Body Composition and Metabolic Caging Analysis in High Fat Fed Mice

Behavioral, metabolic, and lipidomic characterization of the 5xFADxTg30 mouse model of Alzheimer's disease

Alzheimer's disease (AD) is associated with both extracellular amyloid-β (Aβ) plaques and intracellular tau-containing neurofibrillary tangles (NFT). We characterized the behavioral, metabolic and lipidomic phenotype of the 5xFADxTg30 mouse model which contains overexpression of both Aβ and tau. Our results independently reproduce several phenotypic traits described previously for this model, while providing additional characterization. This model develops many aspects associated with AD including frailty, decreased survival, initiation of aspects of cognitive decline and alterations to specific lipid classes and molecular lipid species in the plasma and brain. Notably, some sex-specific differences exist in this model and motor impairment with aging in this model does compromise the utility of the model for some movement-based behavioral assessments of cognitive function. These findings provide a reference for individuals interested in using this model to understand the pathology associated with elevated Aβ and tau or for testing potential therapeutics for the treatment of AD.

Antibiotics administration alleviates the high fat diet-induced obesity through altering the lipid metabolism in young mice

Currently, there is a global trend of rapid increase in obesity, especially among adolescents. The antibiotics cocktails (ABX) therapy is commonly used as an adjunctive treatment for gut microbiota related diseases, including obesity. However, the effects of broad-spectrum antibiotics alone on young obese hosts have rarely been reported. In the present study, the 3-week-old C57BL/6J male mice fed a high-fat diet (HFD) were intragastric administration with ampicillin, vancomycin, metronidazole or neomycin for 30 days. The lipid metabolites in plasma were assessed by biochemical assay kits, and genes related to lipid metabolite in the white adipose were assessed by qPCR. To further analyze the underlying mechanisms, the expression of genes related to lipid metabolism, inflammatory reactions and oxidative stress in the liver were determined by qPCR assay. In addition, the expression of oxidative damage-associated proteins in the liver were detected by western blot. The results showed that oral antibiotics exposure could reduce body weight and fat index in HFD-fed mice, concurrent with the increase of white adipose lipolysis genes and the decrease of hepatic lipogenic genes. Furthermore, antibiotics treatment could clearly reverse the HFD-induced elevation of oxidative damage-related proteins in the liver. Together, these findings will provide valuable clues into the effects of antibiotics on obesity.

Anti-Obesity Effects of Combined Cornus officinalis and Ribes fasciculatum Extract in High-Fat Diet-Induced Obese Male Mice

Simple Summary

Obesity is a general health problem representing a high risk factor for a low-quality lifestyle. Various Food and Drug Administration-approved pharmacological medications have been established for the treatment and prevention of obesity. However, some pharmacotherapies present adverse effects and limited long-term use. Natural herbal medicines as alternative cures have shown low side-effects and suitability for long-term treatment. Cornus officinalis and Ribes fasciculatum (CR) are well-known oriental plants used for health dietary supplements and herbal medicine. This study examined the anti-obesity effect of CR in high-fat diet (HFD)-induced obese male mice. Treatment of CR extract prevented body weight gain through the downregulation of adipogenic inducible genes and recovered the dysregulated energy metabolism in HFD-induced obese male mice. Therefore, CR reduced elevated biochemical obesity parameters in plasma, as well as inhibited hepatic steatosis in the liver and adipocyte size increase in fat tissue. These findings of the study reveal the potential anti-obesity effects of CR as an herbal medicine.

Abstract

Medicinal plants are widely used as supplements for the treatment of various diseases because of their few side-effects. Here, we examined the anti-obesity effects of a mixture extract of Cornus officinalis and Ribes fasciculatum (CR) in high-fat diet (HFD)-induced obese male mice. Four week old male C57BL/6J mice were fed a normal diet (ND) or 60% high-fat diet (HFD) with different concentrations of CR extracts (75, 150, and 300 mg/kg/day) by oral administration for 12 weeks. CR extract administration prevented HFD-induced weight gain, hepatic steatosis, and adipocyte enlargement through the downregulation of adipogenesis-associated genes in obese male mice. In addition, CR administration improved the impaired glucose metabolism, insulin action, biochemical obesity parameters, and metabolic profiles in HFD-induced male mice. Consequently, the CR extract exhibited beneficial effects on HFD-induced systemic metabolic challenges. Taken together, our findings suggest that CR extract may be a potent therapeutic supplement for the treatment and prevention of obesity.

