A worm of one's own: how helminths modulate host adipose tissue function and metabolism

Helminth Infections and Diabetes: Mechanisms Accounting for Risk Amelioration

The global prevalence of type 2 diabetes mellitus (T2D) is increasing rapidly, with an anticipated 600 million cases by 2035. While infectious diseases such as helminth infections have decreased due to improved sanitation and health care, recent research suggests a link between helminth infections and T2D, with helminths such as Schistosoma, Nippostrongylus, Strongyloides, and Heligmosomoides potentially mitigating or slowing down T2D progression in human and animal models. Helminth infections enhance host immunity by promoting interactions between innate and adaptive immune systems. In T2D, type 1 immune responses are suppressed and type 2 responses are augmented, expanding regulatory T cells and innate immune cells, particularly type 2 immune cells and macrophages. This article reviews recent research shedding light on the favorable effects of helminth infections on T2D. The potential defense mechanisms identified include heightened insulin sensitivity and reduced inflammation. The synthesis of findings from studies investigating parasitic helminths and their derivatives underscores promising avenues for defense against T2D.

Characterization of the Hepatic Transcriptome for Divergent Immune-Responding Sheep Following Natural Exposure to Gastrointestinal Nematodes

Infections with gastrointestinal nematodes (GINs) reduce the economic efficiency of sheep operations and compromise animal welfare. Understanding the host's response to GIN infection can help producers identify animals that are naturally resistant to infection. The objective of this study was to characterize the hepatic transcriptome of sheep that had been naturally exposed to GIN parasites. The hepatic transcriptome was studied using RNA-Sequencing technology in animals characterized as high (n = 5) or medium (n = 6) based on their innate immune acute-phase (AP) response phenotype compared with uninfected controls (n = 4), and with biased antibody-mediated (AbMR, n = 5) or cell-mediated (CMR, n = 5) adaptive immune responsiveness compared to uninfected controls (n = 3). Following the assessment of sheep selected for innate responses, 0, 136, and 167 genes were differentially expressed (DE) between high- and medium-responding animals, high-responding and uninfected control animals, and medium-responding and uninfected control animals, respectively (false discovery rate (FDR) < 0.05, and fold change |FC| > 2). When adaptive immune responses were assessed, 0, 53, and 57 genes were DE between antibody- and cell-biased animals, antibody-biased and uninfected control animals, and cell-biased and uninfected control animals, respectively (FDR < 0.05, |FC| > 2). Functional analyses identified enriched gene ontology (GO) terms and metabolic pathways related to the innate immune response and energy metabolism. Six functional candidate genes were identified for further functional and validation studies to better understand the underlying biological mechanisms of host responses to GINs. These, in turn, can potentially help improve decision making and management practices to increase the overall host immune response to GIN infection.

Effects of helminths and anthelmintic treatment on cardiometabolic diseases and risk factors: A systematic review

BACKGROUND

Globally, helminth infections and cardiometabolic diseases often overlap in populations and individuals. Neither the causal relationship between helminth infections and cardiometabolic diseases nor the effect of helminth eradication on cardiometabolic risk have been reviewed systematically in a large number of human and animal studies.

METHODS

We conducted a systematic review assessing the reported effects of helminth infections and anthelmintic treatment on the development and/or severity of cardiometabolic diseases and risk factors. The search was limited to the most prevalent human helminths worldwide. This study followed PRISMA guidelines and was registered prospectively in PROSPERO (CRD42021228610). Searches were performed on December 10, 2020 and rerun on March 2, 2022 using Ovid MEDLINE ALL (1946 to March 2, 2022), Web of Science, Cochrane Library, Global Index Medicus, and Ovid Embase (1974 to March 2, 2022). Randomized clinical trials, cohort, cross-sectional, case-control, and animal studies were included. Two reviewers performed screening independently.

RESULTS

Eighty-four animal and human studies were included in the final analysis. Most studies reported on lipids (45), metabolic syndrome (38), and diabetes (30), with fewer on blood pressure (18), atherosclerotic cardiovascular disease (11), high-sensitivity C-reactive protein (hsCRP, 5), and non-atherosclerotic cardiovascular disease (4). Fifteen different helminth infections were represented. On average, helminth-infected participants had less dyslipidemia, metabolic syndrome, diabetes, and atherosclerotic cardiovascular disease. Eleven studies examined anthelmintic treatment, of which 9 (82%) reported post-treatment increases in dyslipidemia, metabolic syndrome, and diabetes or glucose levels. Results from animal and human studies were generally consistent. No consistent effects of helminth infections on blood pressure, hsCRP, or cardiac function were reported except some trends towards association of schistosome infection with lower blood pressure. The vast majority of evidence linking helminth infections to lower cardiometabolic diseases was reported in those with schistosome infections.

CONCLUSIONS

Helminth infections may offer protection against dyslipidemia, metabolic syndrome, diabetes, and atherosclerotic cardiovascular disease. This protection may lessen after anthelmintic treatment. Our findings highlight the need for mechanistic trials to determine the pathways linking helminth infections with cardiometabolic diseases. Such studies could have implications for helminth eradication campaigns and could generate new strategies to address the global challenge of cardiometabolic diseases.

