Metabolism: clinical and experimental最新文献

Background: Endothelial cell (EC) senescence is a key contributor to retinal vascular dysfunction in diabetic retinopathy (DR), yet its molecular mechanisms remain incompletely understood. While PFKFB3 is well recognized for its critical function in modulating EC glycolysis and angiogenesis, its contribution to endothelial senescence in DR has not been elucidated.

Methods: Single-cell RNA sequencing was used to profile EC senescence signatures and barrier/tight-junction programs in diabetic retinas. PFKFB3/USP7 abundance and Senescence in vivo and in vitro were assessed by Western blotting, SA-β-gal staining, immunofluorescence, and cell-cycle flow cytometry. PFKFB3-USP7 interaction was examined by co-immunoprecipitation, mass spectrometry, and nuclear colocalization. Retinal vascular dysfunction was quantified by Evans blue leakage and PAS-stained retinal trypsin digests.

Results: Single-cell analysis identified ECs subclusters enriched for senescence transcripts and simultaneously depleted for barrier/tight-junction pathways in diabetic retinas. Hyperglycemia reduced PFKFB3 and impaired its nuclear entry, leading to prominent cellular senescence in vitro and in vivo, and restoration of PFKFB3 effectively reversed this phenotype. By establishing stable endothelial cell lines expressing PFKFB3 only in the nucleus (NLS mutant) or cytoplasm (K472Q mutant), we revealed that anti-senescent activity required PFKFB3 nuclear localization. Nuclear-localized PFKFB3 interacted with USP7, a critical modulator of the p53 pathway, and regulated the USP7-p53 axis by constraining their coupling, thereby promoting proteasomal degradation of p53. As a downstream effector of PFKFB3, USP7 abrogated the protective effect of PFKFB3, whereas its inhibition attenuated hyperglycemia-induced senescence and mitigated retinal vascular dysfunction.

Conclusions: Our findings highlighted the essential role of nuclear PFKFB3 dysfunction and USP7-p53 axis dysregulation in mediating EC senescence under diabetic stress, suggesting that targeting PFKFB3 nuclear translocation may be a novel therapeutic strategy for the prevention of diabetic retinopathy.

Objective: To delineate organ-specific and systemic drivers of metabolic dysfunction-associated steatotic liver disease (MASLD), we applied integrative causal inference across clinical, imaging, and proteomic domains in individuals with and without type 2 diabetes (T2D).

Methods: Bayesian network analyses and complementary two-sample Mendelian randomization were used to quantify causal pathways linking adipose distribution, glycemia, and insulin dynamics with liver fat in the IMI-DIRECT prospective cohort study. Data included frequently sampled metabolic challenge tests, MRI-derived abdominal and hepatic fat content, serological biomarkers, and Olink plasma proteomics from 331 adults with new-onset T2D and 964 adults without diabetes, with harmonized protocols enabling replication.

Results: High basal insulin secretion rate (BasalISR), estimated via C-peptide deconvolution, emerged as the primary potential causal driver of liver fat accumulation in both cohorts. BasalISR, a clearance-independent measure of β-cell insulin output distinct from peripheral insulin levels, was independently linked to hepatic steatosis. Visceral adipose tissue exhibited bidirectional associations with liver fat, suggesting a self-reinforcing metabolic loop. Of 446 analyzed proteins, 34 mapped to these metabolic networks (27 in the non-diabetes network, 18 in the T2D network, and 11 shared). Key proteins directly associated with liver fat included GUSB, ALDH1A1, LPL, IGFBP1/2, CTSD, HMOX1, FGF21, AGRP, and ACE2. Sex-stratified analyses identified GUSB in females and LEP in males as the strongest protein predictors of liver fat.

Conclusions: BasalISR may better capture early β-cell-driven disturbances contributing to MASLD. These findings outline a multifactorial, sex- and disease stage-specific proteo-metabolic architecture of hepatic steatosis and identify potential biomarkers or therapeutic targets.