Mesenteric lymphatic dysfunction promotes insulin resistance and represents a potential treatment target in obesity

Visceral adipose tissue (VAT) encases mesenteric lymphatic vessels and lymph nodes through which lymph is transported from the intestine and mesentery. Whether mesenteric lymphatics contribute to adipose tissue inflammation and metabolism and insulin resistance is unclear. Here we show that obesity is associated with profound and progressive dysfunction of the mesenteric lymphatic system in mice and humans. We find that lymph from mice and humans consuming a high-fat diet (HFD) stimulates lymphatic vessel growth, leading to the formation of highly branched mesenteric lymphatic vessels that 'leak' HFD-lymph into VAT and, thereby, promote insulin resistance. Mesenteric lymphatic dysfunction is regulated by cyclooxygenase (COX)-2 and vascular endothelial growth factor (VEGF)-C-VEGF receptor (R)3 signalling. Lymph-targeted inhibition of COX-2 using a glyceride prodrug approach reverses mesenteric lymphatic dysfunction, visceral obesity and inflammation and restores glycaemic control in mice. Targeting obesity-associated mesenteric lymphatic dysfunction thus represents a potential therapeutic option to treat metabolic disease.

Single or combined ablation of peripheral serotonin and p21 limit adipose tissue expansion and metabolic alterations in early adulthood in mice fed a normocaloric diet

Identifying the fundamental molecular factors that drive weight gain even in the absence of hypercaloric food intake, is crucial to enable development of novel treatments for the global pandemic of obesity. Here we investigated both adipose tissue-specific and systemic events that underlie the physiological weight gain occurring during early adulthood in mice fed a normocaloric diet. In addition, we used three different genetic models to identify molecular factors that promote physiological weight gain during normocaloric and hypercaloric diets. We demonstrated that normal physiological weight gain was accompanied by an increase in adipose tissue mass and the presence of cellular and metabolic signatures typically found during obesity, including adipocyte hypertrophy, macrophage recruitment into visceral fat and perturbed glucose metabolism. At the molecular level, this was associated with an increase in adipose tissue tryptophan hydroxylase 1 (Tph1) transcripts, the key enzyme responsible for the synthesis of peripheral serotonin. Genetic inactivation of Tph1 was sufficient to limit adipose tissue expansion and associated metabolic alterations. Mechanistically, we discovered that Tph1 inactivation resulted in down-regulation of cyclin-dependent kinase inhibitor p21Waf1/Cip1 expression. Single or double ablation of Tph1 and p21 were equally effective in preventing adipocyte expansion and systemic perturbation of glucose metabolism, upon both normocaloric and hypercaloric diets. Our results suggest that serotonin and p21 act as a central molecular determinant of weight gain and associated metabolic alterations, and highlights the potential of targeting these molecules as a pharmacologic approach to prevent the development of obesity.

Yap regulates skeletal muscle fatty acid oxidation and adiposity in metabolic disease

Obesity is a major risk factor underlying the development of metabolic disease and a growing public health concern globally. Strategies to promote skeletal muscle metabolism can be effective to limit the progression of metabolic disease. Here, we demonstrate that the levels of the Hippo pathway transcriptional co-activator YAP are decreased in muscle biopsies from obese, insulin-resistant humans and mice. Targeted disruption of Yap in adult skeletal muscle resulted in incomplete oxidation of fatty acids and lipotoxicity. Integrated 'omics analysis from isolated adult muscle nuclei revealed that Yap regulates a transcriptional profile associated with metabolic substrate utilisation. In line with these findings, increasing Yap abundance in the striated muscle of obese (db/db) mice enhanced energy expenditure and attenuated adiposity. Our results demonstrate a vital role for Yap as a mediator of skeletal muscle metabolism. Strategies to enhance Yap activity in skeletal muscle warrant consideration as part of comprehensive approaches to treat metabolic disease.

