The Role of Cannabinoids in Bone Metabolism: A New Perspective for Bone Disorders

Shared genetic architecture highlights the bidirectional association between major depressive disorder and fracture risk

Background

There is limited evidence suggesting that osteoporosis might exacerbate depressive symptoms, while more studies demonstrate that depression negatively affects bone density and increases fracture risk.

Aims

To explore the relationship between major depressive disorder (MDD) and fracture risk.

Methods

We conducted a nested case-control analysis (32 670 patients with fracture and 397 017 individuals without fracture) and a matched cohort analysis (16 496 patients with MDD and 435 492 individuals without MDD) in the same prospective UK Biobank data set. Further, we investigated the shared genetic architecture between MDD and fracture with linkage disequilibrium score regression and the MiXeR statistical tools. We used the conditional/conjunctional false discovery rate approach to identify the specific shared loci. We calculated the weighted genetic risk score for individuals in the UK Biobank and logistic regression was used to confirm the association observed in the prospective study.

Results

We found that MDD was associated with a 14% increase in fracture risk (hazard ratio (HR) 1.14, 95% CI 1.14 to 1.15, p<0.001) in the nested case-control analysis, while fracture was associated with a 72% increase in MDD risk (HR 1.72, 95% CI 1.64 to 1.79, p<0.001) in the matched cohort analysis, suggesting a longitudinal and bidirectional relationship. Further, genetic summary data suggested a genetic overlap between MDD and fracture. Specifically, we identified four shared genomic loci, with the top signal (rs7554101) near SGIP1. The protein encoded by SGIP1 is involved in cannabinoid receptor type 1 signalling. We found that genetically predicted MDD was associated with a higher risk of fracture and vice versa. In addition, we found that the higher expression level of SGIP1 in the spinal cord and muscle was associated with an increased risk of fracture and MDD.

Conclusions

The genetic pleiotropy between MDD and fracture highlights the bidirectional association observed in the epidemiological analysis. The shared genetic components (such as SGIP1) between the diseases suggest that modulating the endocannabinoid system could be a potential therapeutic strategy for both MDD and bone loss.

Lipids and lipid signaling molecules in human milk and infant formula, a chemical characterization of relevant biochemical components

Breastfeeding is the gold standard in infant nutrition and continuous researches aim to optimize infant formula composition as the best alternative available. Human milk lipid content provides more than 50% of energy requirements for infants together with essential vitamins, polyunsaturated fatty acids, and other bioactive components. While fatty acids and vitamins human milk content has been extensively studied and, when needed those have been added to infant formulas, less is known about polyunsaturated fatty acids functional derivatives and other bioactive components. Here we describe the comparison of lipid compositions in breast milk from 22 healthy volunteers breastfeeding mothers and the six most common infant formula devoting particular attention to two families of signaling lipids, endocannabinoids, and eicosanoids. The main differences between breast milk and formulas lie in a variety of saturated fatty and unsaturated fatty acids, in the total amount (45-95% less in infant formula) and a variety of endocannabinoids and eicosanoids (2-AG, 5(s)HETE, 15(S)-HETE and 14,15-EET).

CB2 regulates oxidative stress and osteoclastogenesis through NOX1-dependent signaling pathway in titanium particle-induced osteolysis

Periprosthetic osteolysis (PPO) induced by wear particles at the interface between the prosthesis and bone is a crucial issue of periprosthetic bone loss and implant failure. After wear and tear, granular material accumulates around the joint prosthesis, causing a chronic inflammatory response, progressive osteoclast activation and eventual loosening of the prosthesis. Although many studies have been conducted to address bone loss after joint replacement surgeries, they have not fully addressed these issues. Focusing on osteoclast activation induced by particles has important theoretical implications. Cannabinoid type II receptor (CB2) is a seven-transmembrane receptor that is predominantly distributed in the human immune system and has been revealed to be highly expressed in bone-associated cells. Previous studies have shown that modulation of CB2 has a positive effect on bone metabolism. However, the exact mechanism has not yet been elucidated. In our experiments, we found that NOX1-mediated ROS accumulation was involved in titanium particle-stimulated osteoclast differentiation. Furthermore, we confirmed that CB2 blockade alleviated titanium particle-stimulated osteoclast activation by inhibiting the NOX1-mediated oxidative stress pathway. In animal experiments, downregulation of CB2 alleviated the occurrence of titanium particle-induced cranial osteolysis by inhibiting osteoclasts and scavenging intracellular ROS. Collectively, our results suggest that CB2 blockade may be an attractive and promising therapeutic scheme for particle-stimulated osteoclast differentiation and preventing PPO.

Correlation analysis of positron emission tomography/computed tomography-magnetic resonance imaging of cannabinoid type 1 receptor in the lumbar spine and brain of aged osteoporosis female cynomolgus monkeys

Background

Although cannabinoid receptor 1 (CB1R) antagonists can inhibit bone loss in osteoporosis mouse models, different strains of mice show different bone mass phenotypes after knock out the CB1R gene. The relationship between CB1R and bone metabolism is complex, and its regulatory role in bone metabolism and as a therapeutic target for osteoporosis requires further investigation.

