Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P42345 (mTOR)
 26,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To examine the molecular mechanisms by which plasma amino acid elevation impairs insulin action, we studied seven healthy men twice in random order during infusion of an amino acid mixture or saline (total plasma amino acid approximately 6 vs. approximately 2 mmol/l). Somatostatin-insulin-glucose clamps created conditions of low peripheral hyperinsulinemia ( approximately 100 pmol/l, 0-180 min) and prandial-like peripheral hyperinsulinemia ( approximately 430 pmol/l, 180-360 min). At low peripheral hyperinsulinemia, endogenous glucose production (EGP) did not change during amino acid infusion but decreased by approximately 70% during saline infusion (EGP(150-180 min) 11 +/- 1 vs. 3 +/- 1 mumol . kg(-1) . min(-1), P = 0.001). Prandial-like peripheral hyperinsulinemia completely suppressed EGP during both protocols, whereas whole-body rate of glucose disappearance (R(d)) was approximately 33% lower during amino acid infusion (R(d) (330-360 min) 50 +/- 4 vs. 75 +/- 6 mumol . kg(-1) . min(-1), P = 0.002) indicating insulin resistance. In skeletal muscle biopsies taken before and after prandial-like peripheral hyperinsulinemia, plasma amino acid elevation markedly increased the ability of insulin to activate S6 kinase 1 compared with saline infusion ( approximately 3.7- vs. approximately 1.9-fold over baseline). Furthermore, amino acid infusion increased the inhibitory insulin receptor substrate-1 phosphorylation at Ser312 and Ser636/639 and decreased insulin-induced phosphoinositide 3-kinase activity. However, plasma amino acid elevation failed to reduce insulin-induced Akt/protein kinase B and glycogen synthase kinase 3alpha phosphorylation. In conclusion, amino acids impair 1) insulin-mediated suppression of glucose production and 2) insulin-stimulated glucose disposal in skeletal muscle. Our results suggest that overactivation of the mammalian target of rapamycin/S6 kinase 1 pathway and inhibitory serine phosphorylation of insulin receptor substrate-1 underlie the impairment of insulin action in amino acid-infused humans.
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PMID:Overactivation of S6 kinase 1 as a cause of human insulin resistance during increased amino acid availability. 1612 57

Neuroendocrine tumours of the gastroenteropancreatic axis include carcinoid tumours and islet cell tumours of the pancreas (pancreatic endocrine tumours). Standard medical therapies prescribed for these malignancies include long-acting somatostatin analogues (octreotide and lanreotide) for the palliation of hormonal syndromes; cytotoxic agents (streptozocin, dacarbazine, adriamycin and 5-fluorouracil), which are primarily for the management of advanced islet cell tumours; and hepatic artery embolisation or chemoembolisation for the treatment of liver metastases. Clinical research promises to expand this therapeutic armamentarium. Most of the experimental treatments that are being evaluated in human clinical trials fall into the following categories: angiogenesis inhibitors, novel somatostatin analogues, radiolabelled somatostatin analogues, mTOR inhibitors and novel cytotoxic agents. This review summarises the present scope of clinical research in this field.
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PMID:A review of the current clinical trials for gastroenteropancreatic neuroendocrine tumours. 1724 41

The nutrient-sensitive kinase mammalian target of rapamycin (mTOR) and its downstream target S6 kinase (S6K) are involved in amino acid-induced insulin resistance. Whether the mTOR/S6K pathway directly modulates glucose metabolism in humans is unknown. We studied 11 healthy men (29 years old, BMI 23 kg/m(2)) twice in random order after oral administration of 6 mg rapamycin, a specific mTOR inhibitor, or placebo. An amino acid mixture was infused to activate mTOR, and somatostatin-insulin-glucose clamps created conditions of low peripheral hyperinsulinemia (approximately 100 pmol/l, 0-180 min) and prandial-like peripheral hyperinsulinemia (approximately 450 pmol/l, 180-360 min). Glucose turnover was assessed using d-[6,6-(2)H(2)]glucose infusion (n = 8). Skeletal muscle biopsies were performed at baseline and during prandial-like peripheral hyperinsulinemia (n = 3). At low peripheral hyperinsulinemia, whole-body glucose uptake was not affected by rapamycin. During prandial-like peripheral hyperinsulinemia, rapamycin increased glucose uptake compared with placebo by 17% (R(d 300-360 min), 75 +/- 5 vs. 64 +/- 5 micromol x kg(-1) x min(-1), P = 0.0008). Rapamycin affected endogenous glucose production neither at baseline nor during low or prandial-like peripheral hyperinsulinemia. Combined hyperaminoacidemia and prandial-like hyperinsulinemia increased S6K phosphorylation and inhibitory insulin receptor substrate-1 (IRS-1) phosphorylation at Ser312 and Ser636 in the placebo group. Rapamycin partially inhibited this increase in mTOR-mediated S6K phosphorylation and IRS-1 Ser312 and Ser636 phosphorylation. In conclusion, rapamycin stimulates insulin-mediated glucose uptake in man under conditions known to activate the mTOR/S6K pathway.
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PMID:The Mammalian target of rapamycin pathway regulates nutrient-sensitive glucose uptake in man. 1732 20

