The investigation began with a human clue. The team analyzed 257 community-dwelling Han Chinese adults aged 50 and older who underwent comprehensive cognitive assessment using the Montreal Cognitive Assessment, a screening tool considered more sensitive than the Mini-Mental State Examination for detecting early deficits. Among a panel of energy metabolism indicators, including blood glucose, creatinine, Klotho, and the albumin/globulin ratio, ghrelin showed the strongest correlation with cognitive scores. Higher circulating ghrelin levels were associated with poorer cognitive performance, and the relationship held after accounting for age, sex, and education. Notably, the association was sex-dependent: women with mild cognitive impairment had significantly higher ghrelin levels than cognitively normal women and than men at the same stage. The authors interpret this elevation not as evidence that ghrelin damages cognition, but as a possible compensatory response to metabolic stress, a biomarker of a brain under siege rather than a culprit.

To test what ghrelin actually does, the researchers turned to two mouse models. The first compared young two-month-old animals with nine-month-old mice, capturing an early stage of natural aging. The second used chronic injection of D-galactose, a sugar that accelerates senescence across tissues and is a widely used chemical model of aging. In both models, behavioral testing revealed clear deficits. In the novel object location and novel object recognition tests, aged and D-galactose-treated mice spent less time exploring objects in new positions or objects they had never seen, indicating impaired spatial and recognition memory. In the Morris water maze, they took longer to find a hidden platform, a classic sign of compromised hippocampal learning.

Beneath these behavioral changes lay a striking cellular signature. Western blotting of hippocampal tissue showed upregulation of the senescence markers p16 and p21 and the DNA damage marker gamma-H2AX, alongside loss of Lamin B1, a nuclear envelope protein that declines as cells age, and reduced HMGB1, a chromatin-associated protein. Immunofluorescence co-localization pinpointed these changes within Iba1-positive microglia in the hippocampal CA1 and CA3 regions, confirming that the brain’s innate immune cells were themselves senescing. At the same time, enzyme-linked immunosorbent assays revealed a flood of inflammatory mediators in the hippocampus, including IL-1alpha, IL-1beta, IL-6, IL-8, CXCL10, MCP1, and M-CSF, an inflammaging profile consistent with the senescence-associated secretory phenotype that aged microglia are known to adopt. Both total and acylated ghrelin were elevated in the plasma of these animals, mirroring the human data.

The therapeutic experiment followed. D-galactose-treated mice received daily ghrelin injections at either 20 or 80 micrograms per kilogram during the final four weeks of aging induction, and the same regimen was applied to naturally aged mice. The results were consistent across both models: ghrelin-treated animals performed significantly better in all three behavioral tests, with the higher dose producing the greatest benefit. Molecular analysis showed that ghrelin suppressed p16, p21, and gamma-H2AX while restoring Lamin B1 and HMGB1, effectively reversing the senescence signature. Immunofluorescence confirmed fewer senescent microglia, and the inflammatory cytokine storm in the hippocampus subsided. Interestingly, the protection extended beyond immune cells, as gamma-H2AX signals in neurons also declined after treatment, though astrocytes showed minimal senescence marker co-localization throughout.

What made this outcome puzzling was the receptor. Ghrelin’s classical receptor, GHSR, was expected to mediate any benefit, yet high-dose ghrelin actually reduced GHSR membrane localization, a sign of receptor desensitization, and only the low dose boosted the p-CaMKII/CaMKII ratio that reflects GHSR-driven synaptic plasticity. Even more tellingly, when the researchers knocked down GHSR in D-galactose-treated primary microglia, ghrelin still suppressed p16, p21, and gamma-H2AX. The anti-senescent effect, in other words, was largely GHSR-independent, pointing to some other molecular intermediary.

To find it, the team deployed network pharmacology, cross-referencing predicted ghrelin targets with genes linked to cognitive impairment and clustering the resulting protein-protein interaction network. Five hub genes emerged: SHBG, SRC, C5AR1, KLF4, and BRCA1. Of these, sex hormone-binding globulin, or SHBG, responded most consistently to ghrelin in vivo. SHBG is classically known as a blood protein that binds sex hormones, but elevated levels have previously been linked to hippocampal atrophy and cognitive decline in clinical studies. Immunofluorescence showed SHBG localized in the cytoplasm of BV2 microglial cells, and molecular docking predicted a physical interaction between ghrelin and SHBG, which co-immunoprecipitation in primary microglia then validated. D-galactose exposure raised hippocampal SHBG, and ghrelin lowered it in a dose-dependent fashion.

