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. 2010 Jan;59(1):6-16.
doi: 10.2337/db09-0755. Epub 2009 Oct 6.

Grp78 heterozygosity promotes adaptive unfolded protein response and attenuates diet-induced obesity and insulin resistance

Risheng Ye  1 , Dae Young Jung, John Y Jun, Jianze Li, Shengzhan Luo, Hwi Jin Ko, Jason K Kim, Amy S Lee
Affiliations

Grp78 heterozygosity promotes adaptive unfolded protein response and attenuates diet-induced obesity and insulin resistance

Risheng Ye et al. Diabetes. 2010 Jan.

Abstract

Objective: To investigate the role of the endoplasmic reticulum (ER) chaperone glucose-regulated protein (GRP) 78/BiP in the pathogenesis of obesity, insulin resistance, and type 2 diabetes.

Research design and methods: Male Grp78(+/-) mice and their wild-type littermates were subjected to a high-fat diet (HFD) regimen. Pathogenesis of obesity and type 2 diabetes was examined by multiple approaches of metabolic phenotyping. Tissue-specific insulin sensitivity was analyzed by hyperinsulinemic-euglycemic clamps. Molecular mechanism was explored via immunoblotting and tissue culture manipulation.

Results: Grp78 heterozygosity increases energy expenditure and attenuates HFD-induced obesity. Grp78(+/-) mice are resistant to diet-induced hyperinsulinemia, liver steatosis, white adipose tissue (WAT) inflammation, and hyperglycemia. Hyperinsulinemic-euglycemic clamp studies revealed that Grp78 heterozygosity improves glucose metabolism independent of adiposity and following an HFD increases insulin sensitivity predominantly in WAT. As mechanistic explanations, Grp78 heterozygosity in WAT under HFD stress promotes adaptive unfolded protein response (UPR), attenuates translational block, and upregulates ER degradation-enhancing alpha-mannosidase-like protein (EDEM) and ER chaperones, thus improving ER quality control and folding capacity. Further, overexpression of the active form of ATF6 induces protective UPR and improves insulin signaling upon ER stress.

Conclusions: HFD-induced obesity and type 2 diabetes are improved in Grp78(+/-) mice. Adaptive UPR in WAT could contribute to this improvement, linking ER homeostasis to energy balance and glucose metabolism.

