Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011860 (type 2 diabetes)
 57,723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Twenty-four percent of the adult American population have the metabolic syndrome. Although somewhat counterintuitive, carefully regulated treatment with insulin has been shown to reduce insulin resistance and may also retard the development of cardiovascular disease by preventing chronic hyperglycemia, a condition that synergistically contributes to many proatherogenic pathways, including glycoxidation, the polyol pathway, advanced glycation end products, interference with normal metabolic pathways, and stimulation of protein kinase C-beta and proinflammatory pathways. This article describes some of the physiologic changes that occur when hyperglycemia and insulin resistance develop in patients with type 2 diabetes and discusses therapies, including insulin, that normalize glucose and reduce insulin resistance, thereby potentially reducing cardiovascular risk.
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PMID:Insulin therapy for reducing cardiovascular risk in patients with type 2 diabetes. 1498 5

Lectin-like oxidized LDL receptor-1 (LOX-1) is a newly identified receptor for oxidized LDL that is expressed by vascular cells. LOX-1 is upregulated in aortas of diabetic rats and thus may contribute to the pathogenesis of human diabetic atherosclerosis. In this study, we examined the regulation of human monocyte-derived macrophage (MDM) LOX-1 expression by high glucose and the role of LOX-1 in glucose-induced foam cell formation. Incubation of human MDMs with glucose (5.6 to 30 mmol/L) enhanced, in a dose- and time-dependent manner, LOX-1 gene and protein expression. Induction of LOX-1 gene expression by high glucose was abolished by antioxidants, protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), nuclear factor-kappaB (NF-kappaB), and activated protein-1 (AP-1) inhibitors. In human MDMs cultured with high glucose, increased expression of PKCbeta2 and enhanced phosphorylation of extracellular signal-regulated protein kinase 1/2 was observed. Activation of these kinases was inhibited by the antioxidant N-acetyl-L-cysteine (NAC) and by the PKCbeta inhibitor LY379196. High glucose also enhanced the binding of nuclear proteins extracted from human MDMs to the NF-kappaB and AP-1 regulatory elements of the LOX-1 gene promoter. This effect was abrogated by NAC and PKC/MAPK inhibitors. Finally, high glucose induced human macrophage-derived foam cell formation through a LOX-1-dependent pathway. Overall, these results demonstrate that high glucose concentrations enhance LOX-1 expression in human MDMs and that this effect is associated with foam cell formation. Pilot data showing that MDMs of patients with type 2 diabetes overexpress LOX-1 support the relevance of this work to human diabetic atherosclerosis.
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PMID:Glucose enhances human macrophage LOX-1 expression: role for LOX-1 in glucose-induced macrophage foam cell formation. 1500 26

Nutrient excess is associated with reduced insulin sensitivity (insulin resistance) and plays a central role in the pathogenesis of type 2 diabetes. Recently, free fatty acids as well as amino acids were shown to induce insulin resistance by decreasing glucose transport/phosphorylation with subsequent impairment of glycogen synthesis in human skeletal muscle. These results do not support the traditional concept of direct substrate competition with glucose for mitochondrial oxidation but indicate that the cellular mechanisms of such lipotoxicity and "proteotoxicity" might primarily affect the insulin signaling cascade. The signaling pathways involved in nutrient dependent modulation of insulin action include protein kinase C isoforms and IkappaB kinase. Therefore, pharmacological modulation of these enzymes might represent a promising target for future treatment of insulin resistance. Finally, hyperglycemia which occurs late in the insulin resistance syndrome further augments insulin resistance by mechanisms summarized as glucose toxicity. Chronic hyperglycemia might lead to inhibition of lipid oxidation and thereby to accumulation of intracellular lipid metabolites. Therefore, glucotoxicity might be in part indirectly caused by lipotoxicity (glucolipotoxicity). In conclusion, different nutrients affect common metabolic pathways and thereby induce insulin resistance in humans.
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PMID:Nutrient-induced insulin resistance in human skeletal muscle. 1507 72

Lipoprotein lipase (LPL) secreted by macrophages in the arterial wall promotes atherosclerosis. We have shown that macrophages of patients with type 2 diabetes overproduce LPL and that metabolic factors, including glucose, stimulate macrophage LPL secretion. In this study, we determined the effect of advanced glycation end products (AGEs) on LPL expression by macrophages cultured in a high-glucose environment and the molecular mechanisms underlying this effect. Our results demonstrate that AGEs potentiate the stimulatory effect of high glucose on murine and human macrophage LPL gene expression and secretion. Induction of macrophage LPL mRNA levels by AGEs was identical to that elicited by physiologically relevant modified albumin and was inhibited by anti-AGE receptor as well as by antioxidants. Treatment of macrophages with AGEs resulted in protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) activation. Inhibition of these kinases abolished the effect of AGEs on LPL mRNA levels. Finally, exposure of macrophages to AGEs increased the binding of nuclear proteins to the activated protein-1 consensus sequence of the LPL promoter. This effect was inhibited by PKC and MAPK inhibitors. These results demonstrate for the first time that AGEs potentiate the stimulatory effect of high glucose on macrophage LPL expression. This effect appears to involve oxidative stress and PKC/MAPK activation.
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PMID:Advanced glycation end products potentiate the stimulatory effect of glucose on macrophage lipoprotein lipase expression. 1521 Aug 47

