Aortic stiffness is associated with vascular calcification and remodeling in a chronic kidney disease rat model

Increased aortic pulse-wave velocity (PWV) reflects increased arterial stiffness and is a strong predictor of cardiovascular risk in chronic kidney disease (CKD). We examined functional and structural correlations among PWV, aortic calcification, and vascular remodeling in a rodent model of CKD, the Lewis polycystic kidney (LPK) rat. Hemodynamic parameters and beat-to-beat aortic PWV were recorded in urethane-anesthetized animals [12-wk-old hypertensive female LPK rats (n = 5)] before the onset of end-stage renal disease and their age- and sex-matched normotensive controls (Lewis, n = 6). Animals were euthanized, and the aorta was collected to measure calcium content by atomic absorption spectrophotometry. A separate cohort of animals (n = 5/group) were anesthetized with pentobarbitone sodium and pressure perfused with formalin, and the aorta was collected for histomorphometry, which allowed calculation of aortic wall thickness, medial cross-sectional area (MCSA), elastic modulus (EM), and wall stress (WS), size and density of smooth muscle nuclei, and relative content of lamellae, interlamellae elastin, and collagen. Mean arterial pressure (MAP) and PWV were significantly greater in the LPK compared with Lewis (72 and 33%, respectively) animals. The LPK group had 6.8-fold greater aortic calcification, 38% greater aortic MCSA, 56% greater EM/WS, 13% greater aortic wall thickness, 21% smaller smooth muscle cell area, and 20% less elastin density with no difference in collagen fiber density. These findings demonstrate vascular remodeling and increased calcification with a functional increase in PWV and therefore aortic stiffness in hypertensive LPK rats.     

Cardiac calcium dysregulation in mice with chronic kidney disease

Cardiovascular complications are leading causes of morbidity and mortality in patients with chronic kidney disease (CKD). CKD significantly affects cardiac calcium (Ca²⁺) regulation, but the underlying mechanisms are not clear. The present study investigated the modulation of Ca²⁺ homeostasis in CKD mice. Echocardiography revealed impaired fractional shortening (FS) and stroke volume (SV) in CKD mice. Electrocardiography showed that CKD mice exhibited longer QT interval, corrected QT (QTc) prolongation, faster spontaneous activities, shorter action potential duration (APD) and increased ventricle arrhythmogenesis, and ranolazine (10 µmol/L) blocked these effects. Conventional microelectrodes and the Fluo-3 fluorometric ratio techniques indicated that CKD ventricular cardiomyocytes exhibited higher Ca²⁺ decay time, Ca²⁺ sparks, and Ca²⁺ leakage but lower [Ca²⁺]_i transients and sarcoplasmic reticulum Ca²⁺ contents. The CaMKII inhibitor KN93 and ranolazine (RAN; late sodium current inhibitor) reversed the deterioration in Ca²⁺ handling. Western blots revealed that CKD ventricles exhibited higher phosphorylated RyR2 and CaMKII and reduced phosphorylated SERCA2 and SERCA2 and the ratio of PLB-Thr17 to PLB. In conclusions, the modulation of CaMKII, PLB and late Na⁺ current in CKD significantly altered cardiac Ca²⁺ regulation and electrophysiological characteristics. These findings may apply on future clinical therapies.     

Mechanisms and consequences of hypertriglyceridemia and cellular lipid accumulation in chronic kidney disease and metabolic syndrome

Hypertriglyceridemia and intracellular lipid overload are commonly present in both the chronic kidney disease (CKD) and metabolic syndrome. Hypertriglyceridemia in the metabolic syndrome arises mostly from increased lipoprotein synthesis, while that in the CKD is mainly caused by decreased catabolism. In metabolic syndrome, enhanced plasma levels of free fatty acids and triglyceride (TG) may lead to intracellular fatty acid accumulation in the kidney. However, the mechanisms by which intracellular lipid accumulation occurs in the dieased glomeruli have not been established. I provide evidence that binding/uptake of TG-rich very low-density lipoprotein by glomerular cells is increased in CKD, leading to increased endocytic accumulation of TG. I also provide evidence that cellular damage by fatty acid accumulation in the kidney is particularly severe in podocytes, leading to apoptosis and resulting in glomerulosclerosis. Collectively, these data bring new mechanistic insights into cellular lipid overload and lipotoxicity in CKD.     

