Parathyroid hormone 1-84 alters circulating vascular endothelial growth factor levels in hypoparathyroidism

Is there a relationship between hypoparathyroidism and retinal microcirculation?

PURPOSE

To investigate the retinal microvasculature in patients with surgically induced hypoparathyroidism who have no clinical evidence of retinopathy and to compare these data with those of healthy control subjects.

METHODS

Forty patients with a confirmed diagnosis of permanent hypoparathyroidism and no clinical evidence of retinopathy and 37 age- and sex-matched healthy control subjects were included in the study. After complete ophthalmological examination, all patients underwent optical coherence tomography angiography measurement (Optovue Inc., Fremont, California, USA) to assess the foveal avascular zone (FAZ) area; FAZ perimeter; acircularity index of FAZ; foveal density-300; radial peripapillary capillary plexus (RPCP) vessel density; superficial, middle and deep capillary plexus vessel densities (SCP, MCP and DCP). The data from the right eyes of all participants were used for statistical analysis.

RESULTS

The SCP and MCP vessel densities were significantly lower, and the RPCP whole image and peripapillary vessel densities were significantly higher than those in healthy control subjects (p < 0.05 for all). The DCP vessel densities of patients with surgically induced hypoparathyroidism were not significantly different from those of healthy control subjects (p > 0.05 for all). No significant difference was found in the FAZ area, FAZ perimeter, acircularity index of FAZ, foveal density-300 measurements between patients and controls (p > 0.05 for all).

CONCLUSIONS

Reduced retinal vessel density in patients with surgically induced hypoparathyroidism supports the hypothesis that parathyroid hormone is associated with regulation of vascular homeostasis, including macular microcirculation. Increased perfusion in the peripapillary area may suggest an early subclinic effect of hypoparathyroidism.

Effect of parathyroid hormone on cardiac function in rats with cardiomyopathy

The present study investigated the role of parathyroid hormone (PTH) in non-ischemic cardiomyopathy (CM) and its underlying mechanism. A total of 30 Sprague-Dawley male rats were randomly divided into a control group (n=6) and an experimental group (n=24). To induce CM in the rats of the experimental group, 2 mg/kg Adriamycin (ADR) was administered intraperitoneally with 5 equal injections every third day followed by 5 weekly injections resulting in a cumulative dose of 20 mg/kg. Following establishment of the model, rats in the experimental group were subdivided into a PTH-untreated CM group that received daily normal saline subcutaneous injections for 7 days and three treated CM groups that received daily subcutaneous injections of 5, 10, or 20 µg/kg of recombinant PTH for 7 days. Rats in the control group accordingly received intraperitoneal and subcutaneous injections of normal saline. Blood sample analysis revealed that B-type natriuretic peptide (BNP), troponin T, C-reactive protein (CRP), creatinine and phosphorus concentrations were increased in the PTH-untreated CM group compared with that in the control group, whereas PTH and calcium concentrations were decreased. Administration of PTH dose-dependently decreased BNP, CRP, creatinine and phosphorus levels, and increased PTH and calcium levels. Notably, there were significant differences in PTH, BNP, troponin T, CRP, creatinine, calcium, and phosphorus levels among the rats in the five groups (P<0.01). Cardiac ultrasonography results indicated that the left ventricular ejection fraction (LVEF) was significantly decreased in rats treated with ADR compared with the rats from the control group (P<0.01). However, the LVEF gradually recovered with elevated PTH treatment doses. The overall differences of LVEF and left ventricular end-systolic volume in the five experimental groups were statistically significant (P<0.01). Furthermore, there were dose-dependent increases in LV mass and left ventricular end-diastolic volume in PTH-treated rats; however, the differences between any two groups did not reach statistical significance (P>0.05). Immunohistochemical staining and western blot analysis using an anti-PTH polyclonal antibody was performed to evaluate the protein expression levels of PTH in myocardial tissues. The mRNA expression levels of PTH and BNP were measured using reverse transcription-quantitative polymerase chain reaction. The results demonstrated that the mRNA and protein expression levels of PTH in myocardial tissues were significantly decreased in ADR-treated rats compared with the levels in the control group rats. Injection of recombinant PTH significantly increased PTH expression and reduced BNP expression in dose-dependent manners (P<0.05). These findings demonstrated that PTH can improve cardiac function in rats with ADR-induced CM, suggesting a potential therapeutic application for PTH in non-ischemic CM.

The effect of parathyroid hormone (1-84) treatment on serum bone morphogenetic protein 4 and vascular endothelial growth factor in postmenopausal women with established osteoporosis

PURPOSE

To investigate the effect of 18 months' parathyroid hormone 1-84 (PTH 1-84) treatment on serum levels of bone morphogenetic protein 4 (BMP4) and vascular endothelial growth factor (VEGF), in postmenopausal women with established osteoporosis.

METHODS

Thirty-seven postmenopausal women with osteoporosis (mean age 72.9 ± 8.1 years old) and 23 healthy controls (mean age 68.9 ± 9.9 years old) were enrolled. Patients were treated with daily subcutaneous injections of PTH (1-84) 100 mcg for 18 months, plus calcium 1 gr and vitamin D 800 IU per os daily. Blood samples were taken every 6 months during the study.

RESULTS

At baseline, there were no differences considering anthropometric parameters, co-morbidities, current medications used between patients and controls. Mean serum VEGF levels were significantly higher in osteoporotic patients compared to controls (436.7 ± 259.7 vs. 260.3 ± 184.3 pg/ml, p = 0.006), while there were no differences in mean serum values of BMP4 (5.3 ± 1.7 vs. 5.7 ± 1.6 pg/ml, p = 0.40). Serum VEGF levels increased by approximately 20% after 12 months of PTH (1-84) treatment compared to baseline (p = 0.03) and by 22% after 18 months (p = 0.01). A significant increase of 10% in mean serum BMP4 levels was observed after 18 months of PTH (1-84) treatment compared to baseline (p = 0.02). In the control group we found no differences after 18 months compared to baseline in BMP4 (5.7 ± 1.6 vs. 6.0 ± 1.5 pg/ml, p = 0.53) and VEGF (260.3 ± 184.3 vs. 257.4 ± 107.1 pg/ml, p = 0.94).

CONCLUSIONS

PTH (1-84) treatment increased serum levels of VEGF and BMP4 in postmenopausal women with severe osteoporosis.

Mobilisation of haemopoietic stem cells in teriparatide-treated patients

Parathyroid hormone (PTH) is the predominant regulator of calcium/phosphate homeostasis in the human body. Beside this classical function, preclinical and clinical studies indicated a relevant role for PTH in mobilisation of bone marrow-derived cells into peripheral blood. In addition, recombinant PTH (teriparatide) was recently approved for the treatment of severe osteoporosis. Therefore, it was the aim of the present study to investigate the dynamics of haemopoietic stem cells and corresponding in peripheral blood of 13 patients with osteoporosis during treatment with teriparatide. We were able to show that administration of teriparatide is sufficient to mobilise haemopoietic stem cells into the bloodstream accompanied by an alteration of mobilising cytokines. In conclusion, teriparatide might be a useful tool in the context of stem cell mobilisation.