Oxalate Accumulation Research Articles

Wild Soybean Oxalyl-CoA Synthetase Degrades Oxalate and Affects the Tolerance to Cadmium and Aluminum Stresses.

Acyl activating enzyme 3 (AAE3) was identified as being involved in the acetylation pathway of oxalate degradation, which regulates the responses to biotic and abiotic stresses in various higher plants. Here, we investigated the role of Glycine soja AAE3 (GsAAE3) in Cadmium (Cd) and Aluminum (Al) tolerances. The recombinant GsAAE3 protein showed high activity toward oxalate, with a Km of 105.10 ± 12.30 μM and Vmax of 12.64 ± 0.34 μmol min−1 mg−1 protein, suggesting that it functions as an oxalyl–CoA synthetase. The expression of a GsAAE3–green fluorescent protein (GFP) fusion protein in tobacco leaves did not reveal a specific subcellular localization pattern of GsAAE3. An analysis of the GsAAE3 expression pattern revealed an increase in GsAAE3 expression in response to Cd and Al stresses, and it is mainly expressed in root tips. Furthermore, oxalate accumulation induced by Cd and Al contributes to the inhibition of root growth in wild soybean. Importantly, GsAAE3 overexpression increases Cd and Al tolerances in A. thaliana and soybean hairy roots, which is associated with a decrease in oxalate accumulation. Taken together, our data provide evidence that the GsAAE3-encoded protein plays an important role in coping with Cd and Al stresses.

Metabolome analysis of rice leaves to obtain low-oxalate strain from ion beam-mutagenised population.

Rice leaves and stems, which can be used as rice straw for livestock feed, accumulate soluble oxalate. The oxalate content often reaches 5% of the dry weight leaves. Excess uptake of oxalate-rich plants causes mineral deficiencies in vertebrates, so it is important to reduce the oxalate content in rice leaves to produce high-quality rice straw. However, the mechanism of oxalate accumulation in rice has remained unknown. To understand metabolic networks relating oxalate accumulation in rice. In this study, we performed metabolome analysis of rice M2 population generated by ion-beam irradiation using CE-MS. The result showed wide variation of oxalate contents in M2 plants compared with those of control plants. Multivariate analyses of metabolome dataset revealed that oxalate accumulation was strongly related with anionic compounds such as 2OG and succinate. For low-oxalate plants, four patterns of metabolic alterations affected oxalate contents in the M2 leaves were observed. In M3 plants, we found putative low-oxalate line obtained from low-oxalate M2 mutant. These findings would lead to produce the low-oxalate rice and to understand the oxalate synthesis in plants.These findings would lead to produce the low-oxalate rice and to understand the oxalate synthesis in plants.

The ILE56 mutation on different genetic backgrounds of alanine:glyoxylate aminotransferase: Clinical features and biochemical characterization

Primary Hyperoxaluria type I (PH1) is a rare disease caused by mutations in the AGXT gene encoding alanine:glyoxylate aminotransferase (AGT), a liver enzyme involved in the detoxification of glyoxylate, the failure of which results in accumulation of oxalate and kidney stones formation. The role of protein misfolding in the AGT deficit caused by most PH1-causing mutations is increasingly being recognized. In addition, the genetic background in which a mutation occurs is emerging as a critical risk factor for disease onset and/or severity. Based on these premises, in this study we have analyzed the clinical, biochemical and cellular effects of the p.Ile56Asn mutation, recently described in a PH1 patient, as a function of the residue at position 11, a hot-spot for both polymorphic (p.Pro11Leu) and pathogenic (p.Pro11Arg) mutations. We have found that the p.Ile56Asn mutation induces a structural defect mostly related to the apo-form of AGT. The effects are more pronounced when the substitution of Ile56 is combined with the p.Pro11Leu and, at higher degree, the p.Pro11Arg mutation. As compared with the non-pathogenic forms, AGT variants display reduced expression and activity in mammalian cells. Vitamin B6, a currently approved treatment for PH1, can overcome the effects of the p.Ile56Asn mutation only when it is associated with Pro at position 11. Our results provide a first proof that the genetic background influences the effects of PH1-causing mutations and the responsiveness to treatment and suggest that molecular and cellular studies can integrate clinical data to identify the best therapeutic strategy for PH1 patients.

