Profound loss and senescence of adipose tissues are hallmarks of advanced age, but the underlying cause and their metabolic consequences remain obscure. Proper function of the murine double minute 2 (MDM2)–p53 axis is known to prevent tumorigenesis and several metabolic diseases, yet its role in regulation of adipose tissue aging is still poorly understood. In this study, we show that the proximal p53 inhibitor MDM2 is markedly downregulated in subcutaneous white and brown adipose tissues of mice during aging. Genetic disruption of MDM2 in adipocytes triggers canonical p53-mediated apoptotic and senescent programs, leading to age-dependent lipodystrophy and its associated metabolic disorders, including type 2 diabetes, nonalcoholic fatty liver disease, hyperlipidemia, and energy imbalance. Surprisingly, this lipodystrophy mouse model also displays premature loss of physiological integrity, including impaired exercise capacity, multiple organ senescence, and shorter life span. Transplantation of subcutaneous fat rejuvenates the metabolic health of this aging-like lipodystrophy mouse model. Furthermore, senescence-associated secretory factors from MDM2-null adipocytes impede adipocyte progenitor differentiation via a non–cell-autonomous manner. Our findings suggest that tight regulation of the MDM2–p53 axis in adipocytes is required for adipose tissue dynamics and metabolic health during the aging process.

CD4 ⁺ cytotoxic T lymphocytes (CTLs) were recently implicated in immune-mediated inflammation and fibrosis progression of Graves’ orbitopathy (GO). However, little is known about therapeutic targeting of CD4 ⁺ CTLs. Herein, we studied the effect of rapamycin, an approved mTOR complex 1 (mTORC1) inhibitor, in a GO mouse model, in vitro, and in patients with refractory GO. In the adenovirus-induced model, rapamycin significantly decreased the incidence of GO. This was accompanied by the reduction of both CD4 ⁺ CTLs and the reduction of orbital inflammation, adipogenesis, and fibrosis. CD4 ⁺ CTLs from patients with active GO showed upregulation of the mTOR pathway, while rapamycin decreased their proportions and cytotoxic function. Low-dose rapamycin treatment substantially improved diplopia and the clinical activity score in steroid-refractory patients with GO. Single-cell RNA-Seq revealed that eye motility improvement was closely related to suppression of inflammation and chemotaxis in CD4 ⁺ CTLs. In conclusion, rapamycin is a promising treatment for CD4 ⁺ CTL-mediated inflammation and fibrosis in GO.

Background: White adipose tissue can be classified based on its location as subcutaneous and visceral fat, and the latter accumulation is reported to be more detrimental to metabolism. Endoplasmic reticulum (ER) stress has been demonstrated to regulate lipogenesis. The peptide angiotensin(1–7) [Ang(1–7)], which can be produced from angiotensin II (AngII) by angiotensin-converting enzyme 2 (ACE2), plays its role through Mas receptor, also participates in the regulation of lipid metabolism in adipose tissue, however, whether ER stress is involved in the mechanism remains unclear. Therefore, we aimed to explore the role of Ang(1–7) pathway in regulating visceral adipose tissue expansion and ER stress. Methods: ACE2 knockout (KO), Mas KO and C57BL/6 J mice were fed with high fat diet. Db/db mice were treated with either normal saline, Ang(1–7) or Ang(1–7) combined with Mas receptor inhibitor A779 using mini osmotic pumps. Fat mass was weighted, fat distribution was evaluated by MRI, and lipid profile and adipokines in epididymal adipose tissue were measured by ELISA kits, and histology of epididymal adipose tissue was also analyzed in multiple animal models. Additionally, differentiated 3T3-L1 cells were pre-loaded with palmitic acid to induce ER stress, then treated with drugs as those administrated to db/db mice. ER stress and lipogenesis related proteins in mice adipose and differentiated 3T3L-1 cells were analyzed by Western blot. Results: ACE2 or Mas KO mice exhibited increased visceral adipose tissue, adipocyte size and protein expression of lipogenesis and ER stress related markers in epididymal adipose tissue compared to wild-type mice. Db/db mice treated with Ang(1–7) displayed decreased visceral fat mass, adipocyte size and protein expression of lipogenesis and ER stress markers in epididymal adipose tissue compared to those treated with normal saline, while A779 partly attenuated these effects. Additionally, Ang(1–7) improved ER stress and lipogenesis markers in differentiated 3T3-L1 cells pre-loaded with palmitic acid. Conclusions: Our findings indicated that Ang(1–7) attenuated visceral adipose tissue expansion and lipogenesis by suppression of ER stress via Mas receptor. The present study provides a potential perspective for Ang(1–7) for the therapeutics of obesity and related disorders.

