Alterations in glucose homeostasis in a murine model of Chagas disease

Small molecule mediators of host-T. cruzi-environment interactions in Chagas disease

Small molecules (less than 1,500 Da) include major biological signals that mediate host-pathogen-microbiome communication. They also include key intermediates of metabolism and critical cellular building blocks. Pathogens present with unique nutritional needs that restrict pathogen colonization or promote tissue damage. In parallel, parts of host metabolism are responsive to immune signaling and regulated by immune cascades. These interactions can trigger both adaptive and maladaptive metabolic changes in the host, with microbiome-derived signals also contributing to disease progression. In turn, targeting pathogen metabolic needs or maladaptive host metabolic changes is an important strategy to develop new treatments for infectious diseases. Trypanosoma cruzi is a single-celled eukaryotic pathogen and the causative agent of Chagas disease, a neglected tropical disease associated with cardiac and intestinal dysfunction. Here, we discuss the role of small molecules during T. cruzi infection in its vector and in the mammalian host. We integrate these findings to build a theoretical interpretation of how maladaptive metabolic changes drive Chagas disease and extrapolate on how these findings can guide drug development.

DIAGNOSIS AND TREATMENT OF A NATURAL INFECTION WITH TRYPANOSOMA CRUZI (CHAGAS DISEASE) IN A SYMPTOMATIC DE BRAZZA'S MONKEY (CERCOPITHECUS NEGLECTUS) IN ALABAMA

Trypanosoma cruzi, the causative agent of Chagas disease, is a zoonotic, vector-borne, protozoan hemoflagellate with a wide host range. An 11-yr-old, captive-bred male De Brazza's monkey (Cercopithecus neglecus) presented with weight loss despite normal appetite. Examination revealed hypoglycemia, nonregenerative anemia, and many trypanosomes on a blood smear. A whole blood sample was PCR-positive for T. cruzi discrete typing unit TcIV and the monkey seroconverted using two different methods. The monkey was treated with the standard human dose of benznidazole twice daily for 60 d; however, blood obtained over the next 1.5 yr posttreatment remained PCR-positive for T. cruzi. A second course of benznidazole at a higher dose but lower frequency for 26 wk was required for the monkey to convert to sustained PCR-negative status. The monkey recovered with no apparent lasting effects.

Diets Differently Regulate Tumorigenesis in Young E0771 Syngeneic Breast Cancer Mouse Model

Breast cancer (BC) is the most diagnosed cancer type, accounting for one in eight cancer diagnoses worldwide. Epidemiological studies have shown that obesity is associated with increased risk of BC in post-menopausal women, whereas adiposity reduces the risk of BC in premenopausal women. The mechanistic link between obesity and BC has been examined by combining murine BC models with high-fat diet (HFD) induced obesity. However, the effect of adiposity (not obesity) induced by a short period of HFD consumption on BC pathogenesis is not well understood. In the current study, we examined the effects of different diet compositions on BC pathogenesis using a young E0771 syngeneic BC mouse model fed on either an HFD or regular diet (RD: a low-fat high-carbohydrate diet) for a short period (4 weeks) before implanting mammary tumors in mice. We analyzed the effect of diet composition on the onset of tumor growth, metastasis, and metabolic and immune status in the tumor microenvironment (TME) using various methods including in vivo bioluminescence imaging and immunoblotting analyses. We showed for the first time that a short-term HFD delays the onset of tumorigenesis by altering the immune and metabolic signaling and energy mechanism in the TME. However, RD may increase the risk of tumorigenesis and metastasis by increasing pro-inflammatory factors in the TME in young mice. Our data suggest that diet composition, adipogenesis, and loss of body fat likely regulate the pathogenesis of BC in a manner that differs between young and post-menopausal subjects.

