Albumin antioxidant response to stress in diabetic nephropathy progression

Albumin of People with Diabetes Mellitus Is More Reduced at Low HbA1c

Oxidative stress is involved in the development, progression, and complications of diabetes mellitus (DM). Oxidative modification of human serum albumin's cysteine-34 is a marker for oxidative stress-related pathological conditions. We aimed to evaluate the redox state of albumin in patients with DM to investigate possible correlations with age, diabetes duration, and disease control status. Plasma aliquots were collected from 52 participants (26 type 1 and 26 type 2 DM). Patients were divided into two groups according to their glycated hemoglobin levels less than or equal to and greater than 58 mmol/L. Albumin redox state was assessed with high-performance liquid chromatography by fractionating it into human mercaptalbumin (HMA) and human nonmercaptalbumin 1 and 2 (HNA1 and HNA2). Albumin redox fractions were differently related to the age of study participants. In age-matched T1DM and T2DM groups, the albumin redox state was essentially the same. Irreversibly oxidized HNA2 was positively correlated with diabetes duration, especially in the T1DM group. HNA was increased in people with an increased HbA1c (>58 mmol/mol). Our results support the hypothesis that oxidative stress plays a crucial role in DM pathogenesis and emphasize the importance of diabetes control on systemic oxidative burden.

Optimization of Tokuhashi Scoring System to Improve Survival Prediction in Patients with Spinal Metastases

Introduction: Predicting survival time for patients with spinal metastases is important in treatment choice. Generally speaking, six months is a landmark cutoff point. Revised Tokuhashi score (RTS), the most widely used scoring system, lost its accuracy in predicting 6-month survival, gradually. Therefore, a more precise scoring system is urgently needed. Objective: The aim of this study is to create a new scoring system with a higher accuracy in predicting 6-month survival based on the previously used RTS. Methods: Data of 171 patients were examined to determine factors that affect prognosis (reference group), and the remaining (validation group) were examined to validate the reliability of a new score, adjusted Tokuhashi score (ATS). We compared their discriminatory abilities of the prediction models using area under receiver operating characteristic curve (AUC). Results: Target therapy and the Z score of BMI (Z-BMI), which adjusted to the patients’ sex and age, were additional independent prognostic factors. Patients with target therapy use are awarded 4 points. The Z score of BMI could be added directly to yield ATS. The AUCs were 0.760 for ATS and 0.636 for RTS in the validation group. Conclusion: Appropriate target therapy use can prolong patients’ survival. Z-BMI which might reflect nutritional status is another important influencing factor. With the optimization, surgeons could choose a more individualized treatment for patients.

Cystine supplementation sustains plasma mercaptalbumin levels in rats fed low-protein diets more effectively than methionine

We recently reported that dietary cystine maintained plasma mercaptalbumin levels in rats fed low-protein diets. The present study aimed to compare the influence of low-protein diets supplemented with cystine and methionine, which is another sulfur amino acid, on plasma mercaptalbumin levels in rats. Male Sprague-Dawley rats were fed a 20% soy protein isolate diet (control group), 5% soy protein isolate diet (low-protein group) or 5% soy protein isolate diet supplemented with either methionine (low-protein + Met group) or cystine (low-protein + Cyss group) for 1 week. The percentage of mercaptalbumin within total plasma albumin of the low-protein + Met group was significantly lower than that of the control and low-protein + Cyss groups. No significant differences in the mRNA levels of tumor necrosis factor-α, interleukin-6, interleukin-1β, and cyclooxygenase 2 in blood cells were observed between the low-protein + Met and low-protein + Cyss groups. Treatment with buthionine-(S,R)-sulfoximine, an inhibitor of glutathione synthesis, did not influence the percentage of mercaptalbumin within total plasma albumin in rats fed the low-protein diet supplemented with cystine. These results suggest that supplementation with cystine may be more effective than that with methionine to maintain plasma mercaptalbumin levels in rats with protein malnutrition. Cystine might regulate plasma mercaptalbumin levels via the glutathione-independent pathway.

