Katherine Gallagher

Bone Marrow Adipose Tissue Is an Endocrine Organ that Contributes to Increased Circulating Adiponectin during Caloric Restriction

The adipocyte-derived hormone adiponectin promotes metabolic and cardiovascular health. Circulating adiponectin increases in lean states such as caloric restriction (CR), but the reasons for this paradox remain unclear. Unlike white adipose tissue (WAT), bone marrow adipose tissue (MAT) increases during CR, and both MAT and serum adiponectin increase in many other clinical conditions. Thus, we investigated whether MAT contributes to circulating adiponectin. We find that adiponectin secretion is greater from MAT than WAT. Notably, specific inhibition of MAT formation in mice results in decreased circulating adiponectin during CR despite unaltered adiponectin expression in WAT. Inhibiting MAT formation also alters skeletal muscle adaptation to CR, suggesting that MAT exerts systemic effects. Finally, we reveal that both MAT and serum adiponectin increase during cancer therapy in humans. These observations identify MAT as an endocrine organ that contributes significantly to increased serum adiponectin during CR and perhaps in other adverse states.

Cytokine Induced Phenotypic and Epigenetic Signatures Are Key to Establishing Specific Macrophage Phenotypes

Macrophages (MΦ) play an essential role in innate immune responses and can either display a pro-inflammatory, classically activated phenotype (M1) or undergo an alternative activation program (M2) promoting immune regulation. M-CSF is used to differentiate monocytes into MΦ and IFN-γ or IL-4+IL-13 to further polarize these cells towards M1 or M2, respectively. Recently, differentiation using only GM-CSF or M-CSF has been described to induce a M1- or M2-like phenotype, respectively. In this study, we combined both approaches by differentiating human MΦ in GM-CSF or M-CSF followed by polarization with either IFN-γ or IL-4+IL-13. We describe the phenotypic differences between CD14hi CD163hi CD206int FOLR2-expressing M-CSF MΦ and CD14lo CD163lo CD206hi GM-CSF MΦ but show that both macrophage populations reacted similarly to further polarization with IFN-γ or IL-4+IL-13 with up- and down-regulation of common M1 and M2 marker genes. We also show that high expression of the mannose receptor (CD206), a marker of alternative activation, is a distinct feature of GM-CSF MΦ. Changes of the chromatin structure carried out by chromatin modification enzymes (CME) have been shown to regulate myeloid differentiation. We analyzed the expression patterns of CME during MΦ polarization and show that M1 up-regulate the histone methyltransferase MLL and demethylase KDM6B, while resting and M2 MΦ were characterized by DNA methyltransferases and histone deacetylases. We demonstrate that MLL regulates CXCL10 expression and that this effect could be abrogated using a MLL-Menin inhibitor. Taken together we describe the distinct phenotypic differences of GM-CSF or M-CSF MΦ and demonstrate that MΦ polarization is regulated by specific epigenetic mechanisms. In addition, we describe a novel role for MLL as marker for classical activation. Our findings provide new insights into MΦ polarization that could be helpful to distinguish MΦ activation states.

Epigenetic Changes in Bone Marrow Progenitor Cells Influence the Inflammatory Phenotype and Alter Wound Healing in Type 2 Diabetes

Classically activated (M1) macrophages are known to play a role in the development of chronic inflammation associated with impaired wound healing in type 2 diabetes (T2D); however, the mechanism responsible for the dominant proinflammatory (M1) macrophage phenotype in T2D wounds is unknown. Since epigenetic enzymes can direct macrophage phenotypes, we assessed the role of histone methylation in bone marrow (BM) stem/progenitor cells in the programming of macrophages toward a proinflammatory phenotype. We have found that a repressive histone methylation mark, H3K27me3, is decreased at the promoter of the IL-12 gene in BM progenitors and this epigenetic signature is passed down to wound macrophages in a murine model of glucose intolerance (diet-induced obese). These epigenetically “preprogrammed” macrophages result in poised macrophages in peripheral tissue and negatively impact wound repair. We found that in diabetic conditions the H3K27 demethylase Jmjd3 drives IL-12 production in macrophages and that IL-12 production can be modulated by inhibiting Jmjd3. Using human T2D tissue and murine models, we have identified a previously unrecognized mechanism by which macrophages are programmed toward a proinflammatory phenotype, establishing a pattern of unrestrained inflammation associated with nonhealing wounds. Hence, histone demethylase inhibitor–based therapy may represent a novel treatment option for diabetic wounds.

