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Continuous subtherapeutic insulin counteracts hypothalamopituitary-gonadal alterations in diabetic rats
G E Bestetti1, U Junker, V Locatelli
1Division of Experimental Pathology, University of Berne, Switzerland.
Abstract:
In experimental animal models, gonadal axis lesions are probably responsible for reproductive disorders associated with diabetes mellitus. The pathogenesis of these disorders is not yet known, but it is assumed that insulin deficiency plays an important role. To check this hypothesis, we have investigated the hypothalamopituitary-gonadal axis of insulin-treated streptozocin-induced diabetic (STZ-D) rats and compared it with that of untreated diabetic and control animals. Insulin was delivered by subcutaneously implanted osmotic minipumps. Furthermore, to determine whether possible beneficial insulin effects are selectively limited to the gonadal axis or act generally, we also studied retinal microangiopathy. The hypothalamopituitary-gonadal axis of insulin-treated diabetic animals was almost unchanged. On the contrary, retinal microangiopathy was only slightly influenced by subtherapeutic insulin doses. In conclusion, continuous administration of insulin at subtherapeutic doses can successfully counteract most of the effects of diabetes on the gonadal axis. Thus, the gonadal-axis impairment in STZ-D animals appears to be related to the fall of plasma insulin below a critical level. Furthermore, the various organ systems may respond to different plasma insulin threshold levels.
Insights
Insulin deficiency causes reproductive disorders in diabetes. Continuous insulin treatment in diabetic rats normalized the gonadal axis, suggesting insulin
Area of Science:
- Endocrinology
- Reproductive Biology
- Diabetology
Background:
- Diabetes mellitus is linked to reproductive disorders, potentially due to gonadal axis dysfunction.
- The precise role of insulin deficiency in the pathogenesis of these reproductive issues remains unclear.
Purpose of the Study:
- To investigate the hypothalamopituitary-gonadal axis in insulin-treated streptozocin-induced diabetic (STZ-D) rats.
- To compare the effects of insulin treatment on the gonadal axis and retinal microangiopathy in STZ-D rats.
Main Methods:
- Induction of diabetes in rats using streptozocin.
- Continuous subcutaneous insulin delivery via osmotic minipumps.
- Assessment of the hypothalamopituitary-gonadal axis and retinal microangiopathy.
Main Results:
- Insulin treatment largely preserved the hypothalamopituitary-gonadal axis in STZ-D rats.
- Retinal microangiopathy showed only minor improvement with subtherapeutic insulin doses.
- Gonadal axis impairment in STZ-D rats correlated with plasma insulin levels falling below a critical threshold.
Conclusions:
- Continuous subtherapeutic insulin administration effectively mitigates diabetes-induced gonadal axis dysfunction.
- The gonadal axis impairment in STZ-D rats is primarily linked to critically low plasma insulin levels.
- Different organ systems may exhibit varying sensitivities to plasma insulin threshold levels.