Disorder of fatty acid metabolism in the kidney of PAN-induced nephrotic rats

Effects of Exercise Training on Mitochondrial Fatty Acid β-Oxidation in the Kidneys of Dahl Salt-Sensitive Rats

Exercise training (Ex) has anti-hypertensive and renal protective effects. In this study, we investigate the effects of Ex on mitochondrial fatty acid metabolism in the kidneys of Dahl salt-sensitive (Dahl-S) rats fed a high-salt (HS) diet. Eight-week-old, male Dahl-S rats were divided into three groups: (1) normal-salt diet, sedentary (NS-Sed), (2) HS diet, sedentary (HS-Sed), and (3) HS-Ex. The NS and HS groups were fed a diet containing 0.6% and 8% NaCl, respectively. The HS-Ex group performed treadmill running for 8 weeks (5 days/week; 60 min/day at 16-20 m/min, 0% gradient). Renal function and the expression of enzymes and regulators of β-oxidation and electron transport chain (ETC) complexes were assessed. HS increased systolic blood pressure and proteinuria, and Ex ameliorated these defects. HS also reduced creatinine clearance, and Ex ameliorated it. HS reduced the renal expression of enzymes of β-oxidation (carnitine palmitoyltransferase type I (CPTI) and acyl-CoA dehydrogenases (CADs)) and the related transcription factors peroxisome proliferator-activated receptor α (PPARα) and PPARγ-coactivator-1α (PGC-1α), and Ex restored this. HS also reduced the renal expression of enzymes in ETC complexes, and Ex restored this expression. Ex ameliorates HS-induced renal damage by upregulating enzymes involved in fatty acid β-oxidation and ETC complexes via increases in PPAR-α and PGC-1α expressions in the kidneys of Dahl-S rats. These results suggest that Ex may have beneficial effects on HS-induced mitochondrial dysfunction in the kidney.

Sodium acetate prevents nicotine-induced cardiorenal dysmetabolism through uric acid/creatine kinase-dependent pathway

BACKGROUND

Cigarette smoking or nicotine replacement therapy has been associated with cardiometabolic disorders (CMD). Hyperuricemia has been implicated in the pathogenesis of CMD and cardiorenal dysfunction. Gut microbiota-derived short chain fatty acids (SCFAs) have been reported to have beneficial glucoregulatory and cardiorenal protective effects. This study aimed at investigating the effect of acetate, a gut-derived SCFA, on nicotine-induced CMD and associated cardiorenal dysmetabolism.

MATERIALS AND METHOD

Twenty-four male Wistar rats (n = 6/group) were grouped as: vehicle (p.o.), nicotine-exposed (1.0 mg/kg; p.o.), and sodium acetate-treated (200 mg/kg; p.o.) with or without nicotine exposure daily for 6 weeks. Glucose regulation was evaluated by oral glucose tolerance test and homeostatic model assessment of insulin resistance. Cardiac and renal triacylglycerol (TG), lactate, nitric oxide (NO), uric acid (UA) levels, lactate dehydrogenase (LDH), creatine kinase (CK), adenosine deaminase (ADA), and xanthine oxidase (XO) activities were measured.

RESULTS

The CMD were confirmed in the nicotine-exposed rats that exhibited lower body weight, insulin resistance, endothelial dysfunction, glucose intolerance, increased cardiac and renal TG, TG/HDL-cholesterol, UA, lactate, lipid peroxidation, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, LDH, CK, ADA and XO activities. Concurrent treatment with acetate prevented nicotine-induced glucometabolic and cardiorenal alterations.

CONCLUSION

In summary, these results implied that nicotine exposure caused glucometabolic dysregulation and surplus lipid deposit in the heart and kidney through increased UA production and CK activity. Therefore, oral acetate administration prevents cardiorenal lipotoxicity and glucometabolic dysregulation via suppression of UA production and CK activity in nicotine-exposed rats.

Impact of CYP3A4/5 and ABCB1 polymorphisms on tacrolimus exposure and response in pediatric primary nephrotic syndrome

Aim: To evaluate the impact of CYP3A4*1G, CYP3A5*3 and ABCB1-C3435T polymorphisms on tacrolimus concentrations, efficacy and tolerance in pediatric primary nephrotic syndrome. Methods: Dose-adjusted concentrations (C₀/D), daily dose, frequency and time to relapse, cumulative remission days, and adverse reactions in 65 Chinese patients with various genotypes were retrospectively collected and compared. Results: C₀/D increased in CYP3A4*1/*1, CYP3A5*3/*3 and CYP3A4*1/*1-3A5*3/*3 diplotype carriers by 38.4, 69.7 and 40.9% compared with CYP3A4*1/*1G, CYP3A5*1/*3 and noncarriers, respectively. Recurrence risks were decreased in CYP3A4*1/*1 (0.43 of hazard ratio to *1/*1G) and CYP3A5*3/*3 carriers (0.43 of hazard ratio to *1/*3). None of polymorphisms was linked to adverse reactions. Conclusion: The genotypes of CYP3A4*1G and CYP3A5*3 rather than ABCB1-C3435T potentially predicted tacrolimus exposure and clinical response in pediatric primary nephrotic syndrome.

