Karen A. Harford
University College Dublin
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Proceedings of the Nutrition Society | 2011
Karen A. Harford; Clare M. Reynolds; Fiona C. McGillicuddy; Helen M. Roche
High-fat diet-induced obesity is associated with a chronic state of low-grade inflammation, which pre-disposes to insulin resistance (IR), which can subsequently lead to type 2 diabetes mellitus. Macrophages represent a heterogeneous population of cells that are instrumental in initiating the innate immune response. Recent studies have shown that macrophages are key mediators of obesity-induced IR, with a progressive infiltration of macrophages into obese adipose tissue. These adipose tissue macrophages are referred to as classically activated (M1) macrophages. They release cytokines such as IL-1β, IL-6 and TNFα creating a pro-inflammatory environment that blocks adipocyte insulin action, contributing to the development of IR and type 2 diabetes mellitus. In lean individuals macrophages are in an alternatively activated (M2) state. M2 macrophages are involved in wound healing and immunoregulation. Wound-healing macrophages play a major role in tissue repair and homoeostasis, while immunoregulatory macrophages produce IL-10, an anti-inflammatory cytokine, which may protect against inflammation. The functional role of T-cell accumulation has recently been characterised in adipose tissue. Cytotoxic T-cells are effector T-cells and have been implicated in macrophage differentiation, activation and migration. Infiltration of cytotoxic T-cells into obese adipose tissue is thought to precede macrophage accumulation. T-cell-derived cytokines such as interferon γ promote the recruitment and activation of M1 macrophages augmenting adipose tissue inflammation and IR. Manipulating adipose tissue macrophages/T-cell activity and accumulation in vivo through dietary fat modification may attenuate adipose tissue inflammation, representing a therapeutic target for ameliorating obesity-induced IR.
Diabetes | 2011
Fiona C. McGillicuddy; Karen A. Harford; Clare M. Reynolds; E. Oliver; Mandy Claessens; Kingston H. G. Mills; Helen M. Roche
OBJECTIVE High-fat diet (HFD)-induced adipose tissue inflammation is a critical feature of diet-induced insulin resistance (IR); however, the contribution of interleukin-1 receptor I (IL-1RI)-mediated signals to this phenotype has not been defined. We hypothesized that lack of IL-1RI may ameliorate HFD-induced IR by attenuating adipose tissue inflammation. RESEARCH DESIGN AND METHODS Glucose homeostasis was monitored in chow- and HFD-fed wild-type (WT) and IL-1RI−/− mice by glucose tolerance and insulin tolerance tests. Macrophage recruitment and cytokine signature of adipose tissue macrophages was evaluated. Insulin sensitivity and cytokine secretion from adipose explants was quantified. Cytokine secretion and adipocyte insulin sensitivity was measured in cocultures of WT or IL-1RI−/− macrophages with 3T3L1 adipocytes. Synergistic effects of IL-1β with tumor necrosis factor (TNF)-α on inflammation was monitored in WT and IL-1RI−/− bone-marrow macrophages and adipose explants. RESULTS Lean and obese IL-1RI−/− animals exhibited enhanced glucose homeostasis by glucose tolerance test and insulin tolerance test. M1/M2 macrophage number in adipose tissue was comparable between genotypes; however, TNF-α and IL-6 secretion was lower from IL-1RI−/− adipose tissue macrophages. IL-1RI−/− adipose exhibited enhanced insulin sensitivity, elevated pAKT, lower cytokine secretion, and attenuated induction of phosphorylated signal transducer and activator of transcription 3 and suppressor of cytokine signaling molecule 3 after HFD. Coculture of WT, but not IL-1RI−/− macrophages, with 3T3L1 adipocytes enhanced IL-6 and TNF-α secretion, reduced adiponectin secretion, and impaired adipocyte insulin sensitivity. TNF-α and IL-1β potently synergized to enhance inflammation in WT macrophages and adipose, an effect lost in the absence of IL-1RI. CONCLUSIONS Lack of IL-1RI protects against HFD-induced IR coincident with reduced local adipose tissue inflammation, despite equivalent immune cell recruitment.