Targeting Methylglyoxal in Diabetic Kidney Disease Using the Mitochondria-Targeted Compound MitoGamide

Diabetic kidney disease (DKD) remains the number one cause of end-stage renal disease in the western world. In experimental diabetes, mitochondrial dysfunction in the kidney precedes the development of DKD. Reactive 1,2-dicarbonyl compounds, such as methylglyoxal, are generated from sugars both endogenously during diabetes and exogenously during food processing. Methylglyoxal is thought to impair the mitochondrial function and may contribute to the pathogenesis of DKD. Here, we sought to target methylglyoxal within the mitochondria using MitoGamide, a mitochondria-targeted dicarbonyl scavenger, in an experimental model of diabetes. Male 6-week-old heterozygous Akita mice (C57BL/6-Ins2-Akita/J) or wildtype littermates were randomized to receive MitoGamide (10 mg/kg/day) or a vehicle by oral gavage for 16 weeks. MitoGamide did not alter the blood glucose control or body composition. Akita mice exhibited hallmarks of DKD including albuminuria, hyperfiltration, glomerulosclerosis, and renal fibrosis, however, after 16 weeks of treatment, MitoGamide did not substantially improve the renal phenotype. Complex-I-linked mitochondrial respiration was increased in the kidney of Akita mice which was unaffected by MitoGamide. Exploratory studies using transcriptomics identified that MitoGamide induced changes to olfactory signaling, immune system, respiratory electron transport, and post-translational protein modification pathways. These findings indicate that targeting methylglyoxal within the mitochondria using MitoGamide is not a valid therapeutic approach for DKD and that other mitochondrial targets or processes upstream should be the focus of therapy.

Characterization of the circulating and tissue-specific alterations to the lipidome in response to moderate and major cold stress in mice

This study analyzed the effects of 24 h of cold stress (22°C or 5°C vs. mice maintained at 30 °C) on the plasma, brown adipose tissue (BAT), subcutaneous (SubQ) and epididymal (Epi) white adipose tissue (WAT), liver, and skeletal muscle lipidome of mice. Using mass spectrometry-lipidomics, 624 lipid species were detected, of which 239 were significantly altered in plasma, 134 in BAT, and 51 in the liver. In plasma, acylcarnitines and free fatty acids were markedly increased at 5°C. Plasma triacylglycerols (TGs) were reduced at 22°C and 5°C. We also identified ether lipids as a novel, cold-induced lipid class. In BAT, TGs were the principal lipid class affected by cold stress, being significantly reduced at both 22°C and 5°C. Interestingly, although BAT TG species were uniformly affected at 5°C, at 22°C we observed species-dependent effects, with TGs containing longer and more unsaturated fatty acids particularly sensitive to the effects of cold. In the liver, TGs were the most markedly affected lipid class, increasing in abundance at 5 °C. TGs containing longer and more unsaturated fatty acids accumulated to a greater degree. Our work demonstrates the following: 1) acute exposure to moderate (22°C) cold stress alters the plasma and BAT lipidome; although this effect is markedly less pronounced than at 5°C. 2) Cold stress at 5°C dramatically alters the plasma lipidome, with ether lipids identified as a novel lipid class altered by cold exposure. 3) Cold-induced alterations in liver and BAT TG levels are not uniform, with changes being influenced by acyl chain composition.

Deletion of Trim28 in committed adipocytes promotes obesity but preserves glucose tolerance

The effective storage of lipids in white adipose tissue (WAT) critically impacts whole body energy homeostasis. Many genes have been implicated in WAT lipid metabolism, including tripartite motif containing 28 (Trim28), a gene proposed to primarily influence adiposity via epigenetic mechanisms in embryonic development. However, in the current study we demonstrate that mice with deletion of Trim28 specifically in committed adipocytes, also develop obesity similar to global Trim28 deletion models, highlighting a post-developmental role for Trim28. These effects were exacerbated in female mice, contributing to the growing notion that Trim28 is a sex-specific regulator of obesity. Mechanistically, this phenotype involves alterations in lipolysis and triglyceride metabolism, explained in part by loss of Klf14 expression, a gene previously demonstrated to modulate adipocyte size and body composition in a sex-specific manner. Thus, these findings provide evidence that Trim28 is a bona fide, sex specific regulator of post-developmental adiposity and WAT function.

