AOX delays the onset of the lethal phenotype in a mouse model of Uqcrh (complex III) disease

Netrin 4 is a novel cytokine associated with oxidative stress and insulin resistance in obese individuals

BACKGROUND

Netrin 4 (NTN4) has been reported to be involved in a variety of pathophysiological processes, such as the occurrence and development of tumors, viral replication and infection, and diabetic retinopathy. However, the relationships between NTN4 and metabolic diseases have not been reported.

METHODS

The PhenoScanner tool and R language were used for bioinformatics analysis. Serum NTN4 was measured by ELISA in 211 healthy women and 193 overweight/obesity (OW/OB) women. Alterations in the serum NTN4 level were examined during the cold-exposure tests, acute exercise, lipid infusion, OGTT and EHC.

RESULTS

GWAS and Bioinformatics analysis revealed that NTN4 was closely related to energy metabolism and OS. In a population-based cohort study, we observed that individuals with OW/OB and IR exhibited significantly elevated levels of circulating NTN4. In addition, the serum NTN4 concentration was found to be significantly correlated with indicators of obesity, IR, sex hormone and glucose/lipid metabolism.

CONCLUSIONS

NTN4 is associated with obesity-related IR.

TRIAL REGISTRATION

All research plans were approved by the Human Research Ethics Committee of Chongqing Medical University (No. (74)2012, No. (72)2014 and No. (74)2015).

Xenotopic synthetic biology: Prospective tools for delaying aging and age-related diseases

Metabolic dysregulation represents one of the major driving forces in aging. Although multiple genetic and pharmacological manipulations are known to extend longevity in model organisms, aging is a complex trait, and targeting one's own genes may be insufficient to prevent age-dependent deterioration. An alternative strategy could be to use enzymes from other species to reverse age-associated metabolic changes. In this review, we discuss a set of enzymes from lower organisms that have been shown to affect various metabolic parameters linked to age-related processes. These enzymes include modulators of steady-state levels of amino acids (METase, ASNase, and ADI), NADPH/NADP+ and/or reduced form of coenzyme Q (CoQH2)/CoQ redox potentials (NDI1, AOX, LbNOX, TPNOX, EcSTH, RquA, LOXCAT, Grubraw, and ScURA), GSH (StGshF), mitochondrial membrane potential (mtON and mito-dR), or reactive oxygen species (DAAO and KillerRed-SOD1). We propose that leveraging non-mammalian enzymes represents an untapped resource that can be used to delay aging and age-related diseases.

The alternative enzymes-bearing tunicates lack multiple widely distributed genes coding for peripheral OXPHOS subunits

The respiratory chain alternative enzymes (AEs) NDX and AOX from the tunicate Ciona intestinalis (Ascidiacea) have been xenotopically expressed and characterized in human cells in culture and in the model organisms Drosophila melanogaster and mouse, with the purpose of developing bypass therapies to combat mitochondrial diseases in human patients with defective complexes I and III/IV, respectively. The fact that the genes coding for NDX and AOX have been lost from genomes of evolutionarily successful animal groups, such as vertebrates and insects, led us to investigate if the composition of the respiratory chain of Ciona and other tunicates differs significantly from that of humans and Drosophila, to accommodate the natural presence of AEs. We have failed to identify in tunicate genomes fifteen orthologous genes that code for subunits of the respiratory chain complexes; all of these putatively missing subunits are peripheral to complexes I, III and IV in mammals, and many are important for complex-complex interaction in supercomplexes (SCs), such as NDUFA11, UQCR11 and COX7A. Modeling of all respiratory chain subunit polypeptides of Ciona indicates significant structural divergence that is consistent with the lack of these fifteen clear orthologous subunits. We also provide evidence using Ciona AOX expressed in Drosophila that this AE cannot access the coenzyme Q pool reduced by complex I, but it is readily available to oxidize coenzyme Q molecules reduced by glycerophosphate oxidase, a mitochondrial inner membrane-bound dehydrogenase that is not involved in SCs. Altogether, our results suggest that Ciona AEs might have evolved in a mitochondrial inner membrane environment much different from that of mammals and insects, possibly without SCs; this correlates with the preferential functional interaction between these AEs and non-SC dehydrogenases in heterologous mammalian and insect systems. We discuss the implications of these findings for the applicability of Ciona AEs in human bypass therapies and for our understanding of the evolution of animal respiratory chain.