Chagas disease is not associated with diabetes, metabolic syndrome, insulin resistance and beta cell dysfunction at baseline of Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Chagas disease (ChD) affects millions of people worldwide, being endemic in Latin America and emerging in the United States and Europe. Classically described as targeting the heart and gastrointestinal tract, Trypanosoma cruzi parasitism leads to structural and pro-inflammatory changes in the adipose tissue and pancreas. The effects of these changes on insulin resistance (IR), beta cell dysfunction, diabetes mellitus (DM),and metabolic syndrome (MS) are unclear. We aim to evaluate the association of ChD with DM, IR, beta cell dysfunction and MS in the baseline of multi-centric cohort study 'Brazilian Longitudinal Study of Adult Health' (ELSA-Brasil). This cross-sectional analysis included 14,922 (98%) participants of ELSA-Brasil at baseline. To investigate the associations of ChD with DM, IR (assessed by HOMA-IR) and beta cell dysfunction (assessed by HOMA beta), and MS we fitted logistic regression models including socio-demographic and anthropometric variables, health-related conditions and laboratory results. ChD, defined by positive serology, was prevalent in 1.9% (n = 283) of the sample, 17.3% (n = 49) of whom had cardiomyopathy. DM prevalence was 17.25% (n = 2574) and was not different among those with and without ChD (20.5% vs 17.2%; p = 0.28). Fasting and 2 h-blood glucose after a 75 g anhydrous glucose were slightly higher among participants positive for ChD, when compared with those with negative serology (102 mg/dL versus 100 mg/dL, respectively; and 127 mg/dL versus 124 mg/dL, respectively), only in univariate analysis. There was no significant association between these variables and ChD after adjustments. In addition, there was no significant association between DM, IR, beta cell dysfunction or MS and ChD (without and with cardiomyopathy). Our results showed that ChD, regardless of the presence of cardiomyopathy, is not associated with DM, IR, beta cell dysfunction or MS. These findings suggest the parasitism of the adipose tissue and pancreas in Chagas disease do not translate into clinically relevant glucose abnormalities.

Functional Autoreactive Anti-β2 Adrenergic Antibodies May Contribute to Insulin Resistance Profile in Patients with Chronic Chagas Disease

Potential activation of β2 adrenergic receptors (β2AR) by specific autoreactive antibodies (Abs) that arise during the host reaction to Trypanosoma cruzi, could contribute to the elevated prevalence of metabolic disturbances described in patients with chronic Chagas disease (CCD). This study aimed to determine the prevalence of anti-β2AR Abs in patients with CCD, as well as the correlation of these Abs with the presence of glucose and lipid metabolism disturbances, in order to explore their association with an insulin resistance profile. Additionally, we tested the functional effects of anti-β2AR Abs employing an in vitro bioassay with neuroendocrine cells expressing β2AR. A clinical and metabolic evaluation including an OGTT was performed in 80 CCD patients and 40 controls. Anti-β2AR Abs were measured by an in-house-developed ELISA, and the β2 adrenergic activity of affinity-purified IgG fractions from patient’ sera were assayed in CRE-Luc and POMCLuc transfected AtT-20 cells. A higher proportion of dysglycemia (72.5% vs. 37.5%; p = 0.001) was observed in the CCD group, accompanied by increased HOMA2-IR (p = 0.019), especially in subjects with Abs (+). Anti-β2AR Abs reactivity (7.01 (2.39–20.5); p = 0.0004) and age >50 years (3.83 (1.30–11.25); p = 0.014) resulted as relevant for IR prediction (AUC: 0.786). Concordantly, Abs (+) CCD patients showed elevated metabolic risk scores and an increased prevalence of atherogenic dyslipidemia (p = 0.040), as compared to Abs (−) patients and controls. On functional bioassays, Abs exerted specific and dose-dependent β2-agonist effects. Our findings suggest that anti-β2AR Abs may induce the activation of β2AR in other tissues besides the heart; furthermore, we show that in patients with CCD these Abs are associated with an insulin resistance profile and atherogenic dyslipidemia, providing biological plausibility to the hypothesis that adrenergic activation by anti-β2AR Abs could contribute to the pathogenesis of metabolic disturbances described in CCD patients, increasing their cardiovascular risk.

Immune-neuroendocrine and metabolic disorders in human and experimental T. cruzi infection: New clues for understanding Chagas disease pathology

Studies in mice undergoing acute Trypanosoma cruzi infection and patients with Chagas disease, led to identify several immune-neuroendocrine disturbances and metabolic disorders. Here, we review relevant findings concerning such abnormalities and discuss their possible influence on disease physiopathology.

