The effects of high levels of glucose and insulin on type I collagen synthesis in mature human odontoblasts and pulp tissue in vitro.
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 (Tjäderhane et al., 1994; Hietala and Larmas, 1995; Tjäderhane, 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 microgram/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 may alter odontoblast function independently of insulin.
Välikangas
L
L
Institute of Dentistry, University of Oulu, PO Box 5281, FIN-90014, University of Oulu, Finland. liisa.valikangas@oulu.fi
Pekkala
E
E
Larmas
M
M
Risteli
J
J
Salo
T
T
Tjäderhane
L
L
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D024042:Collagen Type I / Q000096:biosynthesis / Q000187:drug effects*; D003470:Culture Media; D046508:Culture Techniques; D003782:Dental Pulp / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D015536:Down-Regulation; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D009804:Odontoblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010446:Peptide Fragments / Q000187:drug effects / Q000378:metabolism; D011347:Procollagen / Q000187:drug effects / Q000378:metabolism; D013223:Statistics as Topic
D024042:Collagen Type I; D003470:Culture Media; D007328:Insulin; D010446:Peptide Fragments; D011347:Procollagen; C047202:procollagen Type I N-terminal peptide; D005947:Glucose