Fatty acid compositions of lipids in mesenteric adipose tissue and lymphoid cells in patients with and without Crohn's disease and their therapeutic implications

The Role of the Lymphatic System in the Pathogenesis and Treatment of Inflammatory Bowel Disease

Although the number of therapeutic options for the treatment of inflammatory bowel disease (IBD) has increased in recent years, patients suffer from decreased quality of life due to non-response or loss of response to the currently available treatments. An increased understanding of the disease’s etiology could provide novel insights for treatment strategies in IBD. Lymphatic system components are generally linked to immune responses and presumably related to inflammatory diseases pathophysiology. This review aims to summarize findings on immune-mediated mechanisms in lymphoid tissues linked with IBD pathogenesis and (potential) novel treatments. Enhanced innate and adaptive immune responses were observed in mesenteric lymph nodes (MLNs) and other lymphoid structures, such as Peyer’s patches, in patients with IBD and in animal models. Furthermore, the phenomenon of lymphatic obstruction in the form of granulomas in MLNs and lymphatic vessels correlates with disease activity. There is also evidence that abnormalities in the lymphatic stromal components and lymph node microbiome are common in IBD and could be exploited therapeutically. Finally, novel agents targeting lymphocyte trafficking have been added to the treatment armamentarium in the field of IBD. Overall, gut-associated lymphoid tissue plays a key role in IBD immunopathogenesis, which could offer novel therapeutic targets.

Long Chain Polyunsaturated Fatty Acids Docosahexaenoic Acid and Arachidonic Acid Supplementation in the Suckling and the Post-weaning Diet Influences the Immune System Development of T Helper Type-2 Bias Brown Norway Rat Offspring

Background: Dietary long chain polyunsaturated fatty acids (LCPUFA) such as arachidonic acid (ARA) and docosahexaenoic acid (DHA) play an important role in the development of the infant immune system. The role of LCPUFA in the T helper type 2 (Th2) biased immune system is unknown. We aimed to understand the effect of feeding LCPUFA during suckling and post-weaning on immune system development in Th2 bias Brown Norway rat offspring.

Methods: Brown Norway dams were randomly assigned to nutritionally adequate maternal diet throughout the suckling period (0–3 weeks), namely, control diet (0% ARA, 0% DHA; n= 8) or ARA + DHA (0.45% ARA, 0.8% DHA; n = 10). At 3 weeks, offspring from each maternal diet group were randomized to either a control (0% ARA, 0% DHA; n = 19) or ARA+DHA post-weaning (0.5% ARA, 0.5% DHA; n = 18) diet. At 8 weeks, offspring were killed, and tissues were collected for immune cell function and fatty acid composition analyses.

Results: ARA + DHA maternal diet resulted in higher (p < 0.05) DHA composition in breast milk (4×) without changing ARA levels. This resulted in more mature adaptive immune cells in spleen [T regulatory (Treg) cells and B cells], mesenteric lymph nodes (MLN, lower CD45RA+), and Peyer's patches (PP; higher IgG+, B cells) in the ARA+DHA group offspring at 8 weeks. ARA+DHA post-weaning diet (3–8 weeks) resulted in 2 × higher DHA in splenocyte phospholipids compared to control. This also resulted in higher Th1 cytokines, ~50% higher TNF-α and IFNγ, by PMAi stimulated splenocytes ex vivo, with no differences in Th2 cytokines (IL-4, IL-13, and IL-10) compared to controls.

Conclusion: Feeding dams a diet higher in DHA during the suckling period resulted in adaptive immune cell maturation in offspring at 8 weeks. Providing ARA and DHA during the post-weaning period in a Th2 biased Brown Norway offspring model may support Th1 biased immune response development, which could be associated with a lower risk of developing atopic diseases.

Exposure to the environmental endocrine disruptor TCDD and human reproductive dysfunction: Translating lessons from murine models

Humans and other animals are exposed to a wide array of man-made toxicants, many of which act as endocrine disruptors that exhibit differential effects across the lifespan. In humans, while the impact of adult exposure is known for some compounds, the potential consequences of developmental exposure to endocrine disrupting chemicals (EDCs) is more difficult to ascertain. Animal studies have revealed that exposure to EDCs prior to puberty can lead to adult reproductive disease and dysfunction. Specifically, in adult female mice with an early life exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), we demonstrated a transgenerational occurrence of several reproductive diseases that have been linked to endometriosis in women. Herein, we review the evidence for TCDD-associated development of adult reproductive disease as well as known epigenetic alterations associated with TCDD and/or endometriosis. We will also introduce new "Organ-on-Chip" models which, combined with our established murine model, are expected to further enhance our ability to examine alterations in gene-environment interactions that lead to heritable disease.

