Interactions between lipid metabolism and the microbiome in aquatic organisms: A review.

Marine organisms' lipid metabolism contributes to marine ecosystems by producing a variety of lipid molecules. Historically, research focused on the lipid metabolism of the organisms themselves. Recent microbiome studies, however, have revealed that gut microbial communities influence the amount and type of lipids absorbed by organisms, thereby altering the organism's lipid metabolism. This has highlighted the growing importance of research on gut microbiota. This review highlights mechanisms by which gut microbiota facilitate lipid digestion and diversify the lipid pool in aquatic animals through the accelerated degradation of exogenous lipids and the transformation of lipid molecules. We also assess how environmental factors and pollutants, along with the innovative use of probiotics, interact with the gut microbiome to influence lipid metabolism within the host. We aim to elucidate the complex interactions between lipid metabolism and gut microbiota in aquatic animals by synthesizing current research and identifying knowledge gaps, providing a foundation for future explorations.

Effects of bisphenol A on reproduction, oxidative stress, and lipid regulation in the marine rotifer Brachionus plicatilis.

This study reports the effects of bisphenol A (BPA) on the rotifer Brachionus plicatilis, focusing on growth performance, reproductive output, oxidative stress responses, and lipid metabolism genes. High BPA levels disrupted peak daily offspring production and led to oxidative stress and increased superoxide dismutase and catalase activity. The research identified distinctive monoacylglycerol O-acyltransferase (MGAT) and diacylglycerol O-acyltransferase (DGAT) genes in B. plicatilis, B. rotundiformis, and B. koreanus, enhancing understanding of lipid metabolism in these species. BPA exposure significantly altered MGAT and DGAT expression, and feeding status affected these regulatory patterns. When food was unavailable, BPA reduced DGAT2 and MGAT2a expression. However, under feeding conditions, DGAT2 and MGAT1 levels increased, indicating that nutritional status and BPA exposure interact to affect gene expression.

Multigenerational resilience of the marine rotifer Brachionus plicatilis to high temperature after additive exposure to high salinity and nanoplastics.

To study multigenerational resilience to high temperature (HT) conditions, we exposed Brachionus plicatilis marine rotifers to HT, high salinity (HS), and nanoplastics (NPs), and measured reproductive and life-cycle endpoints. After exposure to HT, rotifer lifespans were reduced, but daily production of offspring increased. However, both combined HT/HS and HT/HS/NP exposure led to additional decreases in longevity and reproductive ability; the antioxidant defense mechanisms of the rotifers were also notably upregulated as measured by reactive oxygen species levels. Fatty-acid profiles were reduced in all conditions. In multigenerational experiments, the negative effects of HT dissipated rapidly; however, the effects of HT/HS and HT/HS/NPs required four generations to disappear completely. The findings indicated that B. plicatilis were able to recover from these environmental stressors. This study demonstrated the resilience of aquatic organisms in response to changing environmental conditions and provides insights into the complex interactions of different abiotic stressors.

Oxidative stress-mediated deleterious effects of hypoxia in the brackish water flea Diaphanosoma celebensis.

In this study, we investigated the acute toxicity, in vivo effects, oxidative stress, and gene expression changes caused by hypoxia on the brackish water flea Diaphanosoma celebensis. The no-observed-effect concentration (NOEC) of 48 h of hypoxia exposure was found to be 2 mg/L O2. Chronic exposure to NOEC caused a significant decline in lifespan but had no effect on total fecundity. The induction of reactive oxygen species increased in a time-dependent manner over 48 h, whereas the content of antioxidant enzymes (superoxide dismutase and catalase) decreased. The transcription and translation levels were modulated by hypoxia exposure. In particular, a significant increase in hemoglobin level was followed by up-regulation of hypoxia-inducible factor 1α gene expression and activation of the mitogen-activated protein kinase pathway. In conclusion, our findings provide a better understanding of the molecular mechanism of the adverse effects of hypoxia in brackish water zooplankton.

Toxicity and speciation of inorganic arsenics and their adverse effects on in vivo endpoints and oxidative stress in the marine medaka Oryzias melastigma.

Here, we investigate the effects of acute and chronic exposure to arsenate (AsV) and arsenite (AsIII) in the marine medaka Oryzias melastigma. In vivo effects, biotransformation, and oxidative stress were studied in marine medaka exposed to the two inorganic arsenics for 4 or 28 days. An investigation of embryonic development revealed no effect on in vivo parameters, but the hatching rate increased in the group exposed to AsIII. Exposure to AsIII also caused the greatest accumulation of arsenic in medaka. For acute exposure, the ratio of AsV to AsIII was higher than that of chronic exposure, indicating that bioaccumulation of inorganic arsenic can induce oxidative stress. The largest increase in oxidative stress was observed following acute exposure to AsIII, but no significant degree of oxidative stress was induced by chronic exposure. During acute exposure to AsV, the increase in the enzymatic activity of glutathione-S-transferase (GST) was twice as high compared with exposure to AsIII, suggesting that GST plays an important role in the initial detoxification process. In addition, an RNA-seq-based ingenuity pathway analysis revealed that acute exposure to AsIII may be related to cell-cycle progression. A network analysis using differentially expressed genes also revealed a potential link between the generation of inflammatory cytokines and oxidative stress due to arsenic exposure.

Three-Dimensional Image Visualization under Photon-Starved Conditions Using N Observations and Statistical Estimation.

In this paper, we propose a method for the three-dimensional (3D) image visualization of objects under photon-starved conditions using multiple observations and statistical estimation. To visualize 3D objects under these conditions, photon counting integral imaging was used, which can extract photons from 3D objects using the Poisson random process. However, this process may not reconstruct 3D images under severely photon-starved conditions due to a lack of photons. Therefore, to solve this problem, in this paper, we propose N-observation photon-counting integral imaging with statistical estimation. Since photons are extracted randomly using the Poisson distribution, increasing the samples of photons can improve the accuracy of photon extraction. In addition, by using a statistical estimation method, such as maximum likelihood estimation, 3D images can be reconstructed. To prove our proposed method, we implemented the optical experiment and calculated its performance metrics, which included the peak signal-to-noise ratio (PSNR), structural similarity (SSIM), peak-to-correlation energy (PCE), and the peak sidelobe ratio (PSR).

Image Processing Techniques for Improving Quality of 3D Profile in Digital Holographic Microscopy Using Deep Learning Algorithm.

Digital Holographic Microscopy (DHM) is a 3D imaging technology widely applied in biology, microelectronics, and medical research. However, the noise generated during the 3D imaging process can affect the accuracy of medical diagnoses. To solve this problem, we proposed several frequency domain filtering algorithms. However, the filtering algorithms we proposed have a limitation in that they can only be applied when the distance between the direct current (DC) spectrum and sidebands are sufficiently far. To address these limitations, among the proposed filtering algorithms, the HiVA algorithm and deep learning algorithm, which effectively filter by distinguishing between noise and detailed information of the object, are used to enable filtering regardless of the distance between the DC spectrum and sidebands. In this paper, a combination of deep learning technology and traditional image processing methods is proposed, aiming to reduce noise in 3D profile imaging using the Improved Denoising Diffusion Probabilistic Models (IDDPM) algorithm.

A Novel Image Processing Method for Obtaining an Accurate Three-Dimensional Profile of Red Blood Cells in Digital Holographic Microscopy.

Recently, research on disease diagnosis using red blood cells (RBCs) has been active due to the advantage that it is possible to diagnose many diseases with a drop of blood in a short time. Representatively, there are disease diagnosis technologies that utilize deep learning techniques and digital holographic microscope (DHM) techniques. However, three-dimensional (3D) profile obtained by DHM has a problem of random noise caused by the overlapping DC spectrum and sideband in the Fourier domain, which has the probability of misjudging diseases in deep learning technology. To reduce random noise and obtain a more accurate 3D profile, in this paper, we propose a novel image processing method which randomly selects the center of the high-frequency sideband (RaCoHS) in the Fourier domain. This proposed algorithm has the advantage of filtering while using only recorded hologram information to maintain high-frequency information. We compared and analyzed the conventional filtering method and the general image processing method to verify the effectiveness of the proposed method. In addition, the proposed image processing algorithm can be applied to all digital holography technologies including DHM, and in particular, it is expected to have a great effect on the accuracy of disease diagnosis technologies using DHM.

Three-Dimensional (3D) Visualization under Extremely Low Light Conditions Using Kalman Filter.

In recent years, research on three-dimensional (3D) reconstruction under low illumination environment has been reported. Photon-counting integral imaging is one of the techniques for visualizing 3D images under low light conditions. However, conventional photon-counting integral imaging has the problem that results are random because Poisson random numbers are temporally and spatially independent. Therefore, in this paper, we apply a technique called Kalman filter to photon-counting integral imaging, which corrects data groups with errors, to improve the visual quality of results. The purpose of this paper is to reduce randomness and improve the accuracy of visualization for results by incorporating the Kalman filter into 3D reconstruction images under extremely low light conditions. Since the proposed method has better structure similarity (SSIM), peak signal-to-noise ratio (PSNR) and cross-correlation values than the conventional method, it can be said that the visualization of low illuminated images can be accurate. In addition, the proposed method is expected to accelerate the development of autonomous driving technology and security camera technology.