Membrane lipid changes in erythrocytes, liver and kidney in acute and chronic experimental liver disease in rats

Lipid molecules in lipoprotein surfaces exchange with their counterparts in cell plasma membranes. In human or experimental liver disease, plasma lipoprotein surfaces are enriched in cholesterol and deficient in arachidonate; corresponding alterations occur in membrane lipids of erythrocytes. To determine whether similar changes take place in membranes of nucleated cells, the lipid content of plasma and of erythrocyte, liver and kidney membranes was measured in rats with acute (3-day) galactosamine-induced hepatitis or chronic (3-week) biliary obstruction. In both models of liver injury the cholesterol:phospholipid ratio in plasma and in erythrocytes was significantly increased (P less than 0.001). Although this ratio was also elevated in liver and kidney microsomes, only in liver microsomes of obstructed rats was the increase significant (P less than 0.001). However, the cholesterol:phospholipid ratio of kidney brush-border membranes, was significantly higher in bile-duct-ligated rats; presumably, compensating mechanisms limit cholesterol accumulation in intracellular membranes. Kidney brush-border membranes from obstructed rats were deficient in arachidonate as were plasma and erythrocytes. However, arachidonate levels were unchanged in kidney microsomes; renal delta 6-desaturase, the rate-limiting enzyme in the conversion of linoleic acid to arachidonic acid, was increased by 50% (P less than 0.001) and may have counteracted a reduced supply of exogenous lipoprotein arachidonate. We conclude that in experimental liver disease lipoprotein-induced lipid abnormalities can occur in renal membranes, although compensatory mechanisms may operate; the alterations seen, cholesterol accumulation and arachidonate depletion, would be expected to interfere with sodium transport and prostaglandin production, respectively. Our findings support the hypothesis that lipid abnormalities in kidney membranes contribute to the renal dysfunction which is a frequent complication of human liver disease.     

慢性肾炎大鼠的肠道菌群变化

目的 探究阳离子化牛血清白蛋白（C-BSA）慢性肾炎大鼠肠道菌群结构变化并对其代谢功能进行预测。方法 20只SD大鼠分为正常组和模型组各10只,模型组参照Border造模方法尾静脉注射C-BSA造模,6周后测定24 h尿蛋白、血清肌酐和尿素氮水平。取大鼠结肠和肾脏观察病理切片。收集大鼠粪样运用MiSeq平台进行16S rRNA测序。结果 正常组与模型组大鼠24 h尿蛋白含量、血清肌酐和尿素氮差异均存在统计学意义（均P<0.01）,模型组大鼠肾小球增大,毛细血管变窄,肠上皮损伤,发生炎性浸润。模型组大鼠普氏菌属、毛螺旋菌属相对丰度较高,且氨基酸代谢、维生素代谢和脂质代谢能力减弱。结论 C-BSA肾炎的发生不仅改变肠道菌群结构,而且影响机体代谢功能。     

Efficacy of benzbromarone in hyperuricemic patients associated with chronic kidney disease

We have retrospectively evaluated the uric acid control status and renal function changes over a period of up to 7 years in 35 patients with renal impairment who had stage 3 or higher chronic kidney disease (CKD; stage 3 in 32 patients, stage 4 in 2 patients, and stage 5 in 1 patient) associated with hyperuricemia and were receiving monotherapy with benzbromarone as an antihyperuricemic drug. Serum uric acid levels significantly decreased from 8.5 ± 0.9 to 6.1 ± 0.8 mg/dL at 6 months and were subsequently controlled at less than 7.0 mg/dL in most patients. Most patients received benzbromarone at a dose of 25-50 mg/day, whereas 150-200 mg/day was used in some patients with stage 4 or 5 CKD. No significant changes in estimated glomerular filtration rate (eGFR) from the baseline value of 46.2 ± 11.5 mL/minute/1.73 m(2) were found after benzbromarone therapy. Although the renal function impairment did not improve by reducing the serum uric acid levels with benzbromarone, the renal function did not deteriorate further on the therapy. These results suggest that benzbromarone is applicable to the management of hyperuricemia associated with renal impairment.     

