Hypothalamic and cortical neurons of normotensive and spontaneously hypertensive rats are differently affected by streptozotocin diabetes

Role of dietary and endogenous antioxidants in diabetes

Diabetes affects different people of all ages, race, and sex. This is a condition characterized by a state of chronic hyperglycaemia that leads to an increase of intracellular oxidative stress linked to the overproduction of free radicals. In the present review, we focus our attention on the molecular mechanisms leading to oxidative stress-mediates complications with particular regard to central nervous system (CNS). Furthermore, the present review reports the effects of different kind of antioxidants with enzymatic and nonenzymatic action that may significantly decrease the intracellular free radicals' overproduction and prevents the hyperglycaemia-mediated complications.

Central nervous system complications of diabetes mellitus--a perspective from the blood-brain barrier

A host of diabetes-related changes in the central nervous system (CNS) has been recognized. The underlying causes of these changes are multiple. An important contributor to the changes in the CNS is the blood-brain barrier (BBB). Diabetes is associated with changes in both the barrier and transport functions of the cerebral microvessels. Structural changes in cerebral microvessels may account for some of the observed changes. Additional mechanisms include alterations in hemodynamic variables such as arteriovenous shunting, changes in biophysical properties and biochemical compositions of the endothelial cells including changes in lipid fluidity and composition, and alterations of neurotransmitter activity in the cerebral microvessels, notably altered beta adrenergic neurotransmission. These observations indicate that the CNS is not immune against the microangiopathic complications commonly found in various tissues of diabetic animals.

Thyroid and pituitary secretory disorders in streptozotocin-diabetic rats are associated with severe structural changes of these glands

Streptozotocin diabetes in rats is associated with reduced function of the hypothalamo-pituitary-thyroid axis. The structure and hormone secretion of the thyroid and pituitary glands were studied in adult male rats 1 month after streptozotocin injection. The thyroid of diabetic rats was characterized by decreased follicle area and epithelial thickness. By electron microscopy, thyroid epithelial cells were characterized by flattened and almost empty rough endoplasmic reticulum cisternae, scanty exocytotic apical and endocytotic vesicles as well as degenerate mitochondria and rough endoplasmic reticulum. By immunohistochemistry, intracolloidal thyroglobulin and T3 as well as intraepithelial thyroglobulin were reduced. Electron microscopic and immunohistochemical analysis of pituitary glands showed that in diabetic rats thyrotrophs were mostly of type II, and the number of thyrotrophs (type I + type II) was greater than in controls. By radioimmunoassay (RIA), plasma T3, T4, and TSH levels were markedly reduced, and the TSH response to TRH was deficient in diabetic animals. The pituitary TSH concentration was increased, as expected from the morphological data. This study demonstrates severe structural changes in the thyroid and pituitary glands of diabetic rats which are accompanied by marked alterations of their secretory activity.

The changes in the hypothalamo-pituitary-gonadal axis of streptozotocin-treated male rats depend from age at diabetes onset

The influence of age at diabetes onset and of capillary microangiopathy on the severity and evolution of hypothalamo-pituitary-gonadal changes was studied morphologically and morphometrically in male rats 4 and 8 months after streptozotocin injection. At each time period we studied 2 groups of rats, one made diabetic before (age 1 month), the other after puberty (age 3 months), and compared them with corresponding controls. The size of hypothalamic axons, numerical density and size of pituitary gonadotrophs, size of testicular tubules, and basement membrane thickness of retinal capillaries were measured. Major differences were found at 8 months. Changes of pituitary glands (i.e. small and numerous gonadotrophs) and testes (i.e. small tubular size) were more important in pre- than in postpubertal diabetic rats. This was a consequence of the aggravating prepubertal diabetes between 4 and 8 months. On the contrary, these changes partially regressed in postpubertal diabetic animals. Pituitary and testicular changes were correlated. Other lesions, such as swollen axonal processes in the hypothalamus, increased thickness of seminiferous epithelium and of capillary basement membranes, though very evident in diabetics, were independent from age at induction. Neither microangiopathy nor glycemia were correlated with any other change which confirmed their secondary role in diabetic neuroendocrine disorders. Thus, two types of diabetic disorders of the hypothalamo-pituitary-gonadal axis could be distinguished: 1) those with irreversible effects on immature yet partially reversible effects on mature structures; and 2) those independent from age at induction.