Yaohui Wang's research while affiliated with The National Institute of Diabetes and Digestive and Kidney Diseases and other places
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Publications (31)
Background:
Reduced plasma vitamin C (vitC) concentrations in HIV may result from abnormal urinary excretion: a renal leak. VitC renal leak indicates underlying nutritional dysregulation independent of diet. We hypothesized that increased renal leak prevalence in HIV would be associated with deficient vitC concentrations.
Methods:
We conducted a...
Background:
Reduced plasma vitamin C concentrations in chronic diseases may result from abnormal urinary excretion of vitamin C: a renal leak. We hypothesized that vitamin C renal leak may be associated with disease-mediated renal dysregulation, resulting in aberrant vitamin C renal reabsorption and increased urinary loss.
Objectives:
We investi...
Objectives
Reduced plasma vitamin C concentrations in chronic diseases may result from abnormal urinary excretion of vitamin C excretion: a renal leak. We hypothesized that vitamin C renal leak may be the consequence of disease-mediated dysregulation affecting the renal tubules, resulting in aberrant vitamin C renal reabsorption and increased urina...
Background:
Diabetes is associated with low plasma vitamin C concentrations.
Objectives:
We investigated the contribution of dysregulated vitamin C renal physiology, its prevalence, and associated clinical characteristics.
Methods:
An essential prerequisite was determination of normal vitamin C renal threshold, the plasma concentration at whic...
Strategies to prevent diabetic microvascular angiopathy focus on the vascular endothelium. Because red blood cells (RBCs) are less deformable in diabetes, we explored an original concept linking decreased RBC deformability to RBC ascorbate and hyperglycemia. We characterized ascorbate concentrations from human and mouse RBCs and plasma, and showed...
Although vitamin C (ascorbate) is present in whole blood, accurate measurements in red blood cells (RBCs) are problematic because of assay interferences, limited sensitivity, and sample volume requirements. We describe a new technique for ascorbate measurement in RBCs of humans, wild type mice, and mice unable to synthesize ascorbate. Exogenously a...
This study was performed to quantify the fraction of excreted creatinine not attributable to creatinine filtration for accurately determining the glomerular filtration rate in mice. To measure this we compared creatinine filtration with the simultaneous measurement of inulin clearance using both single-bolus fluorescein isothiocyanate (FITC)-inulin...
Levels of the necessary nutrient vitamin C (ascorbate) are tightly regulated by intestinal absorption, tissue accumulation, and renal reabsorption and excretion. Ascorbate levels are controlled in part by regulation of transport through at least 2 sodium-dependent transporters: Slc23a1 and Slc23a2 (also known as Svct1 and Svct2, respectively). Prev...
Previous experiments from our laboratory have shown that about 50% of urinary creatinine excretion is derived from tubular secretion. In the present study we determined gender differences in creatinine excretion and examined the effect of cimetidine on creatinine excretion. Under anesthesia C57 mice were infused with 0.5 % FITC‐inulin at 0.25 μl/mi...
When vitamin C intake is from foods, fasting plasma concentrations do not exceed 80 micromol/L. We postulated that such tight control permits a paracrine function of vitamin C.
The purpose of this study was to determine whether paracrine secretion of vitamin C from the adrenal glands occurs.
During diagnostic evaluation of 26 patients with hyperald...
Endothelial dysfunction is a hallmark of Type 2 diabetes related to hyperglycemia and oxidative stress. Nitric oxide-dependent vasodilator actions of insulin may augment glucose disposal. Thus endothelial dysfunction may worsen insulin resistance. Intra-arterial administration of vitamin C improves endothelial dysfunction in diabetes. In the presen...
Vitamin C at high concentrations is toxic to cancer cells in vitro. Early clinical studies of vitamin C in patients with terminal cancer suggested clinical benefit, but 2 double-blind, placebo-controlled trials showed none. However, these studies used different routes of administration.
To determine whether plasma vitamin C concentrations vary subs...
Vitamin C in humans must be ingested for survival. Vitamin C is an electron donor, and this property accounts for all its known functions. As an electron donor, vitamin C is a potent water-soluble antioxidant in humans. Antioxidant effects of vitamin C have been demonstrated in many experiments in vitro. Human diseases such as atherosclerosis and c...
The only proven requirement for ascorbic acid (vitamin C) is in preventing scurvy, presumably because it is a cofactor for hydroxylases required for post-translational modifications that stabilize collagen. We have created mice deficient in the mouse ortholog (solute carrier family 23 member 1 or Slc23a1) of a rat ascorbic-acid transporter, Svct2 (...
