Evaluating the impact of metformin targets on the risk of osteoarthritis: a mendelian randomization study

Mitochondrial quality control dysfunction in osteoarthritis: Mechanisms, therapeutic strategies & future prospects

Osteoarthritis (OA) is a prevalent chronic joint disease characterized by articular cartilage degeneration, pain, and disability. Emerging evidence indicates that mitochondrial quality control dysfunction contributes to OA pathogenesis. Mitochondria are essential organelles to generate cellular energy via oxidative phosphorylation and regulate vital processes. Impaired mitochondria can negatively impact cellular metabolism and result in the generation of harmful reactive oxygen species (ROS). Dysfunction in mitochondrial quality control mechanisms has been increasingly linked to OA onset and progression. This review summarizes current knowledge on the role of mitochondrial quality control disruption in OA, highlighting disturbed mitochondrial dynamics, impaired mitochondrial biogenesis, antioxidant defenses and mitophagy. The review also discusses potential therapeutic strategies targeting mitochondrial Quality Control in OA, offering future perspectives on advancing OA therapeutic strategies.

Genetic evidence strengthens the connection between gut microbiota and gingivitis: a two-sample Mendelian randomization study

Introduction

The oral cavity and gut tract, being interconnected and rich in microbiota, may have a shared influence on gingivitis. However, the specific role of distinct gut microbiota taxa in gingivitis remains unexplored. Utilizing Mendelian Randomization (MR) as an ideal method for causal inference avoiding reverse causality and potential confounding factors, we conducted a comprehensive two-sample MR study to uncover the potential genetic causal impact of gut microbiota on gingivitis.

Methods

Instrumental variables were chosen from single nucleotide polymorphisms (SNPs) strongly associated with 418 gut microbiota taxa, involving 14,306 individuals. Gingivitis, with 4,120 cases and 195,395 controls, served as the outcome. Causal effects were assessed using random-effect inverse variance-weighted, weighted median, and MR-Egger methods. For replication and meta-analysis, gingivitis data from IEU OpenGWAS were employed. Sensitivity analyses included Cochran's Q tests, funnel plots, leave-one-out analyses, and MR-Egger intercept tests. This study aimed to assess the genetic correlation between the genetically predicted gut microbiota and gingivitis using linkage disequilibrium score regression (LDSC).

Results

Three gut microbiota taxa (class Actinobacteria id.419, family Defluviitaleaceae id.1924, genus Defluviitaleaceae UCG011 id.11287) are predicted to causally contribute to an increased risk of gingivitis (P< 0.05). Additionally, four gut microbiota taxa (class Actinobacteria id.419, genus Escherichia Shigella id.3504, genus Ruminococcaceae UCG002 id.11360) potentially exhibit inhibitory causal effects on the risk of gingivitis (P< 0.05). No significant evidence of heterogeneity or pleiotropy is detected. Our findings indicate a suggestive genetic correlation between class Actinobacteria id.419, class Bacteroidia id.912, family Defluviitaleaceae id.1924, genus Escherichia Shigella id.3504 and gingivitis.

Conclusion

Our study establishes the genetic causal effect of 418 gut microbiota taxa on gingivitis, offering insights for clinical interventions targeting gingivitis. Subsequent research endeavors are essential to corroborate the findings of our present study.

Relationships between obesity and functional outcome after ischemic stroke: a Mendelian randomization study

BACKGROUND AND OBJECTIVES

Most previous studies suggested obesity deteriorates the functional outcome after ischemic stroke. But there are researches claiming that obesity is associated with lower mortality, recurrence, and readmission rates, which is known as the obesity paradox. Our current research aimed to investigate the correlation between genetically obesity and the post-stroke outcome with the Mendelian randomization (MR) method.

METHODS

The UK Biobank and the GIANT consortium provided instrumental variables for body mass index (BMI, 806,834 individuals) and waist-to-hip ratio (WHR, 697,734 individuals). Data of functional outcome after ischemic stroke were obtained from the Genetics of Ischemic Stroke Functional Outcome network (6012 individuals). Inverse-variance weighted approach was utilized as the primary analyses. Sensitivity analyses involved the utilization of different MR methods. The heterogeneity among genetic variants was assessed by I2 and Q value statistics.

RESULTS

In univariable analysis, there was a significant connection between genetic susceptibility to WHR and worse functional outcome (modified Rankin Scale 3) after ischemic stroke (OR [95%CI] = 1.47 [1.07, 2.02], P = 0.016). Genetic liability to BMI and was not associated with post-stroke functional outcome (all P > 0.05). The overall patterns between genetic liability to WHR and functional outcome post-ischemic outcome no longer existed in the multivariable MR analysis after adjusting for BMI (OR [95%CI] = 1.26[0.76,1.67], P = 0.56).

