Mechanisms by Which Obesity Promotes Acute Graft-Versus-Host Disease in Mice

The efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is limited by the occurrence of acute and chronic graft-versus-host disease (GVHD). We have recently demonstrated that obesity results in exacerbated acute gastrointestinal GVHD in both mouse models and clinical outcomes due to increased pro-inflammatory cytokine responses and microbiota alterations. We therefore wanted to delineate the role of the various parameters in obesity, adiposity, effects of high-fat (HF) diet, and the role of microbiome on GVHD pathogenesis, by taking advantage of a mouse strain resistant to diet-induced obesity (DIO). Female BALB/c mice are resistant to DIO phenotype with approximately 50% becoming DIO under HF diets. The DIO-susceptible recipients rapidly succumb to acute gut GVHD, whereas the DIO-resistant recipient littermates, which do not become obese, are partially protected from GVHD, indicating that being on HF diet alone contributes to but is not the primary driver of GVHD. Microbiome assessment revealed restricted diversity in both cohorts of mice, but coprophagy normalizes the microbiota in mice housed together. We then individually housed DIO-resistant, DIO-susceptible, and lean control mice. Notably, each of the individually housed groups demonstrates marked restricted diversity that has been shown to occur from the stress of single housing. Despite the restricted microbiome diversity, the GVHD pathogenesis profile remains consistent in the group-housed mice, with the lean control single-housed mice exhibiting no acute GVHD and DIO-resistant recipients showing again partial protection. These results demonstrate that the deleterious effects of obesity on acute gut GVHD are critically dependent on adiposity with the HF diet also playing a lesser role, and the microbiome alterations with obesity instead appear to fuel ongoing acute GVHD processes.

Deletion of RAGE fails to prevent hepatosteatosis in obese mice due to impairment of other AGEs receptors and detoxifying systems

Advanced glycation endproducts (AGEs) are involved in several diseases, including NAFLD and NASH. RAGE is the main receptor mediating the pro-inflammatory signalling induced by AGEs. Therefore, targeting of RAGE has been proposed for prevention of chronic inflammatory diseases. However, the role of RAGE in the development of NAFLD and NASH remains poorly understood. We thus aimed to analyse the effect of obesity on AGEs accumulation, AGE-receptors and AGE-detoxification, and whether the absence of RAGE might improve hepatosteatosis and inflammation, by comparing the liver of lean control, obese (LeptrDb−/−) and obese RAGE-deficient (RAGE−/− LeptrDb−/−) mice. Obesity induced AGEs accumulation and RAGE expression with hepatosteatosis and inflammation in LeptrDb−/−, compared to lean controls. Despite the genetic deletion of RAGE in the LeptrDb−/− mice, high levels of intrahepatic AGEs were maintained accompanied by decreased expression of the protective AGE-receptor-1, impaired AGE-detoxifying system glyoxalase-1, and increased expression of the alternative AGE-receptor galectin-3. We also found sustained hepatosteatosis and inflammation as determined by persistent activation of the lipogenic SREBP1c and proinflammatory NLRP3 signalling pathways. Thus, RAGE targeting is not effective in the prevention of NAFLD in conditions of obesity, likely due to the direct liver specific crosstalk of RAGE with other AGE-receptors and AGE-detoxifying systems.

Adenovirus transduction to express human ACE2 causes obesity-specific morbidity in mice, impeding studies on the effect of host nutritional status on SARS-CoV-2 pathogenesis.

The COVID-19 pandemic has paralyzed the global economy and resulted in millions of deaths globally. People with co-morbidities like obesity, diabetes and hypertension are at an increased risk for severe COVID-19 illness. This is of overwhelming concern because 42% of Americans are obese, 30% are pre-diabetic and 9.4% have clinical diabetes. Here, we investigated the effect of obesity on disease severity following SARS-CoV-2 infection using a well-established mouse model of diet-induced obesity. Diet-induced obese and lean control C57BL/6N mice, transduced for ACE2 expression using replication-defective adenovirus, were infected with SARS-CoV-2, and monitored for lung pathology, viral titers, and cytokine expression. No significant differences in tissue pathology, viral replication or cytokine expression were observed between lean and obese groups. Notably, significant weight loss was observed in obese mice treated with the adenovirus vector, independent of SARS-CoV-2 infection, suggesting an obesity-dependent morbidity induced by the vector. These data indicate that the adenovirus-transduced mouse model of SARS-CoV-2 infection is inadequate for performing nutrition studies, and caution should be used when interpreting resulting data.

