The research team, led by investigators at the Chinese PLA General Hospital, began with an unbiased hunt rather than a hypothesis. Using a customized CRISPR-Cas9 library targeting 1,649 metabolic enzymes and regulators—6,596 guide RNAs plus controls—they systematically disabled each gene in A498 clear cell renal cell carcinoma cells and tracked which losses crippled proliferation over 21 days. TPI1 emerged as one of the most robustly depleted hits, sitting at a hub position among the top ten negatively selected genes. The finding was more than a screening artifact: tissue microarrays built from 234 renal tumors and 172 adjacent normal specimens showed markedly elevated TPI1 protein in cancer tissue, a result corroborated by data from the TCGA and an independent cohort. TPI1 expression even climbed with tumor grade, alongside rising frequencies of gain-of-function alterations.

To confirm that TPI1 truly drives tumor growth, the researchers shut it down with short hairpin RNAs in renal cancer cells and watched proliferation collapse in growth curves, EdU incorporation assays, and colony formation tests. In mice bearing xenografts of TPI1-deficient OS-RC-2 cells, tumors were significantly smaller and lighter, with reduced Ki67 staining marking the slowdown in cell division. Crucially, deleting TPI1 caused DHAP to pile up inside cells to roughly ten times normal levels. When the team replaced endogenous TPI1 with a wild-type copy, growth recovered; when they substituted a catalytically dead K14M mutant that cannot handle DHAP, it did not. The lesson was unambiguous: it is TPI1’s enzymatic activity, not some scaffold function, that cancer cells depend on.

Because DHAP cannot cross cell membranes and no eukaryotic transporter for it is known, the team exploited a clever chemical workaround. They fed cells dihydroxyacetone, a membrane-permeable precursor that is converted intracellularly into DHAP by the enzyme TKFC. Supplementing with dihydroxyacetone suppressed cell viability, and silencing TKFC blunted that toxicity—direct evidence that the accumulating upstream metabolite, rather than the loss of the downstream product GAP, was doing the damage. Indeed, adding GAP itself to TPI1-deficient cells offered no rescue at all. The experiment repositioned DHAP in the scientific imagination: no longer a passive glycolytic intermediate, but a molecule with signaling consequences, echoing recent work showing that DHAP can inform the nutrient-sensing complex mTORC1 about glucose availability.

What actually happens inside a cell drowning in DHAP turned out to be the study’s most striking revelation. Transcriptome sequencing of TPI1-deficient cells showed positive enrichment of inflammatory signaling, the p53 pathway, and a senescence-associated secretory phenotype gene set, alongside suppression of E2F targets and G2/M checkpoint programs. The cells stained positive for senescence-associated beta-galactosidase, accumulated the DNA damage marker gamma-H2AX, activated the p53-p21 axis, lost Lamin B1 from their nuclear envelopes, and arrested in the G0/G1 phase. Luminex multiplex analysis and ELISA confirmed a flood of inflammatory secretions—IL-6, IL-8, TNF-alpha, and GM-CSF—the classic SASP signature. In xenografted tumors, the same markers rose in tissue sections. This was not cell death; it was cellular senescence, a durable proliferative arrest that oncologists have long hoped to impose on tumors deliberately.

The engine behind that arrest was mitochondrial. TPI1 knockdown sharply increased overall reactive oxygen species, and probes specific for mitochondrial superoxide and hydrogen peroxide showed the origin clearly: mitochondrial ROS surged. A mitochondria-targeted antioxidant, Mito-TEMPO, brought intracellular ROS back down, reduced the fraction of beta-galactosidase-positive cells, and lowered gamma-H2AX, p53, and p21—mimicking the effects of the general antioxidant NAC. Mitochondrial oxidants were therefore acting as the critical effector, converting a metabolic glitch into DNA double-strand damage and, ultimately, senescence. The remaining question was what had switched the mitochondria into this overdrive state in the first place.

