  We obtain explicit realizations of holographic renormalization group (RG)
flows from M-theory, from E^{2,1} \times Spin(7) at UV to AdS_4 \times
\tilde{S^7} (squashed S^7) at IR, from E^{2,1} \times CY4 at UV to AdS_4 \times
Q^{1,1,1} at IR, and from E^{2,1} \times HK (hyperKahler) at UV to AdS_4 \times
N^{0,1,0} at IR. The dual type IIA string theory configurations correspond to
D2-D6 brane systems where D6 branes wrap supersymmetric four-cycles. We also
study the Penrose limits and obtain the pp-wave backgrounds for the above
configurations. Besides, we study some examples of non-supersymmetric and
supersymmetric flows in five-dimensional gauge theories.
