Ascorbic Acid Metabolism in Diabetes Mellitus^a

Abstract

Competition for membrane transport between glucose and ascorbic acid (AA) has been shown in vitro in human lymphocytes, granulocytes, and fibroblasts. Therefore, we examined the effects of acute administration of i.v. glucose on AA levels in mononuclear (MNL) and polymorphonuclear leukocytes (PMN) and on leukocyte chemotaxis. Plasma glucose and AA, MNL AA, PMN AA, and chemotaxis by MNL and PMN were measured before and after i.v. glucose in fasted normal male volunteers. A decline in AA occurred in PMN as well as MNL, but decreases in AA induced acutely by transient hyperglycemia were not associated with changes in chemotaxis. However, under conditions of prolonged hyperglycemia maintained by a glucose clamp technique, significant changes (p less than 0.01) in chemotaxis by both PMN and MNL were observed after 210 and 240 min, with changes in chemotaxis to several chemoattractants significantly correlated with decreases in intracellular AA after 240 min (p less than 0.05). These results are consistent with the hypothesis that chronic hyperglycemia may be associated with intracellular deficits of leukocyte AA, an impaired acute inflammatory response, and altered susceptibility to infection and faulty wound repair in patients with diabetes.

Ascorbic Acid Concentrations in Umbilical Cord Veins and Arteries of Preterm and Term Newborns

“…2b) is supported by previously reported data [28,[35][36][37]. Sev eral addition factors such as, glucose competi tion with AA for membrane transport [17], iron overload [38][39][40], maternal age, parity and nutrition strongly influences the AA sta tus of the newborn [28].…”

“…Ascorbic acid (AA) is a water-soluble, chain-breaking molecule [2][3][4][5][6][7] which func tions as an outstanding antioxidant in human plasma [8][9][10][11], It is accumulated by various tissues including, but not limited to, the lungs, eyes and brain; as well as by leukocytes [12][13][14][15], particularly in the retina where concen trations are usually higher (approximately 3-10 times) than plasma [16], In addition, AA has been reported to improve impaired bacte ricidal activity and to clinically decrease the frequency of infection [17]; to inhibit the pro duction of broncho-constrictive prostanoids and histamine [14]; to protect ocular tissues against the deleterious effects of oxidative reactions and free radicals [13], and to be associated with a decreased incidence of pre mature rupture of membranes in pregnant women [18]. Other reports have suggested that an association exists between low plasma AA levels and an increased incidence of spon taneous abortion [19], premature birth and low birth weight [ 18,20].…”

The Pathogenesis of Diabetic Foot Problems: An Overview

“…A number of inherent immunological abnormalities have been documented in diabetes, and several studies have shown an increased infection rate in postoperative wounds (39). Neutrophil function is impaired, with abnormalities of adherence, chemotaxis, phagocytosis, and killing ability (40), and these may be partly due to ascorbic acid transport defects (41). We have recently looked at transforming growth factor (TGF)-p in diabetic foot ulcers, as TGF-(3 is known to be central to the process of wound healing (42).…”

Disturbances of micronutrient and antioxidant status in diabetes

“…Vitamin C has also been implicated in long-term complications of diabetes through effects of AA deficiency on collagen abnormalities (McLennan et al 1988). immune function (Pecoraro & Chen, 1987) and platelet activation (Sarji er al. 1979).…”