- Abnormal ambient glucose levels inhibit proteoglycan core protein gene expression and reduce proteoglycan accumulation during chondrogenesis: possible mechanism for teratogenic effects of maternal diabetes. Leonard, C.M., Bergman, M., Frenz, D.A., Macreery, L.A., Newman, S.A. Proc. Natl. Acad. Sci. U.S.A. (1989)