Fecal microbiota transplantation from high caloric-fed donors alters glucose metabolism in recipient mice, independently of adiposity or exercise status

Studies suggest the gut microbiota contributes to the development of obesity and metabolic syndrome. Exercise alters microbiota composition and diversity and is protective of these maladies. We tested whether the protective metabolic effects of exercise are mediated through fecal components through assessment of body composition and metabolism in recipients of fecal microbiota transplantation (FMT) from exercise-trained (ET) mice fed normal or high-energy diets. Donor C57BL/6J mice were fed a chow or high-fat, high-sucrose diet (HFHS) for 4 wk to induce obesity and glucose intolerance. Mice were divided into sedentary (Sed) or ET groups (6 wk treadmill-based ET) while maintaining their diets, resulting in four donor groups: chow sedentary (NC-Sed) or ET (NC-ET) and HFHS sedentary (HFHS-Sed) or ET (HFHS-ET). Chow-fed recipient mice were gavaged with feces from the respective donor groups weekly, creating four groups (NC-Sed-R, NC-ET-R, HFHS-Sed-R, HFHS-ET-R), and body composition and metabolism were assessed. The HFHS diet led to glucose intolerance and obesity in the donors, whereas exercise training (ET) restrained adiposity and improved glucose tolerance. No donor group FMT altered recipient body composition. Despite unaltered adiposity, glucose levels were disrupted when challenged in mice receiving feces from HFHS-fed donors, irrespective of donor-ET status, with a decrease in insulin-stimulated glucose clearance into white adipose tissue and large intestine and specific changes in the recipient's microbiota composition observed. FMT can transmit HFHS-induced disrupted glucose metabolism to recipient mice independently of any change in adiposity. However, the protective metabolic effect of ET on glucose metabolism is not mediated through fecal factors.

Sex-specific adipose tissue imprinting of regulatory T cells

Adipose tissue is an energy store and a dynamic endocrine organ1,2. In particular, visceral adipose tissue (VAT) is critical for the regulation of systemic metabolism3,4. Impaired VAT function-for example, in obesity-is associated with insulin resistance and type 2 diabetes5,6. Regulatory T (Treg) cells that express the transcription factor FOXP3 are critical for limiting immune responses and suppressing tissue inflammation, including in the VAT7-9. Here we uncover pronounced sexual dimorphism in Treg cells in the VAT. Male VAT was enriched for Treg cells compared with female VAT, and Treg cells from male VAT were markedly different from their female counterparts in phenotype, transcriptional landscape and chromatin accessibility. Heightened inflammation in the male VAT facilitated the recruitment of Treg cells via the CCL2-CCR2 axis. Androgen regulated the differentiation of a unique IL-33-producing stromal cell population specific to the male VAT, which paralleled the local expansion of Treg cells. Sex hormones also regulated VAT inflammation, which shaped the transcriptional landscape of VAT-resident Treg cells in a BLIMP1 transcription factor-dependent manner. Overall, we find that sex-specific differences in Treg cells from VAT are determined by the tissue niche in a sex-hormone-dependent manner to limit adipose tissue inflammation.

Exploring the role of the metabolite-sensing receptor GPR109a in diabetic nephropathy

