title: Effect of ascorbic acid on microcirculation in patients with Type II diabetes: a randomized placebo-controlled cross-over study.
abstract: Manifestations of vascular disease, including microvascular changes, constitute the major part of the morbidity and mortality in diabetic patients. Oxidative stress has been suggested to play an important role in the vascular dysfunction of diabetic patients. Furthermore, epidemiological observations indicate a beneficial effect of an increased dietary intake of antioxidants. The present study tested the hypothesis that the antioxidant ascorbic acid influences microcirculatory function in patients with Type II diabetes. Patients with Type II diabetes were treated with 1 g of ascorbic acid three times a day for 2 weeks in a randomized placebo-controlled double-blind cross-over design. Microvascular reactivity was assessed by vital capillaroscopy and PRH (post-occlusive reactive hyperaemia). hs-CRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6), IL-1ra (interleukin-1 receptor antagonist) and ox-LDL (oxidized low-density lipoprotein) were analysed. The results showed no significant change in microvascular reactivity assessed after 2 weeks of ascorbic acid treatment. TtP (time to peak) was 12.0+/-3.3 s before and 11.2+/-3.5 s after ascorbic acid (n=17). In comparison, TtP was 11.5+/-2.9 s before and 10.6+/-2.8 s after placebo (not significant). IL-1ra, IL-6, hs-CRP and ox-LDL did not change significantly after ascorbic acid, neither as absolute or relative values. In conclusion, in contrast with some studies reported previously, we could not demonstrate an effect of continuous oral treatment with ascorbic acid on microvascular reactivity assessed at the level of individual capillaries. Furthermore, we found no indication of an effect on inflammatory cytokines or ox-LDL.
authors.affiliation: Division of Clinical Chemistry, Karolinska Institutet, Karolinska University Hospital, Huddinge, Stockholm SE-141 86, Sweden.
authors.forename: Qing
authors.initials: Q
authors.lastname: Lu
authors.forename: Ingemar
authors.initials: I
authors.lastname: Björkhem
authors.forename: Bengt
authors.initials: B
authors.lastname: Wretlind
authors.forename: Ulf
authors.initials: U
authors.lastname: Diczfalusy
authors.forename: Peter
authors.initials: P
authors.lastname: Henriksson
authors.forename: Anna
authors.initials: A
authors.lastname: Freyschuss
mesh_terms: D000975:Antioxidants / Q000627:therapeutic use*; D001205:Ascorbic Acid / Q000627:therapeutic use*; D002097:C-Reactive Protein / Q000032:analysis; D002196:Capillaries; D018592:Cross-Over Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy*; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000187:drug effects; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008297:Male; D008875:Middle Aged; D017472:Receptors, Interleukin-1 / Q000097:blood; D017211:Treatment Failure
chemical_list: D000975:Antioxidants; D015850:Interleukin-6; D008077:Lipoproteins, LDL; D017472:Receptors, Interleukin-1; C099252:oxidized low density lipoprotein; D002097:C-Reactive Protein; D001205:Ascorbic Acid