Lysosomal dysfunction induced by changes in albumin's tertiary structure: Potential key factor in protein toxicity during diabetic nephropathy.

Aims: Increased amounts of protein, in particular albumin within renal tubular cells (TBCs), induce the expression of inflammatory and fibrogenic mediators, which are adverse prognostic factors in tubulointerstitial fibrosis and diabetic nephropathy (DN). We sought to assess the participation of the thiol-linked tertiary structure of albumin in the mechanism of protein toxicity in a model of TBCs.

Materials And Methods: Cultured human renal proximal tubular cells, HK-2, were exposed to isolated albumin from patients with and without DN (Stages 0, 1 and 4).

In vitro retention efficiency of temporary type zinc oxide cement for orthodontic forced eruption.

Objective: To assess the retention efficiency of three types of temporary zinc oxide cement trademarks on forced eruption using intracranal wire device.

Methods: An in vitro evaluation included intracanal wire device displacement and detachment at 50g load force for 120 days and then the retention resistance at maximum load force.

Results: All groups of temporary zinc oxide cements were efficient to support 50g load forces after 120 days.

Nicotinamide prevents sweet beverage-induced hepatic steatosis in rats by regulating the G6PD, NADPH/NADP and GSH/GSSG ratios and reducing oxidative and inflammatory stress.

The disruption of redox state homeostasis, the overexpression of lipogenic transcription factors and enzymes, and the increase in lipogenic precursors induced by sweetened beverages are determinants of the development of nonalcoholic fatty liver disease. This study evaluated the action of nicotinamide (NAM) on the expression of glucose-6-phosphate dehydrogenase (G6PD) and redox, oxidative, and inflammatory states in a model of nonalcoholic hepatic steatosis induced by high and chronic consumption of carbohydrates. Male rats were provided drinking water with 30% glucose or fructose ad libitum for 12 weeks.

Antioxidant capacity and structural changes of human serum albumin from patients in advanced stages of diabetic nephropathy and the effect of the dialysis.

Changes in the antioxidant capacity of albumin and alterations of the albumin structural conformation were examined in patients in advanced stages of diabetes nephropathy. Human serum albumin was purified from diabetic patients in pre-dialysis (glomerular filtration rate [GFR] between 15 and 29 ml min(-1) 1.73 m(-2)) and those in dialysis (GFR ≤ 15 ml min(-1) 1.

Albumin antioxidant response to stress in diabetic nephropathy progression.

Background: A new component of the protein antioxidant capacity, designated Response Surplus (RS), was recently described. A major feature of this component is the close relationship between protein antioxidant capacity and molecular structure. Oxidative stress is associated with renal dysfunction in patients with renal failure, and plasma albumin is the target of massive oxidation in nephrotic syndrome and diabetic nephropathy.

Nicotinamide, a glucose-6-phosphate dehydrogenase non-competitive mixed inhibitor, modifies redox balance and lipid accumulation in 3T3-L1 cells.

Aims: Excessive energy uptake of dietary carbohydrates results in their storage as fat and requires glucose-6-phosphate dehydrogenase (G6PD)-mediated NADPH production. We sought to assess whether the nicotinamide-induced reduction of G6PD activity might modulate redox balance and lipid accumulation in 3T3-L1 cells.

Main Methods: 3T3-L1 preadipocytes (days 4 and 6 of differentiation) and adipocytes were cultured in the presence of 5 or 25 mM glucose.

Protein conjugated with aldehydes derived from lipid peroxidation as an independent parameter of the carbonyl stress in the kidney damage.

Background: One of the well-defined and characterized protein modifications usually produced by oxidation is carbonylation, an irreversible non-enzymatic modification of proteins. However, carbonyl groups can be introduced into proteins by non-oxidative mechanisms. Reactive carbonyl compounds have been observed to have increased in patients with renal failure.

O-GlcNAc-selective-N-acetyl-beta-D-glucosaminidase activity and mRNA expression in muscle is related to glucosamine-induced insulin resistance.

Glucosamine (GlcN)-induced insulin resistance is associated with an increase in O-linked-N-acetylglucosaminylated modified proteins (O-GlcNAcylated proteins). The role played by O-GlcNAc-selective-N-acetyl-beta-D-glucosaminidase (O-GlcNAcase), which removes O-N-acetyl-glucosamine residues from O-GlcNAcylated proteins, has not yet been demonstrated. We investigated whether GlcN-induced whole-body insulin resistance is related to tissue O-GlcNAcase activity and mRNA expression.

Protein antioxidant response to the stress and the relationship between molecular structure and antioxidant function.

Background: Proteins have long been considered a principal target for oxidants as a result of their abundance in biological systems. However, there is increasing evidence about the significant antioxidant activity in proteins such as albumin. It is leading to new concepts that even consider albumin not only as an antioxidant but as the major antioxidant in plasma known to be exposed to continuous oxidative stress.

Structural and functional changes in the insulin molecule produced by oxidative stress.

The change produced by oxidative stress on proteins (cross-links, backbone cleavage, amino acid modification) generates structural changes with a wide range of consequences such as increased propensity to the aggregation or proteolysis, altered immunogenicity and frequently enzymatic and binding inhibition. Insulin is particularly sensitive to conformational changes, aggregation and cross-linking; any change on insulin could impair its function. We have examined the biological activity of insulin modified by hydroxyl radical and exposed to acrolein in rats and adiposites.

