The metabolite α-aminoadipic acid (2-AAA) has been identified as a predictor of diabetes and atherosclerosis in large human prospective studies. However, the mechanisms linking this metabolite to disease pathophysiology remain unknown.
DHTKD1
is a central gene in the 2-AAA pathway, and has been linked to variation in 2-AAA levels in humans and animals. However, little is known about the role of
DHTKD1
in cellular metabolism. We hypothesized that
DHTKD1
is an important regulator of mitochondrial energy metabolism, with potential involvement in cardiometablic disease.
Methods and Results:
We investigated the consequences of loss of
DHTKD1
function in a human HAP-1 cell line. Treatment with 2-AAA increased mitochondrial respiration in wild-type (WT) cells, but had no effect in
DHTKD1
knock-out (KO) cells.
DHTKD1
KO cells had significantly lower mitochondrial respiration (Mito Stress Test, Seahorse Analyzer), with no differences in glycolytic function, supporting an important role for
DHTKD1
in mitochondrial metabolism. Membrane potential and mitochondrial content were up-regulated in KO compared to WT cells, suggesting a potential compensatory mechanism. We investigated the mechanisms underlying impaired mitochondrial function, and found TOM40 and TIM23, the pivotal proteins required for the movement of proteins into mitochondria, were decreased in
DHTKD1
KO cells. Further,
DHTKD1
KO resulted in reduced expression of electron transport chain related proteins (NDUF88, SDHB, MTCO1, UQCRC2, ATP5A) in mitochondria, but increased expression in the cytosol, suggesting impaired ability to cross the mitochondrial membrane.
Conclusions:
Our data suggest that the absence of
DHTKD1
leads to less TOM40 and TIM23 expression, preventing key proteins in the electron transport chain from entering into mitochondria, resulting in impaired mitochondrial respiration. These findings highlight the vital role of
DHTKD1
in cellular metabolism, and establish DHTKD1-mediated mitochondrial dysfunction as a potential novel pathway in cardiometabolic disease. Elevated 2-AAA observed in individuals prior to onset of diabetes and atherosclerosis may be an early biomarker of dysfunction in this pathway.
Studies of the Electron Transport Chain of Extremely Halophilic Bacteria