Journal of Nutritional Biochemistry | 2012
E. Oliver; Fiona C. McGillicuddy; Karen A. Harford; Clare M. Reynolds; Catherine M. Phillips; Jane F. Ferguson; Helen M. Roche
OBJECTIVE Adipose tissue inflammation with immune cell recruitment plays a key role in obesity-induced insulin resistance (IR). Long-chain (LC) n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have anti-inflammatory potential; however, their individual effects on adipose IR are ill defined. We hypothesized that EPA and DHA may differentially affect macrophage-induced IR in adipocytes. METHODS J774.2 macrophages pretreated with EPA or DHA (50 μM for 5 days) were stimulated with lipopolysaccharide (LPS, 100 ng/ml for 30 min-48 h). Cytokine secretion profiles and activation status of macrophages were assessed by enzyme-linked immunosorbent assay and flow cytometry. Pretreated macrophages were seeded onto transwell inserts and placed over 3T3-L1 adipocytes for 24-72 h; effects on adipocyte-macrophage cytokine cross-talk and insulin-stimulated ³H-glucose transport into adipocytes were monitored. RESULTS DHA had more potent anti-inflammatory effects relative to EPA, with marked attenuation of LPS-induced nuclear factor (NF)κB activation and tumor necrosis factor (TNF)α secretion in macrophages. DHA specifically enhanced anti-inflammatory interleukin (IL)-10 secretion and reduced the expression of proinflammatory M1 (F4/80⁺/CD11⁺) macrophages. Co-culture of DHA-enriched macrophages with adipocytes attenuated IL-6 and TNFα secretion while enhancing IL-10 secretion. Conditioned media (CM) from DHA-enriched macrophages attenuated adipocyte NFκB activation. Adipocytes co-cultured with DHA-enriched macrophages maintained insulin sensitivity with enhanced insulin-stimulated ³H-glucose transport, GLUT4 translocation and preservation of insulin-receptor substrate-1 expression compared to co-culture with untreated macrophages. We confirmed that IL-10 expressed by DHA-enriched macrophages attenuates the CM-induced proinflammatory IR phenotype in adipocytes. CONCLUSIONS We demonstrate an attenuated proinflammatory phenotype of DHA-pretreated macrophages, which when co-cultured with adipocytes partially preserved insulin sensitivity.
Molecular Nutrition & Food Research | 2012
Clare M. Reynolds; Fiona C. McGillicuddy; Karen A. Harford; Orla M. Finucane; Kingston H. G. Mills; Helen M. Roche
SCOPE Inflammasome-mediated inflammation is a critical regulator of obesity-induced insulin resistance (IR). We hypothesized that saturated fatty acids (SFA) directly prime the NLRP3 inflammasome via TLR4 concurrent with IR. We focused on dendritic cells (DCs) (CD11c(+) CD11b(+) F4/80(-) ), which are recruited into obese adipose tissue following high-fat diet (HFD) challenge and are a key cell in inflammasome biology. METHODS AND RESULTS C57BL/6 mice were fed HFD for 16 weeks (45% kcal palm oil), glucose homeostasis was monitored by glucose and insulin tolerance tests. Stromal vascular fraction (SVF) cells were isolated from adipose and analyzed for CD11c(+) CD11b(+) F480(-) DC. Following coculture with bone marrow derived DC (BMDC) insulin-stimulated (3) H-glucose transport into adipocytes, IL-1β secretion and caspase-1 activation was monitored. BMDCs primed with LPS (100 ng/mL), linoleic acid (LA; 200 μM), or palmitic acid (PA; 200 μM) were used to monitor inflammasome activation. We demonstrated significant infiltration of DCs into adipose after HFD. HFD-derived DCs reduce adipocyte insulin sensitivity upon coculture co-incident with enhanced adipocyte caspase-1 activation/IL-1β secretion. HFD-derived DCs are skewed toward a pro-inflammatory phenotype with increased IL-1β secretion, IL-1R1, TLR4, and caspase-1 expression. Complementary in vitro experiments demonstrate that TLR4 is critical in propagating SFA-mediated inflammasome activation. CONCLUSION SFA represent metabolic triggers priming the inflammasome, promoting adipocyte inflammation/IR, suggesting direct effects of SFA on inflammasome activation via TLR4.
