Uric acid-lowering and renoprotective effects of topiroxostat, a selective xanthine oxidoreductase inhibitor, in patients with diabetic nephropathy and hyperuricemia: a randomized, double-blind, placebo-controlled, parallel-group study (UPWARD study)

金沢大学医薬保健研究域医学系Background: Hyperuricemia is supposed to be an independent risk factor for kidney dysfunction in diabetic patients. We attempted to examine the uric acid-lowering effect and the renoprotective effect of topiroxostat, a selective xanthine oxidoreductase inhibitor, in patients with diabetic nephropathy and hyperuricemia in this pilot study. Methods: The study design was randomized, double-blind, placebo-controlled, parallel-group study. A total of 65 patients with hyperuricemia and diabetic nephropathy with microalbuminuria were enrolled and assigned to either the topiroxostat group or the placebo group. Topiroxostat (stepwise dosing from 40 to 160 mg/day) or matching placebo was administered BID for 28 weeks. The primary endpoint was a change in the urinary albumin-to-creatinine ratio in the first-morning-void urine sample. Secondary endpoints were changes in the estimated glomerular filtration rate and the serum uric acid level. Results: At 28 weeks, there was no significant difference in the percent change from baseline in the urinary albumin-to-creatinine ratio between the two groups (topiroxostat: 0 vs. placebo: 17%, p = 0.3206), but the changes in the estimated glomerular filtration rate (− 0.2 vs. − 4.0 mL/min/1.73 m2, p = 0.0303) and the serum uric acid level (− 2.94 vs. − 0.20 mg/dL, p < 0.0001) were significantly different between the topiroxostat and placebo groups. Gouty arthritis occurred in 1 patient in the placebo group and no patients in the topiroxostat group. Conclusion: These findings support that diabetic nephropathy combined with hyperuricemia may be associated with kidney dysfunctions. Topiroxostat provides strict control of the serum uric acid level preventing decline of eGFR in these patients. © 2018 The Author(s)Embargo Period 12 month

Mitochondrial Abnormality Facilitates Cyst Formation in Autosomal Dominant Polycystic Kidney Disease

ABSTRACT Autosomal dominant polycystic kidney disease (ADPKD) constitutes the most inherited kidney disease. Mutations in the PKD1 and PKD2 genes, encoding the polycystin 1 and polycystin 2 Ca2+ ion channels, respectively, result in tubular epithelial cell-derived renal cysts. Recent clinical studies demonstrate oxidative stress to be present early in ADPKD. Mitochondria comprise the primary reactive oxygen species source and also their main effector target; however, the pathophysiological role of mitochondria in ADPKD remains uncharacterized. To clarify this function, we examined the mitochondria of cyst-lining cells in ADPKD model mice (Ksp-Cre PKD1flox/flox) and rats (Han:SPRD Cy/+), demonstrating obvious tubular cell morphological abnormalities. Notably, the mitochondrial DNA copy number and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) expression were decreased in ADPKD model animal kidneys, with PGC-1α expression inversely correlated with oxidative stress levels. Consistent with these findings, human ADPKD cyst-derived cells with heterozygous and homozygous PKD1 mutation exhibited morphological and functional abnormalities, including increased mitochondrial superoxide. Furthermore, PGC-1α expression was suppressed by decreased intracellular Ca2+ levels via calcineurin, p38 mitogen-activated protein kinase (MAPK), and nitric oxide synthase deactivation. Moreover, the mitochondrion-specific antioxidant MitoQuinone (MitoQ) reduced intracellular superoxide and inhibited cyst epithelial cell proliferation through extracellular signal-related kinase/MAPK inactivation. Collectively, these results indicate that mitochondrial abnormalities facilitate cyst formation in ADPKD

The Longitudinal Study of Liver Cysts in Patients With Autosomal Dominant Polycystic Kidney Disease and Polycystic Liver Disease

Although polycystic liver disease (PCLD) is one of the extrarenal complications in patients with autosomal dominant polycystic kidney disease (ADPKD), longitudinal changes and the association with total liver volume (TLV) have not been clearly elucidated yet. Methods: Patients with ADPKD were chosen who underwent computed tomography or magnetic resonance imaging twice or more during August 2003 through December 2015. TLV, each cyst volume, and the proportion of parenchyma were measured. The natural history of liver cysts and the association between TLV and liver cysts were evaluated. To compare with liver cysts in ADPKD patients with PCLD, simple liver cysts in patients without ADPKD were also evaluated. Results: TLV at baseline and its growth rate in all the patients with ADPKD, whose serum creatinine, estimated glomerular filtration rate, and total kidney volume were 1.45 mg/dl (0.76–2.32 mg/dl), 38.5 ml/min per 1.73 m2 (18.7–57.9 ml/min per 1.73 m2), and 1394 ml (773–2861 ml), were 1431 ml (1062–1749 ml) and −0.95%/yr (−3.16 to 4.94%/yr), respectively, in the observation period (median, 1063 days). Neither TLV nor its growth rate was significantly different between ADPKD patients with PCLD and those without PCLD. The growth rate of 79 liver cysts was 39.5%/yr (17.5–80.8%/yr) in PCLD patients with ADPKD. It was significantly larger than that of 60 simple liver cysts in the non-ADPKD group, 11.0%/yr (−2.2 to 33.1%/yr). Moreover, the proportion of parenchyma reduced, whereas that of total cyst volume increased significantly (P = 0.001). Discussion: The reduction of parenchyma was accompanied by the growth of liver cysts during time course in PCLD patients with ADPKD