Hyperuricemia contributes to renal inflammation. We aimed to investigate the role of Na
-K
-ATPase (NKA) in hyperuricemia-induced renal tubular injury. Human primary proximal tubular epithelial cells ...(PTECs) were incubated with uric acid (UA) at increasing doses or for increasing lengths of time. PTECs were then stimulated by pre-incubation with an NKA α1 expression vector or small interfering RNA before UA (100 μg ml
, 48 h) stimulation. Hyperuricemic rats were induced by gastric oxonic acid and treated with febuxostat (Feb). ATP levels, the activity of NKA and expression of its α1 subunit, Src, NOD-like receptor pyrin domain-containing protein 3 (NLRP3) and interleukin 1β (IL-1β) were measured both in vitro and in vivo. Beginning at concentrations of 100 μg ml
, UA started to dose-dependently reduce NKA activity. UA at a concentration of 100 μg ml
time-dependently affected the NKA activity, with the maximal increased NKA activity at 24 h, but the activity started to decrease after 48 h. This inhibitory effect of UA on NKA activity at 48 h was in addition to a decrease in NKA α1 expression in the cell membrane, but an increase in lysosomes. This process also involved the subsequent activation of Src kinase and NLRP3, promoting IL-1β processing. In hyperuricemic rats, renal cortex NKA activity and its α1 expression were upregulated at the 7th week and both decreased at the 10th week, accompanied with increased renal cortex expression of Src, NLRP3 and IL-1β. The UA levels were reduced and renal tubular injuries in hyperuricemic rats were alleviated in the Feb group. Our data suggested that the impairment of NKA and its consequent regulation of Src, NLRP3 and IL-1β in the renal proximal tubule contributed to hyperuricemia-induced renal tubular injury.
Uric acid has emerged as a novel and potential modifiable risk factor for the incidence and progression of kidney diseases, however, the deteriorate effect of uric acid on renal mesangial cells ...remains unclear. The present study is to examine the immune activation of soluble and crystal forms of uric acid in human mesangial cells.
We stimulated primary human mesangial cells (HMCs) with increasing concentrations (from 50 to 200 μg/ml) of soluble monosodium urate (MSU) or MSU crystals. We examined interleukin (IL)-1β protein expression levels in cell culture by ELISA. The stimulated HMCs were further stimulated with soluble MSU or MSU crystals at 200 μg/ml with or without the pre-incubation of toll like receptor (TLR) 4 inhibitor TAK242 (1μM). TLR4, nod-like receptor protein (NLRP3, also known as NALP3), IL-1β, human leukocyte antigen (HLA)-DR and CD40 were examined by Realtime-PCR, Western blot and ELISA, respectively.
We found that both soluble MSU and MSU crystals increased IL-1β protein expression levels in dose-dependent fashion. Soluble MSU significantly enhanced the expression of TLR4, NLRP3, IL-1β, HLA-DR and CD40 while MSU crystals only upregulated the expression of TLR4 and IL-1β. TLR4 inhibitor TAK242 significantly blocked the up-regulation of NLRP3, IL-1β, HLA-DR and CD40 induced by soluble MSU while no TAK242 suppression effect on MSU crystals induced IL-1β up-regulation was found.
Our results suggested that soluble MSU, but not MSU crystals, induce NLRP3, IL-1β, HLA-DR and CD40 upregulation in a TLR4-dependent manner. These findings indicate that soluble MSU may play a pathological role in hyperuricemia induced renal mesangial injury.
Purpose
Clinical classification of hyperuricemia (HUA) could help to guide therapy of HUA. Studies on the classification of HUA with chronic kidney disease (CKD) are rare. Therefore, we aimed to ...investigate the classification of HUA with CKD.
Methods
A cross-sectional study of 428 CKD patients was conducted, including 218 HUA patients. By correlation analysis, the association of 24-h urinary uric acid (24-h Uur), uric acid clearance rate (Cur), the urinary uric acid excretion per kilogram of weight per hour (Eur) and fractional excretion of uric acid (FEur) with estimated glomerular filtration rate (eGFR) was analyzed in the HUA and non-HUA groups. According to Eur combined with Cur and the 24-h Uur combined with FEur, HUA with CKD was classified into underexcretion, renal overload, combined and ‘normal’ types, which were also stratified by CKD stages.