The FASEB Journal | 2012
Emma Börgeson; Fiona C. McGillicuddy; Karen A. Harford; Niamh Corrigan; Debra F. Higgins; Paola Maderna; Helen M. Roche; Catherine Godson
Aging and adiposity are associated with chronic low‐grade inflammation, which underlies the development of obesity‐associated complications, including type 2 diabetes mellitus (T2DM). The mechanisms underlying adipose inflammation may include macrophage infiltration and activation, which, in turn, affect insulin sensitivity of adipocytes. There is a growing appreciation that specific lipid mediators (including lipoxins, resolvins, and protectins) can promote the resolution of inflammation. Here, we investigated the effect of lipoxin A4 (LXA4), the predominant endogenously generated lipoxin, on adipose tissue inflammation. Using adipose tissue explants from perigonadal depots of aging female C57BL/6J mice (Animalia, Chordata, Mus musculus) as a model of age‐associated adipose inflammation, we report that LXA4 (1 nM) attenuates adipose inflammation, decreasing IL‐6 and increasing IL‐10 expression (P<0.05). The altered cytokine milieu correlated with increased GLUT‐4 and IRS‐1 expression, suggesting improved insulin sensitivity. Further investigations revealed the ability of LXA4 to rescue macrophage‐induced desensitization to insulin‐stimulated signaling and glucose uptake in cultured adipocytes, using vehicle‐stimulated cells as controls. This was associated with preservation of Akt activation and reduced secretion of proinflammatory cytokines, including TNF‐α. We therefore propose that LXA4 may represent a potentially useful and novel therapeutic strategy to subvert adipose inflammation and insulin resistance, key components of T2DM.—Börgeson, E., McGillicuddy, F. C., Harford, K. A., Corrigan, N., Higgins, D. F., Maderna, P., Roche, H. M., Godson C. Lipoxin A4 attenuates adipose inflammation. FASEB J. 26, 4287–4294 (2012). www.fasebj.org
PLOS ONE | 2014
Orla M. Finucane; Clare M. Reynolds; Fiona C. McGillicuddy; Karen A. Harford; Martine C. Morrison; John Baugh; Helen M. Roche
Macrophage infiltration is a critical determinant of high-fat diet induced adipose tissue inflammation and insulin resistance. The precise mechanisms underpinning the initiation of macrophage recruitment and activation are unclear. Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, displays chemokine-like properties. Circulating MIF levels are elevated during obesity however its role in high-fat diet induced adipose inflammation and insulin resistance remains elusive. Wildtype and MIF−/− C57Bl\6J mice were fed chow or high-fat diet. Body weight and food intake was assessed. Glucose homeostasis was monitored by glucose and insulin tolerance tests. Adipose tissue macrophage recruitment and adipose tissue insulin sensitivity was evaluated. Cytokine secretion from stromal vascular fraction, adipose explants and bone marrow macrophages was measured. Inflammatory signature and insulin sensitivity of 3T3-L1-adipocytes co-cultured with wildtype and MIF−/− macrophage was quantified. Hepatic triacylglyceride levels were assessed. MIF−/− exhibited reduced weight gain. Age and weight-matched obese MIF−/− mice exhibited improved glucose homeostasis coincident with reduced adipose tissue M1 macrophage infiltration. Obese MIF−/− stromal vascular fraction secreted less TNFα and greater IL-10 compared to wildtype. Activation of JNK was impaired in obese MIF−/−adipose, concomitant with pAKT expression. 3T3-L1-adipocytes cultured with MIF−/− macrophages had reduced pro-inflammatory cytokine secretion and improved insulin sensitivity, effects which were also attained with MIF inhibitor ISO-1. MIF−/− liver exhibited reduced hepatic triacyglyceride accumulation, enhanced pAKT expression and reduced NFκB activation. MIF deficiency partially protects from high-fat diet induced insulin resistance by attenuating macrophage infiltration, ameliorating adipose inflammation, which improved adipocyte insulin resistance ex vivo. MIF represents a potential therapeutic target for treatment of high-fat diet induced insulin resistance.
