Lipoprotein(a), abbreviated Lp(a), is structurally an LDL particle with a twist. It contains apolipoprotein B100 covalently linked, in a one-to-one molar ratio, to apolipoprotein(a), a glycoprotein whose gene sits on chromosome 6 and shares more than 80 percent structural homology with plasminogen, the key enzyme precursor of blood clot dissolution. Apolipoprotein(a) is built from repeated kringle domains, and one of them, kringle 4 type 2, is present in a variable number of copies, usually between 3 and more than 40. This copy number varies enormously between individuals and ancestry groups and is the major determinant of both the size of the particle and the concentration of Lp(a) in plasma: smaller isoforms are secreted more efficiently by hepatocytes, so people carrying fewer repeats tend to have higher circulating levels. The entire production process occurs in the liver, where apo(a) and apoB are secreted separately and assembled into mature Lp(a) particles outside the cell.

The scientific history of Lp(a) is a story of enthusiasm, disappointment, and redemption. After observational studies in the late 1980s linked plasma levels to coronary heart disease, early prospective trials produced discordant results, and because no diet or drug could reliably lower the particle, interest waned for roughly two decades. That picture changed dramatically with population-based studies, meta-analyses, genome-wide association studies, and Mendelian randomization analyses, which together established Lp(a) as a strong, independent, and genetically determined causal risk factor for atherosclerotic cardiovascular disease. Plasma Lp(a) measurement now reclassifies the risk category of approximately 40 percent of primary prevention patients who sit in the intermediate band of the Framingham risk score, and recent guidelines recommend widespread testing. Values above 50 mg/dL, or 125 nmol/L, are conventionally considered elevated; roughly 15 to 20 percent of people worldwide exceed this threshold, and the population distribution is strongly skewed, ranging from less than 0.2 to more than 200 mg/dL.

The concept of residual cardiovascular risk is central to the review’s argument. Even when blood pressure, LDL cholesterol, blood glucose, obesity, and smoking are treated to the best standards of care, a substantial probability of major adverse cardiovascular events remains. The evidence is striking. In the PRIME study, which followed 9,649 men aged 50 to 59 for ten years, treated hypertensive patients had a 50 percent higher relative risk of major cardiovascular events after adjustment for concurrent risk factors. In the Framingham Offspring Cohort, treated hypertensive patients whose blood pressure was below 140/90 mm Hg still carried a 50 percent higher risk of cardiovascular events than untreated subjects with comparable readings. On the lipid side, long-term reassessments of early statin trials show a residual risk of approximately 30 percent, and even trials of the most potent PCSK9 inhibitors, which drove LDL cholesterol to a median below 30 mg/dL, could not normalize cardiovascular risk. A recent participant-level meta-analysis demonstrated that effective LDL reduction does not offset Lp(a)-related risk: participants with Lp(a) above 50 mg/dL and LDL below 77 mg/dL still had a 38 percent greater risk than patients with lower Lp(a) levels.

What makes Lp(a) especially relevant to kidney disease is that the kidney itself appears to be a major site of Lp(a) clearance. Clinical studies consistently show that plasma Lp(a) rises progressively as glomerular filtration rate falls, and the review’s authors contributed their own evidence: in 417 patients with arterial hypertension, 160 of whom had hypertensive nephroangiosclerosis with creatinine clearance between 30 and 89 mL/min/1.73 m², Lp(a) levels were significantly higher in those with renal involvement, correlated inversely with creatinine clearance, and were associated with more prevalent coronary, cerebrovascular, and peripheral artery disease. Notably, urinary albumin losses did not correlate with Lp(a) levels and apo(a) phenotype distribution was comparable across levels of kidney function, suggesting that kidney damage itself, rather than altered isoform expression, drives the increase. Stable isotope turnover studies and urinary apo(a) clearance studies support the conclusion that elevated Lp(a) in chronic kidney disease reflects reduced renal clearance rather than increased hepatic production.