Detecting serum and urine metabolic profile changes of CCl4-liver fibrosis in rats at 12 weeks based on gas chromatography-mass spectrometry

Liver fibrosis is caused by liver injury induced by a number of chronic liver diseases, including schistosome infection, hepatitis infection, metabolic disease, alcoholism and cholestasis. The tissue damage occurring after injury or inflammation of the liver is a reversible lesion; however, liver fibrosis has become a worldwide problem and poses a threat to human health. The development of an effective drug for the prevention and treatment of liver fibrosis is ongoing and uses information from different occurrences of liver fibrosis. In the present study, carbon tetrachloride (CCl₄)-induced metabonomic changes in serum and urine at 12 weeks were analyzed using gas chromatography-mass spectrometry (GC/MS) to investigate potential biomarkers. Liver fibrosis was induced in rats by subcutaneous injections of CCl₄ twice a week for 12 consecutive weeks. Histopathological changes were used to assess the successful production of a CCl₄-induced liver fibrosis model. Serum and urine samples from the two groups were collected at 12 weeks. The metabolic profile changes were analyzed by GC/MS alongside principal component analysis and orthogonal projections to latent structures. Metabolic profile studies indicated that the clustering of the two groups could be separated and seven metabolites in serum and five metabolites in urine were identified. In serum, the metabolites identified included isoleucine, L-malic acid, α-copper, carnitine, hippuric acid, glutaric acid and glucose. In urine 2-hydroxy butyric acid, isoleucine, N-acetyl-β-alanine, cytidine and corticoid were identified. The present study demonstrated that the pathogenesis of liver fibrosis may be associated with the dysfunction of a number of metabolic pathways, including glucose, amino acid, P450, fatty acid, nucleic acid, water-electrolyte and glutathione biosynthesis. Assessing potential biomarkers may therefore provide novel targets and theories for the innovation of novel drugs to prevent and cure liver fibrosis.

Kidneys: key modulators of high-density lipoprotein levels and function

PURPOSE OF REVIEW

The review will examine advances in our understanding of the role kidneys play in high-density lipoprotein (HDL) metabolism and the effect on levels, composition, and function of HDL particles.

RECENT FINDINGS

Components of the HDL particles can cross the glomerular filtration barrier. Some of these components, including apolipoproteins and enzymes involved in lipid metabolism, are taken up by the proximal tubule and degraded, modified, salvaged/returned to the circulation, or lost in the urine. Injury of the glomerular capillaries or tubules can affect these intrarenal processes and modify HDL. Changes in the plasma and urine levels of HDL may be novel markers of kidney damage or mechanism(s) of kidney disease.

SUMMARY

The kidneys have a significant role in the metabolism of individual HDL components, which in turn modulate HDL levels, composition, and functionality of HDL particles. These intrarenal effects may be useful markers of kidney damage and have consequences on kidney-related perturbations in HDL.

Effect of clofibrate on fatty acid metabolism in the kidney of puromycin-induced nephrotic rats

BACKGROUND

Proteinuria plays an essential role in the progression of tubulointerstitial damage, which causes end-stage renal disease. An increased load of fatty acids bound to albumin reabsorbed into proximal tubular epithelial cells (PTECs) contributes to tubulointerstitial damage. Fibrates, agonists of peroxisome proliferator-activated receptor α (PPARα), have renoprotective effects against proteinuria whereas the effects of these compounds on fatty acid metabolism in the kidney are still unknown. Therefore, the present study examined whether the renoprotective effects of clofibrate were associated with improvement of fatty acid metabolism in puromycin aminonucleoside (PAN)-induced nephrotic rats.

METHODS

Rats were allocated to the control, PAN or clofibrate-treated PAN group. Biochemical parameters, renal injury and changes in fatty acid metabolism were studied on day14.

