Bone mineral density is reduced by telmisartan in male spontaneously hypertensive rats

The relationship of telmisartan with sclerostin in the osteoporosis model induced by ovariectomy in rats

OBJECTIVES

Our aim is to explain the relationship between Ang II and Scl in osteoporotic (OP) rats and the contribution of Scl in the antiosteoporotic effect mechanism of angiotensin receptor blockers (ARB).

METHODS

This study consists of two sub-studies conducted on 4th and 12th weeks after ovariectomy. In study 1, treatment was started immediately after bilateral ovariectomy (OVX), while, in study 2, treatment was started 2 months after OVX. Two different doses of telmisartan (5 and 10 mg/kg) were administered with the aid of gavage for 30 days in both sub-study groups.

RESULTS

Serum and tissue Scl, osteocalcin, osteopontin and tartrate-resistant acid phosphatase mRNA expressions were higher and bone mineral densities (BMD) and bone-specific alkaline phosphatase (BALP) mRNA expressions were found to be lower in the OVX groups compared with the sham group. In OVX groups where two different doses of telmisartan were administered, BMD and BALP mRNA expressions increased and serum and tissue Scl decreased.

CONCLUSION

There may be a close relationship between angiotensin II and sclerostin in the development of osteoporosis. In this study, telmisartan administration showed an antiosteoporotic effect and significantly decreased the level of sclerostin. These results strongly support this relationship.

Telmisartan impairs the in vitro osteogenic differentiation of mesenchymal stromal cells from spontaneously hypertensive male rats

Telmisartan (TELM) is an angiotensin II (Ang II) type 1 receptor (Agtr1) antagonist, with partial agonism for Pparg, and has been shown to affect bone metabolism. Therefore, the aim of this study was to investigate the effects of TELM in the in vitro osteogenic differentiation of bone marrow-derived mesenchymal stromal cells (BMSC) from spontaneously hypertensive rats (SHRs). BMSC were obtained from male SHR, and the osteogenic medium (OM) was added to the cells concomitantly with TELM (0.005, 0.05, and 0.5 μM). Undifferentiated BMSC, in control medium (CM), showed an increased viability, while the addition of OM reduced this parameter, and TELM did not show cytotoxicity in the concentrations used. BMSC in OM had an alkaline phosphatase (ALP) activity peak at d10, which decreased at d14 and d21, and TELM reduced ALP at d10 in a dose-dependent manner. Mineralization was observed in the OM at d14, which intensified at d21, but was inhibited by TELM. Agtr1b was increased in the OM, and TELM inhibited its expression. TELM reduced Opn, Ocn, and Bsp and increased Pparg expression, and at the higher concentration TELM also increased the expression of adipogenic markers, Fabp4 and Adipoq. In addition, TELM 0.5 μM increased Irs1 and Glut4, insulin and glucose metabolism markers, known to be regulated by Pparg and to be related to adipogenic phenotype. Our data shows that TELM inhibited the osteogenic differentiation and mineralization of SHR BMSC, by favoring an adipogenic prone phenotype due to Pparg upregulation.

Effects of high-intensity interval training in more or less active mice on biomechanical, biophysical and biochemical bone parameters

High-intensity interval training (HIIT) is of scientific interest due its role in improving physical fitness, but the effects of HIIT on bone health need be carefully explored. Further, it is necessary to know whether HIIT effects on bone health are dependent on the physical activity levels. This may be experimentally tested since we have built a large cage (LC) that allows animals to move freely, promoting an increase of spontaneous physical activity (SPA) in comparison to a small cage (SC). Thus, we examined the effects of HIIT on biophysical, biomechanical and biochemical parameters of bone tissue of C57BL/6J mice living in cages of two different sizes: small (SC) or large (LC) cages with 1320 cm² and 4800 cm² floor space, respectively. Male mice were subdivided into two groups within each housing type: Control (C) and Trained (T). At the end of the interventions, all mice were euthanized to extract the femur bone for biophysical, biomechanical and biochemical analyses. Based a significant interaction from two-way ANOVA, trained mice kept in large cage (but not for trained mice housed in SC) exhibited a reduction of tenacity and displacement at failure in bone. This suggests that long-term HIIT program, in addition with a more active lifestyle correlates with exerts negative effects on the bone of healthy mice. A caution must also be raised about the excessive adoption of physical training, at least regarding bone tissue. On the other hand, increased calcium was found in femur of mice housed in LC. In line with this, LC-C mice were more active (i.e. SPA) than other groups. This implies that an active lifestyle without long-term high intensity physical training seems to play a role in promoting benefits to bone tissue. Our data provides new insights for treatment of osteo-health related disorders.