Effects of Daily Light Integral and LED Spectrum on Growth and Nutritional Quality of Hydroponic Spinach

To achieve clean and high-quality spinach production, the effects of daily light integral (DLI) and light spectrum on growth, nutritional quality, and energy yield of hydroponic spinach (Spinacia oleracea L.) were investigated in a closed plant factory under light-emitting diode (LED) lighting. The hydroponic spinach plants were grown under 16 combinations of four levels of DLI (11.5, 14.4, 17.3, and 20.2 mol m−2 day−1) with four light spectra: LED lamps with ratio of red light to blue light (R:B ratio) of 0.9, 1.2, and 2.2 and fluorescent lamps with R:B ratio of 1.8 as control. The results show that total fresh and dry weights, energy yield, and light energy use efficiency (LUE) of harvested spinach were higher under D17.3-L1.2 treatment compared to other treatments. The higher net photosynthetic rates were shown at DLI of 17.3 mol m−2 day−1 regardless of light quality. Higher vitamin C contents of spinach in all LED treatments were obtained compared with the control. L1.2 treatments with higher fraction of blue light led to more vitamin C content, lower nitrate content, and higher LUE independent of DLI. L2.2 treatment with more fraction of red light was beneficial to reduce oxalate accumulation. Power consumption based on increased total fresh weight under LED lamps with R:B ratio of 1.2 in different DLIs was over 38% lower than that under the fluorescent lamps and 1.73 kWh per 100 g FW at DLI of 17.3 mol m−2 day−1. In conclusion, lighting environment in DLI of 17.3 mol m−2 day−1 using LED lamps with R:B ratio of 1.2 is suggested for the design of a LED plant factory for hydroponic spinach production.

SO011OXALATE-DEGRADING ACTIVITY IN FECAL MICROBIOTA ASSOCIATED WITH BLOOD LIPID PROFILE IN DIALYSIS PATIENTS

Abstract Background and Aims Cardiovascular disease (CVD) remains the leading cause of morbidity and death in end-stage renal disease (ESRD) patients. Thus, the accumulation of oxalate due to ESRD can increase the risk of CVD. Also, the ability of fecal oxalate-degrading activity (ODA) to reduce plasma oxalate levels has been discussed. On the other hand, despite a key role of atherogenic dyslipidemia in the development of CVD, only a few studies have shown a potential role of microbiota in the regulation of blood lipid profiles in the general population. However, at present, there is a general lack of research on this topic in dialysis patients. The present study aimed to investigate the association between oxalate-degrading activity (ODA) in fecal microbiota and blood lipid profiles in ESRD patients. Method We represented the data of a cross-sectional pilot study examining ODA in fecal microbiota, plasma oxalate concentration (POx) and blood lipid profile markers in 32 ESRD patients. Among the patients, there were 21 hemodialysis (HD) patients and 11 peritoneal dialysis (PD) patients. The average age of the patients was 52.5 [39; 65] years. The redoximetric titration with KMnO4 was adopted to evaluate total ODA in fecal microbiota. The results were expressed in % oxalate degradation per 0.01 g of feces. The blood lipid spectrum was determined in all patients: total cholesterol level (TC), high (HDL), low (LDL) and very low (VLDL) density cholesterol, triglycerides (TG) and atherogenic index of plasma (AIP). The median (Me) and interquartile ranges [Q25; Q75] were calculated using the nonparametric Kruskal-Wallis test. The Spearman test was used for the correlation analysis. Chi-square tests were used for comparison of 2 proportions. All statistical analyses were performed using MedCalc. Results Dyslipidemia defined as an increase in atherogenic lipoprotein fractions and inhibition of HDL cholesterol was identified in 13/32 (40.6%) ESRD patients. Negative ODA in fecal microbiota (≤ 0 % /0.01 g) was observed in 14/32 (43.7%) patients. Among them, there were 5/21 (23.8%) HD patients and 7/11 (63.6%) PD patients (χ2=3.9, p=0.04). Significantly lower ODA in fecal microbiota was observed in the patients with atherogenic dyslipidemia in comparison with dyslipidemia-free patients (-5.0 [-8.7; 3.7] vs 3.0 [0.5; 9] %/0.01 g of feces, p=0.02) (Fig. 1). Less ODA in fecal microbiota was, higher levels of TG (r=-0.5, p=0.004) (Fig. 2), VLDL (r=-0.34, p=0.05) (Fig. 3) and, accordingly, AIP (r=-0.38, p=0.03) (Fig. 4) occurred. Conclusion The results of our study have provided preliminary evidence on the fact that a decrease in total ODA in fecal microbiota is associated with atherogenic dyslipidemia. Further studies are needed to determine the role of fecal ODA in the formation of dyslipidemia.