Integrated metabolomic and transcriptomic analysis pointed to calcium. TPI1-deficient cells showed elevated intracellular calcium by both colorimetric assay and fluorescent imaging with Fluo-4 AM. When the researchers compared two chelators, the result was decisive: BAPTA-AM, which binds calcium inside the cell, rescued viability and dampened senescence markers, SASP secretion, and DNA damage, while EGTA, which only chelates extracellular calcium, did essentially nothing. In living tumors, peritumoral BAPTA-AM injections let TPI1-deficient xenografts grow significantly faster than vehicle-treated controls. The signal itself proved to be cyclic ADP-ribose, or cADPR, a second messenger that opens ryanodine receptors on the endoplasmic reticulum and liberates calcium into the cytosol. Metabolomics revealed cADPR accumulating after TPI1 loss, and providing cADPR directly to healthy cells was sufficient on its own to induce calcium overload, beta-galactosidase activity, DNA damage, p53-p21 activation, and SASP release—all of which BAPTA-AM reversed. Conversely, blocking cADPR signaling with the antagonist 8-Br-cADPR suppressed the calcium rise and the senescence program triggered by TPI1 depletion.

Upstream of cADPR, the team identified an unexpected culprit: SARM1, a sterile alpha and TIR motif containing protein long known for its role in axonal degeneration and increasingly appreciated as an NAD-consuming enzyme with catalytic activity rivaling the classical ADP-ribosyl cyclase CD38. In TPI1-deficient cells, CD38 was undetectable, but SARM1 rose markedly—dihydroxyacetone treatment produced the same effect. Overexpressing SARM1 alone reproduced the entire phenotype, from gamma-H2AX and p53-p21 induction to Lamin B1 loss, ROS generation, and SASP secretion, while suppressing proliferation and clonogenic capacity. Removing SARM1 from TPI1-deficient cells restored viability, normalized calcium and cADPR levels, reversed the DNA damage and redox stress, and let xenografts grow faster in mice. Notably, mTORC1 appeared to feed into this circuit: TPI1 loss activated the pathway, read out through phospho-S6K1, and the mTORC1 inhibitor rapamycin attenuated SARM1 induction—yet forced SARM1 expression still drove senescence signaling even under rapamycin, placing SARM1 centrally in the cascade with mTORC1 as a modulator.

The mechanism appears to travel well beyond kidney cancer. Knocking down TPI1 in prostate cancer C4-2, lung cancer A549, and bladder cancer T24 cells likewise curbed viability, raised beta-galactosidase activity, elevated SARM1 and gamma-H2AX, depleted Lamin B1, and increased IL-6, IL-8, and TNF secretion, with TPI1-deficient bladder cancer xenografts growing more slowly in mice. In each line, cADPR and calcium climbed after TPI1 loss, and both BAPTA-AM and 8-Br-cADPR blunted the senescence phenotype, as did SARM1 knockdown—a conserved SARM1-cADPR-calcium axis operating across tumor types.

The implications cut in two directions. For patients with TPI1 deficiency, the rare autosomal recessive disorder caused most often by the E104D mutation, the study offers a mechanistic clue: neither patients nor fly models show overt ATP depletion, and the new work suggests their hemolytic anemia and neurodegeneration may instead stem from a redox-calcium pathway in which DHAP overload drives mitochondrial oxidant stress. For oncology, the findings sketch a metabolite-driven vulnerability: suppressing TPI1, or pharmacologically reinforcing the SARM1-cADPR-calcium-mtROS cascade it controls, might push tumors into senescence deliberately, potentially priming them for immune clearance, while calcium chelation or cADPR antagonism could protect vulnerable tissues. The authors caution that the sensor connecting DHAP to SARM1 remains unidentified, that rapamycin only partially suppressed the phenotype, and that whether the cascade is fully reversible is unknown. Still, the conceptual shift is hard to miss: a century after glycolysis was first mapped in tumors, one of its smallest intermediates has turned out to be a messenger—and cancer cells, it seems, listen closely.

