Adipose tissue invariant NKT cells protect against diet-induced obesity and metabolic disorder through regulatory cytokine production

Invariant natural killer T (iNKT) cells are evolutionarily conserved innate T cells that influence inflammatory responses. We have shown that iNKT cells, previously thought to be rare in humans, were highly enriched in human and murine adipose tissue, and that as adipose tissue expanded in obesity, iNKT cells were depleted, correlating with proinflammatory macrophage infiltration. iNKT cell numbers were restored in mice and humans after weight loss. Mice lacking iNKT cells had enhanced weight gain, larger adipocytes, fatty livers, and insulin resistance on a high-fat diet. Adoptive transfer of iNKT cells into obese mice or in vivo activation of iNKT cells via their lipid ligand, alpha-galactocylceramide, decreased body fat, triglyceride levels, leptin, and fatty liver and improved insulin sensitivity through anti-inflammatory cytokine production by adipose-derived iNKT cells. This finding highlights the potential of iNKT cell-targeted therapies, previously proven to be safe in humans, in the management of obesity and its consequences.

Glucagon-like peptide 1 analogue therapy directly modulates innate immune-mediated inflammation in individuals with type 2 diabetes mellitus

AIMS/HYPOTHESIS

Glucagon-like peptide 1 (GLP-1) is a gut hormone used in the treatment of type 2 diabetes mellitus. There is emerging evidence that GLP-1 has anti-inflammatory activity in humans, with murine studies suggesting an effect on macrophage polarisation. We hypothesised that GLP-1 analogue therapy in individuals with type 2 diabetes mellitus would affect the inflammatory macrophage molecule soluble CD163 (sCD163) and adipocytokine profile.

METHODS

We studied ten obese type 2 diabetes mellitus patients starting GLP-1 analogue therapy at a hospital-based diabetes service. We investigated levels of sCD163, TNF-α, IL-1β, IL-6, adiponectin and leptin by ELISA, before and after 8 weeks of GLP-1 analogue therapy.

RESULTS

GLP-1 analogue therapy reduced levels of the inflammatory macrophage activation molecule sCD163 (220 ng/ml vs 171 ng/ml, p < 0.001). This occurred independent of changes in body weight, fructosamine and HbA1c. GLP-1 analogue therapy was associated with a decrease in levels of the inflammatory cytokines TNF-α (264 vs 149 pg/ml, p < 0.05), IL-1β (2,919 vs 748 pg/ml, p < 0.05) and IL-6 (1,379 vs 461 pg/ml p < 0.05) and an increase in levels of the anti-inflammatory adipokine adiponectin (4,480 vs 6,290 pg/ml, p < 0.002).

CONCLUSIONS/INTERPRETATION

In individuals with type 2 diabetes mellitus, GLP-1 analogue therapy reduces the frequency of inflammatory macrophages. This effect is not dependent on the glycaemic or body weight effects of GLP-1.

Adipose Type One Innate Lymphoid Cells Regulate Macrophage Homeostasis through Targeted Cytotoxicity

Adipose tissue has a dynamic immune system that adapts to changes in diet and maintains homeostatic tissue remodeling. Adipose type 1 innate lymphoid cells (AT1-ILCs) promote pro-inflammatory macrophages in obesity, but little is known about their functions at steady state. Here we found that human and murine adipose tissue harbor heterogeneous populations of AT1-ILCs. Experiments using parabiotic mice fed a high-fat diet (HFD) showed differential trafficking of AT1-ILCs, particularly in response to short- and long-term HFD and diet restriction. At steady state, AT1-ILCs displayed cytotoxic activity toward adipose tissue macrophages (ATMs). Depletion of AT1-ILCs and perforin deficiency resulted in alterations in the ratio of inflammatory to anti-inflammatory ATMs, and adoptive transfer of AT1-ILCs exacerbated metabolic disorder. Diet-induced obesity impaired AT1-ILC killing ability. Our findings reveal a role for AT1-ILCs in regulating ATM homeostasis through cytotoxicity and suggest that this function is relevant in both homeostasis and metabolic disease.

