Involvement of Inducible 6-Phosphofructo-2-kinase in the Anti-diabetic Effect of Peroxisome Proliferator-activated Receptor γ Activation in Mice

Xin Guo,Kefeng Xu,Jifeng Zhang,Honggui Li,Weiyu Zhang,Huan Wang,Alex J Lange,Y Eugene Chen,Yuqing Huo,Chaodong Wu

doi:10.1074/jbc.m110.123174

Abstract

PFKFB3 is the gene that codes for the inducible isoform of 6-phosphofructo-2-kinase (iPFK2), a key regulatory enzyme of glycolysis. As one of the targets of peroxisome proliferator-activated receptor gamma (PPARgamma), PFKFB3/iPFK2 is up-regulated by thiazolidinediones. In the present study, using PFKFB3/iPFK2-disrupted mice, the role of PFKFB3/iPFK2 in the anti-diabetic effect of PPARgamma activation was determined. In wild-type littermate mice, PPARgamma activation (i.e. treatment with rosiglitazone) restored euglycemia and reversed high fat diet-induced insulin resistance and glucose intolerance. In contrast, PPARgamma activation did not reduce high fat diet-induced hyperglycemia and failed to reverse insulin resistance and glucose intolerance in PFKFB3(+/-) mice. The lack of anti-diabetic effect in PFKFB3(+/-) mice was associated with the inability of PPARgamma activation to suppress adipose tissue lipolysis and proinflammatory cytokine production, stimulate visceral fat accumulation, enhance adipose tissue insulin signaling, and appropriately regulate adipokine expression. Similarly, in cultured 3T3-L1 adipocytes, knockdown of PFKFB3/iPFK2 lessened the effect of PPARgamma activation on stimulating lipid accumulation. Furthermore, PPARgamma activation did not suppress inflammatory signaling in PFKFB3/iPFK2-knockdown adipocytes as it did in control adipocytes. Upon inhibition of excessive fatty acid oxidation in PFKFB3/iPFK2-knockdown adipocytes, PPARgamma activation was able to significantly reverse inflammatory signaling and proinflammatory cytokine expression and restore insulin signaling. Together, these data demonstrate that PFKFB3/iPFK2 is critically involved in the anti-diabetic effect of PPARgamma activation.

Highlights

The abbreviations used arePPAR␥, peroxisome proliferator-activated receptor ␥; iPFK2, inducible 6-phosphofructo-2-kinase; F26P2, fructose2,6-bisphosphate; TZD, thiazolidinedione; GyK, glycerol kinase; PEPCK, phosphoenolpyruvate carboxykinase; ROS, reactive oxygen species; JNK, c-Jun N-terminal kinase; NF-␬B, nuclear factor ␬B; TNF␣, tumor necrosis factor ␣; IL-6, interleukin-6; free fatty acids (FFA), free fatty acid(s); HFD, high fat diet; PBS, phosphate-buffered saline; KD, kinase-dead; Ctrl, control; RT, reverse transcription
PFKFB3 is the gene that codes for the inducible isoform of 6-phosphofructo-2-kinase, a key regulatory enzyme of glycolysis
Using PFKFB3/iPFK2-disrupted mice, the present study demonstrates that PFKFB3/iPFK2 is involved in the anti-diabetic effect of PPAR␥ activation, probably by increasing the ability of adipose tissue to store fat and by suppressing adipose tissue inflammatory response

Summary

The abbreviations used are

PPAR␥, peroxisome proliferator-activated receptor ␥; iPFK2, inducible 6-phosphofructo-2-kinase; F26P2, fructose2,6-bisphosphate; TZD, thiazolidinedione; GyK, glycerol kinase; PEPCK, phosphoenolpyruvate carboxykinase; ROS, reactive oxygen species; JNK, c-Jun N-terminal kinase; NF-␬B, nuclear factor ␬B; TNF␣, tumor necrosis factor ␣; IL-6, interleukin-6; FFA, free fatty acid(s); HFD, high fat diet; PBS, phosphate-buffered saline; KD, kinase-dead; Ctrl, control; RT, reverse transcription. Using PFKFB3/iPFK2-disrupted mice, the present study demonstrates that PFKFB3/iPFK2 is involved in the anti-diabetic effect of PPAR␥ activation, probably by increasing the ability of adipose tissue to store fat and by suppressing adipose tissue inflammatory response. Disruption of PFKFB3/iPFK2 blunts the anti-diabetic effect of PPAR␥ activation. Male PFKFB3ϩ/Ϫ mice and wild-type littermates, at the age of 5– 6 weeks, were fed an HFD for 12 weeks and treated with rosiglitazone (10 mg/kg/day) or vehicle (PBS) during the last 4 weeks of HFD feeding. The age-matched male PFKFB3ϩ/Ϫ mice and wild-type littermates were fed a low fat diet (LFD) and received no treatment.

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION