MMP9 and Parkinson disease: We measured levels of active MMP-9 within a small set (n = 8) of serum samples taken from people diagnosed with diabetic nephropathy (four males, four females, 61 ± 7 years of age), Alzheimer’s disease (four males, four females, 60 ± 5 years of age) and Parkinson’s disease (four males, four females, 62 ± 3 years of age), and compared them to a subset (n = 8) of closely age-matched serum samples taken from the second group of ALS (five males, three females, 65 ± 8 years of age) and HC (four males, four females, 61 ± 6 years of age) samples.