Midterm outcomes after treatment of type II endoleaks associated with aneurysm sac expansion

Purpose To examine the outcomes following interventions for type II endoleaks in patients with aneurysm sac expansion after endovascular aneurysm repair (EVAR). Methods A retrospective review was conducted of all patients who underwent treatment for type II endoleak from July 2001 to September 2010 in a single center. In this time period, 29 (4.7%) patients (22 men; mean age 78.6 years, range 54–87) were identified as having a type II endoleak and enlargement of the aneurysm sac, meeting the criterion for treatment. All patients had at least one attempted percutaneous intervention. Patients were followed both clinically and radiographically, with computed tomographic angiography every 3 to 12 months, over a follow-up period that ranged from 1 to 10 years (mean 3.5). Results Forty-eight interventions were performed on the 29 patients. Of these, 15 (56%) patients underwent multiple (2–4) procedures. Of the 11 endoleaks with an isolated inferior mesenteric artery identified as the source, initial success for transarterial embolization at 2 years was 72%, with 2 of the failures having successful secondary interventions. For the 18 endoleaks with a lumbar source, the success of the initial intervention was 17% at 2 years; repeated embolization attempts produced a 40% secondary success rate. Seven (24%) patients had continued endoleak despite multiple treatment attempts; 3 ultimately required elective aortic graft explantation. There were no ruptures or deaths during the study period. In a comparison of type II endoleak patients who had stable aneurysm sacs and those who had persistent sac expansion, the only significant differences in preoperative anatomical characteristics were a lower prevalence of mural thrombus (p=0.036) and longer right iliac arteries (p=0.012) in the group with sac expansion. Independent predictors of type II endoleak were mural thrombus (p<0.001), patent lumbar arteries (p=0.004), aneurysm length (p=0.011), and iliac artery length (p=0.004) Conclusion This study demonstrates that most patients require multiple reinterventions to treat type II endoleaks; specifically, lumbar artery embolization carries a low midterm success rate.

Endovascular management as first therapy for chronic total occlusion of the lower extremity arteries: comparison of balloon angioplasty, stenting, and directional atherectomy.

Purpose To evaluate the role of endovascular therapy in the management of infrainguinal arterial chronic total occlusions (CTOs). Methods Data on all patients with CTOs treated at a single center from 2004 to 2010 were extracted from a prospectively maintained database for retrospective analysis. Patient demographics, angiographic studies, noninvasive vascular test results, and clinical outcomes were evaluated. In this time frame, 481 patients (283 men; mean age 71.7±11.5 years, range 52–85) with claudication (n=177) or critical limb ischemia (CLI, n=304) were treated for 688 CTOs. Lesions were segregated according to location [SFA (n=193), popliteal (n=67), tibial (n=217), and multilevel (n=211)] and analyzed based on treatment mode (angioplasty, angioplasty with stenting, or atherectomy) and clinical indication. Primary patency, assisted primary patency, and secondary patency, as well as limb salvage rates for CLI patients, were calculated. Results At 2 years in claudicants with CTOs confined to the SFA, primary patency ranged from 44% to 58% and secondary patency to 92% depending on treatment type; there were no significant differences among the treatments. However, in CLI patients with SFA CTOs, atherectomy produced better outcomes at 2 years (p=0.002 for primary and p=0.012 for secondary patency) than angioplasty alone. The limb salvage rates ranged from 73% to 91% (no differences among treatment types). In diabetics, CTOs treated with angioplasty and stent had improved secondary patency rates over angioplasty alone. Conclusion The endovascular management of CTO results in reasonable primary patency; moreover, secondary patency at 2 years is excellent. Endovascular therapy should be the first-line option for many patients with peripheral artery disease, including those with CLI, claudicants with poor bypass conduit, or patients at high medical risk for surgery. The presence of CTOs does not appear to change these recommendations. Although multiple reinterventions may be required, endovascular therapies can be considered a primary therapy for many patients with CTO.

