The cocaine- and amphetamine-regulated transcript (CART) peptide is widely expressed throughout the mammalian central nervous system. CART was first identified during sequencing of a hypothalamic peptide whose biological function was unknown at the time. Subsequent studies used immunohistochemistry to detect CART peptides and in situ hybridization to localize the corresponding messenger ribonucleic acid (mRNA) in several species, including rats, mice, non-human primates, and humans. Additional investigations have examined the neurotransmitters that are co-localized with CART peptides. Accumulated evidence indicates that CART peptides participate in diverse physiological processes, including addiction, reward, pain modulation, memory, sleep, hormonal regulation and the energy homeostasis. A clearer understanding of the widespread distribution of CART peptides is therefore essential for elucidating their functional roles. Accordingly, this review summarizes recent findings on the distribution of CART peptides in the aim of this review is to summarize recent findings regarding the distribution of CART peptides within the central nervous system of rodents, non-human primates, and humans, with particular emphasis on interspecies differences as abasis for identifying future research priorities. Accordingly, this review summarizes recent findings on the distribution of CART peptides within the central nervous system of rodents, non-human primates, and humans, with particular emphasis on interspecies differences as a basis for identifying future research priorities.
Tuberculosis (TB) continues to be a significant worldwide health issue, with the rise of drug-resistant forms presenting substantial obstacles to successful treatment. The Mycobacterium tuberculosis (Mtb) enzyme catalase-peroxidase G (KatG) is a crucial molecular determinant of resistance, as it is necessary for the activation of isoniazid and for safeguarding the bacteria against oxidative stress. Mutations in KatG are a key mechanism of isoniazid resistance, contributing to the development of multidrug-resistant tuberculosis, hence establishing KatG as a crucial protein target for novel therapeutic approaches. This study focused on KatG to identify novel antimicrobial peptides (AMP) which were designed using rational changes of the host-defence peptide LL-37 to improve their efficacy against M. tuberculosis. A library of 15 antimicrobial peptides was designed using LL-37 modifications and categorized into three classes: Class I, Class II, and Class III. Peptide structures were predicted and docked against KatG resulting in top antimicrobial peptides. Molecular docking identified three top peptides P3 (-235.28 binding score), A5ζ (-229.42), and A4η (-233.81), with strong binding affinity with KatG active site residues. Further, molecular dynamic (MD) simulation was performed for 100 ns on these top three protein-peptide complexes. MD simulation showed distinct stability profiles majorly with P3 showing exceptional conformational stability. Additionally, safety assessment verified no-toxic, non-allergenic, favorable physicochemical and ADME properties. The computationally designed antimicrobial peptides (P3, A5ζ, and A4η) demonstrated strong binding affinity toward KatG. These interactions suggest their potential to interfere with key mycobacterial enzymatic functions and may contribute to strategies aimed at addressing existing drug resistance mechanisms.
Experimental and quantitative methods for studying protein-graphene interactions remain limited, despite their importance for biosensing and biointerface engineering. Here, we report Fluoro4Graphene, a three-step high-throughput fluorescence-based screening assay for the identification of graphene-binding peptides. In this platform, candidate peptides are genetically fused to the phytase of Yersinia mollaretti, which serves as a reporter enzyme by converting 4-methylumbelliferyl phosphate into the fluorescent 4-methylumbelliferone. Robust signal quantification is achieved by transferring the soluble fluorophore to a secondary microtiter plate prior to detection, thereby avoiding graphene-induced fluorescence. The assay is performed directly from crude Escherichia coli lysates in microtiter plates coated with electrochemically exfoliated graphene flakes, eliminating protein purification steps and enabling high sample throughput. The platform exhibits good reproducibility, with a coefficient of variation of approximately 17%, allowing reliable discrimination of small differences in binding. Analytical performance was validated in a directed evolution campaign targeting the material binding peptide Macaque histatin-1, yielding variants with improved graphene surface coverage. The best variant showed a 1.44-fold improvement in the Fluoro4Graphene screening assay. Independent validation using surface plasmon resonance on high-purity graphene confirmed an increase in surface coverage from 106.19 ng/cm2 to 154.10 ng/cm2. Overall, Fluoro4Graphene provides a robust, reproducible, and scalable analytical tool for the quantitative assessment of protein-graphene interactions.
