Trigonella foenum-graecum seed and 4-hydroxyisoleucine mediates glucose uptake via proximal insulin signaling activation and related downstream gene expression in liver cells.
Fenugreek (Trigonella foenum-graecum) is one of the oldest medicinal plants used worldwide to treat a variety of ailments, including hyperglycaemia. The seed and active compound – 4-hydroxyisoleucine (4-OH-lle) is thought to aid in the treatment of insulin resistance. This study investigated the effects of fenugreek aqueous seed extract and 4-OH-lle, on human liver cells (HepG2) compared to insulin (100ng/ml) and metformin (2mM) controls. Cells were treated with fenugreek seed extract (FSE) and 4-OH-lle: 10 and 100ng/ml under normogylcaemic (5mM glucose) and hyperglycaemic (30mM) conditions for 72h. Tyrosine phosphorylation of insulin receptor-β (IR-β), protein kinase B (Akt) and glycogen synthase kinase-3α/β (GSK-3α/β) protein extracts was determined by western blotting. Gene expression of sterol regulatory element binding protein 1c (SREBP1c), glucose transporter 2 (GLUT2), glycogen synthase (GS) and glucokinase (GK) was evaluated by qPCR. Under normogylcaemic and hyperglycaemic conditions, FSE, 4-OH-lle and insulin at 100ng/ml and metformin (2mM) caused tyrosine phosphorylation of IR-β (p<0.0729; p<0.0121), Akt (p<0.0046; p<0.0005) and GSK-3α/β (p<0.0128; p<0.0048). However, FSE showed the greatest ability in positively controlling GS (*p<0.0262; *p<0.333) and GK (*p<0.333; *p<0.0213), which regulates glycogen synthesis. Also, FSE increased SREBP1c (*p<0.0157; *p<0.0012) which positively regulates GLUT2 (*p<0.0330, *p<0.0417), allowing glucose into the cell. The data suggests that FSE and 4-OH-lle causes an up-regulation of insulin signaling proteins at a proximal level and related downstream gene expression. Taken together, the study suggests that FSE has potential application in the management of chronic hyperglycaemia.