Author + information
- Zhao Huishou and
- Tao Ling
To investigate the effect of BCAA on liver insulin sensitivity, and to investigate whether BCAA contributes to the development of liver insulin resistance through changing the protein level of AKT and the isoforms.
HepG2 cells were divided into control group, palmitate treatment group, BCAA+ palmitate treatment group, the effect of BCAA on palmitate induced HepG2 cells insulin resistance were detected; HepG2 cells were divided into different concentrations of BCAA treatment groups and BCAA+ BT2 treatment group, the effect of of BCAA on the protein level of AKT, mTORC2 and mRNA level of AKT1, AKT2 and AKT3 in HepG2 cells were detected; the effect of prolonged rapamycin incubation and ubiquitin-proteasome inhibitor PYR41 and MG132 on BCAA induced downregulation of AKT protein level was detected.
60 healthy C57BL/6 male mice of 8 weeks old were divided into four groups, respectively. And were offered a choice of normal diet+tap water (ND group), normal diet+tap water containing 5% BCAA (ND/BCAA group), high fat diet+tap water (HD group), high fat diet+tap water containing 5%BCAA (HD/BCAA group). The body weight of mice were weekly recorded until 18 weeks; Intraperitoneal glucose tolerance and insulin tolerance were detected;Serum BCAA level and insulin level were detected. Hepatic insulin signaling pathway, and AKT2 protein levels in mice were detected by Western blot.
1.BCAA promoted palmitate induced insulin resistance in HepG2 cells by downregulation of AKT/AKT2 protein level.
BCAA induced downregulation of AKT and p-AKT(ser473) protein level in HepG2 cells, besides, AKT2 protein levels were significantly downregulated, which promoted palmitate induced HepG2 cells insulin resistance; BCAA induced degradation of AKT by ubiquitin-Proteasome dependent pathway through down-regulation of mTORC2 in HepG2 cell. Rictor, the major component of mTORC2, were significantly down-regulated in HepG2 cells after BCAA incubation for 24 h. And this can be reversed by ubiquitin activating enzyme E1 inhibitor PYR41 and proteasome inhibitor MG132.
2.BCAA promoted high fat diet induced hepatic insulin resistance in mice by down regulating AKT2 protein.
BCAA inhibited high fat diet induced body weight gain in mice by inhibited the food intake.; The mice serum BCAA and insulin level significantly increased after high fat diet feeding for 18 weeks, and the serum BCAA concentration in HD/BCAA group increased further. Hepatic insulin resistance were significantly exacerbated compared with HD group; BCAA promoted high fat diet induced mice liver insulin resistance through down-regulation of AKT2.
BCAA promoted the high fat diet induced hepatic insulin resistance in C57BL/6 mice. The mechanism may be that BCAA induced down-regulation of AKT2 in mice liver, exacerbating the development of liver insulin resistance.