Renal Lactate Research Articles

Metformin and vitamin D combination therapy ameliorates type 2 diabetes mellitus-induced renal injury in male Wistar rats.

Diabetic kidney disease is a major microvascular diabetes mellitus (DM) complication clinically associated with a gradual renal function decline. Although metformin is a common drug for managing DM, however, monotherapy treatment with any antidiabetic drug will necessitate dosage increment since type 2 DM (T2DM) deteriorates over time due to the increasing pancreatic β-cell dysfunction and will eventually require a combination therapy approach with another antidiabetic medication. Vitamin D is a food supplement that has been proven to have antidiabetic and reno-protective activities. Hence, we explore the combination of vitamin D and metformin on T2DM-induced renal dysfunction. Thirty male Wistar rats were randomized into five (5) groups: control, diabetes untreated, diabetics treated with metformin, vitamin D, and vitamin D + metformin. Vitamin D and metformin significantly reversed DM-induced hyperglycemia, electrolyte imbalance, and dyslipidemia. Also, vitamin D and metformin reversed T2DM-induced increase in serum creatinine and urea and renal lactate, LDH, and oxido-inflammatory response. These observed alterations were accompanied by an increase in proton pump activities and modulation of Nrf2/Nf-κB and XO/UA signaling. This study revealed that vitamin D and/or metformin ameliorated T2DM-induced renal injury.

Lactate metabolism and acute kidney injury.

Acute kidney injury (AKI) is a common clinically critical syndrome in hospitalized patients with high morbidity and mortality. At present, the mechanism of AKI has not been fully elucidated, and no therapeutic drugs exist. As known, glycolytic product lactate is a key metabolite in physiological and pathological processes. The kidney is an important gluconeogenic organ, where lactate is the primary substrate of renal gluconeogenesis in physiological conditions. During AKI, altered glycolysis and gluconeogenesis in kidneys significantly disturb the lactate metabolic balance, which exert impacts on the severity and prognosis of AKI. Additionally, lactate-derived posttranslational modification, namely lactylation, is novel to AKI as it could regulate gene transcription of metabolic enzymes involved in glycolysis or Warburg effect. Protein lactylation widely exists in human tissues and may severely affect non-histone functions. Moreover, the strategies of intervening lactate metabolic pathways are expected to bring a new dawn for the treatment of AKI. This review focused on renal lactate metabolism, especially in proximal renal tubules after AKI, and updated recent advances of lactylation modification, which may help to explore potential therapeutic targets against AKI.

PS-B11-2: MODULATORY EFFECT OF PPAR-GAMMA BY ACETATE ON CARDIORENOMETABOLIC DISTURBANCE ASSOCIATED WITH HIGH FAT DIET-FED INSULIN-RESISTANT MALE WISTAR RATS

Objectives: Insulin resistance (IR) and its comorbidities are critical pathogenic factors to cardiovascular disease (CVD) and chronic kidney disease (CKD). Cardiovascular disease and CKD are the leading cause of death and morbidity worldwide. Short chain fatty acids, particularly acetate has been demonstrated to elicit cardioprotective effects. Herein, we investigated its effects on IR-driven cardiorenal disorder and the possible involvement of peroxisome proliferator-activated receptor-gamma (PPAR-Gamma) in rats exposed to high fat diet (HFD). Methods: Ten-week-old male Wistar rats were assigned into three groups (n = 6/group): The groups received distilled water as vehicle (po), 40% HFD with or without 200 mg/kg sodium acetate (po) respectively. The treatments were carried out for 12 weeks. Results: HFD caused IR with impaired glucose tolerance and increased cardiac mass without altering the renal mass. Besides, HFD also increased cardiac/renal lipid indices and low-density lipoprotein, malondialdehyde, uric acid and gamma-glutamyl transferase as well as decreased glutathione, nitric oxide concentration and PPAR-Gamma. It also increased plasma urea, creatinine, troponin, and creatinine kinase and increased cardiac but not renal lactate and lactate dehydrogenase. Nevertheless, supplementation with acetate ameliorated theses alterations. Conclusions: The present results demonstrate cardiorenometabolic disturbance in HFD-induced IR and accompanied by deficiency in PPAR-Gamma. The results in addition suggest that acetate ameliorates cardiorenometabolic disturbance by increasing PPAR-Gamma and insulin sensitivity with attenuation of oxidative and pro-inflammation.

