The in vitro effect of insulin on collagen synthesis in embryonic chick tibia

Tetracycline administration increases protein (presumably procollagen) synthesis and secretion in periodontal ligament fibroblasts of streptozotocin-induced diabetic rats

Streptozotocin-induced, insulin-deficient diabetic adult rats were daily administrated either minocycline or a chemically-modified non-antimicrobial tetracycline (CMT) by oral gavage for a 3-week time period; untreated diabetic and non-diabetic rats served as controls. On day 21, all rats received an intravenous injection of 3H-proline followed by perfusion fixation with an aldehyde mixture at 20 minutes and 4 hours after isotope injection. The upper and lower mandibles of these rats were dissected and processed for quantitative electron microscopic autoradiography to study 3H-proline utilization by fibroblasts in the periodontal ligament (PDL) of molars. In the non-diabetic controls, at 20 min after 3H-proline injection, radioprecursor was incorporated by the Golgi-RER system of PDL fibroblasts. At the 4-h time period, most of the label was present over the collagen fibers around these cells. In contrast, PDL fibroblasts in the untreated diabetic rats showed marked abnormalities ultrastructurally and minimal uptake (20 min) and secretion (4 h) of labeled proline. At both time periods, in both minocycline- and CMT-treated diabetic rats, fibroblasts were structurally more normal and the radioprecursor was localized in the fibroblasts and the PDL matrix in a pattern similar to that seen in the control rats. These results suggest that the diabetes-induced structural abnormalities and suppression of synthesis and secretion of protein (presumably collagen and its precursor) by PDL fibroblasts can be restored to near-normal by administration of a tetracycline and that this effect is mediated by a non-antimicrobial property of this family of antibiotics.

Suggestion of a deficient osteoblastic function in diabetes mellitus: the possible cause of osteopenia in diabetics

The mechanism underlying diabetic osteopenia is still unclear and may involve osteoblastic activity and/or the deficit of insulin's anabolic action. Bone gla protein (BGP) is synthesized by the osteoblast and its synthesis increases with 1,25(OH)2D3 and fluoride. Because 1,25(OH)2D3 also stimulates insulin secretion, sodium fluoride administration can be used to investigate deficient osteoblastic activity in diabetics, as reflected by BGP levels. BGP was determined before and after administering sodium fluoride at a dosage of 50 mg/day/15 days to three groups: 14 patients with insulin-dependent diabetes, 16 diabetics on oral antidiabetic treatment, and 25 controls, all of similar age, sex, and characteristics. Basal BGP values (mean +/- SD) were low in diabetics on insulin treatment (4.3 +/- 1.1 ng/ml) and in diabetics on oral antidiabetics (5.8 +/- 1.2 ng/ml) as compared with controls (6.5 +/- 0.7 ng/ml) (P less than 0.001 and less than 0.05, respectively). After giving fluoride, BGP values did not change in the two diabetic groups but did vary in controls (8.1 +/- 0.6 ng/ml, P less than 0.001). These results suggest that deficient osteoblast function could be responsible for osteopenia in diabetics.