Improvement of glucose homeostasis in obese diabetic db/db mice given Plasmodium yoelii glycosylphosphatidylinositols.
We have previously reported that infection with Plasmodium yoelii, Plasmodium chabaudi, or injection of extracts from malaria-parasitized red blood cells induces hypoglycemia in normal mice and normalizes the hyperglycemia in streptozotocin (STZ)-diabetic mice. P yoelii glycosylphosphatidylinositols (GPIs) were extracted in chloroform:methanol:water (CMW) (10:10:3), purified by high-performance thin layer chromatography (HPTLC) and tested for their insulin-mimetic activities. The effects of P yoelii GPIs on blood glucose were investigated in insulin-resistant C57BL/ks-db/db diabetic mice. A single intravenous injection of GPIs (9 and 30 nmol/mouse) induced a significant dose-related decrease in blood glucose (P < .001), but insignificantly increased plasma insulin concentrations. A single oral dose of 2.7 micromol GPIs per db/db mouse significantly lowered blood glucose (P < .01). P yoelii GPIs in vitro (0.062 to 1 micromol/L) significantly stimulated lipogenesis in rat adipocytes in a dose-dependent manner both in the presence and absence of 10(-8) mol/L insulin (P < .01). P yoelii GPIs stimulated pyruvate dehydrogenase phosphatase (PDH-Pase) and inhibited both cyclic adenosine monophosphate (cAMP)-dependent protein kinase A and glucose-6-phosphatase (G6Pase). P yoelii GPIs had no effect on the activity of the gluconeogenic enzymes fructose-1,6-bisphosphatase (FBPase) and phosphoenolpyruvate carboxykinase (PEPCK). This is the first report of the hypoglycemic effect of P yoelii GPIs in murine models of type 2 diabetes. In conclusion, P yoelii GPIs demonstrated acute antidiabetic effects in db/db mice and in vitro. We suggest that P yoelii GPIs, when fully characterized, may provide structural information for the synthesis of new drugs for the management of diabetes.
Department of Immunology and Molecular Pathology, Royal Free and University College London Medical School, Windeyer Institute of Medical Sciences, UK.
K M
KM
Elased
K A
KA
Gumaa
J B
JB
de Souza
J H L
JH
Playfair
T W
TW
Rademacher
D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002855:Chromatography, Thin Layer; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D006597:Fructose-Bisphosphatase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D005952:Glucose-6-Phosphatase / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects*; D007004:Hypoglycemic Agents; D007328:Insulin / Q000097:blood; D008055:Lipids / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D010084:Oxidation-Reduction; D010967:Plasmodium yoelii / Q000737:chemistry*
D001786:Blood Glucose; D017261:Glycosylphosphatidylinositols; D007004:Hypoglycemic Agents; D007328:Insulin; D008055:Lipids; D017868:Cyclic AMP-Dependent Protein Kinases; D006597:Fructose-Bisphosphatase; D005952:Glucose-6-Phosphatase; D005947:Glucose