Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To determine whether defects of muscle glycogen synthase (GS) activity can be acquired by exposure to elevated glucose or insulin levels, human skeletal muscle cells obtained by needle biopsy from normal control subjects were grown in culture for 4-6 weeks followed by 4 days of fusion and differentiation in media containing either normal (5.5 mmol/l glucose and 22 pmol/l insulin) or increased concentrations of glucose (20 mmol/l), insulin (30 micromol/l), or both. After fusion in normal media, acute stimulation by 33 nmol/l insulin for 1 h increased GS fractional velocity (FV) approximately twofold (from 9.01 +/- 1.26 to 16.31 +/- 2.40, P < 0.05). Increasing the media glucose concentration alone to 20 mmol/l during fusion had no effect on basal FV but caused a marginal impairment of the insulin-stimulated GS response (from 8.51 +/- 1.33 to 12.99 +/- 1.90, P = 0.08). Increasing the media insulin concentration to 30 micromol/l during fusion at 5.5 mmol/l glucose also did not alter basal GS FV (10.61 +/- 1.69%) but completely abolished the normal insulin-stimulated increase in GS activity (to 11.63 +/- 1.55%, NS). The combination of high insulin (30 micromol/l) and high glucose (20 mmol/l) during fusion had no greater effect on the FV of either basal (11.66 +/- 2.16%, NS) or insulin-stimulated (9.20 +/- 1.80%, NS) GS activity than high insulin alone. Fusion in hyperinsulinemic media altered the kinetic parameters of GS with a near doubling of the basal Km0.1 and Vmax0.1 for uridinediphospho-glucose. Hyperinsulinemia also totally prevented the normal insulin-stimulated threefold increase in the Vmax0.1 and the 65% decrease in the A0.5 for glucose-6-phosphate. GS mRNA and protein expression, determined by RNase protection assay and immunoblotting, respectively, were unaffected by changes in media conditions. We conclude that exposure of human skeletal muscle cells primarily to high insulin induces severe insulin resistance through multiple acquired posttranslational defects, which affect both the kinetic characteristics and absolute activity of the GS enzyme.
Diabetes 1996 Apr
PMID:Acquired defects of glycogen synthase activity in cultured human skeletal muscle cells: influence of high glucose and insulin levels. 860 59

To examine whether impairment of intracellular glucose metabolism precedes insulin resistance, we determined the time courses of changes in insulin-stimulated glucose uptake, glycolysis, and glycogen synthesis during high-fat feeding in rats. Animals were fed with a high-fat (66.5%) diet ad libitum for 0, 2, 4, 7, or 14 days (n = 10-11 in each group) after 5 days of a low-fat (12.5%) diet. Submaximal and maximal insulin-stimulated glucose fluxes were estimated in whole body and individual skeletal muscles using the glucose clamp technique combined with D-[3-3H]glucose infusion and 2-[1-14C]deoxyglucose injection. Both submaximal and maximal insulin-stimulated glucose uptake in whole body decreased gradually with high-fat feeding. However, the decreases were minimal and not statistically significant during the initial few days (i.e., 2 and 4 days) of high-fat feeding (P > 0.05). In contrast, insulin-stimulated whole-body glycolysis (both maximal and submaximal) significantly decreased by approximately 30% with 2 days of high-fat feeding and remained suppressed thereafter (P < 0.05). Similar patterns of changes in insulin-stimulated glucose uptake and glycolysis were also observed in skeletal muscle. Insulin-stimulated glycogen synthesis and glucose-6-phosphate (G-6-P) concentrations in skeletal muscle increased significantly during the initial few days of high-fat feeding and gradually returned to control levels by day 14, suggesting that increased G-6-P concentrations were responsible for increased glycogen synthesis. Thus, suppression of insulin-stimulated glycolysis and a compensatory increase in glycogen synthesis (presumably arising from the glucose-fatty acid cycle) preceded decreases in insulin-stimulated glucose uptake in skeletal muscle during high-fat feeding. These findings suggest that the insulin resistance may develop as a secondary response to impaired intracellular glucose metabolism.
Diabetes 1996 May
PMID:Metabolic impairment precedes insulin resistance in skeletal muscle during high-fat feeding in rats. 862 Oct 18

