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Insulin administration enhances growth of the beta-cell mass in streptozotocin-treated newborn rats
J Movassat1, C Saulnier, B Portha
1Laboratory of Physiopathology of Nutrition, Université Paris, France.
Insights
Neonatal diabetes in rats induced by streptozotocin (STZ) shows spontaneous beta-cell regeneration. Insulin therapy from day 2 to 6 significantly enhances beta-cell recovery and neogenesis from precursor cells.
Area of Science:
- Endocrinology
- Developmental Biology
- Regenerative Medicine
Background:
- Streptozotocin (STZ) induces neonatal diabetes by damaging pancreatic beta-cells.
- Previous studies showed spontaneous beta-cell recovery after STZ in newborn rats.
- The mechanisms of beta-cell regeneration in neonatal diabetes require further elucidation.
Purpose of the Study:
- To investigate the effect of early insulin therapy on STZ-induced beta-cell damage and regeneration in newborn rats.
- To determine the contribution of beta-cell replication and neogenesis to regeneration.
- To identify the preferred pathway for insulin-favored beta-cell regeneration.
Main Methods:
- STZ administration on day 1 to induce diabetes in newborn rats.
- Insulin therapy administered from day 2 to 4 or day 2 to 6.
- Quantification of total beta-cell mass and assessment of beta-cell replication and neogenesis.
- Analysis of beta-cell regeneration mechanisms.
Main Results:
- STZ reduced beta-cell mass to 10% of normal by day 4, with 27% recovery by day 7.
- Short-term insulin therapy (days 2-4) did not affect initial STZ-induced damage.
- Long-term insulin therapy (days 2-6) increased beta-cell mass to 44% by day 7.
- Insulin therapy reduced the contribution of replication to total growth (32%) and enhanced neogenesis.
Conclusions:
- Beta-cell regeneration after STZ in newborn rats involves both replication and neogenesis.
- Early insulin therapy significantly promotes beta-cell regeneration, particularly through neogenesis from precursor/stem cells.
- Insulin therapy is a promising strategy to enhance recovery from neonatal diabetes.
Abstract:
We have previously reported that the damage caused by streptozotocin (STZ) administration to the beta-cells in newborn rats was followed by spontaneous recovery from neonatal diabetes. Our present data indicate that STZ administration on the day of birth (day 1) reduced the total beta-cell mass on day 4 to only 10% of the normal value and that after such damage, 27% of the corresponding normal beta-cell mass was spontaneously regained on day 7. During days 4-7, the contribution of the predicted beta-cell growth (due to the replication of preexisting differentiated beta-cells) to the total beta-cell growth represented only 56%. Therefore, recruitment of new beta-cells from a precursor pool indeed represents a significant mechanism for beta-cell regeneration after STZ during this period of life. Here, we report for the first time that 1) insulin therapy from days 2 to 4 did not significantly influence the occurrence of beta-cell damage after STZ administration (total beta-cell mass on day 4 was reduced to 12% of the normal value) and 2) insulin therapy from days 2 to 6 did improve the otherwise spontaneous beta-cell regeneration, since on day 7 total beta-cell mass was 44% of the corresponding normal beta-cell mass. During days 4-7, the contribution of the predicted beta-cell growth to the total beta-cell growth represented only 32% in the insulin-treated STZ group. Finally the insulin-favored regeneration of the beta-cells reflects both an increased replication from differentiated beta-cells and an increased neogenesis from precursor/stem cells, with this last pathway being preferentially activated.