Niacin improves renal lipid metabolism and slows progression in chronic kidney disease

Background

Mounting evidence points to lipid accumulation in the diseased kidney and its contribution to progression of nephropathy. We recently found heavy lipid accumulation and marked dysregulation of lipid metabolism in the remnant kidneys of rats with chronic renal failure (CRF). Present study sought to determine efficacy of niacin supplementation on renal tissue lipid metabolism in CRF.

Methods

Kidney function, lipid content, and expression of molecules involved in cholesterol and fatty acid metabolism were determined in untreated CRF (5/6 nephrectomized), niacin-treated CRF (50 mg/kg/day in drinking water for 12 weeks) and control rats.

Results

CRF resulted in hypertension, proteinuria, renal tissue lipid accumulation, up-regulation of scavenger receptor A1 (SR-A1), acyl-CoA cholesterol acyltransferase-1 (ACAT1), carbohydrate-responsive element binding protein (ChREBP), fatty acid synthase (FAS), acyl-CoA carboxylase (ACC), liver X receptor (LXR), ATP binding cassette (ABC) A-1, ABCG-1, and SR-B1 and down-regulation of sterol responsive element binding protein-1 (SREBP-1), SREBP-2, HMG-CoA reductase, PPAR-α, fatty acid binding protein (L-FABP), and CPT1A. Niacin therapy attenuated hypertension, proteinuria, and tubulo-interstitial injury, reduced renal tissue lipids, CD36, ChREBP, LXR, ABCA-1, ABCG-1, and SR-B1 abundance and raised PPAR-α and L-FABP.

Conclusions and general significance

Niacin administration improves renal tissue lipid metabolism and renal function and structure in experimental CRF.     

Interleukin-20 targets renal cells and is associated with chronic kidney disease

Interleukin (IL)-10 is an anti-inflammatory factor that suppresses renal fibrosis and improves renal function in CKD rats. IL-20 belongs to the IL-10 family; therefore, we sought to determine whether IL-20 is involved in CKD. CKD patients at stage five expressed significantly higher IL-20 in serum than controls. Immunohistochemical staining demonstrated that more IL-20 protein was expressed in the kidney tubular-epithelial cells, mesangial cells, and immune cells of CKD rats with a 5/6 nephrectomy. The lung, liver, and heart tissue of CKD rats also overexpressed IL-20. Thus, we treated two tubular epithelial cells, TKPTS and M-1 cells, with IL-20 to study its effects on CKD. IL-20 treatment induced apoptosis in these cells via caspase-3 activation. Incubating IL-20 with rat interstitial fibroblasts, NRK-49F cells, upregulated TGF-β1production, one key inducer for renal fibrogenesis. Therefore, IL-20 injured renal epithelial cells and induced fibroblasts to produce TGF-β1 that hastened the progression of CKD.     

Alterations of retinol-binding protein 4 species in patients with different stages of chronic kidney disease and their relation to lipid parameters

Retinol-binding protein 4 (RBP4) is elevated in patients with chronic kidney disease (CKD) and has been discussed as marker of kidney function. In addition to an elevated concentration, the existence of truncated RBP4 species, RBP4-L (truncated at last C-terminal leucine) and RBP4-LL (truncated at both C-terminal leucines), has been reported in serum of hemodialysis patients. Since little is known about the occurrence of RBP4 species during the progression of CKD it was the aim of this study to analyse this possible association. The presence of RBP4, RBP4-L, RBP4-LL and transthyretin (TTR) was assessed in serum of 45 healthy controls and 52 patients with stage 2-5 of CKD using ELISA and RBP4 immunoprecipitation with subsequent MALDI-TOF-MS analysis. A reduction of glomerular filtration rate was accompanied by a gradual elevation of RBP4 serum levels and relative amounts of RBP4-LL. Correlation analysis revealed a strong association of the RBP4-TTR ratio with parameters of lipid metabolism and with diabetes-related factors. In conclusion, RBP4 serum concentration and the appearance of RBP4-LL seem to be influenced by kidney function. Furthermore, the RBP4-TTR ratio may provide diagnostic potential with regard to metabolic complications in CKD patients.     