The only proven requirement for ascorbic acid (vitamin C) is in preventing scurvy1,
2, presumably because it is a cofactor for hydroxylases required for post-translational modifications that stabilize collagen3. We have created mice deficient in the mouse ortholog (solute carrier family 23 member 1 or Slc23a1) of a rat ascorbic-acid transporter, S...
Recommendations for vitamin C intake are under revision by the Food and Nutrition Board of the National Academy of Sciences. Since 1989 when the last recommended dietary allowance (RDA) of 60 mg was published, extensive biochemical, molecular, epidemiologic, and clinical data have become available. New recommendations can be based on the following...
This chapter proposes that ideal vitamin intake should be based on how different vitamin concentrations affect vitamin function. Detection of nutrient action should be targeted to specific biochemical and molecular action of the nutrient. Vitamin function should be studied in situ (i.e., in position). “In situ” refers to organelles, cells, animals,...
Recommendations for vitamin intake can be based on the biochemical and clinical criteria of in situ kinetics. This chapter focuses on those clinical criteria that delineate vitamin absorption and distribution. These criteria describe vitamin pharmacokinetics. Pharmacokinetics for vitamins describes steady-state concentration in plasma as a function...
Citations
... Renal leak assessment in chronic disease serves two key functions. First, renal leak characterizes the scope and contribution of abnormal vitamin C urinary loss to low vitamin C concentrations 12,15 . Second, because renal leak incorporates both fasting plasma and urine measurements using a specific vitamin C assay, renal leak outcomes are effective means of investigating disease-specific factors that contribute to vitamin C nutritional pathophysiology and disease pathogenesis 12,15 . ...
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... Additionally, the excessive formation of free radicals related to hyperglycemia can further diminish the antioxidant capacity of vitamin C, leading to vitamin C depletion [56]. T2DM may also be associated with decreased renal reuptake of vitamin C, and diabetic patients with microalbuminuria may excrete more vitamin C in their urine [57]. ...
... Mice kidneys secrete a substantial amount of creatinine(7). Therefore the urine I Ϫ /creatinine ratio should overestimate the amount of I Ϫ absorbed. ...
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... It mostly occurs in epithelial tissues such as the intestine, lung, liver, kidney, and skin, where it is involved in the absorption and (renal) reabsorption of Asc to maintain the whole-body homeostasis (106,161,170,171). Knockout of the SVCT1 transporter gene resulted in 7-10-fold higher urinary loss and 50-70% lower blood level of vitamin C in mice compared to wild-type littermates (33). SVCT2 can be characterized by lower capacity and higher affinity (K M : 8-115 lM) than SVCT1. ...
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... This hypothesis relies on the observation that vitamin C deficiency in mice or humans is correlated to anaemia and haemolysis [18,90]. More recently, a comprehensive study investigated the connection between GLUT1, DHA transport and diabetes [123]. It was observed that hyperglycaemia is inversely related to the ascorbate concentration in red blood cells and that the low ascorbate concentration was associated with strong haemolysis. ...
... Vitamin C is an important antioxidant nutrient required for many enzymatic functions in humans 1,2 . Low vitamin C concentration in chronic diseases, even if nondeficient, may have consequences for disease pathogenesis and wellbeing [3][4][5][6] . Cohorts with HIV have been shown to have lower vitamin C concentrations compared to seronegative controls, even with optimal dietary intake [7][8][9][10][11] . ...
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... Another explanation is based on studies linking low vitamin C concentrations with impaired RBC structure and function. In vivo studies have shown that low vitamin C concentrations are associated with increased RBC rigidity, osmotic fragility, and hemolysis [36]. These potential explanations can be explored in mouse models and prospective longitudinal clinical studies. ...
... Recent studies provided data on some of these aspects (20,21). However, clinical outcome studies are needed to determine the optimal intake of vitamin C in health and disease (134). ...
Reference: Vitamin C
... Antioxidant vitamin plasma levels are the most used parameters to determine their nutritional status. However, leukocytes, like neutrophils, are believed to better reflect tissue concentrations of ascorbate and vitamin E content [36]. Intense exercise induces the degranulation of neutrophils, which leads to an increase of the plasma concentration of marker neutrophil enzymes (elastase and MPO) [8] The increase in circulating neutrophils, and plasma MPO concentration after the half marathon, reflect neutrophil mobilization and priming for oxidative activity due to intense exercise. ...
... Vitamin C content (VC) was determined with the methodology reported by Padayatt et al. [22]. A total of 10 g of the weight of fresh fruit were weighed and placed in a mortar and crushed with 10 mL of hydrochloric acid at 2% (v/v). ...