Prospective cohort data now confirm that this biochemical elevation translates into clinical harm. In the Chronic Renal Insufficiency Cohort study, 3,744 participants followed for 7.5 years showed that those in the highest quartile of Lp(a), above 61.3 mg/dL, had a 49 percent higher risk of myocardial infarction and a 28 percent higher risk of death. The German Chronic Kidney Disease study, which followed 5,043 subjects for 6.5 years, found that each 10 mg/dL increase in Lp(a) raised cardiovascular disease risk by 6.5 percent, with risk climbing more than 30 percent in subjects above 70 mg/dL regardless of traditional risk factors. A systematic review of 15 studies encompassing 12,260 participants with kidney disease confirmed that high Lp(a) independently predicts cardiovascular events and death, and data from the China Renal Data System, covering more than 50,000 participants, linked rising Lp(a) to both progression of renal failure and cardiovascular mortality. The particle is also entwined with calcific aortic valve disease, which frequently accompanies advanced kidney disease, although MESA study data on 6,346 subjects found the association between valve calcification and kidney dysfunction occurred independently of Lp(a) levels.

The dialysis and transplantation literature provides a natural experiment that strengthens the causal interpretation. Patients on hemodialysis have higher Lp(a) than healthy subjects and patients with early kidney disease, and peritoneal dialysis patients show elevations independent of apo(a) isoform size. Crucially, neither hemodialysis nor peritoneal dialysis lowers Lp(a), whereas renal transplantation significantly reduces it, a rapid change consistent with the restoration of renal clearance. In nephrotic syndrome, where heavy urinary protein wasting raises Lp(a) independently of filtration rate, levels normalize after remission of the causative condition, likely reflecting increased hepatic synthesis rather than impaired catabolism. Together these observations justify repeated Lp(a) measurements during the course of progressive kidney disease, since levels fluctuate with inflammatory states and changes in treatment even though they are largely stable over time in the general population.

The therapeutic landscape is changing rapidly. Traditional lipid-lowering drugs have negligible effects on Lp(a), and dietary interventions are unpredictable at best, although replacing saturated fatty acids with unsaturated fats and long-chain carbohydrates produces small reductions. The PCSK9 inhibitors evolocumab and alirocumab lower Lp(a) by only about 27 and 23 percent respectively, from baseline levels that were mostly well below risk thresholds. The new generation of agents is different. Pelacarsen, an antisense oligonucleotide delivered to hepatocytes via the asialoglycoprotein receptor, degrades LPA mRNA and reduced Lp(a) by 80 percent at a dose of 20 mg weekly over six months. Small interfering RNAs conjugated with N-acetyl-galactosamine, including olpasiran, zerlasiran, and lepodisiran, harness the RNA-induced silencing complex to the same end: olpasiran achieved placebo-adjusted reductions of 97 percent, zerlasiran 95 percent with a single 450 mg dose, and lepodisiran 94 percent with 400 mg. Muvalaplin, an oral small molecule that blocks the kringle 4-mediated interaction between apo(a) and apoB, reduced Lp(a) by 86 percent at 240 mg per day over three months. Phase 3 outcome trials such as Lp(a)HORIZON, OCEAN(a), and ACCLAIM-Lp(a) are now testing whether these dramatic biochemical reductions translate into fewer cardiovascular events.

There is, however, a critical caveat for the kidney community: every trial of these investigational drugs excluded patients with advanced chronic kidney disease or on dialysis, so efficacy, dosing, and long-term safety in renal patients remain unknown and cannot be extrapolated. In the meantime, the review’s authors emphasize that rigorous application of proven preventive measures remains essential, including smoking cessation, salt restriction, exercise, blood pressure targets below 130/80 mm Hg with renin-angiotensin system inhibitors, glycated hemoglobin below 7.0 percent, SGLT2 inhibitors, GLP-1 receptor agonists, finerenone, and intensive lipid lowering to LDL below 55 mg/dL using statins, ezetimibe, and PCSK9 inhibitors as needed. For selected high-risk patients with elevated Lp(a), lipoprotein apheresis offers an existing, if cumbersome, option: retrospective series report reductions from a mean of 138 mg/dL to 51 mg/dL with a 94 percent reduction in major cardiovascular events over four years, and in nine hemodialysis patients undergoing combined apheresis, median Lp(a) fell from 242.7 to 64.2 nmol/L with a 57 percent reduction in adverse cardiac and vascular events over four years.

