Sailasuta, Napapon

Suicidality is increased in autism spectrum disorder (ASD), yet effective interventions are lacking. Developing biologically based approaches for preventing and treating suicidality in ASD hinges on the identification of biomarkers of suicidal ideation (SI). Here, we assessed magnetic resonance spectroscopy (MRS) markers of glutamatergic neurotransmission in ASD youth and young adults. Twenty-eight ASD participants (16–33 years) underwent 1H-MRS, and metabolites were quantified using LCModel. N-acetylaspartate (NAA), glutamate (Glu), and the NAA/Glu ratio from the left dorsolateral prefrontal cortex were compared between ASD SI+ (n = 13) and ASD SI− (n = 15) participants. We found that ASD SI+ participants had a higher NAA/Glu ratio compared ASD SI- participants. The NAA/Glu ratio also predicted SI and significantly discriminated between ASD SI+/SI− participants. All analyses including NAA and Glu alone were non-significant. Here, we provide preliminary evidence for the importance of NAA/Glu in ASD with SI, with implications for biomarker discovery. Further mechanistic research into risk and interventional approaches to address SI in ASD are needed.

PurposeTo use 13C magnetic resonance spectroscopy (MRS) and 31P MRS to develop a direct assay for regional [HCO3−] in the human brain and to define brain pH and physiological response of [HCO3−] to fasting.Materials and MethodsSeven healthy subjects underwent MRS examinations on a 1.5T MRI scanner. Subjects were well fed with repeated examinations performed after 4 and 12 hours of fasting. Proton noise decoupling 13C MRS were acquired using pulse and acquired acquisition while 31P MRS were acquired using a 2D chemical shift imaging method with relaxation time (TR) of 2 seconds.ResultsFasting brain bicarbonate concentrations (6.7 ± 2.5 mM for 12‐hour fasting, P = 0.002 and 8.3 ± 2.1 mM for 4‐hour fasting, P = 0.015) are significantly reduced compared to fed state (11.6 ± 1.3 mM). However, no significant difference in brain pH was observed, confirming the critical role of pCO2 in intracerebral pH homeostasis.ConclusionWe demonstrated that the intracellular HCO3− in human brain is readily modified by diet but appears to have no measurable effect on cerebral pH. Natural abundance 13C can provide useful information relevant to human brain pH homeostasis by providing information for HCO3−. J. Magn. Reson. Imaging 2014;39:398–401. © 2013 Wiley Periodicals, Inc.