ß-carotene oxygenase 2 deficiency-triggered mitochondrial oxidative stress promotes low-grade inflammation and metabolic dysfunction.

Low-grade inflammation is a critical pathological factor contributing to the development of metabolic disorders. ß-carotene oxygenase 2 (BCO2) was initially identified as an enzyme catalyzing carotenoids in the inner mitochondrial membrane. Mutations in BCO2 are associated with inflammation and metabolic disorders in humans, yet the underlying mechanisms remain unknown. Here, we used loss-of-function approaches in mice and cell culture models to investigate the role of BCO2 in inflammation and metabolic dysfunction. We demonstrated decreases in BCO2 mRNA and protein levels and suppression of mitochondrial respiratory complex I proteins and mitochondrial superoxide dismutase levels in the liver of type 2 diabetic human subjects. Deficiency of BCO2 caused disruption of assembly of the mitochondrial respiratory supercomplexes, such as supercomplex III2+IV in mice, and overproduction of superoxide radicals in primary mouse embryonic fibroblasts. Further, deficiency of BCO2 increased protein carbonylation and populations of natural killer cells and M1 macrophages, and decreased populations of T cells, including CD4+ and/or CD8+ in the bone marrow and white adipose tissues. Elevation of plasma inflammatory cytokines and adipose tissue hypertrophy and inflammation were also characterized in BCO2 deficient mice. Moreover, BCO2 deficient mice were more susceptible to high-fat diet-induced obesity and hyperglycemia. Double knockout of BCO2 and leptin receptor genes caused a significantly greater elevation of the fasting blood glucose level in mice at 4 weeks of age, compared to the age- and sex-matched leptin receptor knockout. Finally, administration of Mito-TEMPO, a mitochondrial specific antioxidant attenuated systemic low-grade inflammation induced by BCO2 deficiency. Collectively, these findings suggest that BCO2 is essential for mitochondrial respiration and metabolic homeostasis in mammals. Loss or decreased expression of BCO2 leads to mitochondrial oxidative stress, low-grade inflammation, and the subsequent development of metabolic disorders.

Deficiency of ß-carotene oxygenase 2 induces mitochondrial fragmentation and activates the STING-IRF3 pathway in the mouse hypothalamus.

Hypothalamic inflammation has been linked to various aspects of central metabolic dysfunction and diseases in humans, including hyperphagia, altered energy expenditure, and obesity. We previously reported that loss of ß-carotene oxygenase 2 (BCO2), a mitochondrial inner membrane protein, causes the alteration of the hypothalamic metabolome, low-grade inflammation, and an increase in food intake in mice at an early age, e.g., 3-6 weeks. Here, we determined the extent to which the deficiency of BCO2 induces hypothalamic inflammation in BCO2 knockout mice. Mitochondrial proteomics, electron microscopy, and immunoblotting were used to assess the changes in hypothalamic mitochondrial dynamics and mitochondrial DNA sensing and signaling. The results showed that deficiency of BCO2 altered hypothalamic mitochondrial proteome and respiratory supercomplex assembly by enhancing the expression of NADH:ubiquinone oxidoreductase subunit A11 protein and improved cardiolipin synthesis. BCO2 deficiency potentiated mitochondrial fission but suppressed mitophagy and mitochondrial biogenesis. Furthermore, deficiency of BCO2 resulted in inactivation of mitochondrial MnSOD enzyme, excessive production of reactive oxygen species, and elevation of protein levels of stimulator of interferon genes (STING) and interferon regulatory factor 3 (IRF3) in the hypothalamus. The data suggest that BCO2 is essential for hypothalamic mitochondrial dynamics. BCO2 deficiency induces mitochondrial fragmentation and mitochondrial oxidative stress, which may lead to mitochondrial DNA release into the cytosol and subsequently sensing by activation of the STING-IRF3 signaling pathway in the mouse hypothalamus.

Pinto beans modulate the gut microbiome, augment MHC II protein, and antimicrobial peptide gene expression in mice fed a normal or western-style diet.