Telmisartan Prevents Alveolar Bone Loss by Decreasing the Expression of Osteoclasts Markers in Hypertensive Rats With Periodontal Disease

Periodontal disease (PD) is a prevalent inflammatory disease with the most severe consequence being the loss of the alveolar bone and teeth. We therefore aimed to evaluate the effects of telmisartan (TELM), an angiotensin II type 1 receptor (Agtr1) antagonist, on the PD-induced alveolar bone loss, in Wistar (W) and Spontaneous Hypertensive Rats (SHRs). PD was induced by ligating the lower first molars with silk, and 10 mg/kg TELM was concomitantly administered for 15 days. The hemimandibles were subjected to microtomography, ELISA was used for detecting tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), CXCL3, and CCL2, while qRT-PCR was used for analyzing expression of components of renin-angiotensin system (RAS) (Agt, Ace, Agt1r, Agt2r, Ace2, and Masr), and bone markers (Runx2, Osx, Catnb, Alp, Col1a1, Opn, Ocn, Bsp, Bmp2, Trap, Rank, Rankl, CtsK, Mmp-2, Mmp-9, and osteoclast-associated receptor (Oscar)). The SHR + PD group showed greater alveolar bone loss than the W + PD group, what was significantly inhibited by treatment with TELM, especially in the SHR group. Additionally, TELM reduced the production of TNF-α, IL-1β, and CXCL3 in the SHR group. The expression of Agt increased in the groups with PD, while Agtr2 reduced, and TELM reduced the expression of Agtr1 and increased the expression of Agtr2, in W and SHRs. PD did not induce major changes in the expression of bone formation markers, except for the expression of Alp, which decreased in the PD groups. The bone resorption markers expression, Mmp9, Ctsk, and Vtn, was higher in the SHR + PD group, compared to the respective control and W + PD group. However, TELM attenuated these changes and increased the expression of Runx2 and Alp. Our study suggested that TELM has a protective effect on the progression of PD, especially in hypertensive animals, as evaluated by the resorption of the lower alveolar bone. This can be partly explained by the modulation in the expression of Angiotensin II receptors (AT1R and AT2R), reduced production of inflammatory mediators, the reduced expression of resorption markers, and the increased expression of the bone formation markers.

Telmisartan use in rats with preexisting osteoporotics bone disorders increases bone microarchitecture alterations via PPARγ

AIMS

Telmisartan (TEL), an angiotensin II type I receptor blocker and PPARγ partial agonist, has been used for to treat hypertension. It is known that PPARγ activation induces bone loss. Therefore, we evaluate the effects of telmisartan on PPARγ protein expression, biomechanics, density and bone microarchitecture of femurs and lumbar vertebrae in SHR ovariectomized animals, a model of hypertension in which preexisting bone impairment has been demonstrated.

MAIN METHODS

SHR females (3 months old) were distributed into four groups: sham (S), sham + TEL (ST), OVX (C) and OVX + TEL (CT). TEL (5 mg/kg/day) or vehicle were administered according to the groups. After the protocol, blood pressure was measured and density, microarchitecture and biomechanics of bone were analyzed. Western blotting analysis was performed to evaluate PPARγ protein expression in the bones.

KEY FINDINGS

Castration induced a deleterious effect on mineral density and trabecular parameters, with telmisartan enhancing such effects. Telmisartan increased PPARγ levels, which were at their highest when the treatment was combined with castration. As to biomechanical properties, telmisartan reduced the stiffness in the castration group (CT vs. S or C group), as well as resilience and failure load in ST group (vs. all others groups).