CONCLUSION

The current MR study provided evidence that WHR was correlated to unfavorable outcome post-ischemic stroke. Exploring interventions against obesity may potentially improve recovery after ischemic stroke.

Connecting atrial fibrillation to digestive neoplasms: exploring mediation via ischemic stroke and heart failure in Mendelian randomization studies

Background

Notwithstanding the acknowledged interplay between atrial fibrillation (AF) and the emergence of digestive system neoplasms, the intricacies of this relationship remain ambiguous. By capitalizing univariable Mendelian Randomization (MR) complemented by a mediated MR tactic, our pursuit was to elucidate the causative roles of AF in precipitating digestive system malignancies and potential intermediary pathways.

Method

This research endeavor seeks to scrutinize the causal clinical implications of whether genetic predispositions to AF correlate with an increased risk of digestive system malignancies, employing MR analytical techniques. Utilizing a dataset amalgamated from six studies related to AF, encompassing over 1,000,000 subjects, we performed univariable MR assessments, employing the random-effects inverse-variance weighted (IVW) methodology as our principal analytical paradigm. Subsequently, a mediated MR framework was employed to probe the potential mediating influence of AF on the nexus between hypertension (HT), heart failure (HF), ischemic stroke (IS), coronary artery disease (CAD), and digestive system neoplasms.

Result

The univariable MR evaluation unveiled a notable causal nexus between the genetic inclination toward AF and the genetic susceptibility to colon, esophageal, and small intestine malignancies. The mediated MR scrutiny ascertained that the genetic inclination for AF amplifies the risk profile for colon cancer via IS pathways and partially explains the susceptibility to esophageal and small intestine tumors through the HF pathway.

Conclusion

Our investigative endeavor has highlighted a definitive causative association between genetic inclination to AF and specific digestive system neoplasms, spotlighting IS and HF as instrumental mediators. Such revelations furnish pivotal perspectives on the complex genetic interconnections between cardiovascular anomalies and certain digestive tract tumors, emphasizing prospective therapeutic and diagnostic worthy of pursuit.

Osteoarthriris year in review 2023: genetics, genomics, and epigenetics

OBJECTIVE

To elucidate the scientific advances made in the last 12 months within the realm of osteoarthritis genetics, genomics, and epigenetics. This review paper highlights major research publications that enhance our current understanding of the role of genetics, genomics, and epigenetics in osteoarthritis.

METHODS

A systematic literature search was conducted on pubmed.ncbi.nlm.nih.gov on "March 17, 2023", using the following keywords: "osteoarthritis" in combination with any of these terms: "genetic(s)", "mutation(s)", "genomic(s)", "epigenetic(s)", "DNA methylation", "noncoding RNA", "lncRNA", "circular RNA", "microRNA", "transcriptomic(s)", "RNA sequencing", "single cell RNA sequencing", or "single nucleus RNA sequencing". The selection comprised original research articles published in the English language between the OARSI congresses of 2022 and 2023.

RESULTS

A total of 2178 research articles were identified, which subsequently reduced to 67 unique articles relevant to the field. Current trends in osteoarthritis genetics research involve meta-analyses of various cohorts to explore the impact of gene variants on osteoarthritis-related outcomes, such as pain. Early developmental changes within the joint were also found to influence osteoarthritis through genetic variations. Researchers also prioritize testing the mechanisms and functions of miRNAs, circRNAs, and lncRNAs. Potential drug targets began to emerge; however, independent validation studies are lacking. Single cell RNA sequencing studies revealed unique immune cell populations in the knee; however, no study reported single nucleus RNA sequencing analysis.

CONCLUSIONS

This review focused on recent advances in the above-mentioned themes within the field of osteoarthritis. These advances improve our understanding of the disease's complexity and guide us toward functional assessments of genetic/epigenetic outcomes and toward their translational and clinical applications.

Genetic effect of metformin use on risk of cancers: evidence from Mendelian randomization analysis

BACKGROUND

Increasing number of studies reported the positive effect of metformin on the prevention and treatment of cancers. However, the genetic causal effect of metformin utilization on the risk of common cancers was not completely demonstrated.

