- Voluntary exercise prevents the obese and diabetic metabolic syndrome of the melanocortin-4 receptor knockout mouse. Haskell-Luevano, C., Schaub, J.W., Andreasen, A., Haskell, K.R., Moore, M.C., Koerper, L.M., Rouzaud, F., Baker, H.V., Millard, W.J., Walter, G., Litherland, S.A., Xiang, Z. FASEB J. (2009)