Altered distribution and increased IL-17 production by mucosal-associated invariant T cells in adult and childhood obesity

Mucosal-associated invariant T (MAIT) cells are innate MHC-unrestricted cells that regulate inflammatory responses through the rapid production of cytokines. In this article, we show that circulating MAIT cells are depleted in obese adults, and depletion is associated with diabetic status. Circulating MAIT cells more frequently produced IL-17 upon stimulation ex vivo, a cytokine implicated in insulin resistance. MAIT cells were enriched in adipose tissue (AT) compared with blood. AT MAIT cells, but not circulating MAIT cells, were capable of producing IL-10. In AT from obese subjects, MAIT cells were depleted, were less likely to produce IL-10, and more frequently produced IL-17. Finally, we show that IL-17(+) MAIT cells are also increased in childhood obesity, and altered MAIT cell frequencies in obese children are positively associated with insulin resistance. These data indicate that MAIT cells are enriched in human AT and display an IL-17(+) phenotype in both obese adults and children, correlating with levels of insulin resistance. The alterations in MAIT cells may be contributing to obesity-related sterile inflammation and insulin resistance.

Cutting edge: CD1d restriction and Th1/Th2/Th17 cytokine secretion by human Vδ3 T cells

Human γδ T cells expressing the Vδ3 TCR make up a minor lymphocyte subset in blood but are enriched in liver and in patients with some chronic viral infections and leukemias. We analyzed the frequencies, phenotypes, restriction elements, and functions of fresh and expanded peripheral blood Vδ3 T cells. Vδ3 T cells accounted for ~0.2% of circulating T cells, included CD4(+), CD8(+), and CD4(-)CD8(-) subsets, and variably expressed CD56, CD161, HLA-DR, and NKG2D but neither NKG2A nor NKG2C. Vδ3 T cells were sorted and expanded by mitogen stimulation in the presence of IL-2. Expanded Vδ3 T cells recognized CD1d but not CD1a, CD1b, or CD1c. Upon activation, they killed CD1d(+) target cells, released Th1, Th2, and Th17 cytokines, and induced maturation of dendritic cells into APCs. Thus, Vδ3 T cells are glycolipid-reactive T cells with distinct Ag specificities but functional similarities to NKT cells.

Tumour tissue microenvironment can inhibit dendritic cell maturation in colorectal cancer

Inflammatory mediators in the tumour microenvironment promote tumour growth, vascular development and enable evasion of anti-tumour immune responses, by disabling infiltrating dendritic cells. However, the constituents of the tumour microenvironment that directly influence dendritic cell maturation and function are not well characterised. Our aim was to identify tumour-associated inflammatory mediators which influence the function of dendritic cells. Tumour conditioned media obtained from cultured colorectal tumour explant tissue contained high levels of the chemokines CCL2, CXCL1, CXCL5 in addition to VEGF. Pre-treatment of monocyte derived dendritic cells with this tumour conditioned media inhibited the up-regulation of CD86, CD83, CD54 and HLA-DR in response to LPS, enhancing IL-10 while reducing IL-12p70 secretion. We examined if specific individual components of the tumour conditioned media (CCL2, CXCL1, CXCL5) could modulate dendritic cell maturation or cytokine secretion in response to LPS. VEGF was also assessed as it has a suppressive effect on dendritic cell maturation. Pre-treatment of immature dendritic cells with VEGF inhibited LPS induced upregulation of CD80 and CD54, while CXCL1 inhibited HLA-DR. Interestingly, treatment of dendritic cells with CCL2, CXCL1, CXCL5 or VEGF significantly suppressed their ability to secrete IL-12p70 in response to LPS. In addition, dendritic cells treated with a combination of CXCL1 and VEGF secreted less IL-12p70 in response to LPS compared to pre-treatment with either cytokine alone. In conclusion, tumour conditioned media strongly influences dendritic cell maturation and function.

