Dysregulated blood glucose from refined-carbohydrate and high-sugar diets is rising globally, which is contributing to increasing diabetic and hyperglycemia cases. Sustained hyperglycemia shows negative effects on bone repair and endocrine hormonal balance. Affected people are showing slower healing as well as increased fracture risk. Bone mesenchymal stem cells (BMSCs) are essential for bone generation. Under high glucose levels, they lose their ability to proliferate. Their osteogenic capacity also decreases.
A recent study published in “Nature Communications” aimed to investigate how sustained hyperglycemia impairs bone regeneration by disrupting immune-metabolic interactions, particularly examining how neutrophil-derived Pad4 and its metabolite 4-guanidinobutyric acid (4-GBA) affect mesenchymal stem cell osteogenesis. This study also evaluated targeted interventions to restore bone healing in the context of hyperglycemia.
Multiple animal models like male Beagle dogs (age = 15 months, weight = 10-12kg), female Sprague-Dawley (SD) rats (age = 6-8 weeks, weight = 180-220g), female Padi4–/– mice (age = 6-8 weeks, weight = 16-20g), and male New Zealand white rabbits (age = 18-30 weeks, weight = 2.5-4kg) were used in this study. All these animals were housed on a standard diet and under controlled conditions (12-hour light/dark cycle). Experimental procedures included induction of hyperglycemia, tooth extraction, creation of mandibular defects, and treatment with GBASpongel or control solutions. Additional studies involved protein docking, molecular dynamics simulation, peptide hydrogel preparation, and characterization using biochemical assays, scanning electron microscopy (SEM), transmission electron microscopy (TEM), rheology, and isothermal titration calorimetry (ITC).
Human blood samples were collected from healthy, prediabetic, and diabetic individuals (age = 20-45 years). Multiple tooth extraction and bone defect models across various animal models were used to evaluate the GBASpongel-mediated bone regeneration process through histology, micro-computed tomography (micro-CT), oral glucose tolerance test (OGTT), and fluorescence labelling.
Hyperglycemia severely impairs jawbone regeneration. In severe hyperglycemic rats, tooth extraction defects showed an 85% drop in bone volume to total volume ratio (BV/TV), 82% lower trabecular number (Tb.N), 55% reduced bone mineral density (BMD), and 4.8 times increase in trabecular separation (Tb.Sp) at one week. Formation of new bone decreased by 79% and remained below 30% at one month. Jawbone mesenchymal stem cells (JBMSCs) demonstrated an 85% fall in CD73+/ALP+ cells and more than 60% reduction in osteogenic markers. Furthermore, >90% decrease in mineralized nodule formation. Intermittent hyperglycemia produced similar results, with milder deficits, which confirmed impaired JBMSC osteogenesis and mineralization.
Hyperglycemia activated ERK/JNK signaling pathways in neutrophils, increasing phosphorylated ERK by 91% and JNK by 80% which regulated Pad4 through c-Fos/c-Jun. This drives excessive arginine conversion to 4-GBA, inhibiting ALP activity in JBMSC and impairing osteogenesis. Pad4-knockout mice showed improved healing with 39% higher BMD and 1.2 times higher Tb. N, 62% lower Tb.Sp and 1.8-fold higher BV/TV.
GBASpongel restored jawbone regeneration under high-glucose conditions. In chronic hyperglycemic rats, it increased BMD by 95%, BV/VT by 3.3 times, Tb.N by 2.6-fold, and reduced Tb.Sp by 74% at one week, with a 3.1-fold increase in new bone formation. GBASpongel reduced the local 4-GBA-enhanced ALP+/CD73+ JBMSC and demonstrated strong osteogenic efficacy and biosafety in beagle dogs, rabbits, and rats.
This study concluded that hyperglycemia impairs jawbone regeneration by activating the ERK/JNK pathways and increasing 4-GBA accumulation, thereby inhibiting JBMSC and ALP osteogenesis. Deletion or inhibition of Pad4 restores bone healing while GBASpongel hydrogel sequesters 4-GBA, enhancing osteogenesis in beagle dogs, rats, and rabbits, offering a targeted strategy for hyperglycemia-induced bone defects.
References: Zhang L, Li J, Wei X, Yang W, He W, Liu W. Elimination of a neutrophil Pad4 byproduct restores stem cell–mediated bone regeneration in hyperglycemia. Nat Commun. 2025. doi:10.1038/s41467-025-66935-x
