Siewiera 2018 MiPschool Tromso E2
Event: MiPschool Tromso-Bergen 2018
Metformin is a potent anti-hyperglycaemic agent that effectively decreases diabetes-related cardiovascular complications , however, the mechanism responsible for this beneficial effect is still unknown. In vitro studies have shown that metformin used in high concentrations can inhibit complex I of the mitochondrial chain and reduce mitochondrial membrane potential in blood platelets , as it does in liver or muscle cells . Since blood platelet activation and aggregation are highly energy-depended processes , a mild limitation of respiratory chain by metformin could potentially reduce platelet response to stimulating agents, and - in consequence, reduce the risk of cardiovascular complications. Our aim was to evaluate in vivo the effect of metformin on blood platelet mitochondrial respiration and on blood platelet activation and aggregation.
For this purpose sixty 2-month-old Sprague–Dawley rats were randomly allocated into healthy and diabetic groups. In order to induce diabetes the animals were intraperitoneally injected with streptozotocin (STZ) at a dose of 65 mg/kg b.w., while the control group received only a vehicle (0.1 mol/l citrate buffer). After 1-month of confirmed diabetes, animals were divided into four groups: (1) healthy (non-diabetic) rats – not treated with metformin; (2) healthy animals that were given metformin in a dose of 50 mg/kg b.w./day for 4 months; (3) untreated diabetic rats; (4) diabetic rats treated with metformin at a dose of 50 mg/kg b.w./day for 4 months. Animals that survived the experiment were anaesthesized and the blood was collected from the abdominal aorta onto 3.2% sodium citrate. Blood platelets were isolated using a multiple-stage centrifugation procedure. The mitochondrial respiration parameters in intact and permeabilized blood platelets were monitored with the use of high resolution respirometry (Oxygraph-2k, Oroboros Instruments, Innsbruck, Austria). Collagen-stimulated platelet aggregation was monitored with the use Multiplate® analyzer (Roche Diagnostics, Mannheim, Germany). Platelet activation and reactivity to physiological agonists (collagen, thrombin or ADP) were evaluated by the flow cytometric determination of the expressions of platelet surface activation marker (CD62P). Blood samples were examined with the automated haematology analyzer (ABX Micros 60, HORIBA ABX SAS, France).
Four-month treatment with metformin resulted in a small, but statistically significant (p <0.05) decrease in blood glucose concentration in STZ-diabetic animals compared to non-treated diabetic group (501 [478 – 509.5] mg/dl vs. 473.5 [463.75 – 485.5] mg/dl, respectively). However, our results indicate that the treatment with metformin at dose 50 mg/kg b.w./day for 4 months is not sufficient to modify platelet mitochondria respiration or collagen-stimulated platelet aggregation in control and STZ-diabetic rats. Since, the mechanism of metformin action is underlied by its accumulation in cells, we conclude that probably a higher dose is needed to observed beneficial effects in STZ-diabetic rats, including better glycemic control.
Siewiera K(1), Labieniec-Watala M(2), Polak D(1), Wolska N(1), Kassassir H(1), Watala C(1)
- Dept Haemostasis Haemostatic Disorders, Chair Biomedical Sciences, Medical Univ Lodz
- Fac Biol Environmental Protection, Dept Medical Biophysics, Univ Lodz; Lodz, Poland. - firstname.lastname@example.org
The study is supported by the National Centre of Science (NCN 2015/17/N/NZ5/02603 and NCN 2016/20/T/NZ3/00505) and by COST Action CA15203 MitoEAGLE.
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Labels: MiParea: Respiration, Pharmacology;toxicology Pathology: Diabetes
Organism: Rat Tissue;cell: Platelet Preparation: Intact cells, Permeabilized cells
HRR: Oxygraph-2k Event: E2