NK cells in childhood obesity are activated, metabolically stressed, and functionally deficient

Childhood obesity is a major global concern, with over 50 million children now classified as obese. Obesity has been linked to the development of numerous chronic inflammatory diseases, including type 2 diabetes and multiple cancers. NK cells are a subset of innate effector cells, which play an important role in the regulation of adipose tissue and antitumor immunity. NK cells can spontaneously kill transformed cells and coordinate subsequent immune responses through their production of cytokines. We investigated the effect of obesity on NK cells in a cohort of obese children, compared to children with a healthy weight. We demonstrated a reduction in peripheral NK cell frequencies in childhood obesity and inverse correlations with body mass index and insulin resistance. Compared with NK cells from children with normal weight, we show increased NK cell activation and metabolism in obese children (PD-1, mTOR activation, ECAR, and mitochondrial ROS), along with a reduced capacity to respond to stimulus, ultimately leading to loss of function (proliferation and tumor lysis). Collectively we show that NK cells from obese children are activated, metabolically stressed, and losing the ability to perform their basic duties. Paired with the reduction in NK cell frequencies in childhood obesity, this suggests that the negative effect on antitumor immunity is present early in the life course of obesity and certainly many years before the development of overt malignancies.

Distinct and overlapping effector functions of expanded human CD4+, CD8α+ and CD4-CD8α- invariant natural killer T cells

CD1d-restricted invariant natural killer T (iNKT) cells have diverse immune stimulatory/regulatory activities through their ability to release cytokines and to kill or transactivate other cells. Activation of iNKT cells can protect against multiple diseases in mice but clinical trials in humans have had limited impact. Clinical studies to date have targeted polyclonal mixtures of iNKT cells and we proposed that their subset compositions will influence therapeutic outcomes. We sorted and expanded iNKT cells from healthy donors and compared the phenotypes, cytotoxic activities and cytokine profiles of the CD4(+), CD8α(+) and CD4(-)CD8α(-) double-negative (DN) subsets. CD4(+) iNKT cells expanded more readily than CD8α(+) and DN iNKT cells upon mitogen stimulation. CD8α(+) and DN iNKT cells most frequently expressed CD56, CD161 and NKG2D and most potently killed CD1d(+) cell lines and primary leukemia cells. All iNKT subsets released Th1 (IFN-γ and TNF-α) and Th2 (IL-4, IL-5 and IL-13) cytokines. Relative amounts followed a CD8α>DN>CD4 pattern for Th1 and CD4>DN>CD8α for Th2. All iNKT subsets could simultaneously produce IFN-γ and IL-4, but single-positivity for IFN-γ or IL-4 was strikingly rare in CD4(+) and CD8α(+) fractions, respectively. Only CD4(+) iNKT cells produced IL-9 and IL-10; DN cells released IL-17; and none produced IL-22. All iNKT subsets upregulated CD40L upon glycolipid stimulation and induced IL-10 and IL-12 secretion by dendritic cells. Thus, subset composition of iNKT cells is a major determinant of function. Use of enriched CD8α(+), DN or CD4(+) iNKT cells may optimally harness the immunoregulatory properties of iNKT cells for treatment of disease.

The impact of childhood obesity on inflammation, innate immune cell frequency, and metabolic microRNA expression

BACKGROUND

Obesity is characterized by chronic inflammation, immune dysregulation, and alteration of gene expression, associated with type 2 diabetes mellitus and cardiovascular disease. The degree to which these changes occur in childhood obesity is not fully defined.

AIMS AND METHODS

The aim was to investigate the effect of childhood obesity on immune cell frequency, macrophage activation, cytokine production, and specific regulators of metabolic gene expression. Profiling was performed on peripheral blood from 29 obese and 20 nonobese children using real-time PCR, ELISA, and flow cytometry.

