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

Noninsulin-dependent diabetes mellitus (NIDDM), a major health care problem in the Western world, is a disease typified by a relative deficiency of insulin, leading to vast derangements in glucose and lipid homeostasis with disastrous vascular complications. Despite immense research efforts aimed at a clear understanding of the etiology of this complex disease, the molecular mechanisms causing the disorder still remain elusive. This article reviews extant data from recent publications implicating novel signal transduction pathways as important regulators of the insulin stimulus-secretion coupling in the pancreatic beta-cell. The significance of nitric oxide and serine/threonine protein phosphatases, and their inactivation by insulin secretagogues, glucose metabolites, ATP, GTP, glutamate, and inositol hexaphosphate in this arena is scrutinized. Additionally, also presented is the growing concept that an important signal for insulin secretion may reside in the inextricable interplay between glucose and lipid metabolism, specifically the generation of malonyl-CoA, which inhibits carnitine palmitoyltransferase 1 with the attendant accumulation of long-chain acyl CoA esters. Moreover, attention is directed towards novel intracellular actions of hypoglycemic sulfonylureas in the beta-cell. Finally, the importance of "lipotoxicity" and aberrations in glucose uptake and metabolism in beta-cell dysfunction is given consideration. Future research efforts should aim at further characterization of effects of second messengers on protein phosphorylation elements in beta-cells. Additionally, long-term regulation by glucose and the diabetic state (e.g., fatty acids and ketones) on beta-cell protein phosphatases, pyruvate dehydrogenase, and carnitine palmitoyltransferase 1 needs to be explored in greater depth. Clearly, the detrimental impact of diabetic hyperlipidemia on beta-cell function has been a relatively neglected area, but futu re pharmacological approaches directed at preventing lipotoxicity may prove beneficial in the treatment of diabetes.
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PMID:Aspects of novel sites of regulation of the insulin stimulus-secretion coupling in normal and diabetic pancreatic islets. 979 25

To examine the effects of safflower oil versus fish oil feeding on in vivo intramuscular glucose metabolism and relative pyruvate dehydrogenase (PDH) versus tricarboxylic acid (TCA) cycle flux, rats were pair-fed on diets consisting of 1) 59% safflower oil, 2) 59% menhaden fish oil, or 3) 59% carbohydrate (control) in calories. Rates of glycolysis and glycogen synthesis were assessed by monitoring [1-(13)C]glucose label incorporation into [1-(13)C]glycogen, [3-(13)C]lactate, and [3-(13)C]alanine in the hindlimb of awake rats via 13C nuclear magnetic resonance (NMR) spectroscopy during a euglycemic (approximately 6 mmol/l) hyperinsulinemic (approximately 180 microU/ml) clamp. A steady-state isotopic analysis of lactate, alanine, and glutamate was used to determine the relative PDH versus TCA cycle flux present in muscle under these conditions. The safflower oil-fed rats were insulin resistant compared with control and fish oil-fed rats, as reflected by a markedly reduced glucose infusion rate (Ginf) during the clamp (21.4 +/- 2.3 vs. 31.6 +/- 2.8 and 31.7 +/- 1.9 mg x kg(-1) x min(-1) in safflower oil versus control and fish oil groups, respectively, P < 0.006). This decrease in insulin-stimulated glucose disposal in the safflower oil group was associated with a lower rate of glycolysis (21.7 +/- 2.2 nmol x g(-1) x min(-1)) versus control (62.1 +/- 10.3 nmol x g(-1) x min(-1), P < 0.001) and versus fish oil (45.7 +/- 6.7 nmol x g(-1) x min(-1), P < 0.04), as no change in glycogen synthesis (103 +/- 15, 133 +/- 19, and 125 +/- 14 nmol x g(-1) x min(-1) in safflower oil, fish oil, and control, respectively) was detected. The intramuscular triglyceride (TG) content was increased in the safflower oil group (7.3 +/- 0.8 micromol/g) compared with the control group (5.2 +/- 0.8 micromol/g, P < 0.05) and the fish oil group (3.6 +/- 1.1 micromol/g, P < 0.01). Conversely, the percent PDH versus TCA cycle flux was decreased in the safflower oil (43 +/- 8%) versus the control (73 +/- 8%, P < 0.01) and fish oil (64 +/- 6%, P < 0.05) groups. These data suggest that the reduced insulin-stimulated glucose disposal attributed to safflower oil feeding was a consequence of reduced glycolytic flux associated with an increase in relative free fatty acid/ketone oxidation versus TCA cycle flux, whereas fish oil feeding did not alter glucose metabolism and may in part be protective of insulin-stimulated glucose disposal by limiting intramuscular TG deposition.
Diabetes 1999 Jan
PMID:Differential effects of safflower oil versus fish oil feeding on insulin-stimulated glycogen synthesis, glycolysis, and pyruvate dehydrogenase flux in skeletal muscle: a 13C nuclear magnetic resonance study. 989 34

