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ABSTRACT: The nuclear receptor PPAR (peroxisome proliferator-activated receptor) has three subtypes named α, δ(β), and γ that may act as receptors for a range of compounds including antihyperglycaemic drugs, insulin sensitizers, and non-steroidal anti-inflammatory drugs (NSAIDs). Although profiling of the subtype selectivity of the compounds for PPAR is indispensable to elucidate their pharmacological action, the absence of an appropriate transactivation assay for PPARδ led us to develop a sensitive and reproducible method. We found that co-expression of PPARδ, retinoid X receptor (RXR) α, and coactivators such as CBP and SRC-1 enhanced basal and agonist-dependent activation of PPAR responsive element (PPRE)-driven transcription by PPARδ, rendering a PPRE-driven reporter assay reliable and sensitive. Utilizing this assay for PPARδ, we re-evaluated the subtype selectivity of a variety of anti-inflammatory drugs for human PPAR. The PPAR agonists tested included two leukotriene (LT) D4 antagonist, seven NSAIDs, and two anti-rheumatoid drugs. We found that a novel LTD4 antagonist, FK011 ([2-(((2-(4-tert-butyl-1,3-thiazol-2-yl)-1-benzofuran-5-yl)oxy)methyl)phenyl]acetic acid), showed marked agonistic activity for PPARγ. NSAIDs were classified into the following three groups: those showing no activity for all subtypes, those that were selective for PPARγ such as indomethacin and diclofenac, and those showing agonistic activity for the δ and γ subtypes such as ibuprofen. These results will be important to studies on the molecular mechanisms of pharmacological actions of LTD4 antagonists and NSAIDs.

The interrelationship of the minerals calcium (Ca2+), magnesium (Mg2+) and silicon (Si) in the sediments and in the body walls of four tropical sea cucumber species was explored by modeling the concentrations of these minerals. The elemental concentrations of Ca2+, Mg2+ and Si were measured in the body walls and in the ambient sediments occupied by the sea cucumbers Holothuria scabra, H. leucospilota, H. atra and Bohadschia marmorata. The results indicate that the concentrations of Ca2+ and Mg2+ in the body walls of the four sea cucumber species are significantly different from each other, indicating a varying degree of biomineralization across sea cucumber taxa. In contrast, only B. marmorata showed a significant difference in the concentration of Si when compared to the rest of the species tested. Further analysis using linear mixed models revealed that the Ca2+, Mg2+ and Si concentrations in the body walls of the tested sea cucumber species are associated with the sediment concentrations of the same elements. The relatively high concentrations of Ca2+ and Mg2+ in the sediments indicate that these minerals are sufficiently high in sea cucumbers to support their biomineralization. The relationship between the Mg/Ca ratio in the body walls of the sea cucumbers and minerals in the sediments revealed that Si was the only mineral that was not correlated with the Mg/Ca ratio. Predicting the relationship of the elements Ca2+, Mg2+ and Si between the sediments and the body walls of sea cucumbers may be complex due to the various factors that influence the metabolism and biomineralization in sea cucumbers.

In the tropical ecosystem, sea cucumbers are associated with seagrass meadows in various ways, often forming a network of ecological interactions. From this myriad of interactions, the trophic relationship between the seagrasses and sea cucumbers has received recent attention with the advent of analytical techniques. However, little is understood about the exact mechanism by which seagrasses are sustaining the sea cucumber populations in the food chain, considering the high number of refractory components in seagrasses and the lack of digestive enzymes among sea cucumbers. This manuscript aims to review existing concepts in ecology concerning the association between tropical seagrasses and sea cucumbers to provide directions for research and management of this vital resource. We searched literature from electronic databases and identified key concepts concerning sea cucumber and seagrass communities based on geographic distribution, nutrient compositions, seagrass decomposition process, and trophic enrichments in the food chain. A conceptual model was then developed detailing the factors influencing the association between the seagrass meadows and sea cucumbers. Despite the limited published information on the seagrass–sea cucumber association, a synthesis of the current understanding of this topic is provided to address the declining sea cucumber populations in the tropical seagrass meadows. We suggest that the successful restoration of sea cucumber fisheries requires a thorough understanding of the seagrass decomposition process, which is vital to the diet of sea cucumbers.

The diet of the Spinetail Devil Ray Mobula japanica Müller and Henle 1841 from Butuan Bay, Philippines was investigated from January to May 2016 using data on its stomach contents, and C and N stable isotope analyses, in order to contribute to the scarce information on the feeding biology of the threatened tropical populations of the Mobula species. Examination of 16 M. japanica stomachs revealed ingestion of the euphausiid Pseudeuphausia latifrons, sergestid shrimps Acetes intermedius and Lucifer spp. , copepods, and other rare prey items. The tropical krill P. latifrons was the most common, often the sole food, that increases body length of individuals towards the warmer months of April and May, which coincide with the peak season of M. japanica fisheries. Results from δ13C and δ15N stable isotope analysis are consistent with the assimilation of large zooplankton and micronektonic crustaceans. This study is the first report on the feeding of M. japanica in tropical waters and the identification of euphausiid P. latifrons as its dominant prey.