3D photon counting integral imaging by using multi-level decomposition.

In this paper, we propose three-dimensional (3D) photon counting integral imaging by using multi-level decomposition such as discrete wavelet transform to improve the visual quality and measurement accuracy under photon-starved conditions. Conventional 3D integral imaging can visualize 3D objects and acquire their depth information. However, the amount of irradiated light on the object causes the degradation of visual quality for 3D images under photon-starved conditions. To visualize 3D objects, photon counting integral imaging has been utilized. It can detect photons from 3D scenes by using a computational photon counting model, which is modelled by the Poisson random process. However, photons occur not only from objects but also in areas where objects do not exist. Moreover, photon fluctuation may occur in the scene through shot noise. Since these noise photons are measurement errors, it may decrease the image quality and accuracy. In contrast, our proposed method uses 2D discrete wavelet transform, which can emphasize the object photons effectively. Finally, our proposed method can enhance the visual quality of 3D images and provide more accurate depth information under photon-starved conditions. To prove the feasibility of our proposed method, we implement the optical experiment and calculate various image quality metrics.

Effects of temperature and combinational exposures on lipid metabolism in aquatic invertebrates.

Studies of changes in fatty acids in response to environmental temperature changes have been conducted in many species, particularly mammals. However, few studies have considered aquatic invertebrates, even though they are particularly vulnerable to changes in environmental temperature. In this review, we summarize the process by which animals synthesize common fatty acids and point out differences between the fatty acid profiles of vertebrates and those of aquatic invertebrates. Unlike vertebrates, some aquatic invertebrates can directly synthesize polyunsaturated fatty acids (PUFAs), which can be used to respond to temperature changes. Various studies have shown that aquatic invertebrates increase the degree of saturation in their fatty acids through an increase in saturated fatty acid production or a decrease in PUFAs as the temperature increases. In addition, we summarize recent studies that have examined the complex effects of temperature and combinational stressors to determine whether the degree of saturation in aquatic invertebrates is influenced by other factors. The combined effects of carbon dioxide partial pressure, food quality, starvation, salinity, and chemical exposures have been confirmed, and fatty acid profile changes in response to high temperature were greater than those from combinational stressors.

Noise Filtering Method of Digital Holographic Microscopy for Obtaining an Accurate Three-Dimensional Profile of Object Using a Windowed Sideband Array (WiSA).

In the image processing method of digital holographic microscopy (DHM), we can obtain a phase information of an object by windowing a sideband in Fourier domain and taking inverse Fourier transform. In this method, it is necessary to window a wide sideband to obtain detailed information on the object. However, since the information of the DC spectrum is widely distributed over the entire range from the center of Fourier domain, the window sideband includes not only phase information but also DC information. For this reason, research on acquiring only the phase information of an object without noise in digital holography is a challenging issue for many researchers. Therefore, in this paper, we propose the use of a windowed sideband array (WiSA) as an image processing method to obtain an accurate three-dimensional (3D) profile of an object without noise in DHM. The proposed method does not affect the neighbor pixels of the filtered pixel but removes noise while maintaining the detail of the object. Thus, a more accurate 3D profile can be obtained compared with the conventional filter. In this paper, we create an ideal comparison target i.e., microspheres for comparison, and verify the effect of the filter through additional experiments using red blood cells.

Genome-wide identification of fatty acid synthesis genes, fatty acid profiles, and life parameters in two freshwater water flea Daphnia magna strains.

The freshwater water flea Daphnia magna is a planktonic animal belonging to the Cladocera. To evaluate differences between two D. magna strains (KIT and NIES) in terms of life parameters and fatty acid profiles, we examined several endpoints. In the D. magna KIT strain, the numbers of total and cumulative offspring were lower at 23 °C and higher at 14 °C than in the D. magna NIES strain. However, at 14 °C, the D. magna KIT strain showed an increased lifespan. Although the n-3/n-6 polyunsaturated fatty acids (PUFA) ratio was always decreased at a low temperature, the PUFA ratio in the KIT strain had a higher value on day 3 than the NIES strain, which gave it higher adaptability to low temperature. In addition, we identified the elongation of very long chain fatty acids (elovl) and fatty acid desaturase (fad) genes, which are involved in fatty acid biosynthesis pathways, in the genomes of both D. magna KIT and NIES. The Elovl and Fad genes in both D. magna strains were highly conserved, including tandem duplicated Elovl 1/7 genes. This study provides new information about the molecular basis for the difference in temperature sensitivity between two strains of D. magna.