Impaired fasting glucose (IFG) is a reversible intermediate hyperglycemia stage with an increasing risk of diabetes and related complications. Our study was designed to identify the relationship between the serum anion gap and the risk of progressing to impaired fasting glucose and diabetes. Here, we performed a prospective, population-based study among 1191 Chinese individuals aged 22–87 years who took health examinations annually between 2006 and 2012 including clinical features and plasma metabolites. All of the participants had no history of diabetes or related chronic complications. Logistic regression analysis was designed to examine the associations between clinical and metabolomic factors and the risk of developing IFG or diabetes. Among them, 58 subjects whose fasting glucose were between 6.1 and 7 mmol/L were diagnosed as IFG or diabetes. After adjusting for age, sex, body mass index (BMI), high-density lipoprotein (HDL), low-density lipoprotein (LDL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), systolic blood pressure (SBP), diastolic blood pressure (DBP), potassium, and albumin at baseline, the participants in the upper tertiles of serum anion gap (SAG) had higher odds of progressing to IFG or diabetes than those in the lower tertiles. A receiver operating characteristic (ROC) curve was analyzed, and the optimal cutoff level for the anion gap to predict incident IFG or diabetes was 13.76 mmol/L, and the area under the ROC curve (AUC) was 0.623. Our data demonstrate that a higher serum anion gap is associated with the risk of developing IFG or diabetes.

Purpose: Graves’ orbitopathy (GO) is a sight-threatening organ-specific autoimmune disease with complicated pathogenesis. Gut microbiota-derived tryptophan (Trp) metabolites play important roles in immune-related diseases, but their role in GO remains unknown. Methods: Trp metabolism-associated gut flora was analyzed by 16 S sequencing in GO patients and controls. Serum metabolomics profiling was performed to assess Trp metabolic pathway. Trp metabolites levels were measured by ELISA in 401 serum samples from a case-control study, and their effects on inflammation and proliferation in orbital fibroblasts were evaluated in vitro. Results: Trp metabolism-associated gut flora, including phylum Firmicutes and genus Anaerostipes, were significantly down-regulated in GO patients. Serum metabolomics revealed significant enrichment of Trp metabolic pathway in both GO and Graves’ disease (GD) groups. Serum levels of indolepropionic acid (IPA), indole-3-lactate (ILA), and indoleacetic acid (IAA) were significantly decreased in both GD and GO patients compared to controls, with IAA levels further reduced in GO compared to GD patients. Notably, active GO patients had significantly lower IAA levels compared to inactive ones. Moreover, the levels of IAA were negatively correlated with clinical activity score and serum thyrotropin receptor antibody (TRAb) in GO patients. In vitro, IPA, ILA, and IAA mitigated TNFα-induced inflammation and proliferation in orbital fibroblasts by suppressing the Akt signaling pathway. Conclusion: Trp metabolites IAA maybe a novel biomarker for GO progression. And IPA, ILA and IAA may play a protective role in GO by regulating inflammation and proliferation in orbital fibroblasts, suggesting their potential as therapeutic targets for GO treatment.

Graves' orbitopathy (GO) is a sight-threatening disease associated with thyroid dysfunction, with an unmet medical need for early diagnosis and treatment. Orbital fibroblasts (OFs) proliferation and migration play central roles in the pathogenesis of GO. Homocysteine (Hcy) has been demonstrated to be related to thyroid function, but its role in GO remains unclear. In this study, we aimed to investigate the role of Hcy in GO progression and its effects on OFs. A total of 131 patients with Graves' disease (GD) were enrolled, of which 68 suffered from GO, with 40 having inactive GO and 28 having active GO. Serum Hcy levels were measured using ELISA assays. Primary cultured OFs were established from orbital connective tissues. Cell proliferation was quantified using CCK-8 assays, while wound healing assays were used to evaluate OFs migration. Western blotting was used to measure Akt signaling pathway. Under a matched thyroid function state, serum Hcy levels were significantly higher in GO patients than in GD. More interestingly, active GO patients had significantly elevated Hcy levels compared to inactive GO patients. Furthermore, serum Hcy levels correlated positively with clinical activity scores in GO patients. In vitro, Hcy stimulated OFs proliferation and migration under both physiological and inflammatory conditions. Mechanistically, Hcy activated the Akt signaling pathway in OFs under these conditions. This study supports the potential role of Hcy as a novel biomarker for GO progression. Furthermore, Hcy stimulates OFs proliferation and migration, suggesting its potential as a therapeutic target for GO treatment.