Expression of cardiac insulin signalling genes and proteins in rats fed a high-sucrose diet: effect of bilberry anthocyanin extract

Shamjeet Singh, Thomas Netticadan, D. Dan Ramdath

Insulin resistance is associated with impaired cardiac function, but the underlying molecular abnormalities are largely unexplained. Bilberry anthocyanin (BAcn) may be protective, as it appears to potentiate insulin action. Rats were randomly allocated to control, sucrose-fed (SF) or sucrose-fed + BAcn diets (SF-A) for 15 weeks. Cardiac insulin signalling genes and proteins were quantified using reverse transcription quantitative real-time polymerase chain reaction and western blots. Glucose tolerance was not different with treatment. SF showed lower (p < 0.05) ferric reducing antioxidant power, which increased with BAcn. SF resulted in significantly decreased (p < 0.05) expression of 10 genes: acetyl-coenzyme A carboxylase alpha; V-Akt murine thymoma viral oncogene homolog 1; Bcl2-like 1; cytosine-cytosine-adenosine-adenosine-thymidine/enhancer binding protein; FK506 binding protein 12-rapamycin associated; glycerol-3-phosphate dehydrogenase 1 (soluble); solute carrier family 2 (facilitated glucose transporter), member 1, 4; hexokinase 2; and thyroglobulin. SF-A prevented these changes. Compared to SF-A, SF up-regulated (p < 0.05) complement factor D and phosphoinositide-3-kinase, regulatory subunit1 (α); sterol regulatory element binding transcription factor 1 was down-regulated (p < 0.05). SF increased (p < 0.05) cardiac phospholamban and decreased phosphorylated troponin I, which were not attenuated by BAcn. Compared to control or SF, SF-A resulted in significantly lower (p < 0.05) 5'-AMP-activated protein kinase. SF lowered antioxidant capacity and changed the expression of insulin signalling genes, which were modulated by BAcn.