Crosstalk within a brain-breast-bone axis regulates mineral and skeletal metabolism during lactation

Gene Variants and Bisphosphonates Treatment in Pregnancy and Lactation-Associated Osteoporosis (PLO): A Retrospective Study of 22 Chinese Patients

Pregnancy and lactation-associated osteoporosis (PLO) is a rare bone disorder with insufficient understanding on its pathogenesis and treatments. We retrospectively investigated 22 Chinese PLO patients diagnosed in our hospital. Whole exome sequencing was performed in 14 patients, and responses to bisphosphonates treatment were evaluated. The mean age of the patients was 30.8 ± 4.4 years. The mean number of vertebral fractures per patient was 4.0 ± 2.6. The bone mineral density (BMD) Z-scores were - 2.9 ± 0.9 at the lumbar spine (LS), - 1.7 ± 0.7 at the femoral neck, and - 1.8 ± 0.7 at the total hip. Trabecular bone score Z-score was - 2.2 ± 0.8. Genetic analysis identified relevant variants (RVs) in 11 of 14 patients, predominantly in LRP5, WNT1, and COL1A1/A2. Patients with RVs had significantly greater height loss (3.6 ± 2.1 cm vs. 0 cm, p = 0.028). All patients received bisphosphonate therapy, during which increases in BMD primarily at the LS were observed: 13.5 ± 8.8%, 17.8 ± 14.7%, 22.0 ± 17.0%, 27.0 ± 14.1% and 35.1 ± 18.5% at the 6-, 12-, 24-, 36-, and 48-month follow-ups. Patients with RVs demonstrated LS BMD percentage changes of 40.1 ± 22.1% (vs. no RVs group 26.2 ± 14.8%, p = 0.57) after 48-month follow-ups. In conclusion, our study highlights the significant clinical burden of PLO. Genetic RVs are prevalent in Chinese PLO patients. After bisphosphonate treatment, there is a significant increase in BMD, especially in LS. Patients with RVs have the potential of more robust therapeutic response.

Effects of Pregnancy and Lactation on Bone Microstructure and Material Properties in a Rat Model of Bariatric Surgery

Obesity is a major public health issue worldwide. Despite various approaches to weight loss, the most effective technique for reducing obesity, as well as diabetes and associated diseases, is bariatric surgery. Increasingly, young women without children are undergoing bariatric surgery, vertical sleeve gastrectomy (VSG) being the most common procedure nowadays. However, despite several reports suggesting bone loss after VSG, little is known about the potential additive effects of gestation and lactation after VSG to bone health. This study investigated the combined effects of pre-gestational VSG and subsequent gestation/lactation on bone metabolism in a rat model fed a high fat high sugar (HFHS) diet, with a focus on bone biomechanics, mass, microarchitecture and material properties. Furthermore, bone mass and remodelling were followed longitudinally by microCT prior to surgery, 4 weeks post-surgery, after weaning and at sacrifice. Significant alterations in bone mass and microarchitecture, characterized by changes in trabecular thickness and number, as well as changes in bone formation and resorption were influenced by both surgery and reproductive demands. Mechanical testing at sacrifice demonstrated compromised long bone fragility, in rat with HFHS regardless of the surgical procedure (Sham or VSG). Furthermore, analysis of bone material properties highlighted potential disruptions in the pattern of bone mineralization in sham and VSG animals fed a HFHS diet. These findings underscore the complex interplay between pre-gestational VSG and subsequent gestation/lactation in modulating bone metabolism in the investigated rat model. The preclinical rat model may help with optimizing surgical strategies and developing targeted interventions to mitigate potential bone-related complications associated with VSG in reproductive-aged individuals.

