Journal Club: on Vitamin D and Parkinson's disease

Preface:  After a long hiatus during which I have been doing so much research on Crohn's disease that I haven't written a damn thing about neuroscience, I've decided that it's time to return.  I have officially submitted my graduate school applications, and now need to get myself back into regular science-writing mode.

This week's Movement Disorders Journal Club held some lively discussion on the roles that vitamin D might play in the balance deficits of Parkinson's disease patients.  This was based on data presented for a grant application, so the following will have little to do with Dr. P's actual pilot study.

Vitamin D deficiency appears to be prominent in elderly people who frequently experience falls (Bischoff-Ferrari et al 2004).  The mechanisms by which vitamin D is involved with balance, however, are largely unknown.  Dr. P's studies propose to look at how vitamin D levels correlate with falls and posturography in patients with Parkinson's disease (PD) because post-mortem immunolabeling studies have shown that vitamin D receptors are particularly dense in the substantia nigra pars compacta (SNpc)(Eyles et al 2005).

The SNpc is an area of primary pathology in PD; specifically, it is the beginning of the primary dopamine pathway that extends to the basal ganglia and motor cortex, which ultimately make commands of the muscles.  When this pathway is depleted, as in PD, the lack of dopamine signaling from SNpc cells has ramifications through several terminal brain regions which lead to the rigidity, tremor and poor balance that characterize the disease.

One of the important questions to ask, given the high vitamin D receptor density in the SNpc, is what role vitamin D might play in that region of the brain: Is there a central nervous system mechanism by which vitamin D is involved in alleviating behavioral deficits of PD, or is vitamin D helping patients with more general balance deficits through its effect on muscles?

Dr. P is proposing to address this question on both clinical and basic science levels.  Her clinical studies will address the attenuation of several behavioral and motor impairments as correlated with various vitamin D levels.  Her complementary basic science component proposes to speculate vitamin D's activity in the SNpc of a rodent model.  Naturally, this is super exciting to yours truly, so I have offered my services (as an MD, Dr. P needs a collaborative basic science lab in which to conduct the non-human animal component of her studies).  It stunned me, in fact, to learn how little has been studied regarding the role of vitamin D in the SNpc and nigrostriatal pathway, given the clear indication that its receptors are prevalent.

Although this will not begin for several more months, at least, there will be more to come as the publishable results unfurl.  In the meantime, expose yourself to the sunshine! -- you supposedly benefit more from 15min/day sun exposure than from dietary means (Hall et al 2009; Wolpowitz & Gilchrest 2006).  Fanatic Cook elaborates on this beautifully.