Metabolic syndrome agravates cardiovascular, oxidative and inflammatory dysfunction during the acute phase of Trypanosoma cruzi infection in mice

We evaluated the influence of metabolic syndrome (MS) on acute Trypanosoma cruzi infection. Obese Swiss mice, 70 days of age, were subjected to intraperitoneal infection with 5 × 102 trypomastigotes of the Y strain. Cardiovascular, oxidative, inflammatory, and metabolic parameters were evaluated in infected and non-infected mice. We observed higher parasitaemia in the infected obese group (IOG) than in the infected control group (ICG) 13 and 15 days post-infection. All IOG animals died by 19 days post-infection (dpi), whereas 87.5% of the ICG survived to 30 days. Increased plasma nitrite levels in adipose tissue and the aorta were observed in the IOG. Higher INF-γ and MCP-1 concentrations and lower IL-10 concentrations were observed in the IOG compared to those in the ICG. Decreased insulin sensitivity was observed in obese animals, which was accentuated after infection. Higher parasitic loads were found in adipose and hepatic tissue, and increases in oxidative stress in cardiac, hepatic, and adipose tissues were characteristics of the IOG group. Thus, MS exacerbates experimental Chagas disease, resulting in greater damage and decreased survival in infected animals, and might be a warning sign that MS can influence other pathologies.

Dysregulation of insulin levels in Chagas heart disease is associated with altered adipocytokine levels

Metabolic, inflammatory, and autonomic nervous system (ANS) dysfunction are present in patients with heart failure. However, whether these changes are due to left ventricular dysfunction or heart failure etiology is unknown. We evaluated metabolism and inflammatory activity in patients with idiopathic dilated cardiomyopathy (IDC) and Chagas cardiomyopathy (CHG) and their correlation with the ANS. Forty-six patients were divided into 3 groups: IDC, CHG, and control. We evaluated adiponectin, leptin, insulin, interleukin-6, and tumor necrosis factor-alpha. ANS were analyzed by heart rate variability in time and frequency domains on a 24-hour Holter monitor. Levels of glucose, cholesterol, leptin, and adiponectin did not show differences between groups. Insulin levels were lower in CHG group (5.4 ± 3.3 μU/mL) when compared with control (8.0 ± 4.9 μU/mL) and IDC (9.9 ± 5.0 μU/mL) groups (p = 0.007). Insulin was positively associated with LFr/HFr ratio (r = 0.562; p = 0.029) and with the LFr component (r = 0.562; p = 0.029) and negatively associated with adiponectin (r = -0.603; p = 0.017) in CHG group. The addition of an adiponectin unit reduced average insulin by 0.332 μg/mL. Insulin levels were decreased in the CHG group when compared with the IDC group and were associated with ANS indexes and adiponectin levels.

Limited Foxp3+ Regulatory T Cells Response During Acute Trypanosoma cruzi Infection Is Required to Allow the Emergence of Robust Parasite-Specific CD8+ T Cell Immunity

While it is now acknowledged that CD4⁺ T cells expressing CD25 and Foxp3 (Treg cells) regulate immune responses and, consequently, influence the pathogenesis of infectious diseases, the regulatory response mediated by Treg cells upon infection by Trypanosoma cruzi was still poorly characterized. In order to understand the role of Treg cells during infection by this protozoan parasite, we determined in time and space the magnitude of the regulatory response and the phenotypic, functional and transcriptional features of the Treg cell population in infected mice. Contrary to the accumulation of Treg cells reported in most chronic infections in mice and humans, experimental T. cruzi infection was characterized by sustained numbers but decreased relative frequency of Treg cells. The reduction in Treg cell frequency resulted from a massive accumulation of effector immune cells, and inversely correlated with the magnitude of the effector immune response as well as with emergence of acute immunopathology. In order to understand the causes underlying the marked reduction in Treg cell frequency, we evaluated the dynamics of the Treg cell population and found a low proliferation rate and limited accrual of peripheral Treg cells during infection. We also observed that Treg cells became activated and acquired a phenotypic and transcriptional profile consistent with suppression of type 1 inflammatory responses. To assess the biological relevance of the relative reduction in Treg cells frequency observed during T. cruzi infection, we transferred in vitro differentiated Treg cells at early moments, when the deregulation of the ratio between regulatory and conventional T cells becomes significant. Intravenous injection of Treg cells dampened parasite-specific CD8⁺ T cell immunity and affected parasite control in blood and tissues. Altogether, our results show that limited Treg cell response during the acute phase of T. cruzi infection enables the emergence of protective anti-parasite CD8⁺ T cell immunity and critically influences host resistance.

