Updated mechanisms of MASLD pathogenesis.

Metabolic dysfunction-associated steatotic liver disease (MASLD) has garnered considerable attention globally. Changing lifestyles, over-nutrition, and physical inactivity have promoted its development. MASLD is typically accompanied by obesity and is strongly linked to metabolic syndromes. Given that MASLD prevalence is on the rise, there is an urgent need to elucidate its pathogenesis. Hepatic lipid accumulation generally triggers lipotoxicity and induces MASLD or progress to metabolic dysfunction-associated steatohepatitis (MASH) by mediating endoplasmic reticulum stress, oxidative stress, organelle dysfunction, and ferroptosis. Recently, significant attention has been directed towards exploring the role of gut microbial dysbiosis in the development of MASLD, offering a novel therapeutic target for MASLD. Considering that there are no recognized pharmacological therapies due to the diversity of mechanisms involved in MASLD and the difficulty associated with undertaking clinical trials, potential targets in MASLD remain elusive. Thus, this article aimed to summarize and evaluate the prominent roles of lipotoxicity, ferroptosis, and gut microbes in the development of MASLD and the mechanisms underlying their effects. Furthermore, existing advances and challenges in the treatment of MASLD were outlined.

Diagnostic Performance of Angiography-Derived Quantitative Flow Ratio in Complex Coronary Lesions.

BACKGROUND: Quantitative flow ratio derived from computed tomography angiography (CT-QFR) and invasive coronary angiography (Murray law-based quantitative flow ratio [µQFR]) are novel approaches enabling rapid computation of fractional flow reserve without the use of pressure guidewires and vasodilators. However, the feasibility and diagnostic performance of both CT-QFR and µQFR in evaluating complex coronary lesions remain unclear. METHODS: Between September 2014 and September 2021, 240 patients with 30% to 90% coronary diameter stenosis who underwent both coronary computed tomography angiography and invasive coronary angiography with fractional flow reserve within 60 days were retrospectively enrolled. The diagnostic performance of CT-QFR and µQFR in detecting functional ischemia among all lesions, especially complex coronary lesions, was analyzed using fractional flow reserve as the reference standard. RESULTS: CT-QFR and µQFR analyses were performed on 309 and 289 vessels, respectively. The diagnostic sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for CT-QFR in all lesions at the per-vessel level were 91% (with a 95% CI of 84%-96%), 92% (95% CI, 88%-95%), 83% (95% CI, 75%-90%), 96% (95% CI, 93%-98%), and 92% (95% CI, 88%-95%), with values for µQFR of 90% (95% CI, 81%-95%), 97% (95% CI, 93%-99%), 92% (95% CI, 84%-97%), 96% (95% CI, 92%-98%), and 94% (95% CI, 91%-97%), respectively. Among bifurcation, tandem, and moderate-to-severe calcified lesions, the diagnostic values of CT-QFR and µQFR showed great correlation and agreement with those of invasive fractional flow reserve, achieving an area under the receiver operating characteristic curve exceeding 0.9 for each complex lesion at the vessel level. Furthermore, the accuracies of CT-QFR and µQFR in the gray zone were 85% and 84%, respectively. CONCLUSIONS: Angiography-derived quantitative flow ratio (CT-QFR and µQFR) demonstrated remarkable diagnostic performance in complex coronary lesions, indicating its pivotal role in the management of patients with coronary artery disease.

Transcatheter Aortic Valve Replacement for Pure Native Aortic Valve Regurgitation: A Systematic Review.

BACKGROUND: Transcatheter aortic valve replacement (TAVR) is a recent and an effective treatment option for high- or extreme-surgical-risk patients with symptomatic severe aortic stenosis. However, pure severe native aortic valve regurgitation (NAVR) without aortic stenosis remains a contraindication to TAVR. The aim of our systemic review analysis was to evaluate TAVR in patients with pure NAVR. METHODS: We searched the published articles in the PubMed and Web of Science databases (2002-2017) using the Boolean operators for studies of NAVR patients undergoing TAVR. Reference lists of all returned articles were searched recursively for other relevant citations. Pooled estimates were calculated using a random-effects meta-analysis. RESULTS: Finally, a total of 10 studies were included in this analysis. The CoreValve was more frequently used with a lower rate of device success and a higher rate of residual aortic regurgitation. The new-generation transcatheter heart valves (THVs) performed a significantly higher rate with less residual aortic regurgitation and a success rate close to 100%. The 30-day all-cause mortality rates ranged from 0 to 30% with an estimate summary rate of 9% (95% CI: 5-15%; I2 = 33%). Cerebrovascular events, major or life-threatening bleeding, major vascular complications, acute kidney disease, and new permanent pacemaker implantation occurred similarly in both the new- and old-generation THV devices. CONCLUSIONS: Aortic regurgitation remains a challenging pathology for TAVR. TAVR is a feasible and reasonable option for carefully selected patients with pure aortic regurgitation.

