Growth hormone receptor disrupts glucose homeostasis via promoting and stabilizing retinol binding protein 4

Combined Effects of Ketogenic Diet and Aerobic Exercise on Skeletal Muscle Fiber Remodeling and Metabolic Adaptation in Simulated Microgravity Mice

Objective: Prolonged microgravity environments impair skeletal muscle homeostasis by triggering fiber-type transitions and metabolic dysregulation. Although exercise and nutritional interventions may alleviate disuse atrophy, their synergistic effects under microgravity conditions remain poorly characterized. This study investigated the effects of an 8-week ketogenic diet combined with aerobic exercise in hindlimb-unloaded mice on muscle fiber remodeling and metabolic adaptation. Methods: Seven-week-old male C57BL/6J mice were randomly divided into six groups: normal diet control (NC), normal diet with hindlimb unloading (NH), normal diet with hindlimb unloading and exercise (NHE), ketogenic diet control (KC), ketogenic diet with hindlimb unloading (KH), and ketogenic diet with hindlimb unloading and exercise (KHE). During the last two weeks of intervention, hindlimb unloading was applied to simulate microgravity. Aerobic exercise groups performed moderate-intensity treadmill running (12 m/min, 60 min/day, and 6 days/week) for 8 weeks. Body weight, blood ketone, and glucose levels were measured weekly. Post-intervention assessments included the respiratory exchange ratio (RER), exhaustive exercise performance tests, and biochemical analyses of blood metabolic parameters. The skeletal muscle fiber-type composition was evaluated via immunofluorescence staining, lipid deposition was assessed using Oil Red O staining, glycogen content was analyzed by Periodic Acid-Schiff (PAS) staining, and gene expression was quantified using quantitative real-time PCR (RT-qPCR). Results: Hindlimb unloading significantly decreased body weight, induced muscle atrophy, and reduced exercise endurance in mice. However, the combination of KD and aerobic exercise significantly attenuated these adverse effects, as evidenced by increased proportions of oxidative muscle fibers (MyHC-I) and decreased proportions of glycolytic fibers (MyHC-IIb). Additionally, this combined intervention upregulated the expression of lipid metabolism-associated genes, including CPT-1b, HADH, PGC-1α, and FGF21, enhancing lipid metabolism and ketone utilization. These metabolic adaptations corresponded with improved exercise performance, demonstrated by the increased time to exhaustion in the KHE group compared to other hindlimb unloading groups. Conclusions: The combination of a ketogenic diet and aerobic exercise effectively ameliorates simulated microgravity-induced skeletal muscle atrophy and endurance impairment, primarily by promoting a fiber-type transition from MyHC-IIb to MyHC-I and enhancing lipid metabolism gene expression (CPT-1b, HADH, and PGC-1α). These findings underscore the potential therapeutic value of combined dietary and exercise interventions for mitigating muscle atrophy under simulated microgravity conditions.

Growth hormone signaling and clinical implications: from molecular to therapeutic perspectives

Growth hormone (GH) is a key polypeptide hormone secreted by somatotroph cells in the anterior pituitary gland, essential for postnatal growth, metabolism, and systemic homeostasis. Its secretion is regulated by hypothalamic neuropeptides, including GH-releasing hormone and somatostatin. GH exerts effects through direct interaction with the growth hormone receptor and indirect pathways mediated by the GH-IGF-I axis. GHR activation triggers signaling pathways, such as JAK-STAT, PI3K/AKT, and MAPK, promoting cellular proliferation, differentiation, and metabolic balance. The GH-IGF-I axis is critical for bone growth, lipid and carbohydrate metabolism, and organ-specific physiological functions. Dysregulation of GH results in diverse disorders. Congenital deficiencies, like isolated GH deficiency and syndromic conditions (e.g., Turner syndrome), stem from genetic mutations. Acquired deficiencies arise from trauma, tumors, infections, or autoimmune damage, while GH overproduction causes gigantism in children and acromegaly in adults, often due to pituitary adenomas. Idiopathic deficiencies, lacking identifiable causes, complicate management further. Advances in therapy have transformed outcomes for GH disorders. Recombinant human growth hormone provides effective replacement therapy for deficiencies. Somatostatin analogs, dopamine receptor agonists, and GH receptor antagonists are pivotal for managing GH excess. Surgical and radiotherapeutic interventions remain essential for pituitary adenomas. However, GH therapy requires close monitoring to prevent side effects like insulin resistance and metabolic complications. This review provides a comprehensive evaluation of the molecular mechanisms underlying GH action, its physiological roles, GH-related disorders, and therapeutic approaches to optimize patient outcomes.