High fat diet modulates inflammatory parameters in the heart and liver during acute Trypanosoma cruzi infection

The high fat diet (HFD) can trigger metabolic and cardiovascular diseases. Trypanosoma cruzi infection induces progressive inflammatory manifestations capable to affect the structure and the function of important organs such as the heart and liver. Here we aimed to investigate the effects of a HFD on the immune response and matrix metalloproteinase (MMP) activities during acute infection with the T. cruzi strain VL-10. The VL-10 strain has cardiac tropism and causes myocarditis in mice. Male C57BL/6 mice were treated with either: (i) regular diet (Reg) or (ii) HFD for 8 weeks, after which mice in each group were infected with T. cruzi. Mice were euthanized on day 30 after infection, and the liver and heart were subjected to histology and zymography to determine MMP-2 activities and plasma levels of IL-10, TNF, CCL2, and CCL5. T. cruzi-infected HFD animals had higher parasitemia, LDL and total cholesterol levels. Regardless of diet, plasma levels of all inflammatory mediators and cardiac MMP-2 activity were elevated in infected mice in contrast with the low plasma levels of leptin. HFD animals presented micro- and macrovesicular hepatic steatosis, while cardiac leukocyte infiltration was mainly detected in T. cruzi-infected mice. Our findings suggested that a HFD promotes higher circulating T. cruzi load and cardiac and liver immunopathogenesis in an experimental model using the VL-10 strain of the T. cruzi.

Exploring pancreatic pathology in Plasmodium falciparum malaria patients

Hypoglycaemia is an important complication of Plasmodium falciparum malaria infection, which can be lethal if not treated. A decrease in blood sugar (BS) level has been correlated with disease severity, parasitaemia and the use of certain antimalarial drugs. This study explored the relationship between pancreatic pathology, including the expressions of insulin and glucagon in the islets of Langerhans, and the BS levels in P. falciparum malaria patients. Pancreatic tissues from malaria patients were divided into three groups, namely those with BS < 40 mg/dl, BS = 40–120 mg/dl, and BS > 120 mg/dl. In P. falciparum malaria, pancreatic tissues showed numerous parasitised red blood cells (PRBCs) in the capillaries, oedema, acinar necrosis and the presence of inflammatory cells. The islet size and the expression of insulin were significantly increased in P. falciparum malaria patients with hypoglycaemia. In addition, insulin expression was positively correlated with islet size and negatively correlated with BS levels. This pioneer study documents an increase in insulin expression and an increase in islet size in hypoglycaemic patients with P. falciparum malaria. This could contribute to the pathogenesis of hypoglycaemia and provides evidence for the potential need to effectively manage the hypoglycaemia seen in malaria infection.

Chronic Trypanosoma cruzi infection potentiates adipose tissue macrophage polarization toward an anti-inflammatory M2 phenotype and contributes to diabetes progression in a diet-induced obesity model

Chronic obesity and Chagas disease (caused by the protozoan Trypanosoma cruzi) represent serious public health concerns. The interrelation between parasite infection, adipose tissue, immune system and metabolism in an obesogenic context, has not been entirely explored. A novel diet-induced obesity model (DIO) was developed in C57BL/6 wild type mice to examine the effect of chronic infection (DIO+I) on metabolic parameters and on obesity-related disorders. Dyslipidemia, hyperleptinemia, and cardiac/hepatic steatosis were strongly developed in DIO mice. Strikingly, although these metabolic alterations were collectively improved by infection, plasmatic apoB100 levels remain significantly increased in DIO+I, suggesting the presence of pro-atherogenic small and dense LDL particles. Moreover, acute insulin resistance followed by chronic hyperglycemia with hypoinsulinemia was found, evidencing an infection-related-diabetes progression. These lipid and glucose metabolic changes seemed to be highly dependent on TLR4 expression since TLR4-/- mice were protected from obesity and its complications. Notably, chronic infection promoted a strong increase in MCP-1 producing macrophages with a M2 (F4/80+CD11c-CD206+) phenotype associated to oxidative stress in visceral adipose tissue of DIO+I mice. Importantly, infection reduced lipid content but intensified inflammatory infiltrates in target tissues. Thus, parasite persistence in an obesogenic environment and the resulting host immunometabolic dysregulation may contribute to diabetes/atherosclerosis progression.