Associations between local acidosis induced by renal LDHA and renal fibrosis and mitochondrial abnormalities in patients with diabetic kidney disease

During the progression of diabetic kidney disease (DKD), renal lactate metabolism is rewired. The relationship between alterations in renal lactate metabolism and renal fibrosis in patients with diabetes has only been partially established due to a lack of biopsy tissues from patients with DKD and the intricate mechanism of lactate homeostasis. The role of lactate dehydrogenase A (LDHA)-mediated lactate generation in renal fibrosis and dysfunction in human and animal models of DKD was explored in this study. Measures of lactate metabolism (urinary lactate levels and LDHA expression) and measures of DKD progression (estimated glomerular filtration rate and Wilms' tumor-1 expression) were strongly negatively correlated in patients with DKD. Experiments with streptozotocin-induced DKD rat models and the rat renal mesangial cell model confirmed our findings. We found that the pathogenesis of DKD is linked to hypoxia-mediated lactic acidosis, which leads to fibrosis and mitochondrial abnormalities. The pathogenic characteristics of DKD were significantly reduced when aerobic glycolysis or LDHA expression was inhibited. Further studies will aim to investigate whether local acidosis caused by renal LDHA might be exploited as a therapeutic target in patients with DKD.

P07 Toxicokinetic profile of VRP-034

BackgroundPolymyxin B (PMB) can be an effective option for treating resistant Gram-negative pathogens, however, its use is severely compromised by its’ dose-limiting toxicity. VRP-034, a novel formulation of PMB, has previously reported a favourable safety profile compared with marketed PMB (Roy et al.1). This study was conducted to understand the toxicokinetic profile of VRP-034 vis-à-vis marketed PMB.Materials and methods30 healthy Sprague-Dawley rats (divided into six groups of n = 5) received one of three doses (3, 9 and 18 mg/kg/day) of either marketed PMB or VRP-034, administered subcutaneously q8 h over 2 days. Blood samples were collected prior to initiation of experiment and at 0.5, 1, 2, 4, 6, 8, 12 and 24 h after the last dose. Plasma concentrations of PMB were quantified by LC-MS. Additionally, renal toxicity was assessed via clinical pathology, kidney injury biomarkers, oxidative stress markers (3-nitrotyrosine and renal tissue lactate), gross and histopathologic observations of kidney. Urine and blood samples were collected at baseline and Day 2 for the assessment of kidney injury (KIM-1, cystatin-C, BUN and serum creatinine) using respective biochemical or ELISA kits. All values are expressed as mean ± SEM.ResultsThe plasma levels of PMB were found to increase in dose-dependent manner in both the groups. At 3 and 9 mg/kg/day, the plasma PMB exposure were similar for both VRP-034 and marketed PMB groups (AUC0–24: 6.47 ± 0.41 μg/mL·h versus 5.66 ± 0.24 μg/mL·h, P>0.05 and 22.90 ± 1.96 μg/mL·h versus 26.84 ± 1.43 μg/mL·h, P>0.05). At the highest dose of 18 mg/kg/day, the AUC0–24 was higher in the VRP-034 group (AUC0–24: 97.83 ± 12.95 μg/mL·h versus 70.48 ± 4.22 μg/mL·h), however this increase was not statistically significant (P>0.05). The levels of early kidney injury urinary biomarkers increased with dose in both the groups (Table 1). On Day 2, Kim-1 levels in the marketed PMB group increased from baseline by 3.96-fold (versus 2.31-fold in VRP-034 group), 8.21-fold (versus 5.41-fold) and 23.41-fold (versus 9.51-fold) at 3, 9, 18 mg/kg/day dose levels respectively. Likewise, cystatin-C levels increased by 6.22-fold (versus 3.26-fold in VRP-034 group), 6.25-fold (versus 3.67-fold) and 13.57-fold (versus 4.33-fold), respectively, at the three dose levels tested. Oxidative stress markers, tissue lactate and 3-nitrotyrosine, were significantly lower (P<0.05) for VRP-034 group compared with marketed PMB group at the highest dose. Histopathology revealed EGTI grade 3 kidney damage in the marketed PMB group compared with grade 1 damage in the VRP-034 group.Table 1.Kidney injury and oxidative stress markers for marketed PMB and VRO-034 groups All values are reported as mean ± SEM.Lactate marker was only measured on Day 2.UCr, urine creatinine.ConclusionsVRP-034 exhibited a more promising toxicokinetic profile as compared with marketed PMB at all dose levels. Our future work will explore the clinical translation of these findings in humans.

