Aromatase inhibitors are widely used in the treatment of hormone-sensitive breast cancer, but their suppression of estrogen production accelerates bone loss, increases fracture risk, and negatively impacts muscle and fat metabolism. Here, we demonstrate that daily low intensity vibration, serving as a non-drug mimetic for exercise, protects musculoskeletal health in skeletally immature, female mice under complete estrogen deprivation. Subsequent improvements in vertebral bone density are paralleled by greater and leaner skeletal muscle mass and function alongside reduced fat accretion and circulating metabolites. In mature, estrogen deprived mice, vibration enhances weekly bisphosphonate treatment, improving bone density, cortical thickness, and mechanical resistance to fracture. These findings support the proposed hypothesis that low intensity vibration reduces musculoskeletal frailty in estrogen deprived mice, with stronger effects observed in younger cohorts, while in skeletally mature mice combination therapy with anti-resorptive treatment is necessary to suppress cancer-treatment induced musculoskeletal degradation.

Accelerated bone loss has been reported in the early stages of Alzheimer's disease (AD) as indicated by reduced bone mineral density and increased fracture risk in these patients, compared to healthy individuals. In the present study, we investigated bone loss in mouse models of familial Alzheimer's disease harboring the Presenilin 1 (L166P) knock-in mutation (PSEN1 KI), with or without the human amyloid precursor protein transgene (hAPP Tg+) known to induce brain amyloid pathology by 6 months. Female and not male 12-month PSEN1/hAPP Tg+ mice exhibited reduced whole-body bone mineral density and bone mineral content, compared to sex-matched controls. Consistent with PSEN1 L166P driving the phenotype, female PSEN1 KI mice lacking the hAPP transgene also displayed low bone mass with a reduction in bone microarchitecture observed as early as 1 month of age. Correspondingly, PSEN1 KI mice exhibit reduced cortical and trabecular bone mass compared to age- and sex-matched control mice. The loss of bone microarchitecture was largely attributed to a reduction in bone formation as indicated by decreases in serum P1NP levels and osteoblast ALP activity and mRNA expression in vitro. At the ages examined, PSEN1 KI mice exhibited increased follicle stimulating hormone (FSH) levels, which is known to cause a decrease in bone mass. Western blotting also identified both PSEN1 and amyloid-beta protein expression in bone and brain tissue. Taken together, the data indicate that female-specific bone loss in familial AD is potentially due to the direct actions of mutant PSEN1 in bone cells combined with systemic crosstalk caused by brain-expressed PSEN1 L116P.

Comorbidities are becoming increasingly evident during various Alzheimer’s disease related pathologies. It was found that patients with AD have a higher risk for fractures and falls. Further people who have an incident of falls/fractures have a higher risk for cognitive decline. This study is focused on investigating the alterations in the bone at the structural and functional level in MAPT P301S Tg+ mouse, a preclinical model for frontotemporal dementia. The MAPT P301S Tg+ mouse expresses a human 4-repeat mutant MAPT P301S and was developed to model NFTs secondary to tau aggregations. The femur from N = 20 (equal number of male and female) MAPT P301S Tg+ and C57BL/6J mice at 12-months age were scanned with µCT to characterize the bone microarchitecture. Further three-point bending test was performed to assess the biomechanical properties and FTIR was used to determine the material properties of the bone. The expression of genes regulating the bone matrix composition was determined by using RTPCR. The male MAPT P301S Tg+ mice have a significant decrease in bone geometrical parameters (both cortical and trabecular properties) than the females, as compared to their respective wild type. Interestingly the biomechanical properties were altered in both the males and females, wherein there was an increase in the pre-yield properties, but decrease in the post-yield properties. This correlated with the alterations in the material properties of the male bone determined by FTIR and the changes in the genes regulating the extracellular matrix of the bone. Tauopathies lead to loss of bone structure and functionality by altering it’s material composition. Further, we found protein expression This is a first study indicating the presence of Tau in the bone, which impacts the function and this opens up the prospective of Tau impacting other organs, in addition or concurrently with neurodegenerative diseases.