Modulation of host central carbon metabolism and in situ glucose uptake by intracellular Trypanosoma cruzi amastigotes

Obligate intracellular pathogens satisfy their nutrient requirements by coupling to host metabolic processes, often modulating these pathways to facilitate access to key metabolites. Such metabolic dependencies represent potential targets for pathogen control, but remain largely uncharacterized for the intracellular protozoan parasite and causative agent of Chagas disease, Trypanosoma cruzi. Perturbations in host central carbon and energy metabolism have been reported in mammalian T. cruzi infection, with no information regarding the impact of host metabolic changes on the intracellular amastigote life stage. Here, we performed cell-based studies to elucidate the interplay between infection with intracellular T. cruzi amastigotes and host cellular energy metabolism. T. cruzi infection of non-phagocytic cells was characterized by increased glucose uptake into infected cells and increased mitochondrial respiration and mitochondrial biogenesis. While intracellular amastigote growth was unaffected by decreased host respiratory capacity, restriction of extracellular glucose impaired amastigote proliferation and sensitized parasites to further growth inhibition by 2-deoxyglucose. These observations led us to consider whether intracellular T. cruzi amastigotes utilize glucose directly as a substrate to fuel metabolism. Consistent with this prediction, isolated T. cruzi amastigotes transport extracellular glucose with kinetics similar to trypomastigotes, with subsequent metabolism as demonstrated in ¹³C-glucose labeling and substrate utilization assays. Metabolic labeling of T. cruzi-infected cells further demonstrated the ability of intracellular parasites to access host hexose pools in situ. These findings are consistent with a model in which intracellular T. cruzi amastigotes capitalize on the host metabolic response to parasite infection, including the increase in glucose uptake, to fuel their own metabolism and replication in the host cytosol. Our findings enrich current views regarding available carbon sources for intracellular T. cruzi amastigotes and underscore the metabolic flexibility of this pathogen, a feature predicted to underlie successful colonization of tissues with distinct metabolic profiles in the mammalian host.

The kinetoplastid protozoan, Trypanosoma cruzi, is a highly successful parasite with a broad mammalian host range and the capacity to colonize a variety of tissues within a given host to establish life-long infection. T. cruzi infection causes Chagas disease in humans, characterized by severe cardiomyopathy and gastrointestinal motility disorders, with limited treatment options. Despite the critical role of T. cruzi amastigotes in sustaining mammalian infection, little is known about their metabolic requirements or the range of nutrients available to these parasites in the host cell cytoplasm. Here, we demonstrate that T. cruzi infection triggers a host response in infected cells that includes increased mitochondrial respiration and biogenesis and increased glucose uptake into infected cells. We show that exogenous glucose supports optimal intracellular parasite replication and that cytosolic T. cruzi amastigotes access glucose in situ, potentially via a facilitated transport process characterized here. These findings expand our view of the range of carbons available to the intracellular parasite and suggest even greater metabolic flexibility of the tissue-infective stages of T. cruzi than previously appreciated, a capability predicted to contribute to successful host colonization.

Alterations in pancreatic β cell function and Trypanosoma cruzi infection: evidence from human and animal studies

The parasite Trypanosoma cruzi causes a persistent infection, Chagas disease, affecting millions of persons in endemic areas of Latin America. As a result of immigration, this disease has now been diagnosed in non-endemic areas worldwide. Although, the heart and gastrointestinal tract are the most studied, the insulin-secreting β cell of the endocrine pancreas is also a target of infection. In this review, we summarize available clinical and laboratory evidence to determine whether T. cruzi-infection-mediated changes of β cell function is likely to contribute to the development of hyperglycemia and diabetes. Our literature survey indicates that T. cruzi infection of humans and of experimental animals relates to altered secretory behavior of β cells. The mechanistic basis of these observations appears to be a change in stimulus-secretion pathway function rather than the loss of insulin-producing β cells. Whether this attenuated insulin release ultimately contributes to the pathogenesis of diabetes in human Chagas disease, however, remains to be determined. Since the etiologies of diabetes are multifactorial including genetic and lifestyle factors, the use of cell- and animal-based investigations, allowing direct manipulation of these factors, are important tools in testing if reduced insulin secretion has a causal influence on diabetes in the setting of Chagas disease. Long-term clinical investigations will be required to investigate this link in humans.

Adipose Tissue: A Safe Haven for Parasites?

Adipose tissue (AT) is no longer regarded as an inert lipid storage, but as an important central regulator in energy homeostasis and immunity. Three parasite species are uniquely associated with AT during part of their life cycle: Trypanosoma cruzi, the causative agent of Chagas disease; Trypanosoma brucei, the causative agent of African sleeping sickness; and Plasmodium spp., the causative agents of malaria. In AT, T. cruzi resides inside adipocytes, T. brucei is found in the interstitial spaces between adipocytes, while Plasmodium spp. infect red blood cells, which may adhere to the blood vessels supplying AT. Here, we discuss how each parasite species adapts to this tissue environment and what the implications are for pathogenesis, clinical manifestations, and therapy.