RESULTS

Fasting glucose was similar in both groups, but there was a higher degree of insulin resistance in obese subjects (homeostasis model of assessment for insulin resistance, 4.8 vs 0.84; P < .001). Soluble CD163, a marker of macrophage polarization to a proinflammatory profile, was elevated in the obese compared to nonobese children (135 vs 105 ng/mL; P = .03). Invariant natural killer T cells were reduced in the obese children (CD3 T cells, 0.31 vs 0.53%; P = .001). Cytokine profiling revealed significantly elevated TNF-α (6.7 vs 5.1 pg/mL; P = .01) and leptin (1186 vs 432 pg/mL; P < .001) and reduced adiponectin (884 vs 1321 pg/mL; P = .001) in obese compared to nonobese children. Stimulation of peripheral blood mononuclear cells from obese children resulted in higher levels of IL-1β (2100 vs 1500 pg/mL; P = .018). There was a 4-fold increase in expression of microRNA33a (P = .001) and a 3-fold increase in microRNA33b (P = .017) in obese children.

CONCLUSION

Childhood obesity is associated with changes in immune cell frequency, inflammatory environment, and regulation of metabolic gene expression. These changes have been causally linked to the onset of metabolic disease in adulthood and suggest the future trajectory of obese children to the development of type 2 diabetes mellitus and premature cardiovascular disease.

The helminth T2 RNase ω1 promotes metabolic homeostasis in an IL-33- and group 2 innate lymphoid cell-dependent mechanism

Induction of a type 2 cellular response in the white adipose tissue leads to weight loss and improves glucose homeostasis in obese animals. Injection of obese mice with recombinant helminth-derived Schistosoma mansoni egg-derived ω1 (ω1), a potent inducer of type 2 activation, improves metabolic status involving a mechanism reliant upon release of the type 2 initiator cytokine IL-33. IL-33 initiates the accumulation of group 2 innate lymphoid cells (ILC2s), eosinophils, and alternatively activated macrophages in the adipose tissue. IL-33 release from cells in the adipose tissue is mediated by the RNase activity of ω1; however, the ability of ω1 to improve metabolic status is reliant upon effective binding of ω1 to CD206. We demonstrate a novel mechanism for RNase-mediated release of IL-33 inducing ILC2-dependent improvements in the metabolic status of obese animals.

Changes in human dendritic cell number and function in severe obesity may contribute to increased susceptibility to viral infection

Dendritic cells (DCs) are key immune sentinels linking the innate and adaptive immune systems. DCs recognise danger signals and initiate T-cell tolerance, memory and polarisation. They are critical cells in responding to a viral illness. Obese individuals have been shown to have an impaired response to vaccinations against virally mediated conditions and to have an increased susceptibility to multi-organ failure in response to viral illness. We investigated if DCs are altered in an obese cohort (mean body mass index 51.7±7.3 kg m(-2)), ultimately resulting in differential T-cell responses. Circulating DCs were found to be significantly decreased in the obese compared with the lean cohort (0.82% vs 2.53%). Following Toll-like receptor stimulation, compared with lean controls, DCs generated from the obese cohort upregulated significantly less CD83 (40% vs 17% mean fluorescence intensity), a molecule implicated in the elicitation of T-cell responses, particularly viral responses. Obese DCs produced twofold more of the immunosuppressive cytokine interleukin (IL)-10 than lean controls, and in turn stimulated fourfold more IL-4-production from allogenic naive T cells. We conclude that obesity negatively impacts the ability of DCs to mature and elicit appropriate T-cell responses to a general stimulus. This may contribute to the increased susceptibility to viral infection observed in severe obesity.

