Insulin-like growth factors (IGF) I and II utilize different calcium signaling pathways in a primary human parathyroid cell culture model

The association between blood nickel level and handgrip strength in patients undergoing maintenance hemodialysis

BACKGROUND

Progressive loss of peripheral muscle strength is highly pronounced in patients receiving maintenance hemodialysis (MHD), of which the pathological mechanism tends to be multifactorial. Plasma nickel was reportedly correlated with muscular strength in non-dialysis patients. However, scarce is known regarding the association between blood nickel level and handgrip strength among the patients undergoing MHD.

METHODS

This cross-sectional study included patients undergoing MHD at our center in October 2021. Blood samples were collected before the hemodialysis sessions. Nickel level was measured using inductively coupled plasma mass spectrometry. Eligible patients were stratified into three groups by the blood nickel level: tertile 1 (≥ 5.2 ug/L); tertile 2 (< 5.2 ug/L and ≥ 4.5 ug/L); and tertile 3 (< 4.5 ug/L). Handgrip strength measurement was used to evaluate the muscle status. Spearman's analyses and multivariable linear regression analyses were performed to study the relationship between blood nickel level and handgrip strength.

RESULTS

A total of 236 patients were enrolled, with an average age of 55.51 ± 14.27 years and a median dialysis vintage of 83 (IQR: 48-125) months. Patients in group with a higher blood nickel level (tertile 1) tended to be female, had longer dialysis vintage and higher Kt/V, but lower BMI, serum creatinine, hemoglobin, and handgrip strength level (all p < 0.05). After adjustment for confounding factors in multivariable models, for every 1ug/L increase in nickel level, the patient's handgrip strength decreases by 2.81 kg (β: - 2.810, 95% confidence interval: - 5.036 to - 0.584, p = 0.014). Restricted cubic spline confirmed the relationship was nearly linear.

CONCLUSIONS

Our study highlighted that blood nickel level was related to handgrip strength in patients undergoing MHD. Prospective studies with larger sample sizes are still needed to confirm the result.

Energy Metabolism and Ketogenic Diets: What about the Skeletal Health? A Narrative Review and a Prospective Vision for Planning Clinical Trials on this Issue

The existence of a common mesenchymal cell progenitor shared by bone, skeletal muscle, and adipocytes cell progenitors, makes the role of the skeleton in energy metabolism no longer surprising. Thus, bone fragility could also be seen as a consequence of a “poor” quality in nutrition. Ketogenic diet was originally proven to be effective in epilepsy, and long-term follow-up studies on epileptic children undergoing a ketogenic diet reported an increased incidence of bone fractures and decreased bone mineral density. However, the causes of such negative impacts on bone health have to be better defined. In these subjects, the concomitant use of antiepileptic drugs and the reduced mobilization may partly explain the negative effects on bone health, but little is known about the effects of diet itself, and/or generic alterations in vitamin D and/or impaired growth factor production. Despite these remarks, clinical studies were adequately designed to investigate bone health are scarce and bone health related aspects are not included among the various metabolic pathologies positively influenced by ketogenic diets. Here, we provide not only a narrative review on this issue, but also practical advice to design and implement clinical studies on ketogenic nutritional regimens and bone health outcomes. Perspectives on ketogenic regimens, microbiota, microRNAs, and bone health are also included.

Secretion of parathyroid hormone may be coupled to insulin secretion in humans

OBJECTIVE

Parathyroid hormone (PTH) is a key hormone in regulation of calcium homeostasis and its secretion is regulated by calcium. Secretion of PTH is attenuated during intake of nutrients, but the underlying mechanism(s) are unknown. We hypothesized that insulin acts as an acute regulator of PTH secretion.

METHODS

Intact PTH was measured in plasma from patients with T1D and matched healthy individuals during 4-h oral glucose tolerance tests (OGTT) and isoglycemic i.v. glucose infusions on 2 separate days. In addition, expression of insulin receptors on surgical specimens of parathyroid glands was assessed by immunochemistry (IHC) and quantitative PCR (qPCR).

