Oestrogen improves glucose metabolism and insulin signal transduction in HepG2 cells

Abstract

1. Many clinical studies have suggested a relationship between oestrogen and insulin sensitivity. In the present study, HepG2 cells were divided into four groups: (i) control, incubated with 1 nmol/L insulin; (ii) the HI group, which was incubated with 100 nmol/L insulin to induce insulin resistance; (iii) the E2 group, in which control cells were incubated with 1 nmol/L insulin plus 1 nmol/L oestradiol; and (iv) the HI + E2 group, in which insulin-resistant cells were incubated with 100 nmol/L insulin + 1 nmol/L oestradiol. 2. A high concentration of insulin decreased the activity of phosphofructo-1-kinase (PFK), pyruvate dehydrogenase (PDH) and glycogen synthase (GS), as well as decreasing the expression of insulin receptor (IR) and insulin receptor substrate-2 (IRS-2). High insulin had no effect on glucose transport or the expression of insulin receptor-1 (IRS-1). 3. The addition of oestradiol to control cells increased glucose transport, the activity of PFK, PDH and GS and the expression of IRS-1 and IRS-2, but had no effect on the expression of IR. 4. Treatment of insulin-resistant HepG2 cells with oestradiol attenuated HI-induced decreases, except for IR, and the expression of IRS-1 was significantly higher than control, attaining levels seen in group 3. The expression of IRS-2 was significant higher than in insulin-resistant cells, but did not reach control levels. Changes in the activity of PFK, PDH and GS were the same as the changes seen in the expression of IRS-2. 5. These results suggest that high concentrations of insulin induce insulin resistance in HepG2 cells, whereas oestradiol improves glucose metabolism and insulin signal transduction of cells by enhancing the activity of key enzymes involved in glucose metabolism and the expression of IRS-1 and IRS-2.

A strategy for improving FDG accumulation for early detection of metastasis from primary pancreatic cancer: Stimulation of the Warburg effect in AsPC-1 cells

“…c o m / l o c a t e / n u c m e d b i o dehydrogenase-triosephosphate isomerase, and the other chemicals were purchased from Sigma-Aldrich Japan (Tokyo, Japan). The radiolabeled compounds 14 C-FDG, 14 C-maltose, and 14 C-inulin were purchased from American Radiolabeled Chemicals Co. (St. Louis, MO, USA).…”

“…14 C-FDG accumulation experiments were performed according to previously reported methods, with modifications [14,15]. For timecourse experiments, AsPC-1 cells were rinsed with D-PBS and then incubated with 2 ml D-PBS containing 14 C-FDG ( 14 C-FDG D-PBS; 9.25 kBq/ dish) at 37°C for a specific period (15 to 180 min).…”

“…For timecourse experiments, AsPC-1 cells were rinsed with D-PBS and then incubated with 2 ml D-PBS containing 14 C-FDG ( 14 C-FDG D-PBS; 9.25 kBq/ dish) at 37°C for a specific period (15 to 180 min). The 14 C-FDG D-PBS was then removed by aspiration, and the cells were immediately rinsed twice with 5 ml ice-cold D-PBS.…”

“…To confirm the competitive effects of hexoses on 14 C-FDG transport into AsPC-1 cells, the following modifications were incorporated into competitive inhibition experiments: 1) 14 2.6. 6-Phosphofructo-1-kinase activity in pretreated AsPC-1 cells…”

“…PFK-1 activity in the supernatants was measured as previously described [14]. The reaction mixture contained 50 mM Tris-HCl (pH 8.0), 1 mM EDTA, 2 mM MgCl 2 , 2 mM DTT, 5 mM (NH 4 ) 2 SO 4 , 1 mM D-Fru-6-P, 1.2 mM adenosine 5′-triphosphate, 0.2 mM reduced nicotinamide adenine dinucleotide (NADH), 0.8 U/ml aldolase, 0.8 U/ml α-glycerophosphate dehydrogenase, and 8.7 U/ml triosephosphate isomerase in a final volume of 1 ml.…”