BackgroundHypertension is seen in 70% of patients with autosomal dominant polycystic kidney disease by age of 30 years before decline in kidney function. However, cardiac origins of hypertension, such as the natriuretic peptide signaling pathway, have not been fully investigated. We hypothesized that cardiomyocyte localized polycystin proteins contribute to production of natriuretic peptides, and loss of this pathway would contribute to hypertension.MethodsTelemetry, echocardiography, and a molecular analysis of the natriuretic peptide pathway from left ventricular tissue of cardiomyocyte specific knockout models of polycystin-2 (cPC2-KO) mice and Cre control littermates were conducted. Complementary studies were conducted in ex vivo murine hearts, engineered heart tissue with human iPSCs driven into cardiomyocytes with CRISPR/Cas9 knockout of PKD2 and in in vitro cell lines.ResultscPC2-KO mice demonstrated diurnal hypertension. Circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide were unchanged between cPC2-KO and Cre mice. Analysis of the pathways involved in production, maturation, and activity of natriuretic peptides identified decreased transcription of chromogranin B, PCSK6, NPR1, and NFAT genes in cPC2-KOs. Human iPSC-derived cardiomyocytes with PC2-KO failed to produce ANP. Re-expression of polycystin-2 in a myoblast cell line, but not pathogenic forms of polycystin-2, restored ANP production.ConclusionsNatriuretic peptide production required cardiac localized polycystin-2, and loss of this pathway may contribute to the development of hypertension in autosomal dominant polycystic kidney disease.

Despite their beneficial actions as immunosuppressants, glucocorticoids (GC) have devastating effects on the musculoskeletal and cardiac systems, as long-term treated patients exhibit high incidence of falls, bone fractures, and cardiovascular events. Herein, we show that GC upregulate simultaneously in bone, skeletal muscle, and the heart the expression of E3 ubiquitin ligases (atrogenes), known to stimulate the proteasomal degradation of proteins. Activation of vitamin D receptor (VDR) signaling with the VDR ligands calcitriol or eldecalcitol prevented GC-induced atrogene upregulation in vivo and ex vivo in bone/muscle organ cultures and preserved tissue structure/mass and function of the 3 tissues in vivo. Direct pharmacologic inhibition of the proteasome with carfilzomib also conferred musculoskeletal protection. Genetic loss of the atrogene MuRF1-mediated protein ubiquitination in ΔRING mice afforded temporary or sustained protection from GC excess in bone or skeletal and heart muscle. We concluded that the atrogene pathway downstream of MuRF1 underlies GC action in bone, muscle, and the heart, and it can be pharmacologically or genetically targeted to confer protection against the damaging actions of GC simultaneously in the 3 tissues.

ABSTRACT Cardiovascular complications are the most common cause of mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Hypertension is seen in 70% of patients by the age of 30 prior to decline in kidney function. The natriuretic peptides (NPs), atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are released by cardiomyocytes in response to membrane stretch, increasing urinary excretion of sodium and water. Mice heterozygous for Pkd2 have attenuated NP responses and we hypothesized that cardiomyocyte-localized polycystin proteins contribute to production of NPs. Cardiomyocyte-specific knock-out models of polycystin-2 (PC2), one of the causative genes of ADPKD, demonstrate diurnal hypertension. These mice have decreased ANP and BNP expression in the left ventricle. Analysis of the pathways involved in production, maturation, and activity of NPs identified decreased transcription of CgB, PCSK6, and NFAT genes in cPC2-KOs. Engineered heart tissue with human iPSCs driven into cardiomyocytes with CRISPR/Cas9 KO of PKD2 failed to produce ANP. These results suggest that PC2 in cardiomyocytes are involved in NP production and lack of cardiac PC2 predisposes to a hypertensive volume expanded phenotype, which may contribute to the development of hypertension in ADPKD.