RESULTS

The inhibition of PTH secretion was more pronounced in healthy individuals compared to patients with T1D during an OGTT (decrementalAUC0-240min: -5256 ± 3954 min × ng/L and -2408 ± 1435 min × ng/L, P = 0.030). Insulin levels correlated significantly and inversely with PTH levels, also after adjusting for levels of several gut hormones and BMI (P = 0.002). Expression of insulin receptors in human parathyroid glands was detected by both IHC and qPCR.

CONCLUSION

Our study suggests that insulin may act as an acute regulator of PTH secretion in humans.

Activation of TRPA1 Channel by Antibacterial Agent Triclosan Induces VEGF Secretion in Human Prostate Cancer Stromal Cells

Accruing evidence indicates that exposure to environmental compounds may adversely affect human health and promote carcinogenesis. Triclosan (TCS), an antimicrobial agent widely used as a preservative in personal care products, has been shown to act as an endocrine disruptor in hormone-dependent tissues. Here, we demonstrate a new molecular mechanism by which TCS stimulates the secretion by human prostate cancer stromal cells of vascular endothelial growth factor (VEGF), a factor known to promote tumor growth. This mechanism involves an increase in intracellular calcium levels due to the direct activation of a membrane ion channel. Using calcium imaging and electrophysiology techniques, we show for the first time that environmentally relevant concentrations of TCS activate a cation channel of the TRP family, TRPA1 (Transient Receptor Potential Ankirin 1), in primary cultured human prostate cancer stromal cells. The TCS-induced TRPA1 activation increased basal calcium in stromal cells and stimulated the secretion of VEGF and epithelial cells proliferation. Interestingly, immunofluorescence labeling performed on formalin-fixed paraffin-embedded prostate tissues showed an exclusive expression of the TRPA1 channel in prostate cancer stromal cells. Our data demonstrate an impact of the environmental factor TCS on the tumor microenvironment interactions, by activating a tumor stroma-specific TRPA1 ion channel. Cancer Prev Res; 10(3); 177-87. ©2017 AACR.

The association between circulating IGF1, IGFBP3, and calcium: results from NHANES III

BACKGROUND

Despite mounting evidence linking both calcium and IGF1, there is a lack of studies investigating any association between circulating levels of IGF1 and serum calcium.

METHODS

Serum calcium, IGF1, and IGF-binding protein 3 (IGFBP3) were measured for 5368 participants in NHANES III. We calculated multivariable-adjusted geometric means of serum concentrations of IGF1, IGFBP3, and IGF1/IGFBP3 by categories of calcium (lowest 5% (<1.16 mmol/l), mid 90%, and top 5% (≥1.31 mmol/l)). We also performed stratified analyses by sex, age, ethnicity, BMI, serum levels of vitamin D, and bone mineral density (BMD).

RESULTS

Overall, we found that circulating calcium was positively associated with circulating levels of IGF1 and IGFBP3, but not their molar ratio (i.e., geometric mean of IGF1 by increasing calcium categories: 237.63, 246.51, and 264.22 ng/nl; Ptrend: 0.43; Pfirst vs third category: 0.01). In particular, these associations were observed in women, people aged <60, non-Hispanic whites, those with vitamin D levels above the mean, and those with low BMD. In contrast, there was an inverse association with the molar ratio for those with BMI ≥30 kg/m(2).

CONCLUSION

We found an overall positive association between circulating levels of IGF1 and IGFBP3 and serum calcium. However, stratification by potential effect-modifiers did not support all suggested hypotheses. Our findings provide more insight into the interplay between calcium and IGF1, which in the future can be investigated in larger observational studies allowing for additional stratifications based on a combination of the different effect-modifiers investigated here.

Igf-I influences everolimus activity in medullary thyroid carcinoma

CONTEXT

Medullary thyroid carcinoma (MTC) is a rare tumor originating from thyroid parafollicular C cells. It has been previously demonstrated that insulin-like growth factor I (IGF-I) protects MTC from the effects of antiproliferative drugs. Everolimus, an mTOR inhibitor, has shown potent antiproliferative effects in a human MTC cell line, TT, and in two human MTC primary cultures.