Artificial Sweeteners Stimulate Adipogenesis and Suppress Lipolysis Independently of Sweet Taste Receptors

Background: Sweet taste receptors are candidate nutrient sensors in adipose tissue. Results: Sweet taste receptor ligands stimulate adipogenesis and suppress lipolysis; however, these effects do not require T1R2 and T1R3 despite their expression in adipose tissue. Conclusion: Some artificial sweeteners regulate adipocyte differentiation and metabolism through a sweet taste receptor-independent mechanism. Significance: Absorbed artificial sweeteners may regulate aspects of adipose tissue biology. G protein-coupled receptors mediate responses to a myriad of ligands, some of which regulate adipocyte differentiation and metabolism. The sweet taste receptors T1R2 and T1R3 are G protein-coupled receptors that function as carbohydrate sensors in taste buds, gut, and pancreas. Here we report that sweet taste receptors T1R2 and T1R3 are expressed throughout adipogenesis and in adipose tissues. Treatment of mouse and human precursor cells with artificial sweeteners, saccharin and acesulfame potassium, enhanced adipogenesis. Saccharin treatment of 3T3-L1 cells and primary mesenchymal stem cells rapidly stimulated phosphorylation of Akt and downstream targets with functions in adipogenesis such as cAMP-response element-binding protein and FOXO1; however, increased expression of peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding protein α was not observed until relatively late in differentiation. Saccharin-stimulated Akt phosphorylation at Thr-308 occurred within 5 min, was phosphatidylinositol 3-kinase-dependent, and occurred in the presence of high concentrations of insulin and dexamethasone; phosphorylation of Ser-473 occurred more gradually. Surprisingly, neither saccharin-stimulated adipogenesis nor Thr-308 phosphorylation was dependent on expression of T1R2 and/or T1R3, although Ser-473 phosphorylation was impaired in T1R2/T1R3 double knock-out precursors. In mature adipocytes, artificial sweetener treatment suppressed lipolysis even in the presence of forskolin, and lipolytic responses were correlated with phosphorylation of hormone-sensitive lipase. Suppression of lipolysis by saccharin in adipocytes was also independent of T1R2 and T1R3. These results suggest that some artificial sweeteners have previously uncharacterized metabolic effects on adipocyte differentiation and metabolism and that effects of artificial sweeteners on adipose tissue biology may be largely independent of the classical sweet taste receptors, T1R2 and T1R3.

Inflammation as a Therapeutic Target for Diabetic Neuropathies

Diabetic neuropathies (DNs) are one of the most prevalent chronic complications of diabetes and a major cause of disability, high mortality, and poor quality of life. Given the complex anatomy of the peripheral nervous system and types of fiber dysfunction, DNs have a wide spectrum of clinical manifestations. The treatment of DNs continues to be challenging, likely due to the complex pathogenesis that involves an array of systemic and cellular imbalances in glucose and lipids metabolism. These lead to the activation of various biochemical pathways, including increased oxidative/nitrosative stress, activation of the polyol and protein kinase C pathways, activation of polyADP ribosylation, and activation of genes involved in neuronal damage, cyclooxygenase-2 activation, endothelial dysfunction, altered Na+/K+-ATPase pump function, impaired C-peptide-related signaling pathways, endoplasmic reticulum stress, and low-grade inflammation. This review summarizes current evidence regarding the role of low-grade inflammation as a potential therapeutic target for DNs.

