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BACKGROUNDMetabolic dysfunction-associated steatotic liver disease (MASLD) has a substantial inherited component. Rare variants in apolipoprotein B gene (APOB) have been implicated in susceptibility to liver steatosis, but their role in disease progression and outcomes is unclear.METHODSWe investigated APOB rare variants in a case-control cohort of people with advanced MASLD versus healthy controls (n = 510 and 261, respectively), a family-based study (n = 43 and literature meta-analysis), the Million Veteran Program (MVP) cohort (n = 94,885), and the UK Biobank (UKBB) (n = 417,657).RESULTSIn the clinical cohort, APOB variants were enriched in people with advanced MASLD (OR 13.8, 95% CI: 2.7-70.7, P = 0.002) and associated with lower circulating lipids, but higher MASLD activity and fibrosis (P < 0.05). In the family study, APOB variants segregated with hepatic steatosis and fibrosis (P < 0.05). Cross-ancestry meta-analysis of the study cohorts yielded pooled ORs for cirrhosis and hepatocellular carcinoma (HCC) of 1.82, 95% CI: 1.33-2.49 and 3.53, 95% CI: 2.09-5.98, respectively. Variants affecting specifically ApoB100 had a 3-fold greater effect on hepatic lipid metabolism compared with those impairing also ApoB48 and were specifically protective against coronary artery disease (P < 0.05). The variants affected cirrhosis risk similarly, but ApoB48/100 had a larger effect on HCC (P < 0.05).CONCLUSIONSRare APOB variants predispose individuals to advanced MASLD and HCC, with distinct contributions from disrupted VLDL and chylomicrons secretion. These findings highlight the interplay between hepatic and intestinal lipid handling, suggesting that APOB genotyping may enhance MASLD risk stratification and patient identification.FUNDINGEuropean Union, Italian Ministry of Health, Swedish Research Council, Veterans Health Administration, NIH. Show less

The relationship between plasma lipoprotein(a) [Lp(a)] levels and metabolic dysfunction-associated steatotic liver disease (MASLD) remains unclear. The aim of this study was to examine the combined effects of Lp(a) levels on liver and vascular damage. The study was conducted using the Liver-Bible cohort of individuals with metabolic dysfunction (n = 859, 808 with genomic information) and the Milan Biobank (n = 6963). Genome-wide association studies (GWAS) and polygenic risk scores (PRS) were used to evaluate the inherited factors influencing plasma Lp(a) levels. In the Liver-Bible cohort, genetic variation in the LPA gene was the strongest determinant of Lp(a), followed by liver stiffness measurement (LSM). Additionally, circulating Lp(a) levels, but not genetic predisposition, were inversely related to LSM, suggesting that MASLD severity may affect Lp(a) secretion. Among participants with more severe insulin resistance (n = 250), Lp(a) levels (odds ratio 6.7, 95% CI 1.0-53.0, p = 0.046) and LSM (odds ratio 13.7, 95% CI 1.4-172.2, p = 0.023) were associated with greater prevalence of carotid atherosclerotic plaques, regardless of traditional cardiovascular risk factors. In the Milan Biobank, genetically predicted higher Lp(a) levels tended to increase the risk of liver-related outcomes, whereas genetically predicted MASLD was associated with lower circulating Lp(a) levels. The results of this study suggest that liver damage is more likely the cause of reduced plasma Lp(a) levels rather than a consequence. Assessing plasma Lp(a) levels and the extent of liver damage could improve the prediction of vascular damage. Show less

Men with Klinefelter syndrome (KS) show hypergonadotropic hypogonadism, but the pathogenesis of hypotestosteronemia remains unclear. Testicular steroidogenesis in KS men was evaluated over three decades ago after human chorionic gonadotropin (hCG) stimulation, but inconclusive results were obtained. Intriguingly, some recent studies show increased intratesticular testosterone concentrations in men with KS. To analyze serum steroid profile, as a proxy of testicular steroidogenesis, after hCG stimulation in KS compared with control men. A prospective, longitudinal, case-control, clinical trial. Thirteen KS patients (36±9 years) not receiving testosterone (TS) replacement therapy and 12 eugonadic controls (32±8 years) were enrolled. Serum steroids were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) at baseline and for five consecutive days after intramuscular injection of 5000IU hCG. Progesterone (P), 17-hydroxyprogesterone (17OHP), TS, and estradiol (E2) showed a significant increase (P<0.001) after hCG stimulation in both groups. On the contrary, androstenedione (AS) and dehydroepiandrosterone did not increase after hCG stimulation. The 17OHP/P ratio increased in both groups (P<0.001), the TS/AS ratio (17β-hydroxysteroid dehydrogenase type 3 (17βHSD3) activity) did not increase after hCG in any group, and the E2/TS ratio (aromatase activity) increased significantly in both groups (P=0.009 in KS and P<0.001 in controls). Luteinizing hormone decreased after hCG in both groups (P=0.014 in KS and P<0.001 in controls), whereas follicle-stimulating hormone decreased only in control men (P<0.001). This study demonstrates for the first time using LC-MS/MS that Leydig cells of KS men are able to respond to hCG stimulation and that the first steps of steroidogenesis are fully functional. However, the TS production in KS men is impaired, possibly related to reduced hydroxysteroid deydrogenase activity due to an unfavorable intratesticular metabolic state. Show less