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

Glomerular basement membrane (GBM) and tubular basement membrane (TBM) were prepared from human kidneys of diabetics and non-diabetics, and their chemical composition was compared. GBM from diabetics contained a larger amount of hydroxyproline than that from non-diabetics, and smaller amounts of half-cystine, glucose, mannose and sialic acid. On the other hand, TBM from diabetics contained larger amounts of hydroxylysine, methionine, galactose, hexosamine and phospholipid phosphorus than non-diabetics, and smaller amounts of half-cystine, valine, leucine, lysine and histidine. No significant difference was observed in the contents of other components examined in this study between the corresponding membrane obtained from diabetics and non-diabetics. The observed changes may be due to alteration of the tissues in diabetes mellitus.
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PMID:Comparison of the chemical composition of glomerular and tubular basement membranes obtained from human kidneys of diabetics and non-diabetics. 113 45

Current evidence indicates that a hydroxylysine-rich glycoprotein may be of importance in the structural organization and accumulation of glomerular basement membrane in the diabetic state. To further evaluate the role of insulin deficiency in renal glycoprotein synthesis, the effect of experimental diabetes on the incorporation and hydroxylation of 14C-lysine by cell-free systems prepared from rat renal cortex was examined. Microsomal protein synthesis was increased in diabetic preparations, but the rise in renal cortical collagen synthesis relative to total protein synthesis was greater. These changes were not duplicated by the addition of a mixture of unlabeled amino acids or hydroxylation cofactors to incubations with preparations from normal animals.
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PMID:The effect of diabetes on renal lysine utilization. 115 Jan 33

Incorporation of radiolabeled precursors into muscle proteins was studied in isolated rat hemidiaphragms. A mixture of three branched-chain amino acids (0.3 mM each) added to media containing glucose stimulated the incorporation of [14C]lysine into proteins. When tested separately, valine was ineffective, isoleucine was inhibitory, but 0.5 mM leucine increased the specific activity of muscle proteins during incubation with [14C]lysine or [14C]acetate in hemidiaphragms from fed or fasted rats incubated with or without insulin. Preincubation with 0.5 mM leucine increased the specific activity of muscle proteins during a subsequent 30- or 60-min incubation with [14C]lysine or [14C]pyruvate without leucine. Preincubation with other amino acids (glutamate, histidine, methionine, phenylalanine, or tryptophan) did not exert this effect. When hemidiaphragms were incubated with a mixture of amino acids at concentrations found in rat serum and a [14C]lysine tracer, the specific activity of muscle proteins increased when leucine in the medium was raised from 0.1 to 0.5 mM. Experiments with actinomycin D and cycloheximide suggested that neither RNA synthesis nor protein synthesis are required for the initiation of the leucine effect. Leucine was not effective when added after 1 h preincubation without leucine. The concentration of lysine in the tissue water of diaphragms decreased during incubation with 0.5 mM leucine in the presence or absence of cycloheximide, suggesting that leucine inhibited protein degradation. During incubation with [3h]tyrosine (0.35 mM) the addition of 0.5 mM leucine increased the specific activity of muscle proteins, while the specific activity of intracellular tyrosine remained constant and its concentration decreased, suggesting that leucine also promoted protein synthesis. The concentration of leucine in muscle cells or a compartment thereof may play a role in regulating the turnover of muscle proteins and influence the transition to negative nitrogen balance during fasting, uncontrolled diabetes, and the posttraumatic state. Leucine may play a pivotal role in the protein-sparing effect of amino aicds.
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PMID:Leucine. A possible regulator of protein turnover in muscle. 123 98

Although L-carnitine is not considered as an essential nutrient, endogenous synthesis may fail to ensure adequate L-carnitine levels in neonates, especially those born prematurely. Free L-carnitine is found in many foods, mainly those from animal sources. Absorption of free L-carnitine is virtually complete. Lysine and methionine are necessary ingredients for the biosynthesis of L-carnitine. All tissues in the body can produce deoxy-carnitine but, in humans, the enzyme that enables hydroxylation of deoxy-carnitine to carnitine is found only in the liver, brain and kidneys. Complex exchanges of carnitine and its precursors occur between tissues. Muscles take up carnitine from the bloodstream and contain most of the body carnitine stores. L-carnitine and L-carnitine esters are eliminated mainly through the kidneys, which may play a central role in the homeostasis of this compound. Thyroid hormones adrenocorticotrophin (ACTH), and diet all influence urinary excretion of L-carnitine. Free L-carnitine can be assayed in plasma and urine and is occasionally measured in muscle biopsy specimens. Plasma L-carnitine levels may not accurately reflect L-carnitine body stores. L-carnitine ensures transfer of fatty acids to the mitochondria where they undergo oxidation. This process is associated with production of short-chain acylcarnitine which exit from the mitochondria or peroxisomes. L-carnitine ensures regeneration of coenzyme A and is thus involved in energy metabolism. L-carnitine also ensures elimination of xenobiotic substances. Carnitine deficiencies are common. Currently, these deficiencies are classified into two groups. In deficiencies with myopathy, only the muscles are deficient in L-carnitine, perhaps as a result of a primary anomaly of the L-carnitine transport system in muscles. In systemic deficiencies, L-carnitine levels are low in the plasma and in all body tissues. Systemic L-carnitine deficiencies are usually the result of a variety of disease states including deficient intake in premature infants or long-term parenteral nutrition; renal failure; organic acidemias; and Reye's syndrome. Modifications in L-carnitine metabolism have also been reported in patients with diabetes mellitus, malignancies, myocardial ischemia, and alcohol abuse. A large number of supplementation trials have been carried out.
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PMID:[L-carnitine: metabolism, functions and value in pathology]. 129 65