Lipidomic profiling in Crohn's disease: abnormalities in phosphatidylinositols, with preservation of ceramide, phosphatidylcholine and phosphatidylserine composition

Crohn's disease is a chronic inflammatory condition largely affecting the terminal ileum and large bowel. A contributing cause is the failure of an adequate acute inflammatory response as a result of impaired secretion of pro-inflammatory cytokines by macrophages. This defective secretion arises from aberrant vesicle trafficking, misdirecting the cytokines to lysosomal degradation. Aberrant intestinal permeability is also well-established in Crohn's disease. Both the disordered vesicle trafficking and increased bowel permeability could result from abnormal lipid composition. We thus measured the sphingo- and phospholipid composition of macrophages, using mass spectrometry and stable isotope labelling approaches. Stimulation of macrophages with heat-killed Escherichia coli resulted in three main changes; a significant reduction in the amount of individual ceramide species, an altered composition of phosphatidylcholine, and an increased rate of phosphatidylcholine synthesis in macrophages. These changes were observed in macrophages from both healthy control individuals and patients with Crohn's disease. The only difference detected between control and Crohn's disease macrophages was a reduced proportion of newly-synthesised phosphatidylinositol 16:0/18:1 over a defined time period. Shotgun lipidomics analysis of macroscopically non-inflamed ileal biopsies showed a significant decrease in this same lipid species with overall preservation of sphingolipid, phospholipid and cholesterol composition.

Simultaneous quantification of fat content and fatty acid composition using MR imaging

Not only the fat content but also the composition of fatty acids (FAs) in stored triglycerides might be of interest in the research on nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. In this study, a novel reconstruction approach is proposed that uses theoretical knowledge of the chemical structure of FAs to simultaneously quantify the fat fraction (FF) and the FAs composition (chain length cl, number of double bonds ndb, and number of methylene-interrupted double bonds nmidb) from multiple gradient echo images. Twenty phantoms with various fat contents (FF = 9-100%) and FA compositions (cl = 12.1-17.9, ndb = 0.23-5.10, and nmidb = 0.04-2.39) were constructed and imaged in a 3-T Siemens scanner. In addition, spectra were acquired in each phantom. Slopes and "standard deviations from true values" were used to investigate the accuracy of the two methods. The imaging method holds well in a comparison to the previously suggested spectroscopy method and showed similar overall accuracy. The in vivo feasibility was demonstrated in the thigh adipose tissue of a healthy volunteer. In conclusion, our developed method is a promising tool for FF and FA composition quantification.

Subcutaneous adipose tissue fatty acid desaturation in adults with and without rare adipose disorders

Background

Elevated stearoyl-CoA desaturase activity has been described in obese states, with an increased desaturation index (DI) suggesting enhanced lipogenesis. Differences in the DI among various phenotypes of abnormal adiposity have not been studied. Abnormal accumulation of subcutaneous adipose tissue occurs in rare adipose disorders (RADs) including Dercum's disease (DD), multiple symmetric lipomatosis (MSL), and familial multiple lipomatosis (FML). Examining the DI in subcutaneous fat of people with DD, MSL and FML may provide information on adipose tissue fatty acid metabolism in these disorders. The aims of this pilot study were: 1) to determine if differences in adipose tissue DIs are present among RADs, and 2) to determine if the DIs correlate to clinical or biochemical parameters.

Methods

Subcutaneous adipose tissue was obtained from human participants with DD (n = 6), MSL (n = 5), FML (n = 8) and obese Controls (n = 6). Fatty acid composition was determined by gas chromatography/mass spectrometry. The DIs (palmitoleic/palmitic, oleic/stearic, vaccenic/stearic ratios) were calculated from the gas chromatogram peak intensities. SCD1 gene expression was determined. Spearman's correlations between the DIs and available clinical or biochemical data were performed.

Results

In DD subjects, the vaccenic/stearic index was lower (p < 0.05) in comparison to Controls. Percent of total of the saturated fatty acid myristic acid was higher in DD compared with Controls and FML. Percent of monounsaturated vaccenic acid in DD trended lower when compared with Controls, and was decreased in comparison to FML. In MSL, total percent of the polyunsaturated fatty acids was significantly lower than in the Control group (p < 0.05). In the total cohort of subjects, the palmitoleic/palmitic and oleic/stearic DIs positively correlated with age, BMI, and percent body fat.