AT1 receptor blocker, but not an ACE inhibitor, prevents kidneys from hypoperfusion during congestive heart failure in normotensive and hypertensive rats

To provide novel insights into the pathogenesis of heart failure-induced renal dysfunction, we compared the effects of ACE inhibitor (ACEi) and AT1 receptor blocker (ARB) on systemic and kidney hemodynamics during heart failure in normotensive HanSD and hypertensive transgenic (TGR) rats. High-output heart failure was induced by creating an aorto-caval fistula (ACF). After five weeks, rats were either left untreated or treatment with ACEi or ARB was started for 15 weeks. Subsequently, echocardiographic, renal hemodynamic and biochemical measurements were assessed. Untreated ACF rats with ACF displayed significantly reduced renal blood flow (RBF) (HanSD: 8.9 ± 1.0 vs. 4.7 ± 1.6; TGR: 10.2 ± 1.9 vs. 5.9 ± 1.2 ml/min, both P < .001), ACEi had no major RBF effect, whereas ARB completely restored RBF (HanSD: 5.6 ± 1.1 vs. 9.0 ± 1.5; TGR: 7.0 ± 1.2 vs. 10.9 ± 1.9 ml/min, both P < .001). RBF reduction in untreated and ACEi-treated rats was accompanied by renal hypoxia as measured by renal lactate dehydrogenase activity, which was ameliorated with ARB treatment (HanSD: 40 ± 4 vs. 42 ± 3 vs. 29 ± 5; TGR: 88 ± 4 vs. 76 ± 4 vs. 58 ± 4 milliunits/mL, all P < .01). Unlike improvement seen in ARB-treated rats, ACE inhibition didn’t affect urinary nitrates compared to untreated ACF TGR rats (50 ± 14 vs. 22 ± 13 vs. 30 ± 13 μmol/mmol Cr, both P < .05). ARB was more effective than ACEi in reducing elevated renal oxidative stress following ACF placement. A marker of ACEi efficacy, the angiotensin I/angiotensin II ratio, was more than ten times lower in renal tissue than in plasma. Our study shows that ARB treatment, in contrast to ACEi administration, prevents renal hypoperfusion and hypoxia in ACF rats with concomitant improvement in NO bioavailability and oxidative stress reduction. The inability of ACE inhibition to improve renal hypoperfusion in ACF rats may result from incomplete intrarenal RAS suppression in the face of depleted compensatory mechanisms.

Etiology of lactic acidosis in malaria.

Lactic acidosis and hyperlactatemia are common metabolic disturbances in patients with severe malaria. Lactic acidosis causes physiological adverse effects, which can aggravate the outcome of malaria. Despite its clear association with mortality in malaria patients, the etiology of lactic acidosis is not completely understood. In this review, the possible contributors to lactic acidosis and hyperlactatemia in patients with malaria are discussed. Both increased lactate production and impaired lactate clearance may play a role in the pathogenesis of lactic acidosis. The increased lactate production is caused by several factors, including the metabolism of intraerythrocytic Plasmodium parasites, aerobic glycolysis by activated immune cells, and an increase in anaerobic glycolysis in hypoxic cells and tissues as a consequence of parasite sequestration and anemia. Impaired hepatic and renal lactate clearance, caused by underlying liver and kidney disease, might further aggravate hyperlactatemia. Multiple factors thus participate in the etiology of lactic acidosis in malaria, and further investigations are required to fully understand their relative contributions and the consequences of this major metabolic disturbance.

Food Additive (Sodium benzoate)-induced Damage on Renal Function and Glomerular Cells in Rats; Modulating Effect of Aqueous Extract of Atriplex halimus L.

The aim of the current study was to investigate the preventive and curative effect of Atriplex halimus L. (Ah) extract against the kidney damages induced by Sodium benzoate (SB) in rats. Thirty male albino rats were divided into five groups of 6 rats each: Control, Ah, SB, AhP+SB and SB+AhC. SB (100 mg/kg b.w) was added to drinking water for 15 weeks. Aqueous extract of aerial parts of Atriplex halimus received intragastrically during the last 30 days of SB exposure for curative treatment (AhC) and all the duration of SB exposure for preventive treatment (AhP). Some Biochemical markers, oxidative stress parameters and histopathology of kidney tissue were studied. Administration of Sodium benzoate to rats caused a loss of weight and a significant elevation in creatinine, urea, renal malondialdehyde levels and lactate dehydrogenase activity. These changes were accompanied by decreasing in antioxidant defenses, like reduced glutathione level, catalase and glutathione S transferase activities in the kidney. Histopathological studies showed a massive degeneration in kidney tissue in SB-exposed rats. However, treatment with Atriplex halimus (A. halimus) restored the altered of biochemical and oxidative stress markers. A. halimus also regenerated the architectural kidneys lesions to near control. With more protection offered in the curative than preventive models of treatment. In conclusion, the results demonstrate that Sodium benzoate damages kidney structure and function and is a nephrotoxic substance. Atriplex halimus was able to improve the renal damage as an antioxidant and a nephroprotective agent.