P1713A CASE OF DEVASTATING BARIATRIC SURGERY-RELATED ACUTE OXALATE NEPHROPATHY FIRST DIAGNOSED AFTER KIDNEY TRANSPLANTATION

Abstract Background and Aims Despite the obvious efficacy in achieving weight loss, traditional malabsorptive procedures (intestinal by-pass) used for the treatment of obesity, may be associated with enteric oxaluria. Enteric oxaluria, by causing calcium-oxalate stones and nephrocalcinosis, represents an under-recognized cause of end-stage kidney disease in patients with history of intestinal by-pass. Herein, we describe a patient with a long-standing history of intestinal by-pass who developed a devastating acute oxalate nephropathy first diagnosed after kidney transplantation. Method A white female aged 50, who started hemodialysis one year earlier because of tubule-interstitial nephritis on a kidney biopsy, and who had history of recurrent kidney stones (calcium oxalate), underwent urgent deceased-donor kidney transplantation because of exhausted vascular access for hemodialysis (tunneled CVC right giugular vein as the last resort). She had received intestinal by-pass surgery 20 yrs earlier, and had a pacemaker implantation in the left sublavian vein for AV block two years earlier. She was highly sensitized because of blood transfusions at the time of surgery. Results After transplantation, graft function had immediate recovery, serum creatinine decreasing to 2.0mg/dL (117 mmol/L) on post-operative day (POD) 3. Shortly after, serum creatinine started rising until it reached 4.0mg/dL (354mmol/L) on POD 5. Three graft biopsies (performed on POD 6, 9 and 15 post-transplant) revealed acute oxalate nephropathy ( Figure1-2 large oxalate crystals on fresh unfixed core of kidney tissue analyzed under bright field microscope using polarized light) with no sign of rejection. Serial monitoring of Luminex SAB did not reveal circulating anti-HLA donor specific antibodies. Fundus examination revealed two tiny mono-lateral retinal oxalate deposits, whereas bone biopsy did not reveal oxalate accumulation. Plasma oxalate levels were 43 mmol/L on POD 10 were urinary oxalate excretion was 29mg /day on POD 14. The patient slowly progressed to end-stage kidney disease 2-month post-transplantation despite daily high flux dialysis since POD 7, fat-free and oxalate-free diet, oral potassium and high dose pyridoxine supplements. Conclusion Patients on chronic dialysis with a previous history of bariatric surgery via intestinal by-pass may have oxalate nephropathy caused by enteric oxaluria as unknown primary renal disease. The disease may recur shortly after transplantation despite the adoption of prompt aggressive treatment for oxalate removal.

