👤 Chin Kook Rhee

Dysregulated actions of the bone-derived phosphaturic hormone, fibroblast growth factor-23 (FGF23), underlie the pathophysiology of several diseases. FGF23 is synthesized primarily in osteocytes in response to various endogenous molecules; however, the mechanisms governing FGF23 production are incompletely understood. Glycerol-3-phosphate (G3P), a glycolytic by-product originating from the kidney, critically controls skeletal FGF23 synthesis via its conversion in bone to lysophosphatidic acid (LPA), which stimulates osteocyte FGF23 production. The bioactive vitamin D, 1,25-dihydroxyvitamin D (1,25D), also promotes FGF23 production in osteocytes. We herein demonstrated that LPA requires 1,25D action to raise FGF23 levels in mouse bone explants and mice. RNA sequencing of osteocyte-like Ocy454 cells identified differentially expressed genes (DEGs) uniquely induced by LPA/1,25D co-treatment. These unique DEGs were enriched for the ribosome biogenesis pathway. DEGs concurrently induced by individual LPA and 1,25D treatments were enriched for MAPK signaling, and inhibiting this pathway obliterated LPA/1,25D-induced FGF23 production. DEGs following LPA/1,25D co-treatment were enriched for the cytokine-cytokine receptor interaction pathway. Moreover, LPA/1,25D co-treatment, but not individual LPA and 1,25D treatments, rapidly induced the expression of Il12a, the gene encoding the pro-inflammatory cytokine interleukin-12 alpha-subunit, which responded solely to 1,25D at later times and required MAPK-ERK1/2 signaling. Inhibiting cytokine signaling or knocking down Il12a inhibited, while overexpressing Il12a enhanced LPA/1,25D-induced FGF23 production. However, challenging Ocy454 cells with recombinant bioactive interleukin-12 failed to enhance FGF23 production, suggesting that Il12a plays a noncanonical role. Our results reveal a mechanism of skeletal FGF23 synthesis involving synergistic actions of LPA and 1,25D, advancing our understanding of FGF23 regulation. Show less

Lipoprotein(a) [Lp(a)] is a genetically determined, independent risk factor for atherosclerotic cardiovascular disease. However, its role in coronary artery calcification (CAC) remains unclear. We aimed to determine whether Lp(a) levels are associated with the incidence and progression of CAC. We conducted a longitudinal cohort study (2015-22) of 41 929 adults (aged ≥30 years) who underwent baseline Lp(a) measurement and CAC assessment via multi-detector computed tomography. Participants were stratified into those with baseline CAC = 0 (n = 32 338) and CAC > 0 (n = 9591). Outcomes were analysed according to Lp(a) quintiles and clinically relevant categories (<30, 30-50, 50-100, ≥ 100 mg/dL). Cox proportional hazards models estimated hazard ratios (HRs) for incident CAC (CAC > 0) among those with CAC = 0 (median follow-up, 4.04 years). Linear mixed-effects models evaluated CAC progression among those with CAC > 0 (median follow-up, 3.78 years). All models were adjusted for cardiovascular risk factors. Among participants with CAC = 0 (mean age, 40.94 ± 5.81 years; 85.69% men), neither Lp(a) quintiles nor clinical categories were significantly associated with incident CAC [HR for highest vs. second quintile: 0.998 (95% confidence interval, CI, 0.90-1.10); HR for ≥100 vs. <30 mg/dL: 0.83 (95% CI, 0.57-1.23)]. Among those with CAC > 0 (mean age, 45.99 ± 7.20 years; 94.90% men), CAC progression did not differ materially across Lp(a) quintiles or clinical thresholds. Elevated Lp(a) levels were not associated with new-onset CAC or progression of existing CAC in this large longitudinal cohort. Show less

Dyslipidemia remains a central modifiable risk factor for atherosclerotic cardiovascular disease (ASCVD). While 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, commonly known as statins, as well as ezetimibe, fibrates, and omega-3 fatty acids have established roles in lipid lowering, significant residual risk persists in many patients due to insufficient low-density lipoprotein cholesterol (LDL-C) reduction, elevated triglyceride-rich lipoproteins, and genetically determined elevations of lipoprotein(a) (Lp(a)). Recent years have witnessed remarkable advances in therapeutic modalities, including next-generation small molecules, monoclonal antibodies, protein-based infusions, and ribonucleic acid (RNA)-based strategies. These agents target diverse pathways such as proprotein convertase subtilisin/kexin type 9 (PCSK9), angiopoietin-like protein 3 (ANGPTL3), apolipoprotein C-III, apolipoprotein B, cholesteryl ester transfer protein (CETP), and Lp(a), achieving potent lipid modulation with improved convenience and safety. Clinical outcome trials have validated bempedoic acid, PCSK9 inhibitors, and icosapent ethyl, while large-scale programs are ongoing for obicetrapib, oral PCSK9 inhibitors, Lp(a)-targeted oligonucleotides, and ANGPTL3-directed RNA therapeutics. This review summarizes the mechanisms, pivotal trials, and clinical implications of innovative lipid-lowering therapies, highlighting how they may reshape future treatment algorithms for ASCVD prevention. Show less