RESULTS

PAN increased proteinuria, lipid accumulation in PTECs, excretions of N-acetyl-β-D-glucosaminidase (NAG) and 8-hydroxydeoxyguanosine (8OHdG) and the area of caspase 3-positive tubular cells. It decreased renal expressions of medium-chain acyl-CoA dehydrogenase (MCAD), cytochrome P450 (CYP)4A, peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and estrogen-related receptor α (ERRα) without change of the expression of PPARα. Clofibrate reduced proteinuria, lipid accumulation, NAG excretion and the area of caspase 3-positive tubular cells. However, albumin excretion was not reduced and 8OHdG excretion was increased. Clofibrate minimized changes in MCAD, CYP4A, PGC-1α and ERRα expressions with increased PPARα, very long-chain acyl-CoA dehydrogenase (VLCAD) and long-chain acyl-CoA dehydrogenase (LCAD) expressions.

CONCLUSION

Clofibrate is protective against renal lipotoxicity in PAN nephrosis. This study indicates that clofibrate has renoprotective effects through maintaining fatty acid metabolism in the kidney of PAN-induced nephrotic rats.

Estrogen-related receptor (ERR) γ protects against puromycin aminonucleoside-induced podocyte apoptosis by targeting PI3K/Akt signaling

Accumulating evidence has shown that podocyte apoptosis is of vital importance for the development of glomerulosclerosis and progressive loss of renal function. However, the molecular mechanisms leading to podocyte apoptosis are still elusive. In this study, we investigated the role of estrogen-related receptor (ERR) γ in podocyte apoptosis, as well as the underlying mechanisms. Treatment of PAN caused a dose- and time-dependent podocyte apoptosis in line with a significant downregulation of ERRγ. Interestingly, the occurrence of ERRγ downregulation appeared earlier than the onset of cell apoptosis, suggesting a potential that ERRγ reduction triggered apoptotic response in podocyte. To test this hypothesis, ERRγ siRNA was administered to the podocytes. Strikingly, ERRγ silencing resulted in a significant cell apoptosis accompanied with increased injury markers of B7-1 and cathepsin L and decreased podocyte protein nephrin. In contrast, overexpression of ERRγ remarkably attenuated PAN-induced cell apoptosis. Moreover, ERRγ overexpression stimulated PI3K/Akt signaling pathway evidenced by increased expression of PI3K subunits p85α and p110α and phosphorylated Akt. Importantly, a specific PI3K inhibitor LY294002 entirely reversed the anti-apoptotic effect of ERRγ following PAN treatment. Finally, we observed a striking downregulation of ERRγ in PAN-treated rat kidneys, suggesting that our cell model replicated the in vivo condition. Taken together, these data highly suggested that ERRγ played a novel role in modulating podocyte apoptosis by targeting PI3K/Akt signaling pathway.

TLR-mediated albuminuria needs TNFα-mediated cooperativity between TLRs present in hematopoietic tissues and CD80 present on non-hematopoietic tissues in mice

Transient albuminuria induced by pathogen-associated molecular patterns (PAMPs) in mice through engagement of Toll-like receptors (TLRs) is widely studied as a partial model for some forms of human nephrotic syndrome (NS). In addition to TLRs, CD80 has been shown to be essential for PAMP-mediated albuminuria. However, the mechanistic relationships between TLRs, CD80 and albuminuria remain unclear. Here, we show that albuminuria and CD80-uria induced in mice by many TLR ligands are dependent on the expression of TLRs and their downstream signalling intermediate MyD88 exclusively in hematopoietic cells and, conversely, on CD80 expression exclusively in non-hematopoietic cells. TNFα is crucial for TLR-mediated albuminuria and CD80-uria, and induces CD80 expression in cultured renal podocytes. IL-10 from hematopoietic cells ameliorates TNFα production, albuminuria and CD80-uria but does not prevent TNFα-mediated induction of podocyte CD80 expression. Chitohexaose, a small molecule originally of parasite origin, mediates TLR4-dependent anti-inflammatory responses, and blocks TLR-mediated albuminuria and CD80-uria through IL-10. Thus, TNFα is a prominent mediator of renal CD80 induction and resultant albuminuria in this model, and small molecules modulating TLR-mediated inflammatory activation might have contributory or adjunct therapeutic potential in some contexts of NS development.

Summary: Systemic TNFα mediates myeloid cell and podocyte cross-talk to cause LPS-induced mouse microalbuminuria, a partial model of human nephrotic syndrome, pointing to potential adjunct therapeutic approaches.

Efficacy of Shenzhuo formula on diabetic kidney disease: a retrospective study

OBJECTIVE

To observe the efficacy of a traditional Chinese medicine, Shenzhuo formula, on patients with diabetic kidney disease (DKD).