Interleukin-36 cytokines alter the intestinal microbiome and can protect against obesity and metabolic dysfunction

Members of the interleukin-1 (IL-1) family are important mediators of obesity and metabolic disease and have been described to often play opposing roles. Here we report that the interleukin-36 (IL-36) subfamily can play a protective role against the development of disease. Elevated IL-36 cytokine expression is found in the serum of obese patients and negatively correlates with blood glucose levels among those presenting with type 2 diabetes. Mice lacking IL-36Ra, an IL-36 family signalling antagonist, develop less diet-induced weight gain, hyperglycemia and insulin resistance. These protective effects correlate with increased abundance of the metabolically protective bacteria Akkermansia muciniphila in the intestinal microbiome. IL-36 cytokines promote its outgrowth as well as increased colonic mucus secretion. These findings identify a protective role for IL-36 cytokines in obesity and metabolic disease, adding to the current understanding of the role the broader IL-1 family plays in regulating disease pathogenesis.

IL-36α,β and ɣ are IL-1-related cytokines promoting inflammation in the skin and intestine. Here the authors show they are elevated in individuals with obesity, and that mice lacking the IL-36 receptor antagonist are more resistant to diet-induced obesity and metabolic dysfunction, which depends on intestinal microbiota.

Obesity Reduces mTORC1 Activity in Mucosal-Associated Invariant T Cells, Driving Defective Metabolic and Functional Responses

Obesity underpins the development of numerous chronic diseases, such as type II diabetes mellitus. It is well established that obesity negatively alters immune cell frequencies and functions. Mucosal-associated invariant T (MAIT) cells are a population of innate T cells, which we have previously reported are dysregulated in obesity, with altered circulating and adipose tissue frequencies and a reduction in their IFN-γ production, which is a critical effector function of MAIT cells in host defense. Hence, there is increased urgency to characterize the key molecular mechanisms that drive MAIT cell effector functions and to identify those which are impaired in the obesity setting. In this study, we found that MAIT cells significantly upregulate their rates of glycolysis upon activation in an mTORC1-dependent manner, and this is essential for MAIT cell IFN-γ production. Furthermore, we show that mTORC1 activation is dependent on amino acid transport via SLC7A5. In obese patients, using RNA sequencing, Seahorse analysis, and a series of in vitro experiments, we demonstrate that MAIT cells isolated from obese adults display defective glycolytic metabolism, mTORC1 signaling, and SLC7A5 aa transport. Collectively, our data detail the intrinsic metabolic pathways controlling MAIT cell cytokine production and highlight mTORC1 as an important metabolic regulator that is impaired in obesity, leading to altered MAIT cell responses.

Mucosal-Associated Invariant T Cells Display Diminished Effector Capacity in Oesophageal Adenocarcinoma

Oesophageal adenocarcinoma (OAC) is an aggressive malignancy with poor prognosis, and incidence is increasing rapidly in the Western world. Mucosal-associated invariant T (MAIT) cells recognize bacterial metabolites and kill infected cells, yet their role in OAC is unknown. We aimed to elucidate the role of MAIT cells during cancer development by characterizing the frequency, phenotype, and function of MAIT cells in human blood and tissues, from OAC and its pre-malignant inflammatory condition Barrett's oesophagus (BO). Blood and tissues were phenotyped by flow cytometry and conditioned media from explanted tissue was used to model the effects of the tumor microenvironment on MAIT cell function. Associations were assessed between MAIT cell frequency, circulating inflammatory markers, and clinical parameters to elucidate the role of MAIT cells in inflammation driven cancer. MAIT cells were decreased in BO and OAC blood compared to healthy controls, but were increased in oesophageal tissues, compared to BO-adjacent tissue, and remained detectable after neo-adjuvant treatment. MAIT cells in tumors expressed CD8, PD-1, and NKG2A but lower NKG2D than BO cohorts. MAIT cells produced less IFN-γ and TNF-α in the presence of tumor-conditioned media. OAC cell line viability was reduced upon exposure to expanded MAIT cells. Serum levels of chemokine IP-10 were inversely correlated with MAIT cell frequency in both tumors and blood. MAIT cells were higher in the tumors of node-negative patients, but were not significantly associated with other clinical parameters. This study demonstrates that OAC tumors are infiltrated by MAIT cells, a type of CD8 T cell featuring immune checkpoint expression and cytotoxic potential. These findings may have implications for immunotherapy and immune scoring approaches.