Renal lipid accumulation, oxidative stress and uric acid handling in a rodent model of obesity and metabolic syndrome

Hyperuricemia is more prevalent among people with obesity and metabolic syndrome, and is associated with adverse clinical outcomes. We hypothesized that increased renal reabsorption of uric acid (UA) in obesity and metabolic syndrome may be an adaptive response of the kidney when faced with fatty acid-induced oxidative stress. To test this hypothesis, we examined lipid accumulation, markers of oxidative stress, and renal UA handling in Zucker diabetic fatty (ZDF) rats, and in matched lean control animals. Rats were randomized to either normal rodent chow or a diet supplemented with antioxidants (α-tocopheryl acetate, sodium selenite, zinc sulfate, and ascorbic acid), and were followed up for either 4 or 20 weeks after randomization. Dietary antioxidant supplementation had no significant effects in lean control rats but led to partial improvement in markers of elevated oxidative stress in the kidney of ZDF rats. Renal UA handling was not affected by antioxidant supplementation. We observed robust correlations between renal lipid content and oxidative stress markers in the pooled experimental groups, particularly in older animals after 20 weeks on the study diets. Dietary antioxidant supplementation did not prevent the gradual decline in renal function observed in older ZDF rats. These findings suggest that hyperuricemia in the ZDF rat model of obesity and the metabolic syndrome is not caused by renal oxidative stress, that there may be a pathophysiological link between lipid accumulation and oxidative stress in the kidney, and that antioxidant supplementation does not prevent age-related decline in renal function in ZDF rats.

11-Oxygenated C19 Steroids Do Not Distinguish the Hyperandrogenic Phenotype of PCOS Daughters from Girls with Obesity

Context Hyperandrogenemia (HA) is a consistent reproductive phenotype in women with polycystic ovary syndrome (PCOS) and their relatives. Increased testosterone levels are present in premenarchal daughters of affected women (PCOS-d). Obese girls (OB-g) without a family history of PCOS also have peripubertal HA. The sources and significance of HA in these groups remains unknown. Objective 11-oxygenated 19-carbon (C19) steroids are adrenally derived androgens that are elevated in hyperandrogenic disorders, including PCOS. We performed this study to test the hypothesis that peripheral serum 11-oxygenated steroids would differ in PCOS-d compared with OB-g suggesting distinct etiologies of HA in affected girls. Design, Setting, and Participants We compared peripheral serum 11-oxygenated steroid levels in 21 PCOS-d, 29 OB-g, and 17 lean control girls (LC) of comparable age at an academic medical center. Results Body mass index (BMI) differed by design (P < 0.001). 11β-hydroxyandrostenedione, 11-ketoandrostenedione, and 11β-hydroxytestosterone levels did not differ between the groups. Compared with LC, PCOS-d and OB-g had similar elevations in 11-ketotestosterone (11KT) (analysis of variance [ANOVA] P = 0.03; PCOS-d vs LC, P = 0.04; OB-g vs LC, P = 0.05; PCOS-d vs OB-g, P = 0.97). In multivariate regression, 11KT levels were associated with DHEAS (P = 0.008), but not with BMI z score, breast Tanner stage, testosterone, anti-Müllerian hormone or sex hormone–binding globulin levels. Conclusions Circulating 11KT levels were similarly elevated in peripubertal PCOS-d and OB-g, suggesting an adrenal component of HA in both groups. We found that 11-oxygenated 19-carbon steroid profiles did not identify subtypes of HA girls.