From a historical perspective, long non-coding RNAs (lncRNAs) represent a relatively short story. However, this story has many plot lines, thrills, twists, and turns that altogether form quite a long saga of its own. lncRNAs stay at the forefront of a recent paradigm shift from a protein-only world to the mysterious RNA world, the enormous complexity of which we are only beginning to appreciate. Here, we review the most enigmatic aspect of lncRNAs, their coding ability in the context of whole-cell regulation. What peptides do lncRNAs encode as true translons? What is the mechanism of their translation? What roles do these ncRNA-encoded peptides (ncPEPs) play during differentiation and development and in distinct pathologies? Do these ncPEPs contribute to the already known regulatory roles of lncRNAs? Shouldn't we coin the coding subset of lncRNAs its apt name: cryptic long non-coding RNAs (crpt-lncRNAs) for their cryptic coding capacity? These and other questions concerning these current winners of the spotlight in molecular biology, which await resolution, are discussed so that molecular history can be rewritten once again.
Prion and prion-like proteins are classically associated with protein misfolding, but amyloidogenic sequences can also participate in host defence. Here, using deep learning, we screened 19.3 million fragments from 2,897 curated prion-related proteins and identified 1,179 candidate antimicrobial peptides, which we term prionins. Among 75 synthesized prionins, 59 inhibited bacterial pathogens, 53 perturbed membranes and 2 reduced Acinetobacter baumannii infection burden in mice.
Microplastics (MP) and particulate matter (PM) are pervasive environmental contaminants that pose significant threats to intestinal homeostasis. This study systematically investigated the individual and combined effects of MP and PM on intestinal injury using complementary in vivo and in vitro models. In mice, co-exposure to MP and PM induced pronounced oxidative stress, intestinal inflammation, disruption of epithelial barrier integrity, mucin accumulation, activation of endoplasmic reticulum (ER) stress, and dysregulation of autophagy. Consistently, in C2BBe1 intestinal epithelial cells, combined exposure significantly reduced cell viability and exacerbated oxidative stress, ER stress, and autophagic imbalance, as evidenced by increased reactive oxygen species (ROS), elevated BiP and ATF6 expression, and accumulation of p62 and LC3B-II. Moreover, co-exposure promoted intestinal inflammation, barrier dysfunction, and mucin accumulation, demonstrated by increased ICAM-1, IL-1β, IL-6, and TNFα levels, reduced ZO-1 expression, and upregulated MUC2 expression. Strikingly, combined exposure-induced mucin accumulation may provide physical protection and compensate for barrier disruption. Notably, pretreatment with kefir peptides (KPs) markedly attenuated these deleterious effects in vivo and in vitro, supporting their protective potential. KPs pretreatment alleviated cytotoxicity by reducing oxidative and ER stress markers and normalizing autophagy-related protein expression. In addition, KPs decreased ICAM-1 levels, restored epithelial barrier integrity, and limited mucin accumulation in intestinal cells. Collectively, these findings demonstrate that concurrent exposure to MP and PM exacerbates intestinal injury through coordinated activation of oxidative stress, ER stress, and dysregulated autophagy pathways, and identify KPs as a promising preventive strategy for mitigating pollutant-induced intestinal damage.
One major barrier inhibiting most pharmaceutical administrations' effectiveness is the cellular membrane's insufficient permeability. Cell-penetrating peptides (CPPs) are extensively identified as effective biological carriers that can pass through this natural barrier and transport the CPPs-conjugated therapeutic agents into cells. In this line, CPPs-assisted delivery systems have become one of the most popular methods for internalizing nanoparticles (NPs). Recently, CPPs-functionalized PLGA-derived nanocarriers have attracted exceptional attention because of their distinctive features that make them highly appealing for use in next-generation drug delivery systems (DDS). CPPs-conjugated PLGA NPs have demonstrated promise as therapeutic agents in a range of medical fields. This review article summarizes the current development of the CPPs/PLGA nanocarriers. After that, we explore their various challenges and optimization techniques. Finally, future prospects and challenges of CPPs/PLGA nanocarriers are mentioned concisely.
This study aimed to determine the optimal cultivation conditions for four Escherichia coli strains producing recombinant glucagon-like peptide-1 tandems. Validation experiments confirmed that scale-up from shake flasks to a bioreactor is feasible without a significant loss in specific productivity. We also demonstrated that the optimal cultivation conditions were identical for all tested strains. However, the number of glucagon-like peptide-1 monomers in the tandem affected the final yield in both shake flasks and the bioreactor. We also evaluated the target protein fraction in the wet inclusion bodies obtained. The amount of inclusion bodies per gram of biomass was found to correlate with specific productivity, while the target protein fraction in wet inclusion bodies varied among the different tandems. A correlation was identified between the titer of the glucagon-like peptide-1 tandems and the number of monomers. The results indicate that selecting an appropriate number of monomers during strain development can enhance productivity, improve the target protein fraction in wet inclusion bodies, and increase the final product titer after downstream processing.
