Peptides of general formula (I): R1—Wn—Xm-AA1-AA2-AA3-AA4-AA5-AA6-Yp—Zq—R2 their stereoisomers, mixtures thereof and/or their cosmetically or pharmaceutically acceptable salts, a preparation process, cosmetic or pharmaceutical compositions which contain them and their use in the treatment and/or care of conditions, disorders and/or diseases which improve or are prevented by PGC-1α modulation. R1—Wn—Xm-AA1-AA2-AA3-AA4-AA5-AA6-Yp—Zq—R2  (I)