Antagonistic effect of atorvastatin on high fat diet induced survival during acute Chagas disease

Chagasic cardiomyopathy, which is seen in Chagas disease, is the most severe and life-threatening manifestation of infection by the kinetoplastid Trypanosoma cruzi. Adipose tissue and diet play a major role in maintaining lipid homeostasis and regulating cardiac pathogenesis during the development of Chagas cardiomyopathy. We have previously reported that T. cruzi has a high affinity for lipoproteins and that the invasion rate of this parasite increases in the presence of cholesterol, suggesting that drugs that inhibit cholesterol synthesis, such as statins, could affect infection and the development of Chagasic cardiomyopathy. The dual epidemic of diabetes and obesity in Latin America, the endemic regions for Chagas disease, has led to many patients in the endemic region of infection having hyperlipidemia that is being treated with statins such as atorvastatin. The current study was performed to examine mice fed on either regular or high fat diet for effects of atorvastatin on T. cruzi infection-induced myocarditis and to evaluate the effect of this treatment during infection on adipose tissue physiology and cardiac pathology. Atorvastatin was found to regulate lipolysis and cardiac lipidopathy during acute T. cruzi infection in mice and to enhance tissue parasite load, cardiac LDL levels, inflammation, and mortality in during acute infection. Overall, these data suggest that statins, such as atorvastatin, have deleterious effects during acute Chagas disease.

Fish oil supplementation attenuates changes in plasma lipids caused by dexamethasone treatment in rats

Dexamethasone is an anti-inflammatory glucocorticoid that may alter glucose and lipid homeostasis when administered in high doses or for long periods of time. Omega-3 fatty acids, present in fish oil (FO), can be used as potential modulators of intermediary glucose and lipid metabolism. Herein, we evaluate the effects of FO supplementation (1 g·kg(-1) body weight (BW)) on glucose and lipid metabolism in rats treated with dexamethasone (0.5 mg·kg(-1) BW) for 15 days. Adult male Wistar rats were distributed among 4 groups: control (saline, 1 mL·kg(-1) BW and mineral oil, 1 g·kg(-1) BW), DEX (dexamethasone and mineral oil), FO (fish oil and saline), and DFO (fish oil and dexamethasone). Dexamethasone and saline were administered intraperitoneally, and fish oil and mineral oil were administered by gavage. We evaluated functional and molecular parameters of lipid and glycemic profiles at 8 days and at the end of treatment. FO supplementation increased hepatic docosahexaenoic acid (DEX: 5.6% ± 0.7%; DFO: 10.5% ± 0.8%) and eicosapentaenoic acid (DEX: 0.3% ± 0.0%; DFO: 1.3% ± 0.1%) contents and attenuated the increase of plasma triacylglycerol, total cholesterol, and non-high-density lipoprotein cholesterol concentrations in DFO rats compared with DEX rats. These effects seem not to depend on hepatic expression of insulin receptor substrate 1, protein kinase B, peroxisome proliferator-activated receptor γ coactivator 1-α, and peroxisome proliferator-activated receptor γ. There was no effect of supplementation on body weight loss, fasting glycemia, and glucose tolerance in rats treated with dexamethasone. In conclusion, we show that FO supplementation for 15 days attenuates the dyslipidemia induced by dexamethasone treatment.

Dysregulation of Autonomic Nervous System in Chagas' Heart Disease Is Associated with Altered Adipocytokines Levels

BACKGROUND

Chagas disease (CD) induces autonomic dysfunction and inflammatory activity, which may promote metabolic abnormalities. We studied metabolism and his correlation with Autonomic Nervous System (ANS) and inflammation in CD.