1) The earliest electroretinographic manifestation of diabetic retina is a selective change in the oscillatory potential (OP), which originates in postsynaptic retinal neuronal circuits. "Diabetic intraretinal neuropathy" precedes angiopathic retinopathy. 2) The peak latency and the amplitude of the OP are significantly correlated with the psychophysical contrast threshold for motion perception (CTMP) measured with our original device. 3) The CTMP is not correlated with the conventional static contrast threshold measured with a commercially available chart (VCTS-6000). 4) The CTMP is beyond the upper limit in nondiabetic control eyes in 135 out of 162 diabetic eyes at stage 0 (no ophthalmoscopic diabetic retinopathy) and all retinopathic eyes at stages AI (11 eyes) and AII (21 eyes). The CTMP test, which is completely non-invasive and easy to perform, could be useful for mass-screening of early diabetic retinal dysfuction. 5) The amplitude of the OP is enhanced by dopamine and nomifensine (a potent dopamine-uptake blocker), and diminished by haloperidol (a potent antagonist to dopamine D1-D2 receptors). Intrinsic dopamine release in the retina would regulate the amplitude of the OP. 6) The intraretinal content of dopamine decreases in streptozotocin (STZ)-induced diabetic rats where the OP amplitude is diminished, and increases in eyes where the OP amplitude is enhanced at the early stage in spontaneously diabetic (OLETF) rats. The changes in the OP amplitude in STZ-induced and OLETF diabetic rats can not be accounted for by the intraretinal content of gamma-aminobutyric acid (GABA), glycine, glutamate, aspartate or taurine. The changes in the OP amplitude in the diabetic retina are at least partly due to dysfunction of dopaminergic retinal neurons. 7) The peak latency prolongation and the amplitude diminution of the OP in STZ-induced diabetic rats are normalized after insulin treatment, while vitreous fluorescein concentration by vitreous fluorophotometry is not restored by insulin. Thus, the OP changes in STZ-induced diabetic rats are not due to STZ toxicity but to diabetes per se, and are not attributable to blood-ocular barrier disruption as revealed by vitreous fluorophotometry. Retinal neuronal dysfunction revealed by the OP changes at the early preretinopathic stage in STZ-induced diabetic rats is reversible after insulin treatment. 8) The OP changes in OLETF rats are prevented by decreasing food intake by 30% to maintain their blood glucose level and body weight normal. Even in highly genetically diabetic animals, diet therapy starting at an early stage of life inhibits the diabetic OP changes. 9) The amplitude of the bicarbonate response from the retinal pigment epithelium diminishes even at the preretinopathic stage, and is significanly correlated with the peak latency and the amplitude of the OP. Diabetic retinal pigment epitheliopathy as well as retinal neuropathy takes place prior to angiopathic retinopathy in the diabetic retina.
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PMID:[Preretinopathic changes in the oscillatory potential in diabetic retina: interpretation and significance]. 1002 14

Leukocyte 12-lipoxygenase (12-LO) gene expression in pancreatic beta cells is upregulated by cytotoxic cytokines like IL-1beta. Recent studies have demonstrated that 12-LO inhibitors can prevent glutamate-induced neuronal cell death when intracellular glutathione stores are depleted. Therefore, 12-LO pathway inhibition may prevent beta-cell cytotoxicity. To evaluate the role of 12-LO gene expression in immune-mediated islet destruction, we used 12-LO knockout (12-LO KO) mice. Male homozygous 12-LO KO mice and control C57BL/6 mice received 5 consecutive daily injections of low-dose streptozotocin to induce immune-mediated diabetes. Fasting serum glucose and insulin levels were measured at 7-day intervals, and the mice were followed up for 28 days. 12-LO KO mice were highly resistant to diabetes development compared with control mice and had higher serum insulin levels on day 28. Isolated pancreatic islets were treated with IL-1beta, TNF-alpha, and IFN-gamma for 18 hours. Glucose-stimulated insulin secretion in cytokine-treated islets from C57/BL6 mice decreased 54% from that of untreated islets. In marked contrast, the same cytokine mix led to only a 26% decrease in islets from 12-LO KO mice. Furthermore, cytokine-induced 12-hydroxyeicosatetraenoic acid (12-HETE) production was absent in 12-LO KO islets but present in C57/BL6 islets. Isolated peritoneal macrophages were stimulated for 48 hours with IFN-gamma + LPS and compared for nitrate/nitrite generation. 12-LO KO macrophages generated 50% less nitrate/nitrite when compared with C57BL/6 macrophages. In summary, elimination of leukocyte 12-LO in mice ameliorates low dose streptozotocin-induced diabetes by increasing islet resistance to cytokines and decreasing macrophage production of nitric oxide.
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PMID:Resistance to type 1 diabetes induction in 12-lipoxygenase knockout mice. 1033 Apr 25