Alterations in gut homeostasis may contribute to the progression of diabetic nephropathy. There has been recent attention on the renoprotective effects of metabolite-sensing receptors in chronic renal injury, including the G protein-coupled receptor (GPR)109a, which ligates the short-chain fatty acid butyrate. However, the role of GPR109a in the development of diabetic nephropathy, a milieu of diminished microbiome-derived metabolites, has not yet been determined. The present study aimed to assess the effects of insufficient GPR109a signaling, via genetic deletion of GPR109a, on the development of renal injury in diabetic nephropathy. Gpr109a^-/- mice or their wild-type littermates (Gpr109a^+/+) were rendered diabetic with streptozotocin. Mice received a control diet or an isocaloric high-fiber diet (12.5% resistant starch) for 24 wk, and gastrointestinal permeability and renal injury were determined. Diabetes was associated with increased albuminuria, glomerulosclerosis, and inflammation. In comparison, Gpr109a^-/- mice with diabetes did not show an altered renal phenotype. Resistant starch supplementation did not afford protection from renal injury in diabetic nephropathy. While diabetes was associated with alterations in intestinal morphology, intestinal permeability assessed in vivo using the FITC-dextran test was unaltered. GPR109a deletion did not worsen gastrointestinal permeability. Furthermore, 12.5% resistant starch supplementation, at physiological concentrations, had no effect on intestinal permeability or morphology. The results of this study indicate that GPR109a does not play a critical role in intestinal homeostasis in a model of type 1 diabetes or in the development of diabetic nephropathy.

Delineating a role for the mitochondrial permeability transition pore in diabetic kidney disease by targeting cyclophilin D

Mitochondrial stress has been widely observed in diabetic kidney disease (DKD). Cyclophilin D (CypD) is a functional component of the mitochondrial permeability transition pore (mPTP) which allows the exchange of ions and solutes between the mitochondrial matrix to induce mitochondrial swelling and activation of cell death pathways. CypD has been successfully targeted in other disease contexts to improve mitochondrial function and reduced pathology. Two approaches were used to elucidate the role of CypD and the mPTP in DKD. Firstly, mice with a deletion of the gene encoding CypD (Ppif-/-) were rendered diabetic with streptozotocin (STZ) and followed for 24 weeks. Secondly, Alisporivir, a CypD inhibitor was administered to the db/db mouse model (5 mg/kg/day oral gavage for 16 weeks). Ppif-/- mice were not protected against diabetes-induced albuminuria and had greater glomerulosclerosis than their WT diabetic littermates. Renal hyperfiltration was lower in diabetic Ppif-/- as compared with WT mice. Similarly, Alisporivir did not improve renal function nor pathology in db/db mice as assessed by no change in albuminuria, KIM-1 excretion and glomerulosclerosis. Db/db mice exhibited changes in mitochondrial function, including elevated respiratory control ratio (RCR), reduced mitochondrial H2O2 generation and increased proximal tubular mitochondrial volume, but these were unaffected by Alisporivir treatment. Taken together, these studies indicate that CypD has a complex role in DKD and direct targeting of this component of the mPTP will likely not improve renal outcomes.

The Antioxidant Moiety of MitoQ Imparts Minimal Metabolic Effects in Adipose Tissue of High Fat Fed Mice

Mitochondrial dysfunction is associated with a diverse array of diseases ranging from dystrophy and heart failure to obesity and hepatosteatosis. One of the major biochemical consequences of impaired mitochondrial function is an accumulation of mitochondrial superoxide, or reactive oxygen species (ROS). Excessive ROS can be detrimental to cellular health and is proposed to underpin many mitochondrial diseases. Accordingly, much research has been committed to understanding ways to therapeutically prevent and reduce ROS accumulation. In white adipose tissue (WAT), ROS is associated with obesity and its subsequent complications, and thus reducing mitochondrial ROS may represent a novel strategy for treating obesity related disorders. One therapeutic approach employed to reduce ROS abundance is the mitochondrial-targeted coenzyme Q (MitoQ), which enables mitochondrial specific delivery of a CoQ10 antioxidant via its triphenylphosphonium bromide (TPP+) cation. Indeed, MitoQ has been successfully shown to accumulate at the outer mitochondrial membrane and prevent ROS accumulation in several tissues in vivo; however, the specific effects of MitoQ on adipose tissue metabolism in vivo have not been studied. Here we demonstrate that mice fed high-fat diet with concomitant administration of MitoQ, exhibit minimal metabolic benefit in adipose tissue. We also demonstrate that both MitoQ and its control agent dTPP+ had significant and equivalent effects on whole-body metabolism, suggesting that the dTPP+ cation rather than the antioxidant moiety, was responsible for these changes. These findings have important implications for future studies using MitoQ and other TPP+ compounds.