Neuroendocrinology of bone

The past decade has witnessed significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone in primary and secondary osteoporosis. Recent breakthroughs have primarily emerged from identifying disease-causing mutations and phenocopying human bone disease in rodents. Notably, using genetically-modified rodent models, disrupting the reciprocal relationship with tropic pituitary hormone and effector hormones, we have learned that pituitary hormones have independent roles in skeletal physiology, beyond their effects exerted through target endocrine glands. The rise of follicle-stimulating hormone (FSH) in the late perimenopause may account, at least in part, for the rapid bone loss when estrogen is normal, while low thyroid-stimulating hormone (TSH) levels may contribute to the bone loss in thyrotoxicosis. Admittedly speculative, suppressed levels of adrenocorticotropic hormone (ACTH) may directly exacerbate bone loss in the setting of glucocorticoid-induced osteoporosis. Furthermore, beyond their established roles in reproduction and lactation, oxytocin and prolactin may affect intergenerational calcium transfer and therefore fetal skeletal mineralization, whereas elevated vasopressin levels in chronic hyponatremic states may increase the risk of bone loss.. Here, we discuss the interaction of each pituitary hormone in relation to its role in bone physiology and pathophysiology.

Sea buckthorn and its flavonoids isorhamnetin, quercetin, and kaempferol favorably influence bone and breast tissue health

Bone tissue and breast tissue are interrelated, as demonstrated by breast microcalcifications, breast cancer bone metastases, bone morphogenetic proteins, and Wnt signaling. In addition, osteoblasts and osteoclasts represent an important switch of tumor cell dormancy during bone metastasis. Damage to both types of tissues mentioned above is highly prevalent, especially in postmenopausal women, and manifests itself in osteoporosis and breast cancer. Sea buckthorn (Elaeagnus rhamnoides L.), a botanical drug with high antioxidant, antitumor, anti-inflammatory, immunomodulatory, and regenerative properties, has great therapeutic potential due to the unique composition of its bioactive metabolites. This review aimed to summarize the current knowledge from in vitro and in vivo studies on the effect of sea buckthorn, as well as its most widespread flavonoids isorhamnetin, quercetin, and kaempferol, on bone and breast tissue health. In vitro studies have revealed the beneficial impacts of sea buckthorn and aforementioned flavonoids on both bone health (bone remodeling, mineralization, and oxidative stress) and breast tissue health (cancer cell proliferation, apoptosis, tumor growth, and metastatic behavior). In vivo studies have documented their protective effects against disturbed bone microarchitecture and reduced bone strength in animal models of osteoporosis, as well as against tumor expansion and metastatic properties in animal xenograft models. In any case, further research and clinical trials are needed to carefully evaluate the potential therapeutic benefits of sea buckthorn and its flavonoids. Based on the available information, however, it can be concluded that these bioactive metabolites favorably affect both bone and breast tissue health.

PPARG in osteocytes controls cell bioenergetics and systemic energy metabolism independently of sclerostin levels in circulation

OBJECTIVE

The skeleton is one of the largest organs in the body, wherein metabolism is integrated with systemic energy metabolism. However, the bioenergetic programming of osteocytes, the most abundant bone cells coordinating bone metabolism, is not well defined. Here, using a mouse model with partial penetration of an osteocyte-specific PPARG deletion, we demonstrate that PPARG controls osteocyte bioenergetics and their contribution to systemic energy metabolism independently of circulating sclerostin levels, which were previously correlated with metabolic status of extramedullary fat depots.

METHODS

In vivo and in vitro models of osteocyte-specific PPARG deletion, i.e. Dmp1CrePparγflfl male and female mice (γOTKO) and MLO-Y4 osteocyte-like cells with either siRNA-silenced or CRISPR/Cas9-edited Pparγ. As applicable, the models were analyzed for levels of energy metabolism, glucose metabolism, and metabolic profile of extramedullary adipose tissue, as well as the osteocyte transcriptome, mitochondrial function, bioenergetics, insulin signaling, and oxidative stress.

