B2M and Sepsis: To estimate the mitochondrial mass, we determined the mitochondrial copy number by calculating the ratio between the expression of mitochondrial genes and the nuclear housekeeping gene B2M. In keeping with the elevated mitochondrial DNA damage ratio, mitochondrial DNA levels were reduced in sepsis-AKI compared to control subjects, denoting a decrease in mitochondrial mass (p < 0.05; Fig. 7f).