Beneficial effect of vitamin E supplementation on the biochemical and kinetic properties of Tamm–Horsfall glycoprotein in hypertensive and hyperoxaluric patients

Abstract

Background. This study aimed to assess the therapeutic efficacy of oral vitamin E supplementation on the biochemical and kinetic properties of Tamm-Horsfall glycoprotein (THP) in hypertensive and hyperoxaluric patients. Methods. Newly detected hypertensives (n ¼ 200) and stone formers (n ¼ 200) were each subdivided into two groups. One group (n ¼ 100) was administered the antioxidant vitamin E at 400 mg/day given as an oral supplement along with standard therapeutic drugs for hypertension and hyperoxaluria and the patients were followed for a period of 9 months. The other group (n ¼ 100) did not receive vitamin E (placebo controls). Age and sex-matched controls (n ¼ 100) were monitored simultaneously. THP was isolated from 24 h urine samples before and at the end of every third month during a period of 9 months from the vitamin Etreated hypertensive and hyperoxaluric groups. THP samples were also collected from control subjects, and at the end of the ninth month from placebo controls. The isolated protein was assessed for purity by SDS-PAGE. The purity-checked proteins were subjected to spectrophotometric crystallization assay, calcium oxalate (CaOx) crystal interaction studies, and biochemical analysis of sialic acid, thiol and carbonyl content. Plasma superoxide, hydroxyl radical, hydrogen peroxide and vitamin E levels as well as superoxide dismutase and catalase activities were also monitored. Results. The THP from the hypertensive and hyperoxaluric subjects exhibited a significant promoting effect on the nucleation and aggregation phases and caused a concomitant increase in CaOx crystal interaction. The altered kinetic properties of THP in these subjects were strongly associated with increased carbonyl content and with decreased thiol and sialic acid contents. Oral administration of vitamin E to these patients caused near normalization of these biochemical alterations and satisfactorily restored the kinetic properties of THP to near normal activity. At the end of 9 months, THP isolated from placebo controls (hypertensive and hyperoxaluric) showed highly aggregated calcium oxalate monohydrate crystals as observed by light microscopy. In contrast, vitamin E-supplemented patients showed CaOx dihydrate crystals that were similar to control THP. There was an imbalance in the oxidant and antioxidant levels. For the oxidants, superoxide, hydrogen peroxide and hydroxyl radical levels were increased, and for the antioxidants, there was loss of antioxidant enzyme activities and a decline in plasma vitamin E level in both hypertensive and hyperoxaluric patients. Supplementary antioxidant (vitamin E) corrected this imbalance to near normal conditions. Conclusion. We hypothesize that the loss of THP inhibitory activity in the hypertensive and hyperoxaluric patients in a crystallizing medium is mediated primarily by oxidative damage to this protein. The possible occurrence of renal stones in essential hypertensive subjects, and the risk of recurrence in hyperoxaluric subjects, may be explained by oxidative damage ...

Low-vitamin E diet exacerbates calcium oxalate crystal formation via enhanced oxidative stress in rat hyperoxaluric kidney

“…Although there are no epidemiologic studies showing that vitamin E deficiency is a general phenomenon in chronic hyperoxaluric patients, there is a report showing that low serum vitamin E levels are seen in hyperoxaluric patients (29). These patients have an imbalance in oxidant and antioxidant levels in peripheral blood and can be corrected to near normal levels by vitamin E supplementation.…”

“…Vitamin E is the most potent fat-soluble antioxidant in the chain reaction of removing free radicals, protecting membranes from free radical damage, and preventing lipid peroxidation (3,4). Vitamin E deficiency not only decreases renal antioxidant enzyme protein levels and activities but also enhances the differentiation of monocytes to macrophages (4,29) and superoxide production by increasing NADPH oxidase expression (1). Furthermore, vitamin E deficiency can induce a proapoptotic response in lung cells and sensitize them to additional insult (27,28).…”

Detection Single Nucleotide Polymorphisms in Uromodulin Promoter Region Associated With Renal Diseases Using Single-Strand Conformation Polymorphism-Polymerase Chain Polymorphisms Technique

“…In human, the uromodulin is encoded by the UMOD gene, which composed of eleven exons located on chromosome 16p12.3 [1,2]. The primary structure of the polypeptide chain which containing 640 amino acids (aa) with a signal sequence (24 aa) and 8 potential N-linked glycosylation sites [3]. Sequence homology revealed that the protein is may contain N-terminal signal sequence; three epidermal growth factor (EGF)-like domains, the second and third of EGF-like domains contain a calcium-binding motif; a central domain of eight cysteines (D8C) within a cysteine-rich region; a zona pellucida domain is essential for the extracellular protein polymerization into helical filaments; and GPI-anchoring site for integrating the protein with the cell membrane [4].…”

“…Sequence homology revealed that the protein is may contain N-terminal signal sequence; three epidermal growth factor (EGF)-like domains, the second and third of EGF-like domains contain a calcium-binding motif; a central domain of eight cysteines (D8C) within a cysteine-rich region; a zona pellucida domain is essential for the extracellular protein polymerization into helical filaments; and GPI-anchoring site for integrating the protein with the cell membrane [4]. A key structural feature of the uromodulin is rich cysteine amino acid content (48 cysteines) for creating 24 intrachain disulfide bridges, which critical to construct the correct structure [3]. The biosynthesis of this protein and modification occurs in the rough endoplasmic reticulum (RER) of the TAL cells of the kidney.…”

“…The protein precursor (84 kDa) is modified by adding the carbohydrate moiety and GPI anchor-linked molecule to become mature macromolecule with a noticeable mass of 97 kDa. The mature macromolecule once transports across the plasma membrane, cleaved and the free parts secreted with the tubular fluid [3,4]. The uromodulin is existing in urine as a big aggregates or polymeric of glycoprotein, and their molecular weight reached to millions of Daltons.…”