Investigation of methods for more accurate estimation of kidney function in people with high muscle mass
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Serum creatinine (SCr) levels depend on muscle mass and are therefore elevated in people with high muscle mass, potentially leading to underestimation of kidney function in this population. Although recent therapeutic guidelines have shown measurement of serum cystatin C (ScysC) to be useful, this method has not been validated in people with high muscle mass. We conducted this study to investigate methods for more accurately estimating kidney function in people with high muscle mass. Linear regression analysis was used to assess the correlation of endogenous creatinine clearance (24-hour CLcr) and 24-hour CLcr × 0.715 (i.e., modified glomerular filtration rate (GFR)); with estimated kidney function from SCr and ScysC in 15 healthy young adult men with high muscle mass. A significant but weak positive correlation was observed between 24-hour CLcr and estimated CLcr by the Cockcroft and Gault formula (CG CLcr; R2 = 0.371, p = 0.016). The estimated GFR calculated from ScysC (eGFRcys) was significantly higher than CLcr × 0.715, but the two were not correlated (R2 = 0.125, p = 0.197). However, when CG CLcr and eGFRcr were adjusted by muscle mass parameters, the correlation between measured and estimated values improved. Further improvement was seen when participants with a fat mass greater than 25% were excluded (R2 = 0.623, p = 0.004; R2 = 0.510, p = 0.014; n = 11 for both). The results of our study suggest that currently used formulas for estimating kidney function, including eGFRcys, may not be appropriate for people with high muscle mass, but use of muscle mass parameters may improve predictivity.
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Intensive uric acid-lowering therapy in CKD patients: the protocol for a randomized controlled trial.

BACKGROUND: Hyperuricemia would be a risk factor for the development/progression of CKD. However, several studies showed U-shape association between serum uric acid level and renal impairment, suggesting that hypouricemia was rather associated with renal dysfunction. Perhaps, there is the optimal target level of serum UA for renal function. METHODS: The Target-UA study is a multicenter randomized controlled trial. Eligible CKD patients (eGFR ≥ 30, < 60 mL/min/1.73 m2 and urine protein < 0.5 g/gCr or urine albumin to creatinine ratio (ACR) < 300 mg/gCr) with serum UA ≥ 8.0 mg/dL (≥ 7.0 mg/dl: under the treatment) will be enrolled and be randomly assigned to the intensive therapy group (target serum UA level ≥ 4.0 mg/dL, < 5.0 mg/dL) or the standard therapy group (serum UA level ≥ 6.0 mg/dL, < 7.0 mg/dL). Topiroxostat, a new xanthine oxidase inhibitor, will be administered to treat hyperuricemia. The primary endpoint is a change in logarithmic value of urine ACR between baseline and week 52 of treatment. The secondary endpoints include changes in serum UA, eGFR, urine protein, lipid profile, and onset of composite cardiovascular events, renal events, gouty arthritis, and attack of urolithiasis. The number of subjects has been set to be 185 in each group for a total of 370. DISCUSSION: This is the first study, to the best of our knowledge, to determine the optimal target level of serum UA for renal protection and is expected to lead to progress in CKD treatment. TRIAL REGISTRATION: (UMIN000026741 and jRCTs051180146).

Cinacalcet for hemodialyzed patients with or without a high PTH level to control serum calcium and phosphorus: ECO (evaluation of cinacalcet HCl outcome) study.

BACKGROUND: We investigated the influence of cinacalcet on serum Ca and P in hemodialyzed patients with or without a high PTH level, according to K/DOQI guideline, to control serum Ca and P levels. METHODS: We recruited 130 patients in this prospective cohort study and classified them into Group A (iPTH > 300 pg/ml), Group B (iPTH = 181 - 300 pg/ml), and Group C (iPTH ≤ 180 pg/ml). After 24 weeks on cinacalcet, serum Ca, P and iPTH were measured. RESULTS: The achievement rate of the target iPTH level in JSDT guideline was significantly higher in Group B compared with Group A. The achievement rate of serum Ca and P target levels in the Japanese Society for Dialysis Therapy (JSDT) guideline was higher in Group C. In Group A and Group C, the simultaneous achievement rates (Ca, P, and iPTH) in KDOQI guideline increased after treatment with cinacalcet (p < 0.01). There was no difference in the reduction of Ca and P among the groups, while the iPTH reduction was significantly lower in groups B and C compared with that in A. CONCLUSION: Administration of cinacalcet to patients with or without high PTH levels, according to the K/DOQI guideline, facilitates the control of Ca and P levels.

Human sodium phosphate transporter 4 (hNPT4/SLC17A3) as a common renal secretory pathway for drugs and urate.

The evolutionary loss of hepatic urate oxidase (uricase) has resulted in humans with elevated serum uric acid (urate). Uricase loss may have been beneficial to early primate survival. However, an elevated serum urate has predisposed man to hyperuricemia, a metabolic disturbance leading to gout, hypertension, and various cardiovascular diseases. Human serum urate levels are largely determined by urate reabsorption and secretion in the kidney. Renal urate reabsorption is controlled via two proximal tubular urate transporters: apical URAT1 (SLC22A12) and basolateral URATv1/GLUT9 (SLC2A9). In contrast, the molecular mechanism(s) for renal urate secretion remain unknown. In this report, we demonstrate that an orphan transporter hNPT4 (human sodium phosphate transporter 4; SLC17A3) was a multispecific organic anion efflux transporter expressed in the kidneys and liver. hNPT4 was localized at the apical side of renal tubules and functioned as a voltage-driven urate transporter. Furthermore, loop diuretics, such as furosemide and bumetanide, substantially interacted with hNPT4. Thus, this protein is likely to act as a common secretion route for both drugs and may play an important role in diuretics-induced hyperuricemia. The in vivo role of hNPT4 was suggested by two hyperuricemia patients with missense mutations in SLC17A3. These mutated versions of hNPT4 exhibited reduced urate efflux when they were expressed in Xenopus oocytes. Our findings will complete a model of urate secretion in the renal tubular cell, where intracellular urate taken up via OAT1 and/or OAT3 from the blood exits from the cell into the lumen via hNPT4.

Effect of telmisartan on ambulatory blood pressure monitoring, plasma brain natriuretic peptide, and oxidative status of serum albumin in hemodialysis patients.

The effect of telmisartan on ambulatory blood pressure, plasma neurohormonal parameters, and oxidation of serum albumin has not been investigated in hemodialysis (HD) patients. Thirteen hypertensive HD patients were treated with 40 mg telmisartan once daily, and 24-h ambulatory blood pressure monitoring was performed after 0, 4, and 8 weeks of treatment. Plasma renin activity, plasma aldosterone concentration (PAC), brain natriuretic peptide (BNP) level, and serum oxidized albumin level were determined at the same time points. Serum telmisartan concentration was also measured at 4 and 8 weeks. Telmisartan significantly reduced systolic blood pressure and diastolic blood pressure (both awake and sleeping) after 4 weeks, and these pressures showed a further significant decrease after 8 weeks. Plasma levels of aldosterone, BNP, and serum oxidized albumin were markedly decreased after 4 weeks and these lower levels were maintained at 8 weeks. The trough serum telmisartan concentration was not significantly different at 8 weeks compared with 4 weeks. Throughout the treatment period, there were no significant adverse effects. Telmisartan effectively lowers blood pressure and reduces PAC, BNP, and oxidative stress and is safe and well-tolerated by HD patients. A long-term study in a large population is required to determine the influence of telmisartan therapy on cardiovascular mortality and morbidity in HD patients.