[Effects of small GTP-binding protein GDP dissociation stimulator on adipocyte hypertrophy and glucose metabolism disorder in mice].

To explore the effect and mechanism of small GTP-binding protein GDP dissociation stimulator (SmgGDS) on the development of obesity. (1) 8-week-old C57BL/6J mice were randomly assigned to normal diet and high fat diet group, with 6 mice in each group. They were fed regular feed and a high fat diet containing 60% fat for 4 months, respectively. The expression of SmgGDS in epididymal adipose tissue (eWAT), liver, and skeletal muscle were measured using Western-blot. (2) 6-week-old wild-type (WT) and SmgGDS knockdown (KD) mice were divided into four groups, each receiving high fat diet for 4 months (7 in each group) and 7 months (9 in each group). Glucose tolerance test (GTT) and insulin tolerance test (ITT) were conducted; The weight, adipose tissue, and liver weight of mice were recorded; HE staining examined adipose tissue structural changes; Western-blot determined extracellular signal-regulated kinase (ERK) 1/2 phosphorylation levels in eWAT; Real time fluorescence quantitative polymerase chain reaction (RT-qPCR) was used to detect mRNA levels of CCAAT/enhancer binding protein α (C/EBPα), C/EBPβ and peroxisome proliferator activated receptor γ (PPARγ) in eWAT. (3) Mouse embryonic fibroblasts (MEFs) extracted from WT and KD mice were induced for differentiation. Oil red O staining and Western-blot were used to detect lipid droplet and expression of SmgGDS and phospho-ERK; C/EBPα, C/EBPβ and PPARγ mRNA levels were measured using RT-qPCR. (4) 10-week-old C57BL/6J mice were randomly assigned into two groups, with 7 mice in each group. Mice were infected with SmgGDS overexpressing adeno-associated virus (AAV-SmgGDS) or empty vector intraperitoneally, then fed with high fat diet. After 4 weeks, performed GTT and ITT; Recorded the weight and adipose tissue weight of mice; HE staining was used to analyze structural changes of eWAT; Western-blot was used to detect the phosphorylation level of ERK in eWAT. (1) The expression of SmgGDS was significantly upregulated in eWAT of high fat diet fed mice (normal diet group: 0.218±0.037, high fat diet group:0.439±0.072, =2.74, =0.034). (2) At 4 months of high fat diet intervention, the glucose tolerance (60 minutes after glucose injection, WT group: 528 mg/dl±21 mg/dl, KD group: 435 mg/dl±17 mg/dl, =3.47, =0.030; 90 minutes, WT group: 463 mg/dl±24 mg/dl, KD group: 366 mg/dl±18 mg/dl, =3.23, =0.047;120 minutes, WT group: 416 mg/dl±21 mg/dl, KD group: 297 mg/dl±16 mg/dl, =4.49, =0.005) and insulin sensitivity (15 minutes after insulin injection, WT group: 77.79%±3.45%, KD group: 54.30%±2.92%, =3.49, =0.005; 30 minutes, WT group: 62.27%±5.31%, KD group: 42.25%±1.85%, =2.978, =0.024; 90 minutes, WT group: 85.69%±6.63%, KD group: 64.71%±5.41%, =3.120, =0.016) of KD mice were significantly improved compared to the WT group, with an increase in eWAT weight ratio (WT: 4.19%±0.18%, KD: 5.12%±0.37%, =2.28, =0.042), but a decrease in average adipocyte area (WT group: 5221 μm²±241 μm², KD group: 4410 μm²±196 μm², =2.61, =0.026). After 7 months of high fat diet, the eWAT weight ratio of KD mice decreased (WT: 5.02%±0.20%, KD: 3.88%±0.21%, =3.92, =0.001) and adipocyte size decreased (WT group: 6 783 μm²±390 μm², KD group: 4785 μm²±303 μm², =4.05, =0.002). The phospho-ERK1 in eWAT increased (WT group: 0.174±0.056, KD group: 0.588±0.147, =2.64, =0.025), and mRNA level of PPARγ significantly decreased (WT group: 1.018±0.128, KD group: 0.029±0.015, =7.70, =0.015). (3) The expression of SmgGDS was significantly increased in differentiated MEF (undifferentiated: 6.789±0.511, differentiated: 10.170±0.523, =4.63, =0.010); SmgGDS knock-down inhibited lipid droplet formation in MEF (WT group: 1.00±0.02, KD group: 0.88±0.02, =5.05, =0.007) and increased ERK1 (WT group: 0.600±0.179, KD group: 1.325±0.102, =3.52, =0.025) and ERK2 (WT group: 2.179±0.687, KD group: 5.200±0.814, =2.84, =0.047) activity, which can be reversed by ERK1/2 inhibitor. (4) SmgGDS over expression resulted in weight gain, increased eWAT weight (control group: 3.29%±0.36%, AAV-SmgGDS group: 4.27%±0.26%, =2.20, =0.048) and adipocyte size (control group: 3525 μm²±454 μm², AAV-SmgGDS group: 5326 μm²±655 μm², =2.26, =0.047), impaired insulin sensitivity(30 minutes after insulin injection, control group: 44.03%±4.29%, AAV-SmgGDS group: 62.70%±2.81%, =3.06, =0.019), and decreased ERK1 (control group: 0.829±0.077, AAV-SmgGDS group: 0.326±0.036, =5.96, =0.001)and ERK2 (control group: 5.748±0.287, AAV-SmgGDS group: 2.999±0.845, =3.08, =0.022) activity in eWAT. SmgGDS knockdown improves obesity related glucose metabolism disorder by inhibiting adipogenesis and adipose tissue hypertrophy, which is associated with ERK activation.