A landmark Mendelian randomization analysis adds a note of scientific caution: genetically predicted lifelong differences in Lp(a) correspond to an estimated 6 percent decrease in atherosclerotic cardiovascular disease odds for every 10 mg/dL reduction, but such estimates cannot be directly translated into the expected effect of short-term pharmacological lowering, and meaningful clinical benefit would likely require reductions greater than 50 mg/dL. Still, with new therapies capable of cutting Lp(a) by up to 90 percent from baseline, the potential is enormous. If ongoing trials demonstrate that profound Lp(a) reduction lowers residual cardiovascular risk, and if dedicated studies in patients with kidney disease follow, Lp(a) could be transformed from a passive risk marker into a primary therapeutic target for one of the most vulnerable populations in cardiovascular medicine.

Subject of Research: The role of lipoprotein(a) in residual cardiovascular risk among patients with chronic kidney disease and emerging Lp(a)-lowering therapies

Article Title: Lipoprotein(a): a potential target for the reduction of residual cardiovascular risk in patients with chronic kidney disease

Article References: Sechi, L. A., Bulfone, L., Vacca, A., Comand, J., Marcante, S., Brosolo, G., Pagano, C., & Catena, C. (2026). Lipoprotein(a): a potential target for the reduction of residual cardiovascular risk in patients with chronic kidney disease. Frontiers in Nephrology, 6, Article 1950030. https://doi.org/10.3389/fneph.2026.1950030

Image Credits: AI Generated

DOI: 10.3389/fneph.2026.1950030

Keywords: lipoprotein(a), chronic kidney disease, residual cardiovascular risk, atherosclerotic cardiovascular disease, antisense oligonucleotides, small interfering RNA, pelacarsen, olpasiran, muvalaplin, lipoprotein apheresis, renal clearance, cardiovascular prevention

TMAO is a small, low-molecular-weight metabolite with an outsized reputation. It begins its life in the gut, where bacteria convert dietary precursors such as choline, phosphatidylcholine, betaine, and L-carnitine, abundant in red meat, eggs, dairy, and saltwater fish, into trimethylamine, or TMA. The liver then oxidizes TMA into TMAO via the enzyme flavin monooxygenase 3. From there, TMAO circulates in the blood and is excreted almost entirely by the kidneys, without undergoing any meaningful biotransformation along the way. Elevated plasma TMAO has been associated in numerous studies with cardiovascular disease, atherosclerosis, chronic kidney disease, and type 2 diabetes itself, and in diabetic patients specifically, higher TMAO has been tied to more cardiovascular events, faster loss of kidney function, and greater all-cause mortality.

The new analysis was prompted by a puzzling observation from a secondary analysis of the EMMY trial, in which patients treated with empagliflozin after a myocardial infarction showed a more pronounced rise in serum TMAO than those on placebo. That result raised an obvious question: does the same thing happen in people with type 2 diabetes, and does it extend to other drugs in the class, such as dapagliflozin? To find out, investigators combined individual patient data and stored samples from two prospective, randomised, placebo-controlled, double-blind crossover trials conducted at the University of Erlangen-Nuremberg, registered as NCT02471963 and NCT02383238. In each trial, patients were randomised after a run-in phase to receive either 25 mg empagliflozin or 10 mg dapagliflozin, or matching placebo, once daily for six weeks, followed by a one-week washout and a switch to the alternate treatment for another six weeks.

Fasting blood samples and 24-hour urine collections were obtained at baseline and at the end of both treatment periods, then stored at minus 80 degrees Celsius until analysis. TMAO concentrations were quantified with a validated liquid chromatography tandem mass spectrometry assay, using a deuterated internal standard and protein precipitation with methanol. After excluding a small number of samples that could not be quantified, the final analytical population comprised 123 patients, 69 from the empagliflozin trial and 54 from the dapagliflozin trial. The cohort had a mean age of 61.2 years, was 59 percent male, had a mean HbA1c of 6.7 percent, and a mean estimated glomerular filtration rate of 93.8 mL/min/1.73 m², with more than 70 percent of participants above 90. Compliance, assessed by tablet counts, averaged 99 percent in both trials.