The downstream circuit came into focus through transcriptomics and targeted manipulation. RNA sequencing of ghrelin-treated microglia revealed 373 upregulated and 431 downregulated genes, with gene set enrichment analysis positively scoring autophagy pathways. Ghrelin reduced the autophagy substrate p62 while increasing Beclin1 and the LC3-II/LC3-I ratio, hallmarks of enhanced autophagic flux, the cellular recycling process that keeps senescent cells from accumulating damaged components. When the researchers overexpressed SHBG in microglia, the opposite occurred: p62 rose, Beclin1 and LC3 fell, and senescence markers worsened. SHBG knockdown increased JNK1 phosphorylation while SHBG overexpression reduced it, placing JNK1 downstream of SHBG. Blocking JNK1 with a pharmacological inhibitor abolished ghrelin’s ability to raise Beclin1 and LC3, and critically, combining JNK1 inhibition with SHBG overexpression produced no additional suppression, confirming that the two act in a single linear pathway. Finally, forcing Beclin1 expression partially rescued the senescent phenotype caused by SHBG overexpression, completing the picture of a SHBG/JNK1/Beclin1 axis that ghrelin engages to restore autophagy and push microglia back toward a youthful, homeostatic state.

The authors are careful about the limits of their work. The D-galactose and nine-month-old mouse models cannot fully recapitulate human cognitive impairment, the animal experiments used only male mice even though the human data revealed sex-dependent ghrelin patterns, and the long-term safety of ghrelin administration remains untested in larger animals or clinical trials. Some autophagy-related genes, including ERK2, PRKAA1, and CTSD, were untouched by the hormone, suggesting the effect is pathway-specific rather than a blanket activation of the autophagy network. Even so, the study delivers a compelling conceptual advance: a gut-derived metabolic hormone can act on brain immune cells through a non-canonical, receptor-independent route, damping the senescence-associated secretory phenotype that drives neuroinflammation. If the SHBG/JNK1/Beclin1 axis behaves similarly in human microglia, it could open a new class of therapeutic targets for age-related cognitive decline, a condition for which disease-modifying treatments remain desperately lacking despite decades of effort focused almost exclusively on neurons and amyloid.

Subject of Research: Ghrelin regulation of microglial senescence and autophagy in aging-related cognitive impairment

Article Title: Ghrelin Alleviates Aging‐Related Cognitive Impairment by Regulating Autophagy‐Related Signaling via the SHBG/JNK1/Beclin1 Axis in Microglia

Article References: Ghrelin Alleviates Aging‐Related Cognitive Impairment by Regulating Autophagy‐Related Signaling via the SHBG/JNK1/Beclin1 Axis in Microglia. (n.d.). https://doi.org/10.1111/acel.70732

Image Credits: AI Generated

DOI: 10.1111/acel.70732

Keywords: ghrelin, microglia, cognitive impairment, autophagy, SHBG, JNK1, Beclin1, immunosenescence, neuroinflammation, brain aging, D-galactose, Aging Cell

Sertoli cells are the architectural and metabolic backbone of the seminiferous tubules, the coiled structures inside the testis where sperm are made. Each Sertoli cell extends from the basement membrane to the tubule lumen and physically cradles developing germ cells at every stage of their maturation, from spermatogonial stem cells through spermatocytes and spermatids to fully formed sperm. Beyond structural support, these cells supply nutrients, regulate the local hormonal environment, and maintain the polarity of the seminiferous epithelium. They also perform a housekeeping task that is easy to overlook: phagocytosing residual bodies, the excess cytoplasm discarded by spermatids as they transform into streamlined spermatozoa. Without this continuous clearance and recycling, the tubule becomes cluttered and germ cell development stalls.

A defining structure in this system is the blood-testis barrier, a constellation of tight junctions between adjacent Sertoli cells near the base of the tubule. The barrier partitions the seminiferous epithelium into basal and adluminal compartments, shielding meiotic and post-meiotic germ cells from the bloodstream and from the immune system, which would otherwise recognize haploid sperm antigens as foreign. The integrity of this barrier depends on junctional proteins such as Claudin-11, a claudin family member that is highly expressed in Sertoli cells and is required for normal barrier function. Disrupting the barrier does not merely expose germ cells to immune attack; it also destabilizes the polarized architecture that germ cells need to advance through the epithelium.

Beclin1, encoded by the Becn1 gene, is a core component of the autophagy initiation complex. Autophagy begins when a cup-shaped membrane, the phagophore, sequesters cytoplasmic cargo and seals into a double-membraned autophagosome, which then fuses with lysosomes for degradation. Beclin1 partners with the lipid kinase PIK3C3 (also known as VPS34) to nucleate this process, and its activity is modulated by interacting proteins such as Rubicon, which suppresses autophagic degradation, and ULK1, which initiates it. Because complete loss of Beclin1 is lethal early in embryonic development, researchers have had to rely on tissue-specific knockout strategies to probe its function in adult organs, and the testis has proven a particularly informative setting.