Responses of resistant and susceptible hybrid clones of Eucalyptus urophylla × Eucalyptus grandis to infection by Ceratocystis fimbriata

A histopathological study using one resistant and one susceptible clone of Eucalyptus urophylla × Eucalyptus grandis hybrid showed that the colonization of Ceratocystis fimbriata was limited by rapid and intense host defense responses such as closure of the vessel pits; formation of tyloses and gels; accumulation of amorphous material, starch, phenolic compounds, and calcium oxalate; and tissue lignification. The defense mechanisms of the resistant clone were not lethal to the pathogen because the fungus was reisolated from the diseased tissue. The use of resistant genotypes of eucalypt is widely used to control Ceratocystis wilt caused by Ceratocystis fimbriata. However, little is known regarding the fungal infection process and the host defense responses. Thus, the objectives of this study were to compare the histopathological responses of one resistant and one susceptible clone of Eucalyptus urophylla × Eucalyptus grandis to artificial inoculation with C. fimbriata and to identify possible host defense responses against fungal infection. Fungal colonization was analyzed by light and scanning electron microscopy. The host defense responses to artificial fungal inoculation were evaluated through histochemical analysis and determining of the lignin concentration and lesion lengths, whereas the pathogen viability was confirmed by reisolations. Both tested clones showed similar responses against fungal infection but presented defense responses with different speeds and intensities. Fungal colonization was not restricted in the tissue of plants from the susceptible clone, whereas in the resistant clone, fungal colonization was limited to the xylem vessels and parenchyma around the vessels due to closure of the vessel pits; intense formation of tyloses and gels; accumulation of amorphous material, starch, phenolic compounds, and calcium oxalate; and tissue lignification. However, the fungus was reisolated from the inoculated tissues of both clones. The resistance of eucalypt cuttings was found to be based on the rapid and intense defense responses shaped by biochemical and structural mechanisms that contained fungal colonization in the xylem vessels and parenchyma tissues.

Natural history of GM1 gangliosidosis mouse models generated by The Jackson Laboratory Rare and Orphan Disease Center

Primary Hyperoxaluria type I (PH1) is a rare disease caused by mutations in the AGXT gene encoding alanine:glyoxylate aminotransferase (AGT), a liver enzyme involved in the detoxification of glyoxylate, the failure of which results in accumulation of oxalate and kidney stones formation. The role of protein misfolding in the AGT deficit caused by most PH1-causing mutations is increasingly being recognized. In addition, the genetic background in which a mutation occurs is emerging as a critical risk factor for disease onset and/or severity. Based on these premises, in this study we have analyzed the clinical, biochemical and cellular effects of the p.Ile56Asn mutation, recently described in a PH1 patient, as a function of the residue at position 11, a hot-spot for both polymorphic (p.Pro11Leu) and pathogenic (p.Pro11Arg) mutations. We have found that the p.Ile56Asn mutation induces a structural defect mostly related to the apo-form of AGT. The effects are more pronounced when the substitution of Ile56 is combined with the p.Pro11Leu and, at higher degree, the p.Pro11Arg mutation. As compared with the non-pathogenic forms, AGT variants display reduced expression and activity in mammalian cells. Vitamin B6, a currently approved treatment for PH1, can overcome the effects of the p.Ile56Asn mutation only when it is associated with Pro at position 11. Our results provide a first proof that the genetic background influences the effects of PH1-causing mutations and the responsiveness to treatment and suggest that molecular and cellular studies can integrate clinical data to identify the best therapeutic strategy for PH1 patients.

Gene therapy PR006 increased progranulin levels and improved lysosomal related phenotypes in model systems

