Cysteine induces longitudinal bone growth in mice by upregulating IGF-I

Epigenetic repression of de novo cysteine synthetases induces intra-cellular accumulation of cysteine in hepatocarcinoma by up-regulating the cystine uptake transporter xCT

BACKGROUND

The metabolic reprogramming of amino acids is critical for cancer cell growth and survival. Notably, intracellular accumulation of cysteine is often observed in various cancers, suggesting its potential role in alleviating the oxidative stress associated with rapid proliferation. The liver is the primary organ for cysteine biosynthesis, but much remains unknown about the metabolic alterations of cysteine and their mechanisms in hepatocellular carcinoma cells.

METHODS

RNA-seq data from patients with hepatocarcinoma were analyzed using the TNMplot database. The underlying mechanism of the oncogenic alteration of cysteine metabolism was studied in mice implanted with BNL 1ME A.7 R.1 hepatocarcinoma.

RESULTS

Database analysis of patients with hepatocellular carcinoma revealed that the expression of enzymes involved in de novo cysteine synthesis was down-regulated accompanying with increased expression of the cystine uptake transporter xCT. Similar alterations in gene expression have also been observed in a syngeneic mouse model of hepatocarcinoma. The enhanced expression of DNA methyltransferase in murine hepatocarcinoma cells caused methylation of the upstream regions of cysteine synthesis genes, thereby repressing their expression. Conversely, suppression of de novo cysteine synthesis in healthy liver cells induced xCT expression by up-regulating the oxidative-stress response factor NRF2, indicating that reduced de novo cysteine synthesis repulsively increases cystine uptake via enhanced xCT expression, leading to intracellular cysteine accumulation. Furthermore, the pharmacological inhibition of xCT activity decreased intracellular cysteine levels and suppressed hepatocarcinoma tumor growth in mice.

CONCLUSIONS

Our findings indicate an underlying mechanism of the oncogenic alteration of cysteine metabolism in hepatocarcinoma and highlight the efficacy of alteration of cysteine metabolism as a viable therapeutic target in cancer.

Injectable hydrogel loaded with bilayer microspheres to inhibit angiogenesis and promote cartilage regeneration for repairing growth plate injury

Introduction: The repair and regeneration of growth plate injuries using tissue engineering techniques remains a challenge due to large bone bridge formation and low chondrogenic efficiency. Methods: In this study, a bilayer drug-loaded microspheres was developed that contains the vascular endothelial growth factor (VEGF) inhibitor, Bevacizumab, on the outer layer and insulin-like growth factor-1 (IGF-1), a cartilage repair factor, on the inner layer. The microspheres were then combined with bone marrow mesenchymal stem cells (BMSCs) in the gelatin methacryloyl (GelMA) hydrogel to create a composite hydrogel with good injectability and biocompatibility. Results: The in vitro drug-release profile of bilayer microspheres showed a sequential release, with Bevacizumab released first followed by IGF-1. And this hydrogel simultaneously inhibited angiogenesis and promoted cartilage regeneration. Finally, in vivo studies indicated that the composite hydrogel reduced bone bridge formation and improved cartilage regeneration in the rabbit model of proximal tibial growth plate injury. Conclusion: This bilayer microsphere-based composite hydrogel with sequential controlled release of Bevacizumab and IGF-1 has promising potential for growth plate injury repair.

Scaffolds of bioactive glass (Bioglass®) combined with recombinant human bone morphogenetic protein -9 (rhBMP-9) for tooth extraction site preservation

Objective

The study aimed to investigate the osteogenic ability of bioactive glass (bioglass) combined with recombinant human bone morphogenetic protein-9 (rhBMP-9) on rat bone marrow mesenchymal stem cells (BMSCs) in vitro. The study also compares bone regeneration using rhBMP9 soaked with different carrier systems, including bioglass or collagen membranes (BioGide, BG) in a rat alveolar bone site preservation model in vivo.

Methods

Scanning electron microscopy was employed to analyze bioglass surface. The absorption and release potential of rhBMP9 from bioglass were researched by ELISA.

The cell viability, adhesion, proliferation, and differentiation were assessed for rhBMP9 soaked on bioglass by cck-8 kit, alkaline phosphatase (ALP) activity assay, alizarin red staining, and real-time PCR. Furthermore, prepared grafts (bioglass + BG, bioglass/rhBMP9+BG, and bioglass + BG/rhBMP9) were implanted into the maxillary right first incisor sockets of Sprague Dawley rats for 8 weeks, and new bone formation was quantified by micro-CT and histological analysis.