The effects of helminth infections against type 2 diabetes

Type 2 diabetes mellitus (T2D) is a prevalent inflammation-related disease characterized by insulin resistance and elevated blood glucose levels. The high incidence rate of T2D in Western societies may be due to environmental conditions, including reduced worm exposure. In human and animal models, some helminths, such as Schistosoma, Nippostrongylus, Strongyloides, and Heligmosomoides, and their products reportedly ameliorate or prevent T2D progression. T2D induces adaptive immune pathways involved in the inhibition of type 1 immune responses, promotion of type 2 immune responses, and expansion of regulatory T cells and innate immune cells, such as macrophages, eosinophils, and group 2 innate lymphoid cells. Among immune cells expanded in T2DM, type 2 immune cells and macrophages are the most important and may have synergistic effects. The stimulation of host immunity by helminth infections also promotes interactions between the innate and adaptive immune systems. In this paper, we provide a comprehensive review of intestinal helminths' protective effects against T2D.

Diminished circulating levels of angiogenic factors and RAGE ligands in helminth-diabetes comorbidity and reversal following anthelmintic treatment

BACKGROUND

Various epidemiological and experimental studies propose that helminths could play a preventive role against the progression of Type 2 diabetes mellitus (T2DM). T2DM induces microvascular and large vessel complications mediated by elevated levels of angiogenic factors and soluble RAGE ligands. However, the interactions between helminths and host angiogenic factors and RAGE ligands are unexplored.

METHODS

To assess the relationship between a soil-transmitted helminth, Strongyloides stercoralis (Ss) and T2DM, we measured plasma levels of VEGF-A, C, D, Angio-1 and Angio-2 and their receptors VEGF-R1, R2 and R3 as well as sRAGE and their ligands AGE, S100A12 and HMBG-1 in individuals with T2DM with Ss+ or without Ss infection (Ss-). In Ss+ individuals, we also measured the levels of aforementioned factors 6 months following anthelmintic therapy.

RESULTS

Ss+ individuals exhibited significantly decreased levels of VEGF-A, C, D, Angio-1 and Angio-2 and their soluble receptors VEGF-R1, R2 and R3, that increased following anthelmintic therapy. Likewise, Ss+ individuals exhibited significantly decreased levels of AGE and their ligands sRAGE, S100A12 and HMBG-1 which reversed following anthelmintic therapy.

CONCLUSION

Our data suggest that Ss infection could play a beneficial role by limiting or delaying the T2DM related vascular complications.

Climate change facilitates a parasite's host exploitation via temperature-mediated immunometabolic processes

Global climate change can influence organismic interactions like those between hosts and parasites. Rising temperatures may exacerbate the exploitation of hosts by parasites, especially in ectothermic systems. The metabolic activity of ectotherms is strongly linked to temperature and generally increases when temperatures rise. We hypothesized that temperature change in combination with parasite infection interferes with the host's immunometabolism. We used a parasite, the avian cestode Schistocephalus solidus, which taps most of its resources from the metabolism of an ectothermic intermediate host, the three-spined stickleback. We experimentally exposed sticklebacks to this parasite, and studied liver transcriptomes 50 days after infection at 13°C and 24°C, to assess their immunometabolic responses. Furthermore, we monitored fitness parameters of the parasite and examined immunity and body condition of the sticklebacks at 13°C, 18°C and 24°C after 36, 50 and 64 days of infection. At low temperatures (13°C), S. solidus growth was constrained, presumably also by the more active stickleback's immune system, thus delaying its infectivity for the final host to 64 days. Warmer temperature (18°C and 24°C) enhanced S. solidus growth, and it became infective to the final host already after 36 days. Overall, S. solidus produced many more viable offspring after development at elevated temperatures. In contrast, stickleback hosts had lower body conditions, and their immune system was less active at warm temperature. The stickleback's liver transcriptome revealed that mainly metabolic processes were differentially regulated between temperatures, whereas immune genes were not strongly affected. Temperature effects on gene expression were strongly enhanced in infected sticklebacks, and even in exposed-but-not-infected hosts. These data suggest that the parasite exposure in concert with rising temperature, as to be expected with global climate change, shifted the host's immunometabolism, thus providing nutrients for the enormous growth of the parasite and, at the same time suppressing immune defence.

Rapidly declining body temperature in a tropical human population

Normal human body temperature (BT) has long been considered to be 37.0°C. Yet, BTs have declined over the past two centuries in the United States, coinciding with reductions in infection and increasing life expectancy. The generality of and reasons behind this phenomenon have not yet been well studied. Here, we show that Bolivian forager-farmers (n = 17,958 observations of 5481 adults age 15+ years) inhabiting a pathogen-rich environment exhibited higher BT when first examined in the early 21st century (~37.0°C). BT subsequently declined by ~0.05°C/year over 16 years of socioeconomic and epidemiological change to ~36.5°C by 2018. As predicted, infections and other lifestyle factors explain variation in BT, but these factors do not account for the temporal declines. Changes in physical activity, body composition, antibiotic usage, and thermal environment are potential causes of the temporal decline.