The results were consistent in direction across the pooled population. Median plasma TMAO was 3.71 μmol/L at baseline and 3.60 μmol/L after placebo, but rose to 4.19 μmol/L after active treatment, a crossover difference of 0.36 μmol/L with a p-value of 0.006. The median intraindividual percentage change was 11.5 percent, significantly different from zero. When the drugs were analysed separately, the effect was clearer for dapagliflozin, where median TMAO climbed from 3.30 to 4.44 μmol/L, a 23.4 percent median increase, than for empagliflozin, which produced a numerically similar but statistically non-significant rise of 8.4 percent. The authors suggest the pattern points toward a possible class effect of SGLT-2 inhibitors, echoing the EMMY findings and extending them to a second drug and a different patient population.

Just as intriguing was what happened in the kidneys. Because TMAO is cleared almost exclusively by renal excretion, the researchers calculated its renal clearance from paired plasma and 24-hour urine measurements. Across all 123 patients, median renal clearance of TMAO fell from 95.8 mL/min on placebo to 83.9 mL/min on active drug, a statistically significant decline. In the dapagliflozin group the drop was significant on its own, falling from 109.2 to 97.8 mL/min, while the empagliflozin subgroup showed a non-significant downward trend. Yet the total amount of TMAO excreted in 24-hour urine barely changed, rising only non-significantly. That combination, lower clearance with unchanged total excretion, is a biochemical clue that the kidneys may not be the whole story.

The most obvious candidate explanation is the well-known initial dip in estimated glomerular filtration rate that occurs when SGLT-2 inhibitor therapy begins, a reversible haemodynamic effect of tubuloglomerular feedback. The study did observe a small but significant eGFR decline overall, and TMAO levels correlated negatively with eGFR at all time points, as expected from prior literature. But the eGFR dip was marginal, particularly in the dapagliflozin group, which showed the larger TMAO changes, and crucially, there was no correlation between individual patients’ eGFR changes and their TMAO changes. A reduced filtration rate alone, the authors conclude, cannot adequately explain the rise in plasma TMAO.

That leaves transporters and production. TMAO is eliminated primarily by glomerular filtration with a substantial contribution from transporter-mediated secretion in the proximal tubule, where the organic cation transporter 2 shuttles TMAO from blood into tubular cells and the multidrug and toxin extrusion protein 1 exports it into the urine. Animal work has shown that SGLT-2 inhibition broadly downregulates renal transport proteins, and drug interactions with OCT2 or MATE1 could theoretically reduce TMAO secretion. But if transporter-mediated excretion were truly impaired, the total urinary excretion of TMAO should have fallen, and it did not. The authors therefore favour a different hypothesis: SGLT-2 inhibitors may increase the production of TMAO, most plausibly through changes in the gut microbiome, even though some prior studies had suggested these drugs shift the microbiome in ways that should lower TMAO-producing bacteria. A subgroup analysis of the 20 participants who took antibiotics during the trials found no significant difference in TMAO changes, and the crossover design, in which each patient served as their own control, makes dietary shifts an unlikely confounder, although diets were not formally documented.

The clinical implications remain deliberately open. TMAO is widely characterised as a risk marker, and possibly a risk factor, for cardiovascular and kidney disease, so a drug-induced rise of roughly 10 to 20 percent would seem, on its face, unwelcome. Yet SGLT-2 inhibitors have delivered unmistakable benefits on cardiovascular outcomes and mortality in enormous outcome trials, in diabetic and non-diabetic patients alike, benefits that clearly operate through mechanisms beyond glucose control. Whether the TMAO increase is a harmless bystander, a counterbalancing signal, or something that modulates the drugs’ net benefit is unknown, and the authors call for studies examining outcomes in relation to baseline and on-treatment TMAO levels, as well as cohorts with much higher starting concentrations.

The study’s limitations temper any strong conclusions. Six weeks per treatment period is short, so long-term trajectories of TMAO, whether the rise plateaus, persists, or reverses, cannot be determined. No second baseline was established after the washout, so carryover effects may have blunted the measured effect in some patients. All participants had preserved kidney function, with eGFR above 60, leaving the question unanswered for the many diabetic patients with renal impairment, who typically have the highest TMAO levels. Compliance was assessed by counting returned tablets, and diet went unrecorded. Still, the pooled crossover data are internally consistent, and the message is clear enough to unsettle a comfortable assumption: a drug class celebrated for protecting the heart and kidneys may simultaneously raise circulating levels of one of the most talked-about microbiome-derived risk markers in cardiovascular medicine, and the reason why remains an open and compelling scientific question.

