Completion of the Porphyra umbilicalis genome and ongoing research on this species by many investigators suggest the need for wider appreciation of regional specialisation of the P. umbilicalis blade. Here we use light and electron microscopy to describe four distinct regions of the blade: rhizoid cells with abundant floridean starch, vegetative cells, differentiating neutral sporangia, and mature neutral spores. The holdfast, densely covered by microorganisms, presents an intriguing biomechanical structure: thousands of very thin, long rhizoid tips course through the thick, secreted polysaccharide to the substratum. Wild blades in culture have more microorganisms than when collected, including filamentous cyanobacteria.
Regulation of organismal homeostasis in response to nutrient availability is a vital physiological process that involves inter-organ communication. Understanding the mechanisms controlling systemic cross-talk for the maintenance of metabolic health is critical to counteract diet-induced obesity. Here, we show that cardiac-derived transforming growth factor beta 1 (TGF-β1) protects against weight gain and glucose intolerance in mice subjected to high-fat diet. Secretion of TGF-β1 by cardiomyocytes correlates with the bioavailability of this factor in circulation. TGF-β1 prevents adipose tissue inflammation independent of body mass and glucose metabolism phenotypes, indicating protection from adipocyte dysfunction-driven immune cell recruitment. TGF-β1 alters the gene expression programs in white adipocytes, favoring their fatty acid oxidation and consequently increasing their mitochondrial oxygen consumption rates. Ultimately, subcutaneous and visceral white adipose tissue from cadiac-specific TGF-β1 transgenic mice fail to undergo cellular hypertrophy, leading to reduced overall adiposity during high-fat feeding. Thus, TGF-β1 is a critical mediator of heart-fat communication for the regulation of systemic metabolism.
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