Neuroadaptations in the striatal proteome of the rat following prolonged excessive sucrose intake

Obesity is a contemporary health problem of rapidly increasing prevalence. One possible cause of obesity is loss of control over consumption of highly palatable foodstuffs, perhaps mirroring the processes involved in drug addiction. Accordingly, the striatum may be a key neural substrate involved in both food and drug craving. We hypothesised here that prolonged exposure to 10% sucrose solution might cause neuroadaptations in the striatum that are analogous to those previously reported following prolonged exposure to alcohol or recreational drugs. Male Wistar rats were given constant access to 10% sucrose solution (in addition to normal lab chow and tap water) for 8 months and were compared with control rats receiving no sucrose access. Rats in the sucrose group typically drank more than 100 ml of sucrose solution per day and showed 13% greater body weight than controls at the end of the 8 months. Striatal dopamine (DA) concentrations were decreased in the sucrose group rats relative to controls. Differential expression of 18 proteins was identified in the striatum of the sucrose group rats relative to controls. Down regulated proteins included pyridoxal phosphate phosphatase, involved in DA synthesis, and glutathione transferase, involved in free radical scavenging. Up regulated proteins included prolactin (which is under negative regulation by DA) and adipose differentiation-related protein, involved in fat synthesis. We hypothesise that DA-related neuroadaptations in the striatum caused by prolonged sucrose intake may partly drive compulsive intake and seeking of high palatability foodstuffs, in a similar way to that observed with drug and alcohol addictions.