Trichinella spiralis infection ameliorated diet-induced obesity model in mice

Obesity is an increasingly prevalent disease worldwide, and genetic and environmental factors are known to regulate the development of obesity and associated metabolic diseases. Emerging studies indicate that innate and adaptive immune cell responses in adipose tissue play critical roles in the regulation of metabolic homeostasis. Parasitic helminths are the strongest natural inducers of type 2 inflammatory responses, and several studies have revealed that helminth infections inversely correlate with metabolic syndrome. Hence, this study investigated whether helminth infections could have preventative effects on high fat diet-induced obesity. Female C57BL/6 mice were maintained on either a low fat diet (LFD, 10% fat) or a high fat diet (HFD, 60% fat) for 6 weeks after Trichinella spiralis infection. The mice were randomly divided into four groups and were fed a normal diet, LFD, LFD after T. spiralis infection (Inf + LFD), a high fat diet (HFD), or HFD after T. spiralis infection (HFD + inf). All groups were assayed for body weight, food efficiency ratio (FER), total body weight gain (g)/total food intake amount (g) fat weight, and blood biochemical parameters. Our data indicate that the HFD + inf group significantly reduced body weight gain, fat mass, total cholesterol, and FER. Analysis of immune cell composition by flow cytometry revealed that T. spiralis promoted strong decreases in proinflammatory adipose macrophages (F4/80⁺CD11c⁺) and T cells. The alterations in microbiota from fecal samples of mice were analyzed, which showed that T. spiralis infection decreased the ratio of Firmicutes to Bacteriodetes, thereby restoring the previously increased ratio of Firmicutes to Bacteriodetes in HFD-fed mice. Moreover, elimination of T. spiralis retained the protective effects in the HFD-fed obese mice whereas flubendazole (FLBZ) treatment increased levels of the families Lachnospiraceae and Ruminococcaceae. In summary, we provided novel data suggesting that helminth infection protects against obesity and the protection was closely related to M2 macrophage proliferation, an inhibiting proinflammatory response. In addition, it alters the microbiota in the gut.

Metabolic Consequences of Concomitant Strongyloides stercoralis Infection in Patients With Type 2 Diabetes Mellitus

BACKGROUND

Human and animal studies have demonstrated that helminth infections are associated with a decreased prevalence of type 2 diabetes mellitus (T2DM). However, very little is known about their biochemical and immunological interactions.

METHODS

To assess the relationship between a soil-transmitted helminth, Strongyloides stercoralis (Ss), and T2DM, we examined analytes associated with glycemic control, metabolic processes, and T-cell-driven inflammation at the time of Ss diagnosis and 6 months after definitive anthelmintic treatment. We measured plasma levels of hemoglobin A1c, glucose, insulin, glucagon, adipocytokines, and T-helper (TH) 1-, 2-, and 17- associated cytokines in patients with T2DM with (INF group) or without (UN group) Ss infection. In INF individuals, we again assessed the levels of these analytes 6 months following anthelmintic treatment.

RESULTS

Compared to UN individuals, INF individuals exhibited significantly diminished levels of insulin and glucagon that increased significantly following therapy. Similarly, INF individuals exhibited significantly diminished levels of adiponectin and adipsin that reversed following therapy. INF individuals also exhibited significantly decreased levels of the TH1- and TH17- associated cytokines in comparison to UN individuals; again, anthelmintic therapy augmented these levels. As expected, INF individuals had elevated levels of TH2-associated and regulatory cytokines that normalized following definitive therapy. Multivariate analysis revealed that these changes were independent of age, sex, body mass index, and liver and renal function.

CONCLUSIONS

Strongyloides stercoralis infection is associated with a significant modulation of glycemic, hormonal, and cytokine parameters in T2DM and its reversal following anthelmintic therapy. Hence, Ss infection has a protective effect on diabetes-related parameters.

The acute schistosomiasis mansoni ameliorates metabolic syndrome in the C57BL/6 mouse model

Human and experimental studies have shown that chronic schistosomiasis mansoni protects against metabolic disorders through direct and indirect pathways. This study aims to investigate the co-morbidity between the acute schistosomiasis and nonalcoholic fatty liver. To address this, male C57BL/6 mice fed a high-fat chow (60% fat) or standard chow (10% fat) for 13 weeks and later infected with 80 Schistosoma mansoni cercariae. Mice were assigned into four groups: uninfected fed standard (USC), uninfected fed high-fat chow (UHFC), infected fed standard (ISC), and infected fed high-fat chow (IHFC). Blood sample and tissues were obtained at nine weeks post-infection (acute schistosomiasis) by necropsy. UHFC mice showed higher body mass, visceral adiposity, impaired glucose tolerance, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), triglyceride (TG), and liver steatosis compared to USC mice. IHFC mice showed lower blood lipid levels, blood glucose, improved glucose tolerance, body mass, and liver steatosis (macro and microvesicular) compared to UHFC mice. IHFC showed more massive histopathological changes (sinusoidal fibrosis, hepatocellular ballooning, and inflammatory infiltrates) compared to ISC. In conclusion, the co-morbidity results in both beneficial (friend) and detrimental (foe) for the host. While the acute schistosomiasis improves some metabolic features of metabolic syndrome, comorbidity worsens the liver injury.

Safety and tolerability of experimental hookworm infection in humans with metabolic disease: study protocol for a phase 1b randomised controlled clinical trial

BACKGROUND

Abdominal obesity and presence of the metabolic syndrome (MetS) significantly increase the risk of developing diseases such as Type 2 diabetes mellitus (T2DM) with escalating emergence of MetS and T2DM constituting a significant public health crisis worldwide. Lower prevalence of inflammatory and metabolic diseases such as T2DM in countries with higher incidences of helminth infections suggested a potential role for these parasites in the prevention and management of certain diseases. Recent studies confirmed the potential protective nature of helminth infection against MetS and T2DM via immunomodulation or, potentially, alteration of the intestinal microbiota. This Phase 1b safety and tolerability trial aims to assess the effect of inoculation with helminths on physical and metabolic parameters, immune responses, and the microbiome in otherwise healthy women and men.

