Hormones of energy homeostasis : linking weight loss and cognition in Parkinson's disease?

Abstract

Parkinson’s disease (PD) is the second most common neurodegenerative disease in man and is complicated by dementia in up to 83% of people with PD. The risk of dementia is increased in people with PD who lose weight. Stable body weight relies on maintaining a balance of energy intake and energy output; a process coordinated by a number of circulating hormones of energy homeostasis. There is evidence that some of these; ghrelin, insulin and leptin may have pro-cognitive and neuroprotective effects in animal models of PD. Ghrelin secretion may be disordered in PD as levels are lower than in healthy controls. It is not known whether hormones of energy homeostasis are disrupted in people with PD and cognitive impairment (PD-CI). We conducted a cross-sectional quasi-experimental pilot study of 16 people with PD-CI,19 people with PD and normal cognition and 20 healthy controls. Fasting and post-prandial acyl-ghrelin, total ghrelin, growth hormone, insulin-like growth factor-1, insulin and leptin levels were measured. Fasting values and area under the curve for each value was analysed using ANOVA and post-hoc testing using the least-significant difference test. Post-hoc testing demonstrated lower acyl-ghrelin in the PD-CI group (p=0.02). Moreover, there was a correlation between acyl-ghrelin and cognition across the cohort (p=0.01) and acyl ghrelin significantly predicted cognition in multiple linear regression, accounting for 15% of the variance. Insulin and leptin were not different between groups and did not predict cognition. Hunger and fullness were measured using visual analogue scales. Energy intake at lunch was also recorded. Groups were compared using ANOVA. There were no significant differences in hunger, fullness or energy intake between groups. The data show reduced acyl-ghrelin in PD-CI. Acyl-ghrelin is a potential biomarker for cognitive decline in PD and further longitudinal studies should be carried out to further investigate this.