Insulin resistance and type 2 diabetes are associated with elevated circulating levels of nonesterified FA (NEFA) and lipoprotein remnants. The dyslipidemia is an important contributor to the excess arterial disease associated with insulin resistance and type 2 diabetes, but the mechanisms involved are elusive. In the present study we examined the effect of NEFA on macrophages. For this purpose, we utilized human macrophages, prepared by treating THP-1 monocytes with phorbol ester. We found that albumin-bound NEFA at physiological levels increase the secretion of granulocyte macrophage-colony stimulating factor (GM-CSF) by the THP-1 macrophages in a dose-dependent manner. The effect was registered as an increase in mRNA, and the amount of GM-CSF secreted correlated with the accumulation of TAG and DAG in the cell. The NEFA-induced rise in GM-CSF appeared to be mediated by activation of protein kinase C, probably acting on extracellular signal-regulated kinases 1 and 2 and being calcium dependent. We speculate that increased secretion of GM-CSF by resident macrophages in the intima exposed chronically to high levels of NEFA, such as those present in insulin resistance, may contribute to a proatherogenic response of arterial cells.
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PMID:Fatty acids induce increased granulocyte macrophage-colony stimulating factor secretion through protein kinase C-activation in THP-1 macrophages. 1523 3

Skeletal muscle insulin resistance is a co-morbidity of obesity and a risk factor for the development of type 2 diabetes mellitus. Insulin resistance is associated with the accumulation of intramyocellular lipids. Intramyocellular triacylglycerols do not appear to be the cause of insulin resistance but are more likely to be a marker of other lipid intermediates such as fatty acyl-CoA, ceramides or diacylglycerols. Fatty acyl-CoA, ceramides and diacylglycerols are known to directly alter various aspects of the insulin signalling cascade. Insulin signalling is inhibited by the phosphorylation of serine and threonine residues at the levels of the insulin receptor and insulin receptor substrate 1. Protein kinase C is responsible for the phosphorylation of the serine and threonine residues. Fatty acyl-CoA and diacylglycerols are known to activate protein kinase C. The cause of the intramyocellular accumulation of fatty acyl-CoA and diacylglycerols is unclear at this time. Reduced fatty acid oxidation does not appear to be responsible, as fatty acyl-CoA accumulates in skeletal muscle with a normal fatty acid oxidative capacity. Other potential mechanisms include oversupply of lipids to muscle and/or up regulated fatty acid transport.
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PMID:The molecular mechanism linking muscle fat accumulation to insulin resistance. 1529 58

In the history of diabetes, chlorpropamide alcohol flushing test (CPAF) was a big topic in the 1970s to 1980s. Alcohol tolerance after chlorpropamide has prognostic significance, with the intolerant group (CPAF-positive group) being less prone to develop vascular complication than the tolerant group (CPAF-negative group). A mechanism of CPAF has been regarded as the inhibition of aldehyde dehydrogenase 2 (ALDH2) by an N-alkyl-substituted derivative of chlorpropamide, and the expression of these mutations of ALDH2 and alcohol dehydrogenase 2 (ADH2) could determine the alcohol tolerance among the Japanese population. Therefore, we hypothesized that expression of different ALDH2 and ADH2 polymorphisms may induce differences in vascular complications in diabetes and conducted two studies. The first study (study 1) was to determine the association of ALDH2/AHD2 polymorphism with diabetic complications. To know the association of ALDH2/AHD2 polymorphism with diabetic vasculopathy and neuropathy, a total of 158 patients with type 2 diabetes were divided into four groups on the basis of ALDH2 "activity" and ADH2 "superactivity." The frequency of proteinuria and the percentage of proliferative retinopathy among the patients with retinopathy was higher in those with active ALDH2 and superactive ADH2. We speculated that protein kinase C isoforms up-regulated by 4-hydroxynonenal that was detoxified by ALDH2 and ADH2 may account for the long-term development of diabetic nephropathy and severe retinopathy. As for neuropathy, the frequency of symptomatic neuropathy was higher in patients with inactive ALDH2 and usual ADH2. We speculate that increased tissue levels of toxic aldehyde could result from inactive ALDH2 and usual ADH2 expression, which results in the increased level of reactive aldehyde in sensory neuron pathway, thereby causing symptomatic polyneuropathy.
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PMID:ALDH2/ADH2 polymorphism associated with vasculopathy and neuropathy in type 2 diabetes. 1531 96

