Profiling metabolic states with genetically encoded fluorescent biosensors for NADH

NADH and its oxidized form, NAD+, play central roles in energy metabolism and are ideal indicators of cellular metabolic states. In this review, we will introduce recent progress made in the developing of a series of genetically encoded NADH sensors, which offer the potential to fill the gap in currently used techniques of endogenous NAD(P)H fluorescence imaging. These sensors are bright, specific and organelles targetable, allowing real-time tracking and quantification of intracellular NADH levels in different subcellular compartments. The individual strengths and weaknesses of these sensors when applied to the study of metabolic states profiling will be also discussed.