Abstract
ObjectivesTreatment of diabetic subjects with cinnamon demonstrated an improvement in blood glucose concentrations and insulin sensitivity but the underlying mechanisms remained unclear. This work intends to elucidate the impact of cinnamon effects on the brain by using isolated astrocytes, and an obese and diabetic mouse model.MethodsCinnamon components (eugenol, cinnamaldehyde) were added to astrocytes and liver cells to measure insulin signaling and glycogen synthesis. Ob/ob mice were supplemented with extract from cinnamomum zeylanicum for 6 weeks and cortical brain activity, locomotion and energy expenditure were evaluated. Insulin action was determined in brain and liver tissues.ResultsTreatment of primary astrocytes with eugenol promoted glycogen synthesis, whereas the effect of cinnamaldehyde was attenuated. In terms of brain function in vivo, cinnamon extract improved insulin sensitivity and brain activity in ob/ob mice, and the insulin-stimulated locomotor activity was improved. In addition, fasting blood glucose levels and glucose tolerance were greatly improved in ob/ob mice due to cinnamon extracts, while insulin secretion was unaltered. This corresponded with lower triglyceride and increased liver glycogen content and improved insulin action in liver tissues. In vitro, Fao cells exposed to cinnamon exhibited no change in insulin action.ConclusionsTogether, cinnamon extract improved insulin action in the brain as well as brain activity and locomotion. This specific effect may represent an important central feature of cinnamon in improving insulin action in the brain, and mediates metabolic alterations in the periphery to decrease liver fat and improve glucose homeostasis.
Highlights
The pathogenesis of type 2 diabetes integrates obesity, insulin resistance, and insulin secretion failure
Cinnamaldehyde and eugenol were dissolved in dimethyl sulphoxide (DMSO), which equals a final concentration of 0.025% (v/v)
Altered responses on glycogen formation and insulin signaling by cinnamaldehyde and eugenol in cultured primary astrocytes
Summary
The pathogenesis of type 2 diabetes integrates obesity, insulin resistance, and insulin secretion failure. Traditional chinese medicinal plants have been screened and used as pharmacological active compounds for a long time to treat and prevent various chronic diseases, such as diabetes, atherosclerosis, cancer, aging, and other degenerative diseases [1,2,3,4]. In this regard it is worth to remind that one of the most popular diabetes medications, metformin, originates from the perennial herb Galega officinalis used in folk medicine to treat diabetes for hundreds of years [5]. Cinnamon extracts were shown to have antidiabetic effects as a number of cell studies demonstrated an insulin-like action. Cinnamon extract was described as beneficial in Alzheimer’s disease by reducing bamyloid oligomerization and cognitive decline [10,11], and cinnamon further prevented glutamate-induced neuronal death in cultured cerebellar granule cells [12]
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