The Beijing team, led by Yuqing Cai and corresponding authors Yinghe Qin and Yingjie Wu, generated mice in which Becn1 was deleted only in Sertoli cells. The conditional knockout males were fertile in early adulthood, but their reproductive performance declined sharply. At nine weeks of age—the onset of full sexual maturity in the mouse—they sired fewer offspring and produced sperm of reduced quality. Histological examination of their testes revealed vacuolated seminiferous tubules, a hallmark of epithelial disorganization in which fluid-filled cavities disrupt the orderly layers of germ cells. By twelve weeks, the mice were completely infertile, indicating a progressive degeneration rather than a static developmental defect.

The cellular explanation for this collapse lay in two interlocking failures. First, the blood-testis barrier was compromised: the knockout testes showed disrupted barrier integrity and reduced expression of Claudin-11, the tight junction protein that helps seal the epithelium. Second, autophagy itself was clearly impaired. The researchers measured the ratio of LC3-II to LC3-I, a standard biochemical readout of autophagosome formation in which the soluble LC3-I protein is lipidated to membrane-bound LC3-II as autophagosomes assemble. In the absence of Beclin1, this ratio fell, demonstrating that Sertoli cells could no longer form autophagosomes efficiently. The autophagic flux that normally clears damaged organelles, protein aggregates and phagocytosed residual bodies had been throttled at its initiation step.

These results dovetail with a growing body of evidence that autophagy is not a generic housekeeping pathway in the testis but a process with specific, stage-specific reproductive duties. Previous work has shown that the autophagy protein ATG5 is required for the development of elongating spermatids, sperm individualization and normal male fertility, while Atg7 is essential for acrosome biogenesis, the construction of the enzyme-filled cap that sperm need to penetrate an egg. In Sertoli cells, autophagy has been implicated in the assembly of ectoplasmic specializations, the actin-based adhesive junctions that anchor spermatids, and in the regulation of cell polarity through PIK3C3’s control of the actin-severing protein scinderin. Conversely, the autophagy suppressor Rubicon promotes Sertoli cell function by preventing the degradation of the transcription factor GATA4, illustrating that the pathway must be tuned, not merely maximized.

What makes the new study notable is its focus on the initiation machinery rather than the downstream execution proteins. Earlier work from the same group had shown that Beclin1 is vital for spermatogenesis and male fertility when studied more broadly; the present study sharpens the picture by deleting the gene exclusively in Sertoli cells and tracing the resulting pathology to barrier disruption and failed autophagosome formation. This matters because Sertoli cell dysfunction is increasingly recognized as a contributor to unexplained male infertility in humans. While many cases of poor sperm quality are attributed to the germ cells themselves, the new data reinforce the idea that the somatic niche can be the primary fault line: when the nurse cells falter, the germ cells they support fail secondarily.

The study also connects autophagy to the metabolic economics of the tubule. Sertoli cells metabolize glucose into lactate, which they export to germ cells as a preferred fuel, and recent work in Tibetan sheep has shown that BECN1-mediated autophagy activates the glycolytic pathway that drives this lactate synthesis. A Sertoli cell stripped of Beclin1 may therefore be compromised not only in waste clearance and junction maintenance but also in metabolic provisioning, compounding the stress on developing germ cells. The vacuolation observed in the knockout tubules is consistent with such a multi-system failure, in which barrier breakdown, impaired phagocytosis and metabolic shortfall reinforce one another.

For now, the findings are confined to mice, and translating them to human fertility medicine will require caution. Yet they suggest concrete directions for research: screening for impaired autophagic flux in Sertoli cells of infertile men, exploring whether environmental factors known to perturb autophagy also affect barrier integrity, and investigating whether pharmacological modulation of the pathway could protect the niche. The work, supported by approved animal protocols at China Agricultural University and published as an open record with all data contained in the article, adds Beclin1 to the short list of genes whose deletion in Sertoli cells alone is sufficient to render a male mouse infertile. In the intricate economy of the seminiferous tubule, it appears the janitors are as indispensable as the workers they serve.

Subject of Research: The role of the autophagy protein Beclin1 in Sertoli cell function and mouse spermatogenesis

Article Title: Beclin1 Regulates Sertoli Cell Function to Maintain Mouse Spermatogenesis

Article References: Beclin1 Regulates Sertoli Cell Function to Maintain Mouse Spermatogenesis. (n.d.). https://doi.org/10.1007/s43032-026-02202-8

Image Credits: AI Generated

DOI: 10.1007/s43032-026-02202-8

Keywords: autophagy, Beclin1, Sertoli cells, spermatogenesis, blood-testis barrier, male infertility, Claudin-11, LC3, knockout mice, sperm quality, seminiferous tubules, reproductive biology