Physiologic and genetic evidence links hemopexin to triglycerides in mice and humans

Generational Diet-Induced Obesity Remodels the Omental Adipose Proteome in Female Mice

Obesity, a complex condition that involves genetic, environmental, and behavioral factors, is a non-infectious pandemic that affects over 650 million adults worldwide with a rapidly growing prevalence. A major contributor is the consumption of high-fat diets, an increasingly common feature of modern diets. Maternal obesity results in an increased risk of offspring developing obesity and related health problems; however, the impact of maternal diet on the adipose tissue composition of offspring has not been evaluated. Here, we designed a generational diet-induced obesity study in female C57BL/6 mice that included maternal cohorts and their female offspring fed either a control diet (10% fat) or a high-fat diet (45% fat) and examined the visceral adipose proteome. Solubilizing proteins from adipose tissue is challenging due to the need for high concentrations of detergents; however, the use of a detergent-compatible sample preparation strategy based on suspension trapping (S-Trap) enabled label-free quantitative bottom-up analysis of the adipose proteome. We identified differentially expressed proteins related to lipid metabolism, inflammatory disease, immune response, and cancer, providing valuable molecular-level insight into how maternal obesity impacts the health of offspring. Data are available via ProteomeXchange with the identifier PXD042092.

Modulation of Heme-Induced Inflammation Using MicroRNA-Loaded Liposomes: Implications for Hemolytic Disorders Such as Malaria and Sickle Cell Disease

Hemolytic disorders, like malaria and sickle cell disease (SCD), are responsible for significant mortality and morbidity rates globally, specifically in the Americas and Africa. In both malaria and SCD, red blood cell hemolysis leads to the release of a cytotoxic heme that triggers the expression of unique inflammatory profiles, which mediate the tissue damage and pathogenesis of both diseases. MicroRNAs (miRNAs), such as miR-451a and let-7i-5p, contribute to a reduction in the pro-inflammatory responses induced by circulating free hemes. MiR-451a targets both IL-6R (pro-inflammatory) and 14-3-3ζ (anti-inflammatory), and when this miRNA is present, IL-6R is reduced and 14-3-3ζ is increased. Let-7i-5p targets and reduces TLR4, which results in anti-inflammatory signaling. These gene targets regulate inflammation via NFκB regulation and increase anti-inflammatory signaling. Additionally, they indirectly regulate the expression of key heme scavengers, such as heme-oxygenase 1 (HO-1) (coded by the HMOX1 gene) and hemopexin, to decrease circulating cytotoxic heme concentration. MiRNAs can be transported within extracellular vesicles (EVs), such as exosomes, offering insights into the mechanisms of mitigating heme-induced inflammation. We tested the hypothesis that miR-451a- or let-7i-5p-loaded artificial EVs (liposomes) will reduce heme-induced inflammation in brain vascular endothelial cells (HBEC-5i, ATCC: CRL-3245) and macrophages (THP-1, ATCC: TIB-202) in vitro. We completed arginase and nitric oxide assays to determine anti- and pro-inflammatory macrophage presence, respectively. We also assessed the gene expression of IL-6R, TLR4, 14-3-3ζ, and NFκB by RT-qPCR for both cell lines. Our findings revealed that the exposure of HBEC-5i and THP-1 to liposomes loaded with miR-451a or let-7i-5p led to a reduced mRNA expression of IL-6R, TLR4, 14-3-3ζ, and NFκB when treated with a heme. It also resulted in the increased expression of HMOX1 and hemopexin. Finally, macrophages exhibited a tendency toward adopting an anti-inflammatory differentiation phenotype. These findings suggest that miRNA-loaded liposomes can modulate heme-induced inflammation and can be used to target specific cellular pathways, mediating inflammation common to hematological conditions, like malaria and SCD.

Gut Microbiota Remodeling and Intestinal Adaptation to Lipid Malabsorption After Enteroendocrine Cell Loss in Adult Mice

BACKGROUND & AIMS

Enteroendocrine cells (EECs) and their hormones are essential regulators of whole-body energy homeostasis. EECs sense luminal nutrients and microbial metabolites and subsequently secrete various hormones acting locally or at a distance. Impaired development of EECs during embryogenesis is life-threatening in newborn mice and humans due to compromised nutrient absorption. However, the physiological importance of the EEC system in adult mice has yet to be directedly studied. Herein, we aimed to determine the long-term consequences of a total loss of EECs in healthy adults on energy metabolism, intestinal transcriptome, and microbiota.

