Figure 3. AMPK is activated by increased cAMP levels in aged mice. (A) Western blots showing the effct of AMPK in young and aged mice, with or without calorie restriction. (B) Western blots showing the effect of AMPK in young and aged mice, with or without db-cAMP treatment. (C) Western blots showing the effect of AMPK in HFD-fed mice treated with the indicated level of db-cAMP. (D) Hepatic AMP concentrations in mice treated with the indicated levels of db-cAMP or rolipram.