NAD
+
and
NADH play key roles in cellular respiration.
Intracellular redox state defined by the NAD
+
/NADH
ratio (RX) reflects the cellular metabolic and
physiopathological status. By taking the advantage of
high/ultrahigh magnetic field strengths, we have
recently established a novel
in
vivo
31
P
MRS based NAD assay for noninvasive measurements of
intracellular NAD concentrations and redox state in
animal and human brains at 16.4 T, 9.4 T and 7 T,
respectively. To explore its potential for clinical
translation, in this study, we investigated the
feasibility of assessing the NAD metabolism and redox
state in human brain at a relatively lower field of 4 T
by incorporating
1
H-decoupling
technique with the
31
P
NAD assay. The use of
1
H-decoupling
significantly narrowed the linewidths of NAD and
-ATP
resonances, resulting in higher sensitivity and
better-resolved resonance signals as compare to the
1
H-coupled
spectrum. These improvements made it possible for
reliably quantifying cerebral RX and NAD concentrations,
which are consistent with previously reported results
obtained at 7 T in similar aged human subjects. In
summary, this work demonstrates the capability and
utility of the
1
H-decoupled
31
P
MRS-based NAD assay at lower field strength, which
indicates potential opportunities for studying NAD
metabolism and redox state in human brain at clinical
setting.