METHODS

Two-sample Mendelian Randomization (two-sample MR) analysis was conducted to uncover the genetically predicted causal association between metformin use and 26 kinds of cancers. Besides, two-step Mendelian Randomization (two-step MR) assessment was applied to clarify the mediators which mediated the causal effect of metformin on certain cancer. We utilized five robust analytical methods, in which the inverse variance weighting (IVW) method served as the major one. Sensitivity, pleiotropy, and heterogeneity were assessed. The genetic statistics of exposure, outcomes, and mediators were downloaded from publicly available datasets, including the Open Genome-Wide Association Study (GWAS), FinnGen consortium (FinnGen), and UK Biobank (UKB).

RESULTS

Among 26 kinds of common cancers, HER-positive breast cancer was presented with a significant causal relationship with metformin use [Beta: - 4.0982; OR: 0.0166 (95% CI: 0.0008, 0.3376); P value: 0.0077], which indicated metformin could prevent people from HER-positive breast cancer. Other cancers only showed modest associations with metformin use. Potential mediators were included in two-step MR, among which total testosterone levels (mediating effect: 24.52%) displayed significant mediating roles. Leave-one-out, MR-Egger, and MR-PRESSO analyses produced consistent outcomes.

CONCLUSION

Metformin use exhibited a genetically protective effect on HER-positive breast cancer, which was partially mediated by total testosterone levels.

Exerkines and osteoarthritis

Osteoarthritis (OA) is the most prevalent chronic joint disease, with physical exercise being a widely endorsed strategy in its management guidelines. Exerkines, defined as cytokines secreted in response to acute and chronic exercise, function through endocrine, paracrine, and/or autocrine pathways. Various tissue-specific exerkines, encompassing exercise-induced myokines (muscle), cardiokines (heart), and adipokines (adipose tissue), have been linked to exercise therapy in OA. Exerkines are derived from these kines, but unlike them, only kines regulated by exercise can be called exerkines. Some of these exerkines serve a therapeutic role in OA, such as irisin, metrnl, lactate, secreted frizzled-related protein (SFRP), neuregulin, and adiponectin. While others may exacerbate the condition, such as IL-6, IL-7, IL-15, IL-33, myostatin, fractalkine, follistatin-like 1 (FSTL1), visfatin, activin A, migration inhibitory factor (MIF), apelin and growth differentiation factor (GDF)-15. They exerts anti-/pro-apoptosis/pyroptosis/inflammation, chondrogenic differentiation and cell senescence effect in chondrocyte, synoviocyte and mesenchymal stem cell. The modulation of adipokine effects on diverse cell types within the intra-articular joint emerges as a promising avenue for future OA interventions. This paper reviews recent findings that underscore the significant role of tissue-specific exerkines in OA, delving into the underlying cellular and molecular mechanisms involved.

Association between the use of lipid-lowering drugs and the risk of inflammatory bowel disease

BACKGROUND

Observational studies have suggested an association between lipid-lowering drugs and inflammatory bowel disease (IBD) risk. This study aimed to assess the causal influence of lipid-lowering agents on IBD risk using Mendelian randomization analysis.

METHOD

In a population of 173,082 individuals of European ancestry, 55 single-nucleotide polymorphisms were identified as instrumental variables for 6 lipid-lowering drug targets (HMGCR, NPC1LC, PCSK9, LDLR, CETP and APOB). Summary statistics for the genome-wide association study of IBD, ulcerative colitis (UC) and Crohn's disease (CD) were obtained from the FinnGen consortium, Program in Complex Trait Genomics and UK Biobank. Inverse-variance weighted was employed as the primary MR method, and odds ratios (ORs) with 95% confidence intervals were reported as the results. Sensitivity analyses using conventional MR methods were conducted to assess result robustness.

RESULTS

Gene-proxied inhibition of Niemann-Pick C1-like 1 (NPC1L1) was associated with an increased IBD risk (OR [95% CI]: 2.31 [1.38, 3.85]; p = .001), particularly in UC (OR [95% CI]: 2.40 [1.21, 4.74], p = .012), but not in CD. This finding was replicated in the validation cohort. Additionally, gene-proxied inhibition of low-density lipoprotein receptor was associated with reduced IBD (OR [95% CI]: .72 [.60, .87], p < .001) and UC risk (OR [95% CI]: .74 [.59, .92], p = .006), although this result was not replicated in the validation cohort. Other drug targets did not show significant associations with IBD, UC or CD risk.

CONCLUSION

Inhibition of the lipid-lowering drug-target NPC1L1 leads to an increased IBD risk, mainly in the UC population.