Cell Therapies and Gene Therapy for Diabetes: Current Progress

The epidemic of diabetes continues to be an increasing problem, and there is a need for new therapeutic strategies. There are several promising drugs and molecules in synthetic medicinal chemistry that are developing for diabetes. In addition to this approach, extensive studies with gene and cell therapies are being conducted. Gene therapy is an existing approach in treating several diseases, such as cancer, autoimmune diseases, heart disease and diabetes. Several reports have also suggested that stem cells have the differentiation capability to functional pancreatic beta cell development in vitro and in vivo, with the utility to treat diabetes and prevent the progression of diabetes-related complications. In this current review, we have focused on the different types of cell therapies and vector-based gene therapy in treating or preventing diabetes.

Proteomic Analyses in Diverse Populations Improved Risk Prediction and Identified New Drug Targets for Type 2 Diabetes

OBJECTIVE

Integrated analyses of plasma proteomics and genetic data in prospective studies can help assess the causal relevance of proteins, improve risk prediction, and discover novel protein drug targets for type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

We measured plasma levels of 2,923 proteins using Olink Explore among ∼2,000 randomly selected participants from China Kadoorie Biobank (CKB) without prior diabetes at baseline. Cox regression assessed associations of individual protein with incident T2D (n = 92 cases). Proteomic-based risk models were developed with discrimination, calibration, reclassification assessed using area under the curve (AUC), calibration plots, and net reclassification index (NRI), respectively. Two-sample Mendelian randomization (MR) analyses using cis-protein quantitative trait loci identified in a genome-wide association study of CKB and UK Biobank for specific proteins were conducted to assess their causal relevance for T2D, along with colocalization analyses to examine shared causal variants between proteins and T2D.

RESULTS

Overall, 33 proteins were significantly associated (false discovery rate <0.05) with risk of incident T2D, including IGFBP1, GHR, and amylase. The addition of these 33 proteins to a conventional risk prediction model improved AUC from 0.77 (0.73-0.82) to 0.88 (0.85-0.91) and NRI by 38%, with predicted risks well calibrated with observed risks. MR analyses provided support for the causal relevance for T2D of ENTR1, LPL, and PON3, with replication of ENTR1 and LPL in Europeans using different genetic instruments. Moreover, colocalization analyses showed strong evidence (pH4 > 0.6) of shared genetic variants of LPL and PON3 with T2D.

CONCLUSIONS

Proteomic analyses in Chinese adults identified novel associations of multiple proteins with T2D with strong genetic evidence supporting their causal relevance and potential as novel drug targets for prevention and treatment of T2D.

The Hepatokine RBP4 Links Metabolic Diseases to Articular Inflammation

OBJECTIVES

This study investigates the role of retinol binding protein 4 (RBP4) in an articular context. RBP4, a vitamin A transporter, is linked to various metabolic diseases.

METHODS

Synovial fluid RBP4 levels were assessed in crystalline arthritis (CA) patients using ELISA. RBP4's impact on articular cell types was analysed in vitro through RT-PCR and flow cytometry. Proteomic analysis was conducted on primary human osteoarthritis chondrocytes (hOACs).

RESULTS

Synovial fluid RBP4 concentrations in CA patients correlated positively with glucose levels and negatively with synovial leukocyte count and were elevated in hypertensive patients. In vitro, these RBP4 concentrations activated neutrophils, induced the expression of inflammatory factors in hOACs as well as synoviocytes, and triggered proteomic changes consistent with inflammation. Moreover, they increased catabolism and decreased anabolism, mitochondrial dysfunction, and glycolysis promotion. Both in silico and in vitro experiments suggested that RBP4 acts through TLR4.