Combination treatment of Low-Intensity Vibration (LIV) with zoledronic acid (ZA) was hypothesized to preserve bone mass and muscle strength while reducing adipose tissue accrual associated with complete estrogen (E 2 )-deprivation in young and skeletally mature mice. Complete E 2 -deprivation (surgical-ovariectomy (OVX) and daily injection of aromatase inhibitor (AI) letrozole) were performed on 8-week-old C57BL/6 female mice for 4 weeks following commencement of LIV administration or control (no LIV), for 28 weeks. Additionally, 16-week-old C57BL/6 female E 2 -deprived mice were administered ±LIV twice daily and supplemented with ±ZA (2.5 ng/kg/week). By week 28, lean tissue mass quantified by dual-energy X-ray absorptiometry was increased in younger OVX/AI+LIV(y) mice, with increased myofiber cross-sectional area of quadratus femorii. Grip strength was greater in OVX/AI+LIV(y) mice than OVX/AI(y) mice. Fat mass remained lower in OVX/AI+LIV(y) mice throughout the experiment compared with OVX/AI(y) mice. OVX/AI+LIV(y) mice exhibited increased glucose tolerance and reduced leptin and free fatty acids than OVX/AI(y) mice. Trabecular bone volume fraction and connectivity density increased in the vertebrae of OVX/AI+LIV(y) mice compared to OVX/AI(y) mice; however, this effect was attenuated in the older cohort of E 2 -deprived mice, specifically in OVX/AI+ZA mice, requiring combined LIV with ZA to increase trabecular bone volume and strength. Similar improvements in cortical bone thickness and cross-sectional area of the femoral mid-diaphysis were observed in OVX/AI+LIV+ZA mice, resulting in greater fracture resistance. Our findings demonstrate that the combination of mechanical signals in the form of LIV and anti-resorptive therapy via ZA improve vertebral trabecular bone and femoral cortical bone, increase lean mass, and reduce adiposity in mice undergoing complete E 2 -deprivation. One Sentence Summary: Low-magnitude mechanical signals with zoledronic acid suppressed bone and muscle loss and adiposity in mice undergoing complete estrogen deprivation.Translational Relevance:Postmenopausal patients with estrogen receptor-positive breast cancer treated with aromatase inhibitors to reduce tumor progression experience deleterious effects to bone and muscle subsequently develop muscle weakness, bone fragility, and adipose tissue accrual. Bisphosphonates (i.e., zoledronic acid) prescribed to inhibit osteoclast-mediated bone resorption are effective in preventing bone loss but may not address the non-skeletal effects of muscle weakness and fat accumulation that contribute to patient morbidity. Mechanical signals, typically delivered to the musculoskeletal system during exercise/physical activity, are integral for maintaining bone and muscle health; however, patients undergoing treatments for breast cancer often experience decreased physical activity which further accelerates musculoskeletal degeneration. Low-magnitude mechanical signals, in the form of low-intensity vibrations, generate dynamic loading forces similar to those derived from skeletal muscle contractility. As an adjuvant to existing treatment strategies, low-intensity vibrations may preserve or rescue diminished bone and muscle degraded by breast cancer treatment.

Ubiquitin proteasome system was found to contribute to bone loss by regulating bone turnover and metabolism, by modulating osteoblast differentiation and bone formation as well as formation of osteoclasts that contribute to bone resorption. Muscle Ring Finger (MuRF) are novel ubiquitin ligases, which are muscle specific and have not been much implicated in the bone but have been implicated in several human diseases including heart failure and skeletal muscle atrophy. This study is aimed at understanding the role of MuRF1, MuRF2, MuRF3 and Atrogin which are distinct MuRF family proteins in bone homeostasis. Wildtype, heterozygous and homozygous mice of each of the isoforms were used and the bone microarchitecture and mechanical properties were assessed using microCT and biomechanics. MuRF1 depletion was found to alter cortical properties in both males and females, but only trabecular spacing in the females. MuRF2 depletion let to no changes in the cortical and trabecular properties but change in the strain to yield in the females. Depletion of MuRF3 led to decrease in the cortical properties in the females and increase in the trabecular properties in the males. Atrogin depletion was found to reduce cortical properties in both males and females, whereas some trabecular properties were found to be reduced in the females. Each muscle-specific ligase was found to alter the bone structure and mechanical properties in a distinct a sex-dependent manner.

Heart failure (HF) develops from a diverse range of genetic and environmental factors that compromise cardiac function, ultimately resulting in insufficient blood flow to the body. HF is a broad, encompassing term for a chronic, progressive, and highly complex clinical syndrome. The pathophysiology of HF has multiorgan manifestations, primarily in the renal, autonomic, vascular, and cardiac systems, stemming from the specific etiology of the disease. The vast array of factors initiating HF are equally accompanied by diverse and distinct cellular changes that compromise cardiomyocytes, along with the structure and function of the organ. Our understanding of the molecular and biochemical changes that underlie the development and progression of HF has expanded greatly, which facilitated improved patient clustering into HF-specific disease pathobiology and subsequent advancements in both surgical and pharmacological approaches in the therapeutic management of HF. This chapter provides an overview of the recent advances regarding HF, spanning cardiac physiology to intracellular molecular events in the cardiomyocyte, and the current therapeutic strategies to clinically manage HF.

