinase, and one of the earliest detectable responses to insulin binding is activation of this kinase and autophosphorylation of its beta-subunit. Tyrosine autophosphorylation activates the phosphotransferase in the beta-subunit and increases its reactivity toward tyrosine phosphorylation of other substrates. When incubated in vitro with [gamma-32P]ATP and insulin, the purified insulin receptor phosphorylates various proteins on their tyrosine residues. However, so far no proteins other than the insulin receptor have been identified as undergoing tyrosine phosphorylation in response to insulin in an intact cell. Here, using anti-phosphotyrosine antibodies, we have identified a novel phosphotyrosine-containing protein of relative molecular mass (Mr) 185,000 (pp185) which appears during the initial response of hepatoma cells to insulin binding. In contrast to the insulin receptor, pp185 does not adhere to wheat-germ agglutininagarose or bind to anti-insulin receptor antibodies. Phosphorylation of pp185 is maximal within seconds after exposure of the cells to insulin and exhibits a dose-response curve similar to that of receptor autophosphorylation, suggesting that this protein represents the endogenous substrate for the insulin receptor kinase.

641 citations

Journal ArticleDOI
TL;DR: It is demonstrated that GRP78 inhibits both insulin-dependent and ER stress-dependent SREBP-1c proteolytic cleavage and explain the role of ER stress in hepatic steatosis in obese rodents.
Abstract: Hepatic steatosis is present in insulin-resistant obese rodents and is concomitant with active lipogenesis. Hepatic lipogenesis depends on the insulin-induced activation of the transcription factor SREBP-1c. Despite prevailing insulin resistance, SREBP-1c is activated in the livers of genetically and diet-induced obese rodents. Recent studies have reported the presence of an ER stress response in the livers of obese ob/ob mice. To assess whether ER stress promotes SREBP-1c activation and thus contributes to lipogenesis, we overexpressed the chaperone glucose-regulated protein 78 (GRP78) in the livers of ob/ob mice using an adenoviral vector. GRP78 overexpression reduced ER stress markers and inhibited SREBP-1c cleavage and the expression of SREBP-1c and SREBP-2 target genes. Furthermore, hepatic triglyceride and cholesterol contents were reduced, and insulin sensitivity improved, in GRP78-injected mice. These metabolic improvements were likely mediated by restoration of IRS-2 expression and tyrosine phosphorylation. Interestingly, GRP78 overexpression also inhibited insulin-induced SREBP-1c cleavage in cultured primary hepatocytes. These findings demonstrate that GRP78 inhibits both insulin-dependent and ER stress–dependent SREBP-1c proteolytic cleavage and explain the role of ER stress in hepatic steatosis in obese rodents.

641 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20243
20232,520
20225,252
20213,164
20203,368
20193,376