METHODS

Participants eligible for inclusion are adults aged 18-50 with central obesity and a minimum of one additional feature of MetS recruited from the local community with a recruitment target of 54. In a randomised, double-blind, placebo-controlled design, three groups will receive either 20 or 40 stage three larvae of the human hookworm Necator americanus or a placebo. Eligible participants will provide blood and faecal samples at their baseline and 6-monthly assessment visits for a total of 24 months with an optional extension to 36 months. During each scheduled visit, participants will also undergo a full physical examination and complete diet (PREDIMED), physical activity, and patient health (PHQ-9) questionnaires. Outcome measurements include tolerability and safety of infection with Necator americanus, changes in metabolic and immunological parameters, and changes in the composition of the faecal microbiome.

DISCUSSION

Rising cost of healthcare associated with obesity-induced metabolic diseases urgently calls for new approaches in disease prevention. Findings from this trial will provide valuable information regarding the potential mechanisms by which hookworms, potentially via alterations in the microbiota, may positively influence metabolic health.

TRIAL REGISTRATION

The protocol was registered on ANZCTR.org.au on 05 June 2017 with identifier ACTRN12617000818336. Alternatively, a Google search using the above trial registration number will yield a direct link to the trial protocol within the ANZCTR website.

Mechanistic Links Between Obesity, Diabetes, and Blood Pressure: Role of Perivascular Adipose Tissue

Obesity is increasingly prevalent and is associated with substantial cardiovascular risk. Adipose tissue distribution and morphology play a key role in determining the degree of adverse effects, and a key factor in the disease process appears to be the inflammatory cell population in adipose tissue. Healthy adipose tissue secretes a number of vasoactive adipokines and anti-inflammatory cytokines, and changes to this secretory profile will contribute to pathogenesis in obesity. In this review, we discuss the links between adipokine dysregulation and the development of hypertension and diabetes and explore the potential for manipulating adipose tissue morphology and its immune cell population to improve cardiovascular health in obesity.

Effects of Opisthorchis viverrini infection on glucose and lipid profiles in human hosts: A cross-sectional and prospective follow-up study from Thailand

Opisthorchis viverrini (OV) infection is endemic to the Northeast Thailand where the prevalence of Type 2 Diabetes mellitus (T2DM) is higher whilst the incidence of cardiovascular diseases (CVDs) is lower than the rest of Thailand. Helminth infection has both nutritional and immunological impact on their definitive hosts. Thus, a cross-sectional study was performed to see the effects of OV infection on glucose and lipid profiles. For this purpose, 200 each of OV infected and uninfected residents were recruited and their glycated hemoglobin (HbA1c), total cholesterol, triglycerides, low- and high-density lipoproteins (LDL and HDL) levels and anthropometric measurements, including BMI were examined. Then, as the prospective follow- up study, changes of those metabolic parameters of OV positive subjects (n = 120) before and after Praziquantel (PZQ) treatment were monitored for six months. The results showed that OV infection has a protective effect against hyperglycemia (OR 0.482 and p = .04) and metabolic disease risk group (OR 0.478 and p = .03). OV positive participants had lower HbA1c (5.5% Vs. 6.01%, p = .001) but higher HDL (54.07 Vs. 49.46 mg/dL, p = .001) than OV negative participants that are statistically significant. After PZQ treatment for OV-positive subjects, their serum levels of HbA1c (p < .05) and HDL (p < .05) significantly rose during the follow up. Apparently, OV infection lowers HbA1c but increases HDL in definitive human hosts.

Synthetic small molecule analogues of the immunomodulatory Acanthocheilonema viteae product ES-62 promote metabolic homeostasis during obesity in a mouse model

One of the most rapidly increasing human public health problems is obesity, whose sequelae like type-2 diabetes, represent continuously worsening, life-long conditions. Over the last 15 years, data have begun to emerge from human and more frequently, mouse studies, that support the idea that parasitic worm infection can protect against this condition. We have therefore investigated the potential of two synthetic small molecule analogues (SMAs) of the anti-inflammatory Acanthocheilonema viteae product ES-62, to protect against metabolic dysfunction in a C57BL/6 J mouse model of high calorie diet-induced obesity. We found weekly subcutaneous administration of the SMAs in combination (1 μg of each), starting one week before continuous exposure to high calorie diet (HCD), decreased fasting glucose levels and reversed the impaired glucose clearance observed in male mice, when measured at approximately 7 and 13 weeks after exposure to HCD. Fasting glucose levels were also-reduced in male mice fed a HCD for some 38 weeks when given SMA-treatment 13 weeks after the start of HCD, indicating an SMA-therapeutic potential. For the most part, protective effects were not observed in female mice. SMA treatment also conferred protection against each of reduced ileum villus length and liver fibrosis, but more prominently in female mice. Previous studies in mice indicate that protection against metabolic dysfunction is usually associated with polarisation of the immune system towards a type-2/anti-inflammatory direction but our attempts to correlate improved metabolic parameters with such changes were unsuccessful. Further analysis will therefore be required to define mechanism of action. Nevertheless, overall our data clearly show the potential of the drug-like SMAs as a preventative or treatment for metabolic dysregulation associated with obesity.