The onset of type 2 diabetes in obesity is associated with gut dysbiosis and a failure to confine commensal bacteria and toxins to the gut lumen while prebiotics may prevent these effects. This study evaluated the effects of pinto beans (PB) supplementation on cecal bacteria, short-chain fatty acids (SCFAs), distal ileal antigen presentation marker (major histocompatibility complex [MHC] II) and antimicrobial peptide genes during short-term high-fat, high sucrose (HFS) feeding. Six-week-old, male C57BL/6J mice were randomly assigned to four groups (n=12/group), and fed a control (C) or HFS diet with or without cooked PB (10%, wt/wt) for 30 days. Supplemental PB in both the C and HFS diets decreased the abundance of Tenericutes and the sulfate-reducing bacteria Bilophila. In contrast, PB raised the abundance of taxa within the SCFAs-producing family, Lachnospiraceae, compared to groups without PB. Consequently, fecal butyric acid was significantly higher in PB-supplemented groups compared to C and HFS groups. PB reversed the HFS-induced ablation of the distal ileal STAT3 phosphorylation, and up-regulated antimicrobial peptide genes (Reg3γ and Reg3ß). Furthermore, the expression of MHC II protein was elevated in the PB supplemented groups compared to C and HFS. Tenericutes and Bilophilia negatively correlated with activated STAT3 and MHC II proteins. Finally, supplemental PB improved fasting blood glucose, glucose tolerance and suppressed TNFα and inducible nitric oxide synthase mRNA in the visceral adipose tissue. Put together, the beneficial impact of PB supplementation on the gut may be central to its potential to protect against diet-induced inflammation and impaired glucose tolerance.

Involvement of PI3K/Akt, ERK and p38 signaling pathways in emodin-mediated extrinsic and intrinsic human hepatoblastoma cell apoptosis.

As a natural anthraquinone derivative, 1,3,8-trihydroxy-6-methylanthraquinone, known as emodin, has recently been reported to possess potential chemopreventive capacity, but the underlying molecular mechanism of its hepatocyte toxicity remains poorly clarified. The present research indicated that emodin targeted HepG2 cells without being cytotoxic to primary human hepatocyte cells in comparison with chrysophanol and rhein. The anti-proliferative effect of emodin was ascribed to occurrence of apoptosis, which characterized by higher ethidium bromide signal, brighter DAPI fluorescence, cleavages of procaspase-3 and poly (ADP-ribose) polymerase as well as quantitative result from Annexin V-FITC/PI double staining. Furthermore, emodin improved Bax/Bcl-2 ratio, elicited disruption of mitochondrial membrane potential and promoted efflux of cytochrome c to cytosol, indicative of features of mitochondria-dependent apoptotic signals. Emodin concurrently led to activations of Fas, Fas-L, caspase-8 and tBid, which provoked death receptor apoptotic signals. Notably, activated tBid relayed the Fas apoptotic signal to the mitochondrial pathway. Besides, emodin effectively attenuated phosphorylations of Akt and ERK and promoted phosphorylation of p38. Inhibitions of PI3K/Akt and ERK and activation of p38 mediated emodin-induced apoptosis through modulating the mitochondrial pathway and/or death receptor pathway. Additionally, there was a cross-talk between PI3K/Akt and MAPKs pathways in emodin-induced apoptosis.

A microfluidic platform to isolate avian erythrocytes infected with Plasmodium gallinaceum malaria parasites based on surface morphological changes.

This paper reports on a microfluidic platform to isolate and study avian red blood cells (RBCs) infected to various degrees by the malaria parasite Plasmodium gallinaceum. The experimental findings point to the feasibility of using the morphological changes on the surface of the malaria infected avian RBC (miaRBCs) as biomarkers for diagnosis. A glass substrate with a controlled surface roughness was used as part of a polydimethylsiloxane (PDMS) microfluidic channels. When whole-blood samples were introduced into the channels, the miaRBCs would be preferentially slowed and eventually become immobilized on the roughened surface. The surface lesions and furrow-like structures on the miaRBC surfaces offered a markedly higher probability to interact with the roughened substrate and allowed the cells to become imobilized on the surface. The captured miaRBCs were from blood samples at various degrees of infection at 3.2%, 3.9%, 9.1%, 13.4%, 20.1%, 28%, and 37%. It was observed that the miaRBCs could be selectively captured under a wall shear rate between 2.1 to 3.2 s(-1), which was directly proportional to the flow rate through the channels. This capture rate could be improved by increasing the channel length and finer flow control. It was also found that a roughened glass substrate with ten-point-height larger than the depth of surface lesions and furrow-like structures of miaRBCs showed a substantial enhancement on the number of immobilized infected RBCs. These findings indicated that surface morphologies, including surface lesions and furrow-like structures, can serve as an alternative biomarker for malaria diagnosis.