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the SARS-CoV-2 betacoronavirus and has taken over 761,426 American lives as of the date of publication and will likely result in long-term, if not permanent, tissue damage for countless patients. COVID-19 presents with diverse and multisystemic pathologic processes, including a hyperinflammatory response, acute respiratory distress syndrome (ARDS), vascular injury, microangiopathy, tissue fibrosis, angiogenesis, and widespread thrombosis across multiple organs, including the lungs, heart, kidney, liver, and brain. C-X-C chemokines contribute to these pathologies by attracting inflammatory mediators, the disruption of endothelial cell integrity and function, and the initiation and propagation of the cytokine storm. Among these, CXCL10 is recognized as a critical contributor to the hyperinflammatory state and poor prognosis in COVID-19. CXCL10 is also known to regulate growth factor-induced fibrosis, and recent evidence suggests the CXCL10-CXCR3 signaling system may be vital in targeting convergent pro-inflammatory and pro-fibrotic pathways. This review will explore the mechanistic role of CXCL10 and related chemokines in fibrotic complications associated with COVID-19 and the potential of CXCL10-targeted therapeutics for early intervention and long-term treatment of COVID-19-induced fibrosis.

MicroRNA-150 (miR-150) is downregulated in patients with multiple cardiovascular diseases and in diverse mouse models of heart failure (HF). miR-150 is significantly associated with HF severity and outcome in humans. We previously reported that miR-150 is activated by β-blocker carvedilol (Carv) and plays a protective role in the heart using a systemic miR-150 KO mouse model. However, mechanisms that regulate cell-specific miR-150 expression and function in HF are unknown. Here, we demonstrate that potentially novel conditional cardiomyocyte-specific (CM-specific) miR-150 KO (miR-150 cKO) in mice worsens maladaptive cardiac remodeling after myocardial infarction (MI). Genome-wide transcriptomic analysis in miR-150 cKO mouse hearts identifies small proline-rich protein 1a (Sprr1a) as a potentially novel target of miR-150. Our studies further reveal that Sprr1a expression is upregulated in CMs isolated from ischemic myocardium and subjected to simulated ischemia/reperfusion, while its expression is downregulated in hearts and CMs by Carv. We also show that left ventricular SPRR1A is upregulated in patients with HF and that Sprr1a knockdown in mice prevents maladaptive post-MI remodeling. Lastly, protective roles of CM miR-150 are, in part, attributed to the direct and functional repression of proapoptotic Sprr1a. Our findings suggest a crucial role for the miR-150/SPRR1A axis in regulating CM function post-MI.

Over 50 million people worldwide have dementia, one of its most common form being Alzheimer’s disease. It’s one of the top ten leading causes of death attributing to the extraneuronal effects in the bone, skeletal muscle, liver, kidney, and heart. Falls and fractures are one of the predominant causes of mortality in AD patients, indicating the cross talk between the bone and brain during AD. Women with lower femoral BMD were two times more risk‐prone to develop AD than women with higher BMD and this was found to be independent of other risk factors of AD. In this study, we are investigating the changes in the bone markers during early stages of the AD.

The association between reduced myofilament force-generating capacity (F-max) and heart failure (HF) is clear, however the underlying molecular mechanisms are poorly understood. Here, we show impaired F-max arises from reduced BAG3-mediated sarcomere turnover. Myofilament BAG3 expression decreases in human HF and positively correlates with F-max. We confirm this relationship using BAG3 haploinsufficient mice, which display reduced F-max and increased myofilament ubiquitination, suggesting impaired protein turnover. We show cardiac BAG3 operates via chaperone-assisted selective autophagy (CASA), conserved from skeletal muscle, and confirm sarcomeric CASA complex localization is BAG3/proteotoxic stress-dependent. Using mass spectrometry, we characterize the myofilament CASA interactome in the human heart and identify eight clients of BAG3-mediated turnover. To determine if increasing BAG3 expression in HF can restore sarcomere proteostasis/F-max, HF mice were treated with rAAV9-BAG3. Gene therapy fully rescued F-max and CASA protein turnover after four weeks. Our findings indicate BAG3-mediated sarcomere turnover is fundamental for myofilament functional maintenance. Decreased expression of BAG3 in the heart is associated with contractile dysfunction and heart failure. Here the authors show that this is due to decreased BAG3-dependent sarcomere protein turnover, which impairs mechanical function, and that sarcomere force-generating capacity is restored with BAG3 gene therapy.

