Metabolic control of collagen synthesis

A comparison of human skeletal muscle cell maturation in 2D versus 3D culture: A quantitative proteomic study

Compared with 2D monolayers, 3D models more closely mimic native muscle tissue and allow functional measurements. A more complete understanding of how culture conditions and duration affect myotube maturity/function is crucial for validating the transition to 3D systems. Human skeletal muscle cells were cultured as 2D monolayers or within 3D hydrogels for up to 21 days. Quantitative proteomic analysis and functional measurements were conducted to evaluate muscle cell differentiation. Myoblasts differentiated into myotubes by 8 days in both environments; however, at Day 8, 3D constructs exhibited a predominantly slow-twitch phenotype, compared with the mixed fiber type of 2D monolayers. By Day 21, 3D constructs demonstrated enhanced mitochondrial maturity, extracellular matrix remodeling, and a fast-twitch phenotype, indicated by increased myosin-2 abundance (Log2(FC)>1.29, p <0.05). Passive tension increased by >20% following prolonged culture of 3D muscle constructs, but contractile forces reduced by >40%. This study provides a comprehensive proteomic profile of human skeletal muscle cells in 2D and 3D, demonstrating that 3D culture promoted myotube maturity and highlighting the importance of selecting appropriate culture conditions. Data suggest 8 days of differentiation as ideal for achieving peak contractile force in 3D constructs, providing optimal models for testing interventions aimed at preserving muscle function.

Alterations in hepatic amino acid metabolism related to MASLD in individuals with obesity

Deregulation of amino acid (AA) metabolism has been reported in several pathological conditions, including metabolic diseases (e.g., obesity and diabetes), cardiovascular diseases, and cancer. However, the role of alterations in AA levels in chronic liver disorders such as metabolic dysfunction-associated steatotic liver disease (MASLD) remains largely unexplored. In this study we aimed to evaluate the hepatic AA composition in patients with different stages of MASLD, and their relationship with MASLD-related risk factors. A case-control study was conducted in 40 patients with obesity undergoing bariatric surgery at Virgen de la Arrixaca University Hospital (Murcia, Spain), where MASLD diagnosis was confirmed by histological analysis of liver biopsies, and hepatic AA levels were measured using ultra-performance liquid chromatography high-resolution time-of-flight mass spectrometry. Our results revealed that the hepatic AA profile was significantly altered in patients with MASLD. More specifically, comparison between MASLD patients revealed a significant increase in hepatic levels of arginine, glycine and cystine in MASH samples compared to steatotic livers. In addition, hepatic concentrations of arginine, lysine and cystine positively correlated with histopathological diagnosis and other MASLD-related parameters, including transaminases and CK-18 levels. These findings suggest that alterations in certain hepatic AA levels such as arginine, lysine, glycine and cystine in MASLD patients could have translational relevance in understanding the onset of this disease.

Beneficial impact of MTGase-modified fish gelatin on collagen supplementation in rats: Insights from serum metabolomics and gut microbiota

Sustained release technology facilitates precise regulation of active ingredient delivery, attenuating enzymatic degradation while optimizing bioavailability in malabsorptive conditions. Microbial transglutaminase (MTGase) catalyzes isopeptide bond formation via acyl transfer reactions, conferring resistance to gastrointestinal digestion. However, the in vivo sustained release potential of MTGase-modified fish gelatin (MTGase-modified-FG) remains uncertain. In this study, enzymatic modification was performed using MTGase at graded concentrations (0.00 % (Nor), 0.06 % (LD), 0.12 % (MD), and 0.21 % (HD)), with sustained release of collagen evaluated through pharmacokinetic analysis. The results indicated that the MTGase-modified-FG supplementation exhibited a dose-dependent sustained release, extending Tmax from 2.00 ± 0.00 h (Nor) to 5.33 ± 1.15 h (HD). Notably, suboptimal crosslinking (LD/MD) enhanced skin collagen deposition, whereas excessive modification (HD) induced malabsorptive phenomena that may be attributed to the presence of excessive isopeptide bonds. Metabolomic analysis identified MTGase-modified-FG modulated the serum metabolome in collagen-related metabolites (LysoPC, Lysine, succinate), mechanistically linked to choline metabolism in cancer and lysine catabolism. Additionally, the gut microbiota remodeling was modulated by the suppression of Ruminococcus and Blautia, as well as by the expansion of Faecalibaculum and Bifidobacterium at the genus level. RT-qPCR analysis indicated that MTGase-modified-FG enhanced collagen deposition via the TGF-β/Smads and MAPK/AP-1/MMP pathways in human dermal fibroblast cells. These findings suggest that MTGase-modified confers the sustained release properties to fish gelatin, and provides a new collagen supplementation strategy for individuals with malabsorption syndromes.

Vitamin C in Cardiovascular Disease: From Molecular Mechanisms to Clinical Evidence and Therapeutic Applications

Vitamin C, also known as ascorbic acid, is an essential nutrient that humans cannot synthesize, making its intake crucial for health. Discovered nearly a century ago, vitamin C is widely recognized for its ability to prevent scurvy and has become one of the most commonly used supplements. Beyond its antioxidant activity, vitamin C is pivotal in regulating lipid metabolism, promoting angiogenesis, enhancing collagen synthesis, modulating remodeling, and stabilizing the extracellular matrix. While preclinical studies have shown promising results, clinical trials have yielded inconsistent findings, due to suboptimal study design, results misinterpretation, and misleading conclusions. This review provides a holistic overview of existing evidence on the pleiotropic role of vitamin C in cardiovascular diseases, identifying both the strengths and limitations of current research and highlighting gaps in understandings in vitamin C's underlying mechanisms. By integrating molecular insights with clinical data and evaluating the pleiotropic role of vitamin C in cardiovascular disease management and prevention, this review aims to guide future research toward personalized, evidence-based therapeutic strategies in clinical practice.