Predictors of Thrombocytopenia after Self-Expandable Transcatheter Aortic Valve Replacement: A Single-Center Experience from China.

OBJECTIVES: The importance of thrombocytopenia (TP) has been discussed previously. However, data are still limited, especially on predictors of TP. We sought to investigate predictors of TP after transcatheter aortic valve replacement (TAVR), in particular, clinically significant TP. METHODS: We reviewed a total of 123 consecutive patients undergoing TAVR in our medical center. They were stratified into 3 groups according to the nadir platelet count post-TAVR: no/mild TP, moderate TP, and severe TP. Clinically significant TP, also known as major TP, was defined as moderate-to-severe TP (a nadir platelet count <100 × 109/L and a >50% decrease in platelet count). RESULTS: Baseline platelet, baseline hemoglobin, general anesthesia (GA), valve malpositioning and post-TAVR left ventricular ejection fraction were found to be predictors of post-TAVR nadir platelet count. Major TP was associated with a higher risk of major bleeding (OR 3.524, 95% CI 1.546-8.031) and 1-month mortality (OR 11.226, 95% CI 1.208-104.328). Age (OR 1.110, 95% CI 1.014-1.215) and GA (OR 6.494, 95% CI 2.058-20.408) were predictors of major TP. CONCLUSION: Post-TAVR nadir platelet count can be predicted based on baseline and procedural data. Old age and GA contribute to clinically significant TP.

Targeted next-generation sequencing identified ADAMTS5 as novel genetic substrate in patients with bicuspid aortic valve.

BACKGROUND: Bicuspid Aortic Valve (BAV) is the most common congenital heart disease, affecting >1% of the general population. Up to date, three genes, NOTCH1, GATA5 and SMAD6, have been linked to the isolated form of BAV. However, potential genetic determinants remain largely unknown in most BAV patients. MATERIAL AND METHODS: Targeted next-generation sequencing of 7 BAV candidate genes (NOTCH1, GATA5, SMAD6, NOS3, ADAMTS5, Alk2 and SMAD2) was performed in 32 BAV patients. Additional 35 BAV patients and 238 tricuspid aortic valve (TAV) patients, consisting of 107 patients from the transcatheter aortic valve implantation (TAVI) registry and 131 patients from the coronary artery disease (CAD) registry, were selected for further genotyping. RESULTS: We found 2 rare non-synonymous variants in 2/7 genes in 3 BAV patients: one was NOTCH1:c.4297G>A and the other one was ADMTS5:c.935C>A that shared by two patients. NOTCH1:c.4297G>A has not been reported previously. ADMTS5:c.935C>A was predicted to be pathogenic by all applied algorithms. Alignment of protein sequences from all available species revealed that ADMTS5:p.Arg312Leu, produced by ADMTS5:c.935C>A, is located in a highly conserved region. The minor allele frequency of ADMTS5:c.935C>A in BAV patients was significantly higher than the matched population in TAV group (0.015 vs. 0, P=0.048). CONCLUSION: Our results suggested that ADMTS5:c.935C>A are potentially associated with BAV. Further studies, such as large sample case-control replication test and functional research, are needed to explore the role of this rare variant in the development of BAV.

Meta-analysis of Predictors of Early Severe Bleeding in Patients Who Underwent Transcatheter Aortic Valve Implantation.

Severe bleeding (SB) in patients who underwent transcatheter aortic valve implantation (TAVI) could be fatal. Although multiple independent predictors of bleeding post-TAVI have been identified, the definitions of bleeding and predictors vary across studies. This study aimed to provide summary effect estimates for predictors of SB within 30 days post-TAVI. A systematic review of studies that reported the incidence of bleeding post-TAVI with raw data for predictors of interest was performed. Data on characteristics of study, patient, and procedure were extracted. Crude risk ratios (RRs) and 95% confidence intervals were calculated using random-effect model. Fifteen predictors on 65,209 patients from 47 studies were analyzed. The median rate of SB was 11% across studies. Seven factors (3 patient related and 4 procedure related) were recognized as predictors of early SB post-TAVI. Age ≥90 years (RR 1.17; p = 0.008), female (RR 1.13; p = 0.01), and sheath diameter >19 Fr (RR 1.19; p = 0.04) were weak predictors. Chronic kidney disease (RR 1.94; p <0.001) and transapical (TA) (RR 1.82; p <0.001) were moderate predictors that were almost associated with twofold risk. Vascular complication (RR 2.97; p <0.001) and circulatory support (RR 3.39; p <0.001) were strong predictors that were nearly associated with threefold risk. In conclusion, age, gender, chronic kidney disease, TA, sheath diameter, vascular complication, and circulatory support were all predictors of early SB post-TAVI in this meta-analysis, which provided possible guidance for prevention and management of SB related to TAVI.