Methods

Based on lumbar spine volumetric bone mineral density (vBMD) data of healthy female cynomolgus monkeys aged 1-25 years, naturally aged postmenopausal female osteoporotic monkeys and normal young monkeys were screened by detecting lumbar vertebrae vBMD and estradiol levels in this study. Positron emission tomography-computed tomography (PET/CT) and magnetic resonance imaging (MRI) scans were performed on the lumbar spine and brain of the two groups of monkeys using the probe [11C]OMAR, which specifically targets CB1R, and the difference in the CB1R expression of osteoporotic monkeys was evaluated.

Results

The vBMD values of two standard deviations (SDs) below the peak bone value (428.1±53.8 g/cm3) were set as the reference standard for osteoporosis vBMD. Of the 49 healthy female cynomolgus monkeys, 4 postmenopausal older osteoporotic monkeys (18-26 years) and 5 young control monkeys (6-7 years) were selected, and the mean vBMD of the lumbar spine of the two groups was 295.07±19.11 and 419.72±16.14 g/cm3, respectively (P<0.0001). Radioactive uptake in the lumbar spine was linearly and negatively correlated with vBMD (r=-0.7977; P=0.01). Dynamic PET/MR imaging of the brains showed that CB1R was upregulated in the osteoporosis group, and there was a negative linear correlation between the vBMD and area under the time-radioactivity curve (AUC) of the thalamus (r=-0.8506; P=0.0153) and prefrontal cortex (r=-0.8306; P=0.0207).

Conclusions

In this study, PET/CT-MRI molecular imaging technology revealed that CB1R was upregulated in the lumbar spine and brain of the osteoporosis monkeys and that CB1R may be regulated by the brain-bone axis. CB1R antagonist may be a potential drug for the treatment of osteoporosis.

Interoceptive regulation of skeletal tissue homeostasis and repair

Recent studies have determined that the nervous system can sense and respond to signals from skeletal tissue, a process known as skeletal interoception, which is crucial for maintaining bone homeostasis. The hypothalamus, located in the central nervous system (CNS), plays a key role in processing interoceptive signals and regulating bone homeostasis through the autonomic nervous system, neuropeptide release, and neuroendocrine mechanisms. These mechanisms control the differentiation of mesenchymal stem cells into osteoblasts (OBs), the activation of osteoclasts (OCs), and the functional activities of bone cells. Sensory nerves extensively innervate skeletal tissues, facilitating the transmission of interoceptive signals to the CNS. This review provides a comprehensive overview of current research on the generation and coordination of skeletal interoceptive signals by the CNS to maintain bone homeostasis and their potential role in pathological conditions. The findings expand our understanding of intersystem communication in bone biology and may have implications for developing novel therapeutic strategies for bone diseases.

Modulatory Effect of Gut Microbiota on the Gut-Brain, Gut-Bone Axes, and the Impact of Cannabinoids

The gut microbiome is a collection of microorganisms and parasites in the gastrointestinal tract. Many factors can affect this community's composition, such as age, sex, diet, medications, and environmental triggers. The relationship between the human host and the gut microbiota is crucial for the organism's survival and development, whereas the disruption of this relationship can lead to various inflammatory diseases. Cannabidiol (CBD) and tetrahydrocannabinol (THC) are used to treat muscle spasticity associated with multiple sclerosis. It is now clear that these compounds also benefit patients with neuroinflammation. CBD and THC are used in the treatment of inflammation. The gut is a significant source of nutrients, including vitamins B and K, which are gut microbiota products. While these vitamins play a crucial role in brain and bone development and function, the influence of gut microbiota on the gut-brain and gut-bone axes extends further and continues to receive increasing scientific scrutiny. The gut microbiota has been demonstrated to be vital for optimal brain functions and stress suppression. Additionally, several studies have revealed the role of gut microbiota in developing and maintaining skeletal integrity and bone mineral density. It can also influence the development and maintenance of bone matrix. The presence of the gut microbiota can influence the actions of specific T regulatory cells, which can lead to the development of bone formation and proliferation. In addition, its metabolites can prevent bone loss. The gut microbiota can help maintain the bone's equilibrium and prevent the development of metabolic diseases, such as osteoporosis. In this review, the dual functions gut microbiota plays in regulating the gut-bone axis and gut-brain axis and the impact of CBD on these roles are discussed.

Cannabidiol improves thyroid function via modulating vitamin D3 receptor in vitamin D3 deficiency diet-induced rat model

The study was evaluated the impact of cannabidiol (CBD) on thyroid hormones by modulation cannabinoid receptor-2 (CB2) and vitamin D receptor (VDR) in rats fed with vitamin D3 deficiency diet (VDD). CB2-receptors were analyzed by RT-PCR method and others biomarkers by ELISA. The relative expression of CB2 (thyroid ~ 4 folds), VDR protein (liver, 151.72%), and (kidney, 66%) was significantly increased in CBD-60 compared to VDD. Vitamin D3 metabolites were significantly increased serum (189.42%), kidney (73.84%), and liver (58.11%) in CBD-60 than VDD. Increased thyroxine (59.9%) and calcitonin (213.59%); while decreased thyroid-stimulating hormone (36.15%) and parathyroid hormone (38.64%) was observed CBD treatment in VDD rats. In conclusion, CBD treatment improves CB2 and VDR expression and the level of vitamin D3 metabolites, along with improved thyroid hormones, including calcitonin. This is the first report with an improved CB2 and VDR expression after CBD treatment in VDD induced animals. Thus, CBD can be considered to use in hypothyroidism conditions and to maintain bone health.