Conclusions

The positive associations between the DIs and measures of adiposity (BMI and percent body fat) support increased desaturase activity in obesity. The lower vaccenic/stearic DI in DD SAT compared with Controls suggests presence of other factors involved in fat accumulation in addition to lifestyle. Other mechanisms driving fat accumulation in DD such as inflammation or lymphatic dysfunction should be investigated.

Role of the lymphatic system in the pathogenesis of Crohn's disease

PURPOSE OF REVIEW

Intestinal lymph containing interstitial fluid, proteins, immune cells, and digested lipids is actively transported back to the blood stream thanks to rhythmical contractions of the mesenteric lymphatic vessels. During this process, lymph flows through several lymph nodes, allowing antigens to be sampled by the immune system. Abnormalities in lymphatic drainage have been noted in the original descriptions of Crohn's disease, but essentially ignored since. The lymphatic system is re-emerging as a critical player in inflammatory and immune processes and the purpose of this review is to present and discuss new concepts related to the involvement of the lymphatic system in the development of inflammatory bowel diseases (IBDs) and more specifically Crohn's disease.

RECENT FINDINGS

Recent studies reporting lymphangitis, lymphangiogenesis, bacterial infiltration and lymph node infection, immune cell trafficking, and fat-wrapping in Crohn's disease suggest altered lymph drainage and lymphatic pumping, implicating the lymphatic system as a likely player in inflammatory disorders and IBDs.

SUMMARY

Improved knowledge and appreciation of the roles that the lymphatic system plays in immune cell trafficking, infection, fat transport, distribution and metabolism and, of course, edema resolution is necessary to better understand the pathogenesis of chronic inflammatory conditions such as Crohn's disease and may provide the basis for new therapeutic strategies.

Influence of a high cholesterol regime on epicardial and subcutaneous adipose tissue fatty acids profile in rabbits

BACKGROUND

We have shown that the fatty acid profile of epicardial adipose tissue (EAT) in patients with obstructed coronary vessels is different from that of the subcutaneous adipose tissue (SAT). The diversity and amount of fatty acids in the adipose tissue can be affected by the component of the lipids in diet. As a result, this study investigated the influence of a high cholesterol regime on EAT and subcutaneous adipose tissue fatty acids profile in rabbits.

METHODS

Sixteen New Zealand white rabbits were randomly divided into two equal groups. The control group received a normal standard diet, whereas the test group was fed with the high cholesterol regime for 2 months. At the end of this period, the rabbits were anesthetized, 1-5 mg of EAT and SAT were removed, and their fatty acids content was determined.

RESULTS

The high cholesterol regime caused a significant increase in low-density lipoprotein (LDL) and triglycerides levels and a marked decrease in high-density lipoprotein (HDL) concentration. After 2 months, in the EAT, fatty acids 16:0 and 18:1t and saturated fatty acid (SFA) showed a significant increase (P<0.05), whereas, fatty acids 12:0, 18:1, 18:2, and 18:3, monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), ω3, and ω6 had a significant decrease (P<0.05). In SAT, fatty acids 18:3, 20:4, 22:6, MUFA, and ω3 decreased and PUFA, SFA, and ω6 significantly increased (P<0.05).

CONCLUSION

Consumption of a high cholesterol regime for 2 months resulted in a significant increase in atherogenic fatty acids and a decrease in antiatherogenic ones in the EAT. EAT is very sensitive to lipid changes of the regime comparing to SAT.

Alternative macrophage activation and metabolism

Obesity and its attendant metabolic disorders represent the great public health challenge of our time. Recent evidence suggests that onset of inflammation in metabolic tissues pathogenically links obesity to insulin resistance and type 2 diabetes. In this review, we briefly summarize the extant literature, paying special attention to the central role of the tissue-associated macrophage in the initiation of metabolic inflammation. We argue that rather than representing simple inflammatory disease, obesity and metabolic syndrome represent derangements in macrophage activation with concomitant loss of metabolic coordination. As such, the sequelae of obesity are as much products of the loss of positive macrophage influences as they are of the presence of deleterious inflammation. The therapeutic implications of this conclusion are profound because they suggest that pharmacologic targeting of macrophage activation, rather than simply inflammation, might be efficacious in treating this global epidemic.