Quercetin and allopurinol ameliorate kidney injury in STZ-treated rats with regulation of renal NLRP3 inflammasome activation and lipid accumulation

Hyperuricemia, hyperlipidemia and inflammation are associated with diabetic nephropathy. The NLRP3 inflammasome-mediated inflammation is recently recognized in the development of kidney injury. Urate and lipid are considered as danger signals in the NLRP3 inflammasome activation. Although dietary flavonoid quercetin and allopurinol alleviate hyperuricemia, dyslipidmia and inflammation, their nephroprotective effects are currently unknown. In this study, we used streptozotocin (STZ)-induced diabetic nephropathy model with hyperuricemia and dyslipidemia in rats, and found over-expression of renal inflammasome components NLRP3, apoptosis-associated speck-like protein and Caspase-1, resulting in elevation of IL-1β and IL-18, with subsequently deteriorated renal injury. These findings demonstrated the possible association between renal NLRP3 inflammasome activation and lipid accumulation to superimpose causes of nephrotoxicity in STZ-treated rats. The treatment of quercetin and allopurinol regulated renal urate transport-related proteins to reduce hyperuricemia, and lipid metabolism-related genes to alleviate kidney lipid accumulation in STZ-treated rats. Furthermore, quercetin and allopurinol were found to suppress renal NLRP3 inflammasome activation, at least partly, via their anti-hyperuricemic and anti-dyslipidemic effects, resulting in the amelioration of STZ-induced the superimposed nephrotoxicity in rats. These results may provide a basis for the prevention of diabetes-associated nephrotoxicity with urate-lowering agents such as quercetin and allopurinol.     

Cardiac gene expression profile and lipid accumulation in response to starvation

Starvation induces many biochemical and histological changes in the heart; however, the molecular events underlying these changes have not been fully elucidated. To explore the molecular response of the heart to starvation, microarray analysis was performed together with biochemical and histological investigations. Serum free fatty acids increased twofold in both 16- and 48-h-fasted mice, and cardiac triglyceride content increased threefold and sixfold in 16- and 48-h-fasted mice, respectively. Electron microscopy showed numerous lipid droplets in hearts of 48-h-fasted mice, whereas fewer numbers of droplets were seen in hearts from 16-h-fasted mice. Expression of 11,000 cardiac genes was screened by microarrays. More than 50 and 150 known genes were detected by differential expression analysis after 16- and 48-h-fasts, respectively. Genes for fatty acid oxidation and gluconeogenesis were increased, and genes for glycolysis were decreased. Many other genes for metabolism, signaling/cell cycle, cytoskeleton, and tissue antigens were affected by fasting. These data provide a broad perspective of the molecular events occurring physiologically in the heart in response to starvation.     

Renalase in children with chronic kidney disease

Abstract

Background: Renalase is kidney-derived molecule initially considered as catecholamine-inactivating enzyme. However, recent studies suggest that renalase exerts potent cardio- and nephroprotective actions, not related to its enzymatic activity.

Purpose: To assess renalase level in children with chronic kidney disease (CKD).

Material and methods: Serum renalase, BMI, arterial stiffness, peripheral and central blood pressure, intima-media thickness (IMT), medications, and biochemical parameters were analyzed in 38 children with CKD (12.23?±?4.19?years) (stage G2-5). Control group consisted of 38 healthy children.

Results: In the study group, GFR was 25.74?±?8.94?mL/min/1.73 m²; 6 children were dialyzed; 26 had arterial hypertension. Renalase level was higher in the study group compared to control group (p?<?0.001). In CKD children renalase correlated (p?<?0.05) with BMI Z-score (r?=?–0.36), alfacalcidol dose (r?=?0.41), GFR (r?=?–0.69), hemoglobin (r?=?–0.48), total cholesterol (r?=?0.35), LDL-cholesterol (r?=?0.36), triglycerides (r?=?0.52), phosphate (r?=?0.35), calcium-phosphorus product (r?=?0.35), parathormone (r?=?0.58), and pulse wave velocity Z-score (r?=?0.42). In multivariate analysis GFR (β?=?–0.63, p?<?0.001), triglycerides (β?=?0.59, p?=?0.002), and alfacalcidol dose (β?=?–0.49, p?=?0.010) were determinants of renalase.