After entering the muscle cell, glucose is immediately and irreversibly phosphorylated to glucose-6-phosphate by hexokinases (HK) I and II. Previous studies in rodents have shown that HKII may be the dominant HK in skeletal muscle. Reduced insulin-stimulated glucose uptake and reduced glucose-6-phosphate concentrations in muscle have been found in non-insulin-dependent diabetes mellitus (NIDDM) patients when examined during a hyperglycemic hyperinsulinemic clamp. These findings [correction of finding] are consistent with a defect in glucose transport and/or phosphorylation. In the present study comprising 29 NIDDM patients and 25 matched controls, we tested the hypothesis that HKII activity and gene expression are impaired in vastus lateralis muscle of NIDDM patients when examined in the fasting state. HKII activity in a supernatant of muscle extract accounted for 28 +/- 5% in NIDDM patients and 40 +/- 5% in controls (P = 0.08) of total muscle HK activity when measured at a glucose media of 0.11 mmol/liter and 31 +/- 4 and 47 +/- 7% (P = 0.02) when measured at 0.11 mmol/liter of glucose. HKII mRNA, HKII immunoreactive protein level, and HKII activity were significantly decreased in NIDDM patients (P < 0.0001, P = 0.03, and P = 0.02, respectively) together with significantly decreased glycogen synthase mRNA level and total glycogen synthase activity (P = 0.02 and P = 0.02, respectively). In the entire study population HKII activity estimated at 0.11 and 11.0 mM glucose was inversely correlated with fasting plasma glucose concentrations (r = -0.45, P = 0.004; r = -0.54, P < 0.0001, respectively) and fasting plasma nonesterified fatty acid concentrations (r = -0.46, P = 0.003; r = -0.37, P = 0.02, respectively). In conclusion, NIDDM patients are characterized by a reduced activity and a reduced gene expression of HKII in muscle which may be secondary to the metabolic peturbations. HKII contributes with about one-third of total HK activity in a supernatant of human vastus lateralis muscle.
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PMID:Impaired activity and gene expression of hexokinase II in muscle from non-insulin-dependent diabetes mellitus patients. 867 29

To determine whether glycogen synthase (GS) activity remains impaired in skeletal muscle of non-insulin-dependent diabetes mellitus (NIDDM) patients or can be normalized after prolonged culture, needle biopsies of vastus lateralis were obtained from 8 healthy nondiabetic control (ND) and 11 NIDDM subjects. After 4-6 wk growth and 4 d fusion in media containing normal physiologic concentrations of insulin (22 pM) and glucose (5.5 mM), both basal (5.21 +/- 0.79 vs 9.01 +/- 1.25%, P < 0.05) and acute insulin-stimulated (9.35 +/- 1.81 vs 16.31 +/- 2.39, P < 0.05) GS fractional velocity were reduced in NIDDM compared to ND cells. Determination of GS kinetic constants from muscle cells of NIDDM revealed an increased basal and insulin-stimulated Km(0.1) for UDP-glucose, a decreased insulin-stimulated Vmax(0.1) and an increased insulin-stimulated activation constant (A(0.5)) for glucose-6-phosphate. GS protein expression, determined by Western blotting, was decreased in NIDDM compared to ND cells (1.57 +/- 0.29 vs 3.30 +/- 0.41 arbitrary U/mg protein, P < 0.05). GS mRNA abundance also tended to be lower, but not significantly so (0.168 +/- 0.017 vs 0.243 +/- 0.035 arbitrary U, P = 0.08), in myotubes of NIDDM subjects. These results indicate that skeletal muscle cells of NIDDM subjects grown and fused in normal culture conditions retain defects of basal and insulin-stimulated GS activity that involve altered kinetic behavior and possibly reduced GS protein expression. We conclude that impaired regulation of skeletal muscle GS in NIDDM patients is not completely reversible in normal culture conditions and involves mechanisms that may be genetic in origin.
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PMID:Glycogen synthase activity is reduced in cultured skeletal muscle cells of non-insulin-dependent diabetes mellitus subjects. Biochemical and molecular mechanisms. 878 86