Muscle fiber type-dependence effect of exercise on genomic networks in aged mice models.

Skeletal muscles are made up of various muscle fiber type including slow and fast-twitch fibers. Because each muscle fiber has its own physiological characteristics, the effects of aging and exercise vary depending on the type of muscle fiber. We used bioinformatics screening techniques such as differentially expressed gene analysis, gene ontology analysis and gene set enrichment analysis, to try to understand the genetic differences between muscle fiber types. The experiment and gene expression profiling in this study used the soleus (SOL, slow-twitch muscle) and gastrocnemius (GAS, fast-twitch muscle). According to our findings, fatty acid metabolism is significantly up-regulated in SOL compared to GAS, whereas the glucose metabolism pathway is significantly down-regulated in SOL compared to GAS. Furthermore, apoptosis and myogenesis patterns differ between SOL and GAS. SOL did not show differences in apoptosis due to the aging effect, but apoptosis in GAS was significantly up-regulated with age. Apoptosis in GAS of old groups is significantly reduced after 4 weeks of aerobic exercise, but no such finding was found in SOL. In terms of myogenesis, exercise intervention up-regulated this process in GAS of old groups but not in SOL. Taken together, muscle fiber type significantly interacts with aging and exercise. Despite the importance of the interaction between these factors, large-scale gene expression data has rarely been studied. We hope to contribute to a better understanding of the relationship between muscle fiber type, aging and exercise at the molecular level.

Effects of Bacillus Subtilis-Fermented White Sword Bean Extract on Adipogenesis and Lipolysis of 3T3-L1 Adipocytes.

To investigate the adipogenesis and lipolysis effects of the Bacillus subtilis-fermented white sword bean extract (FWSBE) on 3T3-L1 adipocytes, we treated 3T3-L1 preadipocytes before and after differentiation with FWSBE and measured triglyceride, free glycerol, mRNA, and protein levels. First, FWSBE reduced the cell viability of 3T3-L1 pre-adipocytes under 1000 µg/mL conditions. Triglyceride accumulation in 3T3-L1 pre-adipocytes was suppressed, and free glycerol content in mature 3T3-L1 adipocytes was increased in the FWSBE treatment groups, indicating that FWSBE has anti-obesity effects. Further, FWSBE suppressed adipogenesis in 3T3-L1 pre-adipocytes by lowering the protein levels of C/EBPα, PPARγ, and FAS and increasing the level of pACC and pAMPK. Additionally, FWSBE promoted lipolysis in mature 3T3-L1 adipocytes by increasing the transcription levels of Ppara, Acox, and Lcad and the protein levels of pHSL and ATGL. Thus, we suggest that FWSBE can be a potential dietary supplement because of its anti-obesity properties.

iTRAQ-based proteomic profiling, pathway analyses, and apoptotic mechanism in the Antarctic copepod Tigriopus kingsejongensis in response to ultraviolet B radiation.

iTRAQ proteomic profiling was conducted to examine the proteomic responses of the Antarctic copepod Tigriopus kingsejongensis under ultraviolet B (UVB) exposure. Of the 5507 proteins identified, 3479 proteins were annotated and classified into 25 groups using clusters of orthologous genes analysis. After exposing the T. kingsejongensis to 12 kJ/m2 UVB radiation, 77 biological processes were modulated over different time periods (0, 6, 12, 24, and 48 h) compared with the control. A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that UVB exposure in T. kingsejongensis downregulated ribosome and glyoxylate and dicarboxylate metabolism at all time points. Furthermore, antioxidant and chaperone proteins were highly downregulated in response to UVB exposure, causing protein damage and activating apoptotic processes in the 48 h UVB exposure group. These proteomic changes show the mechanisms that underlie the detrimental effects of UVB on the cellular defense systems of the Antarctic copepod T. kingsejongensis.

A novel diagnostic method based on filter bank theory for fast and accurate detection of thermoacoustic instability.