Intestinal dendritic cells: their role in bacterial recognition, lymphocyte homing, and intestinal inflammation

Dendritic cells (DCs) play a key role in discriminating between commensal microorganisms and potentially harmful pathogens and in maintaining the balance between tolerance and active immunity. The regulatory role of DC is of particular importance in the gut where the immune system lies in intimate contact with the highly antigenic external environment. Intestinal DC constantly survey the luminal microenvironment. They act as sentinels, acquiring antigens in peripheral tissues before migrating to secondary lymphoid organs to activate naive T cells. They are also sensors, responding to a spectrum of environmental cues by extensive differentiation or maturation. Recent studies have begun to elucidate mechanisms for functional specializations of DC in the intestine that may include the involvement of retinoic acid and transforming growth factor-β. Specialized CD103(+) intestinal DC can promote the differentiation of Foxp3(+) regulatory T cells via a retinoic acid-dependent process. Different DC outcomes are, in part, influenced by their exposure to microbial stimuli. Evidence is also emerging of the close interaction between bacteria, epithelial cells, and DC in the maintenance of intestinal immune homeostasis. Here we review recent advances of functionally specialized intestinal DC and their mechanisms of antigen uptake and recognition. We also discuss the interaction of DC with intestinal microbiota and their ability to orchestrate protective immunity and immune tolerance in the host. Lastly, we describe how DC functions are altered in intestinal inflammation and their emerging potential as a therapeutic target in inflammatory bowel disease.

Fatty acid composition of epicardial and subcutaneous human adipose tissue

BACKGROUND

Epicardial adipose tissue has special properties that distinguish it from the more widely studied depots of adipose tissue.

OBJECTIVES

We undertook this study to investigate regional differences between epicardial and subcutaneous adipose tissue fat composition, as well as associations between these measures and metabolic variables.

METHODS

Epicardial and subcutaneous peripheral adipose tissue were collected during coronary artery bypass grafting from 42 patients (ages 37-65) with coronary artery disease (CAD). The fatty acid composition of adipose tissue was determined by gas liquid chromatography (GLC).

RESULTS

The saturated fatty acids, including myristic acid (14:0), palmitic acid (16:0), and stearic acid (18:0), were higher, and the unsaturated fatty acids, including palmitoleic acid (16:1n-7), oleic acid (18:1n-9), linoleic acid (18:2n-6), and linolenic acid (18:3n-3), were lower than the subcutaneous adipose tissue. The presence of hypertension was positively correlated with the 16:1n-7 (r = 0.407, P = 0.032) and 18:1n-11(r = 0.370, P = 0.027), and negatively correlated with 18:1n-9 (r = -0.367, P = 0.036) and 18:2n-6 (r = -0.446, P = 0.006) contents of epicardial adipose tissue after adjustment for body mass index.

CONCLUSIONS

Regional differences may be observed in fatty acid composition, suggesting a depot specific impact of stored fatty acids on adipocyte function and metabolism.

Fatty acid composition of adipose tissue and blood in humans and its use as a biomarker of dietary intake

Accurate assessment of fat intake is essential to examine the relationships between diet and disease risk but the process of estimating individual intakes of fat quality by dietary assessment is difficult. Tissue and blood fatty acids, because they are mainly derived from the diet, have been used as biomarkers of dietary intake for a number of years. We review evidence from a wide variety of cross-sectional and intervention studies and summarise typical values for fatty acid composition in adipose tissue and blood lipids and changes that can be expected in response to varying dietary intake. Studies in which dietary intake was strictly controlled confirm that fatty acid biomarkers can complement dietary assessment methodologies and have the potential to be used more quantitatively. Factors affecting adipose tissue and blood lipid composition are discussed, such as the physical properties of triacylglycerol, total dietary fat intake and endogenous fatty acid synthesis. The relationship between plasma lipoprotein concentrations and total plasma fatty acid composition, and the use of fatty acid ratios as indices of enzyme activity are also addressed.

Specialized perinodal fat fuels and fashions immunity

Adipose tissue around lymph nodes is usually removed prior to the study of immune activity-but is it time to reconsider this practice? Perinodal adipose tissue may provide not only a specific lipid resource but also fatty acids, dendritic cells, and soluble mediators that modulate local immunity.

What are subcutaneous adipocytes really good for?

