Daily Endocrinology Research Analysis

BACKGROUND & AIMS: Glycosylated proteins and lipids regulate multiple cellular processes and play key roles in organ damage and regeneration. Recently, glycosylated non-coding small RNAs (glycoRNA) have been identified, however, their expression in the liver and their involvement in hepatic pathology has not yet been reported. METHODS: We detected the presence of glycoRNAs by northern blot and an imaging approach called sialic acid aptamer and RNA in situ hybridization-mediated proximity ligation assay that enables direct visualization of glycoRNAs. Restoration of key mediators of glycoRNA biosynthesis was achieved in vivo, via adeno-associated viral vectors (AAV). RESULTS: Here, we show that glycoRNAs are synthesized in human liver tissue, primary hepatocytes and hepatic tumor cells. In tissues from patients with key features of metabolic dysfunction-associated steatotic liver diseases (MASLD), the most prevalent liver disease worldwide, expression of most glycoRNAs was reduced. Mechanistically, we found that reduced expression of SID1 transmembrane family member 1 (SIDT1) and DTW domain containing 2 (DTWD2), two key mediators of glycoRNA biosynthesis, contribute to loss of glycoRNAs in MASLD. Inhibition of SIDT1 and DTWD2 increased fatty acid load in primary human hepatocytes and enhanced inflammation signals upon co-culture with macrophages. Importantly, AAV-mediated in vivo restoration of SIDT1 and DTWD2 attenuated metabolic dysfunction-associated steatohepatitis (MASH) in mice. Furthermore, sequencing of enriched glycoRNA samples identified eight glycoRNAs, which were downregulated in steatotic human liver and hepatocytes. CONCLUSIONS: Collectively, our study demonstrates the presence of glycoRNAs in human hepatocytes and human liver tissues and their dysregulated expression in experimental steatosis models and in MASLD patients. IMPACT AND IMPLICATIONS: Recent estimates suggest that up to 24% of the world's population is affected by metabolic dysfunction-associated steatotic liver diseases (MASLD). Our study reports for the first time that glycosylated RNAs (glycoRNA), a recently discovered class of RNA, are present in the liver and their expression is dysregulated in fatty liver injury. Importantly, in vivo restoration of glycoRNA biogenesis, attenuated fatty liver injury in preclinical models of MASLD. Furthermore, our results suggest that glycoRNA expression is dysregulated in human livers with MASLD, indicating their potential as novel biomarkers of liver injury.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is increasingly recognized as an independent risk factor for cardiovascular disease (CVD), yet the underlying molecular pathways mediating liver-to-vasculature communication remain largely unidentified. Here we show that extracellular vesicles (EVs) derived from hepatocytes contribute to endothelial dysfunction and atherogenesis. Treatment with EVs derived from palmitic acid (PA)-treated hepatocytes induced inflammation and endothelial dysfunction in human endothelial cells. miR-30b-5p was identified as a candidate cargo, and its elevation was confirmed by qPCR in EVs from PA-treated hepatocytes and western diet-induced steatotic livers. ELOVL5 (elongation of very long chain fatty acid protein 5), a key enzyme involved in fatty acid elongation, was identified as a direct target of miR-30b-5p. Overexpression of miR-30b-5p or knockdown of Elovl5 inhibited the elongation of polyunsaturated fatty acids (PUFAs), leading to endothelial inflammation, which was rescued by PUFA supplementation. In vivo, overexpression of miR-30b-5p accelerated atherogenesis, whereas its inhibition ameliorated vascular lesions. miR-30b-5p levels in human serum-derived EVs positively correlated with the early-stage MASLD indices. Our findings identify EV-derived miR-30b-5p/ELOVL5 axis as a novel mechanistic link between MASLD and CVD. miR-30b-5p may function as both a biomarker and a therapeutic target for early intervention of CVD among patients with MASLD.

IMPORTANCE: Spermatogenic failure (SPGF) is a severe form of male infertility with limited evidence-based medical treatment options. Aromatase inhibitors represent a promising therapeutic strategy for SPGF, but high-quality evidence is lacking. OBJECTIVE: To evaluate the efficacy and safety of letrozole for improving sperm concentration categories in men with SPGF. DESIGN, SETTING, AND PARTICIPANTS: This multicenter, open-label, assessor-blinded randomized clinical trial was conducted at 10 male infertility centers in China from July 2023 to March 2024. Men with SPGF (nonobstructive azoospermia [NOA], cryptozoospermia, or severe oligozoospermia) were enrolled. Follow-up for the primary outcome was completed in June 2024. Data were analyzed from July 2024 to March 2025. INTERVENTIONS: Participants were randomized to receive letrozole (2.5 mg daily) plus vitamins C and E or vitamins C and E alone (control group) for 3 months. MAIN OUTCOMES AND MEASURES: The primary outcome was World Health Organization Sperm Concentration Categories (WHO-SCC) upgrade rate at 3 months after randomization. The secondary outcomes were WHO-SCC grades, Dutch Society of Obstetrics and Gynecology Total Motile Sperm Count Categories (NVOG-TMSCC) upgrade rate, semen parameters, and reproductive hormone levels. RESULTS: Among 296 participants (mean [SD] age, 30.2 [3.9] years; 218 [73.6%] with NOA; 147 randomized to the letrozole group and 149 to the control group), 247 (83.4%) completed the trial, and all 296 were included in the primary analysis. WHO-SCC upgrade rates were 14.3% (21 of 147 participants) with letrozole vs 5.4% (8 of 149 participants) with control (risk difference, 9.2% [95% CI, 2.5%-15.8%]; P = .01). Participants in the letrozole group had higher odds of achieving a better WHO-SCC grade than those in the control group (common odds ratio, 2.65 [95% CI, 1.28-5.47]; P = .008). The NVOG-TMSCC upgrade rate was also higher with letrozole. Letrozole significantly increased serum gonadotropins and testosterone while decreasing estradiol. There were no significant between-group differences in semen parameters. Decreased libido (18 [12.2%] vs 8 [5.4%]; P = .04) was more frequent with letrozole than with control. CONCLUSIONS AND RELEVANCE: In this randomized clinical trial of men with spermatogenic failure, letrozole significantly improved sperm concentration categories and was well tolerated, supporting its use as an option to downstage infertility severity and potentially enable less invasive reproductive management. TRIAL REGISTRATION: chictr.org.cn Identifier: ChiCTR2300073861.