METHODS AND RESULTS

Sixty subjects were divided into 4 groups: control group (CG), IF (indeterminate form) group; ECG group (ECG abnormalities and normal left ventricular systolic function), and LVD group (left ventricular sistolic dysfunction). Levels of adiponectin, leptin, insulin, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) were assayed in serum samples by ELISA. ANS was assessed by heart rate variability in frequency domain in 24-hour Holter and postural tilt test (rest and orthostatic position). High frequency (HFr) component values were used to estimate parasympathetic activity and low frequency (LFr) component, sympathetic activity. Analyzes were made of the correlations of each of the metabolic parameters (leptin and adiponectin) with the inflammatory cytokines (interleukin-6 and TNF- alpha) and with the ANS assessment measurements. No significant differences were observed in leptin and insulin levels. Adiponectin was higher in ECG and LVD groups: [CG = 4766.5 (5529.5), IF = 4003.5 (2482.5), ECG = 8376.5 (8388.5), LVD = 8798 (4188.0) ng/mL, p<0.001)]. IL-6 and TNF-alpha were higher in LVD group: [IL-6: CG = 1.85 (6.41); IF = 1.58 (1.91); ECG = 1.0 (1.57); LVD= 31.44 (72.19) pg/ml; p = 0.001. TNF-alpha: CG = 22.57 (88.2); IF = 19.31 (33.16); ECG = 12.45 (3.07); LVD = 75.15 (278.57) pg/ml; p = 0.04]. Adiponectin levels had a positive association with the HFr component (r = 0.539; p = 0.038) and an inverse association with the LFr component (r = - 0.539; p = 0.038) in ECG group. Leptin levels had a negative association with the HFr component (r= - 0.632; p = 0.011) and a positive association with the LFr component (r = 0.632; p = 0.011) in LVD group.

CONCLUSIONS

We found increased adiponectin levels in Chagas' heart disease with systolic dysfunction and in patients with ECG abnormalities and normal systolic function at rest. Adipocytokines levels (adiponectin and leptin) were associated with ANS parameters in Chagas' heart disease.

The brighter (and evolutionarily older) face of the metabolic syndrome: evidence from Trypanosoma cruzi infection in CD-1 mice

BACKGROUND

Infection with Trypanosoma cruzi, the protozoan parasite that causes Chagas disease, results in chronic infection that leads to cardiomyopathy with increased mortality and morbidity in endemic regions. In a companion study, our group found that a high-fat diet (HFD) protected mice from T. cruzi-induced myocardial damage and significantly reduced post-infection mortality during acute T. cruzi infection.

METHODS

In the present study metabolic syndrome was induced prior to T. cruzi infection by feeding a high fat diet. Also, mice were treated with anti-diabetic drug metformin.

RESULTS

In the present study, the lethality of T. cruzi (Brazil strain) infection in CD-1 mice was reduced from 55% to 20% by an 8-week pre-feeding of an HFD to induce obesity and metabolic syndrome. The addition of metformin reduced mortality to 3%.

CONCLUSIONS

It is an interesting observation that both the high fat diet and the metformin, which are known to differentially attenuate host metabolism, effectively modified mortality in T. cruzi-infected mice. In humans, the metabolic syndrome, as presently construed, produces immune activation and metabolic alterations that promote complications of obesity and diseases of later life, such as myocardial infarction, stroke, diabetes, Alzheimer's disease and cancer. Using an evolutionary approach, we hypothesized that for millions of years, the channeling of host resources into immune defences starting early in life ameliorated the effects of infectious diseases, especially chronic infections, such as tuberculosis and Chagas disease. In economically developed countries in recent times, with control of the common devastating infections, epidemic obesity and lengthening of lifespan, the dwindling benefits of the immune activation in the first half of life have been overshadowed by the explosion of the syndrome's negative effects in later life.

The cell biology of fat expansion

Adipose tissue is a complex, multicellular organ that profoundly influences the function of nearly all other organ systems through its diverse metabolite and adipokine secretome. Adipocytes are the primary cell type of adipose tissue and play a key role in maintaining energy homeostasis. The efficiency with which adipose tissue responds to whole-body energetic demands reflects the ability of adipocytes to adapt to an altered nutrient environment, and has profound systemic implications. Deciphering adipocyte cell biology is an important component of understanding how the aberrant physiology of expanding adipose tissue contributes to the metabolic dysregulation associated with obesity.

Trypanosoma cruzi infection is a potent risk factor for non-alcoholic steatohepatitis enhancing local and systemic inflammation associated with strong oxidative stress and metabolic disorders

