The effects of short-term high-fat feeding on exercise capacity: multi-tissue transcriptome changes by RNA sequencing analysis

Metabolic and Transcriptomic Changes in the Mouse Brain in Response to Short-Term High-Fat Metabolic Stress

The chronic consumption of diets rich in saturated fats leads to obesity and associated metabolic disorders including diabetes and atherosclerosis. Intake of a high-fat diet (HFD) is also recognized to dysregulate neural functions such as cognition, mood, and behavior. However, the effects of short-term high-fat diets on the brain are elusive. Here, we investigated molecular changes in the mouse brain following an acute HFD for 10 days by employing RNA sequencing and metabolomics profiling. Aberrant expressions of 92 genes were detected in the brain tissues of acute HFD-exposed mice. The differentially expressed genes were enriched for various pathways and processes such as superoxide metabolism. In our global metabolomic profiling, a total of 59 metabolites were significantly altered by the acute HFD. Metabolic pathways upregulated from HFD-exposed brain tissues relative to control samples included oxidative stress, oxidized polyunsaturated fatty acids, amino acid metabolism (e.g., branched-chain amino acid catabolism, and lysine metabolism), and the gut microbiome. Acute HFD also elevated levels of N-acetylated amino acids, urea cycle metabolites, and uracil metabolites, further suggesting complex changes in nitrogen metabolism. The observed molecular events in the present study provide a valuable resource that can help us better understand how acute HFD stress impacts brain homeostasis.

Alteration of intestinal mucosal microbiota in mice with Chinese dampness-heat syndrom diarrhea by improper diet combined with high temperature and humidity environments

Background

Environment, diet, and emotion may trigger diarrhea, but the mechanism is unclear. Dietary habits or environmental factors affect the composition of gut microbiota. This study aimed to investigate the effects of improper diet combined with high humidity and temperature (HTH) environment on the intestinal mucosal microbiota.

Materials and methods

Kunming mice were randomly assigned to two equal groups of five mice, namely the control (ccm) group and the model (cmm) group. Diarrhea mice with dampness-heat (DSH) were established by improper diet combined with HTH environments. We used 16S rRNA gene amplicon sequencing to analyze the characteristics of intestinal mucosal microbiota and the interaction relationship of function.

Results

Our study shows that the intestinal mucosal microbiota of mice changed significantly after an improper diet combined with the HTH environments. The abundance of Fusobacteria and Haemophilus increased dramatically in the cmm group compared to the ccm group (P<0.05). And the abundance of Firmicutes, Lactobacillus, and Lonsdalea was significantly decreased in the cmm group (P<0.05). According to the functional predictive analysis, we found that Lactobacillus showed a significant negative correlation with Protein export, Homologous recombination, Phenylalanine, tyrosine, tryptophan biosynthesis, Citrate cycle, and Lipoic acid metabolism.

Conclusion

Diarrhea with DSH constructed under improper diet and HTH environment may be related to Lactobacillus and Haemophilus. And long-term consumption of improper diet and the HTH environment may affect metabolism.

Unveiling the transcriptome alteration of POMC neuron in diet-induced obesity

Loss of neuron homeostasis in the arcuate nucleus (ARC) is responsible for diet-induced-obesity (DIO). We previously reported that loss of Rb1 gene compromised the homeostasis of anorexigenic POMC neurons in ARC and induced obesity in mice. To evaluate the development of DIO, we propose to analyze the transcriptomic alteration of POMC neurons in mice following high fat diet (HFD) feeding. We isolated these neurons from established DIO mice and performed transcriptomic profiling using RNA-seq. In total, 1066 genes (628 upregulated and 438 downregulated) were identified as differentially expressed genes (DEGs). Pathway enrichment analysis with these DEGs further revealed that "cell cycle," "apoptosis," "chemokine signaling," and "sphingolipid metabolism" pathways were correlated with DIO development. Moreover, we validated that the pRb protein, a key regulator of "cell cycle pathway," was inactivated by phosphorylation in POMC neurons by HFD feeding. Importantly, the reversal of deregulated cell cycle by stereotaxic delivering of the unphosphorylated pRbΔP in ARC significantly meliorated the DIO. Collectively, our study provides insights into the mechanisms related to the loss of homeostasis of POMC neurons in DIO, and suggests pRb phosphorylation as a potential intervention target to treat DIO.

