Neurochemical changes in welders revealed by proton magnetic resonance spectroscopy.
BACKGROUND
Occupational and environmental exposure to manganese (Mn) is associated with various neurobehavioral and movement dysfunctions. However, few studies have systemically examined the neurochemical effects of Mn exposure.


OBJECTIVE
We examined typical changes in cerebral metabolite ratios in welders chronically exposed to Mn, compared with control individuals, using proton magnetic resonance spectroscopy (MRS), investigated whether an abnormality in brain metabolism is associated with neurobehavioral changes, and assessed possible implications of chronic Mn exposure.


METHODS
Thirty-five welders chronically exposed to Mn and 20 age-matched healthy subjects underwent single-voxel MRS at short echo time to assess the N-acetylaspartate (NAA), myoinositol (mI), total choline (tCho), and glutamine plus glutamate (Glx) levels, each of which was expressed as a ratio to total creatine (tCr). Neurobehavioral tests were also performed to define cognitive status.


RESULTS
NAA/tCr, Glx/tCr, and tCho/tCr ratios in the frontal gray matter (anterior cingulate cortex; ACC) and parietal white matter did not differ significantly between welders and control subjects. These metabolite ratios did not correlate significantly with blood Mn concentration or neurobehavioral parameters. However, mI levels in the ACC, but not in the parietal white matter, were significantly reduced in welders compared with control individuals (P<0.01). Furthermore, in the frontal lobe of the brain, the mI/tCr ratio was significantly correlated with verbal memory scores as well as blood Mn concentration (P<0.05).


CONCLUSIONS
The cognitive decline observed in welders exposed to Mn was associated with a decreased mI/tCr ratio in the ACC. The depletion of mI in welders may reflect possible glial cell swelling and/or detoxification processes associated with long-term exposure to Mn.
Chang
Yongmin
Y
Department of Molecular Medicine, Kyungpook National University College of Medicine, Kyungpook National University Hospital, Daegu, South Korea.
Woo
Seung-Tae
ST
Lee
Jae-Jun
JJ
Song
Hui-Jin
HJ
Lee
Hui Joong
HJ
Yoo
Don-Sik
DS
Kim
Suk Hwan
SH
Lee
Hun
H
Kwon
Young Joo
YJ
Ahn
Hyung Jin
HJ
Ahn
Joon-Ho
JH
Park
Sin-Jae
SJ
Weon
Young Cheol
YC
Chung
In-Sung
IS
Jeong
Kyoung Sook
KS
Kim
Yangho
Y
D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects*; D016022:Case-Control Studies; D002794:Choline / Q000378:metabolism; D004781:Environmental Exposure / Q000009:adverse effects*; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D007294:Inositol / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008345:Manganese / Q000097:blood / Q000494:pharmacology; D008875:Middle Aged; D009460:Neurologic Examination / Q000379:methods; D011522:Protons; D013057:Spectrum Analysis / Q000379:methods; D013223:Statistics as Topic; D011795:Surveys and Questionnaires; D014896:Welding
D011522:Protons; D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid; D008345:Manganese; D007294:Inositol; C000179:N-acetylaspartate; D002794:Choline