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Figures

FIG. 1.
FIG. 1.
Attenuation of diet-induced obesity in Grp78+/− mice. A: Fasting body weight on regular diet (RD) or HFD from 10-week-old mice (n ≥ 7 mice per condition). ○, +/+ HFD; ●, +/− HFD; ▵, +/+ regular diet; ▴, +/− regular diet. B: Body size after 20-week HFD. C: Body composition after 11-week HFD. n = 9 (+/+, □) or 6 (+/−, ■). D: Food intake measurement. n = 7 (+/+, □) or 5 (+/−, ■). E: Oil Red O staining of stool smear from mice on HFD. Negative control: dH2O; positive control: white adipose extract. Data are presented as the means ± SE. *P < 0.05; **P < 0.01 for +/− vs. +/+. (A high-quality color digital representation of this figure is available in the online issue.)
FIG. 2.
FIG. 2.
Enhancement of energy expenditure in Grp78+/− mice. Metabolic cage studies on mice after 10-week HFD (n ≥ 3 mice per condition). A: Energy expenditure. B: O2 consumption and CO2 production. C: Respiratory exchange ratio. D: Total physical activity. Data are presented as the means ± SE. **P < 0.01 for +/− (■) vs. +/+ (□).
FIG. 3.
FIG. 3.
Resistance to HFD-induced diabetic phenotypes in Grp78+/− mice. A: Fasting blood glucose (n ≥ 7 mice per condition). ○, +/+ HFD; ●, +/− HFD; ▵, +/+ regular diet; ▴, +/− regular diet. B: Fasting blood insulin after 19-week HFD. n = 15 (+/+, □) or 16 (+/−, ■). Data are presented as means ± SE. **P < 0.01 for +/− vs. +/+. C–E: Histochemical studies on 25-week-old mice on regular diet (RD) or after 15-week HFD (n ≥ 3 mice per condition). Numbers above scale bars indicate the represented object distance. C: Insulin immunostaining on pancreas. D: Hematoxylin and eosin staining on liver (C and D: Lower panels exhibit the boxed areas within the corresponding upper panels.) E: Hematoxylin and eosin and CD68 staining on WAT. Arrowheads indicate inflammation. (A high-quality color digital representation of this figure is available in the online issue.)
FIG. 4.
FIG. 4.
Grp78 heterozygosity improves insulin sensitivity independently of adiposity. A–C: Hyperinsulinemic-euglycemic clamp studies on 13-week-old +/+ (n = 5) and +/− (n = 4) mice on regular diet (RD). A: Body composition. B: GINF. C: Whole-body glucose turnover and glycolysis during clamps. D: Immortalized Grp78+/− and +/+ MEFs were treated with insulin (100 nmol/l, 15 min) following 5-h serum starvation. Whole cell lysates were subjected to Western blot for phosphorylated (Ser473) and total AKT. Lanes were run on the same gel but noncontiguous. E–H: For 13-week-old mice on regular diet or after 3-week HFD. E: Fasting body weight (HFD). F: Blood glucose (regular diet and HFD). G: Blood insulin (regular diet and HFD). (E–G: n ≥ 6 mice per condition.) H: Insulin tolerance test (HFD). n = 4 (+/+, ○) or 5 (+/−, ●). Data are presented as the means ± SE. *P < 0.05; **P < 0.01 for +/− vs. +/+. □, +/+; ■, +/−.
FIG. 5.
FIG. 5.
Grp78 heterozygosity improves insulin sensitivity predominantly in WAT. A–E: Hyperinsulinemic-euglycemic clamp studies on +/− (■, n = 6) and +/+ (□, n = 9) mice after 10–11 weeks of HFD. A: Whole-body glucose metabolism indicated by GINF and clamp glucose turnover. B: Whole-body glycolysis and glucose anabolism during clamps. C and D: Glucose uptake by white adipose (C), skeletal muscle, and brown adipose (D) during clamps. E: Hepatic glucose production. F and G: Representative Western blots and quantitation of phosphorylation of IRS-1 (Tyr) and AKT (Ser473) in WAT of mice after clamps (n = 4 mice per genotype) (F) and JNK1 in WAT of 25-week-old mice on regular diet (RD) or after 15-week HFD (n = 3–5 mice per condition) (G). □, +/+; ■, +/−. Data are presented as the means ± SE. *P < 0.05; **P < 0.01 for +/− vs. +/+; ##P < 0.01 for HFD vs. regular diet.
FIG. 6.
FIG. 6.
Grp78 heterozygosity promotes adaptive UPR and improves ER homeostasis in WAT. Whole cell lysates were prepared from WAT of 25-week-old mice on regular diet (RD) or after 15-week HFD (n = 4–6 mice per condition) and subjected to Western blotting. The protein loading was normalized against β-actin. Quantitation of relative protein levels of indicated UPR signaling molecules (A) and ER chaperones (B) are presented as the means ± SE. *P < 0.05; **P < 0.01 for +/− vs. +/+; #P < 0.05; ##P < 0.01 for HFD vs. regular diet. □, +/+ regular diet; formula image, +/− regular diet; ▧, +/+ HFD; ■, +/− HFD.
FIG. 7.
FIG. 7.
Grp78 heterozygosity upregulates PGC-1α and GRP75 in WAT. Whole cell lysates from WAT of 25-week-old mice on regular diet (RD) or after 15-week HFD (n = 4–6 mice per condition) were subjected to Western blotting for PGC-1α (A) and GRP75 (B). In the representative blots, lanes that were run on the same gel but noncontiguous are divided by lines. Quantitative protein levels are presented as the means ± SE. *P < 0.05; **P < 0.01 for +/− vs. +/+; #P < 0.05; ##P < 0.01 for HFD vs. regular diet. □, +/+; ■, +/−.
FIG. 8.
FIG. 8.
Overexpression of active ATF6 improves insulin sensitivity in MEFs under ER stress. A HA-tagged nuclear form of ATF6 [ATF6(N)] was overexpressed in immortalized wild-type MEFs via transient transfection 72 h prior to insulin stimulation, controlled by the empty vector. Transfected MEFs were treated with tunicamycin (Tu, 1.5 μg/ml) or DMSO for 14 h before insulin stimulation. Following 5 h serum starvation, cells were treated with insulin (100 nmol/l, 15 min). A: Whole cell lysates were immunoblotted for indicated proteins. B: Quantitation of AKT Ser473 phosphorylation is presented as the means ± SE. *P < 0.05 for +/− vs. +/+; ##P < 0.01 for HFD vs. regular diet. □, vector; ■, ATF6(N).
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References

    1. Kaufman RJ, Scheuner D, Schroder M, Shen X, Lee K, Liu CY, Arnold SM: The unfolded protein response in nutrient sensing and differentiation. Nat Rev Mol Cell Biol 2002;3:411–421 - PubMed
    1. Rutkowski DT, Kaufman RJ: That which does not kill me makes me stronger: adapting to chronic ER stress. Trends Biochem Sci 2007;32:469–476 - PubMed
    1. Ni M, Lee AS: ER chaperones in mammalian development and human diseases. FEBS Lett 2007;581:3641–3651 - PMC - PubMed
    1. Rosen ED, Spiegelman BM: Adipocytes as regulators of energy balance and glucose homeostasis. Nature 2006;444:847–853 - PMC - PubMed
    1. Gregor MF, Hotamisligil GS: Thematic review series: adipocyte biology. Adipocyte stress: the endoplasmic reticulum and metabolic disease J Lipid Res 2007;48:1905–1914 - PubMed

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