MTA-cooperative inhibition of protein arginine methyltransferase 5 (PRMT5) is synthetic lethal with methylthioadenosine phosphorylase (MTAP)-deficient cancers. PRMT5's enzymatic activity can be assessed by measuring symmetric dimethylarginine (SDMA) modification levels of protein substrates. However, conventional assays that attempt to measure total SDMA levels lack the specificity to measure individual PRMT5 substrates, and thus potentially reduce selectivity and sensitivity. This study aims to identify and characterize specific DMA peptides that can serve as clinical pharmacodynamic (PD) biomarkers for PRMT5 inhibition in formalin-fixed paraffin-embedded solid tumors, leveraging data-independent acquisition-mass spectrometry (DIA-MS)-based global proteomics without additional DMA enrichment. We evaluated 145 DMA peptides in xenograft models treated by a novel MTAP-selective PRMT5 inhibitor, AZD3470. Arginine dimethylation of G3BP1 at residue R460 (G3BP1(R460)) was identified as the primary PD biomarker for PRMT5 inhibition due to its high abundance and significant post-treatment reduction that correlated with dose. The global proteomics assay with a limit of detection/quantification characterized the quantitative performance and allowed for confident detection of G3BP1(R460). Using this quantitative assay, more than 90% reduction in G3BP1(R460) modification at 100 mg/kg was reproducibly detected in MTAP-null xenograft models. Our findings suggested that the DIA-MS proteomics assay can provide high specificity and sensitivity in the detection of PRMT5 inhibition.
Many neuropsychiatric disorders involve dysregulation of the dopaminergic (DA) input to the forebrain. Of particular relevance are DA afferents from the midbrain ventral tegmental area (VTA). A key neuromodulatory influence onto DAVTA neurons arises from lateral hypothalamic area hypocretin/orexin (OX) neurons. Despite being a major input, the differential actions of OX peptides A and B on their receptors (OX1R and OX2R) in DA neurons is poorly understood. Using genetically engineered mice whose DA cells selectively lack OX input via Hcrtr1 (DAOx1R-KO) or Hcrtr2 (DAOx2R-KO), we assessed DAVTA neuron intrinsic excitability ex vivo, and evaluated behavioral phenotypes across socio-emotional and cognitive domains. We discovered previously unrecognized effects of OX peptides on DAVTA cell response. While OXA enhanced DAVTA neuron firing via OX1R, OXB diminished firing via OX2R. Behaviorally, DA OX1R loss generated anxiety-like responding and context-dependent hyperactivity, while DA OX2R loss decreased sociability and compromised aversion-driven learning. Loss of either OX1R or OX2R in DA cells elicited impulsivity and compulsivity-like behavioral patterns. We evidence distinct functions of OX1R vs OX2R signaling in modulating the intrinsic excitability of DAVTA neurons, and influencing DA-related behaviors. Our data implicate OX→DA signaling pathways in neuropsychiatric endophenotypes relevant to obsessive-compulsive, attention-deficit/hyperactivity, and autism spectrum disorders, and inform therapeutic strategies targeting orexin receptors.
Transthyretin (TTR) amyloidosis is one of the most common forms of systemic amyloidosis, involving deposits of pathogenic TTR aggregates in tissues and organs throughout the body. TTR aggregation is initiated by the dissociation of a native TTR tetramer into a monomeric intermediate, which subsequently misfolds and assembles into insoluble aggregates. Using an efficient 19F-NMR aggregation assay, we previously showed that designed peptide inhibitors can interact with multiple TTR species. However, quantifying species-specific binding affinities has remained difficult because the populations of these TTR species change over time and include a low-abundance monomeric intermediate. Here, we develop a quantitative method to extract species-dependent binding affinities directly from population-resolved 19F-NMR aggregation data. Using diflunisal as a model compound, we determine its binding affinities for both the tetramer and the monomeric intermediate under acidic, aggregating conditions. At acidic pH, tetramer binding becomes approximately two-fold tighter, and monomer binding becomes 15-fold stronger, compared to neutral pH. We then apply this method to previously collected 19F-NMR aggregation data for designed peptide inhibitors. The results show that concatenating two capping peptides increases their binding affinity to both TTR tetramers and monomeric intermediates by about two-fold, relative to the same peptides mixed separately at equal concentrations. Our method enables direct, quantitative comparison of species-dependent inhibitor binding, providing mechanistic insights useful for designing and optimizing TTR aggregation inhibitors.
