Efficacy of Hydroxy-L-proline (HYP) analogs in the treatment of primary hyperoxaluria in Drosophila Melanogaster.

BACKGROUND: Substrate reduction therapy with analogs reduces the accumulation of substrates by inhibiting the metabolic pathways involved in their biosynthesis, providing new treatment options for patients with primary hyperoxalurias (PHs) that often progress to end-stage renal disease (ESRD). This research aims to evaluate the inhibition efficacy of Hydroxy-L-proline (HYP) analogs against calcium oxalate (CaOx) crystal formation in the Drosophila Melanogaster (D. Melanogaster) by comparing them with Pyridoxine (Vitamin B6). METHODS: Three stocks of Drosophila Melanogaster (W118, CG3926 RNAi, and Act5C-GAL4/CyO) were utilized. Two stocks (CG3926 RNAi and Act5C-GAL4 /CyO) were crossed to generate the Act5C > dAGXT RNAi recombinant line (F1 generation) of D. Melanogaster which was used to compare the efficacy of Hydroxy-L-proline (HYP) analogs inhibiting CaOx crystal formation with Vitamin B6 as the traditional therapy for primary hyperoxaluria. RESULTS: Nephrolithiasis model was successfully constructed by downregulating the function of the dAGXT gene in D. Melanogaster (P-Value = 0.0045). Furthermore, the efficacy of Hydroxy-L-proline (HYP) analogs against CaOx crystal formation was demonstrated in vivo using D. Melanogaster model; the results showed that these L-Proline analogs were better in inhibiting stone formation at very low concentrations than Vitamin B6 (IC50 = 0.6 and 1.8% for standard and dietary salt growth medium respectively) compared to N-acetyl-L-Hydroxyproline (IC50 = 0.1% for both standard and dietary salt growth medium) and Baclofen (IC50 = 0.06 and 0.1% for standard and dietary salt growth medium respectively). Analysis of variance (ANOVA) also showed that Hydroxy-L-proline (HYP) analogs were better alternatives for CaOx inhibition at very low concentration especially when both genetics and environmental factors are intertwined (p < 0.0008) for the dietary salt growth medium and (P < 0.063) for standard growth medium. CONCLUSION: Addition of Hydroxy-L-Proline analogs to growth medium resulted in the reduction of CaOx crystals formation. These analogs show promise as potential inhibitors for oxalate reduction in Primary Hyperoxaluria.

Oxalate nephropathy in a Tibetan spaniel litter. A probable case of primary hyperoxaluria.

Severe oxalate nephropathy with end-stage kidney lesions was found in two pups of a litter of three Tibetan Spaniels. This histopathological finding strongly suggests a primary hyperoxaluria since there was no exposure to agents capable of producing secondary hyperoxaluria. Primary hyperoxaluria has not been reported as a spontaneous disease in the dog, although it is a well-known, but rare, inherited metabolic disease of man.

Effect of vitamin C supplementation on renal oxalate deposits in five-sixths nephrectomized rats.

We have previously reported that hyperoxalemia can be aggravated by vitamin C supplementation in regular hemodialysis patients. The present study was undertaken to examine the validity of this observation in an experimental setting. Fifty five-sixths nephrectomized rats were divided into two groups: 30 rats were allowed free access to water containing 8 mg/ml of vitamin C (100-160 mg/100 g/24 h) and the remainder given tap water without vitamin C. The serum creatinine increased and the Hct decreased gradually; however, there was no difference between the two groups. Plasma vitamin C, oxalate and urinary oxalate levels were higher in the vitamin -treated group than the nontreated rats. Histological examination revealed glomerular and interstitial fibrosis and round cell infiltration as well as tubular cyst formation. Oxalate deposits in renal tubules were found only in vitamin C-treated rats with advanced renal failure. Nontreated animals with equally advanced renal impairment showed no oxalate deposits. These results confirm our previous clinical findings that vitamin C supplementation aggravates the secondary oxalosis of chronic renal failure.