Lymphocyte roles in metabolic dysfunction: of men and mice

Type 2 diabetes (T2D) is a metabolic disease associated with obesity-related insulin resistance (IR) and chronic inflammation. Animal studies indicate that IR can be caused and/or exacerbated by systemic and/or tissue-specific alterations in lymphocyte differentiation and function. Human studies also indicate that obesity-associated inflammation promotes IR. Nevertheless, clinical trials with anti-inflammatory therapies have yielded modest impacts on established T2D. Unlike mouse models, where obesity is predominantly associated with IR, 20-25% of obese humans are metabolically healthy with high insulin sensitivity. The uncoupling of obesity from IR in humans but not in animal models advocates for a more comprehensive understanding of mediators and mechanisms of human obesity-promoted IR, and better integration of knowledge from human studies into animal experiments to efficiently pursue T2D prevention and treatment.

Human invariant NKT cell subsets differentially promote differentiation, antibody production, and T cell stimulation by B cells in vitro

Invariant NK T (iNKT) cells can provide help for B cell activation and Ab production. Because B cells are also capable of cytokine production, Ag presentation, and T cell activation, we hypothesized that iNKT cells will also influence these activities. Furthermore, subsets of iNKT cells based on CD4 and CD8 expression that have distinct functional activities may differentially affect B cell functions. We investigated the effects of coculturing expanded human CD4(+), CD8α(+), and CD4(-)CD8α(-) double-negative (DN) iNKT cells with autologous peripheral B cells in vitro. All iNKT cell subsets induced IgM, IgA, and IgG release by B cells without needing the iNKT cell agonist ligand α-galactosylceramide. Additionally, CD4(+) iNKT cells induced expansions of cells with phenotypes of regulatory B cells. When cocultured with α-galactosylceramide-pulsed B cells, CD4(+) and DN iNKT cells secreted Th1 and Th2 cytokines but at 10-1000-fold lower levels than when cultured with dendritic cells. CD4(+) iNKT cells reciprocally induced IL-4 and IL-10 production by B cells. DN iNKT cells expressed the cytotoxic degranulation marker CD107a upon exposure to B cells. Remarkably, whereas iNKT cell subsets could induce CD40 and CD86 expression by B cells, iNKT cell-matured B cells were unable to drive proliferation of autologous and alloreactive conventional T cells, as seen with B cells cultured in the absence of iNKT cells. Therefore, human CD4(+), CD8α(+), and DN iNKT cells can differentially promote and regulate the induction of Ab and T cell responses by B cells.

Innate PD-L1 limits T cell-mediated adipose tissue inflammation and ameliorates diet-induced obesity

Obesity has become a major health problem in the industrialized world. Immune regulation plays an important role in adipose tissue homeostasis; however, the initial events that shift the balance from a noninflammatory homeostatic environment toward inflammation leading to obesity are poorly understood. Here, we report a role for the costimulatory molecule programmed death-ligand 1 (PD-L1) in the limitation of diet-induced obesity. Functional ablation of PD-L1 on dendritic cells (DCs) using conditional knockout mice increased weight gain and metabolic syndrome during diet-induced obesity, whereas PD-L1 expression on type 2 innate lymphoid cells (ILC2s), T cells, and macrophages was dispensable for obesity control. Using in vitro cocultures, DCs interacted with T cells and ILC2s via the PD-L1:PD-1 axis to inhibit T helper type 1 proliferation and promote type 2 polarization, respectively. A role for PD-L1 in adipose tissue regulation was also shown in humans, with a positive correlation between PD-L1 expression in visceral fat of people with obesity and elevated body weight. Thus, we define a mechanism of adipose tissue homeostasis controlled by the expression of PD-L1 by DCs, which may be a clinically relevant finding with regard to immune-related adverse events during immune checkpoint inhibitor therapy.

