DataSheet_1_CD73-dependent generation of extracellular adenosine by vascular endothelial cells modulates de novo lipogenesis in adipose tissue.pdf

Next to white and brown adipocytes present in white and brown adipose tissue (WAT, BAT), vascular endothelial cells, tissue-resident macrophages and other immune cells have important roles in maintaining adipose tissue homeostasis but also contribute to the etiology of obesity-associated chronic inflammatory metabolic diseases. In addition to hormonal signals such as insulin and norepinephrine, extracellular adenine nucleotides modulate lipid storage, fatty acid release and thermogenic responses in adipose tissues. The complex regulation of extracellular adenine nucleotides involves a network of ectoenzymes that convert ATP via ADP and AMP to adenosine. However, in WAT and BAT the processing of extracellular adenine nucleotides and its relevance for intercellular communications are still largely unknown. Based on our observations that in adipose tissues the adenosine-generating enzyme CD73 is mainly expressed by vascular endothelial cells, we studied glucose and lipid handling, energy expenditure and adaptive thermogenesis in mice lacking endothelial CD73 housed at different ambient temperatures. Under conditions of thermogenic activation, CD73 expressed by endothelial cells is dispensable for the expression of thermogenic genes as well as energy expenditure. Notably, thermoneutral housing leading to a state of low energy expenditure and lipid accumulation in adipose tissues resulted in enhanced glucose uptake into WAT of endothelial CD73-deficient mice. This effect was associated with elevated expression levels of de novo lipogenesis genes. Mechanistic studies provide evidence that extracellular adenosine is imported into adipocytes and converted to AMP by adenosine kinase. Subsequently, activation of the AMP kinase lowers the expression of de novo lipogenesis genes, most likely via inactivation of the transcription factor carbohydrate response element binding protein (ChREBP). In conclusion, this study demonstrates that endothelial-derived extracellular adenosine generated via the ectoenzyme CD73 is a paracrine factor shaping lipid metabolism in WAT.</p

Intravenous Iron Carboxymaltose as a Potential Therapeutic in Anemia of Inflammation

<div><p>Intravenous iron supplementation is an effective therapy in iron deficiency anemia (IDA), but controversial in anemia of inflammation (AI). Unbound iron can be used by bacteria and viruses for their replication and enhance the inflammatory response. Nowadays available high molecular weight iron complexes for intravenous iron substitution, such as ferric carboxymaltose, might be useful in AI, as these pharmaceuticals deliver low doses of free iron over a prolonged period of time. We tested the effects of intravenous iron carboxymaltose in murine AI: Wild-type mice were exposed to the heat-killed <i>Brucella abortus</i> (BA) model and treated with or without high molecular weight intravenous iron. 4h after BA injection followed by 2h after intravenous iron treatment, inflammatory cytokines were upregulated by BA, but not enhanced by iron treatment. In long term experiments, mice were fed a regular or an iron deficient diet and then treated with intravenous iron or saline 14 days after BA injection. Iron treatment in mice with BA-induced AI was effective 24h after iron administration. In contrast, mice with IDA (on iron deficiency diet) prior to BA-IA required 7d to recover from AI. In these experiments, inflammatory markers were not further induced in iron-treated compared to vehicle-treated BA-injected mice. These results demonstrate that intravenous iron supplementation effectively treated the murine BA-induced AI without further enhancement of the inflammatory response. Studies in humans have to reveal treatment options for AI in patients.</p></div

Hepatic mRNA levels of pSTAT3, MCP-1, SOD2 and activin B in the liver of WT mice after BA and intravenous iron injection.

<p><b>(A)</b> Phosphorylated STAT3 levels compared to α-tubulin in the liver of C57BL/6 mice 4h after intraperitoneal BA or PBS administration followed by intravenous iron or PBS treatment for an additional 2h. <b>(B)</b> Hepatic MCP-1 mRNA levels were determined in WT mice after intraperitoneal BA or PBS administration followed by intravenous iron or PBS injection for an additional 2h (n = 3, 2-way ANOVA P<0,0001; **P = 0.007: PBS/PBS vs BA/PBS; *P = 0.02: PBS/PBS vs BA/iron; **P = 0.007: PBS/iron vs BA/PBS); (*P = 0.02: PBS/iron vs BA/iron; **P = 0.008: BA/PBS vs BA/iron; not shown in the graph). <b>(C)</b> Hepatic SOD2 mRNA levels in WT mice 4h after intraperitoneal BA or PBS administration followed by intravenous iron or PBS treatment for an additional 2h (n = 3, 2-way ANOVA P = 0.0002; **P = 0.004: PBS/PBS vs BA/PBS; **P = 0.004: PBS/PBS vs BA/iron); (**P = 0.006: PBS/iron vs BA/PBS; **P = 0.007: PBS/iron vs BA/iron, not shown in graph). <b>(D)</b> Hepatic activin B mRNA levels in WT mice 4h after intraperitoneal BA or PBS administration followed by intravenous iron or PBS injection for an additional 2h (n = 3, 2-way ANOVA P<0,0001; **P = 0.009: PBS/PBS vs BA/PBS; ***P = 0.0002: PBS/PBS vs BA/iron); (**P = 0.009: PBS/iron vs BA/PBS; ***P = 0.0003: PBS/iron vs BA/iron, not shown in graph).</p

Hepcidin response to iron treatment depends on the diets.