Basil (Ocimum basilicum L.) and/or Celery (Apium graveolens L.) Leaves Aqueous Extracts Role in Opposition to Drinking Contaminated Water Induced Male Rats Urinary Stones and Renal Deteriorations

Aims: The current research was designed to explore the role of basil and/or celery leaves aqueous extracts against urinary stones (urolithiasis) and renal deteriorations induced by drinking water contaminated with ethylene glycol (EG) and ammonium chloride (AC) in male rats.&#x0D; Place and Duration of Study: The Medical Research Center of the Faculty of Pharmacy, Al-Azhar University, Cairo, Egypt. The experiment duration was 35 days, 7 days for acclimatization followed by 28 days experimentation.&#x0D; Methodology: Fifty-five adult male Sprague-Dawley rats were classified randomly into 5 groups of ten animals each, except urolithiatic control group which contained 15 rats. Rats were treated as follow: Group I: healthy control group (HCG), rats drank distilled water and received a placebo 1 ml distilled water daily by intra-gastric tube ; Group II: urolithiatic control group (UCG), rats drank distilled water containing ( 0.75% EG and 1% AC ) and the access to water was ad libitum and received 1 ml distilled water daily by intra-gastric tube.; Group III : urolithiatic rats supplemented with aqueous basil extract(U+ABE), rats drank distilled water containing ( 0.75% EG and 1% AC) and the access to water was ad libitum and supplemented with (200mg/kg body weight) aqueous basil extract daily by intra-gastric tube.; Group IV: urolithiatic rats supplemented with aqueous celery extract(U+ACE), rats drank distilled water containing ( 0.75% EG and 1% AC) and the access to water was ad libitum and supplemented with (200mg/kg body weight) aqueous celery extract daily by intra-gastric tube. ; Group V: urolithiatic rats supplemented with aqueous basil and celery extract(U+ABE+ACE) , rats drank distilled water containing ( 0.75% EG and 1% AC) and the access to water was ad libitum and supplemented with (100mg/kg body weight) aqueous basil extract and (100mg/kg body weight) aqueous celery extract daily by intra-gastric tube. At the end of the study 28 days, 24 h urine samples were collected from each individual animal and then rats were sacrificed under sodium barbiturate anesthesia. Blood samples were collected from the hepatic portal vein, serum was separated for biochemical analyses. Kidney samples were separated for tissue homogenate preparation, urinary bladder and ureters were separated and opened to collect urinary calculi.&#x0D; Results: Research results documented that basil and celery aqueous extracts contain significant amount of active constituents including flavonoids and polyphenols. Drinking water contaminated with EG and AC caused significant decrease (p≤0.01) in urine volume, pH, urinary and renal magnesium levels with significant increase (p≤0.01) in urinary and renal calcium, phosphate and oxalate levels. It also caused significant increase in kidney function tests [serum creatinine, uric acid, urea, as well as cystatin C] levels .Also renal enzyme activities of [acidic phosphatase (ACP), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP)] activities were significantly increased (p≤0.01) with significant decrease in renal lactate dehydrogenase (LDH) activity. Water contamination also induced renal mitochondrial dysfunction (decreased complex-1 activity), apoptosis (increased caspase-3 activity) in association with a state of renal oxidative stress [increased renal malondialdehyde (MDA) level related to decreased renal reduced glutathione (GSH)level and superoxide dismutase (SOD) activity].Inflammation [increased renal tumor necrosis factor- alpha (TNF- α) and interleukin 18 (IL-18)] with suppressed immune function [decreased serum immunoglobulin (IgG and IgM)] levels were observed in urolithiatic control group. As a result of biochemical changes resulted from EG and AM administration mineral precipitation and urinary stones formation was observed in urolithiatic control group. Oral administration of aqueous basil and /or celery extracts to urolithiatic rats improved urine analysis parameters, renal functions, renal enzymes activities and mitochondrial function. Aqueous extracts also counteracted renal oxidative stress, inflammation, suppressed immune response and urinary stones formation.&#x0D; Conclusion: Research results proved that aqueous basil and/or celery extracts counteracted and ameliorated urinary stones formation and renal deteriorations associated with drinking water contaminated with EG and AC due to their content of active constituents including flavonoids and polyphenols. The most significant improvements were recorded in the group supplemented with both extracts.