RESULTS

Circulating sclerostin levels of γOTKO male and female mice were not different from control mice. Male γOTKO mice exhibited a high energy phenotype characterized by increased respiration, heat production, locomotion and food intake. This high energy phenotype in males did not correlate with "beiging" of peripheral adipose depots. However, both sexes showed a trend for reduced fat mass and apparent insulin resistance without changes in glucose tolerance, which correlated with decreased osteocytic responsiveness to insulin measured by AKT activation. The transcriptome of osteocytes isolated from γOTKO males suggested profound changes in cellular metabolism, fuel transport, mitochondria dysfunction, insulin signaling and increased oxidative stress. In MLO-Y4 osteocytes, PPARG deficiency correlated with highly active mitochondria, increased ATP production, and accumulation of reactive oxygen species (ROS).

CONCLUSIONS

PPARG in male osteocytes acts as a molecular break on mitochondrial function, and protection against oxidative stress and ROS accumulation. It also regulates osteocyte insulin signaling and fuel usage to produce energy. These data provide insight into the connection between osteocyte bioenergetics and their sex-specific contribution to the balance of systemic energy metabolism. These findings support the concept that the skeleton controls systemic energy expenditure via osteocyte metabolism.

Memory T-Cells Contribute to Calcium Release from Bones during Lactation in Mice

Objective: Milk production during lactation places a high demand for calcium that is fulfilled both from maternal bone resorption and diet. While it is known that mammary gland-derived PTHrP drives bone resorption during lactation, the impact of postpartum estrogen loss on bone has been unclear. Methods: We used a case-control study design to test the effect of estrogen loss in lactating mice. Results: In the present study, we show for the first time that estrogen loss during lactation activates memory T-cells (TM) to produce TNFα and IL-17A to aid in bone resorption and calcium release. Our studies reveal a new mechanism for the release of calcium from bone postpartum. The findings provide several new insights. First, the immune system plays a critical role in milk production postpartum. Second, evolutionarily, the pathway serves the physiological purpose of increasing bone resorption to release calcium for breastmilk production postpartum but becomes maladaptive postmenopause, leading to osteoporosis. Finally, these results highlight the crosstalk between the brain-bone-breast-endocrine axis and the immune system during lactation.

Bone Metabolism, Bone Mass, and Bone Structure During Pregnancy and Lactation: Normal Physiology and Pregnancy and Lactation-Associated Osteoporosis

This article reviews bone metabolism, bone mass, and bone structure changes expected during and after pregnancy and lactation, as well as the condition of pregnancy and lactation-associated osteoporosis (PLO)-a presentation with fragility fracture(s) in the context of these physiologic changes. Clinical implications of physiologic bone changes will be addressed, as will specific management considerations that apply to premenopausal women with PLO.

Breastmilk mineral composition among well-educated mothers from Central Poland - Associations with maternal dietary intake, dietary patterns and infant psychomotor development

BACKGROUND

Maternal dietary habits could affect breastmilk mineral composition, which may influence infant development. Mineral dietary intake or supplementation slightly affects its breastmilk concentration. However, the intake of selected food groups or dietary patterns that reflect diet complexity could have a greater impact. Hence, the aim of the study was to assess breastmilk mineral composition at one, three, and six months of lactation among mothers living in urban area of Central Poland, as well as the evaluate maternal dietary determinants and associations with infant anthropometric and psychomotor development.

METHODS

The study was conducted among 43 healthy and exclusively breastfeeding mothers. In the first, third, and sixth months of lactation, we collected breastmilk samples and assessed the concentration of Ca, P, Zn, Fe, Se, Ni, As, Pb, and Cd using the ICP-MS method. Maternal dietary habits were evaluated by a food frequency questionnaire in the first month of lactation, whereas in the third and sixth by the three-day food record. Based on the collected data adherence to the Polish-adapted Mediterranean (Pl-aMED; 1 month) and the DASH diet (Mellen's Index; 3 and 6 months) was assessed. In the third and sixth months of lactation infant anthropometric parameters and the sixth month of lactation psychomotor development were evaluated.