To better define the modifications of liver gluconeogenesis and citric acid cycle, or Krebs' cycle, activity induced by insulin deficiency and the effects of metformin on these abnormalities, we infused livers isolated from postabsorptive or starved normal and streptozotocin-induced diabetic rats with pyruvate and lactate (labeled with [3-13C]lactate) with or without the simultaneous infusion of metformin. Lactate and pyruvate uptake and glucose production were calculated. The 13C-labeling pattern of liver glutamate was used to calculate, according to Magnusson's model, the relative fluxes through Krebs' cycle and gluconeogenesis. These relative fluxes were converted into absolute values using substrate balances. In normal rats, starvation increased gluconeogenesis, the flux through pyruvate carboxylase-phosphoenolpyruvate carboxykinase (PC-PEPCK), and the ratio of PC to pyruvate dehydrogenase (PDH) flux (P < 0.05); metformin induced only a moderate decrease in the PC:PDH ratio. Livers from postabsorptive diabetic rats had increased lactate and pyruvate uptakes (P < 0.05); their metabolic fluxes resembled those of starved control livers, with increased gluconeogenesis and flux through PC-PEPCK. Starvation induced no further modifications in the diabetic group. Metformin decreased glucose output from the liver of starved diabetic rats (P < 0.05). The flux through PC-PEPCK and also pyruvate kinase were decreased (P < 0.05) by metformin in both groups of diabetic rats. In conclusion, insulin deficiency increased in this model of diabetes gluconeogenesis through enhanced uptake of substrate and increased flux through PC-PEPCK; metformin decreased glucose production by reducing the flux through PC-PEPCK.
Diabetes 1999 Jun
PMID:Modifications of citric acid cycle activity and gluconeogenesis in streptozotocin-induced diabetes and effects of metformin. 1034 12

The glutamatergic synapse is the key structure in the development of activity-dependent synaptic plasticity in the central nervous system. The analysis of the complex biochemical mechanisms at the basis of the long-term changes in synaptic efficacy have received a tremendous impulse by the observation that the post-synaptic constituents of the synapse can be separated and purified through a simple procedure involving detergent treatment of synaptosomes and differential centrifugation. In this fraction, called post-synaptic density (PSD), the functional interactions of its constituents are preserved. The various subunits of ionotropic glutamate receptors are held in register with the presynaptic active zone through their interaction with linker proteins. N-methyl-D-aspartate (NMDA) subunits NR2A and NR2B, bind to the PSD protein called PSD-95, which in turn binds neuroligins, providing a handle for interacting with neurexin, located in the plasma membrane at the presynaptic active zone. Additional clustering of NMDA receptors is provided through the binding of NRI subunits to the cytoskeletal protein alpha-actinin-2. AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and kainate receptors are other important constituents of PSDs and bind to different anchoring proteins. Phosphorylation processes have long been known to modulate NMDA receptor functional activity: the finding that several protein kinases, particularly Ca2+/Calmodulin-dependent protein kinase II and protein tyrosine kinases of the src family, are major constituents of PSDs has allowed to demonstrate that these enzymes are localized in a strategic position of the glutamatergic synapse, so that their activation provides a means for NMDA receptor function regulation upon its activation. The relevance of these mechanisms has been demonstrated in experimental models of pathologies involving deficits in synaptic plasticity, such as in streptozotocin-induced diabetes and in an animal model of prenatal induced ablation of hippocampal neurons. Both animal models display disturbances in long-term potentiation and cognitive deficits, thus providing in vivo models to study pathology related changes in both the structure and the function of the excitatory synapse.
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PMID:Pathophysiological implications of the structural organization of the excitatory synapse. 1044 87