We investigated whether low density lipoprotein (LDL) under oxidative stress might induce the release of fructose, glucose-6-phosphate and fructose-6-phosphate from perivascular cells, and also whether these substances might accelerate the formation of advanced glycation end products (AGE) from proteins in vitro. When vascular smooth muscle cells were incubated with LDL in Ham's F10 at 37 degrees C for 48 h. release of all these substances was increased dose-dependently by oxidized LDL. Fructose release was increased in a dose-dependent manner by glucose. Indomethacin (20 microM) significantly (P < 0.01) suppressed the release of fructose (25.4 +/- 15.7% of control) and hexose phosphates (29.4 +/- 4.0) with the inhibition of release of lactate dehydrogenase (35.5 +/- 4.9) as well as probucol, whereas an aldose reductase inhibitor, epalrestat, significantly (P < 0.001) inhibited only the fructose release (0.9 +/- 0.8). Release of fructose and hexose phosphates from vascular endothelial cells was also induced by oxidized LDL. AGE immunoreactivities and AGE-related fluorescence formed from proteins and glucose were significantly increased (P < 0.001) in the presence of small amounts of the cellular glucose metabolites (6.6%) with glucose (93.4%). These data suggest that release of potent AGE initiators, fructose and hexose phosphates, from perivascular cells induced by oxidized LDL may be an important phenomenon for vascular complications.
Diabetes Res Clin Pract 1996 Mar
PMID:Release of fructose and hexose phosphates from perivascular cells induced by low density lipoprotein and acceleration of protein glycation in vitro. 879 96

Although the kinetic characteristics of hepatic glucokinase (GK) suggest its potential role as the hepatic "glucose sensor," its impact on the regulation of in vivo hepatic glucose production (HGP) is still controversial. Since decreased GK activity has been linked to experimental and human diabetes, we examined whether a moderate and transient inhibition of GK activity diminishes the ability of hyperglycemia to suppress HGP. We first determined the concentration of the competitive inhibitor, glucosamine (GlcN), which decreases hepatic GK activity by approximately 60% in vitro. GlcN was then infused into conscious rats to achieve a similar inhibition of the in vivo GK activity (plasma GlcN levels = approximately 2 mmol/l; rats infused with saline served as control, n = 20). To maintain equal plasma insulin and glucagon concentrations throughout the studies, somatostatin and insulin (basal replacement) were infused for 4 h. [3-(3H)]-glucose and [U-(14C)]-lactate were infused to measure HGP, gluconeogenesis, and glucose cycling (GC) during 2 h of euglycemia (glucose approximately 8 mmol/l) followed by 2 h of hyperglycemia (glucose approximately 18 mmol/l). Our results support the notion that hepatic GK activity is indeed decreased by GlcN in vivo. In fact, in response to hyperglycemia the "direct" pathway of hepatic glucose-6-phosphate (G-6-P) formation was approximately 40% lower with GlcN compared with saline infusion (37 +/- 3 vs. 63 +/- 3%; P < 0.001). Furthermore, while hyperglycemia stimulated GC by approximately 2.5-fold during saline infusion (from 3.0 +/- 0.6 to 7.7 +/- 1.4 mg.kg-1.min-1, P < 0.001, euglycemia vs. hyperglycemia), this increase was blunted in the presence of GlcN (4.6 +/- 0.6 mg.kg-1.min-1, P = NS). Finally, in the presence of GlcN, the hepatic concentration of G-6-P was decreased by approximately 40% compared with saline (234 +/- 38 and 390 +/- 24 nmol/g, P < 0.01). During the euglycemic studies, HGP was similar (12.6 +/- 0.6 and 11.3 +/- 0.2 mg .kg-1.min-1 with GlcN or saline infusion, respectively). However, while hyperglycemia per se suppressed HGP by approximately 65%, HGP was inhibited by approximately 38% and it was approximately twofold higher than in the saline-infused rats (7.8 +/- 0.8 and 4.0 +/- 0.3 mg.kg-1.min-1, P < 0.01) in the presence of GlcN-induced inhibition of hepatic GK. This increase in HGP was largely accounted for by the decreased inhibition of hepatic net glycogenolysis by hyperglycemia (3.3 +/- 0.8 and 1.1 +/- 0.3 mg.kg-1.min-1 with GlcN or saline infusion, respectively, P < 0.01). We conclude that intact GK activity is required for the normal suppression of HGP by hyperglycemia and its impairment may contribute to increased HGP in experimental and human diabetes.
Diabetes 1996 Oct
PMID:Glucosamine-induced inhibition of liver glucokinase impairs the ability of hyperglycemia to suppress endogenous glucose production. 882 67