The effect of physiologic concentrations of inorganic phosphate (Pi) on fructosamine (FRA) synthesis was studied. After 75 g oral glucose administration (OGTT), 'delta FRA/24 h', defined as delta FRA after incubating serum or other specimens at 37 degrees C for 24 h after adding 1000 mg/dl glucose, was significantly decreased in parallel to the decrease of plasma Pi concentrations. 'The FRA index', defined as the FRA value divided by the corresponding glucose concentration, both at fasting, correlated significantly with plasma Pi concentrations. In vitro incubation of serum total protein (TP), albumin (ALB), gamma-globulin (GLB), free lysine (Lys), and free valine (Val) with glucose at different concentrations of Pi showed a Pi-dependent increase of FRA synthesis throughout 48 h of incubation. The accelerating effect of 5 mg/dl Pi on FRA synthesis from TP, ALB, GLB, Lys, and Val at pH 7.4 was, respectively, as great as 48, 20, 24, 13 or 25% of those without Pi. Increase of pH from 6 to 10 logarithmically increased delta FRA/24 h in contrast to a logarithmic decrease of the accelerating effect of Pi on delta FRA/24 h. These data show that physiologic concentrations of Pi accelerate protein glycation by accelerating dehydrogenation during the Amadori rearrangement through the negative charge of Pi. Because this accelerating effect of physiologic Pi presumably exists in vivo, Pi concentration must be taken into account as an accelerating factor for FRA synthesis in evaluating diabetic control, and further studies must be carried out to elucidate whether hyperphosphatemia accelerates glycation-induced diabetic complications.
Diabetes Res Clin Pract 1992 Jul
PMID:Physiologic concentrations of inorganic phosphate accelerate fructosamine synthesis. 151 64

We have recently examined the exons encoding the insulin receptor tyrosine kinase domain and GLUT 4 in 30 subjects with Type 2 (non-insulin-dependent) diabetes mellitus using a molecular scanning approach. The variant sequences Val-Met985 and Lys-Glu1068 of the insulin receptor and Val-Ile383 of GLUT 4 were each separately found in three different diabetic subjects. In a study of a Welsh population, the GLUT 4(383) variant was found in three of 160 diabetic and none of the 80 control subjects. In this study, the same group of Welsh Type 2 diabetic and control subjects was analysed using allele-specific oligonucleotide hybridisation, single nucleotide primer extension and allele-specific restriction digestion to ascertain the frequency of the two insulin receptor mutations. The Val-Met985 mutation was found in none of the 160 Welsh Caucasian Type 2 diabetic subjects and two of 80 control subjects. The Lys-Glu1068 mutation removes a Sty 1 site and digestion of amplified exon 18 with Sty 1 confirmed the presence of the mutation in the heterozygous state in the original subject. None of the Welsh diabetic or control subjects had the Glu1068 mutation. The discovery of a very common silent polymorphism at codon 130 of GLUT 4 allowed examination of the association of this locus with Type 2 diabetes using allele-specific oligonucleotide hybridisation in a subset of the Welsh subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Insulin receptor and insulin-responsive glucose transporter (GLUT 4) mutations and polymorphisms in a Welsh type 2 (non-insulin-dependent) diabetic population. 152 31

The role of oxygen in chemical modification and cross-linking of rat tail collagen by glucose was studied at physiological pH and temperature in vitro. Cross-linking of collagen under air depended on glucose concentration, but was inhibited under antioxidative conditions (nitrogen atmosphere with transition metal chelators). The cross-linking reaction under air depended on phosphate buffer concentration, but this effect was eliminated by addition of chelators, identifying trace metal ions in the buffer as catalysts of oxidative cross-linking reaction. Antioxidative conditions had no effect on glycation, that is, formation of fructose lysine, but inhibited formation of the glycoxidation products N epsilon-(carboxymethyl)lysine and pentosidine as well as the development of fluorescence in glycated collagen. Glycation itself decreased during continued incubation of the collagen without glucose; however, cross-linking and concentrations of glycoxidation products and fluorescence in collagen were not reversible under either oxidative or antioxidative conditions. These observations are consistent with recent studies in vivo on the reversibility of collagen glycation, the irreversibility of formation of glycoxidation products and fluorescence, and the strong correlations between glycoxidation products and fluorescence in collagen (1). These results indicate that oxidation reactions play a critical role in the extended chemical modification and cross-linking of collagen by glucose and suggest that measurement of glycoxidation products should be useful for assessing cumulative chemical modification of collagen by glucose in vivo.
Diabetes 1992 Oct
PMID:Role of oxygen in cross-linking and chemical modification of collagen by glucose. 152 35