CONCLUSIONS

This study identifies relevant RBP4 concentrations in CA patients' synovial fluids, linking them to hypertensive patients with a metabolic disruption. Evidence is provided that RBP4 acts as a DAMP at these concentrations, inducing robust inflammatory, catabolic, chemotactic, and metabolic responses in chondrocytes, synoviocytes, and neutrophils. These effects may explain RBP4-related metabolic diseases' contribution to joint destruction in various rheumatic conditions like CA.

Short-term administration of Qipian®, a mixed bacterial lysate, inhibits airway inflammation in ovalbumin-induced mouse asthma by modulating cellular, humoral and neurogenic immune responses

AIMS

Qipian® is a commercialized agent composed of extracts of three genera of commensal bacteria, and its mechanism of action on asthma is unclear. This study aimed to examine the impact of Qipian® on airway inflammation and investigate the underlying mechanisms.

MATERIALS AND METHODS

Qipian® or dexamethasone (DEX) was administered before OVA challenge in an ovalbumin-induced asthma mouse model, and then asthmatic symptoms were observed and scored. Samples of lung tissues, blood, and bronchoalveolar lavage fluid (BALF) were collected, and eosinophils (Eos), immunoglobins (Igs), and type 1 T helper (Th1)/Th2 cell cytokines were measured. Mucus production in the lung was assessed by periodic acid-Schiff (PAS) staining. The effects of Qipian® on dendritic and T regulatory (Treg) cells were investigated using flow cytometry.

KEY FINDINGS

The short-term administration of Qipian® significantly inhibited the cardinal features of allergic asthma, including an elevated asthmatic behaviour score, airway inflammation and immune response. Histological analysis of the lungs showed that Qipian® attenuated airway inflammatory cell infiltration and mucus hyperproduction. Qipian® restored Th1/Th2 imbalance by decreasing interleukin (IL)-4, IL-5, and IL-13 while increasing interferon (IFN)-γ and IL-10. Further investigation revealed that Qipian® treatment induced the upregulation of CD4+CD25+Foxp3+ Treg cells and CD103+ DCs and downregulation of tachykinins neurokinin A (NKA) and NKB in the lung.

SIGNIFICANCE

Our findings suggested that short-term treatment with Qipian® could alleviate inflammation in allergic asthma through restoring the Th1/Th2 balance by recruiting Treg cells to airways and inducing the proliferation of CD103+ DCs, which actually provides a new treatment option for asthma.

SPP2 plays a role in the tumorigenesis of hepatocellular carcinoma: A bioinformatic based analysis

OBJECTIVES

Hepatocellular carcinoma (HCC) patients at the same stage exhibit different prognosis, and the underlying molecular mechanism remains unclear. This study aims to identify the key genes impacting the prognosis of HCC patients.

METHODS

Differentially expressed gene analyses were performed between HCC samples and normal ones, and between patients with long overall survival (OS) and those with short OS, in TCGA-LIHC and GSE14520 datasets. The Kaplan-Meier method with log-rank test was used to evaluate the role of secreted phosphoprotein 2 (SPP2) in the prognosis of HCC patients. Gene set enrichment analysis (GSEA) was used to understand the difference of enriched signaling pathways between SPP2-stratified HCC subgroups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to predict the potential functional pathways in which SPP2 might participate.

RESULTS

SPP2 was significantly down-regulated in tumors when compared with normal tissues, or in tumor samples with short OS when compared with those with long OS [fold change (FC)>2 and false discovery rate (FDR)<0.05]. Low expression of SPP2 was associated with worse clinicopathological features like vascular invasion (P=1.6e-05), poor cancer status (with tumor, P=0.021), advanced T stage (T3 or T4, P=4.5e-04), advanced TNM stage (stage III or IV, P=3.1e-04), and with unfavorable prognosis (shorter OS, P=0.002). Gene enrichment analyses revealed that SPP2 might involve in the metabolic homeostasis of HCC and in the development of liver fibrosis and cirrhosis.