Results

Bioglass absorbed rhBMP9 dramatically and released it with a slow and stable speed within ten days by ELISA. When used with cck-8 kit detection, cell viability at 24 h, cell adhesion rate at 8 h, and cell proliferation at 1, 3, and 5 days were decreased in the bioglass alone group versus the control group but slightly increased with the addition of rhBMP9. Similarly, the effect of osteogenic differentiation on bioglass increased significantly when combined with rhBMP9 by upregulating the expression of ALP, mineralized matrix, and osteogenic related genes. Furthermore, both bioglass/rhBMP9+BG samples and bioglass + BG/rhBMP9 samples significantly improved several bone formation parameters compared with bioglass + BG samples. Interestingly, bioglass + BG/rhBMP9 samples demonstrated more bone regeneration in rat site preservation models.

Conclusions

Both bioglass and BG can be applied in GBR surgery as effective carriers of rhBMP9. However, BG may be more suitable than bioglass for investigating site preservation effect after tooth extraction when associated with rhBMP9 and provides a practical clinical solution to the problem of bone deficiency caused by alveolar bone atrophy.

Biological Functions of Let-7e-5p in Promoting the Differentiation of MC3T3-E1 Cells

MicroRNAs let-7c and let-7f, two members of the let-7 family, were involved in regulating osteoblast differentiation and have an important role in bone formation. Let-7e-5p, which also belonged to the let-7 family, presented in the differentiation of adipose-derived stem cells and mouse embryonic stem cells. However, the role of let-7e-5p in osteoblast differentiation was unclear. Thus, this study aimed to elucidate the function of let-7e-5p in osteoblast differentiation and its mechanism. Firstly, we found that the let-7e-5p mimic promoted osteoblast differentiation but not the proliferation of MC3T3-E1 cells by positively regulating the expression levels of osteogenic-associated genes (RUNX2, OCN, OPN, and OSX), the activity of ALP, and formation of mineralized nodules. Moreover, we ascertained that the let-7e-5p mimic downregulated the post-transcriptional expression of SOCS1 by specifically binding to the 3′ untranslated region of SOCS1 mRNA. Also, let-7e-5p-induced SOCS1 downregulation increased the protein levels of p-STAT5 and IGF-1, which were both modulated by SOCS1 molecules. Furthermore, let-7e-5p abrogated the inhibition of osteogenic differentiation mediated by SOCS1 overexpression. Therefore, these results suggested that let-7e-5p regulated the differentiation of MC3T3-E1 cells through the JAK2/STAT5 pathway to upregulate IGF-1 gene expression by inhibiting SOCS1. These findings may provide a new insight into the regulatory role of let-7e-5p in osteogenic differentiation and imply the existence of a novel mechanism underlying let-7e-5p-mediated osteogenic differentiation.

Association of Plasma Total Cysteine and Anthropometric Status in 6-30 Months Old Indian Children

High-quality protein has been associated with child growth; however, the role of the amino acid cysteine remains unclear. The aim was to measure the extent to which plasma total cysteine (tCys) concentration is associated with anthropometric status in children aged 6–30 months living in New Delhi, India. The study was a prospective cohort study including 2102 children. We calculated Z-scores for height-for-age (HAZ), weight-for-height (WHZ), or weight-for-age (WAZ) according to the WHO Child Growth Standards. We used multiple regression models to estimate the association between tCys and the anthropometric indices. A high proportion of the children were categorized as malnourished at enrolment; 41% were stunted (HAZ ≤ −2), 19% were wasted (WHZ ≤ −2) and 42% underweight (WAZ ≤ −2). Plasma total cysteine (tCys) was significantly associated with HAZ, WHZ and WAZ after adjusting for relevant confounders (p < 0.001). Low tCys (≤25th percentile) was associated with a decrease of 0.28 Z-scores for HAZ, 0.10 Z-scores for WHZ, and 0.21 Z-scores for WAZ compared to being >25th percentile. In young Indian children from low-to-middle socioeconomic neighborhoods, a low plasma total cysteine concentration was associated with an increased risk of poor anthropometric status.