Immune Regulation of Metabolic Homeostasis by Helminths and Their Molecules

Since time immemorial, humans have coevolved with a wide variety of parasitic helminths that have contributed to shape their immune system. The recent eradication of helminth infections in modern societies has coincided with a spectacular rise in inflammatory metabolic diseases, such as obesity, nonalcoholic steatohepatitis, and type 2 diabetes. Landmark studies in the emerging field of immunometabolism have highlighted the central role of the immune system in regulating metabolic functions, notably in adipose tissue, liver, and the gut. In this review we discuss how helminths, which are among the strongest natural inducers of type 2 immunity, and some of their unique immunomodulatory molecules, may contribute to the maintenance of tissue-specific and whole-body metabolic homeostasis and protection against obesity-associated meta-inflammation.

Schistosoma mansoni does not and cannot oxidise fatty acids, but these are used for biosynthetic purposes instead

Adult schistosomes, parasitic flatworms that cause the tropical disease schistosomiasis, have always been considered to be homolactic fermenters and, in their energy metabolism, strictly dependent on carbohydrates. However, more recent studies suggested that fatty acid β-oxidation is essential for egg production by adult female Schistosoma mansoni. To address this conundrum, we performed a comprehensive study on the lipid metabolism of S. mansoni. Incubations with [¹⁴C]-labelled fatty acids demonstrated that adults, eggs and miracidia of S. mansoni did not oxidise fatty acids, as no ¹⁴CO₂ production could be detected. We then re-examined the S. mansoni genome using the genes known to be involved in fatty acid oxidation in six eukaryotic model reference species. This showed that the earlier automatically annotated genes for fatty acid oxidation were in fact incorrectly annotated. In a further analysis we could not detect any genes encoding β-oxidation enzymes, which demonstrates that S. mansoni cannot use this pathway in any of its lifecycle stages. The same was true for Schistosoma japonicum and all other schistosome species that have been sequenced. Absence of β-oxidation, however, does not imply that fatty acids from the host are not metabolised by schistosomes. Adult schistosomes can use and modify fatty acids from their host for biosynthetic purposes and incorporate those in phospholipids and neutral lipids. Female worms deposit large amounts of these lipids in the eggs they produce, which explains why interference with the lipid metabolism in females will disturb egg formation, even though fatty acid β-oxidation does not occur in schistosomes. Our analyses of S. mansoni further revealed that during the development and maturation of the miracidium inside the egg, changes in lipid composition occur which indicate that fatty acids deposited in the egg by the female worm are used for phospholipid biosynthesis required for membrane formation in the developing miracidium.

The response of meteorin-like hormone and interleukin-4 in overweight women during exercise in temperate, warm and cold water

Background Meteorin-like hormone (Metrnl) and interleukin-4 (IL-4) are protein molecules that stimulate the production of brown adipose tissue to improve diseases such as type 2 diabetes and obesity. The aim of this study was to investigate the response of Metrnl protein and IL-4 in overweight women during exercise in temperate, warm and cold water. Materials and methods Thirteen overweight young women (mean age 25.21 ± 3.27 years, body mass index 26.43 ± 1.34 kg/m2) were selected randomly and performed three sessions of interval exercise (40 min per session, 65% of maximum oxygen consumption) in non-consecutive days in temperate (24-25 °C), warm (36.5-37.5 °C) and cold (16.5-17.5 °C) water. Blood sampling was done immediately before and after exercise. Results The Metrnl level significantly increased after exercise in temperate and warm water (p = 0.0001) and significantly decreased in cold water (p = 0.0001). IL-4 level significantly increased after exercise in warm water (p = 0.003), while there was no significant change after exercise in temperate and cold water. Conclusions Exercise in warm water appears to stimulate and accumulate immune cells compared to temperate and cold water. This feature can be used to stimulate the production of hormones such as Metrnl and IL-4 to enhance brown fat, although more studies are needed in this regard.

Defining Eosinophil Function in Adiposity and Weight Loss

Despite promising early work into the role of immune cells such as eosinophils in adipose tissue (AT) homeostasis, recent findings revealed that elevating the number of eosinophils in AT alone is insufficient for improving metabolic impairments in obese mice. Eosinophils are primarily recognized for their role in allergic immunity and defence against parasitic worms. They have also been detected in AT and appear to contribute to adipose homeostasis and drive energy expenditure, but the underlying mechanisms remain elusive. It has long been recognized that immune cells such as macrophages respond to external signals to regulate adipose homeostasis and energy balance, however, less is known about the relevance of eosinophil activity in AT. As the authors propose in this review, given recent debate over the relative importance of their tissue-specific abundance, the stage is now set for exploring the functionality and activation states of AT eosinophils.

Nanomedicine Approaches Against Parasitic Worm Infections

Nanomedicine approaches have the potential to transform the battle against parasitic worm (helminth) infections, a major global health scourge from which billions are currently suffering. It is anticipated that the intersection of two currently disparate fields, nanomedicine and helminth biology, will constitute a new frontier in science and technology. This progress report surveys current innovations in these research fields and discusses research opportunities. In particular, the focus is on: (1) major challenges that helminth infections impose on mankind; (2) key aspects of helminth biology that inform future research directions; (3) efforts to construct nanodelivery platforms to target drugs and genes to helminths hidden in their hosts; (4) attempts in applying nanotechnology to enable vaccination against helminth infections; (5) outlooks in utilizing nanoparticles to enhance immunomodulatory activities of worm-derived factors to cure allergy and autoimmune diseases. In each section, achievements are summarized, limitations are explored, and future directions are assessed.