Primary Hyperoxaluria type I (PH1) is a rare disease caused by mutations in the AGXT gene encoding alanine:glyoxylate aminotransferase (AGT), a liver enzyme involved in the detoxification of glyoxylate, the failure of which results in accumulation of oxalate and kidney stones formation. The role of protein misfolding in the AGT deficit caused by most PH1-causing mutations is increasingly being recognized. In addition, the genetic background in which a mutation occurs is emerging as a critical risk factor for disease onset and/or severity. Based on these premises, in this study we have analyzed the clinical, biochemical and cellular effects of the p.Ile56Asn mutation, recently described in a PH1 patient, as a function of the residue at position 11, a hot-spot for both polymorphic (p.Pro11Leu) and pathogenic (p.Pro11Arg) mutations. We have found that the p.Ile56Asn mutation induces a structural defect mostly related to the apo-form of AGT. The effects are more pronounced when the substitution of Ile56 is combined with the p.Pro11Leu and, at higher degree, the p.Pro11Arg mutation. As compared with the non-pathogenic forms, AGT variants display reduced expression and activity in mammalian cells. Vitamin B6, a currently approved treatment for PH1, can overcome the effects of the p.Ile56Asn mutation only when it is associated with Pro at position 11. Our results provide a first proof that the genetic background influences the effects of PH1-causing mutations and the responsiveness to treatment and suggest that molecular and cellular studies can integrate clinical data to identify the best therapeutic strategy for PH1 patients.

Biochemical properties and oxalate-degrading activity of oxalate decarboxylase from bacillus subtilis at neutral pH.

Oxalate decarboxylase (OxDC) from Bacillus subtilis is a Mn‐dependent hexameric enzyme that converts oxalate to carbon dioxide and formate. OxDC has greatly attracted the interest of the scientific community, mainly due to its biotechnological and medical applications in particular for the treatment of hyperoxaluria, a group of pathologic conditions caused by oxalate accumulation. The enzyme has an acidic optimum pH, but most of its applications involve processes occurring at neutral pH. Nevertheless, a detailed biochemical characterization of the enzyme at neutral pH is lacking. Here, we compared the structural–functional properties at acidic and neutral pH of wild‐type OxDC and of a mutant form, called OxDC‐DSSN, bearing four amino acid substitutions in the lid (Ser161‐to‐Asp, Glu162‐to‐Ser, Asn163‐toSer, and Ser164‐to‐Asn) that improve the oxalate oxidase activity and almost abolish the decarboxylase activity. We found that both enzymatic forms do not undergo major structural changes as a function of pH, although OxDC‐DSSN displays an increased tendency to aggregation, which is counteracted by the presence of an active‐site ligand. Notably, OxDC and OxDC‐DSSN at pH 7.2 retain 7 and 15% activity, respectively, which is sufficient to degrade oxalate in a cellular model of primary hyperoxaluria type I, a rare inherited disease caused by excessive endogenous oxalate production. The significance of the data in the light of the possible use of OxDC as biological drug is discussed. © 2019 IUBMB Life, 1–11, 2019

Interactive effect of nitrogen nutrition, nitrate reduction and seasonal variation on oxalate synthesis in leaves of Napier-bajra hybrid (Pennisetum purpureum × P. glaucum)

Oxalate may cause hypocalcaemia or formation of urinary calculi in animals with prolonged grazing of Napier grass (Pennisetum purpureum) × pearl millet (bajra, P. glaucum) hybrid (NBH). We investigated the influence of nitrate metabolism, nitrogen (N) nutrition, N forms and seasonal variation on oxalate accumulation in leaves of NBH in a field experiment in Ludhiana, India. The experiment was a randomised block design with three N sources (nitrate, amide and ammonium), three application rates (50, 75 and 100 kg N/ha), four seasons (summer, monsoon, autumn, pre-winter) and three replicates. Applied N nutrition induced oxalate synthesis and activities of nitrate reductase (NR) and nitrite reductase (NiR) enzymes. A positive association of N nutrition with both oxalate accumulation and nitrate-reducing enzymes was found. Nitrate-N increased oxalate accumulation and NiR activity more than ammonium and amide. A differential effect of seasons on NR and NiR activities, as well as on oxalate accumulation, was observed. Among different harvest seasons, NR and NiR activities were positively associated with oxalate accumulation in summer and the monsoon season. These results suggest that N fertilisation, particularly in nitrate form, is associated with upregulation of nitrate-reducing enzymes, leading to oxalate accumulation in NBH leaves.

