Type 1 diabetes alters brain cannabinoid receptor expression and phosphorylation status in rats

One of the most common symptoms of diabetes is extreme hunger, but the brain mechanism underlying this hyperphagia is unknown. The endocannabinoid system has emerged as one of the main food intake regulators in the brain. However, the effects of type 1 diabetes on the endocannabinoid system are not completely known. Thus, the aim of the present work is to establish the possible alterations induced by type 1 diabetes on the brain endocannabinoid system in rats. Western blot and immunocytochemistry were used to measure CB1 and phosphorylated CB1 receptor expression in several prosencephalic regions in streptozotocin-induced type 1 diabetic rats. Serum leptin levels were measured by ELISA. CB1 receptor expression was increased in striatum and hypothalamus of diabetic animals, with no changes in other brain areas studied. CB1 receptor phosphorylation was also increased in the same brain areas. Type 1 diabetes induced significant weight loss, and serum leptin levels were severely decreased. These results reinforce the possible role of the CB1 receptor as a pharmacological target for the clinical management of appetite in diabetic patients.

Diabetes-induced biochemical changes in central and peripheral catecholaminergic systems

A great variety of alterations have been described in the nervous system of diabetic animals. They are named as diabetic neuropathy and affect the brain, spinal cord and peripheral nerves. In diabetic animals, plasma and tissue catecholamine levels have been reported to be increased, decreased or unchanged, and these disparities have been explained by differences in the tissues selected, severity or duration of diabetes. Dopamine, norepinephrine and epinephrine from different tissues were extracted by absorption onto alumina, and measured by high performance liquid chromatography with electrochemical detection. We found that diabetes alters catecholaminergic systems in a highly specific manner. The dopamine content is reduced in the dopaminergic nigrostriatal system only. Norepinephrine is differently altered in several areas of the sympathetic nervous system. It is increased in cardiac ventricles, and decreased in stellate ganglia and the blood serum. However, it is not altered in the central nervous system. Finally, epinephrine is only altered in the adrenal gland where it is increased, and in the serum where it is reduced. Our results suggest that diabetes reduces the activity of the nigrostriatal dopaminergic system. Changes found at the sympathoadrenal level could be explained by reduced norepinephrine and epinephrine synthesis, with increased storage due to a reduced release from synaptic vesicles.