The rising global burden of diabetes mellitus necessitates exploration of mechanisms beyond classical pancreatic dysfunction. The gut-pancreas-metabolism axis has emerged as a central regulatory network linking gut microbiota, enteroendocrine signaling, immune modulation, and pancreatic function in glucose homeostasis. Gut-derived bioactive metabolites, including short-chain fatty acids, bile acid derivatives, indole compounds, lipopolysaccharide fragments, and microbial peptides, significantly influence insulin secretion, insulin sensitivity, inflammation, and energy metabolism. These metabolites regulate key pathways such as AMP-activated protein kinase, PI3K/Akt signaling, G-protein-coupled receptor activation, and inflammatory cascades, thereby contributing to β-cell preservation and metabolic balance. Dysbiosis-associated shifts in microbial metabolite profiles are strongly associated with insulin resistance, impaired incretin responses, and chronic low-grade inflammation in type 2 diabetes. This review summarizes recent mechanistic advances in the gut-pancreas-metabolism axis and highlights the therapeutic potential of microbiota-derived bioactive compounds. Furthermore, it discusses emerging translational strategies, including probiotics, prebiotics, postbiotics, and dietary modulation of the gut microbiome, as adjunctive approaches for diabetes management. Targeting this axis provides promising opportunities for precision-based metabolic therapy in diabetes care.
Proteases are enzymes that catalyze the hydrolysis of peptide bonds in proteins for their functional modification or degradation. Members of the Dipeptidyl Peptidase IV (DPPIV) family are exopeptidases that cleave dipeptides off the N-termini of their substrate peptides, typically after proline or alanine. Recently, we showed that human DPP4 and Caenorhabditis elegans DPF-3 have a larger target repertoire in vitro, permitting cleavage after additional amino acids. Here, we use terminal amine isotopic labeling of substrates (TAILS) to identify DPF-3 targets in vivo and observe cleavage of MEP-1 after threonine, confirming a broader substrate specificity of DPF-3 also in vivo. Demonstrating physiological relevance, we show that rendering MEP-1 resistant to cleavage disrupts its stability, leading to developmental abnormalities such as defective gonadal migration and reproductive issues. Collectively, our findings highlight a previously unappreciated complexity in the substrate specificity of DPPIV family proteases and suggest that their physiological roles may extend beyond what is currently known.
Histone post-translational modifications (PTMs) alter chromatin dynamics and contribute to the regulation of gene expression in health and disease, yet mass spectrometry-based histone PTM analysis remains constrained by inefficient sample preparation workflows. Here, we develop RIPUP (Rapid Identification of histone PTMs in Underivatized Peptides), a streamlined multiprotease workflow that reduces sample preparation to hours while improving PTM coverage and quantitative accuracy. Systematic evaluation of Arg-C Ultra and a recombinant (r)-Chymotrypsin protease under varied conditions, including standard derivatization with propionic anhydride and tandem mass tag (TMT) labeling, demonstrated that Arg-C Ultra with TMT labeling achieves a detection of total PTM that exceeds Trypsin-based approaches. Using the HiP-Frag computational framework for unrestrictive PTM identification, we discovered that TMT's tertiary amine provides charge compensation that rescues the ionization of negatively charged acylations revealing 58 succinylation and 31 glutarylation sites─a "dark epigenome" largely undetected by propionylation-based methods. Complementary digestion with Arg-C Ultra and r-Chymotrypsin provides orthogonal sequence coverage, enabling the detection of PTMs in H2A variants, linker histones, and regions poorly represented by arginine-specific cleavage alone. In HEK293T cells treated with the pan-sirtuin inhibitor nicotinamide, RIPUP quantified 112 statistically significant peptidoforms (adj p < 0.05), predominantly increasing with the NAM dose (88 up, 24 down). Application of RIPUP to frozen-thawed rat hippocampal sections within a 3 h workflow identified >200 PTMs including H3 K27/K36/K37 methylation, H4 N-terminal acetylation patterns, and H2A K118/K119 ubiquitination. This rapid, high-efficiency platform enables timely discovery of epigenetic mechanisms and accelerates the path from PTM identification to therapeutic target validation.