Quantitation of oxalates in corms and shoots of Colocasia esculenta (L.) Schott under drought conditions

Oxalate (calcium oxalate) accumulation in taro plants (Colocasia esculenta (L.) Schott) impacts their nutritional quality, producing acridity, causing lips, mouth and throat tissues swelling if consumed fresh. The oxalate content is related to photosynthesis, through the glycolate–glyoxylate oxidation pathway. The plant’s photosynthetic rate usually increases in non-stressed conditions. Differences in photosynthetic rate are indirectly related to the chlorophyll content index. Protein accumulation and starch variation are also important traits to understand the taro oxalate synthesis caused by drought and how they affect corm quality. The purpose of this study was to quantitate oxalates in taro corms and shoots submitted to drought conditions and to evaluate how stress response can affect the nutritional quality of taro whole-plant. Seven taro genotypes from Madeira, Canaries and Pacific Community (SPC) collections were grown in greenhouse conditions and submitted to different watering regimes for drought tolerance screening. Corms and shoots were harvested and evaluated for oxalates (soluble, insoluble and total), chlorophyll content index (CCI), crude protein, starch, starch solubility in water and starch swelling power. All accessions had very high calcium oxalate content. Drought-tolerant genotypes showed good osmotic response by oxalate precipitation and mobilization through shoot to corm tissues, photosynthesis adaptation by increase of CCI, protein accumulation, and very low starch hydrolysis. Sensitive-drought genotypes showed less mobilization of calcium oxalate, decreased photosynthetic rate and protein synthesis, and slight increase of starch hydrolysis. Variation in taro oxalate content is consistent and significantly correlated with the photosynthetic rate, carbohydrate metabolism and protein synthesis.

Maize Oxalyl-CoA Decarboxylase1 Degrades Oxalate and Affects the Seed Metabolome and Nutritional Quality.

The organic acid oxalate occurs in microbes, animals, and plants; however, excessive oxalate accumulation in vivo is toxic to cell growth and decreases the nutritional quality of certain vegetables. However, the enzymes and functions required for oxalate degradation in plants remain largely unknown. Here, we report the cloning of a maize (Zea mays) opaque endosperm mutant that encodes oxalyl-CoA decarboxylase1 (EC4.1.1.8; OCD1). Ocd1 is generally expressed and is specifically induced by oxalate. The ocd1 mutant seeds contain a significantly higher level of oxalate than the wild type, indicating that the ocd1 mutants have a defect in oxalate catabolism. The maize classic mutant opaque7 (o7) was initially cloned for its high lysine trait, although the gene function was not understood until its homolog in Arabidopsis thaliana was found to encode an oxalyl-CoA synthetase (EC 6.2.1.8), which ligates oxalate and CoA to form oxalyl-CoA. Our enzymatic analysis showed that ZmOCD1 catalyzes oxalyl-CoA, the product of O7, into formyl-CoA and CO2 for degradation. Mutations in ocd1 caused dramatic alterations in the metabolome in the endosperm. Our findings demonstrate that ZmOCD1 acts downstream of O7 in oxalate degradation and affects endosperm development, the metabolome, and nutritional quality in maize seeds.

Effect of Cadmium on Distribution of Potassium, Calcium, Magnesium, and Oxalate Accumulation in Amaranthus cruentus L. Plants

Effect of cadmium at concentrations of 1 and 10 μM on biomass increment, mineral nutrient elements (potassium, calcium, and magnesium) accumulation, and oxalic acid pools in organs of Amaranthus cruentus L. plants growing under water culture conditions was investigated. It was established that cadmium in the tested concentrations did not exert any pronounced damage effect on amaranth plants, which was in part shown to be associated with its predominant accumulation in roots and minimization of its transfer into young leaves. It was demonstrated that, in sublethal concentrations, this metal exerted growth response in the above ground amaranth organs expressed in stimulation of young leaves' growth, while simultaneously inhibiting growth processes in mature leaves. The results obtained are discussed in the context of determination of plant growth response to the effect of cadmium by certain metabolic changes whose functional manifestations consisted in carbon metabolism intensification and increase in water-insoluble oxalate content in amaranth leaves. Simultaneous observed increase in Ca2+ and Mg2+ levels in young and mature amaranth leaves is considered as additional evidence in favor of accelerating leaves' ontogenesis pace under the effect of sublethal doses of cadmium.