METHODS

We depleted intestinal EECs by tamoxifen treatment of adult Neurog3^fl/fl; Villin-CreER^T2 male mice. We studied intestinal cell differentiation, food efficiency, lipid absorption, microbiota composition, fecal metabolites, and transcriptomic responses in the proximal and distal small intestines of mice lacking EECs. We also determined the high-fat diet-induced transcriptomic changes in sorted Neurog3^eYFP/+ EECs.

RESULTS

Induction of EEC deficiency in adults is not life-threatening unless fed with a high-fat diet. Under a standard chow diet, mice lose 10% of weight due to impaired food efficiency. Blood concentrations of cholesterol, triglycerides, and free fatty acids are reduced, and lipid absorption is impaired and delayed in the distal small intestine. Genes controlling lipogenesis, carbohydrate metabolism, and neoglucogenesis are upregulated. Microbiota composition is rapidly altered after EECs depletion and is characterized by decreased a-diversity. Bacteroides and Lactobacillus were progressively enriched, whereas Lachnospiraceae declined without impacting fecal short-chain fatty acid concentrations.

CONCLUSIONS

EECs are dispensable for survival in adult male mice under a standard chow diet. The absence of EECs impairs intestinal lipid absorption, leading to transcriptomic and metabolic adaptations and remodeling of the gut microbiota.

Type 2 Diabetes in Obesity: A Systems Biology Study on Serum and Adipose Tissue Proteomic Profiles

Obesity is associated with metabolic disorders such as insulin resistance and type 2 diabetes mellitus (T2DM), further increasing an already heightened cardiovascular risk. Here, amongst obese class III bariatric surgery patients, we have investigated the effect of T2DM in serum and in two, same patient, adipose tissue (AT) depots through proteomic profile expression analyses. Serum and AT samples from subcutaneous (SAT) and visceral (VAT) fat were collected during bariatric surgery. Bead-based targeted multiplex assay systems were used to simultaneously detect and quantify multiple targets in serum samples (targeted proteomics) and analyze changes in adipokine serum composition. AT samples were assessed through an untargeted proteomics approach. Through a systems biology analysis of the proteomic data, information on the affected biological pathways was acquired. In obese class III individuals, the presence of T2DM induced a significantly higher systemic release of ghrelin, GLP-1, glucagon, MMP3, BAFF, chitinase 3-like 1, TNF-R1 and TNF-R2, and a lower systemic release of IL-8. SAT and VAT proteomes belonging to the same patient showed significant differences in local protein content. While the proteins upregulated in VAT were indicative of metabolic dysregulation, SAT protein upregulation suggested adequate endocrine regulation. The presence of T2DM significantly affected VAT protein composition through the upregulation of dysregulating metabolic pathways, but SAT protein composition was not significantly modified. Our results show that T2DM induces metabolic dysregulation in obese individuals with changes in systemic marker levels and impairment of proteostasis in VAT but not in SAT.

Metabolic labeling unveils alterations in the turnover of HDL-associated proteins during diabetes progression in mice

Several aspects of diabetes pathophysiology and complications result from hyperglycemia-induced alterations in the structure and function of plasma proteins. Furthermore, insulin has a significant influence on protein metabolism by affecting both the synthesis and degradation of proteins in various tissues. To understand the role of progressive hyperglycemia on plasma proteins, in this study, we measured the turnover rates of high-density lipoprotein (HDL)-associated proteins in control (chow diet), prediabetic [a high-fat diet (HFD) for 8 wk] or diabetic [HFD for 8 wk with low-dose streptozotocin (HFD + STZ) in weeks 5-8 of HFD] C57BL/6J mice using heavy water (2H2O)-based metabolic labeling approach. Compared with control mice, HFD and HFD + STZ mice showed elevations of fasting plasma glucose levels in the prediabetic and diabetic range, respectively. Furthermore, the HFD and HFD + STZ mice showed increased hepatic triglyceride (TG) levels, total plasma cholesterol, and plasma TGs. The kinetics of 40 proteins were quantified using the proteome dynamics method, which revealed an increase in the fractional synthesis rate (FSR) of HDL-associated proteins in the prediabetic mice compared with control mice, and a decrease in FSR in the diabetic mice. The pathway analysis revealed that proteins with altered turnover rates were involved in acute-phase response, lipid metabolism, and coagulation. In conclusion, prediabetes and diabetes have distinct effects on the turnover rates of HDL proteins. These findings suggest that an early dysregulation of the HDL proteome dynamics can provide mechanistic insights into the changes in protein levels in these conditions.NEW & NOTEWORTHY This study is the first to examine the role of gradual hyperglycemia during diabetes disease progression on HDL-associated protein dynamics in the prediabetes and diabetic mice. Our results show that the fractional synthesis rate of HDL-associated proteins increased in the prediabetic mice whereas it decreased in the diabetic mice compared with control mice. These kinetic changes can help to elucidate the mechanism of altered protein levels and HDL dysfunction during diabetes disease progression.