Meta-Analysis of Impact of Diabetes Mellitus on Outcomes After Transcatheter Aortic Valve Implantation.

To date, the impact of diabetes mellitus (DM) on prognosis after transcatheter aortic valve implantation (TAVI) is still contradictory and thus merits further investigation. The purpose of this meta-analysis was to evaluate the impact of DM on outcomes after TAVI. A systematic search of the PubMed database was performed. Primary end points were 30-day and 1-year all-cause mortality after TAVI. Risk ratios (RRs) and 95% CIs were calculated using the random-effect or fixed-effect model, depending on heterogeneity between studies, and p values <0.05 was considered significant. A total of 16 studies involving 13,253 patients were included in our meta-analysis. There was no significant difference between the groups with DM and without DM regarding 30-day (RR 1.07, 95% CI 0.90 to 1.27, p = 0.45) or 1-year (RR 1.04, 95% CI 0.94 to 1.15, p = 0.42) all-cause mortality. The risks of 30-day complications, including myocardial infarction, stroke, major vascular complications, major bleeding, and acute kidney injury, were similar between patients with and without DM. In conclusion, DM neither affected short- or mid-term all-cause mortality nor short-term complications after TAVI.

Meta-Analysis of Outcomes and Evolution of Pulmonary Hypertension Before and After Transcatheter Aortic Valve Implantation.

Pulmonary hypertension (PH) is a common entity in patients with severe aortic stenosis (AS) who underwent transcatheter aortic valve implantation (TAVI), but its role on clinical outcomes remains undetermined. We evaluated the impact of baseline and postprocedural PH on clinical outcomes and changes in pulmonary artery systolic pressure after TAVI by performing a meta-analysis of 16 studies enrolling 9,204 patients with AS who underwent TAVI. In patients with baseline PH, all-cause mortality was significantly increased, as shown by pooled odds ratio (ORs) for overall 30-day (OR 1.52, 95% confidence interval [CI] 1.28 to 1.80), 1-year (OR 1.39, 95% CI 1.27 to 1.51), and 2-year all-cause mortality (OR 2.00, 95% CI 1.49 to 2.69), compared with those without PH, independent of different methods of PH assessment. The presence of post-TAVI PH was associated with a significant increase in 2-year all-cause mortality (OR 2.32, 95% CI 1.43 to 3.74). Nevertheless, pulmonary artery systolic pressure decreased at 3-month to 1-year follow-up (standardized mean difference -1.12, 95% CI -1.46 to -0.78). Baseline PH was associated with higher 30-day and 1-year cardiovascular mortality. Patients with baseline PH had higher risk of stroke at 1 year and acute kidney injury at 30 days. But the risk of major vascular complications was significantly lower in patients with baseline PH. In conclusion, the presence of PH is associated with increased short- and long-term mortality, also higher risk of stroke and acute kidney injury after TAVI. A significant decrease in PSAP is detected in patients with AS in midterm follow-up after TAVI.

Profound Actions of an Agonist of Growth Hormone-Releasing Hormone on Angiogenic Therapy by Mesenchymal Stem Cells.

OBJECTIVE: The efficiency of cell therapy is limited by poor cell survival and engraftment. Here, we studied the effect of the growth hormone-releasing hormone agonist, JI-34, on mesenchymal stem cell (MSC) survival and angiogenic therapy in a mouse model of critical limb ischemia. APPROACH AND RESULTS: Mouse bone marrow-derived MSCs were incubated with or without 10(-8) mol/L JI-34 for 24 hours. MSCs were then exposed to hypoxia and serum deprivation to detect the effect of preconditioning on cell apoptosis, migration, and tube formation. For in vivo tests, critical limb ischemia was induced by femoral artery ligation. After surgery, mice received 50 µL phosphate-buffered saline or with 1×10(6) MSCs or with 1×10(6) JI-34-reconditioned MSCs. Treatment of MSCs with JI-34 improved MSC viability and mobility and markedly enhanced their capability to promote endothelial tube formation in vitro. These effects were paralleled by an increased phosphorylation and nuclear translocation of signal transducer and activator of transcription 3. In vivo, JI-34 pretreatment enhanced the engraftment of MSCs into ischemic hindlimb muscles and augmented reperfusion and limb salvage compared with untreated MSCs. Significantly more vasculature and proliferating CD31(+) and CD34(+) cells were detected in ischemic muscles that received MSCs treated with JI-34. CONCLUSIONS: Our studies demonstrate a novel role for JI-34 to markedly improve therapeutic angiogenesis in hindlimb ischemia by increasing the viability and mobility of MSCs. These findings support additional studies to explore the full potential of growth hormone-releasing hormone agonists to augment cell therapy in the management of ischemia.

