Metabolic syndrome (MS) comprises central obesity, increased plasma glucose levels, hyperlipidemia and hypertension, and its incidence is increasing due to changes in lifestyle and dietary structure in recent years. MS has been proven to be associated with an increased incidence of cardiovascular diseases and type 2 diabetes mellitus, leading to morbidity and mortality. In this manuscript, we review recent studies concerning the role of the gut microbiota in MS modulation. Manipulation of the gut microbiota through the administration of prebiotics or probiotics may assist in weight loss and reduce plasma glucose and serum lipid levels, decreasing the incidence of cardiovascular diseases and type 2 diabetes mellitus. To the best of our knowledge, short-chain fatty acids (SCFAs), bile salt hydrolase (BSH), metabolic endotoxemia and the endocannabinoid (eCB) system are essential in regulating the initiation and progression of MS through the normalization of adipogenesis and the regulation of insulin secretion, fat accumulation, energy homeostasis, and plasma cholesterol levels. Therefore, the gut microbiota may serve as a potential therapeutic target for MS. However, further studies are needed to enhance our understanding of manipulating the gut microbiota and the role of the gut microbiota in MS prevention and treatment.

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: Graves' orbitopathy (GO) is the most common and serious manifestation of Graves' disease (GD). It is characterized by orbital inflammation and tissue remodeling. Although several GO models have been reported, most lack a full assessment or mechanistic evaluation. Here, we established a promising mouse model mimicking many aspects of human GO with a frequency of 70% and characterized the key role of T cells in the progression of GO. Methods: An adenovirus expressing the human thyrotropin (TSH) receptor A subunit (Ad-TSHRA) was injected in the muscles of female BALB/C mice nine times to induce GO. At predetermined time points, histological examinations of retrobulbar tissues and thyroid glands were performed to dynamically monitor changes; serum autoantibodies and total thyroxine levels were examined to evaluate thyroid function. Flow cytometry of CD4+ T cell subgroups and RNA sequencing (RNA-Seq) of splenocytes were also performed to explore the underlying mechanism. Results: After nine injections, 7 of 10 mice challenged with Ad-TSHRA developed the orbital changes associated with GO. Seven mice manifested retrobulbar fibrosis, and four mice showed adipogenesis. Exophthalmia, conjunctival redness, and orbital lymphocyte infiltration were also observed in a subset of mice. The orbitopathy was first detected after seven injections and followed the hyperplastic change observed in thyroids after four injections. Flow cytometry revealed increased proportions of Th1 cells and decreased proportions of Th2 cells and regulatory T (Treg) cells in the splenocytes of GO mice. This change in CD4+ T cell subgroups was confirmed by orbital immunohistochemical staining. Genes involved in T cell receptor signaling, proliferation, adhesion, inflammation, and cytotoxicity were upregulated in GO mice according to the RNA-Seq; a trend of upregulation of these GO-specific genes was observed in mice with hyperthyroidism without orbitopathy after four injections. Conclusions: A GO mouse model was successfully established by administering nine injections of Ad-TSHRA. The model was achieved with a frequency of 70% and revealed the importance of T cell immunity. A potential time window from Graves' hyperthyroidism to GO was presented for the first time. Therefore, this model could be used to study the pathogenesis and novel treatments for GO.

Time-restricted eating (TRE) and low-carbohydrate diet (LCD) can improve multiple cardiometabolic parameters in patients with metabolic syndrome (MetS), but their effects on psychosocial health and satiety are unclear. In this study, we aimed to evaluate the effects of TRE, LCD, and their combination (TRE + LCD) on quality of life (QoL), sleep, mood, appetite, and metabolic hormones in patients with MetS. This is a secondary analysis of a single-center, 3-month, open-label, randomized clinical trial investigating the effects of TRE, LCD, and TRE + LCD on weight and cardiometabolic parameters in individuals with MetS. This secondary analysis examined QoL, sleep, mood, and appetite using the Rand 36-Item Short Form (SF-36); Pittsburgh Sleep Quality Index (PSQI); Depression, Anxiety, and Stress Scale; and Eating Behavior Rating Scale, respectively, as well as measured levels of metabolic hormones including leptin, amylin, glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1 (GLP-1), pancreatic polypeptide (PP), and peptide YY. Between-group comparisons were conducted via one-way ANOVAs and post hoc LSD tests for normally distributed variables or Kruskal‒Wallis H tests and the Nemenyi test for abnormally distributed variables. P < 0.017 was considered significant in multiple comparisons following Bonferroni adjustment. A total of 162 participants (mean [SD] age, 41.2 [9.9] years; mean [SD] body mass index, 29.3 [3.4] kg/m²; 102 [63%] men) who started the intervention were analyzed. After 3 months, only the TRE group decreased GLP-1 levels (-0.9 [IQR, -1.9 to -0.3] pg/mL; P = 0.002), increased PP levels (8.9 [IQR, -7.6 to 71.8] pg/mL; P = 0.011), physical functioning in the SF-36 (5.2 [95% CI, 1.9 to 8.5]; P = 0.001), social functioning in the SF-36 (9.1 [95% CI, 2.5 to 15.6]; P = 0.005), role-physical in the SF-36 (24.1 [95% CI, 11.8 to 36.4]; P < 0.001), role-emotional in the SF-36 (22.4 [95% CI, 12.6 to 32.2]; P < 0.001), and sleep efficiency in the PSQI (0.29 [95% CI, 0.03 to 0.55]; P = 0.021). Compared with changes in LCD, TRE further increased general health in the SF-36 (9.7 [95% CI, 3.3 to 16.0]; P = 0.006). Relative to the changes of TRE + LCD, TRE significantly increased role-emotional in the SF-36 (19.9 [95% CI 4.9 to 34.8]; P = 0.006). Changes in sleep quality, mood status, appetite, and metabolic hormones did not differ among three groups. Greater weight loss was associated with decreased leptin levels (r = 0.538), decreased amylin levels (r = 0.294), reduced total appetite scores (r = 0.220), and improved general health (r = -0.253) (all P ≤ 0.01). TRE, LCD, and TRE + LCD all could improve psychosocial health and reduce appetite. Notably, TRE yielded greater benefits in QoL compared with LCD or TRE + LCD in individuals with MetS. ClinicalTrials.gov Identifier: NCT04475822.