Association of Maternal Plasma Total Cysteine and Growth among Infants in Nepal: A Cohort Study

Cysteine is a semi-essential amino acid that has been positively associated with growth in children. However, transgenerational effects remain unclear. The aim of this analysis was to assess whether maternal plasma total cysteine (tCys) concentration is associated with various growth indicators in infants living in peri-urban settings in Bhaktapur, Nepal. We used data from the 561 mothers enrolled in an ongoing randomized controlled trial. We built linear regression models to evaluate the associations between maternal tCys and birth weight, length-for-age Z-scores (LAZ) and weight-for-length Z-scores (WLZ) at birth and six months of age. Maternal tCys was inversely associated with birth weight among boys after adjusting for confounders (p < 0.05). In addition, there was a negative association between maternal tCys and LAZ at birth (p < 0.01). No associations between maternal tCys and the other anthropometric indicators were found significant, although there was a tendency for maternal tCys to be associated positively with WLZ at birth among girls (p < 0.10). This is a first study evaluating transgenerational relation of tCys on growth in infants. Further, larger and more comprehensive studies are needed to determine if and how maternal tCys alters child growth.

Effects of Linalyl Acetate on Thymic Stromal Lymphopoietin Production in Mast Cells

Thymic stromal lymphopoietin (TSLP) is an important factor responsible for the pathogenesis of allergic diseases, such as atopic dermatitis and asthma. Because linalyl acetate (LA) possesses a wide range of pharmacological properties, being antispasmodic, anti-inflammatory, and anti-hyperpigmentation, we hypothesized that LA could inhibit TSLP. Therefore, enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, caspase-1 assay, Western blot analysis, fluorescent analyses of the intracellular calcium levels, and the phorbol myristate acetate (PMA)-induced edema model were used to investigate how LA inhibits the production of TSLP in HMC-1 cells. LA reduced the production and mRNA expression of TSLP in HMC-1 cells. LA also inhibited the activation of nuclear factor-κB and degradation of IκBα. PMA plus A23187 stimulation up-regulated caspase-1 activity in HMC-1 cells; however, this up-regulated caspase-1 activity was down-regulated by LA. Finally, LA decreased intracellular calcium levels in HMC-1 cells as well as PMA-induced ear swelling responses in mice. Taken together, these results suggest that LA would be beneficial to treatment of atopic and inflammatory diseases by reducing TSLP.

Glucagon and/or IGF-1 Production Regulates Resetting of the Liver Circadian Clock in Response to a Protein or Amino Acid-only Diet

The circadian system controls the behavior and multiple physiological functions. In mammals, the suprachiasmatic nucleus (SCN) acts as the master pacemaker and regulates the circadian clocks of peripheral tissues. The SCN receives information regarding the light-dark cycle and is thus synchronized to the external 24-hour environment. In contrast, peripheral clocks, such as the liver clock, receive information from the SCN and other factors; in particular, food intake which leads to insulin secretion induces strong entrainment of the liver clock. On the other hand, the liver clock of insulin-depleted mice treated with streptozotocin (STZ) has been shown to be entrained by scheduled feeding, suggesting that insulin is not necessary for entrainment of the liver clock by feeding. In this study, we aimed to elucidate additional mechanism on entraining liver clock by feeding a protein-only diet and/or amino-acid administration which does not increase insulin levels. We demonstrated that protein-only diet and cysteine administration elicit entrainment of the liver clock via glucagon secretion and/or insulin-like growth factors (IGF-1) production. Our findings suggest that glucagon and/or IGF-1 production are additional key factors in food-induced entrainment.

•

Dietary protein or cysteine increase serum glucagon and hepatic IGF-1 levels, and entrain liver circadian rhythm.

•

Increasing IGF-1 levels is an additional entrainment factor of liver circadian rhythm.

•

Hepatic IGF-1 production is found to be a key factor in the entrainment of liver circadian rhythm in STZ-treated mice.

Disruption of the circadian rhythm leads to multiple disorders; thus the maintenance of circadian oscillation is necessary for maintaining normalized physiological functions. Postprandial insulin secretion is known as an entraining factor of peripheral circadian rhythm; however, this pathway is not appropriate for diabetes patients in whom insulin signaling is disrupted. Here we report that both dietary protein and cysteine alone entrain liver circadian rhythm by increasing glucagon and/or IGF-1 levels independently of insulin. Findings indicate an additional entrainment factor that can be applied to chronotherapy by controlling food content or by supplementation in peoples with diabetes, circadian rhythm disorders.