Previous studies suggest associations between the risk of developing chronic obstructive pulmonary disease (COPD) and adiponectin/leptin (ALR) and apolipoprotein B/A1 (APOR) ratios. This longitudinal observational study, using data from the Korean Genome and Epidemiology Study (KoGES), examined the rate of lung function decline, risk factors for the airflow obstruction (AFO), and the time to first AFO based on ALR and APOR groups. Among 5578 participants, high ALR and low APOR were associated with rapid decline in lung function and a shorter time to the first AFO. The high ALR group and the combined high ALR and low APOR group showed higher risk of experiencing AFO both at least once (RR 1.46, 95% CI 1.12-1.90; RR 1.74, 95% CI 1.23-2.46, respectively) and at the final follow up (RR 1.44, 95% CI 1.05-1.96; RR 1.72, 95% CI 1.14-2.60, respectively). High ALR and the combined high ALR and low APOR were identified as risk factors for earlier time to first AFO. This study highlights the potential of ALR and APOR as makers for predicting the risk of future airflow obstruction. Show less

Common genetic variants in glucokinase regulator (GCKR), which encodes GKRP, a regulator of hepatic glucokinase (GCK), influence multiple metabolic traits in genome-wide association studies (GWASs), making GCKR one of the most pleiotropic GWAS loci in the genome. It is unclear why. Prior work has demonstrated that GCKR influences the hepatic cytosolic NADH/NAD Show less

Eicosanoids are biologically active derivatives of polyunsaturated fatty acids with broad relevance to health and disease. We report a genome-wide association study in 8406 participants of the Atherosclerosis Risk in Communities Study, identifying 41 loci associated with 92 eicosanoids and related metabolites. These findings highlight loci required for eicosanoid biosynthesis, including FADS1-3, ELOVL2, and numerous CYP450 loci. In addition, significant associations implicate a range of non-oxidative lipid metabolic processes in eicosanoid regulation, including at PKD2L1/SCD and several loci involved in fatty acyl-CoA metabolism. Further, our findings highlight select clearance mechanisms, for example, through the hepatic transporter encoded by SLCO1B1. Finally, we identify eicosanoids associated with aspirin and non-steroidal anti-inflammatory drug use and demonstrate the substantial impact of genetic variants even for medication-associated eicosanoids. These findings shed light on both known and unknown aspects of eicosanoid metabolism and motivate interest in several gene-eicosanoid associations as potential functional participants in human disease. Show less

Metabolomics genome wide association study (GWAS) help outline the genetic contribution to human metabolism. However, studies to date have focused on relatively healthy, population-based samples of White individuals. Here, we conducted a GWAS of 537 blood metabolites measured in the Chronic Renal Insufficiency Cohort (CRIC) Study, with separate analyses in 822 White and 687 Black study participants. Trans-ethnic meta-analysis was then applied to improve fine-mapping of potential causal variants. Mean estimated glomerular filtration rate was 44.4 and 41.5 mL/min/1.73m Show less

Depression is a common symptom of many mental disorders, especially major depressive disorder (MDD) and bipolar disorder (BD). Previous studies have reported that these diseases share common pathophysiological pathways; therefore, this study elucidated whether the plasma levels of protein markers related to common depressive symptoms differed between patients with BD and those with MDD. Plasma samples of 71 patients with mood disorders and clinical manifestations were analyzed in this study. After depleting the abundant proteins, liquid chromatography-tandem mass spectrometry and label-free quantification were performed. Five proteins, viz., cholesteryl ester transfer protein (CETP), apolipoprotein D (APOD), mannan-binding lectin serine protease 2 (MASP2), Ig lambda chain V-II region BO (IGLV2-8) and Ig kappa chain V-III region NG9 (IGKV3-20) were negatively associated with the total scores of the Hamilton depression rating scale (HAM-D), after adjusting for the covariates. CETP and APOD also showed significant negative correlations with the anhedonia/retardation and guilt/agitation scores of the HAM-D. Four proteins, namely, Ig kappa chain V-II region TEW (IGKC; IGKV2D-28), Ig lambda variable 5-45 (IGLV5-45), complement factor H (CFH) and attractin (ATRN), showed significant associations with anhedonia/retardation after adjusting for covariates. Proteins that significantly correlated with the symptoms could predict the remission state of depression (area under the curve [AUC], 0.83) and anhedonia/retardation (AUC, 0.80). Bioinformatics analysis revealed that complement activation, immune response, and lipid metabolism were significantly enriched pathways. Although our study design was cross-sectional and no controls were included, protein markers identified in this preliminary study will be further investigated in our subsequent longitudinal study. Show less