METHODS

Eighty-eight outpatients with DKD were enrolled. Changes in estimated glomerular filtration rate (eGFR), creatinine clearance, serum creatinine, blood-urea-nitrogen, albuminuria, glycosylated hemoglobin (HbA1C), blood pressure, and lipid profile were measured and analyzed before and after intervention with Shenzhuo formula for 1, 3, 6, 9, 12, and 18 months.

RESULTS

Compared with the baseline amounts, serum creatinine decreased, and eGFR and creatinine clearance increased, significantly after intervention for 1, 3, 6, 9, 12, and 18 months (all P < 0.05). Mean eGFR increased by 2.11 mL/min per 1.73 m²/y after 18-month treatment. Urinary protein at 24 h decreased significantly after 1, 3, 9, and 12 months (P < 0.05). HbA1C decreased significantly (P < 0.05) after 3, 6, 9, 12, and 18 months, and systolic blood pressure decreased significantly (P < 0.05) after 1, 3, and 6 months. Total cholesterol decreased significantly (P < 0.05) after 1, 3, 6, and 18 months. Triglyceride and low-density lipoprotein-cholesterol decreased significantly (P < 0.05) after 1 and 3 months.

CONCLUSION

Shenzhuo formula can improve eGFR and possibly slow DKD progression. Shenzhuo formula can also lower HbA1C, lipid levels and blood pressure.

Yi Qi Qing Re Gao formula ameliorates puromycin aminonucleoside-induced nephrosis by suppressing inflammation and apoptosis

Background

Yi Qi Qing Re Gao (YQQRG) formula is a traditional Chinese herbal medicine used to treat chronic nephritis. This study was designed to evaluate the underlying mechanism in the use of YQQRG formula to treat nephrosis induced by puromycin aminonucleoside (PAN).

Methods

Thirty-six male Wistar rats were randomly divided into 3 groups of 12 rats each: a sham group, a vehicle-treated PAN model group (PAN), and a group treated with YQQRG (PAN + YQQRG). The PAN model was established by a single intravenous injection of PAN at a dose of 40 mg/kg body weight; rats in the sham group received the same volume of saline. Twenty-four hour urinary protein was measured 0, 3, 5, 10, and 15 days after the injection. The rats were sacrificed on day 10 and day 15 and the serum lipid profile examined. The renal cortex of each rat was stained with periodic acid–Schiff reagent and the pathologic alterations and ultrastructural changes were examined by transmission electron microscopy. In situ cell apoptosis was detected by a terminal deoxynucleotidyl transferase-mediated uridine 5′-triphosphate-biotin nick end-labeling (TUNEL) assay. Transcriptive levels of inflammatory markers and molecules associated with apoptosis were detected by a real-time polymerase chain reaction and expression of proteins was examined by either immunohistochemistry or Western blot analysis.

Results

YQQRG significantly decreased urinary protein level, and lowered serum lipid level. YQQRG also attenuated histologic lesions in the rat kidneys. Activation of inflammatory markers was largely restored by the administration of YQQRG. TUNEL assay showed that YQQRG decreased the number of apoptotic cells. Both mRNA and protein levels of caspase-3 were significantly reduced in the group treated with YQQRG, whereas expression of the Bcl-2 protein increased in the YQQRG group.

Conclusions

YQQRG alleviated kidney injury in PAN-treated rats, possibly through anti-inflammatory and anti-apoptotic effects.

Altered renal lipid metabolism and renal lipid accumulation in human diabetic nephropathy

Animal models link ectopic lipid accumulation to renal dysfunction, but whether this process occurs in the human kidney is uncertain. To this end, we investigated whether altered renal TG and cholesterol metabolism results in lipid accumulation in human diabetic nephropathy (DN). Lipid staining and the expression of lipid metabolism genes were studied in kidney biopsies of patients with diagnosed DN (n = 34), and compared with normal kidneys (n = 12). We observed heavy lipid deposition and increased intracellular lipid droplets. Lipid deposition was associated with dysregulation of lipid metabolism genes. Fatty acid β-oxidation pathways including PPAR-α, carnitine palmitoyltransferase 1, acyl-CoA oxidase, and L-FABP were downregulated. Downregulation of renal lipoprotein lipase, which hydrolyzes circulating TGs, was associated with increased expression of angiopoietin-like protein 4. Cholesterol uptake receptor expression, including LDL receptors, oxidized LDL receptors, and acetylated LDL receptors, was significantly increased, while there was downregulation of genes effecting cholesterol efflux, including ABCA1, ABCG1, and apoE. There was a highly significant correlation between glomerular filtration rate, inflammation, and lipid metabolism genes, supporting a possible role of abnormal lipid metabolism in the pathogenesis of DN. These data suggest that renal lipid metabolism may serve as a target for specific therapies aimed at slowing the progression of glomerulosclerosis.