Subject of Research: Metabolite-driven mitochondrial redox signaling linking TPI1 loss to cellular senescence via the SARM1–cADPR–Ca2+ axis in cancer

Article Title: TPI1 Loss Triggers a Metabolite‐Driven Mitochondrial Redox Vulnerability via the SARM1–cADPR–Ca2+ Axis

Article References: Liu, C., Wu, S., Wang, C., Zhou, Z., Cai, T., Tao, W., Zuo, S., Zhang, C., Dong, Y., Feng, Y., Huang, Q., Wang, B., Ma, X., Ma, H., Zhang, X., & Huang, Y. (2026). TPI1 Loss Triggers a Metabolite‐Driven Mitochondrial Redox Vulnerability via the SARM1–cADPR–Ca 2+ Axis. Advanced Science, 13(56), Article e76614. https://doi.org/10.1002/advs.76614

Image Credits: AI Generated

DOI: 10.1002/advs.76614

Keywords: TPI1, DHAP, SARM1, cADPR, calcium signaling, mitochondrial ROS, cellular senescence, clear cell renal cell carcinoma, CRISPR screen, glycolysis, p53-p21 pathway, mTORC1

The research comes at a pivotal moment for cardiovascular medicine. Clinical trials of HDL-raising drugs have repeatedly failed to deliver the promised reduction in heart attacks and strokes, forcing scientists to reconsider whether the quantity of HDL in the blood is the right thing to measure at all. Attention has shifted to HDL quality, the idea that some HDL particles perform their protective functions well while others may be dysfunctional or even harmful. The new study provides some of the most detailed mechanistic evidence to date that a specific, identifiable HDL subtype can be pro-atherogenic, and it argues that targeting HDL quality, rather than simply raising HDL cholesterol numbers, could open a genuinely new therapeutic front against atherosclerotic cardiovascular disease.

To isolate the culprit, the researchers turned to anion-exchange chromatography, a technique that separates lipoproteins according to their surface electrical charge. HDL from human plasma can be resolved into five fractions, designated H1 through H5, with H5 being the most electronegative, meaning it carries an unusually strong negative surface charge that reflects underlying biochemical alterations. The team applied this method to blood samples from 131 asymptomatic individuals, 95 of whom had metabolic syndrome and 36 of whom served as healthy controls. The results were striking: plasma H5 levels were significantly elevated in those with cardiovascular disease risk, averaging 4.0 percent of total HDL compared with 2.7 percent in controls, a difference that reached statistical significance.

The clinical implications became clearer when the researchers examined an imaging cohort of 118 participants who underwent carotid ultrasound assessments. Elevated H5 levels were independently associated with structural markers of subclinical atherosclerosis, including increased intima-media thickness, a measure of the thickening of the inner two layers of the carotid artery wall, and greater plaque burden. These associations held after accounting for conventional risk factors, suggesting that H5 is not merely a passive bystander in metabolic disease but a marker, and quite possibly a mediator, of early arterial damage in people who appear healthy.

What makes H5 so dangerous? The answer lies in its molecular cargo. Proteomic analysis revealed that the triglyceride-rich H5 fraction carries a distinct lipoproteome, markedly enriched with apolipoproteins that are not normally prominent passengers on HDL, including apolipoprotein(a), apolipoprotein B, and apolipoprotein C-III. The presence of apolipoprotein(a) is particularly noteworthy because it is the defining protein component of lipoprotein(a), a genetically determined and causally established risk factor for atherosclerotic cardiovascular disease. Apolipoprotein B is the core structural protein of low-density lipoprotein, the classic bad cholesterol, while apolipoprotein C-III is known to impair the breakdown of triglyceride-rich particles. Their enrichment on an HDL particle suggests that H5 is not simply modified HDL but something closer to a molecular chimera, a particle that has acquired atherogenic cargo and, in doing so, lost its protective identity.