Conclusions: In children with CKD there is a strong correlation between renalase level and CKD stage. Furthermore, in these patients renalase does not correlate with blood pressure but may be a marker of arterial stiffness.     

Human embryonic mesenchymal stem cell-derived conditioned medium rescues kidney function in rats with established chronic kidney disease

Chronic kidney disease (CKD) is a major health care problem, affecting more than 35% of the elderly population worldwide. New interventions to slow or prevent disease progression are urgently needed. Beneficial effects of mesenchymal stem cells (MSC) have been described, however it is unclear whether the MSCs themselves or their secretome is required. We hypothesized that MSC-derived conditioned medium (CM) reduces progression of CKD and studied functional and structural effects in a rat model of established CKD. CKD was induced by 5/6 nephrectomy (SNX) combined with L-NNA and 6% NaCl diet in Lewis rats. Six weeks after SNX, CKD rats received either 50 μg CM or 50 μg non-CM (NCM) twice daily intravenously for four consecutive days. Six weeks after treatment CM administration was functionally effective: glomerular filtration rate (inulin clearance) and effective renal plasma flow (PAH clearance) were significantly higher in CM vs. NCM-treatment. Systolic blood pressure was lower in CM compared to NCM. Proteinuria tended to be lower after CM. Tubular and glomerular damage were reduced and more glomerular endothelial cells were found after CM. DNA damage repair was increased after CM. MSC-CM derived exosomes, tested in the same experimental setting, showed no protective effect on the kidney. In a rat model of established CKD, we demonstrated that administration of MSC-CM has a long-lasting therapeutic rescue function shown by decreased progression of CKD and reduced hypertension and glomerular injury.     

Oxidative stress is associated with decreased heart rate variability in patients with chronic kidney disease

Objectives: Elevated oxidative stress and reduced heart rate variability (HRV) is prevalent in patients with chronic kidney disease (CKD) and is associated with increased morbidity and mortality. Previous studies have identified a positive association between elevated oxidative stress and autonomic dysfunction, however this relationship has not yet been investigated in the CKD population.

Methods: Plasma was collected from 78 patients with stage 3–4 CKD (estimated glomerular filtration rate 25–60?ml/min/1.73?m²) for the assessment of oxidative stress, including plasma total F2-isoprostanes, glutathione peroxidase activity and total antioxidant capacity. Time and frequency HRV parameters were measured from a three lead electrocardiogram.

Results: Participants with elevated F2-isoprostanes had reduced HRV compared to patients with normal levels of F2-isoprostanes. A number of HRV parameters were found to be inversely correlated with F2-isoprostanes in all CKD patients, including SDNN (r?=??0.337; P?r?=??0.281, P?=?0.01), LF (r?=??0.315, P?r?=??0.288, P?=?0.01). Multiple linear regression found F2-isoprostanes to be an independent predictor of SDNN (r²?=?0.287, β?=??0.272, P?=?0.01).

Discussion: Oxidative stress is significantly and independently associated with HRV in patients with CKD. Identifying oxidative stress in the pathogenesis of autonomic dysfunction may help target therapeutic strategies.     

Combined application of rapamycin and atorvastatin improves lipid metabolism in apolipoprotein E-deficient mice with chronic kidney disease