OBJECTIVE

To verify whether IGF-I may influence the effects of everolimus in a group of human MTC primary cultures.

DESIGN

We collected 18 MTCs that were dispersed in primary cultures, treated without or with 10 nM-1 μM everolimus and/or 50 nM IGF-I. Cell viability was evaluated after 48 h, and calcitonin (CT) secretion was assessed after a 6 h incubation. IGF-I receptor downstream signaling protein expression profile was also investigated.

RESULTS

Everolimus significantly reduced cell viability in eight MTC [by ~20%; P < 0.01 vs. control; everolimus-responders (E-R) MTCs], while cell viability did not change in 10 MTCs [everolimus-non-responders (E-NR) MTCs]. In E-R MTCs, IGF-I blocked the antiproliferative effects of everolimus that did not affect CT secretion, but blocked the stimulatory effects of IGF-I on this parameter. IGF-I receptor downstream signaling proteins were expressed at higher levels in E-NR MTC as compared to E-R MTCs.

CONCLUSION

IGF-I protects a subset of MTC primary cultures from the antiproliferative effects of everolimus and stimulates CT secretion by an mTOR mediated pathway that, in turn, may represent a therapeutic target in the treatment of aggressive MTCs.

Juxtaglomerular cell CaSR stimulation decreases renin release via activation of the PLC/IP(3) pathway and the ryanodine receptor

The calcium-sensing receptor (CaSR) is a G-coupled protein expressed in renal juxtaglomerular (JG) cells. Its activation stimulates calcium-mediated decreases in cAMP content and inhibits renin release. The postreceptor pathway for the CaSR in JG cells is unknown. In parathyroids, CaSR acts through G(q) and/or G(i). Activation of G(q) stimulates phospholipase C (PLC), and inositol 1,4,5-trisphosphate (IP(3)), releasing calcium from intracellular stores. G(i) stimulation inhibits cAMP formation. In afferent arterioles, the ryanodine receptor (RyR) enhances release of stored calcium. We hypothesized JG cell CaSR activation inhibits renin via the PLC/IP(3) and also RyR activation, increasing intracellular calcium, suppressing cAMP formation, and inhibiting renin release. Renin release from primary cultures of isolated mouse JG cells (n = 10) was measured. The CaSR agonist cinacalcet decreased renin release 56 ± 7% of control (P < 0.001), while the PLC inhibitor U73122 reversed cinacalcet inhibition of renin (104 ± 11% of control). The IP(3) inhibitor 2-APB also reversed inhibition of renin from 56 ± 6 to 104 ± 11% of control (P < 0.001). JG cells were positively labeled for RyR, and blocking RyR reversed CaSR-mediated inhibition of renin from 61 ± 8 to 118 ± 22% of control (P < 0.01). Combining inhibition of IP(3) and RyR was not additive. G(i) inhibition with pertussis toxin plus cinacalcet did not reverse renin inhibition (65 ± 12 to 41 ± 8% of control, P < 0.001). We conclude stimulating JG cell CaSR activates G(q), initiating the PLC/IP(3) pathway, activating RyR, increasing intracellular calcium, and resulting in calcium-mediated renin inhibition.

Protein kinase C: a putative new target for the control of human medullary thyroid carcinoma cell proliferation in vitro

We investigate the role of protein kinase C (PKC) in the control of medullary thyroid carcinoma (MTC) cell proliferation by a PKC inhibitor, Enzastaurin, in human MTC primary cultures and in the TT cell line. We found that PKC inhibition reduces cell proliferation by inducing caspase-mediated apoptosis and blocks the stimulatory effect of IGF-I on calcitonin secretion. Enzastaurin reduces PKCβII (Thr500) phosphorylation, indicating a direct involvement of this isoform as well as the phosphorylated levels of Akt (Ser 473) and glycogen synthase kinase (Ser9), PKC pathway downstream targets and pharmacodynamic markers for PKC inhibition. PKCβII and PKCδ enzyme isoforms expression and localization were investigated. These data indicate that in vitro PKC is involved in the control of human MTC proliferation and survival by modulating apoptosis, with a mechanism that implicates PKCβII inhibition and translocation in different subcellular compartments. Targeting PKC may represent a useful therapeutic approach for controlling MTC proliferation.

