👤 Yehuda Handelsman

Obicetrapib is a next-generation, oral, selective cholesteryl ester transfer protein inhibitor known to significantly affect atherogenic lipoproteins, including low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (ApoB), nonhigh-density lipoprotein cholesterol (Non-HDL-C), and lipoprotein(a) [Lp(a)]. To evaluate the lipid-lowering efficacy of obicetrapib based on available evidence. This systematic review was drafted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive literature search was conducted to identify randomized clinical trials assessing the lipid-lowering effects of obicetrapib compared to placebo. Fixed and random-effects models were used. Five randomized clinical trials (n = 288 patients) were included in this analysis. Patients treated with obicetrapib exhibited significantly greater reductions in LDL-C (mean difference [MD]: 41.4% [95% CI: 45.7 to -37.1]; I²: 6%), ApoB (MD: 26.5% [95% CI: 31.3 to -21.6]; I²: 45%), and Non-HDL-C (MD: 34.5% [95% CI: 37.0 to -31.6]; I²: 80%) compared to those receiving a placebo. Additionally, HDL-C levels were significantly higher in the obicetrapib group (MD: 157.4% [95% CI: 142.2 to 172.6]; I²: 69%). While triglyceride levels did not differ significantly between the 2 groups, Lp(a) levels were notably reduced with obicetrapib treatment (MD: 39.5% [95% CI: 54.6 to -24.3]; I²: 67%). Obicetrapib is associated with significant reductions in key atherogenic lipoproteins, including LDL-C, ApoB, Non-HDL-C and Lp(a). Further investigation is needed to assess its impact on cardiovascular risk. Show less

Historically, 17β-hydroxysteroid dehydrogenase type 3 (HSD17B3) was thought to be the key enzyme responsible for testicular testosterone production. In humans, loss-of-function mutations in HSD17B3 impair testosterone production during prenatal life leading to impaired development of androgen-dependent tissues in 46,XY individuals. However, male mice with HSD17B3 deficiency exhibit normal testicular testosterone concentrations, normal development of reproductive organs and are fertile, suggesting that mice express other hydroxysteroid dehydrogenase enzymes capable of testicular testosterone synthesis. This study aimed to investigate whether 17β-hydroxysteroid dehydrogenase type 12 (HSD17B12), which can convert androstenedione to testosterone in mice but not in humans, compensates for the lack of HSD17B3 in Hsd17b3 knockout (KO) mice. We used CRISPR/Cas9 to substitute the amino acid in mouse HSD17B12 that is responsible for its ability to convert androstenedione to testosterone with the amino acid of the human enzyme that prevents androstenedione being used as a substrate. When this Hsd17b12 mutation was introduced into Hsd17b3 KO mice, males exhibited normal reproductive tracts but reduced testicular testosterone production with a consequential reduction in seminal vesicle weight. This suggests HSD17B12 contributes toward testosterone production in the absence of HSD17B3, but other enzymes must also contribute. We therefore quantified other testicular hydroxysteroid dehydrogenases, finding that HSD17B7 mRNA and protein was markedly upregulated in Hsd17b3 KO testes. We confirmed that mouse, but not human, HSD17B7 can produce testosterone in vitro. We conclude that compared to humans, mice exhibit increased plasticity in testosterone production via hydroxysteroid dehydrogenase enzymes to support androgen action and male fertility. Show less

We determined the functional role of the Sertoli cell glucocorticoid receptor (GR) in vivo using a transgenic Cre-loxP approach to conditionally disrupt GR expression. Sertoli cell GR knockout (SCGRKO) was shown by absent Sertoli cell-specific GR immunolocalization and reduced levels of glucocorticoid-responsive Stc1 and Tsc22d3 mRNA in SCGRKO relative to control testes. Adult SCGRKO testes exhibited distinct morphological changes, including reduced seminiferous tubular lumen formation, decreased total Sertoli cell numbers, and parallel reductions in meiotic spermatocyte and postmeiotic spermatid numbers. Conversely, tubular diameter was increased and testis size was normal in SCGRKO males. Decreased serum FSH and testicular Fshr mRNA levels were consistent with reduced Sertoli cell number. Adult SCGRKO testes also displayed atypical germ cells and interstitial focal accumulations of hypertrophic lipid-laden, immature-like Leydig cells. Circulating LH, and testicular Lhr mRNA, testosterone, dihydrotestosterone, and 3α/3β-diol levels were all reduced in mature SCGRKO mice, whereas serum testosterone and dihydrotestosterone levels remained normal. Moreover, Sertoli cell GR disruption caused differential changes to steroidogenic enzyme transcripts, with down-regulated testicular Cyp11a1 contrasting with up-regulated Hsd17b3 expression. Reduced SCGRKO testicular expression of Hsd11b2, encoding an enzyme for corticosterone inactivation, supports a dynamic coupling between Hsd11b and androgen production. Our novel SCGRKO model has revealed that Sertoli cell-mediated GR actions support normal testicular function. Sertoli cell GR is required to maintain normal testicular Sertoli/germ cell numbers and circulating gonadotropin levels, as well as optimal Leydig cell maturation and steroidogenesis, providing new insight into gluocorticoid-mediated impact on male reproduction. Show less