Prognostic value of the combined variability of mean platelet volume and neutrophil percentage for short-term clinical outcomes of sepsis patients

ABSTRACT Introduction In this single center retrospective cohort study, 784 patients with sepsis were enrolled and followed up for at least 30 days. The selected endpoint was an all-cause mortality event. Method The relationship between MPV-CV + NEU%-CV and all-cause mortality (in-hospital and 30-day) was analyzed by categorizing the patients into four groups according to MPV-CV and NEU%-CV values. For in-hospital mortality, a significantly higher risk of mortality was observed in patients with an MPV-CV ≥ 15.00% + NEU%-CV ≥ 16.00% than in patients of the other groups (P < 0.001). After adjustment for age, sex, body mass index (BMI), infection site, Acute Physiology and Chronic Health Evaluation (APACHE) II score, Sequential Organ Failure Assessment (SOFA) score, use of vasoactive drugs, mechanical ventilation and renal replacement therapy (RRT), hematocrit, albumin, procalcitonin (PCT), and lactate, logistic regression analysis revealed that an MPV-CV ≥ 15.00% + NEU%-CV ≥ 16.00% was an independent predictive factor for in-hospital mortality [adjusted model: odds ratio (OR) = 4.48, 95% CI = 2.92–6.88, P = 0.001]. Results After adjustment for age, sex, BMI, infection site, APACHE II score, SOFA score, hematocrit, albumin, PCT, lactate, and the use of vasoactive drugs, mechanical ventilation, and RRT, Cox proportional-hazards regression model revealed that an MPV-CV ≥ 15.00% + NEU%-CV ≥ 16.00% was an independent predictive factor for 30-day mortality [adjusted model 1: hazard ratio (HR) = 7.69, 95% CI = 4.15–14.24, P < 0.001; adjusted model 2: HR = 4.07, 95% CI = 2.50–6.62, P < 0.001]. Conclusion The combination of MPV-CV and NEU%-CV provides a good prognostic value and is a strong independent predictor of short-term clinical outcomes in patients with sepsis. An MPV-CV ≥ 15.00% + NEU%-CV ≥ 16.00% is significantly associated with adverse short-term clinical outcomes. Trial registration number is XJTU2AF2016LSY-04, the registration date is December 2018.

L-glutamine supplementation exerts cardio-renal protection in estrogen-progestin oral contraceptive-treated female rats

Glycogen and lipid disruptions represent a spectrum of metabolic disorders that are crucial risk factors for cardiovascular disease in estrogen-progestin oral contraceptive (COC) users. l-glutamine (GLN) has been shown to exert a modulatory effect in metabolic disorders-related syndromes. We therefore hypothesized that GLN supplementation would protect against myocardial and renal glycogen-lipid mishandling in COC-treated animals by modulation of Glucose-6-phosphate dehydrogenase (G6PD) and xanthine oxidase (XO) activities. Adult female Wistar rats were randomly allotted into control, GLN, COC and COC + GLN groups (six rats per group). The groups received vehicle (distilled water, p.o.), GLN (1 g/kg), COC containing 1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel and COC plus GLN respectively, daily for 8 weeks. Data showed that treatment with COC led to metabolically-induced obesity with correspondent increased visceral and epicardial fat mass. It also led to increased plasma, myocardial and renal triglyceride, free fatty acid, malondialdehyde (MDA), XO activity, uric acid content and decreased glutathione content and G6PD activity. In addition, COC increased myocardial but not renal glycogen content, and increased myocardial and renal glycogen synthase activity, increased plasma and renal lactate production and plasma aspartate transaminase/alanine aminotransferase (AST/ALT) ratio. However, these alterations were attenuated when supplemented with GLN except plasma AST/ALT ratio. Collectively, the present results indicate that estrogen-progestin oral contraceptive causes metabolically-induced obesity that is accompanied by differential myocardial and renal metabolic disturbances. The findings also suggest that irrespective of varying metabolic phenotypes, GLN exerts protection against cardio-renal dysmetabolism by modulation of XO and G6PD activities.