Gender differences in outcomes of endovascular treatment of infrainguinal peripheral artery disease

Objective: Our goal was to assess the outcomes of females compared to males treated with endovascular lower extremity interventions in order to determine optimal therapy based on gender. Methods: We performed a retrospective review evaluating the outcomes of primary transluminal angioplasty (PTA) and PTA + stenting (PTA + S) for peripheral arterial disease (PAD). Patency rates and limb salvage were the primary end points. Results: A total of 1017 lesions were analyzed in 537 patients (229 male and 308 female) between 2004 and 2009. There were no differences between genders in lesion characteristics. Women were more likely to have interventions for critical limb ischemia (CLI). In CLI patients with superficial femoral artery (SFA) and tibial lesions, women had better patency rates (P < .005). Conclusions: Women have better patency rates compared with men following treatment of some CLI lesions. Interestingly, women are treated more frequently for CLI when compared to men. For some lesion types in women, PTA alone was equivalent to PTA + S. Our results suggest that outcomes may be optimized by tailoring interventions to gender.

Outcomes after late explantation of aortic endografts depend on indication for explantation.

BACKGROUND With the growing prevalence of endovascular repair for abdominal aortic aneurysm (AAA), the number of patients requiring graft explantation is increasing. Therefore, knowledge related to outcomes after explantation may lead to improvement in surgical options. In this study we compare our experience with explantation of aortic endografts, based on indication. METHODS The medical records of all aortic procedures performed at our center were queried during the period from 2002 to 2012. Relevant data from patients needing explantation of aortic endografts were analyzed using Fishers exact test, t-test, and Kaplan-Meier analysis. RESULTS Thirty-nine patients underwent aortic endograft explantation (64.1% men). Mean age was 71.9 years with a mean aneurysm size of 6.8 cm (range 3.5-10.7 cm). Hypertension (97.4%), hyperlipidemia (76.9%), and history of smoking (82%) were the most prevalent risk factors. Mean time to explant was 41.7 months (range 2.2-118.4 months). The primary explant indication was endoleak in 27 (69.2%) and infection in 12 (30.8%) patients. The endoleak group consisted of 13 type I, 8 type II, 1 type III, 4 endotension, 1 rupture, and 4 patients with multiple endoleaks. Seven patients were symptomatic, whereas 2 had ruptured aneurysms. Half of the patients in the infection group required supraceliac clamping for explantation. Operative blood loss (P = 0.08) and need for transfusion (P = 0.005) were significantly higher in the infection group. Thirty-day morbidity was 51.8% for the endoleak group and 83% for the infection group (P = 0.08). There were only 2 deaths in the cohort within 30 days, both in the infection group. Twenty-seven patients were alive at a mean follow-up of 1.9 years (range 0.1-8.4 years). CONCLUSIONS Endograft explantation is a challenging operation with high morbidity and mortality. Furthermore, patients with an infectious etiology have significantly worse outcomes than those requiring explantation for endoleaks.

Macrophage-Mediated Inflammation in Normal and Diabetic Wound Healing

The healing of cutaneous wounds is dependent on the progression through distinct, yet overlapping phases of wound healing, including hemostasis, inflammation, proliferation, and resolution/remodeling. The failure of these phases to occur in a timely, progressive fashion promotes pathologic wound healing. The macrophage (MΦ) has been demonstrated to play a critical role in the inflammatory phase of tissue repair, where its dynamic plasticity allows this cell to mediate both tissue-destructive and -reparative functions. The ability to understand and control both the initiation and the resolution of inflammation is critical for treating pathologic wound healing. There are now a host of studies demonstrating that metabolic and epigenetic regulation of gene transcription can influence MΦ plasticity in wounds. In this review, we highlight the molecular and epigenetic factors that influence MΦ polarization in both physiologic and pathologic wound healing, with particular attention to diabetic wounds.