Metabolic syndrome (MetS) which is caused by obesity and insulin resistance, is well known for its predictive capability for the risk of type 2 diabetes mellitus and cardiovascular disease. The development of MetS is associated with multiple genetic factors, environmental factors and lifestyle. We performed a genome-wide association study to identify single-nucleotide polymorphism (SNP) related to MetS in large Korean population based samples of 1,362 subjects with MetS and 6,061 controls using the Axiom® Korean Biobank Array 1.0. We replicated the data in another sample including 502 subjects with MetS and 1,751 controls. After adjusting for age and sex, rs662799 located in the APOA5 gene were significantly associated with MetS. 15 SNPs in GCKR, C2orf16, APOA5, ZPR1, and BUD13 were associated with high triglyceride (TG). 14 SNPs in APOA5, ALDH1A2, LIPC, HERPUD1, and CETP, and 2 SNPs in MTNR1B were associated with low high density lipoprotein cholesterol (HDL-C) and high fasting blood glucose respectively. Among these SNPs, 6 TG SNPs: rs1260326, rs1260333, rs1919127, rs964184, rs2075295 and rs1558861 and 11 HDL-C SNPs: rs4775041, rs10468017, rs1800588, rs72786786, rs173539, rs247616, rs247617, rs3764261, rs4783961, rs708272, and rs7499892 were first discovered in Koreans. Additional research is needed to confirm these 17 novel SNPs in Korean population. Show less

Diastolic dysfunction (DD) is common among hypertrophic cardiomyopathy (HCM) patients, causing major morbidity and mortality. However, its cellular mechanisms are not fully understood, and presently there is no effective treatment. Patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) hold great potential for investigating the mechanisms underlying DD in HCM and as a platform for drug discovery. In the present study, beating iPSC-CMs were generated from healthy controls and HCM patients with DD. Micropatterned iPSC-CMs from HCM patients showed impaired diastolic function, as evidenced by prolonged relaxation time, decreased relaxation rate, and shortened diastolic sarcomere length. Ratiometric Ca2+ imaging indicated elevated diastolic [Ca2+]i and abnormal Ca2+ handling in HCM iPSC-CMs, which were exacerbated by β-adrenergic challenge. Combining Ca2+ imaging and traction force microscopy, we observed enhanced myofilament Ca2+ sensitivity (measured as dF/Δ[Ca2+]i) in HCM iPSC-CMs. These results were confirmed with genome-edited isogenic iPSC lines that carry HCM mutations, indicating that cytosolic diastolic Ca2+ overload, slowed [Ca2+]i recycling, and increased myofilament Ca2+ sensitivity, collectively impairing the relaxation of HCM iPSC-CMs. Treatment with partial blockade of Ca2+ or late Na+ current reset diastolic Ca2+ homeostasis, restored diastolic function, and improved long-term survival, suggesting that disturbed Ca2+ signalling is an important cellular pathological mechanism of DD. Further investigation showed increased expression of L-type Ca2+channel (LTCC) and transient receptor potential cation channels (TRPC) in HCM iPSC-CMs compared with control iPSC-CMs, which likely contributed to diastolic [Ca2+]i overload. In summary, this study recapitulated DD in HCM at the single-cell level, and revealed novel cellular mechanisms and potential therapeutic targets of DD using iPSC-CMs. Show less

ANGPTL8 is a liver-derived secretory protein that leads to elevated serum triglyceride and the level of circulating ANGPTL8 is strongly associated with obesity and diabetes. Here we investigated the mechanisms of activation and inhibition of ANGPTL8 expression in hepatocytes. The expression of ANGPTL8 was significantly increased in HepG2 cells exposed to palmitic acid, tunicamycin, or T0901317, and was reversed in cells treated with AICAR. Palmitic acid, tunicamycin, and T0901317 increased LXRα and SREBP-1c mRNA expression. The inhibitory effect of AICAR on the expression of T0901317-induced ANGPTL8 was most strongly evident in cells that were transfected with SREBP-1 siRNA. AICAR increased phosphorylation of PPARα and the effect of AICAR was not observed in cells treated with PPARα inhibitor. Metformin had a similar effect on ANGPTL8 expression to that of AICAR. These data suggest that AMPK can suppress the expression of LXR/SREBP-1 signal-induced ANGPTL8 in HepG2 cells. Show less

Centriolar satellites are PCM-1-positive granules surrounding centrosomes. Proposed functions of the centriolar satellites include protein targeting to the centrosome, as well as communication between the centrosome and surrounding cytoplasm. CEP90 is a centriolar satellite protein that is critical for spindle pole integrity in mitotic cells. In this study, we examined the biological functions of CEP90 in interphase cells. CEP90 physically interacts with PCM-1 at centriolar satellites, and this interaction is essential for centrosomal accumulation of the centriolar satellites and eventually for primary cilia formation. CEP90 is also required for BBS4 loading on centriolar satellites and its localization in primary cilia. Our results imply that the assembly and transport of centriolar satellites are critical steps for primary cilia formation and ciliary protein recruitment. Show less