Remodeling of self-assembled microvascular networks under long term flow

The incorporation of a functional perfusable microvascular network (MVN) is a common requirement for most organ on-chip-models. Long-term perfusion of MVNs is often required for the maturation of organ phenotypes and disease pathologies and to model the transport of cells and drugs entering organs. In our microphysiological system, we observe that flow can recover perfusion in regressed MVNs and maintain perfusable MVNs for at least 51 days. Throughout the 51 days, however, the MVNs are continuously remodeling to align with the direction of bulk flow and only appear to attain morphological homeostasis with the use of maintenance medium without growth factors. We observed that the flow resistance of the MVNs decreases over time, and using a computational model, we show that stable vessels have higher flow rates and velocities compared to regressing vessels. Cytokine analysis suggests that static conditions generate an inflammatory state, and that continuous flow reduces inflammation over an extended period. Finally, through bulk RNA sequencing we identify that both the endothelial and fibroblast cells are actively engaged in vascular and matrix remodeling due to flow and that these effects persist for at least 2 weeks. This MPS can be applied to study hemodynamically driven processes, such as metastatic dissemination or drug distribution, or to model long-term diseases previously not captured by MPS, such as chronic inflammation or aging-associated diseases.

The role of various collagen types in tumor biology: a review

Collagen comprises approximately 30% of the body's protein content and is essential for maintaining the structural integrity, support, and strength of the skin, muscles, bones, and connective tissues. Recent research has further elucidated its role in various aspects of tumor biology, including tumorigenesis, invasion, migration, drug resistance, and recurrence. Furthermore, collagen is involved in prognostic assessments, the evaluation of therapeutic efficacy, immunoregulation, and the identification of potential treatment targets in oncology. This review examines a range of tumor types, including lung, gastric, breast, melanoma, and colorectal cancers, among others. Our objective is to differentiate these tumors based on the specific types of collagen present and to analyze the roles of various collagen types in tumor development, progression, prognosis, and their potential as therapeutic targets.

Arginine: at the crossroads of nitrogen metabolism

L-arginine is the most nitrogen-rich amino acid, acting as a key precursor for the synthesis of nitrogen-containing metabolites and an essential intermediate in the clearance of excess nitrogen. Arginine's side chain possesses a guanidino group which has unique biochemical properties, and plays a primary role in nitrogen excretion (urea), cellular signaling (nitric oxide) and energy buffering (phosphocreatine). The post-translational modification of protein-incorporated arginine by guanidino-group methylation also contributes to epigenetic gene control. Most human cells do not synthesize sufficient arginine to meet demand and are dependent on exogenous arginine. Thus, dietary arginine plays an important role in maintaining health, particularly upon physiologic stress. How cells adapt to changes in extracellular arginine availability is unclear, mostly because nearly all tissue culture media are supplemented with supraphysiologic levels of arginine. Evidence is emerging that arginine-deficiency can influence disease progression. Here, we review new insights into the importance of arginine as a metabolite, emphasizing the central role of mitochondria in arginine synthesis/catabolism and the recent discovery that arginine can act as a signaling molecule regulating gene expression and organelle dynamics.

Lower expression of colony-stimulating factor 2, an embryokine, in the endometrial epithelium of old cows

Context Infertility increases with age in various animals, including cows, owing to unknown mechanisms. The glandular and luminal epithelia of the bovine uterus synthesise and secrete colony-stimulating factor 2 (CSF2), which is a well-studied embryokine. We recently reported the possibility of fibrosis in the uteri of old cows. However, the relationship between CSF2 expression and fibrosis has not yet been clarified. Aims We tested the hypothesis that the endometrial epithelia of old cows have lower CSF2 expression compared to in heifers, and that myofibroblasts [alpha-smooth muscle actin (αSMA)-positive fibroblasts] increase near the epithelium of old cows. Methods We collected caruncle and intercaruncle samples from post-pubertal, growing, nulliparous heifers (n =6; 24.7±1.3months old) and old multiparous cows (n =6; 128.5±15.4months old). We analysed mRNA and protein expression, along with fluorescent immunohistochemistry for CSF2, anti-collagen type IV, anti-Müllerian hormone type 2 receptor, and anti-αSMA. Key results Quantitative reverse transcription polymerase chain reaction and western blot analysis revealed lower CSF2 expression in the caruncle and intercaruncle of old cows than in young heifers. Fluorescence microscopy using the same antibodies and anti-collagen type IV, anti-Müllerian hormone type 2 receptor, and anti-αSMA antibodies showed increased fibroblasts and αSMA signals near the epithelium of old cows compared to young heifers. Conclusion CSF2 expression was lower in endometrial epithelia of old cows compared to those in heifers, and myofibroblasts increased near the epithelia of old cows. Implications Lower CSF2 may play an important role in age-related infertility.