A Blood Biomarker for Duchenne Muscular Dystrophy Shows That Oxidation State of Albumin Correlates with Protein Oxidation and Damage in Mdx Muscle

Duchenne muscular dystrophy (DMD) is a severe X-linked muscle wasting disease with no cure. While the precise mechanisms of progressive dystropathology remain unclear, oxidative stress caused by excessive generation of oxidants is strongly implicated. Blood biomarkers that could track oxidant levels in tissues would be valuable to measure the effectiveness of clinical treatments for DMD; our research has focused on developing such biomarkers. One target of oxidants that has the potential to be harnessed as a clinical biomarker is the thiol side chain of cysteine 34 (Cys34) of the blood protein albumin. This study using the mdx mouse model of DMD shows that in plasma, albumin Cys34 undergoes thiol oxidation and these changes correlate with levels of protein thiol oxidation and damage of the dystrophic muscles. A comparison with the commonly used biomarker protein carbonylation, confirmed that albumin thiol oxidation is the more sensitive plasma biomarker of oxidative stress occurring in muscle tissue. We show that plasma albumin oxidation reflects muscle dystropathology, as increased after exercise and decreased after taurine treatment of mdx mice. These data support the use of albumin thiol oxidation as a blood biomarker of dystropathology to assist with advancing clinical development of therapies for DMD.

Efficacy of tripterygium glycosides combined with ARB on diabetic nephropathy: a meta-analysis

The purpose of this meta-analysis was to evaluate the beneficial and adverse effects of tripterygium glycosides (TGs) combined with angiotensin II receptor blocker (ARB) on diabetic nephropathy (DN). We searched for randomized controlled trials (RCTs) in PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang Data, Chinese Biomedical Literature Database, China Science and Technology Journal Database up to June 2017. Weighted mean difference (WMD) and standardized mean difference (SMD) were used for continuous variables and all variables were expressed by 95% confidence interval (CI). Twenty-three studies with 1810 DN patients were included in this meta-analysis. TG combined with ARB statistically significantly improved 24-h urinary total protein (24-h UTP) (SMD = −1.46; 95% CI = −1.84 to −1.09; P<0.00001), urinary albumin excretion rate (UAER) (SMD = −6.9; 95% CI = −9.65 to −4.14, P<0.00001), serum creatinine (SCr) (WMD = −7.65.14; 95% CI = −12.99 to −2.31; P=0.005) and albumin (Alb) (WMD = 5.7; 95% CI = 4.44 to 6.96; P<0.00001) more than did ARB alone. TG combined with ARB statistically significantly affected the level of serum glutamic pyruvic transaminase (SGPT) (WMD = 1.08; 95% CI = 0.04 to 2.12, P=0.04) more than did ARB alone. Compared with ARB alone, TG combined with ARB showed no significant difference in improving blood urea nitrogen (BUN) and hemoglobin A1c (HbA1c). Minor side effects from the combined treatment were observed and mainly focused on the abnormal liver function. TG combined with ARB offers a novel concept in treating DN, more high-quality RCTs are needed for better understanding and applying the combined treatment in DN.

A Comparison of Frailty Measures at Listing to Predict Outcomes After Lung Transplantation

BACKGROUND

Sarcopenia may be an important predictive factor of outcomes after lung transplantation (LTx). Serum albumin and the 6-minute walk distance (6MWD) have been shown to be a marker of LTx outcomes. We measured sarcopenia, albumin, and 6MWD in a cohort of LTx patients and analyzed the utility of these as markers of outcomes for LTx patients.

METHODS

We retrospectively identified LTx recipients from 2013-2018 at our institution who underwent computed tomographic imaging during their listing evaluation. From that image, we measured skeletal muscle cross-sectional surface area at the third lumbar vertebral level, and sarcopenia was diagnosed by established cutoffs. Associations between sarcopenia, albumin, 6MWD, and survival, and hospital length of stay, complications, readmissions, and discharge destination were evaluated.