We measured net uptake and release of amino acids in the brain of 7 nondiabetic and six diabetic subjects. Duration of insulin-dependent diabetes (IDDM) was 19.4 +/- 2.1 years. Arteriojugular vein measurements were performed before and after 120 minutes of insulin infusion and ensuing Biostator-regulated normoglycemia. Cerebral blood flow was measured during normoglycemia by 11-CH3-F and positron emission tomography. During hyperglycemia in the IDDM subjects, arterial concentrations of valine and leucine were higher, and those of glutamic acid and arginine lower, than in nondiabetic subjects. Insulin infusion lowered levels of most amino acids in both groups. Insulin treatment did not significantly affect the uptake or release of amino acids. Significant net uptake of branched-chain amino acids was noted in both groups, as well as uptake of lysine and phenylalanine in the IDDM subjects. The sum of measured differences was not different from zero in either group. Nitrogen balance depended on impressive release of glutamine from the brain (-963 +/- 147 and -960 +/- 303 nmol/100 g/min), which amounted to 73% and 69% of net release in nondiabetic and IDDM subjects, respectively. We conclude that balance between uptake and release of amino acids is similar in nondiabetic and in long-term IDDM subjects.
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PMID:Brain uptake and release of amino acids in nondiabetic and insulin-dependent diabetic subjects: important role of glutamine release for nitrogen balance. 153 41

The effects of bound fatty acids and nonenzymatic glycosylation (NEG) on tryptophan binding to human serum albumin (HSA) were examined utilizing a rate of dialysis technique. HSA with 0, 1, 2, 3, or 5 mol of palmitate bound per mol of HSA was glycosylated in vitro to a level exceeding that seen in diabetes. NEG was not inhibited by fatty acids, suggesting that Lys-525, the primary site for NEG, is not an essential component of the principal sites for long-chain fatty acid binding to HSA. Scatchard analysis of binding data showed an expected fatty acid dependent decrease in the number of available tryptophan binding sites, but showed that fatty acids did not affect tryptophan affinity. The binding data failed to show an effect of NEG on tryptophan binding. The lack of inhibition of tryptophan binding by NEG suggests that drug-binding Site II, the indole/benzodiazepine site, is resistant to both NEG and to any conformational changes in HSA which may occur with NEG. These data suggest that elevated plasma free tryptophan and the resulting altered serotonin metabolism seen in diabetes are independent of increased NEG and likely result from diabetic hyperlipidemia.
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PMID:Effects of nonenzymatic glycosylation and fatty acids on tryptophan binding to human serum albumin. 157 75

It has been proposed that the cytokine interleukin-1 beta (IL-1 beta), secreted by islet-infiltrating macrophages, may be involved in the pathogenesis of insulin-dependent diabetes mellitus by participation in beta-cell destruction. Addition of IL-1 beta to isolated pancreatic islets in vitro results in cytotoxic effects on beta-cell function, but there is little information on the intracellular events that convey the actions of the cytokine. In the present study, fetal rat pancreatic islets containing a high fraction of beta-cells were exposed in culture to IL-1 beta. It was found that IL-1 beta markedly decreased beta-cell DNA synthesis, insulin secretion and cyclic AMP content. In order to explore whether the decrease in cAMP resulted from IL-1 beta interaction with GTP-binding proteins coupled to adenylyl cyclase, islets were treated for 24 h with pertussis toxin prior to addition of cytokine. While this treatment restored the decrease in cAMP, the reduced DNA synthesis and insulin secretion persisted. Pertussis toxin treatment without the addition of IL-1 beta resulted in increases in cAMP, DNA synthesis and insulin secretion. Addition of the stimulatory cAMP analog Sp-cAMPS also increase DNA synthesis and insulin secretion, but failed to affect the decrease in these functions evoked by IL-1 beta. The protease inhibitor N alpha-p-tosyl-L-lysine chloromethyl ketone, recently shown to protect completely against IL-1 beta-induced suppression of insulin production and secretion, was found to markedly reduce DNA synthesis without affecting insulin secretion. When the protease inhibitor was combined with IL-1 beta, the suppressed secretion was counteracted while DNA synthesis inhibition was not. It is concluded that cAMP stimulates DNA synthesis and insulin secretion in beta-cells, but that the inhibitory effect of IL-1 beta on these functions cannot be ascribed to the decrease in cAMP evoked by the cytokine. However, the repressive effect of the cytokine on insulin secretion, but not DNA synthesis, may be prevented by protease inhibition.
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PMID:Inhibition of fetal rat pancreatic beta-cell replication by interleukin-1 beta in vitro is not mediated through pertussis toxin-sensitive G-proteins, a decrease in cyclic AMP, or protease activation. 165 27


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