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The Effects of High levels of Glucose and Insulin on Type I Collagen Synthesis in Mature Human Odontoblasts and Pulp Tissue in vitro

Institute of Dentistry, University of Oulu, PO Box 5281, FIN-90014 University of Oulu, Finland, liisa.valikangas{at}oulu.fi

E. Pekkala

Institute of Dentistry, University of Oulu, PO Box 5281, FIN-90014 University of Oulu, Finland

M. Larmas

Institute of Dentistry, University of Oulu, PO Box 5281, FIN-90014 University of Oulu, Finland, Oulu University Hospital, Oulu, Finland

J. Risteli

Oulu University Hospital, Oulu, Finland

T. Salo

Institute of Dentistry, University of Oulu, PO Box 5281, FIN-90014 University of Oulu, Finland, Oulu University Hospital, Oulu, Finland

L. Tjäderhane

Institute of Dentistry, University of Oulu, PO Box 5281, FIN-90014 University of Oulu, Finland, Oulu Municipal Health Centre, Oulu, Finland

High levels of dietary sucrose affect the metabolism of the pulp-dentin complex and enhance the caries process in dentin. The high-sucrose diet reduces dentin formation in young rats (Tjaderhane et al., 1994; Hietala and Larmas, 1995; Tjaderhane, 1996) and in pups of rat dams fed high-sucrose diet during lactation (Pekkala et al., 2000a). However, the mechanisms behind the effects are unknown. A direct effect of elevated blood glucose or an indirect effect via insulin has been suggested. We investigated the effects of high glucose and insulin on type I collagen synthesis in human odontoblasts and pulp tissue in vitro, using an organ culture method for functional post-mitotic odontoblasts. Odontoblasts and pulp tissue were cultured separately for 10 days in DMEM with 15% FBS containing additional glucose (G) (4.45 g/L) or insulin (I) (0.6 µg/mL) or both together (GI). We evaluated type I collagen synthesis with RIA, measuring the level of N-terminal propeptide of type I collagen (PINP) secreted into the culture media. PINP secretion decreased in odontoblasts and pulp tissue in G and GI groups when compared with the control and insulin samples (p = 0.001 in both groups in the pulp samples). Insulin alone did not affect PINP secretion distinctly. The results indicate that high levels of glucose, but not insulin, directly down-regulate the type I collagen synthesis in young, differentiated human odontoblasts and pulp tissue. Insulin does not affect the inhibitory effect of high sucrose. These in vitro findings indicate that the high-sucrose diet mav alter odontoblast function independently of insulin.

Key Words: Glucose • insulin • human • odontoblast • collagen.

Advances in Dental Research, Vol. 15, No. 1, 72-75 (2001)
DOI: 10.1177/08959374010150011801


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