title: Correlation of insulin-enhancing properties of vanadium-dipicolinate complexes in model membrane systems: phospholipid langmuir monolayers and AOT reverse micelles.
abstract: We explore the interactions of V(III) -, V(IV) -, and V(V) -2,6-pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood-glucose-lowering effects of these compounds on STZ-induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self-assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V(III) -phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V(IV) and V(V) -phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V(III) - and V(IV) -dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V(IV) complexes in reverse micelles indicate that the neutral and smaller 1:1 V(IV) -dipic complex penetrates the interface, whereas the larger 1:2 V(IV) complex does not. UV/Vis spectroscopy studies of the anionic V(III) -dipic complex show only minor interactions. These results are in contrast to behavior of the V(V) -dipic complex, [VO2 (dipic)](-) , which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V(III) -, V(IV) -, and V(V) -dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds' efficacy at lowering elevated blood glucose levels in diabetic rats.
authors.affiliation: Chemistry Department, Monmouth College, 700 E. Broadway, Monmouth, IL 61462 (USA).
authors.forename: Audra G
authors.initials: AG
authors.lastname: Sostarecz
authors.forename: Ernestas
authors.initials: E
authors.lastname: Gaidamauskas
authors.forename: Steve
authors.initials: S
authors.lastname: Distin
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Bonetti
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Levinger
authors.forename: Debbie C
authors.initials: DC
authors.lastname: Crans
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D000818:Animals; D056831:Coordination Complexes / Q000737:chemistry / Q000493:pharmacokinetics*; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy; D004143:Dioctyl Sulfosuccinic Acid / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D007004:Hypoglycemic Agents / Q000737:chemistry / Q000493:pharmacokinetics*; D007328:Insulin / Q000378:metabolism; D008567:Membranes, Artificial; D008823:Micelles; D010848:Picolinic Acids; D011725:Pyridines / Q000737:chemistry / Q000493:pharmacokinetics*; D051381:Rats; D014639:Vanadium / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D056831:Coordination Complexes; D007004:Hypoglycemic Agents; D007328:Insulin; D008567:Membranes, Artificial; D008823:Micelles; D010848:Picolinic Acids; D011725:Pyridines; D014639:Vanadium; D004143:Dioctyl Sulfosuccinic Acid; D015060:1,2-Dipalmitoylphosphatidylcholine; C004860:dipicolinic acid
keywords: EPR spectroscopy; Langmuir monolayers; antidiabetic; membrane model; redox state; reverse micelles; vanadium