Glycation of proteins of the vessel wall is thought to play an important role in the pathogenesis of vascular complications in diabetes by affecting structure and function of these proteins. Adhesive proteins in the extracellular matrix (ECM) of endothelial cells (ECs) are essential for attachment of ECs to the subintima. In this study, we investigated the effect of glycation of ECM and purified adhesive proteins on EC adhesion and spreading. ECM was incubated with the reactive sugar glucose-6-phosphate (0-500 mmol/l) for different time periods (0-14 days) at 37 degrees C. Degree of glycation, measured in an enzyme-linked immunosorbent assay using a monoclonal antibody specific for advanced glycation end products, increased in a time- and concentration-dependent manner. Glycation of ECM with 50 mmol/l glucose-6-phosphate resulted in increased coverage by ECs as measured in a cell adhesion assay and was the result of an increase in number of adhered cells, while cell size was unaffected. Glycation of ECM with higher concentrations of glucose-6-phosphate resulted in decreased coverage by ECs caused by both a reduction in number of adhered ECs and impaired spreading. Experiments with purified glycated matrix proteins indicate that the decrease in EC adhesion and spreading on glycated ECM may result from glycation of vitronectin. Impaired EC adhesion and spreading caused by vitronectin glycation may result in impaired endothelial function and contribute to vascular disease.
Diabetes 1997 Jan
PMID:Effect of extracellular matrix glycation on endothelial cell adhesion and spreading: involvement of vitronectin. 897 Oct 87

To determine the mechanism of impaired insulin-stimulated muscle glycogen metabolism in patients with poorly controlled insulin-dependent diabetes mellitus (IDDM), we used 13C-NMR spectroscopy to monitor the peak intensity of the C1 resonance of the glucosyl units in muscle glycogen during a 6-h hyperglycemic-hyperinsulinemic clamp using [1-(13)C]glucose-enriched infusate followed by nonenriched glucose. Under similar steady state (t = 3-6 h) plasma glucose (approximately 9.0 mM) and insulin concentrations (approximately 400 pM), nonoxidative glucose metabolism was significantly less in the IDDM subjects compared with age-weight-matched control subjects (37+/-6 vs. 73+/-11 micromol/kg of body wt per minute, P < 0.05), which could be attributed to an approximately 45% reduction in the net rate of muscle glycogen synthesis in the IDDM subjects compared with the control subjects (108+/-16 vs. 195+/-6 micromol/liter of muscle per minute, P < 0.001). Muscle glycogen turnover in the IDDM subjects was significantly less than that of the controls (16+/-4 vs. 33+/-5%, P < 0.05), indicating that a marked reduction in flux through glycogen synthase was responsible for the reduced rate of net glycogen synthesis in the IDDM subjects. 31P-NMR spectroscopy was used to determine the intramuscular concentration of glucose-6-phosphate (G-6-P) under the same hyperglycemic-hyperinsulinemic conditions. Basal G-6-P concentration was similar between the two groups (approximately 0.10 mmol/kg of muscle) but the increment in G-6-P concentration in response to the glucose-insulin infusion was approximately 50% less in the IDDM subjects compared with the control subjects (0.07+/-0.02 vs. 0.13+/-0.02 mmol/kg of muscle, P < 0.05). When nonoxidative glucose metabolic rates in the control subjects were matched to the IDDM subjects, the increment in the G-6-P concentration (0.06+/-0.02 mmol/kg of muscle) was no different than that in the IDDM subjects. Together, these data indicate that defective glucose transport/phosphorylation is the major factor responsible for the lower rate of muscle glycogen synthesis in the poorly controlled insulin-dependent diabetic subjects.
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PMID:Mechanism of impaired insulin-stimulated muscle glucose metabolism in subjects with insulin-dependent diabetes mellitus. 915 94

