Presented herein are compositions and uses thereof for: (i) increasing or regulating glucose concentration in a central nervous system of a subject, (ii) inhibiting or delaying cognitive decline in a subject, (iii) enhancing cognitive function in a subject, and/or (iv) treating a disease or condition associated with a decreased level of glucose in a central nervous system of a subject. In some embodiments, the compositions provided herein comprise L-serine, or a precursor, derivative or conjugate thereof.