The unfolded protein response (UPR) is a critical adaptive program triggered upon cellular stresses that profoundly reshapes the transcriptome and translatome. In the very first minutes of cellular stress, translation blockage, RNA decay and RNA granules formation prompt the synthesis of proteins essential to the stress response. Due to the dynamic nature of these processes, investigating translation upon stress has proven to be challenging; therefore, our understanding of these mechanisms and translatome rewiring upon stress remains limited. Here, we exploit O-Propargyl-puromycin (OPP) labelling of de novo peptides followed by LC-MS/MS to identify de novo proteins translated upon endoplasmic reticulum (ER) stress. Combined with transcriptomic analyses, our approach reveals that ER stress profoundly impacts the synthesis of core splicing factor proteins leading to a significant reshaping of the splicing landscape. We identify a signature of seven splicing events consistently occurring in mammalian cells exposed to ER stress. Using pharmacological, genetic, phosphoproteomic and sequencing approaches, we demonstrate that this specific signature is driven by PERK activation and is dependent on the axis CLK1/SRSF1. Our findings identify PERK/CLK1/SRSF1 -mediated splicing regulation as a new facet of ER stress, defining an ERi-splice signature spanning healthy and malignant tissues.
Antimicrobial peptides (AMPs) play important roles in suppressing bacterial colonization and infection, and several AMPs are used as antimicrobial agents. Conversely, bacteria possess mechanisms that confer resistance to AMPs. We previously identified clinical Staphylococcus aureus isolates lacking the vraDEH genes, which are involved in nisin and bacitracin resistance. All such isolates belonged to clonal complex (CC) 121 and exhibited increased susceptibility to nisin A and bacitracin. The absence of vraDEH was accompanied by the absence of a 35,005-bp genomic region encompassing the biofilm-associated icaRADBC genes and a histidine biosynthesis operon. In a vraDEH-positive CC121 strain, this region was flanked by two IS1181 elements, whereas in vraDEH-negative strains it was replaced by a single IS1181 element, suggesting deletion through recombination between IS elements. Analysis of publicly available genomes revealed that all strains carrying the 35-kb deletion belonged to a single phylogenetic subclade of CC121. The downstream IS1181 insertion was frequently found in CC121 strains, whereas the upstream insertion was only found in this subclade. Across the S. aureus population, IS1181 copy number and insertion sites correlated with phylogenetic relationships, suggesting that lineage-associated IS1181 insertion may contribute to the genomic deletion in S. aureus CC121.
Solar salterns are environmentally stable yet biologically extreme ecosystems that serve as vital models for understanding and managing hypersaline environments, including industrial saline effluents. Despite their ecological and biotechnological significance, Indian solar salterns remain functionally underexplored. In this study, we integrated culture-dependent isolation with whole-metagenome sequencing to investigate microbial community assembly, functional specialization, and eco-technological potential across four geographically distinct Indian salterns.Physicochemical analyses revealed pronounced spatial variation in salinity, pH, and electrical conductivity, which together strongly structured microbial communities. Metagenomic sequencing generated between 4.84 and 8.68 Gb of raw data across individual site, yielding between 429,420 and 669,991 predicted genes in high-salinity locations. Taxonomic reconstruction demonstrated archaeal dominance at extreme salinity, particularly among Euryarchaeota, whereas comparatively moderate salinity sites supported more balanced bacterial-archaeal assemblages. Alpha diversity patterns indicated higher richness in Tamil Nadu and Rajasthan, while Gujarat exhibited reduced evenness consistent with environmental filtering.Culture-dependent approaches recovered 42 halophilic and polyextremophilic isolates, primarily affiliated with Halobacteriaceae and Bacillaceae, complementing the broad taxonomic detection of these lineages inferred from metagenomic data. Functional annotation revealed extensive enrichment of genes involved in ion transport, energy production, osmoprotectant biosynthesis, and DNA repair, reflecting an adaptive mechanism critical for survival in high-salinity industrial processes. Amino acid metabolism genes exceeded 25,000 hits in selected sites, and replication and repair genes reached 32,554 in Gujarat, indicating heightened stress-response activity. Secondary metabolite biosynthetic gene clusters, including pathways for novel antimicrobial peptides, terpene, ribosomally synthesized and post-translationally modified peptide-like, and type III polyketide synthase pathways, were widely distributed, offering new biological control mechanisms for environments impaired by stress. Antimicrobial resistance signatures were limited and unevenly distributed across sites.These findings demonstrate that salinity acts as a dominant ecological filter driving both taxonomic composition and functional specialization in Indian solar salterns. By linking environmental gradients to adaptive genomic traits, this study establishes a functional baseline for hypersaline ecosystems.