Invariant Natural Killer T Cell Deficiency and Functional Impairment in Sleep Apnea: Links to Cancer Comorbidity

STUDY OBJECTIVES

Emerging evidence links obstructive sleep apnea (OSA) with increased cancer incidence and mortality. Invariant natural killer T (iNKT) cells play an important role in cancer immunity. We hypothesized that patients with OSA have low number of circulating invariant natural killer T (iNKT) cells, which may also be functionally impaired. This study aims to evaluate the frequency of circulating iNKT cells in OSA.

DESIGN

We evaluated the frequency of circulating iNKT cells by flow cytometry in 33 snorers being assessed for possible OSA. Using iNKT cell lines, we also evaluated the effect of exposure to hypoxia over 24 hours on apoptosis, cytotoxicity, and cytokine production.

SETTING

Teaching hospital based sleep unit and research laboratory.

PATIENTS

Thirty-three snorers were evaluated: 9 with no OSA (apnea-hypopnea frequency [AHI] < 5/h), 12 with mild-moderate OSA (AHI 5-30) and 12 with severe OSA (AHI > 30).

MEASUREMENTS AND RESULTS

Patients with severe OSA had considerably fewer iNKT cells (0.18%) compared to patients with mild-moderate (0.24%) or no OSA (0.35%), P = 0.0026. The frequency of iNKT cells correlated negatively with apnea-hypopnea index (r = -0.58, P = 0.001), oxygen desaturation index (r = -0.58, P = 0.0003), and SpO2% < 90% (r = -0.5407, P = 0.005). The frequency of iNKT cells increased following 12 months of nCPAP therapy (P = 0.015). Hypoxia resulted in increased apoptosis (P = 0.016) and impaired cytotoxicity (P = 0.035).

CONCLUSION

Patients with obstructive sleep apnea (OSA) have significantly reduced levels of circulating invariant natural killer T (iNKT) cells and hypoxia leads to impaired iNKT cell function. These observations may partly explain the increased cancer risk reported in patients with OSA.

Correlation between maternal inflammatory markers and fetomaternal adiposity

Outside pregnancy, both obesity and diabetes mellitus are associated with changes in inflammatory cytokines. Obesity in pregnancy may be complicated by gestational diabetes mellitus (GDM) and/or fetal macrosomia. The objective of this study was to determine the correlation between maternal cytokines and fetomaternal adiposity in the third trimester in women where the important confounding variable GDM had been excluded. Healthy women with a singleton pregnancy and a normal glucose tolerance test at 28 weeks gestation were enrolled at their convenience. Maternal cytokines were measured at 28 and 37 weeks gestation. Maternal adiposity was assessed indirectly by calculating the Body Mass Index (BMI), and directly by bioelectrical impedance analysis. Fetal adiposity was assessed by ultrasound measurement of fetal soft tissue markers and by birthweight at delivery. Of the 71 women studied, the mean maternal age and BMI were 29.1 years and 29.2 kg/m(2) respectively. Of the women studied 32 (45%) were obese. Of the cytokines, only maternal IL-6 and IL-8 correlated with maternal adiposity. Maternal TNF-α, IL-β, IL-6 and IL-8 levels did not correlate with either fetal body adiposity or birthweight. In this well characterised cohort of pregnant non-diabetic women in the third trimester of pregnancy we found that circulating maternal cytokines are associated with maternal adiposity but not with fetal adiposity.

Tissue specific regulation of glucocorticoids in severe obesity and the response to significant weight loss following bariatric surgery (BARICORT)

CONTEXT

Tissue cortisol exposure is under the control of the isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD). 11β-HSD1 in vivo, acts as an oxoreductase converting inactive cortisone to active cortisol. We hypothesized that 11β-HSD1 activity is dysregulated in obesity and alters following bariatric surgery induced weight loss in different tissues.