The impact of a helminth-modified microbiome on host immunity

Intestinal helminths have well-characterized modulatory effects on mammalian immune pathways. Ongoing helminth infection has been associated with both the suppression of allergies and an altered susceptibility to microbial infections. Enteric helminths share a niche with the intestinal microbiota, and the presence of helminths alters the microbiota composition and the metabolic signature of the host. Recent studies have demonstrated that the helminth-modified intestinal microbiome has the capacity to modify host immune responses even in the absence of live helminth infection. This article discusses the mechanisms by which helminths modify the intestinal microbiome of mammals, and reviews the evidence for a helminth-modified microbiome directly influencing host immunity during infectious and inflammatory diseases. Understanding the multifaceted mechanisms that underpin helminth immunomodulation will pave the way for novel therapies to combat infectious and inflammatory diseases.

The Untapped Pharmacopeic Potential of Helminths

The dramatic rise in immunological disorders that occurs with socioeconomic development is associated with alterations in microbial colonization and reduced exposure to helminths. Excretory-secretory (E/S) helminth products contain a mixture of proteins and low-molecular-weight molecules representing the primary interface between parasite and host. Research has shown great pharmacopeic potential for helminth-derived products in animal disease models and even in clinical trials. Although in its infancy, the translation of worm-derived products into therapeutics is highly promising. Here, we focus on important key aspects in the development of immunomodulatory drugs, also highlighting novel approaches that hold great promise for future development of innovative research strategies.

Helminth infection protects against high fat diet-induced obesity via induction of alternatively activated macrophages

Epidemiological studies indicate an inverse correlation between the prevalence of the so-called western diseases, such as obesity and metabolic syndrome, and the exposure to helminths. Obesity, a key risk factor for many chronic health problems, is rising globally and is accompanied by low-grade inflammation in adipose tissues. The precise mechanism by which helminths modulate metabolic syndrome and obesity is not fully understood. We infected high fat diet (HFD)-induced obese mice with the intestinal nematode parasite Heligmosomoides polygyrus and observed that helminth infection resulted in significantly attenuated obesity. Attenuated obesity corresponded with marked upregulation of uncoupling protein 1 (UCP1), a key protein involved in energy expenditure, in adipose tissue, suppression of glucose and triglyceride levels, and alteration in the expression of key genes involved in lipid metabolism. Moreover, the attenuated obesity in infected mice was associated with enhanced helminth-induced Th2/Treg responses and M2 macrophage polarization. Adoptive transfer of helminth-stimulated M2 cells to mice that were not infected with H. polygyrus resulted in a significant amelioration of HFD-induced obesity and increased adipose tissue browning. Thus, our results provide evidence that the helminth-dependent protection against obesity involves the induction of M2 macrophages.

Adipocyte CD1d determines adipose inflammation and insulin resistance in obesity

Obesity-induced adipose tissue inflammation is regulated by various immune cells for innate and adaptive immunity. Among adipose tissue immune cells, it has been proposed that invariant Natural Killer T (iNKT) cells play crucial roles in anti-inflammatory responses in obesity. iNKT cells recognize 'lipid' antigens loaded on CD1d of antigen presenting cells and modulate immune responses by secreting Th1 or Th2 type cytokines depending on species of lipid antigens, antigen presenting cell types, and environmental cytokine milieu. However, the regulatory mechanisms of antigen presenting cells for adipose iNKT cell stimulation have not been clearly elucidated. Recently, we have reported that CD1d expressing adipocytes could act as an antigen presenting cell for adipose iNKT cells by characterization of adipocyte-specific CD1d knockout (CD1d^ADKO) mice. Upon high-fat diet (HFD) feeding, CD1d^ADKO mice aggravated adipose tissue inflammation and insulin resistance compared with CD1d^f/f mice. In this commentary, we provide the additional data of adipocyte CD1d-dependent regulation of adipose iNKT cell responses as well as systemic insulin sensitivity. In addition, we discuss how the interaction between adipocytes and iNKT cells would be regulated with the progression of obesity.

Côte d'Ivoire Dual Burden of Disease (CoDuBu): Study Protocol to Investigate the Co-occurrence of Chronic Infections and Noncommunicable Diseases in Rural Settings of Epidemiological Transition

BACKGROUND

Individual-level concomitance of infectious diseases and noncommunicable diseases (NCDs) is poorly studied, despite the reality of this dual disease burden for many low- and middle-income countries (LMICs).

OBJECTIVE

This study protocol describes the implementation of a cohort and biobank aiming for a better understanding of interrelation of helminth and Plasmodium infections with NCD phenotypes like metabolic syndrome, hypertension, and diabetes.

