Franny Jongbloed

36 CHAPTER 2 The upregulation of pathways involved in stress resistance suggests that DR induces a protective state. In addition, we previously showed in young animals that this protection was associated with decreased levels of oxidative injury, cytokine production and inflammation and at six hours after IRI, levels of the pro-inflammatory cytokine interleukin 6 (IL-6) were significantly lower in DR compared to ad libitum fed mice 9,24 . These early effects support the concept that DR preconditions a protective stress response resulting in a better recovery rather than a faster recovery per se. In summary, we have shown that fasting induces a robust protection against renal IRI in aged-overweight F1-FVB/C57BL6-hybrid mice as it does in young-lean C57BL/6 mice. These findings suggest a general protective response induced by DR against IRI regardless of age, gender, body weight and genetic background. Gene expression profiles of kidneys of both young and aged mice after fasting show the involvement of retinol biosynthesis as well as stress response pathways. Whether these effects are cell-autonomous or influenced by systemic factors remains unknown and needs further clarification. Finally, contrary to common believe short-term preoperative DR rather than hyper alimentation improves stress resistance and recovery from surgically induced renal IRI. Therefore, translation of preoperative DR to the clinic seems to be the next logical step, whereby older and overweight patients do not have to be excluded from its benefits. MATERIALS AND METHODS Ethics statement All animal experiments are done according to the Dutch National Experiments on Animal Act via theEUadoptedDirective 86/609/EEC(1986) andhad the approval of the local Animal Experiments Committee of the National Institute of Public Health and the Environment (RIVM), the Netherlands (protocol number: 201100308). To ameliorate suffering of the animals, the mice were given 0.5 ml PBS supplemented with 2.4 µg buprenorphine after surgery in order to compensate for fluid loss and provide analgesia and an identical analgesic dose of buprenorphine was administered in the morning after surgery. The method of sacrifice was exsanguination, done under anesthesia by intramuscular injection of a Ketamine–Rompun mixture. Animals All aged mice were bred, raised and kept under identical SPF conditions as described 32 . Male (n=16) and female (n=22) wild type FVB-C57BL/6J F1-hybrid mice, with an average age of 72 and 74 weeks and average weight of 48.0 and 47.4 grams, respectively, were used. Animals were kept under standard laboratory conditions (temperature ± 20°C, 12-hour