METHODS

We recruited 21 patients prior to undergoing bariatric surgery and performed cortisol generation profiles (following oral cortisone administration), urinary corticosteroid metabolite analysis, adipose tissue microdialysis, and tissue gene expression before and after weight loss, following bariatric surgery. Archived tissue samples from 20 previous bariatric surgery patients were also used for tissue gene expression studies.

RESULTS

Gene expression showed a positive correlation with 11β-HSD1 and BMI in omental adipose tissue (OM) (r = +0.52, P = .0001) but not sc adipose tissue (r = +0.28, P = .17). 11β-HSD1 expression in liver negatively correlated with body mass index (BMI) (r = -0.37, P = .04). 11β-HSD1 expression in sc adipose tissue was significantly reduced after weight loss (0.41 ± 0.28 vs 0.17 ± 0.1 arbitrary units, P = .02). Following weight loss, serum cortisol generation increased during a cortisol generation profile (area under the curve 26 768 ± 16 880 vs 47 579 ± 16 086 nmol/L/minute, P ≤ .0001.) Urinary corticosteroid metabolites demonstrated a significant reduction in total cortisol metabolites after bariatric surgery (15 224 ± 6595 vs 8814 ± 4824 μg/24 h, P = .01). Microdialysis of sc adipose tissue showed a threefold reduction in cortisol/cortisone ratio after weight loss.

CONCLUSIONS

This study highlights the differences in tissue specific regulation of cortisol metabolism in obesity and after weight loss. Following bariatric surgery hepatic 11β-HSD1 activity increases, sc adipose tissue 11β-HSD1 activity is reduced and total urinary cortisol metabolites are reduced indicating a possible reduction in hypothalamic pituitary adrenal axis drive. 11β-HSD1 expression correlates positively with BMI in omental adipose tissue and negatively within hepatic tissue. 11β-HSD1 expression is reduced in sc adipose tissue after weight loss.

Cigarette smoke alters the invariant natural killer T cell function and may inhibit anti-tumor responses

Invariant natural killer T (iNKT) cells are a minor subset of human T cells which express the invariant T cell receptor Vα24 Jα18 and recognize glycolipids presented on CD1d. Invariant NKT cells are important immune regulators and can initiate anti-tumor responses through early potent cytokine production. Studies show that iNKT cells are defective in certain cancers. Cigarette smoke contains many carcinogens and is implicated directly and indirectly in many cancers. We investigated the effects of cigarette smoke on the circulating iNKT cell number and function. We found that the iNKT cell frequency is significantly reduced in cigarette smoking subjects. Invariant NKT cells exposed to cigarette smoke extract (CSE) showed significant defects in cytokine production and the ability to kill target cells. CSE inhibits the upregulation of CD107 but not CD69 or CD56 on iNKT cells. These findings suggest that CSE has a specific effect on iNKT cell anti-tumor responses, which may contribute to the role of smoking in the development of cancer.

The role of bacterial antigen detection tests in the diagnosis of bacterial meningitis

We sought to determine the circumstances under which cerebrospinal fluid (CSF) bacterial antigen detection tests. (BADT) are indicated. The medical records of 146 consecutive patients with bacterial meningitis seen from 1986 to 1991 were reviewed retrospectively (mean age 16 months; median eight months). Bacterial meningitis was defined as a positive CSF culture or a positive CSF BADT, in association with the clinical presentation and response to antibiotic treatment consistent with bacterial meningitis. Before lumbar puncture, 61/146 (42%) of meningitis patients had received treatment with antibiotics. CSF BADT was performed on 56/61 (92%) of pretreated patients; of these, 48 (87%) were positive, and 8 (13%) were negative. In this group, 15/61 (25%) of pretreated patients had a negative CSF culture but a positive CSF BADT. All 85 patients who did not receive antibiotics before lumbar puncture had positive CSF cultures and 52/75 (69%) had positive CSF BADT. Because prior antibiotic therapy may impair bacterial growth from the CSF, a CSF BADT should be performed whenever the patient has received prior antibiotic treatment.