Subject of Research: Effects of SGLT-2 inhibitors on plasma TMAO concentrations and renal clearance in patients with type 2 diabetes

Article Title: Effects of SGLT‐2 Inhibitors on Plasma Concentrations and Renal Clearance of the Risk Marker Trimethylamine‐N‐Oxide in Patients With Type‐2 Diabetes

Article References: Effects of SGLT‐2 Inhibitors on Plasma Concentrations and Renal Clearance of the Risk Marker Trimethylamine‐N‐Oxide in Patients With Type‐2 Diabetes. (n.d.). https://doi.org/10.1002/edm2.70318

Image Credits: AI Generated

DOI: 10.1002/edm2.70318

Keywords: SGLT-2 inhibitors, TMAO, type 2 diabetes, empagliflozin, dapagliflozin, gut microbiome, renal clearance, cardiovascular risk, kidney function, eGFR, clinical trial, biomarkers

The core problem the researchers set out to solve is a tension at the heart of contrast agent chemistry. In T1-weighted MRI, contrast agents work by shortening the longitudinal relaxation time of nearby water protons, causing tissue to appear brighter on the image. The efficiency of that process is captured by a number called the longitudinal relaxivity, or r1, measured in units of inverse millimolar seconds. A higher r1 means each unit of gadolinium brightens tissue more strongly, allowing lower doses. But gadolinium-based particles can also shorten the transverse relaxation time, quantified as r2, which darkens tissue and muddies T1-weighted images when the ratio of r2 to r1 climbs too high. The ideal T1 agent would have a high r1 paired with an r2/r1 ratio as close to one as possible, meaning the particle boosts brightness without any unwanted darkening effect.

To reach that ideal, the team, led by Hui Liao and Jie Fang of Zhejiang Ocean University together with collaborators at Guangzhou First People’s Hospital, the Zhoushan Center for Disease Control and Prevention, and Suzhou Ultra-Nano Technology, turned to surface ligand engineering. Rather than redesigning the nanoparticle core itself, they focused on the shell of molecules that coats it and controls how water molecules interact with the gadolinium ions at the particle surface. Using a two-step ligand exchange strategy, the researchers synthesized ultrasmall gadolinium oxide nanoparticles and progressively swapped their surface chemistry for citrate groups. The approach reflects a growing recognition in the field that the coating on a nanoparticle is not a passive stabilizer but an active determinant of magnetic performance, governing how quickly water protons can approach, bind, and relax near the particle surface.

The results are striking on paper. At a clinically relevant magnetic field strength of 3.0 tesla, the citrate-coated gadolinium oxide nanoparticles, abbreviated Gd2O3-Cit, exhibited a longitudinal relaxivity of 8.714 per millimolar per second, approximately 2.3 times higher than Magnevist, one of the most widely used gadolinium chelates in hospitals worldwide. Just as important, the transverse-to-longitudinal ratio came in at just 1.06, nearly at the theoretical optimum of unity and among the lowest values reported to date for any gadolinium oxide based T1 contrast agent. In practical terms, that means the particles act almost purely as brightening agents, sharpening anatomical detail on T1-weighted scans without the signal loss and contrast confusion that plague many nanoparticle formulations whose r2 contributions contaminate the image.

The physics behind this performance is worth unpacking. Gadolinium ions owe their contrast power to seven unpaired electrons, which create strong local magnetic field fluctuations that accelerate the relaxation of nearby water protons. In conventional chelates, a single gadolinium ion is wrapped in an organic cage, and only a limited number of water molecules can get close enough to feel that influence. In a nanoparticle, hundreds or thousands of gadolinium ions sit at or near the surface, multiplying the number of water molecules that can be relaxed simultaneously. But that advantage comes with a catch: the same dense magnetic material can also generate strong static field inhomogeneities that dephase proton spins and drive T2 shortening, darkening the image. The ultrasmall size of the citrate-coated particles, combined with the way citrate ligands organize water access to the surface, appears to suppress that dephasing pathway almost entirely, preserving the pure T1 character of the signal.