Chemical and functional changes of human insulin by in vitro incubation with blood from diabetic patients in oxidative stress.

Oxidative stress damage to biomolecules has been implicated in several diseases including diabetes mellitus. In the present study, we investigated the effect of oxidative stress in whole blood (WB) from diabetic patients (n = 60) on recombinant human insulin. Insulin was incubated with WB obtained from diabetic patients (DP) who had hyperglycemia (>300 mg/dL) or from 41 healthy volunteers (HV).

Whole body hyperthermia reduces oxidative stress in the striatum of rats in an animal model of mitochondrial toxicity with 3-nitropropionic acid.

Purpose: The goal of this study was to determine whether whole body hyperthermia (WBH) could reduce oxidative stress in the striatum produced by 3-nitropropionic acid (3-NP), a mitochondrial toxin that irreversibly inhibits succinate dehydrogenase (SDH), causing impairment of energy metabolism, oxidative stress and a selective degeneration of striatal cells.

Methods: Rats were subjected to WBH (42 degrees C) or normothermia control conditions for 30 min and then treated with 3-NP. Striatum samples were processed and the levels of protein carbonyl groups, biogenic amines, Hsp72 and salicylate hydroxylation (to probe the hydroxyl radical (OH(*)) intervention) were determined.

Determination of acrolein by high-voltage capillary electrophoresis from oxidized fatty acids.

Acrolein is an alpha,beta-unsaturated aldehyde with enormous capacity of reaction, occurs in the air like a pollutant, but it is (we know now) an important lipid peroxidation product as well. The compound is one of the several aldehydes produced from fatty acid oxidation, although it is particularly important because it constitutes the major electrophyle aldehyde derived from lipid oxidation. Acrolein can be formed actively from oxidized fatty acids and undergo aldolic condensation in alkaline pH; this is a particular characteristic that we have used in its process of separation with capillary electrophoresis.

Formation of an adduct between insulin and the toxic lipoperoxidation product acrolein decreases both the hypoglycemic effect of the hormone in rat and glucose uptake in 3T3 adipocytes.

Lipid peroxidation induced by reactive oxygen species might modify circulating biomolecules because of the formation of alpha,beta-unsaturated or dicarbonylic aldehydes. In order to investigate the interaction between a lipoperoxidation product, acrolein, and a circulating protein, insulin, the acrolein-insulin adduct was obtained. To characterize the adduct, gel filtration chromatography, sodium dodecylsulfate-polyacrylamide gel electrophoresis and carbonyl determination were performed.

Paradoxical changes in muscle gene expression in insulin-resistant subjects after sustained reduction in plasma free fatty acid concentration.

Lipid oversupply plays a role in developing insulin resistance in skeletal muscle, decreasing expression of nuclear-encoded mitochondrial genes, and increasing extracellular matrix remodeling. To determine if a decrease in plasma lipid content reverses these abnormalities, insulin-resistant subjects with a family history of type 2 diabetes had euglycemic clamps and muscle biopsies before and after acipimox treatment to suppress free fatty acids. Free fatty acids fell from 0.

Glucose-6-phosphate dehydrogenase activity and NADPH/NADP+ ratio in liver and pancreas are dependent on the severity of hyperglycemia in rat.

Hyperglycemia is associated with metabolic disturbances affecting cell redox potential, particularly the NADPH/NADP+ ratio and reduced glutathione levels. Under oxidative stress, the NADPH supply for reduced glutathione regeneration is dependent on glucose-6-phosphate dehydrogenase. We assessed the effect of different hyperglycemic conditions on enzymatic activities involved in glutathione regeneration (glucose-6-phosphate dehydrogenase and glutathione reductase), NADP(H) and reduced glutathione concentrations in order to analyze the relative role of these enzymes in the control of glutathione restoration.

Oxidation by reactive oxygen species (ROS) alters the structure of human insulin and decreases the insulin-dependent D-glucose-C14 utilization by human adipose tissue.

The formation of dityrosine of human insulin oxidized by metal-catalyzed oxidation system (H2O2/Cu) was estimated by fluorescent methods. The oxidation of tyrosine and phenylalanine residues present on the insulin molecule was evident after 2 minutes of in vitro oxidation due to the formation of protein-bound dityrosine. The success of oxidative protein modification was followed until available aromatic residues were consumed (60 minutes), measured by their emission at 405 nm.

Peroxynitrite activates glucose uptake in 3T3-L1 adipocytes through a PI3-K-dependent mechanism.

Peroxynitrite, the product of the reaction between *NO and O2*-, is a strong oxidant and nitrating molecule, and it has been recently consideredas a component of some important signaling pathways. Herein, we report the effect of peroxynitrite on glucose uptake in 3T3-L1 adipocytes. Peroxynitrite stimulated glucose uptake and this effect was inhibited by citochalasin B, indicating the participation of facilitated GLUT transporters.

Diabetogenic effect of STZ diminishes with the loss of nitric oxide: role of ultraviolet light and carboxy-PTIO.

Nitric oxide has been demonstrated to participate in beta-cell damage during streptozotocin (STZ)-induced diabetes. STZ consists of 2-deoxy-D-glucose substituted by N-methyl-N-nitrosourea at C-2 and therefore can liberate (.) NO.