Mitochondrial response to the BCKDK-deficiency: Some clues to understand the positive dietary response in this form of autism

Abstract

Mutations on the mitochondrial-expressed Branched Chain α-Keto acid Dehydrogenase Kinase (BCKDK) gene have been recently associated with a novel dietary-treatable form of autism. But, being a mitochondrial metabolism disease, little is known about the impact on mitochondrial performance. Here, we analyze the mitochondrial response to the BCKDK-deficiency in patient's primary fibroblasts by measuring bioenergetics, ultra-structural and dynamic parameters. A two-fold increase in superoxide anion production, together with a reduction in ATP-linked respiration and intracellular ATP levels (down to 60%) detected in mutants fibroblasts point to a general bioenergetics depletion that could affect the mitochondrial dynamics and cell fate. Ultrastructure analysis of BCKDK-deficient fibroblasts shows an increased number of elongated mitochondria, apparently associated with changes in the mediator of inner mitochondria membrane fusion, GTPase OPA1 forms, and in the outer mitochondrial membrane, mitofusin 2/MFN2. Our data support a possible hyperfusion response of BCKDK-deficient mitochondria to stress. Cellular fate also seems to be affected as these fibroblasts show an altered proportion of the cells on G0/G1 and G2/M phases. Knockdown of BCKDK gene in control fibroblasts recapitulates most of these features. Same BCKDK-knockdown in a MSUD patient fibroblasts unmasks the direct involvement of the accelerated BCAAs catabolism in the mitochondrial dysfunction. All these data give us a clue to understand the positive dietary response to an overload of branched-chain amino acids. We hypothesize that a combination of the current therapeutic option with a protocol that considers the oxidative damage and energy expenditure, addressing the patients' individuality, might be useful for the physicians.

Altered Redox Homeostasis in Branched‐Chain Amino Acid Disorders, Organic Acidurias, and Homocystinuria

“…However, also in this case, the mitochondrial response to BCKDK deficiency seems to be the increase in O 2 − , alterations in the expression of MnSOD and GPX, and alterations in the bioenergetics' profile with reductions in ATP-linked respiration and intracellular levels. All these data support the hyperfusion response of BCKDK-deficient mitochondria to stress and the altered cell fate observed in patients' fibroblasts [ 54 ]. Apart from the canonical ROS-producing sites in mitochondrial electron transfer chain, several reports pointed towards the important role of mitochondrial 2-oxoacid dehydrogenase complexes (2-oxoglutarate dehydrogenase, pyruvate dehydrogenase, and BCKDH) that share the E3 dihydrolipoamide dehydrogenase, as major O 2 − /H 2 O 2 producers under conditions of maximum activities of substrate oxidation [ 55 , 56 ].…”

Microbiota and Neurological Disorders: A Gut Feeling

“…Cellular processes depend on the energy supplied by their mitochondria, and dysfunctional mitochondria can lead to an unsustainable cellular bioenergetics deficit that is detrimental to the cell's function and survival. 181 In brain cells, even a small energy deficit, which is a common occurrence during the aging process, can reduce synaptic neurotransmitter release and adversely affect synaptic function. 26 , 101 Maintaining a healthy gut microbiota state is necessary to support the metabolic activities of the brain, 59 , 162 and Mattson 157 and Bourassa et al 85 posit that some of the common pathologies leading to ILOD and other brain disorders may be amenable to therapeutic modification by diet and lifestyle changes.…”

Dataset reporting BCKDK interference in a BCAA-catabolism restricted environment

“…Medium containing viral particles (non-target control shRNA -SHC002- or either of the BCKDK shRNAs targeting different sequences of human BCKDK ) were removed 48 h after transfection. Infections of MSUD fibroblasts were performed as described in [1] . ShRNA clone information: clone TRC number: TRCN0000199200, TRCN000010196, and TRCN000010183; clone ID: NM_005881.1-828s1c1, NM_005881.x-850s1c1, and NM_005881.x-135s1c1.…”

“…GAPDH mRNA expression levels were used as an endogenous control. The data were analyzed using LyghtCycler®480 software (Roche Applied Sciences) correlating the initial template concentration with the cycle threshold (Ct) to obtain the relative quantity (RQ) of RNA, defined in detail in [1] .…”

“… This data article contains complementary figures to the research article “Mitochondrial response to the BCKDK-deficiency: some clues to understand the positive dietary response in this form of autism” [ 1 ]. Herein we present data relative to the effect of knocking down BCKDK gene on the real time oxygen consumption rate of fibroblasts obtained from a Maple Syrup Urine Disease (MSUD) patient.…”