Size matters for another reason that goes beyond magnetism: clearance. Particles small enough, typically below roughly five to eight nanometers in hydrodynamic diameter, can pass through the glomerular filtration barrier of the kidney and be excreted in urine, rather than being captured by the liver and spleen’s scavenging cells, where larger nanoparticles can accumulate for weeks or months. The researchers demonstrated that their Gd2O3-Cit particles have a plasma elimination half-life of 113.8 minutes, long enough to circulate and produce strong vascular enhancement in the liver on in vivo T1-weighted MRI, yet short enough to suggest efficient renal excretion afterward. That balance between circulation time and clearance is notoriously difficult to strike, and it is one of the key hurdles that has kept many promising nanoparticle contrast agents stuck at the preclinical stage.

Safety, of course, is the elephant in the room for anything containing gadolinium. Free gadolinium ions are toxic, interfering with calcium channels and a range of enzymes, which is why all clinical agents wrap the metal in chelating molecules. Concerns deepened after studies linked repeated gadolinium exposure to deposits in brain tissue, particularly with the older linear chelates, prompting regulatory warnings and a shift toward macrocyclic agents. The nanoparticle approach takes a different tack: instead of chelating individual ions, it locks gadolinium into a robust oxide lattice, from which release is expected to be far slower. The team reports preliminary biocompatibility data including cytotoxicity assays, hemolysis testing, and short-term histological examination, all of which indicated acceptable safety profiles under the conditions tested. The authors are careful to frame these as preliminary findings, and much longer-term biodistribution and degradation studies would be needed before any clinical translation, but the early signals are encouraging.

The work also fits into a broader renaissance in contrast agent design. Over the past decade, researchers have explored gadolinium oxide nanoparticles coated with polymers such as polyaspartic acid and poly(methyl vinyl ether-alt-maleic acid), albumin-shelled formulations for high-resolution angiography, biofabricated gadolinium oxide encapsulated in exosomes for renal clearance, and even kilogram-scale syntheses aimed at making the materials practical to produce. Others have pursued gadolinium-free alternatives, including ultrasmall iron oxide and carbon-coated ferrite nanoparticles, to sidestep gadolinium toxicity altogether. What distinguishes the new study is its focus on a single, tunable variable, the surface ligand, and its demonstration that a simple citrate coating, chosen for its biocompatibility and strong binding to gadolinium oxide surfaces, can push relaxivity and r2/r1 performance simultaneously toward the theoretical optimum without exotic chemistry.

The implications, if the approach survives further testing, could be substantial. A contrast agent with more than double the per-gadolinium efficiency of current clinical agents would allow lower injected doses, reducing both cost and any residual safety concerns. Renal clearance would spare patients the long-term organ accumulation associated with larger particles, and the strong vascular enhancement observed in the liver suggests applications in angiography, tumor imaging, and perfusion studies. The researchers also note that a pending Chinese patent application related to the work signals commercial interest in the platform. For now, the study stands as a clean proof of concept that sometimes the most powerful way to improve a nanomaterial is not to rebuild its core but to rethink what sits on its surface, one citrate molecule at a time.

Subject of Research: Development of citrate-coated ultrasmall gadolinium oxide nanoparticles as biocompatible T1-weighted MRI contrast agents with renal clearance

Article Title: Ultra-small biocompatible Gd2O3-Cit nanoparticles for improved T1-weighted MR imaging and renal clearance

Article References: Ultra-small biocompatible Gd2O3-Cit nanoparticles for improved T1-weighted MR imaging and renal clearance. (n.d.). https://doi.org/10.1007/s11051-026-06762-3

Image Credits: AI Generated

DOI: 10.1007/s11051-026-06762-3

Keywords: gadolinium oxide nanoparticles, MRI contrast agent, T1-weighted imaging, citrate coating, surface ligand engineering, relaxivity, renal clearance, biocompatibility, nanomedicine, Magnevist, ligand exchange, diagnostic imaging