Editorial: Adipose tissue dysfunction

Transcriptomic analysis of adipose tissue reveals adipogenesis is modulated by the degree of weight loss in patients with obesity

BACKGROUND AND AIMS

Obesity is a complex condition with a diverse presentation and highly variable response to treatment. It is increasingly evident that obesity requires a plethora of interventions informed by biomarkers to optimise the chance of success. Adipose tissue is a metabolically active endocrine tissue and its metabolic response to intervention has the potential to provide key information to design targeted treatments to tackle obesity. To this aim, this study sought to identify, through transcriptomics analysis, common elements between adipose tissue of those undergoing bariatric surgery to those who were successful in losing weight through a lifestyle intervention.

METHODS AND RESULTS

Transcriptomic data from Gene Expression Omnibus were extracted from three bariatric surgery interventions and three lifestyle interventions. Paired linear mixed modelling using the limma package in R was used to determine differentially expressed genes before and after the interventions. Unpaired linear mixed modelling was used to determine differentially expressed genes between high and low responders to the intervention. Differentially modulated pathways were analysed with PathVisio and downloaded for graphic representation from the WikiPathways database.

CONCLUSION

We demonstrated that successful lifestyle interventions and bariatric surgery share the modulation of the Adipogenesis pathway (WP236). Leptin expression was positively correlated with weight loss, only up to a 10 % weight loss, suggesting a possible involvement of its dysregulation in explaining individual propensity to weight regain and potentially indicating who requires a targeted intervention. We also identify an interesting relationship between RBL2 expression and weight loss that requires further investigation.

Plasma Lipidomics, Gut Microbiota Profile, and Phenotype of Adipose Tissue in an ApoE-/- Mouse Model of Plaque Instability

BACKGROUND

An appropriate animal model that can simulate the pathological process of atherosclerosis is urgently needed to improve treatment strategies. This study aimed to develop a new atherosclerosis model using ApoE-/- mice and to characterize lipidomics, gut microbiota profiles, and phenotypic alterations in adipose tissue using this model.

METHODS

After a 14- or 18-week high-fat diet (HFD), male ApoE-/- mice were randomly divided into four groups and treated separately with or without short-term and strong co-stimulation, including ice water bath and intraperitoneal injection of lipopolysaccharide and phenylephrine. As a control group, C57BL/6 mice were fed with conventional chow. The serum lipid levels, aortic arch pathology, adipose tissue phenotypic changes, plasma lipidomics, and 16S rDNA gene sequencing of colon feces were investigated.

RESULTS

The serum lipid levels were significantly lowered following extended HFD feeding for four weeks. However, co-stimulation increased serum interleukin (IL)-1β levels but did not affect serum lipid profiles. Co-stimulation revealed typical vulnerable atherosclerotic plaque characteristics and defective adipose hypertrophy associated with peroxisome proliferator-activated receptor γ (PPARγ) regulation in adipose tissue and a reduction in mitochondrial uncoupling protein 1 (UCP1) within brown adipose tissue. Plasma lipidomic analysis showed that sphingomyelin (SM), ceramide (Cer), and monohexosylceramide (HexCer) levels in plasma were significantly elevated by HFD feeding, whereas co-stimulation further elevated HexCer levels. Additionally, glycerophosphocholines (16:0/16:0, 18:2/20:4, 18:1/18:1) and HexCer (C12:1, C16:0), Cer (d18:1/16:0), and SM (C16:0) were the most sensitive to co-stimulation. Combined co-stimulation and HFD-fed increased the abundance of Firmicutes, the abundance of f_Erysipelotrichaceae, and the Firmicutes/Bacteroidota ratio but decreased the abundance of microflora promoting bile acid metabolism and short-chain fatty acids (SCFAs) in mouse feces. The results were consistent with the findings of epidemiologic atherosclerotic cardiovascular disease studies.

CONCLUSIONS

This study established an ApoE-/- mouse atherosclerotic vulnerable plaque model using a multi-index evaluation method. Adipogenic disorders, dysregulation of lipid metabolism at the molecular level, and increasing harmful gut microbiota are significant risk factors for vulnerable plaques, with sphingolipid metabolism receiving the most attention.

Adipose failure through adipocyte overload and autoimmunity

Metabolic syndrome poses a great worldwide threat to the health of the patients. Increased visceral adiposity is recognized as the main determinant of the detrimental clinical effects of insulin resistance. Inflammation and immune system activation in the adipose tissue (AT) have a central role in the pathophysiology of metabolic syndrome, but the mechanisms linking increased adiposity to immunity in the AT remain in part elusive. In this review, we support the central role of adipocyte overload and relative adipose failure as key determinants in triggering immune aggression to AT. This provides a mechanistic explanation of the relative metabolic wellness of metabolically normal obese people and the disruption in insulin signaling in metabolically obese lean people.