METHODS

A baseline cross-sectional population-based survey was conducted over one year, in the Taabo health and demographic surveillance system (HDSS) in south-central Côte d'Ivoire. We randomly identified 1020 consenting participants aged ≥18 years in three communities (Taabo-Cité, Amani-Ménou, and Tokohiri) reflecting varying stages of epidemiological transition. Participants underwent health examinations consisting of NCD phenotyping (anthropometry, blood pressure, renal function, glycemia, and lipids) and infectious disease testing (infections with soil-transmitted helminths, schistosomes, and Plasmodium). Individuals identified to have elevated blood pressure, glucose, lipids, or with infections were referred to the central/national health center for diagnostic confirmation and treatment. Aliquots of urine, stool, and venous blood were stored in a biobank for future exposome/phenome research. In-person interviews on sociodemographic attributes, risk factors for infectious diseases and NCDs, medication, vaccinations, and health care were also conducted. Appropriate statistical techniques will be applied in exploring the concomitance of infectious diseases and NCDs and their determinants. Participants' consent for follow-up contact was obtained.

RESULTS

Key results from this baseline study, which will be published in peer-reviewed literature, will provide information on the prevalence and co-occurrence of infectious diseases, NCDs, and their risk factors. The Taabo HDSS consists of rural and somewhat more urbanized areas, allowing for comparative studies at different levels of epidemiological transition. An HDSS setting is ideal as a basis for longitudinal studies since their sustainable field work teams hold close contact with the local population.

CONCLUSIONS

The collaboration between research institutions, public health organizations, health care providers, and staff from the Taabo HDSS in this study assures that the synthesized evidence will feed into health policy towards integrated infectious disease-NCD management. The preparation of health systems for the dual burden of disease is pressing in low- and middle-income countries. The established biobank will strengthen the local research capacity and offer opportunities for biomarker studies to deepen the understanding of the cross-talk between infectious diseases and NCDs.

TRIAL REGISTRATION

International Standard Randomized Controlled Trials Number (ISRCTN): 87099939; http://www.isrctn.com/ISRCTN87099939 (Archived by WebCite at http://www.webcitation.org/6uLEs1EsX).

Helminth antigens counteract a rapid high-fat diet-induced decrease in adipose tissue eosinophils

Brown adipose tissue (BAT) activation and white adipose tissue (WAT) beiging can increase energy expenditure and have the potential to reduce obesity and associated diseases. The immune system is a potential target in mediating brown and beige adipocyte activation. Type 2 and anti-inflammatory immune cells contribute to metabolic homeostasis within lean WAT, with a prominent role for eosinophils and interleukin (IL)-4-induced anti-inflammatory macrophages. We determined eosinophil numbers in epididymal WAT (EpAT), subcutaneous WAT (ScAT) and BAT after 1 day, 3 days or 1 week of high-fat diet (HFD) feeding in C57Bl/6 mice. One day of HFD resulted in a rapid drop in eosinophil numbers in EpAT and BAT, and after 3 days, in ScAT. In an attempt to restore this HFD-induced drop in adipose tissue eosinophils, we treated 1-week HFD-fed mice with helminth antigens from Schistosoma mansoni or Trichuris suis and evaluated whether the well-known protective metabolic effects of helminth antigens involves BAT activation or beiging. Indeed, antigens of both helminth species induced high numbers of eosinophils in EpAT, but failed to induce beiging. In ScAT, Schistosoma mansoni antigens induced mild eosinophilia, which was accompanied by slightly more beiging. No effects were observed in BAT. To study type 2 responses on brown adipocytes directly, T37i cells were stimulated with IL-4. This increased Ucp1 expression and strongly induced the production of eosinophil chemoattractant CCL11 (+26-fold), revealing that brown adipocytes themselves can attract eosinophils. Our findings indicate that helminth antigen-induced eosinophilia fails to induce profound beiging of white adipocytes.

IGF1 Shapes Macrophage Activation in Response to Immunometabolic Challenge

In concert with their phagocytic activity, macrophages are thought to regulate the host immunometabolic responses primarily via their ability to produce specific cytokines and metabolites. Here, we show that IL-4-differentiated, M2-like macrophages secrete IGF1, a hormone previously thought to be exclusively produced from liver. Ablation of IGF1 receptors from myeloid cells reduced phagocytosis, increased macrophages in adipose tissue, elevated adiposity, lowered energy expenditure, and led to insulin resistance in mice fed a high-fat diet. The investigation of adipose macrophage phenotype in obese myeloid IGF1R knockout (MIKO) mice revealed a reduction in transcripts associated with M2-like macrophage activation. Furthermore, the MIKO mice infected with helminth Nippostrongylus brasiliensis displayed delayed resolution from infection with normal insulin sensitivity. Surprisingly, cold challenge did not trigger an overt M2-like state and failed to induce tyrosine hydroxylase expression in adipose tissue macrophages of control or MIKO mice. These results show that IGF1 signaling shapes the macrophage-activation phenotype.

New Data on Human Macrophages Polarization by Hymenolepis diminuta Tapeworm-An In Vitro Study