<p>WT mice were challenged with or without intraperitoneal BA injection and 14d later treated with or without intravenous iron. <b>(A)</b> Hepatic hepcidin mRNA levels 24h after iron treatment in mice fed a regular iron diet (black bars) or an iron deficient diet (white bars) (iron deficient diet: n = 4, 2-way ANOVA P = 0.006; *P = 0.01: PBS/PBS vs BA/iron; ***P = 0.0002: BA/PBS vs BA/iron). <b>(B)</b> Hepcidin mRNA levels 7d after the iron treatment in mice as in (A) (iron deficient diet: n = 4, 2-way ANOVA P = 0.0007; *p = 0.02: PBS/PBS vs BA/PBS; **P = 0.001: BA/PBS vs BA/iron). <b>(C)</b> Liver iron content (LIC) was determined in C57BL/6 mice fed a regular or iron deficient diet. LIC 14d after BA and 24h after intravenous iron administration are shown (regular diet: n = 3–4, 2-way ANOVA P = 0.002; **P = 0.008: PBS/PBS vs BA/PBS, iron deficient diet: n = 4, 2-way ANOVA, P < 0.0001; **P = 0.005: PBS/PBS vs BA/iron; **P = 0.004: BA/PBS vs BA/iron). <b>(D)</b> LIC 14d after BA and 7d after iron treatment in mice fed a regular or an iron deficient diet (iron deficient diet: n = 4, 2-way ANOVA P = 0.0002; *P = 0.01: PBS/PBS vs BA/iron; *P = 0.01: BA/PBS vs BA/iron).</p

Intravenous iron treated BA-induced anemia in mice.

<p>WT mice were challenged with intraperitoneal BA injection and 14d later treated with intravenous iron. <b>(A)</b> Hemoglobin levels 24h after the iron treatment in mice fed a regular (black bars) or iron deficient (white bars) diet (regular diet: n = 3, 2-way ANOVA P < 0,0001; ***P = 0.0006: PBS/PBS vs BA/PBS; *P = 0.02: BA/PBS vs BA/iron). <b>(B)</b> Hemoglobin levels 7d after the intravenous iron treatment as in (A) (iron deficient diet: n = 4, 2-way ANOVA P = 0.002; ***P = 0.0007: PBS/PBS vs BA/PBS; **P = 0.003: BA/PBS vs BA/iron). <b>(C)</b> Serum iron levels 24h after intravenous iron treatment in mice on a regular or iron deficient diet (iron deficient diet: n = 4, 2-way ANOVA P = 0.007; **P = 0.006: PBS/PBS vs BA/PBS; **P = 0.006: BA/PBS vs BA/iron). <b>(D)</b> Serum iron levels 7d after intravenous iron treatment as in (C).</p

Serum cytokine levels measured after BA and intravenous iron administration.

<p>(<b>A</b>) Serum IL-6 protein levels were determined in C57BL/6 mice 4h after intraperitoneal BA or PBS administration followed by intravenous iron or PBS injection for an additional 2h (n = 3, 2-way ANOVA P = 0.003; *P = 0.04: PBS/PBS vs BA/PBS; *P = 0.04: PBS/iron vs BA/PBS). <b>(B)</b> Serum TNF-α levels (n = 3, 2-way ANOVA P = 0.03; **P = 0.009: PBS/PBS vs BA/PBS; *P = 0.03: PBS/PBS vs BA/iron; **P = 0.009: PBS/iron vs BA/PBS; *P = 0.03: PBS/iron vs BA/iron).</p

Induction of hepatic hepcidin mRNA levels and serum iron levels after intraperitoneal injection of BA and/or intravenous iron carboxymaltose administration.

<p><b>(A)</b> Hepatic hepcidin mRNA levels were determined by quantitative RT-PCR in C57BL/6 mice 4h after intraperitoneal BA or PBS administration followed by intravenous iron or PBS treatment for an additional 2h (values represent mean±SD, n = 3, 2-way ANOVA, P = 0.002; **P = 0.004: PBS/PBS vs BA/PBS, and **P = 0.002: PBS/PBS vs BA/iron). <b>(B)</b> Serum iron levels were measured (values represent mean±SD, n = 3, 2-way ANOVA, P = 0.0008; *P = 0.02: PBS/PBS vs PBS/iron, *P = 0.01: PBS/PBS vs BA/PBS, *P = 0.04: PBS/PBS vs BA/iron, and *P = 0.03: BA/PBS vs BA/iron).</p

Reticulocyte production index (RPI) in BA-challenged mice fed a regular or an iron deficient diet and treated with intravenous iron or PBS.

<p>WT mice were fed a regular or iron deficient diet and injected with BA intraperitoneally followed 14d later by intravenous iron or PBS treatment. <b>(A)</b> Reticulocyte production Index (RPI = Retic%xHb/14.46, with 14.46g/dL as the mean baseline hemoglobin (Hb) level of healthy WT mice) 24h after iron or PBS treatment (2-way ANOVA P = 0.01, regular diet: n = 3, *P = 0.03: PBS/PBS vs BA/PBS; iron deficient diet: n = 3; *P = 0.02: PBS/PBS vs BA/iron). <b>(B)</b> Reticulocyte production 7d after iron or PBS treatment (iron deficient diet: n = 3–4, 2-way ANOVA P = 0.008; *P = 0.04: PBS/PBS vs BA/iron).</p