Results
According to the Eur and Cur, in early CKD (eGFR ≥ 60 mL/min/1.73 m
2
), the underexcretion type accounted for 83.75%, and the renal overload type accounted for 2.5%. As the CKD stage increased, the proportion of the underexcretion type increased. According to the 24-h Uur and FEur, in early CKD, the underexcretion type accounted for 53.75%, and the renal overload type accounted for 15%. With increasing CKD stages, the proportion of the ‘normal’ type increased significantly.
Conclusion
Different uses of Eur with Cur or 24-h Uur with FEur varied significantly in classifying HUA patients with CKD. Eur + Cur may be more applicable to the classification of HUA patients with CKD, and further research is needed.
Mounting studies have shown that hyperuricemia is related to kidney diseases through multiple ways. However, the application of urinary uric acid indicators in patients with reduced renal function is ...not clear. In this study, we aim to determine the effects of renal function on various indicators reflecting uric acid levels in patients with chronic kidney disease (CKD).
Anthropometric and biochemical examinations were performed in 625 patients with CKD recruited from Dept of Nephrology of Huadong hospital affiliated to Fudan University. Multiple regression analyses were used to study correlations of the estimated glomerular filtration rate (eGFR) with serum uric acid (SUA) and renal handling of uric acid. For further study, smooth curve plots and threshold effect analyses were applied to clarify associations between renal function and uric acid levels.
The nonlinear relationships were observed between eGFR and urinary uric acid indicators. The obvious inflection points were observed in smooth curve fitting of eGFR and fractional excretion of uric acid (FEur), excretion of uric acid per volume of glomerular filtration (EurGF). In subsequent analyses where levels of eGFR< 15 mL/min/1.73m
were dichotomized (CKD5a/CKD5b), patients in the CKD5a showed higher levels of FEur and EurGF while lower levels of urinary uric acid excretion (UUA), clearance of uric acid (Cur) and glomerular filtration load of uric acid (FLur) compared with CKD5b group (all P < 0.05). And there was no significant difference of SUA levels between two groups. On the other hand, when eGFR< 109.9 ml/min/1.73 m
and 89.1 ml/min/1.73 m
, the resultant curves exhibited approximately linear associations of eGFR with Cur and FLur respectively.
FEur and EurGF showed significantly compensatory increases with decreased renal function. And extra-renal uric acid excretion may play a compensatory role in patients with severe renal impairment to maintain SUA levels. Moreover, Cur and FLur may be more reliable indicators of classification for hyperuricemia in CKD patients.
Statins are the most widely used drugs in elderly patients; the most common clinical application of statins is in aged hyperlipemia patients. There are few studies on the effects and mechanisms of ...statins on bone in elderly mice with hyperlipemia. The study is to examine the effects of atorvastatin on bone phenotypes and metabolism in aged apolipoprotein E-deficient (apoE
) mice, and the possible mechanisms involved in these changes.
Twenty-four 60-week-old apoE
mice were randomly allocated to two groups. Twelve mice were orally gavaged with atorvastatin (10 mg/kg body weight/day) for 12 weeks; the others served as the control group. Bone mass and skeletal microarchitecture were determined using micro-CT. Bone metabolism was assessed by serum analyses, qRT-PCR, and Western blot. Bone marrow-derived mesenchymal stem cells (BMSCs) from apoE
mice were differentiated into osteoblasts and treated with atorvastatin and silent information regulator 1 (Sirt1) inhibitor EX-527.
The results showed that long-term administration of atorvastatin increases bone mass and improves bone microarchitecture in trabecular bone but not in cortical bone. Furthermore, the serum bone formation marker osteocalcin (OCN) was ameliorated by atorvastatin, whereas the bone resorption marker tartrate-resistant acid phosphatase 5b (Trap5b) did not appear obviously changes after the treatment of atorvastatin. The mRNA expression of Sirt1, runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), and OCN in bone tissue were increased after atorvastatin administration. Western blot showed same trend in Sirt1 and Runx2. The in vitro study showed that when BMSCs from apoE
mice were pretreated with EX527, the higher expression of Runx2, ALP, and OCN activated by atorvastatin decreased significantly or showed no difference compared with the control. The protein expression of Runx2 showed same trend.
Accordingly, the current study validates the hypothesis that atorvastatin can increase bone mass and promote osteogenesis in aged apoE
mice by regulating the Sirt1-Runx2 axis.