Helminths and their products can suppress the host immune response to escape host defense mechanisms and establish chronic infections. Current studies indicate that macrophages play a key role in the immune response to pathogen invasion. They can be polarized into two distinct phenotypes: M1 and M2. The present paper examines the impact of the adult Hymenolepis diminuta (HD) tapeworm and its excretory/secretory products (ESP) on THP-1 macrophages. Monocytes were differentiated into macrophages and cultured with a living parasite or its ESP. Our findings indicate that HD and ESP have a considerable impact on human THP-1 macrophages. Macrophages treated with parasite ESP (with or without LPS) demonstrated reduced expression of cytokines (i.e., IL-1α, TNFα, TGFβ, IL-10) and chemokines (i.e., IL-8, MIP-1α, RANTES, and IL-1ra), while s-ICAM and CxCL10 expression rose after ESP stimulation. In addition, inflammatory factor expression rose significantly when macrophages were exposed to living parasites. Regarding induced and repressed pathways, significant differences were found between HD and ESP concerning their influence on the phosphorylation of ERK1/2, STAT2, STAT3, AMPKα1, Akt 1/2/3 S473, Hsp60, and Hck. The superior immunosuppressive properties of ESP compared to HD were demonstrated with lower levels of IL-1β, TNF-α, IL-6, IL-23, and IL-12p70 following stimulation. The presence of HD and its ESP were found to stimulate mixed M1/M2 macrophage phenotypes. Our findings indicate new molecular mechanisms involved in the response of human macrophages to tapeworm infection, this could be a valuable tool in understanding the mechanisms underlying the processes of immune regulation during cestodiasis.

Immune Modulation of Brown(ing) Adipose Tissue in Obesity

Obesity is associated with a variety of medical conditions such as type 2 diabetes and cardiovascular diseases and is therefore responsible for high morbidity and mortality rates. Increasing energy expenditure by brown adipose tissue (BAT) is a current novel strategy to reduce the excessive energy stores in obesity. Brown adipocytes burn energy to generate heat and are mainly activated upon cold exposure. As prolonged cold exposure is not a realistic therapy, researchers worldwide are searching for novel ways to activate BAT and/or induce beiging of white adipose tissue. Recently, the contribution of immune cells in the regulation of brown adipocyte activity and beiging of white adipose tissue has gained increased attention, with a prominent role for eosinophils and alternatively activated macrophages. This review discusses the rediscovery of BAT, presents an overview of modes of activation and differentiation of beige and brown adipocytes, and describes the recently discovered immunological pathways that are key in mediating brown/beige adipocyte development and function. Interventions in immunological pathways harbor the potential to provide novel strategies to increase beige and brown adipose tissue activity as a therapeutic target for obesity.

Do worms protect against the metabolic syndrome? A systematic review and meta-analysis

AIMS

There is increasing evidence on the role of helminth infections in modifying autoimmune and allergic diseases. These infections may have similar effect in other inflammatory processes, such as insulin resistance. This review aims to examine the literature on the effect of helminthic infections on metabolic outcomes in humans.

METHODS

Using the PRISMA protocol, we searched the literature using PubMed, MEDLINE, and a manual review of reference lists. Human studies published in English after 1995 were included. Four papers were included in this review. Data was extracted and a meta-analysis was conducted using a random-effects model. Heterogeneity was assessed using Tau(2) and I(2) tests.

RESULTS

The included studies found that infection was associated with lower glucose levels, less insulin resistance, and/or a lower prevalence of metabolic syndrome (MetS) or type 2 diabetes mellitus (T2DM). Meta-analysis showed that participants with a previous or current helminth infection were 50% less likely to have an endpoint of metabolic dysfunction in comparison to uninfected participants (OR 0.50; 95% CI 0.38-0.66).

CONCLUSION

This review has shown that helminth infections can be associated with improved metabolic outcomes. Understanding of the mechanisms underlying this relationship could facilitate the development of novel strategies to prevent or delay T2DM.

Schistosome-Derived Molecules as Modulating Actors of the Immune System and Promising Candidates to Treat Autoimmune and Inflammatory Diseases

It is long known that some parasite infections are able to modulate specific pathways of host's metabolism and immune responses. This modulation is not only important in order to understand the host-pathogen interactions and to develop treatments against the parasites themselves but also important in the development of treatments against autoimmune and inflammatory diseases. Throughout the life cycle of schistosomes the mammalian hosts are exposed to several biomolecules that are excreted/secreted from the parasite infective stage, named cercariae, from their tegument, present in adult and larval stages, and finally from their eggs. These molecules can induce the activation and modulation of innate and adaptive responses as well as enabling the evasion of the parasite from host defense mechanisms. Immunomodulatory effects of helminth infections and egg molecules are clear, as well as their ability to downregulate proinflammatory cytokines, upregulate anti-inflammatory cytokines, and drive a Th2 type of immune response. We believe that schistosomes can be used as a model to understand the potential applications of helminths and helminth-derived molecules against autoimmune and inflammatory diseases.

Regulation of metabolic health and adipose tissue function by group 2 innate lymphoid cells

Adipose tissue (AT) is home to an abundance of immune cells. With chronic obesity, inflammatory immune cells accumulate and promote insulin resistance and the progression to type 2 diabetes mellitus. In contrast, recent studies have highlighted the regulation and function of immune cells in lean, healthy AT, including those associated with type 2 or "allergic" immunity. Although traditionally activated by infection with multicellular helminthes, AT type 2 immunity is active independently of infection, and promotes tissue homeostasis, AT "browning," and systemic insulin sensitivity, protecting against obesity-induced metabolic dysfunction and type 2 diabetes mellitus. In particular, group 2 innate lymphoid cells (ILC2s) are integral regulators of AT type 2 immunity, producing the cytokines interleukin-5 and IL-13, promoting eosinophils and alternatively activated macrophages, and cooperating with and promoting AT regulatory T (Treg) cells. In this review, we focus on the recent developments in our understanding of group 2 innate lymphoid cell cells and type 2 immunity in AT metabolism and homeostasis.