Effect of Dietary XOS Supplementation on Systemic Amino Acid Homeostasis

Objectives Systemic amino acid (AA) levels are tightly regulated. Homeostasis of certain AAs, such as branched chain AAs (BCAAs), and aromatic AAs are not only associated with impaired glucose control but also important determinants of mood. The health benefits of dietary xylooligosaccharides (XOS) in glucose control have been published. In addition, XOS consumption was reported to increase participant-reported vitality and happiness. Therefore, we hypothesized that dietary XOS supplementation induce changes of AA homeostasis, which contributes to its metabolic and mood benefit. Methods Male db/db BSK mice and their respective lean control db/m BSK mice were used in this study. Mice at age 7 wk were randomized into three groups and fed AIN93M, AIN93M + 2%−, or 7%-XOS (w/w) for 8 weeks (n = 8–10/group). At the end of the intervention, fasting serum samples were collected and processed for glucose, insulin, AA analysis. Results db/db mice developed obesity, hyperglycemia and hyperinsulinemia compared to db/m mice. We did not detect difference in serum BCAAs and aromatic AAs, including phenylalanine (phe), tryptophan (Trp) and tyrosine (Tyr) between db/db and db/m mice. Serum arginine (Arg), proline (Pro) and methionine (Met) were significantly lower in db/db compared db/m. Dietary XOS supplementation (2 and 7%) did not change body weight and fat depots in db/m and db/db mice. Fasting blood glucose, Met and Pro levels were significantly reduced by 7% XOS in db/m not db/db mice. XOS did not change any other AAs in either db/db or db/m mice. Serum Trp microbial metabolites indole acetate (IAA) was significantly higher while indole propionate (IPA) was lower in db/db mice compared to db/m mice. XOS (both 2 and 7%) decreased IAA in both db/m and db/db mice, while 2% XOS increased IPA only in db/db mice. Tyr was decreased by 7% XOS in db/m mice but not db/db mice, while Tyr metabolite, p-cresol sulfate, was reduced by 2% XOS in db/db mice only. Conclusions Our data indicate interactions between dietary XOS and Leptin R genotype/or host metabolic status on glucose control and systemic AA homeostasis. The mechanism of how dietary XOS intake modulate AA homeostasis needs further investigation. Funding Sources This project was supported by NIH-R01 and Center for Human Nutrition.

SAT-LB100 Central and Peripheral Endocannabinoid Levels in Obese Versus Lean Women

The endocannabinoid system (ECS) is thought to be involved in obesity because its activation increases appetite and weight gain (Pagotto et al 2006). The ECS is hyperactivated in the hypothalamus of obese mice, and peripheral overactivation has been observed in humans; circulating 2-arachidonoyl glycerol (2-AG) levels positively correlated with body fat, visceral fat and fasting glucose (Osei-Hyiaman et al 2005) (Bluher et al 2006) (Motaghedi and McGraw 2008) (Cavuoto et al 2007) (Artmann et al 2008) (Bermudez-Silva 2009). The aim of this study was to evaluate whether differential activation of the peripheral versus the central ECS occurred in humans and to test the hypothesis that the ECS is hyperactivated in the human central nervous system (CNS).Cerebral spinal fluid (CSF) and blood samples were collected from 13 obese and 11 lean control women to measure 2-AG and anandamide (AEA) levels.AEA levels were higher in the plasma of obese women (obese: 4.03 ± 0.91 pmol/mL, N=13; lean: 1.84 ± 0.21 pmol/mL, N=10; p<0.05) but were lower in the CSF of obese women. The plasma/CSF ratio was 41.58 ± 5.78 (N=10) in lean women and 103.0 ± 37.36 (N=6) in obese women (p=0.054). There were no correlations between plasma and CSF AEA levels or with any biochemical parameter. The 2-AG analysis was not possible because of technical problems.Our data suggested that in human obesity, the peripheral ECS may be more active than the central ECS. Indeed, the system appeared to be suppressed in the CNS of obese women. Therefore, the peripheral activation of the ECS may be more relevant for obesity. Keywords: Anandamide, 2-arachidonoyl glycerol, obesity, endocannabinoid, endocannabinoid system, cb1 receptor.

Effects of long-term exposure to aluminum in the hippocampus in the type 2 diabetes model rats

We investigated the long-term effects of aluminum (Al) exposure in the hippocampus in Zucker diabetic fatty (ZDF) rats and Zucker lean control (ZLC) rats.