Indeed, the study confirmed that H5 suffers from impaired cholesterol efflux, the fundamental housekeeping function that defines healthy HDL. Rather than extracting cholesterol from peripheral tissues and vessel walls, H5 fails at this task, compounding its harm. But the researchers went further, asking what H5 actually does to the endothelial cells that form the inner lining of arteries. Using human umbilical vein endothelial cells in vitro, they found that exposure to H5 triggered a cascade of damaging events: accumulation of reactive oxygen species, the chemically reactive molecules that oxidize and injure cellular components; activation of the DNA damage response; and ultimately cellular senescence, a state in which cells permanently stop dividing but refuse to die, instead secreting a inflammatory cocktail known as the senescence-associated secretory phenotype.

At the heart of this senescence program, the team identified the p53–p21 signaling axis as the central mediator. p53 is the cell’s guardian of the genome, a transcription factor that responds to DNA damage by either halting the cell cycle or initiating cell death. When p53 is activated, it upregulates p21, a cyclin-dependent kinase inhibitor that enforces cell cycle arrest. In endothelial cells exposed to H5, this pathway was switched on, driving the cells into the senescent state. The importance of this axis was confirmed in vivo: in mouse models, H5-induced vascular dysfunction promoted a pro-atherogenic phenotype, and this effect was mediated centrally by the same p53–p21 pathway. The convergence of in vitro and in vivo evidence on a single molecular mechanism lends the findings considerable weight.

The concept of endothelial senescence as a driver of vascular aging has been gaining momentum in the geroscience community. Senescent endothelial cells lose their ability to produce nitric oxide, the signaling molecule that keeps blood vessels dilated and prevents platelets and immune cells from sticking to vessel walls. They also secrete pro-inflammatory cytokines and matrix-degrading enzymes that destabilize atherosclerotic plaques. By showing that a specific lipoprotein subfraction can induce this program through a defined signaling pathway, the study connects lipid biochemistry to the biology of aging in a way that few previous investigations have managed. It also echoes earlier work by some of the same investigators on electronegative low-density lipoprotein, which has been shown to induce mitochondrial dysfunction and premature senescence of vascular cells, suggesting that charge-defined subfractions of both major lipoprotein classes may share senescence-inducing properties.

The translational implications are substantial. If H5 can be reliably measured in clinical laboratories, it could serve as a biomarker for identifying asymptomatic individuals who harbor silent, progressing atherosclerosis despite apparently acceptable conventional lipid profiles. More ambitiously, the identification of the p53–p21 axis as the central mediator raises the possibility of pharmacological intervention, whether by reducing the formation of H5, blocking its interactions with endothelial cells, or modulating the downstream senescence program. The study’s authors argue that their findings validate targeting HDL quality, specifically the H5 subfraction, as a novel therapeutic strategy, a reframing that could finally explain why simply raising HDL cholesterol has failed to improve outcomes in large clinical trials.

Caveats remain, as they always do. The human cohorts were cross-sectional, so the associations between H5 and carotid atherosclerosis, while statistically independent, do not by themselves prove causation in people. The mouse experiments support a causal mechanism, but the extent to which the same pathway operates in human arteries over decades will require longitudinal studies. Still, the work represents a compelling synthesis of epidemiology, proteomics, cell biology, and animal physiology, and it arrives amid renewed interest in lipoprotein(a) as a drug target and in senolytic therapies that clear senescent cells from aging tissues. If future studies confirm that H5 is both a reliable marker and a treatable mediator of vascular aging, the humble HDL particle, long viewed as a one-dimensional hero of cardiovascular health, may turn out to be a far more complicated character, one whose darkest fractions hold the key to keeping arteries young.

Subject of Research: The role of apolipoprotein(a)-rich electronegative HDL subfraction H5 in inducing endothelial senescence and accelerating vascular aging and atherosclerosis

Article Title: Apolipoprotein(a)-rich electronegative HDL accelerates vascular aging and atherosclerosis by inducing endothelial senescence

Article References: Hsu, W.-L., Chung, C.-P., Chung, C., Wei, W.-Y., Chen, T.-Y., Akyol, O., Chiang, H.-H., Chou, M.-C., Kraler, S., Lüscher, T., Tsai, M.-H., & Chen, C.-H. (2026). Apolipoprotein(a)-rich electronegative HDL accelerates vascular aging and atherosclerosis by inducing endothelial senescence. GeroScience. https://doi.org/10.1007/s11357-026-02523-1