RESULTS

Sarcopenia was found in 72% (95 of 132) of patients, 18% (24 of 131) of patients were hypoalbuminemic, and 41% had a low 6MWD. Survival was not associated with presence of sarcopenia (hazard ratio [HR], 1.06; 95% confidence interval [CI], 0.46-2.42) or low 6MWD (HR, 0.86; 95% CI, 0.410-1.83). Hospital length of stay, complications, readmissions, and discharge destination were not influenced by sarcopenia or 6MWD. In contrast, hypoalbuminemia was independently associated with decreased survival (HR, 2.25; 95% CI, 1.04-4.85) and a higher grade of postoperative complications (P = .04).

CONCLUSIONS

Sarcopenia is prevalent in LTx patients. Neither sarcopenia nor 6MWD predicted mortality or short-term outcomes after LTx. This is in contrast to albumin levels, which were inversely associated with survival and complications. Albumin shows promise as an important predictor of mortality and short-term outcomes after LTx.

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). The magnitude of change of the albumin tertiary structure, cell viability (LDH leakage), apoptosis (Annexin V), transdifferentiation and reticulum endoplasmic stress (Western blot and flow cytometry) and lysosomal enzyme activity were assessed.

KEY FINDINGS

We found that albumin from Stage 4 patients presented >50% higher thiol-dependent changes of tertiary structure compared to Stages 0 and 1. Cells incubated with Stage 4 albumin displayed 5 times less viability, accompanied by an increased number of apoptotic cells; evidence of profibrogenic markers E-cadherin and vimentin and higher expression of epithelial-to-mesenchymal transition markers α-SMA and E-cadherin and of endoplasmic reticulum stress protein GRP78 were likewise observed. Moreover, we found that cathepsin B activity in isolated lysosomes showed a significant inhibitory effect on albumin from patients in advanced stages of DN and on albumin that was intentionally modified.

SIGNIFICANCE

Overall, this study showed that thiol-dependent changes in albumin's tertiary structure interfere with the lysosomal proteolysis of renal TBCs, inducing molecular changes associated with interstitial fibrosis and DN progression.

Oxidative Stress, Apoptosis, and Mitochondrial Function in Diabetic Nephropathy

Diabetic nephropathy (DN) is the second most frequent and prevalent complication of diabetes mellitus (DM). The increase in the production of oxidative stress (OS) is induced by the persistent hyperglycemic state capable of producing oxidative damage to the macromolecules (lipids, carbohydrates, proteins, and nucleic acids). OS favors the production of oxidative damage to the histones of the double-chain DNA and affects expression of the DNA repairer enzyme which leads to cell death from apoptosis. The chronic hyperglycemic state unchains an increase in advanced glycation end-products (AGE) that interact through the cellular receptors to favor activation of the transcription factor NF-κB and the protein kinase C (PKC) system, leading to the appearance of inflammation, growth, and augmentation of synthesis of the extracellular matrix (ECM) in DN. The reactive oxygen species (ROS) play an important role in the pathogenesis of diabetic complications because the production of ROS increases during the persistent hyperglycemia. The primary source of the excessive production of ROS is the mitochondria with the capacity to exceed production of endogenous antioxidants. Due to the fact that the mechanisms involved in the development of DN have not been fully clarified, there are different approaches to specific therapeutic targets or adjuvant management alternatives in the control of glycemia in DN.

An oxidized/reduced state of plasma albumin reflects malnutrition due to an insufficient diet in rats

We examined whether protein- and food-intake restrictions modulate the oxidized/reduced state of plasma albumin in Sprague-Dawley rats. Rats were fed a 3%, 5%, 10% or 20% casein diet for 2 weeks. The plasma albumin concentration significantly decreased with decreasing protein intake. However, no significant difference in plasma albumin concentration was seen between rats fed the 5% or 10% casein diet. In rats fed the 5% casein diet, the percentage of mercaptalbumin within total plasma albumin was significantly lower and that of nonmercaptalbumin-1 was significantly higher than in rats fed the 10% casein diet. In experiments with food-intake restriction for 2 weeks, rats were fed 50% or 75% of the amount of a 20% casein diet consumed by control rats. The percentage of mercaptalbumin was significantly lower and that of nonmercaptalbumin-2 was significantly higher in rats with food-intake restriction than in control rats. When rats with malnutrition were refed with the 20% casein diet ad libitum, the percentage of mercaptalbumin rapidly increased. The change in the percentage of mercaptalbumin was correlated with the plasma transthyretin concentration. These results indicate that the oxidized/reduced state of plasma albumin may be applied as a sensitive marker of nutritional status reflecting dietary pattern.