Insulin resistance plays a primary role in the development of type 2 diabetes and may be related to alterations in fat metabolism. Recent studies have suggested that local accumulation of fat metabolites inside skeletal muscle may activate a serine kinase cascade involving protein kinase C-theta (PKC-theta), leading to defects in insulin signaling and glucose transport in skeletal muscle. To test this hypothesis, we examined whether mice with inactivation of PKC-theta are protected from fat-induced insulin resistance in skeletal muscle. Skeletal muscle and hepatic insulin action as assessed during hyperinsulinemic-euglycemic clamps did not differ between WT and PKC-theta KO mice following saline infusion. A 5-hour lipid infusion decreased insulin-stimulated skeletal muscle glucose uptake in the WT mice that was associated with 40-50% decreases in insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and IRS-1-associated PI3K activity. In contrast, PKC-theta inactivation prevented fat-induced defects in insulin signaling and glucose transport in skeletal muscle. In conclusion, our findings demonstrate that PKC-theta is a crucial component mediating fat-induced insulin resistance in skeletal muscle and suggest that PKC-theta is a potential therapeutic target for the treatment of type 2 diabetes.
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PMID:PKC-theta knockout mice are protected from fat-induced insulin resistance. 1537 6

Sex steroid hormones are involved in the metabolism, accumulation and distribution of adipose tissues. It is now known that oestrogen receptor, progesterone receptor and androgen receptor exist in adipose tissues, so their actions could be direct. Sex steroid hormones carry out their function in adipose tissues by both genomic and nongenomic mechanisms. In the genomic mechanism, the sex steroid hormone binds to its receptor and the steroid-receptor complex regulates the transcription of given genes. Leptin and lipoprotein lipase are two key proteins in adipose tissues that are regulated by transcriptional control with sex steroid hormones. In the nongenomic mechanism, the sex steroid hormone binds to its receptor in the plasma membrane, and second messengers are formed. This involves both the cAMP cascade and the phosphoinositide cascade. Activation of the cAMP cascade by sex steroid hormones would activate hormone-sensitive lipase leading to lipolysis in adipose tissues. In the phosphoinositide cascade, diacylglycerol and inositol 1,4,5-trisphosphate are formed as second messengers ultimately causing the activation of protein kinase C. Their activation appears to be involved in the control of preadipocyte proliferation and differentiation. In the presence of sex steroid hormones, a normal distribution of body fat exists, but with a decrease in sex steroid hormones, as occurs with ageing or gonadectomy, there is a tendency to increase central obesity, a major risk for cardiovascular disease, type 2 diabetes and certain cancers. Because sex steroid hormones regulate the amount and distribution of adipose tissues, they or adipose tissue-specific selective receptor modulators might be used to ameliorate obesity. In fact, hormone replacement therapy in postmenopausal women and testosterone replacement therapy in older men appear to reduce the degree of central obesity. However, these therapies have numerous side effects limiting their use, and selective receptor modulators of sex steroid hormones are needed that are more specific for adipose tissues with fewer side effects.
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PMID:Direct effects of sex steroid hormones on adipose tissues and obesity. 1545 95

Oxidative stress is thought to be one of the causative factors contributing to insulin resistance and type 2 diabetes. Previously, we showed that reactive oxygen species (ROS) production is significantly increased in adipocytes from high-fat diet-induced obese and insulin-resistant mice (HF). ROS production was also associated with the increased activity of PKC-delta. In the present studies, we hypothesized that PKC-delta contributes to ROS generation and determined their intracellular source. NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI) reduced ROS levels by 50% in HF adipocytes, and inhibitors of NO synthase (L-NAME, 1 mM), xanthine oxidase (allopurinol, 100 microM), AGE formation (aminoguanidine, 10 microM), or the mitochondrial uncoupler (FCCP, 10 microM) had no effect. Rottlerin, a selective PKC-delta inhibitor, suppressed ROS levels by approximately 50%. However, neither GO-6976 nor LY-333531, effective inhibitors toward conventional PKC or PKC-beta, respectively, significantly altered ROS levels in HF adipocytes. Subsequently, adenoviral-mediated expression of wild-type PKC-delta or its dominant negative mutant (DN-PKC-delta) in HF adipocytes resulted in either a twofold increase in ROS levels or their suppression by 20%, respectively. In addition, both ROS levels and PKC-delta activity were sharply reduced by glucose depletion. Taken together, these results suggest that PKC-delta is responsible for elevated intracellular ROS production in HF adipocytes, and this is mediated by high glucose and NADPH oxidase.
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PMID:PKC-delta-dependent activation of oxidative stress in adipocytes of obese and insulin-resistant mice: role for NADPH oxidase. 1550 33


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