Mitochondrial dysfunction has been implicated in the early stages or progression of many renal diseases. Improving mitochondrial function and homeostasis has the potential to protect renal function. ...Serum- and glucocorticoid-induced kinase 1 (SGK1) is known to regulate various cellular processes, including cell survival. In this study, we intend to demonstrate the effect and molecular mechanisms of SGK1 in renal tubular cells upon oxidative stress injury and to determine whether regulation of mitochondrial function is implicated in this process. HK-2 cells were exposed to H2O2, and cell viability and apoptosis were dynamically detected by the CCK-8 assay and annexin-V/PI staining. The concentrations of cellular reactive oxygen species (ROS) and adenosine triphosphate (ATP) and the expression of the SGK1/GSK3β/PGC-1α signaling pathway were analyzed by flow cytometry or western blot. In addition, shRNA targeting SGK1 and SB216763 were added into the culture medium before H2O2 exposure to downregulate SGK1 and GSK3β, respectively. Cell viability and mitochondrial functions, including mitochondrial membrane potential (Δψm), Cytochrome C release, mtDNA copy number, and mitochondrial biogenesis, were examined. Protein levels and SGK1 activation were significantly stimulated by H2O2 exposure. HK-2 cells with SGK1 inhibition were much more sensitive to H2O2-induced oxidative stress injury than control group cells, as they exhibited increased apoptotic cell death and mitochondrial dysfunction involving the deterioration of cellular ATP production, ROS accumulation, mitochondrial membrane potential reduction, and release of Cytochrome C into the cytoplasm. Studies on SGK1 knockdown also indicated that SGK1 is required for the induction of proteins associated with mitochondrial biogenesis, including PGC-1α, NRF-1, and TFAM. Moreover, the deleterious effects of SGK1 suppression on cell apoptosis and mitochondrial function, including mitochondrial biogenesis, were related to the phosphorylation of GSK3β and partially reversed by SB216763 treatment. H2O2 leads to SGK1 overexpression in HK-2 cells, which protects human renal tubule cells from oxidative stress injury by improving mitochondrial function and inactivating GSK3β.
Aim
To investigate the correlation of renal tubular inflammatory and injury markers with renal uric acid excretion in chronic kidney disease (CKD) patients.
Methods
Seventy-three patients with CKD ...were enrolled. Fasting blood and morning urine sample were collected for routine laboratory measurements. At the same time, 24 h of urine was collected for urine biochemistry analyses, and 10 ml was extracted from the 24-h urine sample to further detect renal tubular inflammatory and injury markers, including interleukin-18 (IL-18), interleukin 1β (IL-1β), neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). The patients were divided into three tertile groups according to their 24-h urinary uric acid (24-h UUA) levels (UUA1: 24-h UUA ≤ 393.12 mg; UUA2: 393.12 < 24-h UUA ≤ 515.76 mg; UUA3: 24-h UUA > 515.76 mg). The general clinical and biochemical indexes were compared. Multivariable linear regression models were used to test the association of IL-18/Urinary creatinine concentration (IL-18/CR), IL-1β/CR, NGAL/CR and KIM-1/CR with renal uric acid excretion indicators.
Results
All of tested renal tubular inflammation- and injury-related urinary markers were negatively associated with 24-h UUA and UEUA, and the negative correlation still persisted after adjusting for multiple influencing factors including urinary protein and eGFR. Further group analyses showed that these makers were significantly higher in the UUA1 than in the UUA3 group.
Conclusions
Our findings suggest that markers of urinary interstitial inflammation and injury in CKD patients are significantly correlated with 24-h UUA and Urinary excretion of uric acid (UEUA), and those with high 24-h UUA have lower levels of these markers. Renal uric acid excretion may also reflect the inflammation and injury of renal tubules under certain conditions.
Increasing evidence has shown that albuminuria is related to serum uric acid. Little is known about whether this association may be interrelated via renal handling of uric acid. Therefore, we aim to ...study urinary uric acid excretion and its association with albuminuria in patients with chronic kidney disease (CKD).
A cross-sectional study of 200 Chinese CKD patients recruited from department of nephrology of Huadong hospital was conducted. Levels of 24 h urinary excretion of uric acid (24-h Uur), fractional excretion of uric acid (FEur) and uric acid clearance rate (Cur) according to gender, CKD stages, hypertension and albuminuria status were compared by a multivariate analysis. Pearson and Spearman correlation and multiple regression analyses were used to study the correlation of 24-h Uur, FEur and Cur with urinary albumin to creatinine ratio (UACR).