Severe obesity is associated with symptomatic presentation, higher parathyroid hormone levels, and increased gland weight in primary hyperparathyroidism

CONTEXT

A relationship between primary hyperparathyroidism (PHPT) and obesity has been observed but is incompletely understood. Furthermore, obesity has been associated with vitamin D deficiency, suggesting that the three conditions may be linked.

OBJECTIVE

We hypothesized that PHPT in morbidly obese patients is more severe and that the difference may be explained by vitamin D deficiency. DESIGN AND SETTING, PARTICIPANTS, AND OUTCOME MEASURES: Records of 196 patients with surgically treated PHPT and known body mass index (BMI) were examined. Patients were stratified into three BMI groups: group I (nonobese), BMI < 25 kg/m(2) (n = 54); group II (non-severely obese), BMI 25-34 kg/m(2) (n = 102); and group III (severely obese), BMI 35 kg/m(2) or greater (n = 40).

RESULTS

Preoperative PTH levels were higher in group ΙΙΙ compared with group Ι (181 ± 153 vs. 140 ± 80 pg/ml, p = 0.04). Group III patients had larger tumors on average compared with group I (1.8 ± 1.5 vs. 1.04 ± 1.5 g, P = 0.0002). In group III, BMI positively correlated with parathyroid tumor weight (r = 0.5, P = 0.002). Postoperative PTH was higher in group III compared with group Ι (61 ± 41 vs. 44 ± 28 pg/ml, P = 0.02). There was higher frequency of depression, musculoskeletal symptoms, weakness, and gastroesophageal reflux disease in group III patients.

CONCLUSIONS

BMI positively correlated with parathyroid tumor weight independent of vitamin D. Severely obese patients have larger parathyroid tumor weight, higher pre- and postoperative PTH, and greater symptoms.

Role of growth factors on human parathyroid adenoma cell proliferation

INTRODUCTION

Primary hyperparathyroidism (pHPT) is caused by a single monoclonal adenoma in more than 80% of patients. Biomolecular mechanisms causing pHPT are still not completely known, even if a great amount of studies have been developed recently, mainly regarding angiogenesis and growth factors. Among the latter, insulin-like growth factor 1 (IGF-1), basic fibroblastic growth factor (bFGF), vascular endothelial growth factor (VEGF), and transforming growth factor beta 1 (TGF-beta1) and their effects have been extensively evaluated in different kinds of endocrine disease.

METHODS

Parathyroid cell cultures were prepared from six human adenomatous parathyroid glands that were surgically removed. After 7 days of culture, the cells were refed with DMEM supplemented with 2% FCS alone (control group), or containing hrTGFbeta1, or hrIGF-I, or hrbFGF, or hrVEGF. Then, after 48-hour incubation, cell count was performed by a particle count and size analyzer, and prevalence of cell cycle was analyzed by using a flow cytometer.

RESULTS

Cell count (x10000) in the control group was 3.73 +/- 0.32. Low-dose TGF-beta1 stimulation resulted in 5.25 +/- 0.38 cells, and high-dose TGF-beta1 stimulation resulted in 2.35 +/- 0.37 cells. IGF-1 stimulation resulted in 5.4 +/- 0.65 cells, bFGF stimulation in 5.68 +/- 0.86 cells, and VEGF stimulation resulted in 6.03 +/- 1.03 cells. Statistical analysis revealed significant differences in the control group compared with the growth factor-stimulated groups. Cytometry showed different results in the percentage of cells in S-phase, in particular 22.65 +/- 4.98% of IGF-1-stimulated cells were found in S-phase compared with 7.55 +/- 3.2% of control group cells (p < 0.0001).

CONCLUSIONS

Growth factors seem to play an important role in parathyroid adenoma cell proliferation; IGF-1, bFGF, VEGF, and low-dose TGF-beta1 promote cell proliferation, whereas high-dose TGF-beta1 inhibits these phenomena.