The aim of this study was to investigate the effect of increasing exogenous palmitate concentration on carbohydrate and palmitate oxidation in hearts from control and 1-wk diabetic rats. Hearts were perfused with glucose, [3-(13)C]lactate, and [U-(13)C]palmitate. Substrate oxidation rates were determined by combining (13)C-NMR glutamate isotopomer analysis of tissue extracts with measurements of oxygen consumption. Carbohydrate oxidation was markedly depressed after diabetes in the presence of low (0.1 mM) but not high (1.0 mM) palmitate concentration. Increasing exogenous palmitate concentration 10-fold resulted in a 7-fold increase in the contribution of palmitate to energy production in controls but only a 30% increase in the diabetic group. Consequently, at 0.1 mM palmitate, the rate of fatty acid oxidation was higher in the diabetic group than in controls; however, at 1.0 mM fatty acid oxidation, it was significantly depressed. Therefore, after 1 wk of diabetes, the major differences in carbohydrate and fatty acid metabolism occur primarily at low rather than high exogenous palmitate concentration.
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PMID:Impact of 1 wk of diabetes on the regulation of myocardial carbohydrate and fatty acid oxidation. 1044 31

The entrainment function in the suprachiasmatic nucleus (SCN) of young non-diabetic Otsuka Long Evans Tokushima Fatty (OLETF) rats was studied. OLETF rats significantly needed more days for re-entrainment to a new light-dark cycle than control Long Evans Tokushima Otsuka (LETO) rats. We also assessed Fos expression in the SCN induced by dim light exposure. The number of Fos-immunoreactive cells was significantly decreased in 5- to 13-week-old OLETF rats compared with LETO rats. Moreover, the effect of glutamate on neuronal activity in the SCN of OLETF rats were investigated. In young non-diabetic OLETF rats, the phase delay in the SCN neuronal firing rhythm induced by 1 microM glutamate was significantly less than that in LETO rats. These results suggested that the entrainment function is reduced in OLETF rats before the onset of diabetes.
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PMID:Lowered entrainment function in the suprachiasmatic nucleus of Otsuka Long Evans Tokushima Fatty (OLETF) rats. 1044 61

Antioxidant enzyme activities in rat liver and forebrain and the effect of the MK-801 administration on these activities were estimated on 6th day of alloxan-induced diabetes. The catalase, superoxide dismutase, glutathione reductase, and glutathione peroxidase activities of cytosolic fractions from both liver and forebrain were shown to decrease significantly in prediabetic rats, and these alterations were virtually prevented by the course of MK-801 administration. The results suggest that the suppression of antioxidant enzymes can be the primary biochemical disturbance in diabetes progression and that glutamate NMDA receptors can be involved in the molecular mechanism underlying this condition.
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PMID:[Activity of antioxidant enzymes in liver and brain is decreased in the early stage of diabetes, and this decrease depends on the function of NMDA-receptors]. 1054 79

This paper provides an overview of our current understanding of the role of sigma-receptors in the regulation of cough, gastrointestinal and retinal function. Systemic administration of N-(+)-allylnormetazocine ((+)SKF-10,047), 1,2-di-(2-toyl)guanidine (DTG) or pentazocine markedly reduced the number of coughs in a dose-dependent manner. The antitussive effect of these sigma-receptor ligands was significantly reduced by pretreatment with haloperidol or rimcazol, a specific antagonist of sigma-receptors. Antitussive effects of dextromethorphan and noscapine were significantly and dose-dependently reduced by pretreatment with rimcazole. However, rimcazole did not have a significant effect on the antitussive effect of morphine. These results suggest that haloperidol-sensitive sigma-receptors may be involved in the antitussive mechanism of non-narcotic antitussive drugs. Selective sigma-receptor ligands such as (+)SKF-10,047, DTG and (+)pentazocine elicit a potent protection against gastric and duodenal ulcers. Ulcerprotective activity of sigma-receptor ligands may be related to their stimulating effect on bicarbonate secretion through interaction with sigma-receptors in the gastrointestinal mucosa. Activation of sigma-receptors in retina protect retinal cells against glutamate-induced neurotoxicity. It is possible that sigma-receptor ligands may be useful as therapeutic drugs against retinal disease with ischemia-induced neuronal cell death such as retinal artery occlusion, diabetes mellitus or glaucoma.
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PMID:[Possible role of sigma-receptors in the regulation of cough reflex, gastrointestinal and retinal function]. 1056 63


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