CircRNA screening and ceRNA network construction for milk fat metabolism in dairy cows

BACKGROUND

Milk fat is one of the main reference elements for evaluating milk quality and is a primary objective trait in dairy cattle breeding. In recent years, circular RNAs (circRNAs) have been found to play crucial roles in many biological processes. However, the function and expression profiles of circRNAs in milk fat synthesis in cows are not completely understood. We performed RNA sequencing to analyze the genome-wide expression of circRNA transcripts in bovine mammary epithelial cells (BMECs) from cows with extreme differences in milk fat percentage. We identified candidate differential circRNAs associated with milk fat metabolism using functional enrichment analysis and constructed a lipid metabolism-related competing endogenous RNA (ceRNA) interactive regulatory network.

RESULTS

A total of 290 circRNAs were significantly differentially expressed (DE-circRNAs) in high milk fat percentage (HMF) cows compared to that in low milk fat percentage (LMF) cows. Of the 290 circRNAs, 142 were significantly upregulated and 148 were significantly downregulated. Enrichment analysis (Gene Ontology and Kyoto Encyclopedia of Genes and Genomes) identified four DE-circRNAs (circ_0001122, circ_0007367, circ_0018269, and circ_0015179) that potentially regulate milk fat metabolism. Among them, circ_0001122, circ_0007367, and circ_0015179 had relatively high expression levels in cow mammary gland tissue compared to other tissues (heart, liver, kidney, uterus, ovaries, and small intestine) of cows. The regulatory networks circ_0001122:miR-12043:LIPG, circ_0007367:miR-331-3p:CIDEA/PML, and circ_0018269:miR-11989:RORC/HPX are potential networks to explore the mechanism of milk fat regulation.

CONCLUSIONS

These results reveal the possible role of circRNAs in milk fat metabolism in dairy cows. Several important circRNAs and ceRNAs affecting milk fat synthesis were identified, providing insights into the complex biology of milk fat synthesis as well as a novel theoretical perspective for future research on lactation, milk quality, and breed improvement in dairy cows.

Changes in apolipoprotein abundance dominate proteome responses to prolonged fasting in elephant seals

Unlike many animals that reduce activity during fasting, northern elephant seals (NES) undergo prolonged fasting during energy-intensive life-history stages such as reproduction and molting, fueling fasting energy needs by mobilizing fat stores accrued during foraging. NES display several unique metabolic features such as high fasting metabolic rates, elevated blood lipid and high-density lipoprotein (HDL) cholesterol levels, efficient protein sparing and resistance to oxidative stress during fasting. However, the cellular mechanisms that regulate these adaptations are still not fully understood. To examine how metabolic coordination is achieved during prolonged fasting, we profiled changes in blubber, skeletal muscle and plasma proteomes of adult female NES over a 5 week fast associated with molting. We found that while blubber and muscle proteomes were remarkably stable over fasting, over 50 proteins changed in abundance in plasma, including those associated with lipid storage, mobilization, oxidation and transport. Apolipoproteins dominated the blubber, plasma and muscle proteome responses to fasting. APOA4, APOE and APOC3, which are associated with lipogenesis and triglyceride accumulation, decreased, while APOA1, APOA2 and APOM, which are associated with lipid mobilization and HDL function, increased over fasting. Our findings suggest that changes in apolipoprotein composition may underlie the maintenance of high HDL levels and, together with adipokines and hepatokines that facilitate lipid catabolism, may mediate the metabolic transitions between feeding and fasting in NES. Many of these proteins have not been previously studied in this species and provide intriguing hypotheses about metabolic regulation during prolonged fasting in mammals.