Sclerotinia sclerotiorum: An Evaluation of Virulence Theories

Oxalic acid production in Sclerotinia sclerotiorum has long been associated with virulence. Research involving UV-induced, genetically undefined mutants that concomitantly lost oxalate accumulation, sclerotial formation, and pathogenicity supported the conclusion that oxalate is an essential pathogenicity determinant of S. sclerotiorum. However, recent investigations showed that genetically defined mutants that lost oxalic acid production but accumulated fumaric acid could cause disease on many plants and substantiated the conclusion that acidic pH, not oxalic acid per se, is the necessary condition for disease development. Critical evaluation of available evidence showed that the UV-induced mutants harbored previously unrecognized confounding genetic defects in saprophytic growth and pH responsiveness, warranting reevaluation of the conclusions about virulence based on the UV-induced mutants. Furthermore, analyses of the evidence suggested a hypothesis for the existence of an unrecognized regulator responsive to acidic pH. Identifying the unknown pH regulator would offer a new avenue for investigating pH sensing/regulation in S. sclerotiorum and novel targets for intervention in disease control strategies.

Specific Inhibition of Hepatic Lactate Dehydrogenase Reduces Oxalate Production in Mouse Models of Primary Hyperoxaluria.

Primary hyperoxalurias (PHs) are autosomal recessive disorders caused by the overproduction of oxalate leading to calcium oxalate precipitation in the kidney and eventually to end-stage renal disease. One promising strategy to treat PHs is to reduce the hepatic production of oxalate through substrate reduction therapy by inhibiting liver-specific glycolate oxidase (GO), which controls the conversion of glycolate to glyoxylate, the proposed main precursor to oxalate. Alternatively, diminishing the amount of hepatic lactate dehydrogenase (LDH) expression, the proposed key enzyme responsible for converting glyoxylate to oxalate, should directly prevent the accumulation of oxalate in PH patients. Using RNAi, we provide the first in vivo evidence in mammals to support LDH as the key enzyme responsible for converting glyoxylate to oxalate. In addition, we demonstrate that reduction of hepatic LDH achieves efficient oxalate reduction and prevents calcium oxalate crystal deposition in genetically engineered mouse models of PH types 1 (PH1) and 2 (PH2), as well as in chemically induced PH mouse models. Repression of hepatic LDH in mice did not cause any acute elevation of circulating liver enzymes, lactate acidosis, or exertional myopathy, suggesting further evaluation of liver-specific inhibition of LDH as a potential approach for treating PH1 and PH2 is warranted.

Expression Analysis of Oxalate Metabolic Pathway Genes Reveals Oxalate Regulation Patterns in Spinach.

Spinach (Spinacia oleracea L.) is one of most important leafy vegetables because of its high nutritional value and high oxalate content, which can be toxic with negative effects on human nutrition. Ammonium and nitrate can effectively regulate oxalate accumulation, although the mechanisms underlying the oxalate biosynthesis and regulation are still undetermined in plants. In the present study, we identified 25 putative genes that are involved in the oxalate biosynthetic and degradation pathway, before analyzing the oxalate content and the expression levels of the corresponding proteins under normal growth conditions, with or without ammonium and nitrate treatments, using high and low oxalate-accumulated spinach genotypes. The two cultivars exhibited different profiles of total oxalate and soluble oxalate accumulation. The high oxalate concentrations in spinach were as a result of the high transcription levels of the genes that are involved in oxalate biosynthesis under normal growth conditions, such as SoGLO2, SoGLO3, three SoOXACs, SoMLS, SoMDH1, SoMDH2, and SoMDH4. The results revealed that the ammonium and nitrate were able to control the oxalate content in leaves, possibly because of the different transcription levels of the genes. The oxalate content is regulated by complex regulatory mechanisms and is varied in the different varieties of spinach. The results from this research may be used to assist the investigation of the mechanism of oxalate regulation and breeding for reduced oxalate content in spinach.

