Community-Level Responses to Iron Availability in Open Ocean Plankton Ecosystems

Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron availability on plankton communities, we explored the comprehensive bio-oceanographic and bio-omics data sets from Tara Oceans in the context of the iron products from two state-of-the-art global scale biogeochemical models. We obtained novel information about adaptation and acclimation toward iron in a range of phytoplankton, including picocyanobacteria and diatoms, and identified whole subcommunities covarying with iron. Many of the observed global patterns were recapitulated in the Marquesas archipelago, where frequent plankton blooms are believed to be caused by natural iron fertilization, although they are not captured in large-scale biogeochemical models. This work provides a proof of concept that integrative analyses, spanning from genes to ecosystems and viruses to zooplankton, can disentangle the complexity of plankton communities and can lead to more accurate formulations of resource bioavailability in biogeochemical models, thus improving our understanding of plankton resilience in a changing environment

Cardiovascular Revascularization Medicine

3204-2051

Abstract 469: Vitamin D Deficiency Potentiates Restenosis Following Coronary Angioplasty in Hypercholesterolemic Swine

Introduction: Vitamin D is a sectosteroid that functions through vitamin D receptor (VDR), a transcription factor, which regulates various downstream signaling pathways and controls the transcription of many targets genes. Vitamin D deficiency is associated increased risk of incident congestive heart failure, myocardial infarction, and cardiovascular disease mortality. However, most of the studies which identified an association between lower vitamin D intake or lower 25-hydroxyvitamin D and increased risk of cardiovascular disease are observational or cross-sectional studies. There has been no careful study evaluating the effect of vitamin D supplementation on coronary artery disease outcome following coronary intervention. Objective: The purpose of this study was to examine the effect of vitamin D deficiency and vitamin D supplementation on coronary artery restenosis following balloon angioplasty in hypercholesterolemic Yucatan microswine. Methods: Twelve female microswine were fed vitamin D-deficient or vitamin D-sufficient high cholesterol diet. At six months, animals underwent coronary angioplasty. Following coronary intervention swine in the vitamin D-sufficient high cholesterol diet group received supplementation of 1,000 IU or 3,000 IU of vitamin D3. Six months later, angiogram was performed followed by optical coherence tomography to monitor the development of intimal hyperplasia and restenosis. At the end of 12 months animals were euthanized, coronary arteries were harvested and morphological and histological studies were performed. Results: Findings from the optical coherence tomography and histomorphometric studies showed a significant decrease in neointimal hyperplasia, increase in in-segment lumen diameter, and decrease in the intima-media ratio in coronary arteries following balloon angioplasty in swine with vitamin D supplementation compared to the animals with vitamin D-deficient status. In the in-vitro studies, calcitriol inhibited proliferation of coronary artery smooth muscle cells. Conclusion: These data suggest that vitamin D deficiency increases intimal hyperplasia and restenosis following coronary balloon angioplasty in hypercholesterolemic swine. Since vitamin D inhibits smooth muscle cell proliferation, supplementation of non-secosteroidal VDR ligands prior to coronary intervention could help in preventing the neointimal formation and restenosis. </jats:p

Decreased expression of vitamin D receptors in neointimal lesions following coronary artery angioplasty in atherosclerotic swine.

Inflammatory cytokines, such as TNF-α, play a key role in the pathogenesis of occlusive vascular diseases. Activation of vitamin D receptors (VDR) elicits both growth-inhibitory and anti-inflammatory effects. Here, we investigated the expression of TNF-α and VDR in post-angioplasty coronary artery neointimal lesions of hypercholesterolemic swine and examined the effect of vitamin D deficiency on the development of coronary restenosis. We also examined the effect of calcitriol on cell proliferation and effect of TNF-α on VDR activity and expression in porcine coronary artery smooth muscle cells (PCASMCs) in-vitro.Expression of VDR and TNF-α and the effect of vitamin D deficiency in post-angioplasty coronary arteries were analyzed by immunohistochemistry and histomorphometry. Cell proliferation was examined by thymidine and BrdU incorporation assays in cultured PCASMCs. Effect of TNF-α-stimulation on the activity and expression of VDR was analyzed by luciferase assay, immunoblotting and immunocytochemistry. In-vivo, morphometric analysis of the tissues revealed typical lesions with significant neointimal proliferation. Histological evaluation showed expression of smooth muscle α-actin and significantly increased expression of TNF-α in neointimal lesions. Interestingly, there was significantly decreased expression of VDR in PCASMCs of neointimal region compared to normal media. Indeed, post-balloon angioplasty restenosis was significantly higher in vitamin D-deficient hypercholesterolemic swine compared to vitamin D-sufficient group. In-vitro, calcitriol inhibited both serum- and PDGF-BB-induced proliferation in PCASMCs and TNF-α-stimulation significantly decreased the expression and activity of VDR in PCASMCs.These data suggest that significant downregulation of VDR in proliferating smooth muscle cells in neointimal lesions could be due to atherogenic cytokines, including TNF-α. Vitamin D deficiency potentiates the development of coronary restenosis. Calcitriol has anti-proliferative properties in PCASMCs and these actions are mediated through VDR. This could be a potential mechanism for uncontrolled growth of neointimal cells in injured arteries leading to restenosis

Vitamin D Supplementation Reduces Intimal Hyperplasia and Restenosis following Coronary Intervention in Atherosclerotic Swine.

Vitamin D is a fat-soluble steroid hormone that activates vitamin D receptor to regulate multiple downstream signaling pathways and transcription of various target genes. There is an association between vitamin D deficiency and increased risk for cardiovascular disease. However, most of the studies are observational and associative in nature with limited data on clinical application. Thus, there is a need for more prospective randomized controlled studies to determine whether or not vitamin D supplementation provides cardiovascular protection. In this study, we examined the effects of the deficiency and supplementation of vitamin D on coronary restenosis following coronary intervention in atherosclerotic Yucatan microswine. Twelve Yucatan microswine were fed vitamin D-deficient (n = 4) or -sufficient (n = 8) high cholesterol diet for 6-months followed by coronary intervention. Post-intervention, swine in the vitamin D-sufficient high cholesterol diet group received daily oral supplementation of either 1,000 IU (n = 4) or 3,000 IU (n = 4) vitamin D3. Six months later, optical coherence tomography (OCT) was performed to monitor the development of intimal hyperplasia and restenosis. Animals were euthanized to isolate arteries for histomorphometric and immunohistochemical studies. Animals had graded levels of serum 25(OH)D; vitamin D-deficient (15.33 ± 1.45 ng/ml), vitamin D-sufficient + 1,000 IU oral vitamin D post-intervention (32.27 ± 1.20 ng/ml), and vitamin D-sufficient + 3,000 IU oral vitamin D post-intervention (51.00 ± 3.47 ng/ml). Findings from the OCT and histomorphometric studies showed a decrease in intimal hyperplasia and restenosis in vitamin D-supplemented compared to vitamin D-deficient swine. Vitamin D supplementation significantly decreased serum levels of TNF-α and IFN-γ, upregulated serum levels of IL-10, and had no effect on serum IL-6 levels. These findings suggest that vitamin D supplementation limits neointimal formation following coronary intervention in atherosclerotic swine and provide the support for vitamin D supplementation to protect against the development of coronary restenosis

Experimental and Molecular Pathology

1346-3529