CONCLUSIONS

SPP2 might inhibit the development of liver fibrosis and cirrhosis and the tumorigenesis of HCC, and analogs of SPP2 might be potential drugs in the prevention of these diseases.

The Enhancement of Acylcarnitine Metabolism by 5-Heptadecylresorcinol in Brown Adipose Tissue Contributes to Improving Glucose and Lipid Levels in Aging Male Mice

5-Heptadecylresorcinol (AR-C17), a primary biomarker of whole grain (WG) consumption, has been demonstrated to improve the thermogenic activity of aging mice. However, the intricate regulatory mechanism is not fully understood. This study conducted metabolomics analysis on young and aging mice with or without AR-C17 administration after cold exposure. The results showed that the aging mice displayed lower levels of acylcarnitine (ACar) in their plasma compared with the young mice during cold exposure, and 150 mg/kg/day of AR-C17 administration for 8 weeks could increase the plasma ACar levels of aging mice. ACar has been reported to be an essential metabolic fuel for the thermogenesis of brown adipose tissue (BAT). AR-C17 had similar effects on the ACar levels in the BAT as on the plasma of the aging mice during cold exposure. Furthermore, the aging mice had reduced ACar metabolism in the BAT, and AR-C17 could improve the ACar metabolism in the BAT of aging mice, thereby promoting the metabolic utilization of ACar by BAT. Moreover, the glucose and lipid levels of aging mice could be improved by AR-C17. This study revealed a deeper metabolic mechanism involved in the AR-C17-mediated thermogenic regulation of BAT, providing a new theoretical basis for the nutrition and health benefits of WG.

Identification of Metabolism-Related Gene-Based Subgroup in Prostate Cancer

Prostate cancer is still the main male health problem in the world. The role of metabolism in the occurrence and development of prostate cancer is becoming more and more obvious, but it is not clear. Here we firstly identified a metabolism-related gene-based subgroup in prostate cancer. We used metabolism-related genes to divide prostate cancer patients from The Cancer Genome Atlas into different clinical benefit populations, which was verified in the International Cancer Genome Consortium. After that, we analyzed the metabolic and immunological mechanisms of clinical beneficiaries from the aspects of functional analysis of differentially expressed genes, gene set variation analysis, tumor purity, tumor microenvironment, copy number variations, single-nucleotide polymorphism, and tumor-specific neoantigens. We identified 56 significant genes for non-negative matrix factorization after survival-related univariate regression analysis and identified three subgroups. Patients in subgroup 2 had better overall survival, disease-free interval, progression-free interval, and disease-specific survival. Functional analysis indicated that differentially expressed genes in subgroup 2 were enriched in the xenobiotic metabolic process and regulation of cell development. Moreover, the metabolism and tumor purity of subgroup 2 were higher than those of subgroup 1 and subgroup 3, whereas the composition of immune cells of subgroup 2 was lower than that of subgroup 1 and subgroup 3. The expression of major immune genes, such as CCL2, CD274, CD276, CD4, CTLA4, CXCR4, IL1A, IL6, LAG3, TGFB1, TNFRSF4, TNFRSF9, and PDCD1LG2, in subgroup 2 was almost significantly lower than that in subgroup 1 and subgroup 3, which is consistent with the results of tumor purity analysis. Finally, we identified that subgroup 2 had lower copy number variations, single-nucleotide polymorphism, and neoantigen mutation. Our systematic study established a metabolism-related gene-based subgroup to predict outcomes of prostate cancer patients, which may contribute to individual prevention and treatment.

L-Arabinose improves hypercholesterolemia via regulating bile acid metabolism in high-fat-high-sucrose diet-fed mice

Background

Hypercholesterolemia is closely associated with an increased risk of cardiovascular diseases. l-Arabinose exhibited hypocholesterolemia properties, but underlying mechanisms have not been sufficiently investigated. This study aimed to elucidate the mechanisms of l-arabinose on hypocholesterolemia involving the enterohepatic circulation of bile acids.