Nanocapsules of oxalate oxidase for hyperoxaluria treatment

Enzyme therapeutics have great potential for the treatment of systemic disorders such as urolithiasis and nephrocalcinosis, which are caused by the excessive accumulation of oxalate. However, exogenous enzymes have short half-lives in vivo and elicit high immunogenicity, which largely limit the therapeutic outcomes. Herein, we report a delivery strategy whereby therapeutic enzymes are encapsulated within a thin zwitterionic polymer shell to form enzyme nanocapsules. The strategy is exemplified by the encapsulation of oxalate oxidase (OxO) for the treatment of hyperoxaluria, because as-synthesized OxO nanocapsules have a prolonged blood circulation half-life and elicit reduced immunogenicity. Our design of enzyme nanocapsules that enable the systemic delivery of therapeutic enzymes can be extended to various biomedical applications.

Anatomically distinct representatives of Cactaceae Juss. family have different response to acute heat shock stress

In order to escape extreme environmental conditions plants have developed different survival strategies. The study of plant response to high temperatures is especially interesting in representatives of varied cacti families that have to resist big temperature oscillations. In the present study plants of Aylostera, Echinocactus and Mammillaria genera were exposed to temperatures of 40 or 50 °C for 3 h and peroxidase and superoxide dismutase activity, photosynthetic pigments and flavonoids concentration, and lipid peroxide oxidation level in the stem were determined. Plants with different anatomical structure showed distinct patterns of response to high temperature. Plants of Echinocactus grusonii proved the highest drought and heat resistant with strong antioxidant response and the most expressed xerophytic features of anatomical structures (epidermis and cuticle thickening, calcium oxalate accumulation, water-storage tissue development). Heat stress induced a quick increase of peroxidase activity and flavonoid concentration in this species. Relative heat resistance (40 °C) in Mammillaria bocasana is also facilitated by increased flavonoid concentration, chlorophyll a and carotenoid concentration and also high superoxide dismutase activity under normal conditions.We conclude that the development of antioxidant reactions depends on anatomical protection of plants. More effective anatomical conformation to the stress conditions may be accompanied by rapid response to stress at the antioxidant biochemical level. Less effective protection at the anatomical level to hyperthermia is accompanied by the presence of a larger activity of antioxidant enzymes in conditions without short-term high-temperature stress. Plants which do not possess these qualities, Aylostera flavistyla in particular, suffer more from short-term high-temperature stress.

Characterization of metabolic network of oxalic acid biosynthesis through RNA seq data analysis of developing spikes of finger millet (Eleusine coracana): Deciphering the role of key genes involved in oxalate formation in relation to grain calcium accumulation

In the present study, we identified seven major genes of oxalic acid biosynthesis pathway (SGAT, GGAT, ICL, GLO, MHAR, APO and OXO) from developing spike transcriptome of finger millet using rice as a reference. Sequence alignment of identified genes showed high similarity with their respective homolog in rice except for OXO and GLO. Transcript abundance (FPKM) reflects the higher accumulation of identified genes in GP-1 (low calcium genotype) as compared to GP-45 (high calcium genotype) which was further confirmed by qRT-PCR analysis, indicating differential oxalate formation in both genotypes. Determination of oxalic acid and tartaric acid content in developing spikes explain that higher oxalic acid content in GP-1 however, tartaric acid content was more in GP-45. Higher calcium content in GP-45 and lower oxalate accumulation may be due to the diversion of more ascorbic acid into tartaric acid and may correspond to less formation of calcium oxalate. Our results suggest that more than one pathway for oxalic acid biosynthesis might be present in finger millet with probable predominance of ascorbate-tartarate pathway rather than glyoxalate-oxalate conversion. Thus, finger millet can be use as an excellent model system for understanding more specific role of nutrients-antinutrients interactions, as evident from the present study.