Researchers have discovered that a hormone produced in the stomach called ghrelin could be used to boost resistance to or even slow the development of Parkinson's disease.

Parkinson's disease is caused by a degeneration of dopamine neurons in an area of the midbrain known as the substantia nigra, which is responsible for dopamine production. Reduced production of dopamine in late-stage Parkinson's disease causes symptoms such as severe difficulty in walking, restricted movements, delays in moving, lack of appetite, difficulty eating, periods of remaining motionless (known as "freezing") and head and limb tremors.

Parkinson's disease can develop when the dopamine cells degenerate and die.  The researchers found that ghrelin is protective of the dopamine neurons. "We also found that, in addition to its influence on appetite, ghrelin is responsible for direct activation of the brain's dopamine cells," said study author Tamas Horvath. "Because this hormone originates from the stomach, it is circulating normally in the body, so it could easily be used to boost resistance to Parkinson's disease or it could be used to slow the development of the disease."

Image: 3D representaion of dopamine.

The researchers conducted the study in mice that received ghrelin supplementation and in mice that were deficient in ghrelin hormone and in the ghrelin receptor. When compared to controls, mice with impaired ghrelin action in the brain had more loss of dopamine. Horvath said the results could be easily translated to human use because the ghrelin system is preserved through various species.

Ghrelin was previously associated with the release of growth hormones, appetite, learning, memory, and with the reward circuitry of the brain that regulates food cravings. Recent human studies show that body mass index, stored fat and diabetes are linked to Parkinson's disease. Past research also shows that obesity is a risk factor for neurodegeneration in mice.

The research team will in future studies try to determine ghrelin levels in both healthy individuals and Parkinson's disease patients. They will also determine whether altered ghrelin levels might be a biomarker of Parkinson's disease development and vulnerability.
References:
1. Tamas Horvat, et al. Ghrelin Promotes and Protects Nigrostriatal Dopamine Function via a UCP2-Dependent Mitochondrial Mechanism. J. Neurosci., Nov 2009; 29: 14057 - 14065 ; doi:10.1523/JNEUROSCI.3890-09.2009.
2. Image by Sbrools.