Methods

Thirty six-week-old male mice were randomly divided into three groups: the control group and the high-fat-high-sucrose diet (HFHSD)-fed group were gavaged with distilled water, and the l-arabinose-treated group were fed HFHSD and received 400 mg/kg/day l-arabinose for 12 weeks. Serum and liver biochemical parameters, serum and fecal bile acid, cholesterol and bile acid metabolism-related gene and protein expressions in the liver and small intestine were analyzed.

Results

l-Arabinose supplementation significantly reduced body weight gain, lowered circulating low-density lipoprotein cholesterol (LDL-C) while increasing high-density lipoprotein cholesterol (HDL-C) levels, and efficiently alleviated hepatic inflammation and lipid accumulations in HFHSD-fed mice. l-Arabinose inhibited cholesterol synthesis via downregulation of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR). Additionally, l-arabinose might facilitate reverse cholesterol transport, evidenced by the increased mRNA expressions of low-density lipoprotein receptor (LDL-R) and scavenger receptor class B type 1 (SR-B1). Furthermore, l-arabinose modulated ileal reabsorption of bile acids mainly through downregulation of ileal bile acid-binding protein (I-BABP) and apical sodium-dependent bile acid transporter (ASBT), resulting in the promotion of hepatic synthesis of bile acids via upregulation of cholesterol-7α-hydroxylase (CYP7A1).

Conclusions

l-Arabinose supplementation exhibits hypocholesterolemic effects in HFHSD-fed mice primarily due to regulation of bile acid metabolism-related pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-022-00662-8.

In vitro efficacy of Capparis spinosa extraction against larvae viability of Echinococcus granulosus sensu stricto

Cystic echinococcosis (CE) is a chronic zoonotic parasitic disease caused by infection with the larvae of the Echinococcus granulosus sensu lato (s.l.) cluster. Currently, new drugs are urgently required due to the poor therapeutic effect of the existing drugs albendazole and mebendazole. Capparis spinosa, a traditional medicinal plant, has potential therapeutic effects on various diseases based on extracts from its fruit and other parts. The results of this study demonstrated that the water-soluble and ethanolic extracts of C. spinosa fruit had in vitro killing effects on the larvae of E. granulosus sensu stricto (s.s.) and disrupted the ultrastructure of protoscoleces and metacestodes. In vitro cytotoxicity assays showed that the water-soluble and ethanolic extracts of C. spinosa fruit were not significantly toxic to primary mouse hepatocytes at an effective dose to CE. In conclusion, water-soluble and ethanolic extracts of C. spinosa fruit have great potential for the development of new drugs for the treatment of CE.

Retinoid Homeostasis and Beyond: How Retinol Binding Protein 4 Contributes to Health and Disease

Retinol binding protein 4 (RBP4) is the specific transport protein of the lipophilic vitamin A, retinol, in blood. Circulating RBP4 originates from the liver. It is secreted by hepatocytes after it has been loaded with retinol and binding to transthyretin (TTR). TTR association prevents renal filtration due to the formation of a higher molecular weight complex. In the circulation, RBP4 binds to specific membrane receptors, thereby delivering retinol to target cells, rendering liver-secreted RBP4 the major mechanism to distribute hepatic vitamin A stores to extrahepatic tissues. In particular, binding of RBP4 to 'stimulated by retinoic acid 6' (STRA6) is required to balance tissue retinoid responses in a highly homeostatic manner. Consequently, defects/mutations in RBP4 can cause a variety of conditions and diseases due to dysregulated retinoid homeostasis and cover embryonic development, vision, metabolism, and cardiovascular diseases. Aside from the effects related to retinol transport, non-canonical functions of RBP4 have also been reported. In this review, we summarize the current knowledge on the regulation and function of RBP4 in health and disease derived from murine models and human mutations.

