Overnutrition causes many metabolic diseases including type 2 diabetes. PFKFB3/iPFK2 is a master regulator of adipocyte and intestinal nutrient metabolism. Using PFKFB3/iPFK2+/– mice and adipocyte-specific PFKFB3 over-expression mice, the present study investigated the role of PFKFB3/iPFK2 in regulating diet-induced adiposity, inflammation in adipose tissue and intestine, and systemic insulin resistance. On a high-fat diet (HFD), PFKFB3+/– mice gained much less body weight than did wild-type littermates. However, HFD-induced systemic insulin resistance in PFKFB3+/– mice was more severe than in wild-type littermates. In contrast, adipocyte-specific PFKFB3 over-expression increased adiposity but suppressed overnutrition induced adipose tissue inflammatory response and improved insulin sensitivity. In addition to adipose tissue, PFKFB3/iPFK2 also played a role in intestine events. Compared to wild-type littermates, PFKFB3+/– mice displayed a significant increase in the expression of intestinal inflammatory markers on a HFD. In conclusion, PFKFB3 protects against overnutrition-induced adipose tissue and intestine inflammatory response and systemic insulin resistance in an adiposity-independent manner. Selective PFKFB3 activation may be viable for treating and/or preventing insulin resistance and type 2 diabetes.

Studies had shown that leucine supplementation increases insulin sensitivity and it has been studied that n-3 PUFA may have an anti-inflammatory effect in adipocytes. However, the extent to which dietary sources such as leucine and/or n-3 PUFA act through PFKFB3/iPFK2 to suppress adipocyte inflammatory response has not been studied; PFKFB3/iPFK2 is a regulator that links adipocyte metabolism and inflammatory responses. In this study, the involvement of PFKFB3/iPFK2 in the effects of insulin sensitizing and anti-inflammatory effect of leucine and/or n-3 PUFA are explored using cultured 3T3-L1 adipocytes including wild-type cells, PFKFB3-control cells (iPFK2-Ctrl) and PFKFB3-knockdown cells (iPFK2-KD). In iPFK2-Ctrl cells, leucine supplementation appears to have insulin-sensitizing effects through improving p-Akt/Akt insulin signaling, but have no effect on adiponectin expression, and appear to have limited anti-inflammatory effects. n-3 PUFA supplementation appears to have limited effects on both insulin sensitizing and anti-inflammatory effects in iPFK2-Ctrl. In contrast, n-3 PUFA exhibit pro-inflammatory expression in iPFK2-KD. The results of this study support the hypothesis that PFKFB3/iPFK2 is critically involved in insulin-sensitizing effects of leucine. This role of PFKFB3/iPFK2, however, appears to be independent of anti-inflammatory responses. Given this, it is likely that PFKFB3/iPFK2 only account, in part, for the beneficial effects of leucine. n-3 PUFA stimulate PFKFB3/iPFK2 activity in wild-type adipocytes. However, PUFA do not exhibit anti-inflammatory and insulin-sensitizing effects in controls. In contrast, n3-PUFA exhibit proinflammatory effects in iPFK2-KD cells. Taken together, PFKFB3/iPFK2 is involved, at least in part, in the effects of insulin sensitization of leucine and appears to protect adipocytes from inflammatory responses, which could be exacerbated by n-3 PUFA when PFKFB3/iPFK2 is disrupted.