High Intrarenal Lactate Production Inhibits the Renal Pseudohypoxic Response to Acutely Induced Hypoxia in Diabetes.

Intrarenal hypoxia develops within a few days after the onset of insulinopenic diabetes in an experimental animal model (ie, a model of type-1 diabetes). Although diabetes-induced hypoxia results in increased renal lactate formation, mitochondrial function is well maintained, a condition commonly referred to as pseudohypoxia. However, the metabolic effects of significantly elevated lactate levels remain unclear. We therefore investigated in diabetic animals the response to acute intrarenal hypoxia in the presence of high renal lactate formation to delineate mechanistic pathways and compare these findings to healthy control animals. Hyperpolarized 13C-MRI and blood oxygenation level–dependent 1H-MRI was used to investigate the renal metabolism of [1-13C]pyruvate and oxygenation following acutely altered oxygen content in the breathing gas in a streptozotocin rat model of type-1 diabetes with and without insulin treatment and compared with healthy control rats. The lactate signal in the diabetic kidney was reduced by 12%–16% during hypoxia in diabetic rats irrespective of insulin supplementation. In contrast, healthy controls displayed the well-known Pasteur effect manifested as a 10% increased lactate signal following reduction of oxygen in the inspired air. Reduced expression of the monocarboxyl transporter-4 may account for altered response to hypoxia in diabetes with a high intrarenal pyruvate-to-lactate conversion. Reduced intrarenal lactate formation in response to hypoxia in diabetes shows the existence of a different metabolic phenotype, which is independent of insulin, as insulin supplementation was unable to affect the pyruvate-to-lactate conversion in the diabetic kidney.

Renal Tubular Cell Mitochondrial Dysfunction Occurs Despite Preserved Renal Oxygen Delivery in Experimental Septic Acute Kidney Injury.

To explain the paradigm of significant renal functional impairment despite preserved hemodynamics and histology in sepsis-induced acute kidney injury. Prospective observational animal study. University research laboratory. Male Wistar rats. Using a fluid-resuscitated sublethal rat model of fecal peritonitis, changes in renal function were characterized in relation to global and renal hemodynamics, and histology at 6 and 24 hours (n = 6-10). Sham-operated animals were used as comparison (n = 8). Tubular cell mitochondrial function was assessed using multiphoton confocal imaging of live kidney slices incubated in septic serum. By 24 hours, serum creatinine was significantly elevated with a concurrent decrease in renal lactate clearance in septic animals compared with sham-operated and 6-hour septic animals. Renal uncoupling protein-2 was elevated in septic animals at 24 hours although tubular cell injury was minimal and mitochondrial ultrastructure in renal proximal tubular cells preserved. There was no significant change in global or renal hemodynamics and oxygen delivery/consumption between sham-operated and septic animals at both 6- and 24-hour timepoints. In the live kidney slice model, mitochondrial dysfunction was seen in proximal tubular epithelial cells incubated with septic serum with increased production of reactive oxygen species, and decreases in nicotinamide adenine dinucleotide and mitochondrial membrane potential. These effects were prevented by coincubation with the reactive oxygen species scavenger, 4-hydroxy-2,2,6,6-tetramethyl-piperidin-1-oxyl. Renal dysfunction in sepsis occurs independently of hemodynamic instability or structural damage. Mitochondrial dysfunction mediated by circulating mediators that induce local oxidative stress may represent an important pathophysiologic mechanism.

Histopathological findings of renal tissue induced by oxidative stress due to different concentrations of fluoride.

It has been reported that excessive intake of fluoride can induce renal lesions. However, its pathogenesis is still less understood. Therefore, this study was conducted to investigate oxidative damage and the relationships between the oxidative damage and renal lesions in fluoride-treated mice by using the methods of histopathology, biochemistry, flow cytometry and quantitative real-time polymerase chain reaction (qRT-PCR). A total of 240 ICR mice were randomly divided into four equal groups (sodium fluoride was given orally at the dose of 0, 12, 24 and 48 mg/kg body weight for 42 days, respectively). We found that fluoride in excess of 12 mg/kg induced renal oxidative damage, which was characterized by increasing the levels of reactive oxygen species (ROS) production and contents of malondialdehyde (MDA) and protein carbonyls (PC), and decreasing the abilities of anti-superoxide anion (ASA) and anti-hydroxyl radical (AHR), glutathione (GSH) content, as well as activities and mRNA expression levels of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GSH-Px). Concurrently, fluoride caused degeneration and necrosis of the tubular cells, renal tubular hyaline casts and glomeruli swelling, which were consistent with the alteration of renal function parameters including elevated contents of serum creatinine (Cr), serum uric acid (UA), blood urea nitrogen (BUN), and the activities of urinary N-acetyl-b-D-glucosaminidase (NAG), renal lactate dehydrogenase (LDH), and reduced activities of sodium-potassium adenosine triphosphatase (Na+/K+-ATPase) and acid phosphatase (ACP) in the kidney. The above-mentioned results showed that fluoride in excess of 12 mg/kg induced renal oxidative damage, which then caused renal lesions and dysfunctions. These findings also clearly demonstrated that oxidative damage is one of the mechanisms of fluoride-induced renal lesions and dysfunctions.

Hyperbaric oxygen therapy reduces renal lactate production.

Intrarenal hypoxia is an acknowledged factor contributing to the development of diabetic nephropathy. Hyperbaric oxygen (HBO) therapy is a well‐known adjuvant treatment for several medical conditions, such as decompression sickness, infections, and wound healing. The underlying metabolic response of HBO is largely unknown. In this study, we investigated the effect of HBO on the intrarenal metabolic alteration in diabetes. Hyperpolarized [1‐13C]pyruvate MRI was performed to assess intrarenal energy metabolism in normoglycemic controls and short‐term (2 weeks) streptozotocin‐induced diabetic rats with and without HBO for five consecutive days. HBO therapy blunted intrarenal lactate production, 3 days after the therapy, in both normoglycemic controls and diabetic rats without affecting either lactate dehydrogenase mRNA expression or activity. HBO therapy reduced lactate formation in both normoglycemic and hyperglycemic rats. These findings support hyperpolarized [1‐13C]pyruvate MRI as a novel method for monitoring HBO therapy via the pyruvate to lactate conversion.

Protein-Protein Interaction between Sodium-Coupled Monocarboxylate Transporter 1 (SMCT1) and PDZ Domain-Containing Ring Finger Domain 3 (PDZRN3)

Sodium-coupled monocarboxylate transporters (SMCTs) are membrane proteins which transport lactate on the apical side of kidney. In addition to renal lactate reabsorption, it is known that both SMCTs and urate/anion transporter1 (URAT1) bind to PDZK1 and that SMCTs and URAT1 functionally cooperate to transport urate. This indicates that these transporters reabsorb urate by exchange for sodium. Our recent study revealed that SMCT1 (SLC5A8), a higher-affinity transporter than SMCT2 (SLC5A12), bound to PDZ domain-containing RING finger domain 3 (PDZRN3) in a yeast two hybrid screening. But there is less information available on the interaction between SMCT1 and PDZRN3. In this study, we elucidated this protein-protein interaction between them to resolve the regulation mechanism of serum urate level. We performed coimmunoprecipitation study to confirm the binding between SMCT1 and PDZRN3, and performed [3H] nicotinate uptake study to reveal whether there was a functional change by this binding, using HEK293 cells transiently transfected with SMCT1, its mutant lacking the PDZ motif and PDZRN3. Coimmunoprecipitation study revealed that the wild type SMCT1, but not its mutant lacking the SMCT1 C-terminal PDZ motif, directly bound to PDZRN3. In uptake study, there was no significant difference in amount of nicotinate uptake via SMCT1 and its mutant lacking the PDZ motif, in the presence of PDZRN3 or not. These results showed the protein-protein bind between SMCT1 and PDZRN3, but no functional interaction. This suggests that PDZRN3 regulates urate reabsorption via URAT1 by preventing SMCT1 from binding to PDZK1.

Antioxidant treatment attenuates lactate production in diabetic nephropathy.

