Variants of the .alpha. subunit of AMP-activated kinase (AMPK), nucleic acids encoding such variants, and methods for their use are provided. The AMPK variants include splice variants that have an additional exon in the AMPK mRNA, and thus have an additional 15 amino acid residues in the encoded polypeptide. The AMPK variants can, for example, have at least 75% identity to the amino acid sequence of SEQ ID NO:4, and can contain an amino acid sequence having at least 75% identity to the amino acid sequence of SEQ ID NO:2.