American Journal of Physiology-endocrinology and Metabolism | 2013
Fiona C. McGillicuddy; Clare M. Reynolds; Orla M. Finucane; Eilish Coleman; Karen A. Harford; Christine Grant; Domenico Sergi; Lynda M. Williams; Kingston H. G. Mills; Helen M. Roche
Emerging evidence has demonstrated that saturated fatty acids prime pro-IL-1β production and inflammasome-mediated IL-1β activation is critical in obesity-associated insulin resistance (IR). Nonetheless, IL-1 receptor I-deficient (IL-1RI−/−) mice develop mature-onset obesity despite consuming a low-fat diet (LFD). With this apparent contradiction, the present study evaluated whether IL-1RI−/− mice were protected against long-term (6 mo) high-fat diet (HFD)-induced IR. Male wild-type and IL-1RI−/− mice were fed LFD or HFD for 3 or 6 mo, and glucose and insulin tolerance tests were performed. Adipose insulin sensitivity, cytokine profiles, and adipocyte morphology were assessed. The adipogenic potential of stromal vascular fraction was determined. Hepatic lipid accumulation and insulin sensitivity were characterized. IL-1RI−/− mice developed glucose intolerance and IR after 6 mo HFD compared with 3 mo HFD, coincident with enhanced weight gain, hyperinsulinemia, and hyperleptinemia. The aggravated IR phenotype was associated with loss of adipose functionality, switch from adipocyte hyperplasia to hypertrophy and hepatosteatosis. Induction of adipogenic genes was reduced in IL-1RI−/− preadipocytes after 6 mo HFD compared with 3 mo HFD. Obese LFD-IL-1RI−/− mice exhibited preserved metabolic health. IL-1RI−/− mice develop glucose intolerance and IR after 6 mo HFD intervention. While mature-onset obesity is evident in LFD-IL-1RI−/− mice, the additional metabolic insult of HFD was required to drive adipose inflammation and systemic IR. These findings indicate an important interaction between dietary fat and IL-1, relevant to optimal metabolic health.
Scottish Section of The Nutrition Society, 7-8 April 2009. | 2009
Karen A. Harford; M. Claessens; E. Oliver; Clare M. Reynolds; Kingston H. G. Mills; Helen M. Roche
Macrophages are a heterogeneous population of cells that play a role in the innate immune response to infection. Recent studies have shown that macrophages are key cells in the development of obesity, wherein there is progressive infiltration of macrophages into the adipose tissue. These adipose tissue macrophages are referred to as classically-activated, or M1, macrophages. They release proinflammatory cytokines such as IL-1, IL-6 and TNFa creating an inflammatory response that can contribute to insulin resistance and type 2 diabetes mellitus. In lean individuals macrophages are in an M2-polarization, or alternatively-activated, state and are thought to protect against inflammation. The IL-1 receptor type 1 (IL-1R1) is responsible for transmitting the pro-inflammatory effects of IL-1. The aim of the present study was to determine the number of adipose tissue macrophages and their activation state using flow cytometry in wild type (WT) mice and in IL-1R1 / mice at certain time points over a period of 16 weeks. C57BL/6 WT and IL-1R1 / mice with a C57BL/6 background (six to eight mice per group) were fed a high-fat diet (45% energy from fat) for 16 weeks. At weeks 0, 6 and 16 epididymal adipose tissue (EAT) and visceral adipose tissue (VAT) samples were taken from the C57BL/6 WT and IL-1R1 / mice. Adipocytes and stromal vascular cells (SVC) were isolated from the adipose tissue by collagenase treatment. SVC were labelled with antibodies for macrophage markers F4/80, CD11B and CD11C and analysed by flow cytometry to determine the number of macrophages and activation status of the macrophages present. Triple-positive cells (F4/80 + CD11B + CD11C + ) are associated with the M1-polarization state, while double-positive cells (F4/80 + CD11B + CD11C ) indicate M2 macrophages. At week 0 there was a significantly larger population of F4/80 + CD11B + CD11C (M2) cells in the EAT and VAT of the IL-1R1 / group compared with the WT group (P<0.05) but no difference between groups in the number of F4/80 + CD11B + CD11C + (M1) cells. However, after 6 weeks