SIGNIFICANCE

These results demonstrated that telmisartan compromised bone density and microarchitecture in animals that shows preexisting osteoporotic bone disorders, probably via mechanisms associated with increased PPARγ. If this translates to humans, a need for greater caution in the use of telmisartan by patients that have preexisting bone problems, as in the postmenopausal period, may be in order.

Exposure to tobacco smoke increases bone loss in spontaneously hypertensive rats

PURPOSE

To define if exposure to tobacco smoke (TS) could induce reduction of bone mass and impairment of bone architecture, features observed in osteoporosis in normotensive rats and the influence of TS exposure on the osteoporotic features exhibited in the spontaneously hypertensive (SH) rats.

METHODS

Normotensive Wistar Kyoto (WKY) and SH rats were exposed to filtered air or TS for 8 weeks, then their proximal femurs were extracted for micro-computed tomography (micro-CT) assessment, histological and immune-histological examinations to quantify the adverse influence of TS exposure on the bone mass and density, as well as bone architecture.

RESULTS

We found that TS exposure not only induced significant decreases in bone mineral density (BMD), bone volume (BV), cortical and trabecular thickness (Ct.Th and Tb.Th), trabecular surface area (Tb.Ar), expression of hypoxia-inducible factor-1α (HIF-1α) in the trabecular marrow, delayed ossification of cartilage, as well as statistical increases in trabecular separation (Tb.SP) and the number of trabecular marrow adipocytes in both WKY and SH rats, but also exacerbated multiple features of osteoporosis exhibited in SH rats, including decreased BMD, Ct.Th, Tb.Ar, HIF-1α expression, delayed cartilage ossification, and increased Tb.SP.

CONCLUSIONS

Our results show that TS exposure can reduce bone mass and impair bone architecture and exacerbate multiple features of osteoporosis exhibited in SH rats.

Initiation of antihypertensive monotherapy and incident fractures among Medicare beneficiaries

BACKGROUND

Research suggests antihypertensive medications are associated with fractures in older adults, however results are inconsistent and few have examined how the association varies over time. We sought to examine the association between antihypertensive class and incident non-vertebral fractures among older adults initiating monotherapy according to time since initiation.

METHODS

We used a new-user cohort design to identify Medicare beneficiaries (≥ 65 years of age) initiating antihypertensive monotherapy during 2008-2011 using a 20% random sample of Fee-For-Service Medicare beneficiaries enrolled in parts A (inpatient services), B (outpatient services), and D (prescription medication) coverage. Starting the day after the initial antihypertensive prescription, we followed beneficiaries for incident non-vertebral fractures. We used multinomial logistic regression models to estimate propensity scores for initiating each antihypertensive drug class. Using these propensity scores, we weighted beneficiaries to achieve the same baseline covariate distribution as beneficiaries initiating with angiotensin-converting enzyme inhibitors. Lastly, we used weighted Cox proportional hazard models to estimate hazard ratios (HRs) of having an incident fractures according to antihypertensive class and time since initiation.

RESULTS

During 2008-2011, 122,629 Medicare beneficiaries initiated antihypertensive monotherapy (mean age 75, 61% women, 86% White). Fracture rates varied according to days since initiation and antihypertensive class. Beneficiaries initiating with thiazides had the highest fracture rate in the first 14 days following initiation (438 per 10,000 person-years, 95% confidence interval (CI): 294-628; HR: 1.40, 0.78-2.52). However, beneficiaries initiating with calcium channel blockers had the highest fracture rate during the 15-365 days after initiation (435 per 10,000 person-years, 95% CI: 404-468; HR: 1.11, 1.00-1.24). Beneficiaries initiating with angiotensin-receptor blockers had the lowest fracture rates during the initial 14 days (333 per 10,000 person-years, 190-546, HR: 0.92, 0.49-1.75) and during 15-365 days after initiation (321 per 10,000 person-years, 287-358, HR: 0.96, 0.84-1.09).

CONCLUSION

The association between antihypertensives and fractures varied according to class and time since initiation. Results suggest that when deciding upon antihypertensive therapy, clinicians may want to consider possible fracture risks when choosing between antihypertensive drug classes.