Anti-inflammatory effect of insulin and its mechanism: An exploratory study / 中国糖尿病杂志

ABSTRACT

Objective To discuss the anti-inflammatory effect and its possible mechanism of different insulin concentration on IκB, NF-κB and TNF-α mRNA in monocytes stimulated by lipopolysaccharide and to detect the key molecule P-Akt in PI3K/ Akt signaling pathway at the cellular level. Methods The peripheral blood (10 ml)is collected from 30 type 2 diabetics (T2DM). Then, the mononuclear cells are centrifugally separated based on density gradient and divided into five different groupsthe control (Con)group; the low concentration insulin 100 mU/L(L-Ins)group; the combination of low concentration insulin 100 mU/L and LY-294002 10 μmol/L(L-Ins+LY) group; the high concentration insulin 1000 mU/L (H-Ins) group, The combination of high concentration insulin 1000 mU/L and LY- 294002 10 μmol/L(H-Ins+LY) group. Two subgroups were set in each category. After incubating for 24 hours, the lipopolysaccharide (100 ng/ml)was added and the mononuclear cell culture of peripheral blood was continued. One hour later, the activities of P-Akt, IκBα and NF-κB of one subgroup were detected using western blot; two hours later, monocytes of the other subgroup were collected and the level of TNF-a mRNA was detected using real-time PCR Results Compared with Con group, the expressions of P-Akt and IkB were higher in L-Ins group and H-Ins group (P<0. 05), the expressions of NF-κB and TNF-a mRNA were lower in L-Ins group and H-Ins group (P<0. 05). Compared with L-Ins group, the expressions of P-Akt and IκB were higher in H-Ins group (P<0. 05), but the expressions of NF-κB and TNF-a mRNA were lower (P< 0. 05). Compared with L-Ins + LY group (H-Ins + LY group), the expressions of IκB and P-Akt were higher(P<0. 05)and the expressions of NF-κB and TNF-a mRNA were lower in L-Ins group (H-Ins group)(P<0. 05). Compared with Con group, no significant variations were shown in the expressions of P-Akt, IkB and NF-κB in L-Ins+LY group and H-Ins+LY group (P>0. 05) except for the high expressions of TNF-a mRNA (P<0. 05). There is no significant difference between L-Ins+LY group and H-Ins+LY group (P>0. 05). Conclusion The direct anti-inflammatory effect of insulin is verified in a dose dependent manner. Insulin may regulate the synthesis and secretion of inflammatory cytokines by activating PI3K/Akt pathway, increasing IkB and affecting the state of NF-κB. Insulin may increase the synthesis and secretion of inflammatory cytokines through other pathways when the PI3K/Akt pathway is blocked.