Effects of putative metformin targets on phenotypic age and leukocyte telomere length: a mendelian randomisation study using data from the UK Biobank

BACKGROUND

Metformin, a first-line medication for type 2 diabetes, might also have a protective effect against ageing-related diseases, but so far little experimental evidence is available. We sought to assess the target-specific effect of metformin on biomarkers of ageing in the UK Biobank.

METHODS

In this drug target mendelian randomisation study, we assessed the target-specific effect of four putative targets of metformin (AMPK, ETFDH, GPD1, and PEN2), involving ten genes. Genetic variants with evidence of causation of gene expression, glycated haemoglobin A1c (HbA1c), and colocalisation were used as instruments mimicking the target-specific effect of metformin via HbA1c lowering. The biomarkers of ageing considered were phenotypic age (PhenoAge) and leukocyte telomere length. To triangulate the evidence, we also assessed the effect of HbA1c on the outcomes using a polygenic mendelian randomisation design and assessed the effect of metformin use on these outcomes using a cross-sectional observational design.

FINDINGS

GPD1-induced HbA1c lowering was associated with younger PhenoAge (β -5·26, 95% CI -6·69 to -3·83) and longer leukocyte telomere length (β 0·28, 0·03 to 0·53), and AMPKγ2 (PRKAG2)-induced HbA1c lowering was associated with younger PhenoAge (β -4·88, -7·14 to -2·62) but not with longer leukocyte telomere length. Genetically predicted HbA1c lowering was associated with younger PhenoAge (β -0·96 per SD lowering of HbA1c, 95% CI -1·19 to -0·74) but not associated with leukocyte telomere length. In the propensity score matched analysis, metformin use was associated with younger PhenoAge (β -0·36, 95% CI -0·59 to -0·13) but not with leukocyte telomere length.

INTERPRETATION

This study provides genetic validation evidence that metformin might promote healthy ageing via targets GPD1 and AMPKγ2 (PRKAG2), and the effect could be in part due to its glycaemic property. Our findings support further clinical research into metformin and longevity.

FUNDING

Healthy Longevity Catalyst Award, National Academy of Medicine, and Seed Fund for Basic Research, The University of Hong Kong.

DNA Supramolecular Hydrogel-Enabled Sustained Delivery of Metformin for Relieving Osteoarthritis

Osteoarthritis (OA) is a musculoskeletal disorder affecting ∼500 million people worldwide. Metformin (MET), as an oral hypoglycemic drug approved by the Food and Drug Administration, has displayed promising potential for treating OA. Nonetheless, in the articular cavity, MET suffers from rapid clearance and cannot circumvent the severe inflammatory environment, greatly confining the therapeutic efficacy. Herein, DNA supramolecular hydrogel (DSH) has been utilized as a sustained drug delivery vehicle for MET to treat OA, which dramatically prolonged the retention time of MET in the articular cavity from 3 to 14 days and simultaneously exerted a greater anti-inflammatory effect. Our delivery platform, termed MET@DSH, better protects cartilage than single-agent MET. Additionally, the corresponding molecular mechanisms underlying the therapeutic effects were also analyzed. We anticipate this DNA supramolecular hydrogel-enabled sustained drug delivery and anti-inflammatory strategy will reshape the current landscape of OA treatment.

Metformin Treatment Reduces the Incidence of Rheumatoid Arthritis: A Two-Sample Mendelian Randomized Study

Several studies have shown that rheumatologic patients can benefit from metformin, but it remains unclear whether metformin treatment is causally associated with the risk of rheumatoid arthritis (RA). A two-sample Mendelian randomization (MR) study was conducted to investigate the causal relationship between metformin treatment and the incidence of rheumatoid arthritis. The genome-wide significant (p < 5 × 10^-8) single-nucleotide polymorphisms (SNPs) associated with metformin use were selected as instrumental variables (IVs). Summary statistics on RA were extracted from a large genome-wide association study (GWAS) meta-analysis. The inverse variance-weighted (IVW) method was used as the determinant of the causal effects of metformin treatment on RA. Cochran's Q was used to detect heterogeneity. Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) test and MR-Egger regression were used to detect horizontal pleiotropy. A total of 34 SNPs significantly associated with metformin treatment were obtained. Thirty-two SNPs were selected as IVs after removing two SNPs for being palindromic with intermediate allele frequencies (rs11658063 and rs4930011). The IVW results showed a negative causal association between metformin treatment and RA (OR = 0.0232, 95% CI 1.6046 × 10^-3 - 0.3368; p = 0.006). Meanwhile, no heterogeneity or pleiotropy was detected, indicating that the results were reliable. This study indicated a negative causality between metformin treatment and RA, indicating that the treatment of metformin can prevent the pathogenesis of RA.