Atherosclerosis arising from the pro-inflammatory conditions associated with chronic kidney disease (CKD) increases major cardiovascular morbidity and mortality. Rapamycin (RAPA) is known to inhibit atherosclerosis under CKD and non-CKD conditions, but it can cause dyslipidemia; thus, the co-application of lipid-lowering agents is recommended. Atorvastatin (ATV) has been widely used to reduce serum lipids levels, but its synergistic effect with RAPA in CKD remains unclear. Here, we analyzed the effect of their combined treatment on atherosclerosis stimulated by CKD in apolipoprotein E-deficient (ApoE^−/−) mice. Oil Red O staining revealed that treatment with RAPA and RAPA＋ ATV, but not ATV alone, significantly decreased the atherosclerotic lesions in the aorta and aortic sinus, compared to those seen in the control (CKD) group. The co-administration of RAPA and ATV improved the serum lipid profile and raised the expression levels of proteins involved in reverse cholesterol transport (LXRα, CYP7A1, ABCG1, PPARγ, ApoA1) in the liver. The CKD group showed increased levels of various genes encoding atherosclerosis-promoting cytokines in the spleen (Tnf-α, Il-6 and Il-1β) and aorta (Tnf-α and Il-4), and these increases were attenuated by RAPA treatment. ATV and RAPA＋ATV decreased the levels of Tnf-α and Il-1β in the spleen, but not in the aorta. Together, these results indicate that, in CKD-induced ApoE^−/− mice, RAPA significantly reduces the development of atherosclerosis by regulating the expression of inflammatory cytokines and the co-application of ATV improves lipid metabolism.     

Dietary lysine restriction induces lipid accumulation in skeletal muscle through an increase in serum threonine levels in rats

We previously reported that dietary amino acid restriction induces the accumulation of triglycerides (TAG) in the liver of growing rats. However, differences in TAG accumulation in individual cell types or other tissues were not examined. In this study, we show that TAG also accumulates in the muscle and adipose tissues of rats fed a low amino acid (low-AA) diet. In addition, dietary lysine restriction (low-Lys) induces lipid accumulation in muscle and adipose tissues. In adjusting the nitrogen content to that of the control diet, we found that glutamic acid supplementation to the low-AA diet blocked lipid accumulation, but supplementation with the low-Lys diet did not, suggesting that a shortage of nitrogen caused lipids to accumulate in the skeletal muscle in the rats fed a low-AA diet. Serum amino acid measurement revealed that, in rats fed a low-Lys diet, serum lysine levels were decreased, while serum threonine levels were significantly increased compared with the control rats. When the threonine content was restricted in the low-Lys diet, TAG accumulation induced by the low-Lys diet was completely abolished in skeletal muscle. Moreover, in L6 myotubes cultured in medium containing high threonine and low lysine, fatty acid uptake was enhanced compared with that in cells cultured in control medium. These findings suggest that the increased serum threonine in rats fed a low-Lys diet resulted in lipid incorporation into skeletal muscle, leading to the formation of fatty muscle tissue. Collectively, we propose conceptual hypothesis that “amino-acid signal” based on lysine and threonine regulates lipid metabolism.     

NMR-based metabolomics associated with chronic kidney disease in humans and animals: a one health perspective

Molecular and Cellular Biochemistry - Chronic kidney disease (CKD) is a renal dysfunction that can lead to high rates of mortality and morbidity, particularly when coupled with late diagnosis. CKD...     

Conjugated docosahexaenoic acid inhibits lipid accumulation in rats

Conjugated linoleic acid (CLA), which contains a conjugated double-bond system, and n-3 highly unsaturated fatty acids such as docosahexaenoic acid (DHA) are widely known to improve lipid metabolism. To examine the possibility that a fatty acid with a combination of these structural features might have stronger physiological effects, we prepared conjugated DHA (CDHA) by alkaline isomerization of DHA and examined its effects on lipid and sugar metabolism in rats. Rats were force fed with 200 mg of test oils [linoleic acid (LA), DHA, CLA or CDHA] everyday for 4 weeks. Compared with the animals from the other groups, those in the CDHA group showed a significant weight loss in white adipose tissue (57% of adipose tissue weight in the LA group) and significant decreases in the levels of liver triacylglycerol (TG; 65% of TG level in the LA group) as well as total cholesterol (TC; 88% of TC level in the LA group), indicating suppression of lipid accumulation in the liver and adipose tissue. In addition, plasma TG and TC levels significantly decreased (69% of TG level and 82% of TC level in the LA group), indicating improved lipid metabolism. In the liver, the fatty acid synthesis system was inhibited and the fatty acid beta-oxidation system was activated, whereas the free fatty acid, glucose and tumor necrosis factor alpha levels in the plasma were lowered following CDHA administration. Hence, intake of CDHA appears to suppress the accumulation of fat in the liver and epididymal adipose tissue and improves lipid and sugar metabolism in rats.