BACKGROUND

The immune mechanisms underlying experimental non-alcoholic steatohepatitis (NASH), and more interestingly, the effect of T. cruzi chronic infection on the pathogenesis of this metabolic disorder are not completely understood.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated immunological parameters in male C57BL/6 wild type and TLR4 deficient mice fed with a standard, low fat diet, LFD (3% fat) as control group, or a medium fat diet, MFD (14% fat) in order to induce NASH, or mice infected intraperitoneally with 100 blood-derived trypomastigotes of Tulahuen strain and also fed with LFD (I+LFD) or MFD (I+MFD) for 24 weeks. We demonstrated that MFD by itself was able to induce NASH in WT mice and that parasitic infection induced marked metabolic changes with reduction of body weight and steatosis revealed by histological studies. The I+MFD group also improved insulin resistance, demonstrated by homeostasis model assessment of insulin resistance (HOMA-IR) analysis; although parasitic infection increased the triglycerides and cholesterol plasma levels. In addition, hepatic M1 inflammatory macrophages and cytotoxic T cells showed intracellular inflammatory cytokines which were associated with high levels of IL6, IFNγ and IL17 plasmatic cytokines and CCL2 chemokine. These findings correlated with an increase in hepatic parasite load in I+MFD group demonstrated by qPCR assays. The recruitment of hepatic B lymphocytes, NK and dendritic cells was enhanced by MFD, and it was intensified by parasitic infection. These results were TLR4 signaling dependent. Flow cytometry and confocal microscopy analysis demonstrated that the reactive oxygen species and peroxinitrites produced by liver inflammatory leukocytes of MFD group were also exacerbated by parasitic infection in our NASH model.

CONCLUSIONS

We highlight that a medium fat diet by itself is able to induce steatohepatitis. Our results also suggest a synergic effect between damage associated with molecular patterns generated during NASH and parasitic infection, revealing an intense cross-talk between metabolically active tissues, such as the liver, and the immune system. Thus, T. cruzi infection must be considered as an additional risk factor since exacerbates the inflammation and accelerates the development of hepatic injury.

JNK and IKKβ phosphorylation is reduced by glucocorticoids in adipose tissue from insulin-resistant rats

OBJECTIVES

Peripheral insulin resistance (IR) is one of the main side effects caused by glucocorticoid (GC)-based therapies, and the molecular mechanisms of GC-induced IR are not yet fully elucidated. Thus, we aimed to investigate the effects of dexamethasone treatment on the main components of insulin and inflammatory signaling in the adipose tissue of rats.

MATERIALS/METHODS

Male Wistar rats received daily injections of dexamethasone (1mg/kg body weight (b.w.), intraperitoneally (i.p.)) for 5 days (DEX), whereas control rats received saline (CTL). The metabolic status was investigated, and the epididymal fat fragments were collected for lipolysis and western blot analyses.

RESULTS

The DEX rats became hyperglycemic, hyperinsulinemic, insulin resistant and glucose intolerant, compared with the CTL rats (P<0.05). The basal glycerol release in the fat fragments was 1.5-fold higher in the DEX rats (P<0.05). The phosphorylation of protein kinase B (PKB) at ser(473) decreased by 44%, whereas, the phosphorylation of insulin receptor substrate (IRS)-1 at ser(307) increased by 93% in the adipose tissue of the DEX rats after an oral bolus of glucose (P<0.05). The basal phosphorylation of c-jun-N-terminal kinase (JNK) and inhibitor of nuclear factor kappa-B (IKKβ) proteins was reduced by 46% and 58%, respectively, in the adipose tissue of the DEX rats (P<0.05). This was paralleled with a significant reduction (47%) in the glucocorticoid receptor (GR) protein content in the adipose tissue of the DEX rats (P<0.05).

CONCLUSION

The insulin-resistant status of rats induced by dexamethasone administration have PKB and IRS-1 activity attenuated in epididymal fat without increases in the phosphorylation of the proinflammatory signals JNK and IKKβ.

Markers of oxidative stress in adipose tissue during Trypanosoma cruzi infection

The protozoan parasite Trypanosoma cruzi causes Chagas disease. Cardiac and adipose tissues are among the early targets of infection and are sites of persistent infection. In the heart and adipose tissue, T. cruzi infection results in an upregulation of pro-inflammatory mediators. In the heart, infection is associated with an increase in the markers of oxidative stress. To date, markers of oxidative stress have not been evaluated in adipose tissue in this infection. Brown and white adipose tissues were obtained from CD-1 mice infected with the Brazil strain of T. cruzi for 15, 30, and 130 days post infection. Protein carbonylation and lipid peroxidation assays were performed on these samples. There was an upregulation of these markers of oxidative stress at all time-points in both white and brown adipose tissue. Determinants of anti-oxidative stress were downregulated at similar time-points. This increase in oxidative stress during T. cruzi infection most likely has a deleterious effect on host metabolism and on the heart.