Muscle metabolic reprogramming underlies the resistance of liver fatty acid-binding protein (LFABP)-null mice to high-fat feeding-induced decline in exercise capacity

Liver fatty acid-binding protein (LFABP) binds long-chain fatty acids with high affinity and is abundantly expressed in the liver and small intestine. Although LFABP is thought to function in intracellular lipid trafficking, studies of LFABP-null (LFABP^-/-) mice have also indicated a role in regulating systemic energy homeostasis. We and others have reported that LFABP^-/- mice become more obese than wildtype (WT) mice upon high-fat feeding. Here, we show that despite increased body weight and fat mass, LFABP^-/- mice are protected from a high-fat feeding-induced decline in exercise capacity, displaying an approximate doubling of running distance compared with WT mice. To understand this surprising exercise phenotype, we focused on metabolic alterations in the skeletal muscle due to LFABP ablation. Compared with WT mice, resting skeletal muscle of LFABP^-/- mice had higher glycogen and intramuscular triglyceride levels as well as an increased fatty acid oxidation rate and greater mitochondrial enzyme activities, suggesting higher substrate availability and substrate utilization capacity. Dynamic changes in the respiratory exchange ratio during exercise indicated that LFABP^-/- mice use more carbohydrate in the beginning of an exercise period and then switch to using lipids preferentially in the later stage. Consistently, LFABP^-/- mice exhibited a greater decrease in muscle glycogen stores during exercise and elevated circulating free fatty acid levels postexercise. We conclude that, because LFABP is not expressed in muscle, its ablation appears to promote interorgan signaling that alters muscle substrate levels and metabolism, thereby contributing to the prevention of high-fat feeding-induced skeletal muscle impairment.

Interscapular and Perivascular Brown Adipose Tissue Respond Differently to a Short-Term High-Fat Diet

Brown adipose tissue (BAT) function may depend on its anatomical location and developmental origin. Interscapular BAT (iBAT) regulates acute macronutrient metabolism, whilst perivascular BAT (PVAT) regulates vascular function. Although phenotypically similar, whether these depots respond differently to acute nutrient excess is unclear. Given their distinct anatomical locations and developmental origins and we hypothesised that iBAT and PVAT would respond differently to brief period of nutrient excess. Sprague-Dawley rats aged 12 weeks (n=12) were fed either a standard (10% fat, n=6) or high fat diet (HFD: 45% fat, n=6) for 72h and housed at thermoneutrality. Following an assessment of whole body physiology, fat was collected from both depots for analysis of gene expression and the proteome. HFD consumption for 72h induced rapid weight gain (c. 2.6%) and reduced serum non-esterified fatty acids (NEFA) with no change in either total adipose or depot mass. In iBAT, an upregulation of genes involved in insulin signalling and lipid metabolism was accompanied by enrichment of lipid-related processes and functions, plus glucagon and peroxisome proliferator-activated receptor (PPAR) signalling pathways. In PVAT, HFD induced a pronounced down-regulation of multiple metabolic pathways which was accompanied with increased abundance of proteins involved in apoptosis (e.g., Hdgf and Ywaq) and toll-like receptor signalling (Ube2n). There was also an enrichment of DNA-related processes and functions (e.g., nucleosome assembly and histone exchange) and RNA degradation and cell adhesion pathways. In conclusion, we show that iBAT and PVAT elicit divergent responses to short-term nutrient excess highlighting early adaptations in these depots before changes in fat mass.

Acute effects of dietary plant nutrients on transcriptome profiles: evidence from human studies

The health benefits of long-term dietary plant ingestion are well-established. However, literature on acute nutritional challenges is very limited. This study aimed to identify available evidence on transcriptomics responses to acute ingestion of plants or plant extracts and identify signature gene profiles that may serve as biomarkers of health status. We systematically searched electronic databases and extracted information based-on inclusion criteria such as human clinical studies, single plant-based nutrients and outcomes reported on acute transcriptome responses. A total of 11 studies reported on acute intake of plant dietary interventions. Four studies investigating natural oil extracts with three reporting on whole plants and two studies on natural plant-derived extracts. Gene expression was found to be associated with immune response (7 studies), inflammation (9 studies), metabolism (8 studies), cellular processes and cancer. The finding of this systematic review suggests that acute ingestion may significantly impact diverse physiological and pathological pathways including inflammatory, immune, cancer and oxidative stress pathways. Transcriptomics approach is proven to be an effective strategy in discovery of these anticipated mechanisms. Further studies are now required to validate and continue exploring the short-term health impact of dietary plants and their bioactive phytochemicals on gene expression and function.