on a high-fat diet there was a larger population of the more active F4/80 + CD11B + CD11C + (M1) cells in the EAT of the WT group compared with the IL-1R1 / group (P<0.05) while there was a reduced number of F4/80 + CD11B + CD11C (M2) cells in the IL-1R1 / group compared with week 0. After 16 weeks on a high-fat diet there was no significant difference in the number of F4/80 + CD11B + CD11C + (M1) cells between the two groups of mice. Interestingly by week 16 there was a higher population of F4/80 + CD11B + CD11C (M2) cells in the EAT and VAT of the WT group compared with the IL-1R1 / group (P<0.05). These results imply that impairing IL-1 signalling decreases the macrophages ability to switch from an M2-polarization state to the proinflammatory M1-polarization state. This outcome delays the infiltration of M1 macrophages into the adipose tissue, thereby lowering the pro-inflammatory response and attenuating the progression of insulin resistance. Further studies are continuing in order to determine the molecular mechanisms by which this process occurs.
Proceedings of the Nutrition Society | 2008
Karen A. Harford; M. Claessens; E. Oliver; Kingston H. G. Mills; Helen M. Roche
Macrophages are a heterogeneous population of cells that play a role in the innate immune response to infection. Recent studies have shown that macrophages are key cells in the development of obesity, wherein there is progressive infiltration of macrophages into the adipose tissue. These adipose tissue macrophages are referred to as classically-activated, or M1, macrophages. They release proinflammatory cytokines such as IL-1, IL-6 and TNFa, creating an inflammatory response that can contribute to insulin resistance and type 2 diabetes mellitus (T2DM). In lean individuals macrophages are in an M2-polarization or alternatively-activated state and are thought to protect against inflammation. The IL-1 receptor type 1 (IL-1R1) is responsible for transmitting the pro-inflammatory effects of IL-1. The aim of the present study was to determine the number of adipose tissue macrophages and their activation state using flow cytometry in control mice and in IL-1R1 /mice at certain time points over a period of 12 weeks. C57BL/6 control and IL-1R1 /mice were fed a high-fat diet (45% energy from fat) for 12 weeks. At week 6 epididymal adipose tissue samples were taken from control and IL-1R1 /mice. Adipocytes and stromal vascular cells (SVC) were isolated from the adipose tissue by collagenase treatment. SVC were labelled with antibodies for macrophage markers F4/80, CD11B and CD11C and analysed by flow cytometry to determine the number of macrophages and activation status of the macrophages present. Triple-positive cells (F4/80 CD11B CD11C) are associated with the M1-polarization state, while double-positive cells (F4/80 CD11B ) indicate M2 macrophages. Fasting glucose, insulin, triacylglycerol (TAG) and non-esterified fatty acid (NEFA) concentrations were measured at weeks 0 and 6. In the control group a larger population of the more active F4/80CD11BCD11C cells was present at week 6 compared with the IL-1R1 /group (P<0.05). After 6 weeks on a high fat diet TG and NEFA levels were significantly higher in both control and IL-1R1 /groups. Fasting glucose concentrations did not differ significantly over time in either control or IL-1R1 /groups. However, insulin concentrations in the control group at week 6 were significantly higher when compared with week 0 (P<0.05), pointing to insulin resistance. No significant differences in insulin levels in the IL-1R1 /mice were found. These results imply that impairing IL-1 signalling decreases the macrophages ability to switch from an M2-polarization state to the proinflammatory M1-polarization state. This outcome reduces the infiltration of M1 macrophages into the adipose tissue, thereby lowering the pro-inflammatory response and attenuating the progression of insulin resistance. Further studies are continuing in order to determine the molecular mechanisms by which this process occurs.
Archive | 2010
Clare M. Reynolds; Fiona C. McGillicuddy; Karen A. Harford; Khg Mills; Helen M. Roche