Our acute awareness of the cosmetic, psychosocial and sexual importance of subcutaneous adipose tissue contrasts dramatically with how poorly we have understood the biology of this massive, enigmatic, often ignored and much-abused skin compartment. Therefore, it is timely to recall the exciting, steadily growing, yet underappreciated body of evidence that subcutaneous adipocytes are so much more than just 'fat guys', hanging around passively to conspire, at most, against your desperate attempts to maintain ideal weight. Although the subcutis, quantitatively, tends to represent the dominant architectural component of human skin, conventional wisdom confines its biological key functions to those of energy storage, physical buffer, thermoregulation and thermoinsulation. However, already the distribution of human superficial adipose tissue, by itself, questions how justified the popular belief is that 'skin fat' (which actually may be more diverse than often assumed) serves primarily thermoinsulatory purposes. And although the metabolic complications of obesity are well appreciated, our understanding of how exactly subcutaneous adipocytes contribute to extracutaneous disease - and even influence important immune and brain functions! - is far from complete. The increasing insights recently won into subcutaneous adipose tissue as a cytokine depot that regulates innate immunity and cell growth exemplarily serve to illustrate the vast open research expanses that remain to be fully explored in the subcutis. The following public debate carries you from the evolutionary origins and the key functional purposes of adipose tissue, via adipose-derived stem cells and adipokines straight to the neuroendocrine, immunomodulatory and central nervous effects of signals that originate in the subcutis - perhaps, the most underestimated tissue of the human body. The editors are confident that, at the end, you shall agree: No basic scientist and no doctor with a serious interest in skin, and hardly anyone else in the life sciences, can afford to ignore the subcutaneous adipocyte - beyond its ample impact on beauty, benessence and body mass.

Perinodal Adipose Tissue and Fatty Acid Composition of Lymphoid Tissues in Patients with and without Crohn's Disease and Their Implications for the Etiology and Treatment of CD

The physiological bases for roles of adipose tissue and fatty acids in the symptoms and dietary treatments of Crohn's disease are poorly understood. The hypothesis developed from experiments on rodents that perinodal adipocytes are specialized to provision adjacent lymphoid tissues was tested by comparing the composition of triacylglycerol fatty acids in homologous samples of mesenteric adipose tissue and lymph nodes from patients with or without Crohn's disease. Mesenteric perinodal and other adipose tissue, and lymph nodes, were collected during elective surgery for Crohn's disease and other conditions. Fatty acids were extracted, identified, and quantified by thin-layer and gas-liquid chromatography. Perinodal adipose tissue contained more unsaturated fatty acids than other adipose tissue in controls, as reported for other mammals, but site-specific differences were absent in Crohn's disease. Lipids from adipose and lymphoid tissues had more saturated fatty acids, but fewer polyunsaturates in Crohn's disease patients than controls. In adipose tissue samples, depletion of n-3 polyunsaturates was greatest, but n-6 polyunsaturates, particularly arachidonic acid, were preferentially reduced in lymphoid cells. Ratios of n-6/n-3 polyunsaturates were higher in adipose tissue but lower in lymphoid cells in Crohn's disease patients than in controls. Site-specific differences in fatty acid composition in normal human mesentery are consistent with local interactions between lymph node lymphoid cells and adjacent adipose tissue. But these site-specific properties are absent in Crohn's disease, causing anomalies in composition of lymphoid cell fatty acids, which may explain the efficacy of elemental diets containing oils rich in n-6 polyunsaturates.

Changes in adipocytes and dendritic cells in lymph node containing adipose depots during and after many weeks of mild inflammation

The time course and cellular basis for inflammation-induced hypertrophy of adipose tissue were investigated over 20 weeks in mature male rats. Mild inflammation was induced by subcutaneous injection of 20 microg lipopolysaccharide into one hind-leg three times/week for 4 or 8 weeks, followed by up to 12 weeks 'rest' without intervention. Mean volume and frequency of apoptosis (TUNEL assay) were measured in adipocytes isolated from sites defined by their anatomical relations to lymph nodes, plus numbers of CCL21-stimulated lymph node-derived and adipose tissue-derived dendritic cells. Experimental inflammation increased dendritic cells and adipocyte apoptosis in the locally stimulated popliteal depot and the lymphoid tissue-associated regions of the contralateral popliteal and mesentery and omentum. Responses declined slowly after inflammation ended, but all measurements from the locally stimulated popliteal depot, and the omentum, were still significantly different from controls after 12 weeks rest. The locally stimulated popliteal adipose tissue enlarged by 5% within 4 weeks and remained larger than the control. We conclude that prolonged inflammation induces permanent enlargement, greater adipocyte turnover and increased dendritic cell surveillance in the adjacent adipose tissue and the omentum. The experiment suggests a mechanism for selective hypertrophy of lymphoid tissue-associated adipose tissue in chronic stress and inflammatory disorders, including impaired lymph drainage, Crohn's disease and HIV-associated lipodystrophy, and a link between evolutionary fitness, sexual selection and aesthetically pleasing body symmetry. It would be useful for further study of molecular mechanisms in inflammation-induced local hypertrophy of adipose tissue and development of specific therapies that avoid interference with whole-body lipid metabolism.