The Dipeptide Pro-Gly Promotes IGF-1 Expression and Secretion in HepG2 and Female Mice via PepT1-JAK2/STAT5 Pathway

It has been shown that IGF-1 secretion is influenced by dietary protein or amino acid. However, whether the dipeptides elicit regulatory effects on IGF-1 secretion remains largely unclear. Thus, this study aimed to investigate the effects of the dipeptide Pro-Gly on IGF-1 expression and secretion in HepG2 cells and mice, and explore the underlying mechanisms. The in vitro results indicated that Pro-Gly, but not Pro plus Gly, promoted the expression and secretion of IGF-1 in HepG2. Meanwhile, the expression of the peptide transporter 1 (PepT1) was elevated by Pro-Gly, whereas knockdown of PepT1 with siRNA eliminated the increase of IGF-1 expression induced by Pro-Gly. In addition, Pro-Gly activated JAK2/STAT5 signaling pathway in a PepT1-dependent manner. Furthermore, Pro-Gly enhanced the interaction between JAK2 and STAT5, and the translocation of phospho-STAT5 to nuclei. Moreover, inhibition of JAK2/STAT5 blocked the promotive effect of Pro-Gly on IGF-1 expression and secretion. In agreement with the in vitro results, the in vivo findings demonstrated that Pro-Gly, but not Pro plus Gly, stimulated the expression and secretion of IGF-1 and activated JAK2/STAT5 signaling pathway in the liver of mice injected with Pro-Gly or Pro+Gly acutely or chronically. Besides, acute injection of JAK2/STAT5 inhibitor abolished the elevation of IGF-1 expression and secretion induced by Pro-Gly in mice. Collectively, these findings suggested that the dipeptide Pro-Gly promoted IGF-1 expression and secretion in HepG2 cells and mice by activating JAK2/STAT5 signaling pathway through PepT1. These data provided new insights to the regulation of IGF-1 expression and secretion by the dipeptides.

Which dietary components modulate longitudinal growth?

PURPOSE OF REVIEW

Linear growth in children is sensitive to nutritional status; the growth of the human skeleton requires many different nutritional factors for energy and building blocks: proteins, lipids, carbohydrates and micronutrients. However, what are the specific nutritional factors that are required for proper growth and what is the composition that will be most beneficial is still not known.

RECENT FINDINGS

Recent findings indicate that macro and micronutrients are required as building blocks and as cofactors for important enzymes. In addition, they stimulate linear growth by acting as regulatory factors and also affect gut microbiome. Some interesting studies regarding the effect of proteins and amino acids are presented.

SUMMARY

Most studies investigated the effect of replacing a single micronutrient that was deficient; however, in real life, deficiency of one nutritional element is commonly associated with other deficiencies. Therefore, it is a reasonable clinical approach, both in developing and developed countries, to use a mixture of both macro and micronutrients to support growth. How much of each of the components and what is the best composition are still open questions that require more research.

The dipeptide Pro-Asp promotes IGF-1 secretion and expression in hepatocytes by enhancing JAK2/STAT5 signaling pathway

It has been implicated that IGF-1 secretion can be regulated by dietary protein. However, whether the dipeptides, one of digested products of dietary protein, have influence on IGF-1 secretion remain largely unknown. Our study aimed to investigate the effects of the dipeptide Pro-Asp on IGF-1 secretion and expression in hepatocytes and to explore the possible underlying mechanisms. Our findings demonstrated that Pro-Asp promoted the secretion and gene expression of IGF-1 in HepG2 cells and primary porcine hepatocytes. Meanwhile, Pro-Asp activated the ERK and Akt signaling pathways, downstream of IGF-1. In addition, Pro-Asp enhanced GH-mediated JAK2/STAT5 signaling pathway, while inhibition of JAK2/STAT5 blocked the promotive effect of Pro-Asp on IGF-1 secretion and expression. Moreover, acute injection of Pro-Asp stimulated IGF-1 expression and activated JAK2/STAT5 signaling pathway in mice liver. Together, these results suggested that the dipeptide Pro-Asp promoted IGF-1 secretion and expression in hepatocytes by enhancing GH-mediated JAK2/STAT5 signaling pathway.