RESULTS

Breastmilk Se, Ni, As, Pb, and Cd levels were under the LOQ in all the breastmilk samples at all study visits. Median breastmilk mineral concentrations of Ca, P, Zn, and Fe in the first, third, and sixth months of lactation varied from 381.9 to 332.7 mg/L, 161.6 to 139.1 mg/L, 2.2 to 0.8 mg/L, and 0.26 to 0.17 mg/L, respectively. Maternal dietary intake and supplementation did not affect breastmilk Ca, P, Zn, and Fe. Pl-aMED scores were associated with breastmilk Ca (β = 0.489, 95% CI 0.180 - 0.799, p = 0.003) and Zn (β = 0.499, 95% CI 0.199 - 0.798, p = 0.002) in the first month of lactation, whereas no association with the DASH diet were observed in the third and sixth month of lactation. Breastmilk Fe in the third month was associated with infant motor development (β = 0.420, 95% CI 0.113 - 0.727, p = 0.009) in the sixth month of life, but no other associations with anthropometric or psychomotor development were observed. Moreover, we estimated that few infants meet their adequate intake (AI) requirements for P, Zn, and Fe.

CONCLUSION

Our study showed that maternal adherence to Pl-aMED is a significant predictor of breastmilk Ca and Zn in the first month of lactation, which may be especially important considering that more than 75% of infants had inadequate Zn intake. Moreover, we found that breastmilk Fe positively influenced infant motor development, despite the majority of infants having inadequate intake. On the other hand, no infant had deficiency symptoms, which emphasizes the necessity to evaluate of AI norms for infants.

The Role of Osteocytes in Pre-metastatic Niche Formation

PURPOSE OF REVIEW

The formation of a pre-metastatic niche (PMN), in which primary cancer cells prime the distant site to be favorable to their engraftment and survival, may help explain the strong osteotropism observed in multiple cancers, such as breast and prostate. PMN formation, which includes extracellular matrix remodeling, increased angiogenesis and vascular permeability, enhanced bone marrow-derived cell recruitment and immune suppression, has mostly been described in soft tissues. In this review, we summarize current literature of PMN formation in bone. We also present evidence of a potential role for osteocytes to be the primary mediators of PMN development.

RECENT FINDINGS

Osteocytes regulate the bone microenvironment in myriad ways beyond canonical bone tissue remodeling, including changes that contribute to PMN formation. Perilacunar tissue remodeling, which has been observed in both bone and non-bone metastatic cancers, is a potential mechanism by which osteocyte-cancer cell signaling stimulates changes to the bone microenvironment. Osteocytes also protect against endothelial permeability, including that induced by cancer cells, in a loading-mediated process. Finally, osteocytes are potent regulators of cells within the bone marrow, including progenitors and immune cells, and might be involved in this aspect of PMN formation. Osteocytes should be examined for their role in PMN formation.

Breastfeeding Duration Is Associated with the Risk of Tooth Loss, Chewing Difficulty, and Undernutrition among Older Korean Women: Results of the Korea National Health and Nutrition Examination Survey (KNHANES) 2013-2015

We investigated whether older Korean women with prolonged breastfeeding duration have an increased risk of tooth loss, chewing difficulty, or undernutrition, as well as whether tooth loss and chewing difficulty mediate the association between breastfeeding duration and undernutrition risk. This study included 1666 women aged ≥65 years from the 2013-2015 Korea National Health and Nutrition Examination Survey who breastfed after delivery. The number of teeth and chewing ability were investigated based on the status of individual teeth and a self-report questionnaire, respectively. Dietary intake was estimated using the 24 h recall method. Compared with women who breastfed for 1-18 months, the odds ratios for tooth loss were 1.16 (95% confidence interval [CI] = 0.69-1.94), 1.79 (95% CI = 1.08-2.94), and 1.86 (95% CI = 1.16-2.97) among women who breastfed for 19-36, 37-72, and ≥73 months, respectively (p for trend = 0.004). Similar results were obtained for chewing difficulty and undernutrition. Furthermore, tooth loss and chewing difficulty partially mediated the association between breastfeeding duration and undernutrition risk. In conclusion, older Korean women who breastfed for longer periods are more likely to experience tooth loss, chewing difficulty, and undernutrition, which are particularly severe among women who breastfed for ≥37 months. The association between breastfeeding duration and undernutrition risk is mediated by tooth loss and chewing difficulty.