The early progression of diabetic nephropathy is notoriously difficult to detect and quantify before the occurrence of substantial histological damage. Recently, hyperpolarized [1-13C]pyruvate has demonstrated increased lactate production in the kidney early after the onset of diabetes, implying increased lactate dehydrogenase activity as a consequence of increased nicotinamide adenine dinucleotide substrate availability due to upregulation of the polyol pathway, i.e., pseudohypoxia. In this study, we investigated the role of oxidative stress in mediating these metabolic alterations using state-of-the-art hyperpolarized magnetic resonance (MR) imaging. Ten-week-old female Wistar rats were randomly divided into three groups: healthy controls, untreated diabetic (streptozotocin treatment to induce insulinopenic diabetes), and diabetic, receiving chronic antioxidant treatment with TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl) via the drinking water. Examinations were performed 2, 3, and 4 wk after the induction of diabetes by using a 3T Clinical MR system equipped with a dual tuned 13C/1H-volume rat coil. The rats received intravenous hyperpolarized [1-13C]pyruvate and were imaged using a slice-selective 13C-IDEAL spiral sequence. Untreated diabetic rats showed increased renal lactate production compared with that shown by the controls. However, chronic TEMPOL treatment significantly attenuated diabetes-induced lactate production. No significant effects of diabetes or TEMPOL were observed on [13C]alanine levels, indicating an intact glucose-alanine cycle, or [13C]bicarbonate, indicating normal flux through the Krebs cycle. In conclusion, this study demonstrates that diabetes-induced pseudohypoxia, as indicated by an increased lactate-to-pyruvate ratio, is significantly attenuated by antioxidant treatment. This demonstrates a pivotal role of oxidative stress in renal metabolic alterations occurring in early diabetes.

Structure and Function of the Kidney in Septic Shock. A Prospective Controlled Experimental Study.

It is unclear how septic shock causes acute kidney injury (AKI) and whether this is associated with histological change. We aimed to determine the nature and extent of changes in renal structure and function over time in an ovine model of septic shock. Fifteen sheep were instrumented with a renal artery flow probe and renal vein cannula. Ten were given intravenous Escherichia coli to induce septic shock, and five acted as controls. Animals were mechanically ventilated for 48 hours, while receiving protocol-guided parenteral fluids and a norepinephrine infusion to maintain mean arterial pressure. Renal biopsies were taken every 24 hours or whenever animals were oliguric for 2 hours. A renal pathologist, blinded to tissue source, systematically quantified histological appearance by light and electron microscopy for 31 prespecified structural changes. Sheep given E. coli developed septic shock, oliguria, increased serum creatinine, and reduced creatinine clearance (AKI), but there were no changes over time in renal blood flow between groups (P > 0.30) or over time within groups (P > 0.50). Renal oxygen consumption increased only in nonseptic animals (P = 0.01), but there was no between-group difference in renal lactate flux (P > 0.50). There was little structural disturbance in all biopsies and, although some cellular appearances changed over time, the only difference between septic and nonseptic animals was mesangial expansion on electron microscopy. In an intensive care-supported model of gram-negative septic shock, early AKI was not associated with changes in renal blood flow, oxygen delivery, or histological appearance. Other mechanisms must contribute to septic AKI.

Detection of localized changes in the metabolism of hyperpolarized gluconeogenic precursors 13 C-lactate and 13 C-pyruvate in kidney and liver.

The purpose of this study was to characterize tissue-specific alterations in metabolism of hyperpolarized (HP) gluconeogenic precursors 13 C-lactate and 13 C-pyruvate by rat liver and kidneys under conditions of fasting or insulin-deprived diabetes. Seven normal rats were studied by MR spectroscopic imaging of both HP 13 C-lactate and 13 C-pyruvate in both normal fed and 24 h fasting states, and seven additional rats were scanned after induction of diabetes by streptozotocin (STZ) with insulin withdrawal. Phosphoenolpyruvate carboxykinase (PEPCK) expression levels were also measured in liver and kidney tissues of the STZ-treated rats. Multiple sets of significant signal modulations were detected, with graded intensity in general between fasting and diabetic states. An approximate two-fold reduction in the ratio of 13 C-bicarbonate to total 13 C signal was observed in both organs in fasting. The ratio of HP lactate-to-alanine was markedly altered, ranging from a liver-specific 54% increase in fasting, to increases of 69% and 92% in liver and kidney, respectively, in diabetes. Diabetes resulted in a 40% increase in renal lactate signal. STZ resulted in 5.86-fold and 2.73-fold increases in PEPCK expression in liver and kidney, respectively. MRI of HP 13 C gluconeogenic precursors may advance diabetes research by clarifying organ-specific roles in abnormal diabetic metabolism. Magn Reson Med 77:1429-1437, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Acute renal denervation decreases lactate production in the kidney cortex in experimental septic shock

The kidney is not considered a source of lactate during septic shock. Renal lactate metabolism, however, is complex with consumption and production occurring simultaneously. As β2 stimulation during endotoxemia results in increased lactate production in the muscle [1], lactate formation in the renal cortex may result from sympathetic stimulation as well.