title: Effects of two weeks of metformin treatment on whole-body glycocalyx barrier properties in db/db mice.
abstract: BACKGROUND
  The anti-diabetic drug metformin has been demonstrated to exert a protective effect against vascular complications in diabetes independent of its glucose lowering action. Since the endothelial glycocalyx has been indicated to have important vasculoprotective properties and to be vulnerable to degradation by hyperglycemic conditions, we evaluated in the current study the effect of short-term metformin treatment on whole-body glycocalyx barrier properties in a mouse model of non-insulin dependent diabetes mellitus (db/db mouse).
  
  
  METHODS
  Glycocalyx barrier properties were measured in an acute experiment in three groups of mice: 1) db/db mice without treatment serving as controls, 2) db/db mice which received metformin for two weeks in the drinking water serving as experimental group, and 3) C57Bl/6 mice serving as reference group. Animals were put under anesthesia (ketamine, medetomidine, and atropine) and carotid artery blood pressure was continuously monitored. To probe the glycocalyx a mixture of the tracers FITC-labeled 70 kDa dextrans (Dex70) or fluorescein-labeled red blood cells (RBCs) versus Texas Red-labeled 40 kDa dextrans (Dex40) was infused and blood samples subsequently collected for 30 min to determine the initial vascular distribution volume and clearance of these tracers. Urine was collected and dry-to-wet weight of heart and kidney were determined after the experiment. Group differences were tested using unpaired t-tests.
  
  
  RESULTS
  Metformin treatment did not affect body weight, fasting blood glucose and arterial blood pressure. Compared to C57Bl/6 mice, db/db mice showed a diminished initial exclusion and increased vascular clearance of Dex70 versus Dex40 (P < 0.05), and both were improved by the metformin treatment (P < 0.05). While urine production was higher in the db/db mice compared to C57Bl/6 (P < 0.05), heart and kidney of the metformin treated animals showed comparable dry-to-wet weights compared to the C57Bl/6 mice.
  
  
  CONCLUSIONS
  Two weeks of metformin in the drinking water is associated with an improvement in glycocalyx barrier properties in db/db mice, as evidence by an enhanced exclusion and retention of 70 kDa dextrans in the vasculature. In addition, metformin improved hydration of heart and kidney. Previous reported cardiovascular benefits of metformin may well involve an improvement of the endothelial glycocalyx.
authors.forename: Bart J M
authors.initials: BJ
authors.lastname: Eskens
authors.forename: Coert J
authors.initials: CJ
authors.lastname: Zuurbier
authors.forename: Judith
authors.initials: J
authors.lastname: van Haare
authors.forename: Hans
authors.initials: H
authors.lastname: Vink
authors.affiliation: Department of Physiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, PO Box 616, 6200, MD Maastricht, The Netherlands. J.vanTeeffelen@maastrichtuniversity.nl.
authors.forename: Jurgen W G E
authors.initials: JW
authors.lastname: van Teeffelen
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D019276:Glycocalyx / Q000187:drug effects* / Q000378:metabolism; D006439:Hemodynamics / Q000187:drug effects; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D013997:Time Factors; D014554:Urination / Q000187:drug effects; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D008687:Metformin