Figure 5. The glucose-fatty acid (Randle) cycle in muscle. Oxidation of fatty acids (FFA) inhibits pyru vate dehydrogenase (PDH). Citrate inhibits phosphofructokinase (PFK). The rise in glucose-6-phosphate inhibits hexokinase. Additional abbreviations: UDP, uridine diphosphate; GLUT 4, Glucose transporter 4.