Background: Adipocyte hypertrophy, the unique capacity of adipocytes to enlarge in response to energy surplus, is a crucial determinant of metabolic health during obesity. Nonetheless, the molecular mechanisms governing this adaptive growth remain incompletely characterized.

Methods: Super-enhancer landscapes in adipocytes were mapped via H3K27ac chromatin immunoprecipitation sequencing analysis of adipocyte nuclei from mice fed either a standard chow diet or high-fat diet (HFD) to identify transcriptional regulators activated under obesogenic conditions. Functional validation was conducted through both in vitro and in vivo experiments, including adipocyte-specific gene deletion mouse models, followed by single-nucleus RNA sequencing.

Results: Super-enhancer profiling identified Serum Response Factor (SRF) as a critical driver of actin cytoskeletal remodeling in adipocytes during obesity. SRF was shown to be both necessary and sufficient for regulation of actin cytoskeletal gene expression in 3T3-L1 adipocytes. Adipocyte-specific SRF ablation in mice led to reduced expression of actin cytoskeletal genes, disruption of actin filament organization, and impaired adipocyte enlargement under HFD feeding. Despite comparable body weight, SRF-deficient mice developed exacerbated insulin resistance and ectopic lipid accumulation in the liver and brown adipose tissue, indicative of compromised lipid storage within adipocytes. Single-nucleus RNA-seq further revealed that cell-intrinsic actin cytoskeletal defects in adipocytes propagated to tissue-level dysfunction, impairing vascularization and increasing inflammation.

Conclusion: These findings establish SRF as a central regulator of actin cytoskeletal organization that promotes healthy adipocyte hypertrophy and adipose tissue remodeling. Enhancing SRF-dependent cytoskeletal remodeling in adipocytes may offer a therapeutic strategy to preserve metabolic health in obesity.

Aim: AMPLIPHY is the first Phase 3 study comparing sepiapterin versus sapropterin in children and adults with phenylketonuria (PKU).

Methods: AMPLIPHY was an international, Phase 3, two-part, open-label study in participants with PKU aged ≥2 years. Participants responsive to sepiapterin (60 mg/kg/day) in Part 1 (≥20% reduction in blood phenylalanine [Phe]) entered Part 2, a crossover treatment period, and were randomized 1:1 to alternative treatment sequences of sepiapterin (60 mg/kg/day, licensed dosage) and sapropterin (20 mg/kg/day, maximum licensed dosage) for 4 weeks each, with a 14-day washout between treatments. The primary endpoint was mean change in blood Phe from baseline to Weeks 3-4 of each treatment period (Part 2).

Results: Of 82 participants enrolled, 67 (81.7%) and 62 (75.6%) had reductions in blood Phe ≥20% and ≥ 30%, respectively, in Part 1. Sixty-two participants were randomized in Part 2 (mean [SD] age, 15.8 [10.8] years). In the primary analysis set (≥30% reduction in blood Phe in Part 1, n = 58), mean (SD) baseline blood Phe before sepiapterin and sapropterin treatment was 725.8 (302.1) and 790.4 (370.0) μmol/L, respectively. Least-squares mean (SE) reduction in blood Phe from baseline was -437.0 (28.0) and - 256.6 (28.2) μmol/L, respectively, representing a least-squares mean difference of -180.4 μmol/L (95% CI: -229.5, -131.4; p < 0.0001) and a relative 70% greater reduction with sepiapterin versus sapropterin. Both treatments were well tolerated, with safety profiles consistent with previous reports.

Conclusions: Sepiapterin was superior to the highest approved dose of sapropterin in lowering blood Phe. No new safety signals were observed. The trial was registered in the UK Clinical Study Registry, ISRCTN, on January 29, 2024 (ID number, ISRCTN79102999; https://www.isrctn.com/ISRCTN79102999).