Transplantation of SIRT1-engineered aged mesenchymal stem cells improves cardiac function in a rat myocardial infarction model.

BACKGROUND: Previous studies have demonstrated that biological aging has a negative influence on the therapeutic effects of mesenchymal stem cells (MSCs)-based therapy. Using a rat myocardial infarction (MI) model, we tested the hypothesis that silent mating type information regulation 2 homolog 1 (SIRT1) may ameliorate the phenotype and improve the function of aged MSCs and thus enhance the efficacy of aged MSCs-based therapy. METHODS: Sixty female rats underwent left anterior descending coronary artery ligation and were randomly assigned to receiving: intramyocardial injection of cell culture medium (DMEM group); SIRT1 overexpression vector-treated aged MSCs (SIRT1-aged MSCs group) obtained from aged male SD rats or empty vector-treated aged MSCs (vector-aged MSCs group). Another 20 sham-operated rats that underwent open-chest surgery without coronary ligation or any other intervention served as controls. RESULTS: SIRT1-aged MSC group exhibited enhanced blood vessel density in the border zone of MI hearts, which was associated with reduced cardiac remodeling, leading to improved cardiac performance. Consistent with the in vivo data, our in vitro experiments also demonstrated that SIRT1 overexpression ameliorated aged MSCs senescent phenotype and recapitulated the pro-angiogenesis property of MSCs and conferred the anti-stress response capabilities, as indicated by increases in pro-angiogenic factors, angiopoietin 1 (Ang1) and basic fibroblast growth factor (bFGF), expressions and a decrease in anti-angiogenic factor thrombospondin-1 (TBS1) at mRNA levels, and increases in Bcl-2/Bax ratio at protein level. CONCLUSIONS: Up-regulating SIRT1 expression could enhance the efficacy of aged MSCs-based therapy for MI as it relates to the amelioration of senescent phenotype and hence improved biological function of aged MSCs.

SIRT1 ameliorates age-related senescence of mesenchymal stem cells via modulating telomere shelterin.

Mesenchymal stem cells (MSCs) senescence is an age-related process that impairs the capacity for tissue repair and compromises the clinical use of autologous MSCs for tissue regeneration. Here, we describe the effects of SIRT1, a NAD(+)-dependent deacetylase, on age-related MSCs senescence. Knockdown of SIRT1 in young MSCs induced cellular senescence and inhibited cell proliferation whereas overexpression of SIRT1 in aged MSCs reversed the senescence phenotype and stimulated cell proliferation. These results suggest that SIRT1 plays a key role in modulating age-induced MSCs senescence. Aging-related proteins, P16 and P21 may be downstream effectors of the SIRT1-mediated anti-aging effects. SIRT1 protected MSCs from age-related DNA damage, induced telomerase reverse transcriptase (TERT) expression and enhanced telomerase activity but did not affect telomere length. SIRT1 positively regulated the expression of tripeptidyl peptidase 1 (TPP1), a component of the shelterin pathway that protects chromosome ends from DNA damage. Together, the results demonstrate that SIRT1 quenches age-related MSCs senescence by mechanisms that include enhanced TPP1 expression, increased telomerase activity and reduced DNA damage.

Impaired CXCR4 expression and cell engraftment of bone marrow-derived cells from aged atherogenic mice.

OBJECTIVES: Reduced numbers and activity of circulating progenitor cells are associated with aging and have been linked with coronary artery disease. To determine the impact of aging and atherosclerotic disease on the chemotaxic activity of bone marrow derived cells (BMCs), we examined CXCR4 surface expression on BMCs from aged and atherosclerotic mice. METHODS: CXCR4 expression and cellular mobility were compared between BMCs of young (6-week old) ApoE null mice (ApoE(-/-)) and aged ApoE(-/-) mice that had been fed with a high-fat, high-cholesterol diet for 6-months. RESULTS: Age and atherosclerosis correlated with significantly lower surface expression of CXCR4 that was less inducible by calcium. The impaired calcium response was associated with defective calcium influx and was partially recovered by treatment with the calcium ionophore ionomycin. ApoE(-/-) mice fed high fat diet for 6-months had defective CXCR4 expression and SDF-1 regulation that is equivalent to that of 24-month old wild type mice. BMCs from aged, atherogenic ApoE(-/-) mice also displayed defective homing to SDF-1, and the animals had lower serum and bone marrow levels of SDF-1. CONCLUSION: Evolution of atherosclerosis in ApoE(-/-) mice is paralleled by progressive loss of mobility of BMCs with reductions of CXCR4 expression, and reduced levels of SDF-1 in both serum and bone marrow. These changes mute the homing capability of BMCs and may contribute to the progression of atherosclerosis in this model.