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02523-1

Keywords: HDL, H5 subfraction, apolipoprotein(a), endothelial senescence, p53-p21 pathway, atherosclerosis, vascular aging, metabolic syndrome, cholesterol efflux, reactive oxygen species, carotid intima-media thickness, cardiovascular disease

The researchers set out to resolve a puzzle that has shadowed nutrition science for years. Protein is indispensable, fueling muscle growth, immune regulation, and bone development, yet large epidemiological studies have linked very high protein intake to elevated all-cause mortality and to age-related conditions such as chronic kidney disease and type 2 diabetes. Meanwhile, dozens of experiments in organisms from yeast to mice have shown that restricting protein extends life. What has been missing is a dynamic, mechanistic account of how excess protein actually promotes aging across the lifespan, rather than a snapshot taken at a single moment in time.

To fill that gap, the team turned to Drosophila melanogaster, the fruit fly, a classic aging model whose short life makes lifelong observation practical. They fed flies a series of six diets with identical total calories but protein energy supplies ranging from 5 to 30 percent, carefully adjusting glucose so that only the protein-to-carbohydrate ratio changed. The result was a striking inverted U-shaped curve. Flies on the 10 percent protein diet lived longest, with a median lifespan of 75 days. As protein climbed, lifespan fell in a dose-dependent manner, dropping to just 54 days at 30 percent protein. Even the extreme 5 percent diet shortened life, confirming that both too little and too much protein are harmful. Food intake measurements ruled out the possibility that flies on high-protein diets were simply eating more calories, and climbing tests showed the effect was not an artifact of general frailty at the start of the intervention.

With the lifespan effect established, the researchers deployed a formidable multi-omics arsenal. They sequenced the transcriptomes of flies at day 18, representing early life, and day 48, representing middle-to-late life, across all five protein levels, and complemented this with quantitative proteomics and amino acid metabolic profiling. By correlating the expression of every gene with lifespan grades across the dietary spectrum, they narrowed thousands of candidates down to a shortlist of genes that responded consistently to high protein at both life stages. Pathway analysis kept pointing to one metabolic hub: the glycine, serine, and threonine metabolism pathway, which was strongly and persistently activated by high-protein diets at both the RNA and protein levels, and whose activity scores correlated negatively with lifespan with Spearman coefficients as high as minus 0.97.

Within that pathway, a protein interaction network analysis flagged one gene as the top-ranked hub: CG6415, the fly homolog of the human AMT gene. Its expression rose steadily as dietary protein increased and lifespan fell, and it was also among a set of 150 genes whose expression changed in the same direction during natural aging, suggesting that the diet essentially hijacks a program the animal already runs as it grows old. To test causality, the team generated flies in which CG6415 was either deleted entirely or overexpressed throughout the body. The results were decisive. Knocking out CG6415 extended the median lifespan of flies on the 30 percent protein diet by 15.7 percent and restored the activity of antioxidant enzymes such as superoxide dismutase and catalase, which the high-protein diet had suppressed. Conversely, forcing CG6415 expression on a normal 10 percent protein diet shortened median lifespan by 22 percent, mimicking the effect of a high-protein diet without any change in nutrition. Combining overexpression with a high-protein diet produced the worst survival of all, a clear additive interaction confirmed statistically by two-way analysis of variance.

The mechanism, the omics data indicated, centered on oxidative phosphorylation, the mitochondrial process that converts nutrients into ATP. High-protein diets suppressed the oxidative phosphorylation pathway, activated senescence-related signaling through the p53 pathway, and dampened electron transport and ion transport, all changes that CG6415 knockout reversed. ATP levels told the same story: they fell significantly in high-protein-fed flies and were partially restored by deleting CG6415. Because oxidative phosphorylation is the core function of mitochondria, the team reasoned that CG6415 must be acting on mitochondrial homeostasis itself.

