Dequina A. Nicholas

Th17 cells are categorized as non-pathogenic (Th17np) and pathogenic (Th17p), states defined primarily in murine autoimmune models. In contrast, studying these states in humans remains difficult because these subsets lack validated identifiers. We developed a nanovial-based single-cell ELISA to isolate cytokine-secreting human Th17 cells and define Th17np vs Th17p cell transcriptional states. These signatures enabled predictive classification and flow-cytometric identification across tissues and diseases. Application of these strategies with single-cell metabolic modeling and functional profiling revealed that Th17np cells predominate in type 2 diabetes yet exhibit impaired fatty acid oxidation capacity despite elevated carnitine palmitoyltransferase 1A (CPT1A). CRISPR perturbation and pharmacologic inhibition identified acylcarnitine metabolism as a regulator of Th17 state balance and exposed a selective metabolic vulnerability in type 2 diabetes. This framework links human Th17 cell pathogenicity to lipid metabolism.

High-fructose corn syrup (HFCS) consumption is a risk factor for obesity and diabetes, yet the underlying mechanisms, especially at the specific organ level, are incompletely understood. Catabolism of dietary fructose primarily occurs in the small intestine and liver, with fructose breakdown in the liver being pathological, while small intestinal fructose clearance protects the liver. Here, we report that inhibition of fructose catabolism specifically in the murine small intestine unexpectedly mitigates fructose-induced obesity and insulin resistance. Such phenotypes are attributed to decreased dietary fat absorption by the shortening of ileal lacteals. Fecal transplantation experiments revealed that the microbiome altered by blunted host intestinal fructose catabolism decreases ileal macrophages essential for lacteal growth. Thus, altered intestinal lacteal architecture likely contributes to the synergistic effects of high fat and sugar on metabolic disorders. It may also be relevant to the clinical evidence that pharmacologic suppression of fructose catabolism mitigates diet-induced obesity.

Chronic inflammation disrupts hormonal balance in the Hypothalamic-Pituitary-Gonadal (HPG) axis, contributing to reproductive disorders. While immune cells in the hypothalamus and ovaries have been extensively studied, their impact on the pituitary remains largely unexplored. Our research identifies pituitary macrophages (PitMacs) as the dominant pituitary immune cell population with a role in regulating reproductive gonadotropin secretion both in vitro and in vivo. Using a targeted AAV-based depletion strategy, we demonstrate that a reduction of PitMacs decreases serum gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), in female mice. PitMacs are transcriptomically distinct from other tissue-resident macrophages and harbor a unique translational program that reflects the pituitary's endocrine identity, including active translation of growth hormone (Gh) and prolactin (Prl). Cytokine profiling identified CXCL5 and IFN-γ as key PitMac-derived mediators of gonadotropin regulation. Mechanistically, CXCL5 signals through CXCR2 to activate the MAPK pathway, converging with Gonadotropin-Releasing Hormone (GnRH) signaling in a time-dependent manner to regulate LH secretion and GnRH receptor surface expression. These findings establish PitMacs as essential endocrine-immune integrators, opening new avenues for understanding inflammation-driven reproductive disorders.

Polyendocrine metabolic ovarian syndrome (PMOS), formerly termed polycystic ovary syndrome (PCOS), is a reproductive disorder with heterogeneous symptoms and severity. Despite extensive research documenting chronic immune dysfunction as a hallmark of PMOS, the specific mechanisms of immune activation remain poorly understood. Emerging evidence suggests that gut-derived bacterial endotoxins, particularly lipopolysaccharide (LPS), can breach intestinal barriers and trigger systemic inflammation via Toll-like receptor 4 (TLR4). This study examined the role of TLR4 in PMOS-like pathology using a letrozole (LET)-induced mouse model. In LET-treated wild-type female mice, serum LPS and its carrier protein LBP were elevated compared to LET-treated TLR4-/- mice. Additionally, TLR4 deficiency attenuated multiple PMOS-like features, including elevated luteinizing hormone, anovulation, and metabolic dysfunction. LET-treated TLR4-/- mice also preserved estrous cycling and fertility, maintained gut barrier integrity, and reduced inflammatory markers. These findings support TLR4 as an important contributor to multiple features of PMOS-like pathology. This novel work highlights TLR4-mediated inflammation as a potential target for anti-inflammatory treatments in women with PMOS.

Metabolism is known to influence cell identity, but the underlying mechanisms remain unclear. Here we reveal spatiotemporal dynamics of phosphofructokinase 1 (PFK1), a key glycolytic enzyme, within the skeletal muscle lineage. The expression of PFKM (the muscle isoform of PFK1) is low in muscle stem cells and increases during differentiation. Mechanistically, Wnt signalling rapidly induces lysosomal degradation of PFKM through a methyl arginine degron motif, which gets selectively methylated by the protein arginine methyltransferase (PRMT1) and delivered to lysosomes through microautophagy. PFKM degradation shifts glucose metabolism from glycolysis to the pentose phosphate pathway. PFKM overexpression increases glycolysis and promotes differentiation into terminally differentiated myofibres. On the other hand, PFKM knockdown blunts differentiation, which can be rescued by supplementation with the downstream glycolytic intermediate 3-phosphoglycerate. In sum, our findings highlight the importance of compartmentalized metabolism in cell fate decisions.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the leading cause of dementia. It is characterized by cognitive decline and accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles. Accumulating evidence indicates that viral infection may worsen and/or increase development of established AD pathology. The COVID-19 pandemic has brought attention to the link between SARS-CoV-2 infection and neurologic conditions that vary in severity and duration, as well as the worsening of clinical symptoms in elderly people with dementia. To better understand potential mechanisms by which SARS-CoV-2 infection impacts AD neuropathology, aged 5xFAD and wildtype (WT) mice were intranasally infected with mouse-adapted SARS-CoV-2 (MA10). Intranasal infection of aged-matched (10-14 month) 5xFAD or wild type (WT) C57BL/6 mice with MA10 resulted in viral infection of the lungs that correlated with acute viral pneumonia characterized by lymphocyte inflammation and antiviral immune responses. Viral RNA was not detected within the central nervous system (CNS) of either WT or 5xFAD mice at days 7 or 21 post-infection (p.i.), nor were there signs of overt glial activation or neuroinflammation. There were no differences in either Aβ plaque volume or number within the brains of MA10-infected 5xFAD mice compared to uninfected 5xFAD mice. However, bulk RNA sequencing and spatial transcriptomics revealed evidence of altered expression of genes associated with neuronal and glial dysfunction, as well as reduced expression of genes encoding adhesion molecules in vascular endothelial cells. Collectively, these findings demonstrate that MA10 infection did not affect Aβ plaque size or numbers in 5xFAD mice, yet in both WT and 5xFAD mice, there were numerous down-stream effects on gene expression associated with resident CNS cell function.

