The present invention relates generally to nucleic acid molecules expressed at least in the hypothalamus, liver, mesenteric adipose tissue, or red gastrocnemius muscle conveniently identified using differential display techniques under differing physiological conditions. The nucleic acid molecules are associated with or act as markers for conditions of inter alia a healthy state, myopathy, obesity, anorexia, weight maintenance, diabetes, disorders associated with mitochondrial dysfunction, genetic disorders and/or metabolic energy levels. More particularly, the present invention is directed to a nucleic acid molecule and/or its expression product for use in therapeutic and diagnostic protocols for conditions such as inter alia a myopathy, obesity, anorexia, weight maintenance, diabetes, disorders associated with mitochondrial dysfunction, genetic disorders and/or metabolic energy levels. The subject nucleic acid molecule and expression product and their derivatives, homologs, analogs and mimetics are proposed to be useful, therefore, as therapeutic and diagnostic agents for inter alia a myopathy, obesity, anorexia, weight maintenance, diabetes, disorders associated with mitochondrial dysfunction, genetic disorders and/or metabolic energy levels or as targets for the design and/or identification of modulators of their activity and/or function.