To test that idea in a mammalian context, the researchers moved to human embryonic kidney 293T cells, a validated model for mitochondrial and aging studies, and manipulated AMT, the human counterpart of CG6415. Overexpressing AMT reduced the activities of mitochondrial respiratory chain complexes I, II, III, and V, lowered cellular ATP, collapsed the mitochondrial membrane potential, and flooded the cells with reactive oxygen species, including mitochondria-specific superoxide detected with the MitoSOX probe. Senescence markers followed: senescence-associated beta-galactosidase staining increased, inflammatory genes such as TNF-alpha, IL-1 beta, and IL-6 were upregulated, and the canonical p53-p21 senescence pathway switched on at both the mRNA and protein levels. In the reverse experiment, silencing AMT with siRNA in cells stressed by hydrogen peroxide restored complex V activity, ATP production, and membrane potential, reduced ROS, and blunted the p53-p21 response, demonstrating that the AMT-ROS-p53-p21 axis is a genuine conduit from mitochondrial dysfunction to cellular senescence.

The final question was which component of dietary protein drives the effect. Proteins are built from twenty amino acids, so the team profiled the amino acid pools of high-protein-fed flies and then supplemented each amino acid individually onto the baseline 10 percent protein diet. Three of them, isoleucine, valine, and phenylalanine, shortened lifespan significantly, by roughly five to six days, while several others, including threonine, methionine, and glycine, actually extended it. Molecular docking showed that all three lifespan-shortening amino acids can bind the CG6415 protein, but only isoleucine reliably upregulated the gene in the fly thorax and abdomen and impaired both oxidative and heat stress resistance. Crucially, CG6415 knockout rescued the lifespan reduction caused by isoleucine supplementation, extending median lifespan by nine days, and lowering dietary isoleucine within a high-protein diet extended lifespan in control flies but not in CG6415-overexpressing ones. Isoleucine also reproduced the dose-response relationship of the full high-protein diet, with lifespan shortening progressively as supplementation increased. Together, these experiments position isoleucine as the key amino acid through which high-protein diets activate CG6415 and promote aging, a finding that resonates with earlier mouse studies showing that dietary isoleucine restriction extends healthspan and lifespan.

The authors are careful about the limits of their work. The study relied primarily on flies, with human cells used only for mechanistic verification, and organ-specific studies in mammals remain to be done. Individual amino acid supplementation only partially reproduced the high-protein effect, hinting that protein’s impact on aging emerges from the combined action of multiple amino acids rather than any single one. The researchers also focused on pathways uniformly regulated across two life stages, leaving stage-specific effects for future exploration. Still, the implications are hard to ignore. At a time when protein supplements are marketed aggressively to adolescents, fitness enthusiasts, and older adults alike, the study offers a cautionary counterweight: sustained excessive protein intake, particularly of isoleucine-rich foods, may quietly erode mitochondrial function and accelerate the very aging process that health-conscious consumers are trying to delay. The identification of CG6415/AMT as a druggable node in this pathway, and of isoleucine as its dietary trigger, opens a concrete path toward precision nutrition, in which protein quality and amino acid composition, not just quantity, become the targets of anti-aging dietary design.

Subject of Research: Mechanism by which high-protein diets accelerate aging through CG6415/AMT gene activation and mitochondrial dysfunction

Article Title: High-protein diet promotes aging by activating the CG6415 / AMT gene and disrupting mitochondrial homeostasis

Article References: Xu, X., Zheng, W., Liu, Q., Li, Y., Yang, S., Zhou, R., Wang, Y., Qi, X., Zhang, C., Zhang, F., Wu, Y., Li, Y., & Li, Y. (2026). High-protein diet promotes aging by activating the CG6415/AMT gene and disrupting mitochondrial homeostasis. Journal of Advanced Research, 88, 995-1012. https://doi.org/10.1016/j.jare.2026.01.063

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.01.063

Keywords: high-protein diet, aging, lifespan, Drosophila melanogaster, CG6415, AMT gene, mitochondria, oxidative phosphorylation, isoleucine, reactive oxygen species, p53-p21 pathway, nutrition