Human skeletal muscle cultures (HSMCs) from type II diabetic subjects were used to determine whether metabolic abnormalities such as hyperglycemia or hyperinsulinemia contribute to the defective muscle glycogen synthase (GS) activity present in this disorder. Following approximately 6 weeks of growth, diabetic cultures were fused for 4 days in normal, hyperglycemia, or hyperinsulinemia medium. Fusion of diabetic HSMCs in hyperglycemia medium (20 mmol/l vs. 5.5 mmol/l) had no effect on GS fractional velocity (FV) or mRNA levels, but impaired acute insulin-stimulation of glycogen synthesis and GS activity at 0.1 mmol/l glucose-6-phosphate, and reduced GS protein content by approximately 15% (P < 0.05). Fusion of diabetic muscle cultures in hyperinsulinemia medium (30 micromol/l vs. 22 pmol/l) improved basal GS activity, increasing the reduced GS FV by approximately 50% (P < 0.05), and decreasing the elevated Km(0.1) (half-maximal substrate concentration) by approximately 47% (P < 0.05). Hyperinsulinemia also significantly increased (P < 0.05) the reduced GS mRNA and protein levels of diabetic muscle to levels similar to that in nondiabetic subjects. In contrast to the improvements in the basal state, hyperinsulinemia completely abolished acute insulin responsiveness of GS activity and glycogen synthesis in muscle of type II diabetic subjects. The combination of hyperinsulinemia and hyperglycemia produced effects on both basal and insulin-responsive GS FV and mRNA similar to hyperinsulinemia alone, but hyperinsulinemia prevented hyperglycemia's effect of lowering GS protein and glycogen synthesis. We concluded that, in diabetic muscle, hyperinsulinemia may serve to partially compensate for the impaired basal GS activity and for the adverse effects of hyperglycemia on GS protein content, activity, and glycogen formation by both pre- and posttranslational mechanisms. Despite these beneficial effects, hyperinsulinemia also induces severe impairment of insulin-stimulated GS activity and glycogen formation, which may contribute to acquired muscle insulin resistance of type II diabetes.
Diabetes 1997 Jun
PMID:Regulation of glycogen synthase activity in cultured skeletal muscle cells from subjects with type II diabetes: role of chronic hyperinsulinemia and hyperglycemia. 916 74

Mannose is an aldohexose component of a number of glycoproteins in cellular membranes and blood plasma. Free (unbound) mannose is a normal blood plasma constituent and its concentration is elevated in diabetes mellitus and chronic glomerulonephritis. We devised an enzymatic method for the determination of free mannose in which mannose is converted to glucose-6-phosphate and measured spectrophotometrically using glucose-6-phosphate dehydrogenase and nicotinamide adenine dinucleotide phosphate (NADP). Accumulation of reduced NADP in the assay was verified by spectral analysis and by finding rapid disappearance of absorbance at 340 nm on addition of glutathione reductase and oxidized glutathione into the reaction mixture. The method necessitates prior removal of glucose from the samples. This we accomplished using glucose-6-phosphate dehydrogenase and a surplus amount of NADP, followed by elimination of reduced NADP by acidification of the reaction mixture. The assays may be run in parallel for expediency. Concentration of free mannose in serum was 18.5 +/- 5.5 mumol/l in healthy fasting female adults. The analytical recovery was 90.2 +/- 10.2% and the between-run imprecision was 13.5% (18.5 +/- 5.5 mumol/l, mean +/- SD) and 10.4% (75.3 +/- 10.3 mumol/l). The assay showed rectilinearity up to 220 mumol/l, which covers the measuring range to which the mannose concentrations in normal and clinical samples may be expected to fall.
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PMID:Enzymatic determination of unbound D-mannose in serum. 936 94


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