Adriamycin-induced oxidative stress is prevented by mixed hydro-alcoholic extract of Nigella sativa and Curcuma longa in rat kidney

OBJECTIVE

Inflammation and oxidative stress is considered to have a crucial role in induction of nephropathy. Curcuma longa (C. longa) and Nigella sativa (N. sativa) have anti-inflammatory and antioxidant effects. This study was designed to investigate the effect of mixed hydro-alcoholic extract of N.sativa and C. longa on the oxidative stress induced by Adriamycin (ADR) in rat kidney.

MATERIALS AND METHODS

The animals were divided into 6 groups: control (CO), ADR, Adriamycin+ Vitamin C (ADR+VIT C), C. longa extract+ Adriamycin (C.LE+ADR), N. sativa extract+ Adriamycin (N.SE+ADR) and C. longa extract+ N. sativa extract + Adriamycin (N.S+C.L+ADR). ADR (5mg/kg) was injected intravenously, whereas VITC (100mg/kg) and extract of C. longa (1000mg/kg) and N. sativa (200mg/kg) were administrated orally. Finally, the renal tissue, urine and blood samples were collected and submitted to measure of redox markers, osmolarity and renal index.

RESULTS

The renal content of total thiol and superoxide dismutase (SOD) activity significantly decreased and Malondialdehyde (MDA) concentration increased in Adriamycin group compared to control group. The renal content of total thiol and SOD activity significantly enhanced and MDA concentration reduced in treated-mixed extract of C. longa and N. sativa along with ADR group compared to ADR group. The mixed extract did not restore increased renal index percentage induced by ADR. There also was no significant difference in urine and serum osmolarity between the groups.

CONCLUSION

hydro-alcoholic extracts of N.sativa and C.longa led to an improvement in ADR-induced oxidative stress and mixed administration of the extracts enhanced the aforementioned therapeutic effect.

Nitroxides protect against peroxynitrite-induced nitration and oxidation

Nitroxides are promising compounds for prevention of undesired protein modifications. The aim of this study was to compare the efficiency of 11 nitroxides, derivatives of 2,2,6,6-tetramethylpiperidine-1-oxide (TEMPO) and 2,2,5,5-tetramethylpirrolidine-1-oxyl (PROXYL) in prevention of nitration and oxidation of model compounds and human serum albumin (HSA). Most nitroxides were very efficient in preventing loss of fluorescein fluorescence induced by peroxynitrite (PN) (IC50 in the nanomolar range) and preventing HSA nitration. The loss of fluorescein fluorescence was demonstrated to be due to nitration. Nitroxides were more effective in prevention nitration than oxidation reactions. They showed a concentration window for preventing dihydrorhodamine (DHR) 123 oxidation but exerted a prooxidant effect at both high and low concentrations. No prooxidant effect of nitroxides was seen in prevention of DHR123 oxidation induced by SIN-1. In all essays hydrophobic nitroxides (especially 4-nonylamido-TEMPO and 3-carbamolyl-dehydroPROXYL) showed the lowest efficiency. An exception was the prevention of thiol group oxidation by PN and SIN-1 where hydrophobic nitroxides were the most effective, apparently due to binding to the protein. Nitroxides showed low toxicity to MCF-7 cells. Most nitroxides, except for the most hydrophobic ones, protected cells from the cytotoxic action of SIN-1 and SIN-1-induced protein nitration. These results point to potential usefulness of nitroxides for prevention of PN-induced oxidation and, especially, nitration.