This study proposes and analyzes a novel methodology that can effectively detect multi-mode combustion instability (CI) in a gas turbine combustor. The experiment is conducted in a model gas turbine combustor, and dynamic pressure (DP) and flame images are examined during the transition from stable to unstable flame, which is driven by changing fuel compositions. As a powerful technique for early detection of CI in multi-mode as well as in single mode, a new filter bank (FB) method based on spectral analysis of DP is proposed. Sequential processing using a triangular filter with Mel-scaling and a Hamming window is applied to increase the accuracy of the FB method, and the instability criterion is determined by calculating the magnitude of FB components. The performance of the FB method is compared with that of two conventional methods that are based on the root-mean-squared DP and temporal kurtosis. From the results, the FB method shows comparable performance in detection speed, sensitivity, and accuracy with other parameters. In addition, the FB components enable the analysis of various frequencies and multi-mode frequencies. Therefore, the FB method can be considered as an additional prognosis tool to determine the multi-mode CI in a monitoring system for gas turbine combustors.

Alleviation of tributyltin-induced toxicity by diet and microplastics in the marine rotifer Brachionus koreanus.

To determine the effects of tributyltin (TBT) upon multiple exposures of diet and microplastic in rotifer, in vivo life parameters were measured. In 10 µg/L TBT-exposed rotifer, the 1 and 0.5 x diet groups resulted in reproduction reduction. However, 10 x diet treatment showed no significant changes in the total fecundity, despite a decrease in daily reproduction. Besides, differences in the lifespan were observed in response to different diet regimens. TBT and/or MP-exposed parental rotifer (F0) showed a significant delay in the pre-reproductive day under 0.5 x diet regimen. In all dietary regimens, exposure to TBT and MP induced an increase in reactive oxygen species, but antioxidant activities were perturbed. To further verify the carryover effect of TBT toxicity, progeny rotifer (F1) obtained from 24 h TBT and/or MP-exposed F0 was used. Interestingly, the faster hatching rate was observed only in F1 obtained from 1 x diet regimen-exposed F0. However, in the 0.5 x diet, the total fecundity was reduced and the pattern of the daily reproduction was collapsed. Thus, the toxicity of TBT can be alleviated by MP and nutrition status, but TBT-induced toxicity and its carryover effect are inevitable.

Genome-wide identification and structural analysis of heat shock protein gene families in the marine rotifer Brachionus spp.: Potential application in molecular ecotoxicology.

Heat shock proteins (Hsp) are class of conserved and ubiquitous stress proteins present in all living organisms from primitive to higher level. Various studies have demonstrated multiple cellular functions of Hsp in living organisms as an important biomarker in response to abiotic and biotic stressors including temperature, salinity, pH, hypoxia, environmental pollutants, and pathogens. However, full understanding on the mechanism and pathway involved in the induction of Hsp still remains challenging, especially in aquatic invertebrates. In this study, the entire Hsp family and subfamily members in the marine rotifers Brachionus spp., one of the cosmopolitan ecotoxicological model organisms, have been genome-widely identified. In Brachionus spp. Hsp family was comprised of Hsp10, small hsp (sHsp), Hsp40, Hsp60, Hsp70/105, and Hsp90, with highest number of genes found within Hsp40 DnaJ homolog subfamily C members. Also, the differences in the orientation of the conserved motifs within Hsp family may have induced differences in transcriptional gene modulation in response to thermal stress in Brachionus koreanus. Overall, Hsp family-specific domains were highly conserved in all three Brachionus spp., relative to Homo sapiens and across other animal taxa and these findings will be helpful for future ecotoxicological studies focusing on Hsps.

Effects of low temperature on longevity and lipid metabolism in the marine rotifer Brachionus koreanus.

Low-temperature exposure prolongs lifespans and changes lipid metabolism but the relationship between longevity and lipids is largely unknown. Here, we examine the relationship between longevity and lipid metabolism at low temperatures (20 °C and 15 °C) compared with a 25 °C control. Life parameters, fatty acid composition, and transcriptome changes were analyzed in the monogonont rotifer Brachionus koreanus. In vivo life-parameter data indicate that lifespan and fecundity exhibit opposite correlations at low temperatures. The amount of total fatty acids decreased significantly at low temperatures but areas stained with Nile red increased at 15 °C compared with the control. From RNA-seq-based transcriptional analysis, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway-enrichment analysis were conducted. GO analysis shows that telomeres were positively regulated at low temperatures. KEGG pathway-enrichment results indicate that gene expression involved in lipid metabolism was activated with increased glycerol and/or choline synthesis at low temperatures. We suggest that reduced reproductive rates are associated with a decrease of lecithin, which is involved in the conversion of glycerol to triacylglycerol in response to low temperatures by lowering the temperature of body fluid.