The correlation between kidney volume and measured glomerular filtration rate in an Asian ADPKD population: a prospective cohort study

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disorder that leads to end stage renal disease (ESRD). Cyst expansion in ADPKD is strongly associated with the decline in renal function. However, the correlation between total kidney volume (TKV) and glomerular filtration rate (GFR) at an early stage has not been well demonstrated. There is growing evidence that utilization of estimated GFR (eGFR) may induce misleading information in a population with near normal renal function. Therefore, a more accurate method is essential.

Methods

A prospective cohort of ADPKD patients was conducted with clinical data and laboratory collection. Measured GFR (mGFR) was assessed by iohexol plasma clearance method using ultra performance liquid chromatography. eGFR was calculated using the CKD-EPI equation. Kidney volumes were evaluated using MRI imaging protocol.

Results

Thirty two patients completed the study. The mean age was 56 years old. The mean initial mGFR was 83.8 mL/min/1.73m². The mean change in mGFR per year was –2.99 mL/min/1.73m²/year. The mean initial height-adjusted TKV (htTKV) was 681.0 mL/m. The mean percentage change in htTKV per year (%ΔhtTKV/y) was 4.77 %/year. mGFR had a better association with clinical parameters than eGFR. Initial mGFR was significantly and inversely correlated with initial htTKV and age. The percentage change in mGFR per year was significantly and inversely correlated with the %ΔhtTKV/y and 24-hr urine albumin. The %ΔhtTKV/y was significantly correlated with initial htTKV.

Conclusions

Our studies demonstrated that mGFR using iohexol is a more reliable and accurate method than eGFR for evaluating GFR changes in the early stages of ADPKD patients. There is a strong inverse correlation between kidney volume and mGFR in an Asian ADPKD population. The initial htTKV is a good predictor of kidney volume progression. The %ΔhtTKV/y is a good early surrogate marker for the decline in renal function. 24-hr urine albumin is also a good indicator for renal progression.

Unique chromoplast organisation and carotenoid gene expression in carotenoid-rich carrot callus

MAIN CONCLUSION

The new model orange callus line, similar to carrot root, was rich in carotenoids due to altered expression of some carotenogenesis-associated genes and possessed unique diversity of chromoplast ultrastructure. Callus induced from carrot root segments cultured in vitro is usually pale yellow (p-y) and poor in carotenoids. A unique, non-engineered callus line of dark orange (d-o) colour was developed in this work. The content of carotenoid pigments in d-o callus was at the same level as in an orange carrot storage root and nine-fold higher than in p-y callus. Carotenoids accumulated mainly in abundant crystalline chromoplasts that are also common in carrot root but not in p-y callus. Using transmission electron microscopy, other types of chromoplasts were also found in d-o callus, including membranous chromoplasts rarely identified in plants and not observed in carrot root until now. At the transcriptional level, most carotenogenesis-associated genes were upregulated in d-o callus in comparison to p-y callus, but their expression was downregulated or unchanged when compared to root tissue. Two pathway steps were critical and could explain the massive carotenoid accumulation in this tissue. The geranylgeranyl diphosphate synthase gene involved in the biosynthesis of carotenoid precursors was highly expressed, while the β-carotene hydroxylase gene involved in β-carotene conversion to downstream xanthophylls was highly repressed. Additionally, paralogues of these genes and phytoene synthase were differentially expressed, indicating their tissue-specific roles in carotenoid biosynthesis and metabolism. The established system may serve as a novel model for elucidating plastid biogenesis that coincides with carotenogenesis.

Development and validation of RP-HPLC and RP-UPLC methods for quantification of erythropoietin formulated with human serum albumin

Rapid and sensitive reverse phase high performance liquid chromatography (RP–HPLC) and ultra performance liquid chromatography (UPLC) methods with UV detection for quantification of erythropoietin (EPO) in presence of human serum albumin (HSA) as a stabilizer in a pharmaceutical formulation of EPO have been developed and validated. Chromatography was performed with mobile phase containing 0.1% Trifluoroacetic acid (TFA) in MilliQ water and 0.1% TFA in acetonitrile with gradient program and a flow rate of 1.5 mL/min for HPLC and 0.35 mL/min for UPLC. Quantification was accomplished with internal reference standard (qualified using EP reference standard). The methods were validated for linearity (correlation coefficient=0.99), accuracy, precision and robustness. Robustness was confirmed by considering three factors; percentages of TFA in mobile phase, age of test sample and mobile phase and column temperature. Intermediate precision was confirmed by different analysts, different equipments and on different days. The relative standard deviation (RSD) value (<2%, n=30) indicated good precision of the developed method. The proposed RP-HPLC method had retention time less than 20 min while the developed UPLC method had retention time less than 4 min. Both the RP-HPLC and UPLC methods were simple, highly sensitive, precise and accurate, suggesting that the developed methods are useful for routine quality control.