Adoptive transfer of Pfkfb3-disrupted hematopoietic cells to wild-type mice exacerbates diet-induced hepatic steatosis and inflammation

Abstract

Background and objectives: Hepatic steatosis and inflammation are key characteristics of non-alcoholic fatty liver disease (NAFLD). However, whether and how hepatic steatosis and liver inflammation are differentially regulated remains to be elucidated. Considering that disruption of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (Pfkfb3/iPfk2) dissociates fat deposition and inflammation, the present study examined a role for Pfkfb3/iPfk2 in hematopoietic cells in regulating hepatic steatosis and inflammation in mice. Methods: Pfkfb3-disrupted (Pfkfb3+/−) mice and wild-type (WT) littermates were fed a high-fat diet (HFD) and examined for NAFLD phenotype. Also, bone marrow cells isolated from Pfkfb3+/− mice and WT mice were differentiated into macrophages for analysis of macrophage activation status and for bone marrow transplantation (BMT) to generate chimeric (WT/BMT- Pfkfb3+/−) mice in which Pfkfb3 was disrupted only in hematopoietic cells and control chimeric (WT/BMT-WT) mice. The latter were also fed an HFD and examined for NAFLD phenotype. In vitro, hepatocytes were co-cultured with bone marrow-derived macrophages and examined for hepatocyte fat deposition and proinflammatory responses. Results: After the feeding period, HFD-fed Pfkfb3+/− mice displayed increased severity of liver inflammation in the absence of hepatic steatosis compared with HFD-fed WT mice. When inflammatory activation was analyzed, Pfkfb3+/− macrophages revealed increased proinflammatory activation and decreased anti-proinflammatory activation. When NAFLD phenotype was analyzed in the chimeric mice, WT/BMT-Pfkfb3+/− mice displayed increases in the severity of HFD-induced hepatic steatosis and inflammation compared with WT/BMT-WT mice. At the cellular level, hepatocytes co-cultured with Pfkfb3+/− macrophages revealed increased fat deposition and proinflammatory responses compared with hepatocytes co-cultured with WT macrophages. Conclusions: Pfkfb3 disruption only in hematopoietic cells exacerbates HFD-induced hepatic steatosis and inflammation whereas the Pfkfb3/iPfk2 in nonhematopoietic cells appeared to be needed for HFD feeding to induce hepatic steatosis. As such, the Pfkfb3/iPfk2 plays a unique role in regulating NAFLD pathophysiology.

Keywords

• 6-Phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (Pfkfb3/iPfk2)
• Hematopoietic cells
• Hepatic steatosis
• Inflammation
• Macrophages