Pituitary crosstalk with bone, adipose tissue and brain

Traditional textbook physiology has ascribed unitary functions to hormones from the anterior and posterior pituitary gland, mainly in the regulation of effector hormone secretion from endocrine organs. However, the evolutionary biology of pituitary hormones and their receptors provides evidence for a broad range of functions in vertebrate physiology. Over the past decade, we and others have discovered that thyroid-stimulating hormone, follicle-stimulating hormone, adrenocorticotropic hormone, prolactin, oxytocin and arginine vasopressin act directly on somatic organs, including bone, adipose tissue and liver. New evidence also indicates that pituitary hormone receptors are expressed in brain regions, nuclei and subnuclei. These studies have prompted us to attribute the pathophysiology of certain human diseases, including osteoporosis, obesity and neurodegeneration, at least in part, to changes in pituitary hormone levels. This new information has identified actionable therapeutic targets for drug discovery.

Bridging the Gap: Pregnancy-And Lactation-Associated Osteoporosis

Early diagnosis of pregnancy- and lactation-associated osteoporosis (PLO) is mandatory for a good outcome. Standard care is not a matter of conventional guidelines, rather it requires an individualized strategy while true overall incidence and pathogeny remain open issues. This is a narrative review based on full-length English articles, published between January 2021 and March 2023 and accessed via PubMed (no traumatic fractures or secondary osteoporosis are included). Our case-sample-based analysis included 836 females with PLO (the largest cohort based on published cases so far) through 12 studies and 24 single case reports. Except for one survey, these involved retrospective cohorts of small size (6-10 females/study) to medium size (23-47 women/study), and large cohorts with >50 subjects per study (a maximum of 379). Age of diagnosis: from 24 to 40 years for case reports (most subjects being over 30 and primigravida), while original studies indicated an average age between 31 and 34.18 years. Type of fractures underlined a most frequent vertebral phenotype (a mean of 2 to 5.8 vertebral fractures per patient) versus a most severe non-vertebral phenotype (hip and femoral neck fractures mostly requiring surgery). Potential contributors varied: smoking (1/3-1/2 of subjects), family history of osteoporosis (1/3), heparin and glucocorticoid use in pregnancy, low body mass index (majority of cases), hypovitaminosis D; and (with a low level of statistical significance) anti-psychotic medication, gestational diabetes, lupus, thrombophilia, anemia, in vitro fertilization (1/3 in one study), twin pregnancy, tocolysis with MgSO4, and postpartum thyroiditis. Most remarkably, up to 50% of PLO patients harbor mutations of LRP5, WNT1, and COL1A1/A2 (more damaged form with potential benefits from osteoanabolic drugs); gene testing might become the new norm in PLO. The low index of clinical suspicion should be supported by performing magnetic resonance imaging (gold standard in pregnancy) with DXA (in lactation). Low bone mineral density is expected (Z-score varying from -2.2 SD to -4 SD, unless normal which does not exclude PLO). Bone turnover markers might be useful in individuals with normal DXA, in pregnancy when DXA cannot be performed, and in following the response to anti-osteoporosis drugs. Alternatively, microarchitecture damage might be reflected by DXA-trabecular bone score and high-resolution peripheral quantitative computed tomography. Specific medical interventions are currently focused on teriparatide (TPT) use (3 studies; n = 99 females treated with TPT and an additional subgroup of 18 patients from the gene-analysis-based study, thus a total of 117 females) which seems to be the therapy of choice as reflected by these new data: 6-24 months, 20 µg/day, no sequential therapy needed; case selection based on high fracture risk is necessary). The first case using romosozumab was reported in 2022. PAO/LAO remains a challenging condition which is a battle for the wellbeing of two individuals, on one hand, considering maternal-fetal outcomes and taking care of the offspring, but it is a battle for a multidisciplinary team, on the other hand, since a standardized approach is lacking.