Daily Endocrinology Research Analysis

Obstructive sleep apnea (OSA) is associated with obesity and cardiovascular risk. The SURMOUNT-OSA master protocol comprised two, 52-week, randomized, double-blind, placebo-controlled phase 3 studies (study 1 and study 2) and demonstrated a significant reduction of a number of cardiometabolic risk measures in participants with OSA and obesity following treatment with tirzepatide. Here we report prespecified analysis of cardiometabolic risk measures in SURMOUNT-OSA. Post hoc analyses include changes in a homeostatic model assessment for insulin resistance and mediation analysis to determine the proportion of observed changes attributable to reductions in body weight, apnea-hypopnea index and sleep apnea-specific hypoxic burden. In both study 1 and study 2 of SURMOUNT-OSA, tirzepatide treatment was associated with greater alleviation of cardiometabolic risk factors than placebo. Independent mediation effect of changes in OSA metrics was observed on high-sensitivity C-reactive protein, homeostatic model assessment for insulin resistance and triglycerides. The combination of changes in weight and OSA metrics, as well as weight alone, had a significant mediation effect on systolic blood pressure, but there was no significant mediation effect of weight or OSA metrics observed on diastolic blood pressure. Based on the mediation analysis, treating both sleep-disordered breathing and obesity is likely required to optimize the treatment effect on cardiometabolic benefits for patients with moderate-to-severe OSA and obesity. The ClinicalTrials.gov registration number for this study is NCT05412004 .

Pheochromocytomas and paragangliomas (PPGLs) with SDHB mutations frequently develop metastases, but the molecular mechanisms driving this progression remain unclear. Here we show that SDHB-mutant metastatic PPGLs display an amplified hypermethylation signature, particularly in genes involved in neuronal differentiation, building on previous findings in SDHx-mutated tumors. This epigenetic shift is already detectable in benign SDHB-mutant tumors, suggesting early priming toward a less differentiated state. In parallel, we identify hypomethylation of genes linked to carbohydrate metabolism, notably the fructose transporter SLC2A5. Functional assays reveal that SDHB loss, hypoxia, exogenous succinate, and fructose availability promote tumor cell growth and induce cell-type-restricted, SDHB-dependent, induction of SLC2A5 expression. These findings highlight the dual role of SDHB mutations in driving epigenetic reprogramming and metabolic adaptation, promoting tumor cell plasticity and survival under metabolic stress. By uncovering a fructose-driven metabolic vulnerability, our study provides insights into the molecular mechanisms underlying metastatic PPGLs and identifies potential therapeutic targets at the intersection of epigenetic and metabolic regulation.

Structural variants (SVs) that disrupt topologically associating domains can cause disease by rewiring enhancer-promoter interactions. Duplications involving GPR101 are known to cause X-linked acrogigantism (X-LAG) through ectopic GPR101 expression, but not all of these duplications are pathogenic. This presents a diagnostic challenge, especially in the prenatal setting. We evaluated POSTRE, a tool that predicts the regulatory impact of SVs, to distinguish pathogenic from benign GPR101 duplications. We analyzed seven non-pathogenic duplications and 27 known X-LAG-associated duplications. To enable predictions in an X-LAG-relevant tissue, enhancer maps built using H3K27ac ChIP-seq, ATAC-seq, and RNA-seq data derived from human anterior pituitary samples (NIH research protocol 97-CH-0076, Clinicaltrials.gov Identifier NCT00001595, submitted on 11 March 1999) were integrated into POSTRE. POSTRE correctly classified all 34 duplications as benign or pathogenic. In addition, one X-LAG case with mild clinical features (i.e. severe growth hormone hypersecretion without pituitary tumorigenesis) was found to include only 2/5 VGLL1 enhancers, whereas all typical X-LAG cases had ≥4 enhancers duplicated. This suggests that partial enhancer hijacking at VGLL1 could explain the different clinical features in this individual. These findings support the utility of POSTRE to support diagnostic pipelines when interpreting SVs affecting chromatin architecture in pituitary disease and highlight its potential to reduce uncertainty in genetic counseling without requiring chromatin conformation capture assays.