Effects of dietary glucose and fructose upon cannabinoid CB1 receptor functionality in the rat brain: A pilot study

Aims

A high consumption of fructose leads not only to peripheral changes in insulin sensitivity and vascular function, but also to central changes in several brain regions. Given the role of the endogenous cannabinoid system in the control of energy intake, we undertook a pilot study to determine whether a high fructose diet produced changes in brain CB₁ receptor functionality.

Main methods

Male rats given access ad libitum to normal chow were given either water, glucose or fructose solutions to drink. CB₁ receptor functionality was measured autoradiographically as the increase in ³⁵S]GTPγS binding produced by the agonist CP55,940.

Key findings

Seven regions were investigated: the prefrontal cortex, caudate–putamen, hippocampal CA1–CA3, dentate gyrus, amygdala, and dorsomedial and ventromedial hypothalami. Two-way robust Wilcoxon analyses for each brain region indicated that the dietary treatment did not produce significant main effects upon agonist-stimulated ³⁵S]GTPγS binding in any of the regions, in contrast to a significant main effect upon both leptin and adiponectin levels in the blood. However, a MANCOVA of the data controlling for leptin and adiponectin as co-variables identified a significant effect of glucose and fructose treatment for five weeks upon the ³⁵S]GTPγS response in the ventromedial hypothalamus, a region of importance for regulation of appetite.

Significance

It is concluded from this pilot study that palatable solutions do not produce overt changes in brain CB₁ receptor functionality, although subtle changes in discrete brain regions may occur.