Proteotoxicity from insufficient clearance of misfolded/damaged proteins underlies many diseases. Carboxyl terminus of Hsc70-interacting protein (CHIP) is an important regulator of proteostasis in many cells, having E3-ligase and chaperone functions and often directing damaged proteins towards proteasome recycling. While enhancing CHIP functionality has broad therapeutic potential, prior efforts have all relied on genetic upregulation. Here we report that CHIP-mediated protein turnover is markedly post-translationally enhanced by direct protein kinase G (PKG) phosphorylation at S20 (mouse, S19 human). This increases CHIP binding affinity to Hsc70, CHIP protein half-life, and consequent clearance of stress-induced ubiquitinated-insoluble proteins. PKG-mediated CHIP-pS20 or expressing CHIP-S20E (phosphomimetic) reduces ischemic proteo- and cytotoxicity, whereas a phospho-silenced CHIP-S20A amplifies both. In vivo, depressing PKG activity lowers CHIP-S20 phosphorylation and protein, exacerbating proteotoxicity and heart dysfunction after ischemic injury. CHIP-S20E knock-in mice better clear ubiquitinated proteins and are cardio-protected. PKG activation provides post-translational enhancement of protein quality control via CHIP.

Alzheimer disease (AD) is characterized by deterioration of cognitive capabilities with an estimated 44 million individuals worldwide living with it. Beyond memory deficits, the most common AD co-morbidities include swallowing defects (muscle), fractures (bone, muscle), and heart failure. The underlying causes of these co-morbidities and their role in AD pathophysiology are currently unknown. This review is the first to summarize the emerging picture of the cardiac and musculoskeletal deficits in human AD. We present the involvement of the heart, characterized by diastolic heart failure, the presence of amyloid deposits, and electrophysiological changes, compared with age-matched control subjects. The characteristic musculoskeletal defects in AD come from recent clinical studies and include potential underlying mechanisms (bone) in animal models. These studies detail a primary muscle weakness (without a loss of muscle mass) in patients with mild cognitive impairment, with progression of cognitive impairment to AD associating with ongoing muscle weakness and the onset of muscle atrophy. We conclude by reviewing the loss of bone density in patients with AD, paralleling the increase in fracture and fall risk in specific populations. These studies paint AD as a systemic disease in broad strokes, which may help elucidate AD pathophysiology and to allow for new ways of thinking about therapeutic interventions, diagnostic biomarkers, and the pathogenesis of this multidisciplinary disease.

Ubiquitination plays a critical role in controlling protein turnover via proteasomal degradation, altering subcellular localization, and regulating protein activity. Functional role(s) for the Atrogin‐1 (MAFbx) ubiquitin ligase in regulating transcription factors have been found in skeletal muscle and the heart, but not in other organs. Within the myocyte, Atrogin‐1 localizes to the sarcomere and nucleus. We have previously reported that Atrogin‐1 is a critical regulator of pathologic and physiologic cardiac hypertrophy in vivo, involving specific interaction and ubiquitination of transcription factors central the signaling pathways driving these hypertrophic responses, including FOXO1/3. Recent studies have linked cardiomyocyte Atrogin‐1 to the regulation of the extracellular matrix. With evidence that cardiomyocyte Atrogin‐1 can affect cells other than myocytes, we analyzed Atrogin‐1−/− mice for their effects on metabolism and bone. DEXA whole body analysis of Atrogin‐1−/− mice revealed significantly decreased fat mass (15.6% vs. 35.8% fat, p<0.05) with a corresponding increase in lean mass (84.4% vs. 64.2%, p<0.05) at the age of 11–15 months, but not at 5 months, when compared to strain‐ and age‐matched wildtype (WT) control mice. Since the Atrogin‐1−/− mice weighed significantly less than WT mice (29±3 vs. 40±2 g, p<0.05), the net fat loss was 4.6 g (vs. 14.3 g in age‐matched WT) and the lean body mass identical between groups (25.7 vs. 24.6 g). Together these findings suggest Atrogin‐1’s role in regulating fat metabolism. Analysis of bone microarchitecture and mechanical properties of adult Atrogin‐1−/− mice was undertaken at 17–21 weeks of age, a time point where no phenotype has been previously observed in skeletal muscle or heart. Femurs were dissected and subsequently assessed by μCT (SkyScan 1172) for bone microarchitecture in the distal femur metaphysis (1 mm) and mid‐diaphysis region and challenged by a three‐point bending test to assess their material and structural properties. No differences in cortical or trabecular bone microarchitecture were identified and nor were any changes in mechanical properties. Together, these findings illustrate novel biological roles of Atrogin‐1 in regulating systemic fat metabolism, possibly involving crosstalk between skeletal muscle/heart and systemic fat metabolism. Our analysis provides an essential framework for the potential therapeutic targeting of ubiquitin ligases like Atrogin‐1 in the context of striated muscle and metabolic disease.Support or Funding InformationSupport: Lilly Foundation/Indiana Center for Musculoskeletal Health/ IU School of Medicine, Physician Scientist Initiative, Scientific Research Initiative