OBJECTIVE

To investigate the effect of 4-hydroxyisoleucine (4-HIL), an active component of Trigonella Foenum-graecum L. on high glucose induced insulin resistance (IR) in 3T3-L1 adipocytes, and to explore underlying molecular mechanisms.

METHODS

3T3-L1 adipocytes were treated with 25 mmol/L glucose and 0.6 nmol/L insulin to induce IR. They were intervened by different concentrations of 4-HIL (at 5, 10, and 20 micromol/L). [3H]-Deoxy-D-glucose up-taking method was used to detect the glucose uptake. The mRNA expression of cellular tumor necrosis factor-alpha (TNF-alpha) was detected by polymerase chain reaction (PCR). The content of TNF-alpha in the culture supernatant was detected by enzyme-linked immunosorbent assay (ELISA). Palmitic acid (PA) acted as the control.

RESULTS

After intervened by 25 mmol/L glucose and 0.6 nmol/L insulin for 18 h, the insulin-stimulated glucose transportation in 3T3-L1 adipocytes was inhibited by 63%. The mRNA expression of cellular TNF-alpha in adipocytes significantly increased, when compared with that in normal adipocytes (P < 0.05). The level of TNF-alpha secreted in the culture supernatant was increased by 70 pg/mL (P < 0.05). Similar changes occurred in the PA group. After exposure to 4-HIL (5, 10, or 20 micromol/L) for 24 h, the glucose transportation was increased by 35%, 50%, and 60%, respectively. PCR results showed that along with increasing 4-HIL concentrations, the mRNA expression of cellular TNF-alpha showed a decreasing trend, showing statistical difference when compared with the model group and the PA group (P < 0.05). Compared with the model group, the TNF-alpha level in the supernatant was respectively reduced by 10 pg/mL, 18 pg/mL, and 39 pg/mL after intervention (P < 0.05).

CONCLUSIONS

4-HIL could remarkably improve high glucose-induced IR in 3T3-L1 adipocytes. Meanwhile, 4-HIL could inhibit the secretion of TNF-alpha.