Carcinoid and islet-cell carcinoma are often also known as low-grade neuroendocrine carcinomas. They are often slow-growing but can be resistant to standard therapy. While somatostatin analogues are often used to control hormonal syndromes, there is currently no therapy approved in the US for control of carcinoid tumor growth. For islet-cell carcinoma, streptozocin-based chemotherapy may induce tumor shrinkage, but second-line option are limited. This chapter reviews the molecular biology of neuroendocrine tumors, including the roles of MENIN, TSC2, NF-1, vHL, p53, bcl-2, bax, VEGF, IGF, PDGF, EGFR, and mTOR. Recently, there has been interest in developing molecularly targeted therapy for this group of diseases. Phase-II studies with imatinib, bevacizumab, sunitinib, gefitnib, temsirolimus, and everolimus (RAD001) have completed accrual. Encouraging results have been observed in studies with VEGF and mTOR inhibitors. Phase-III study of bevacizumab is planned in the US. Large-scale multinational phase-II and -III studies of everolimus are under way.
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PMID:Neuroendocrine tumors. Molecular targeted therapy for carcinoid and islet-cell carcinoma. 1738 71

Diagnosis and treatment of autosomal dominant polycystic kidney disease (ADPKD) is rapidly changing. Cellular pathways that involve the polycystins are being mapped and involve the primary cilium, intracellular calcium and cAMP regulation, and the mammalian target of rapamycin (mTOR) pathway. With the use of new imaging approaches, earlier diagnosis of hepatic cystic disease is possible, and measurement of kidney and cystic growth as well as kidney blood flow is possible over relatively short periods. PKD gene type, gender, proteinuria, and the presence of hypertension relate to the rate of kidney growth in ADPKD. On the basis of risk factors for progression to ESRD and the pathogenic roles that intracellular cAMP and mTOR play in cystogenesis, novel therapies are now being tested, including maximal inhibition of the renin-angiotensin system, inhibition of renal intracellular cAMP using vasopressin V2 receptor antagonists, and somatostatin analogues, as well as inhibitors of mTOR. This review addresses the current understanding of the pathogenesis and the natural history of ADPKD; accuracy and reliability of diagnostic approaches in utero, childhood, and adulthood; the value of reliable magnetic resonance imaging to measure disease progression early in the course of ADPKD; and novel therapeutic approaches that are being evaluated in ADPKD.
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PMID:Autosomal dominant polycystic kidney disease: time for a change? 1742 47

Patients with metastatic gastrointestinal neuroendocrine tumors have traditionally been faced with few effective treatment options. Somatostatin analogs often successfully control symptoms of hormonal hypersecretion but seldom result in tumor regression. Some patients with hepatic metastases are also candidates for ablative therapies such as surgical debulking or embolization. The role of systemic agents such as interferon alfa or cytotoxic chemotherapy remains ill defined. The more prevalent use of these modalities has been restricted by low tumor response rates and the potential for toxicity. Novel agents, including radiolabeled somatostatin analogs, inhibitors of the vascular endothelial growth factor pathway, and inhibitors of mammalian target of rapamycin, have shown promising activity in recent clinical studies. Continued investigation of these agents should render a better understanding of their efficacy in patients with advanced neuroendocrine tumors.
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PMID:New developments in the treatment of gastrointestinal neuroendocrine tumors. 1743 Jun 88

Skeletal muscle protein synthesis is elevated in neonates in part due to an enhanced response to the rise in insulin and amino acids after eating. In vitro studies suggest that glucose plays a role in protein synthesis regulation. To determine whether glucose, independently of insulin and amino acids, is involved in the postprandial rise in skeletal muscle protein synthesis, pancreatic-substrate clamps were performed in neonatal pigs. Insulin secretion was inhibited with somatostatin and insulin was infused to reproduce fasting or fed levels, while glucose and amino acids were clamped at fasting or fed levels. Fractional protein synthesis rates and translational control mechanisms were examined. Raising glucose alone increased protein synthesis in fast-twitch glycolytic muscles but not in other tissues. The response in muscle was associated with increased phosphorylation of protein kinase B (PKB) and enhanced formation of the active eIF4E.eIF4G complex but no change in phosphorylation of AMP-activated protein kinase (AMPK), tuberous sclerosis complex 2 (TSC2), mammalian target of rapamycin (mTOR), 4E-binding protein-1 (4E-BP1), ribosomal protein S6 kinase (S6K1), or eukaryotic elongation factor 2 (eEF2). Raising glucose, insulin, and amino acids increased protein synthesis in most tissues. The response in muscle was associated with phosphorylation of PKB, mTOR, S6K1, and 4E-BP1 and enhanced eIF4E.eIF4G formation. The results suggest that the postprandial rise in glucose, independently of insulin and amino acids, stimulates protein synthesis in neonates, and this response is specific to fast-twitch glycolytic muscle and occurs by AMPK- and mTOR-independent pathways.
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PMID:Glucose stimulates protein synthesis in skeletal muscle of neonatal pigs through an AMPK- and mTOR-independent process. 1755 Oct 2