The multivariate analysis showed that 24-h Uur and Cur were lower and FEur was higher in the hypertension group, stage 3-5 CKD and macro-albuminuria group (UACR> 30 mg/mmol) than those in the normotensive group, stage 1 CKD group and the normo-albuminuria group (UACR< 3 mg/mmol) (all P < 0.05). Moreover, males had higher 24-h Uur and lower FEur than females (both P < 0.05). Multiple linear regression analysis showed that UACR was negatively associated with 24-h Uur and Cur (P = 0.021, P = 0.007, respectively), but not with FEur (P = 0.759), after adjusting for multiple confounding factors.
Our findings suggested that urinary excretion of uric acid is negatively associated with albuminuria in patients with CKD. This phenomenon may help to explain the association between albuminuria and serum uric acid.
Background/Aims: Hypertension and hyperuricemia are closely associated with an intermingled cause and effect relationship. Additionally, urinary sodium and potassium excretion is related to blood ...pressure. Whether or not it is associated with urinary uric acid excretion is not clear. Therefore, we aim to study the association of urinary sodium and potassium with renal uric acid excretion in patients with CKD. Methods: A cross-sectional study of 428 patients with CKD recruited from our department was conducted. All patients were divided into hypertension and non-hypertension group. In these two groups, Spearman correlation and multiple linear regression analysis were used to study the correlation of urinary sodium and potassium with renal handling of uric acid. Results: According to multiple linear regression analysis, in hypertension group, fractional excretion of sodium (FEna) was negatively correlated with 24 hour urinary uric acid (24-hUur) and uric acid clearance rate (Cur) (beta coefficients B=-0.066, -0.182, respectively; both P< 0.05), and positively correlated with fractional excretion of uric acid (FEur) (B=1.641, P< 0.001). Additionally, fractional excretion of potassium (FEk) was positively correlated with FEur (B=0.576, P< 0.001), but not related to 24-hUur and Cur (both P>0.05). And urinary sodium/potassium ratio (Una/k) was negatively related to 24-h Uur and Cur (B=-0.047, -0.159, both P< 0.05), and positively related to FEur (B=0.578, P< 0.05). Furthermore, FEna and FEk was still positively related to FEur in the lowest tertile of eGFR groups (both P< 0.05), but not related in the second and highest tertile of eGFR groups (all P> 0.05). In non-hypertension group, FEna was negatively correlated with 24-hUur (B=-0.589, P< 0.05), but not related to Cur and FEur (both P> 0.05). both FEk and Una/k was not related to 24-h Uur, Cur and FEur (all P> 0.05). Moreover, FEna and FEk was still not correlated with FEur in all tertiles of eGFR groups (all P> 0.05). Conclusion: We found that in patients with CKD, urinary sodium and potassium excretion is closely correlated to renal handling of uric acid, which was pronounced in hypertensive patients with low eGFR. This phenomenon may be one of the mechanisms of the relationship between hypertension and hyperuricemia. Further research is needed to confirm it. It is expected to manage hyperuricemia in terms of controlling the diet of sodium and potassium.
To analyze the association between hypertension and urinary uric acid excretion in patients with chronic kidney disease (CKD).
We screened 87 patients who had been admitted at the Dept of Nephrology, ...Huadong hospital between April 2017 to April 2019 who had completed 24-h ambulatory blood pressure monitoring and retained 24-h urine biochemical test specimens, thirty adult patients (age ≤ 65 years) with CKD 1-2 stages were recruited in the study. Pearson's correlation analysis and multiple linear regression analysis were used to study the correlation of urinary uric acid excretion with ambulatory blood pressure values and the association of morning mean diastolic pressure (mMDP), night mean diastolic pressure (nMDP) and CV of dMSP (coefficient of variation of day mean systolic pressure) with fractional excretion of uric acid (FEua) and uric acid clearance rate (Cur). Independent T test was used to compare the differences of blood pressure values in FEua1 (FEua< 6.0%) and FEua2 (FEua≥6.0%) or Cur1 (Cur < 6.2 ml/min/1.73 m
) and Cur2 (Cur ≥ 6.2 ml/min/1.73m
) groups according to the median of FEua or Cur, respectively.
After adjusting for confounding factors, multiple linear regression analysis showed that FEua was positively associated with the mMDP and nMDP, Cur was positively associated with CV of dMSP. Levels of mMDP and nMDP in FEua1 group was lower than that in FEua2 group (both
< 0.05), level of CV of dMSP in Cur2 group were higher than that in Cur1 group (
< 0.01).
We demonstrated that there is a positive correlation of FEua with morning and night mean diastolic pressure separately and Cur is positively related to CV of dMSP in CKD population. Monitoring the trend of urinary uric acid, may have a role in the early detection for hypertension or relative risks in the population of CKD.
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