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder affecting women worldwide. For decades, the “chronic inflammation hypothesis” has guided research into the role of the immune system in PCOS pathogenesis. However, this review challenges this paradigm by pointing out discrepancies in current literature on systemic immune markers in PCOS. We highlight the limitations of relying solely on systemic inflammatory markers and emphasize the importance and diversity of tissue-specific immune responses. Evidence from human and animal studies reveals distinct immune responses across various tissues affected by PCOS or inflammation, including the hypothalamus, pituitary, ovaries, endometrium, and adipose tissue. These findings suggest that PCOS is not characterized by systemic low-grade inflammation, but rather by discrete tissue-specific immune interaction with endocrine cells. Finally, we discuss how advanced single-cell technologies and computational tools are enhancing our understanding of immune cell signaling to endocrine cells in PCOS. Moving forward, we propose that research should focus on elucidating causal relationships between local immune responses and endocrine dysfunction in PCOS. This shift in perspective from systemic to tissue-specific immune responses is critical for developing targeted immunotherapies for PCOS.

Polycystic ovary syndrome (PCOS) is a reproductive disorder with heterogeneous symptoms and severity. Despite extensive research documenting chronic immune dysfunction as a hallmark of PCOS, the specific molecular mechanisms driving immune activation and its connection to the syndrome’s diverse symptoms remain poorly understood. Emerging evidence suggests that gut-derived bacterial endotoxins, particularly lipopolysaccharide (LPS), may breach the intestinal barriers in PCOS patients and trigger systemic inflammation through Toll-like receptor 4 (TLR4), a pattern recognition receptor of the innate immune system. This study investigated whether TLR4 serves as a critical mechanistic driver of PCOS pathogenesis by examining the effect of genetic TLR4 knockout (TLR4 ^-/- ) in a letrozole (LET)-induced mouse model of PCOS. Our results demonstrate that TLR4 deficiency reduces many PCOS-like symptoms, including elevated luteinizing hormone, anovulation, and metabolic dysfunction. TLR4 knockout also preserved estrous cycling and fertility, improved glucose tolerance, maintained gut barrier integrity, and reduced inflammatory markers in LET-treated females. These findings establish TLR4 as a key mediator orchestrating PCOS’s multi-system pathology, positioning TLR4 as a critical convergence point rather than affecting individual symptoms in isolation. This novel work reveals that TLR4-mediated inflammation drives multiple PCOS pathologies, opening avenues for targeted anti-inflammatory treatments in women with this disorder. Significance Statement: Polycystic ovary syndrome (PCOS) affects up to 15% of reproductive-age women worldwide. This study reveals that TLR4, an innate immune receptor, is key to the pathophysiology of PCOS-like symptoms in female mice. When TLR4 was genetically deleted, mice treated with letrozole to induce PCOS-like symptoms maintained normal weight, glucose regulation, estrous cycling, and fertility. The improvements coincided with preserved gut barrier breakdown and reduced inflammation. These findings identify TLR4 as a key mediator between gut health, immune activation, and PCOS pathophysiology, suggesting that targeting TLR4 could offer new therapeutic approaches for this common but poorly understood syndrome affecting millions of women.

Diabetes is a metabolic and inflammatory disease that disproportionately affects African American populations, yet clinical diagnostics often rely on biomarkers discovered and validated predominantly in White cohorts. This study investigates race-specific lipid and inflammatory features of diabetes to uncover biologically distinct disease signatures that may contribute to disparities in diagnosis and management. We analyzed clinical parameters from a well-matched subset of the HANDLS cohort (N = 40) and conducted targeted plasma lipidomics and multiplex cytokine profiling across African American and White individuals from the HANDLS cohort with and without diabetes. Then we validated key findings using a large and diverse cohort of African American and White individuals with type 2 diabetes from the NIH AllofUs program (N = 17,339). Our results reveal racially divergent signatures of diabetes. White individuals with diabetes exhibited elevated Cholesterol:HDL ratios, triglycerides, and classical inflammatory markers such as hs-CRP. In contrast, African American individuals with diabetes displayed minimal lipid elevations but showed increased Th17-related cytokines1. These differences were independent of statin use, age, and body mass index. Additionally, correlations between lipid to cytokine ratios and the glycemic marker hemoglobin A1C differed sharply by race, suggesting that the pathophysiology of diabetes is not uniform across populations. Our findings challenge standard diabetes biomarkers and emphasize the need for more inclusive diagnostic frameworks. By identifying population-specific biological patterns of diabetes, this study provides important insight into the roots of persistent health disparities and underscores the value of precision approaches to equitable diabetes care.