Protein expression of mesenchymal stem cells after transfection of pcDNA3.1⁻-hVEGF165 by ultrasound-targeted microbubble destruction.

Ultrasound-targeted microbubble destruction (UTMD) has been proposed as a new technique for organ-specific gene transfer and drug delivery. This study was performed to investigate the effect of UTMD on marrow mesenchymal stem cells (MSCs) transfected with pcDNA3.1⁻-hVEGF165.pcDNA3.1⁻-hVEGF165 were transfected into the third passage of MSCs, with or without UTMD under different ultrasound conditions. Protein expression was quantified by hVEGF165-ELISA kit after transfection for 24, 48, and 72 hours. UTMD-mediated transfection of MSCs yielded a significant protein expression. UTMD of mechanic index (MI) 0.6 for 90 seconds led to the highest level of protein expression.

Defective CXCR4 expression in aged bone marrow cells impairs vascular regeneration.

The chemokine stromal cell-derived factor-1 (SDF-1) plays a critical role in mobilizing precursor cells in the bone marrow and is essential for efficient vascular regeneration and repair. We recently reported that calcium augments the expression of chemokine receptor CXCR4 and enhances the angiogenic potential of bone marrow derived cells (BMCs). Neovascularization is impaired by aging therefore we suggested that aging may cause defects of CXCR4 expression and cellular responses to calcium. Indeed we found that both the basal and calcium-induced surface expression of CXCR4 on BMCs was significantly reduced in 25-month-old mice compared with 2-month-old mice. Reduced Ca-induced CXCR4 expression in BMC from aged mice was associated with defective calcium influx. Diminished CXCR4 surface expression in BMC from aged mice correlated with diminished neovascularization in an ischemic hindlimb model with less accumulation of CD34(+) progenitor cells in the ischemic muscle with or without local overexpression of SDF-1. Intravenous injection of BMCs from old mice homed less efficiently to ischemic muscle and stimulated significantly less neovascularization compared with the BMCs from young mice. Transplantation of old BMCs into young mice did not reconstitute CXCR4 functions suggesting that the defects were not reversible by changing the environment. We conclude that defects of basal and calcium-regulated functions of the CXCR4/SDF-1 axis in BMCs contribute significantly to the age-related loss of vasculogenic responses.

Heat shock protein 90 protects rat mesenchymal stem cells against hypoxia and serum deprivation-induced apoptosis via the PI3K/Akt and ERK1/2 pathways.

Mesenchymal stem cell (MSC) transplantation has shown a therapeutic potential to repair the ischemic and infracted myocardium, but the effects are limited by the apoptosis and loss of donor cells in host cardiac microenvironment. The aim of this study is to explore the cytoprotection of heat shock protein 90 (Hsp90) against hypoxia and serum deprivation-induced apoptosis and the possible mechanisms in rat MSCs. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was assessed by Hoechst 33258 nuclear staining and flow cytometric analysis with annexin V/PI staining. The gene expression of Toll-like receptor-4 (TLR-4) and V-erb-b2 erythroblastic leukemia viral oncogene homolog 2 (ErbB2) was detected by real-time polymerase chain reaction (PCR). The protein levels of cleaved caspase-3, Bcl-2, Bcl-xL, Bax, total-ERK, phospho-ERK, total-Akt, phospho-Akt, and Hsp90 were detected by Western blot. The production of nitric oxide was measured by spectrophotometric assay. Hsp90 improves MSC viability and protects MSCs against apoptosis induced by serum deprivation and hypoxia. The protective role of Hsp90 not only elevates Bcl-2/Bax and Bcl-xL/Bax expression and attenuates cleaved caspase-3 expression via down-regulating membrane TLR-4 and ErbB2 receptors and then activating their downstream PI3K/Akt and ERK1/2 pathways, but also enhances the paracrine effect of MSCs. These findings demonstrated a novel and effective treatment strategy against MSC apoptosis in cell transplantation.