A novel regulatory mechanism of geniposide for improving glucose homeostasis mediated by circulating RBP4

BACKGROUND

Systemic insulin signal transduction is influenced by the inter-tissue crosstalk, which might be the potential therapeutic strategy for T2DM. Although anti-diabetic function of geniposide has been previously reported, the underlying mechanism was not completely clear in light of the complex pathogenesis of T2DM.

PURPOSE

The present experiment is devoted to investigate the potential effects of geniposide on systemic insulin sensitivity mediated by hepatokine-RBP4 in high fat diet (HFD)-fed mice.

METHODS

The HFD-fed wild type mice were administered with geniposide (25 or 50 mg/kg/d) by intraperitoneal injection, and the normal saline and Metformin were used as negative control group and positive control group, respectively. After administration for 4 weeks, the food intake, body weight, glucose tolerance tests, insulin tolerance tests and serum biochemical indices were examined, along with insulin signaling pathway-associated proteins and hepatic histomorphological analysis. The liver, gastrocnemius and mouse primary hepatocytes were also harvested for molecular mechanism study.

RESULTS

After geniposide treatment for 4 weeks, the blood glucose level was reduced in HFD-fed mice. Furthermore, geniposide treatment improved insulin sensitivity both in the liver and gastrocnemius (GAS). In terms of mechanism, geniposide disturbed circulating RBP4 level including its synthesis, secretion and homeostasis. Moreover, geniposide modified fuel selection and promoted glucose uptake in skeletal muscle and reduced glycogen storage, which were closely related to impaired circulating RBP4 homeostasis, leading to ameliorative systemic insulin sensitivity.

CONCLUSION

Our current study proposes a novel regulatory mechanism of geniposide for improving glucose homeostasis through regulating circulating RBP4 level, which also provides new strategies for the prevention and treatment of T2DM.

EgGLUT1 Is Crucial for the Viability of Echinococcus granulosus sensu stricto Metacestode: A New Therapeutic Target?

Cystic echinococcosis (CE) is a zoonotic parasitic disease caused by infection with the larvae of Echinococcus granulosus sensu lato (s.l.) cluster. It is urgent to identify novel drug targets and develop new drug candidates against CE. Glucose transporter 1 (GLUT1) is mainly responsible for the transmembrane transport of glucose to maintain its constant cellular availability and is a recent research hotspot as a drug target in various diseases. However, the role of GLUT1 in E. granulosus s.l. (EgGLUT1) was unknown. In this study, we cloned a conserved GLUT1 homology gene (named EgGLUT1-ss) from E. granulosus sensu stricto (s.s.) and found EgGLUT1-ss was crucial for glucose uptake and viability by the protoscoleces of E. granulosus s.s. WZB117, a GLUT1 inhibitor, inhibited glucose uptake by E. granulosus s.s. and the viability of the metacestode in vitro. In addition, WZB117 showed significant therapeutic activity in E. granulosus s.s.-infected mice: a 10 mg/kg dose of WZB117 significantly reduced the number and weight of parasite cysts (P < 0.05) as efficiently as the reference drug, albendazole. Our results demonstrate that EgGLUT1-ss is crucial for glucose uptake by the protoscoleces of E. granulosus s.s., and its inhibitor WZB117 has a therapeutic effect on CE.

Towards Understanding the Direct and Indirect Actions of Growth Hormone in Controlling Hepatocyte Carbohydrate and Lipid Metabolism

Growth hormone (GH) is critical for achieving normal structural growth. In addition, GH plays an important role in regulating metabolic function. GH acts through its GH receptor (GHR) to modulate the production and function of insulin-like growth factor 1 (IGF1) and insulin. GH, IGF1, and insulin act on multiple tissues to coordinate metabolic control in a context-specific manner. This review will specifically focus on our current understanding of the direct and indirect actions of GH to control liver (hepatocyte) carbohydrate and lipid metabolism in the context of normal fasting (sleep) and feeding (wake) cycles and in response to prolonged nutrient deprivation and excess. Caveats and challenges related to the model systems used and areas that require further investigation towards a clearer understanding of the role GH plays in metabolic health and disease are discussed.