Patients with neuroendocrine tumors may pursue a number of treatment options, but there is little consensus on a single, standard treatment approach. Somatostatin analogs are generally administered to patients with symptoms of hormonal secretion, and are often highly effective in this regard. However, the administration of somatostatin analogs is only rarely associated with tumor regression, and randomized trials demonstrating a survival benefit associated with their use have not been performed. Selected patients with hepatic metastases may undergo surgical debulking, embolization or other ablative therapies. The clinical benefit associated with administration of systemic agents such as IFN-alpha or cytotoxic chemotherapy has been limited. With the possible exception of streptozocin-based therapy in patients with pancreatic neuroendocrine tumors, the widespread use of standard cytotoxic regimens has been limited by their relatively modest antitumor activity, as well as concerns regarding their potential toxicity. The modest efficacy seen with these agents in patients with advanced neuroendocrine tumors has led to great interest in the development of novel treatment approaches. One such approach is the use of radiolabeled somatostatin analogs. Recently, agents targeting the VEGF pathway and mammalian target of rapamycin have also shown promise in patients with advanced neuroendocrine tumors. Ongoing randomized studies should help better define the role these agents will play in the future treatment of patients with this disease.
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PMID:Emerging therapies for the treatment of patients with advanced neuroendocrine tumors. 1760

Traditional therapies have offered patients with advanced gastrointestinal neuroendocrine tumors limited benefit. Selected patients with hepatic metastases may benefit from surgical debulking, embolization, or other ablative therapies. While somatostatin analogs are highly effective in controlling symptoms of hormonal secretion, they are only rarely associated with tumor regression. The clinical benefit associated with the administration of systemic agents such as interferon-alpha or cytotoxic chemotherapy is less clear, and the widespread use of such regimens has been limited by their relatively modest anti-tumor activity, as well as concerns regarding their potential toxicity. The mixed clinical results seen with these agents in neuroendocrine tumors have led to great interest in the development of novel treatment approaches for patients with advanced disease. Recent clinical studies of novel agents, particularly those targeting the vascular endothelial growth factor pathway and mammalian target of rapamycin, have demonstrated promising activity in patients with advanced neuroendocrine tumors. Ongoing randomized studies should help better define the role these and other targeted agents will play in the future treatment of patients with this disease.
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PMID:Gastrointestinal neuroendocrine tumors: a role for targeted therapies? 1763 38

Polycystic kidney diseases (autosomal dominant and autosomal recessive) are progressive renal tubular cystic diseases, which are characterised by cyst expansion and loss of normal kidney structure and function. Autosomal dominant polycystic kidney disease (ADPKD) is the most common life- threatening, hereditary disease. ADPKD is more prevalent than Huntington's disease, haemophilia, sickle cell disease, cystic fibrosis, myotonic dystrophy and Down's syndrome combined. Early diagnosis and treatment of hypertension with inhibitors of the renin-angiotensin-aldosterone system (RAAS) and its potential protective effect on left ventricular hypertrophy has been one of the major therapeutic goals to decrease cardiac complications and contribute to improved prognosis of the disease. Advances in the understanding of the genetics, molecular biology and pathophysiology of the disease are likely to facilitate the improvement of treatments for these diseases. Developments in describing the role of intracellular calcium ([Ca(2+)](i)) and its correlation with cellular signalling systems, Ras/Raf/mitogen extracellular kinase (MEK)/extracellular signal-regulated protein kinase (ERK), and interaction of these pathways with cyclic adenosine monophosphate (cAMP) levels, provide new insights on treatment strategies. Blocking the vasopressin V(2) receptor, a major adenylyl cyclase agonist, demonstrated significant improvements in inhibiting cytogenesis in animal models. Because of activation of the mammalian target of rapamycin (mTOR) pathway, the use of sirolimus (rapamycin) an mTOR inhibitor, markedly reduced cyst formation and decreased polycystic kidney size in several animal models. Caspase inhibitors have been shown to decrease cytogenesis and renal failure in rats with cystic disease. Cystic fluid secretion results in cyst enlargement and somatostatin analogues have been shown to decrease renal cyst progression in patients with ADPKD. The safety and efficacy of these classes of drugs provide potential interventions for experimental and clinical trials.
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PMID:Potential pharmacological interventions in polycystic kidney disease. 1803 88


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