Background/Objectives: Mounting evidence indicates that the short-chain fatty acid butyrate protects against obesity and associated comorbidities, partially through the induction of adipose tissue thermogenesis. However, the effects of butyrate on white adipose tissue (WAT) browning and its molecular mechanism are still elusive. The objective of this study was to investigate butyrate-induced thermogenesis in white adipose tissue and its underlying mechanism. Methods: We studied the effects of butyrate on diet-induced obesity in the humanized APOE*3-Leiden.CETP transgenic mouse model and explored factors related to white adipose browning. Specifically, mice were challenged with a high-fat diet supplemented with butyrate. Adiposity was measured to assess obesity development. Energy metabolism was detected using an indirect calorimetry system. RNA-seq analysis was conducted to analyze the transcription landscape of WAT and responsible targets. Furthermore, the revealed molecular mechanism was verified in vitro. Results: Butyrate alleviated high-fat diet-induced obesity and promoted energy expenditure accompanied by brown adipose tissue activation and WAT browning. Mechanistically, RNA-seq analysis revealed that butyrate downregulated HDAC9 in WAT. Additionally, butyrate decreased HDAC9 while increasing thermogenesis in vitro. Inhibition of HDAC9 with TMP269 promoted thermogenic gene expression, mimicking the effects of butyrate. Conclusions: Butyrate protects against diet-induced obesity accompanied by decreasing the expression of HDAC9 in white adipose tissue and inducing browning. This study reveals a new mechanism whereby butyrate activates adaptive thermogenesis and provides new insights for the development of weight-loss drugs targeting adipose HDAC9.

Diabetic retinopathy (DR) is a major microvascular complication of diabetes mellitus and causes vision impairment and blindness. The presence of major risk factors for DR, such as high levels of HbA1c, does not predict all DR pathogenesis in the clinic, which suggests that uncovering the underlying mechanisms and identifying novel markers are needed. Previous evidence has shown that the serum metabolic signature of DR is unique and detectable compared with that of diabetes mellitus (DM). Here, we aimed to identify serum metabolites as reliable biomarkers for the presence of DR in type 2 DM (T2DM) patients. We performed untargeted and targeted metabolomic studies using liquid chromatography‒mass spectrometry (LC‒MS) and multiple reaction monitoring (MRM) methods on the serum samples of T2DM patients. For the discovery dataset, 39 DR patients and 39 non-DR (NDR) patients were included. For the validation dataset, 95 DR patients and 95 non-DR (NDR) patients were included. Receiver operating characteristic curve analysis was performed to evaluate the discriminating power of the metabolites. Binary logistic regression models were fit to evaluate the associations of metabolite peak areas or neurotransmitter concentrations with the presence of DR and adjusted for known risk factors. A total of 7123 metabolites were tested. The 39 DR patients had a mean age of 56 years with an average diabetes duration of 12 years, and the 39 NDR patients had a mean age of 57 years with an average diabetes duration of 11 years. Nine serum candidate markers were further identified. Six out of nine markers were associated with DR after we adjusted for covariates, including blood pressure, HbA1c, diabetes duration, fasting blood glucose, triglyceride, eGFR etc. Among them, eicosapentaenoic acid (EPA) and L-tyrosine were validated in an independent, risk factor-matched sample set. The serum L-tyrosine concentration was decreased in DR group by 47% (-0.22 ± 0.87 vs. 0.48 ± 1.05, P < 0.001), of which the cutoff value was 0.10 mg/ml, with 86% sensitivity and 40% specificity (AUC = 0.62, 95% CI = 0.54–0.70, P = 0.005). Low levels of circulating L-Tyrosine indicate retinopathy occurrence in T2DM population.