Western Diet Induced Remodelling of the Tongue Proteome

The tongue is a heavily innervated and vascularized striated muscle that plays an important role in vocalization, swallowing and digestion. The surface of the tongue is lined with papillae which contain gustatory cells expressing various taste receptors. There is growing evidence to suggest that our perceptions of taste and food preference are remodelled following chronic consumption of Western diets rich in carbohydrate and fats. Our sensitivity to taste and also to metabolising Western diets may be a key factor in the rising prevalence of obesity; however, a systems-wide analysis of the tongue is lacking. Here, we defined the proteomic landscape of the mouse tongue and quantified changes following chronic consumption of a chow or Western diet enriched in lipid, fructose and cholesterol for 7 months. We observed a dramatic remodelling of the tongue proteome including proteins that regulate fatty acid and mitochondrial metabolism. Furthermore, the expressions of several receptors, metabolic enzymes and hormones were differentially regulated, and are likely to provide novel therapeutic targets to alter taste perception and food preference to combat obesity.

Iron Metabolism in Obesity and Metabolic Syndrome

Obesity is an excessive adipose tissue accumulation that may have detrimental effects on health. Particularly, childhood obesity has become one of the main public health problems in the 21st century, since its prevalence has widely increased in recent years. Childhood obesity is intimately related to the development of several comorbidities such as nonalcoholic fatty liver disease, dyslipidemia, type 2 diabetes mellitus, non-congenital cardiovascular disease, chronic inflammation and anemia, among others. Within this tangled interplay between these comorbidities and associated pathological conditions, obesity has been closely linked to important perturbations in iron metabolism. Iron is the second most abundant metal on Earth, but its bioavailability is hampered by its ability to form highly insoluble oxides, with iron deficiency being the most common nutritional disorder. Although every living organism requires iron, it may also cause toxic oxygen damage by generating oxygen free radicals through the Fenton reaction. Thus, iron homeostasis and metabolism must be tightly regulated in humans at every level (i.e., absorption, storage, transport, recycling). Dysregulation of any step involved in iron metabolism may lead to iron deficiencies and, eventually, to the anemic state related to obesity. In this review article, we summarize the existent evidence on the role of the most recently described components of iron metabolism and their alterations in obesity.

Differentially expressed serum proteins from obese Wistar rats as a risk factor for obesity-induced diseases

Obesity is a chronic disease that negatively affects life expectancy through its association with life-threatening diseases such as cancer and cardiovascular diseases. Expression proteomics combined with in silico interaction studies are used to uncover potential biomarkers and the pathways that promote obesity-related complications. These biomarkers can either aid in the development of personalized therapies or identify individuals at risk of developing obesity-related diseases. To determine the serum protein changes, Wistar rats were fed standard chow (low fat, LF), or chow formulated high fat (HF) diets (HF1, HF2 and HF3) for 8 and 42 weeks to induce obesity. Serum samples were collected from lean and obese rats at these time points. The serum samples were precipitated using trichloroacetic acid (TCA)/acetone and analyzed by 2-Dimensional SDS-PAGE. Serum protein profiles were examined using mass spectrometry (MS)-based proteomics and validated by western blotting. Protein-protein interactions among the selected proteins were studied in silico using bioinformatics tools. Several proteins showed differences in expression among the three HF diets when compared to the LF diet, and only proteins with ≥ twofold expression levels were considered differentially expressed. Apolipoprotein-AIV (APOA4), C-reactive protein (CRP), and alpha 2-HS glycoprotein (AHSG) showed differential expression at both 8 and 42 weeks, whereas alpha 1 macroglobulin (AMBP) was differentially expressed only at 8 weeks. Network analysis revealed some interactions among the proteins, an indication that these proteins might interactively play a crucial role in development of obesity-induced diseases. These data show the variation in the expression of serum proteins during acute and chronic exposure to high fat diet. Based on the expression and the in-silico interaction these proteins warrant further investigation for their role in obesity development.

Prediction of the Secretome and the Surfaceome: A Strategy to Decipher the Crosstalk between Adipose Tissue and Muscle during Fetal Growth

Crosstalk between adipose and muscular tissues is hypothesized to regulate the number of muscular and adipose cells during fetal growth, with post-natal consequences on lean and fat masses. Such crosstalk largely remains, however, to be described. We hypothesized that a characterization of the proteomes of adipose and muscular tissues from bovine fetuses may enhance the understanding of the crosstalk between these tissues through the prediction of their secretomes and surfaceomes. Proteomic experiments have identified 751 and 514 proteins in fetal adipose tissue and muscle. These are mainly involved in the regulation of cell proliferation or differentiation, but also in pathways such as apoptosis, Wnt signalling, or cytokine-mediated signalling. Of the identified proteins, 51 adipokines, 11 myokines, and 37 adipomyokines were predicted, together with 26 adipose and 13 muscular cell surface proteins. Analysis of protein–protein interactions suggested 13 links between secreted and cell surface proteins that may contribute to the adipose–muscular crosstalk. Of these, an interaction between the adipokine plasminogen and the muscular cell surface alpha-enolase may regulate the fetal myogenesis. The in silico secretome and surfaceome analyzed herein exemplify a powerful strategy to enhance the elucidation of the crosstalk between cell types or tissues.