Diabetic wound management is compromised by infection, oxidative stress, and viscous exudates that dilute therapeutic agents. We report a spatially organized bilayer polyurethane scaffold designed to address these barriers. The scaffold integrates: (i) a hydrophilic layer with covalently bound L-arginine and ascorbic acid for degradation-dependent nitric oxide generation and ROS scavenging; (ii) a hydrophobic layer presenting REDV peptides for endothelial recruitment; and (iii) aligned microchannels with engineered wettability gradients enabling directional transport of viscous exudates (up to 90 mPa·s). This architectural segregation prevents therapeutic dilution while promoting regeneration. In diabetic infected wounds, the scaffold achieved 91.7% closure by day 12, significantly outperforming controls (43.8%) and commercial Tegaderm (56.7%). Treatment facilitated bacterial clearance, inflammatory resolution (reduced TNF-α/IL-1β, elevated IL-10), growth factor upregulation, and robust vessel maturation. These findings demonstrate that orchestrating degradation-dependent therapeutic release with directional fluid transport offers a potent translational strategy for chronic wound treatment.
Adropin, a peptide hormone encoded by the Energy Homeostasis Associated (Enho) gene, is involved in regulating food intake, energy homeostasis, and diverse metabolic functions; it is predominantly produced in the liver and brain and exerts its effects on both central and peripheral tissues. This study aimed to evaluate the impact of intracerebroventricular (ICV) adropin administration on food intake and its interactions with NPY and melanocortin systems. This research encompassed 6 experiments organized into 4 distinct groups. In experiment 1, chickens received ICV injections of saline or adropin (0.5, 1, and 2 µg). In experiment 2, birds received ICV injection of saline, B5063 (NPY1 receptor antagonist, 1.25 µg), adropin (2 µg) and co-injection of the B5063 + adropin. Experiments 3 to 6 mirrored the methodology of experiment 2, with the sole modifications being the substitution of B5063 with SF22 (NPY2 receptor antagonist, 1.25 µg), SML0891 (NPY5 receptor antagonist, 1.25 µg), SHU9119 (MC3/MC4 receptor antagonist, 0.5 nmol) and MCL0020 (MC4 receptor antagonist, 0.5 nmol). At 30, 60, and 120 min subsequent to ICV injection, cumulative food intake was evaluated. Adropin produced a significant reduction in food intake in a dose-responsive manner compared with control animals (p < 0.05). Co-injection of B5063 alongside adropin intensified the hypophagic response elicited by adropin (p < 0.05). Furthermore, the anorexigenic response triggered by adropin was negated when SHU9119 and MCL0020 were given alongside it (p < 0.05). Adropin-mediated suppression of feeding was unaffected by the administration of SF22 and SML0891 (p > 0.05). These findings suggest that the NPY1, MC3, and MC4 receptors contribute to the hypophagic response triggered by adropin.
Hormonal dysregulation is increasingly reported in ME/CFS and Long COVID, yet the broader role of neuroendocrine disruption in these conditions remains underexplored. While changes in steroid, peptide, and neuropeptide hormones have been identified, these findings are often considered in isolation and without attention to their timing or integration within broader physiological systems. The hypothalamic-pituitary axes regulate endocrine, immune, autonomic, nervous, and metabolic functions, systems commonly affected in both conditions, yet their circadian and menstrual dynamics are rarely investigated. In this review, we examine the evidence for neuroendocrine dysfunction in ME/CFS and Long COVID, focusing on hormone output, functional assays, receptor expression, and the coordination of endocrine biorhythms. Sex hormone signalling emerges as a key area of vulnerability, particularly given the female predominance in both conditions and the complexity of reproductive hormone regulation. We argue that accurate hormone measurement and time-structured sampling, including circadian and menstrual rhythms, are essential for detecting meaningful biological differences. By embedding chronobiology-aware, dense-sampling strategies and integrating multi-omic analyses into multi-system study designs, we outline a framework for investigating dynamic endocrine mechanisms underlying symptom variability and multisystem dysfunction, which may ultimately support the development of more targeted, personalised interventions.