Dietary iron interacts with genetic background to influence glucose homeostasis

BACKGROUND

Iron is a critical component of metabolic homeostasis, but consumption of dietary iron has increased dramatically in the last 30 years, corresponding with the rise of metabolic disease. While the link between iron metabolism and metabolic health is well established, the extent to which dietary iron contributes to metabolic disease risk is unexplored. Further, it is unknown how dietary iron interacts with genetic background to modify metabolic disease risk.

METHODS

LG/J and SM/J inbred mouse strains were used to investigate the relationship between genetic background and metabolic function during an 8-week high iron diet. Glucose tolerance and adiposity were assessed, colorimetric assays determined levels of circulating metabolic markers, and hepatic iron content was measured. RNA sequencing was performed on white adipose tissue to identify genes differentially expressed across strain, diet, and strain X diet cohorts. Hepatic Hamp expression and circulating hepcidin was measured, and small nucleotide variants were identified in the Hamp genic region.

RESULTS

LG/J mice experienced elevated fasting glucose and glucose intolerance during the high iron diet, corresponding with increased hepatic iron load, increased circulating ferritin, and signs of liver injury. Adipose function was also altered in high iron-fed LG/J mice, including decreased adiposity and leptin production and differential expression of genes involved in iron and glucose homeostasis. LG/J mice failed to upregulate hepatic Hamp expression during the high iron diet, resulting in low circulating hepcidin levels compared to SM/J mice.

CONCLUSIONS

This study highlights the importance of accounting for genetic variation when assessing the effects of diet on metabolic health, and suggests dietary iron's impact on liver and adipose tissue is an underappreciated component of metabolic disease risk.

Rapid and direct determination of fatty acids and glycerides profiles in Schisandra chinensis oil by using UPLC-Q/TOF-MSE

Fatty acids and glycerides are globally accepted quality and nutrition indicators of oils. Schisandra chinensis (S. chinensis) is a good functional oil source, with an oil content of 10-50% (dry weight). In this study, the UPLC-Q/TOF-MS^E technique was developed to profile FFA and glycerides in the S. chinensis oils directly. The results showed that all of the 36 FFA calibration equations of the mixture standard had good linear relationships (R² > 0.99). The limit of detection for the tested compounds ranged from 0.0001 to 0.0200 μg/mL, while the limit of quantification ranged from 0.0005 to 0.1300 μg/mL. In total, seventeen FFAs, six diglycerides and 20 triglycerides were identified. Linoleic, oleic, stearic and palmitic acids were the most abundant FFAs in the S. chinensis oils. It was also found that S. chinensis oil is rich in the L-L, L-L-L, O-L-L and O-L-O glycerides. These results will be helpful for the use of this technique in physicochemical evaluation and for further application development.

Ironing out the Details: Untangling Dietary Iron and Genetic Background in Diabetes

The search for genetic risk factors in type-II diabetes has been hindered by a failure to consider dietary variables. Dietary nutrients impact metabolic disease risk and severity and are essential to maintaining metabolic health. Genetic variation between individuals confers differences in metabolism, which directly impacts response to diet. Most studies attempting to identify genetic risk factors in disease fail to incorporate dietary components, and thus are ill-equipped to capture the breadth of the genome's impact on metabolism. Understanding how genetic background interacts with nutrients holds the key to predicting and preventing metabolic diseases through the implementation of personalized nutrition. Dysregulation of iron homeostasis is associated with type-II diabetes, but the link between dietary iron and metabolic dysfunction is poorly defined. High iron burden in adipose tissue induces insulin resistance, but the mechanisms underlying adipose iron accumulation remain unknown. Hepcidin controls dietary iron absorption and distribution in metabolic tissues, but it is unknown whether genetic variation influencing hepcidin expression modifies susceptibility to dietary iron-induced insulin resistance. This review highlights discoveries concerning the axis of iron homeostasis and adipose function and suggests that genetic variation underlying dietary iron metabolism is an understudied component of metabolic disease.