Schimke immunoosseous dysplasia and management considerations for vascular risks

Schimke immunoosseous dysplasia (SIOD) is a multisystemic condition characterized by early arteriosclerosis and progressive renal insufficiency, among other features. Many SIOD patients have severe, migraine-like headaches, transient neurologic attacks, or cerebral ischemic events. Cerebral events could be exacerbated or precipitated by hypertension, and it is unclear how these are related to arteriosclerotic changes as dyslipidemia is also a feature of SIOD. The correlation between hypercholesterolemia and cardiovascular risk in SIOD is unclear. Also, the etiology and management of headaches is not well characterized. Here we report our clinical observations in the management of SIOD in a patient who was diagnosed in school age despite early signs and symptoms. We describe biallelic variants, including a previously unreported c.1931G>A (p.Arg644Gln) variant in SMARCAL1. We specifically investigated whether migraine-like headaches and progressive nephropathy may be related to blood pressure dysregulation. We found a correlation between tighter blood pressure regulation using ambulatory blood pressure monitoring and a subjective decrease in headache symptoms. We discuss blood pressure medication management in SIOD. We also characterize dyslipidemia relative to atherosclerosis risks and provide new management strategies to consider for optimizing care.

A new familial form of a late-onset, persistent hyperinsulinemic hypoglycemia of infancy caused by a novel mutation in KCNJ11

The ATP-sensitive potassium channel (K_ATP) functions as a metabo-electric transducer in regulating insulin secretion from pancreatic β-cells. The pancreatic K_ATP channel is composed of a pore-forming inwardly-rectifying potassium channel, Kir6.2, and a regulatory subunit, sulphonylurea receptor 1 (SUR1). Loss-of-function mutations in either subunit often lead to the development of persistent hyperinsulinemic hypoglycemia of infancy (PHHI). PHHI is a rare genetic disease and most patients present with immediate onset within the first few days after birth. In this study, we report an unusual form of PHHI, in which the index patient developed hyperinsulinemic hypoglycemia after 1 year of age. The patient failed to respond to routine medication for PHHI and underwent a complete pancreatectomy. Genotyping of the index patient and his immediate family members showed that the patient and other family members with hypoglycemic episodes carried a heterozygous novel mutation in KCNJ11 (C83T), which encodes Kir6.2 (A28V). Electrophysiological and cell biological experiments revealed that A28V hKir6.2 is a dominant-negative, loss-of-function mutation and that K_ATP channels carrying this mutation failed to reach the cell surface. De novo protein structure prediction indicated that this A28V mutation reoriented the ER retention motif located at the C-terminal of the hKir6.2, and this result may explain the trafficking defect caused by this point mutation. Our study is the first report of a novel form of late-onset PHHI that is caused by a dominant mutation in KCNJ11 and exhibits a defect in proper surface expression of Kir6.2.

Sex differences in response to targeted kyphosis specific exercise and posture training in community-dwelling older adults: a randomized controlled trial

Background

Hyperkyphosis, an excessive anterior curvature in the thoracic spine, is associated with reduced health status in older adults. Hyperkyphosis is highly prevalent, more common in older women than men. There is no standard intervention to reduce age-related hyperkyphosis. Sex differences in response to a kyphosis-specific exercise intervention are not known.

Methods

We conducted a randomized controlled trial of a targeted kyphosis-specific exercise and postural training program on the primary outcome Cobb angle of kyphosis, and investigated whether the magnitude of change differed between men and women. One hundred twelve participants aged ≥60 years with kyphosis ≥40° were enrolled and randomized to exercise or waitlist control, and 101 participants had analyzable baseline and follow-up radiographs for Cobb angle measurements. A group intervention including 10 participants per group was delivered by a physical therapist, 1-h, twice a week for 3-months. Controls were placed on a waitlist for 3 months before receiving a delayed intervention. Primary outcome was change from baseline to 3-months in Cobb angle measured from standing lateral spine radiographs. Secondary outcomes included change over 3-months in kyphometer-measured kyphosis, physical function and quality of life. Groups were combined for analysis after both received the intervention, and sex differences in response to the intervention were tested with ANOVA.

Results

Participants (60 women, 41 men) were 70.0 (SD = 5.7) years old with mean Cobb angle 55.9 (SD = 12.2) degrees at baseline. The active group had higher baseline modified Physical Performance Test scores than control, p = 0.03. Men had greater baseline kyphometer-measured kyphosis, p = 0.09, and higher bone mineral density (BMD), spine strength, more vertebral fractures and diffuse idiopathic skeletal hyperostosis (DISH) than women, p ≤ 0.01. There was no statistically significant difference between groups in change in Cobb at 3-months, p = 0.09, however change in kyphometer-measured kyphosis differed by 4.8 (95% CI:-6.8,-2.7) degrees, p < 0.001, favoring the active group. There were no differences between men and women in change in either kyphosis measurement after intervention, p > 0.1.

Conclusions

A 3-month targeted spine strengthening exercise and posture training program reduced kyphometer-measured, but not radiographic-measured kyphosis. Despite sex differences in baseline kyphosis, BMD, spine strength, fractures and DISH, sex did not affect treatment response.

Trial registration

ClinicalTrials.gov Identifier: NCT01766674.

Targeted spine strengthening exercise and posture training program to reduce hyperkyphosis in older adults: results from the study of hyperkyphosis, exercise, and function (SHEAF) randomized controlled trial

A 6-month randomized controlled trial of spine-strengthening exercise and posture training reduced both radiographic and clinical measures of kyphosis. Participants receiving the intervention improved self-image and satisfaction with their appearance. Results suggest that spine-strengthening exercise and postural training may be an effective treatment option for older adults with hyperkyphosis.

INTRODUCTION

The purpose of the present study is to determine in a randomized controlled trial whether spine-strengthening exercises improve Cobb angle of kyphosis in community-dwelling older adults.

METHODS

We recruited adults ≥60 years with kyphosis ≥40° and enrolled 99 participants (71 women, 28 men), mean age 70.6 ± 0.6 years, range 60-88, with baseline Cobb angle 57.4 ± 12.5°. The intervention included group spine-strengthening exercise and postural training, delivered by a physical therapist, 1-h, three times weekly for 6 months. Controls received four group health education meetings. The primary outcome was change in the gold standard Cobb angle of kyphosis measured from standing lateral spine radiographs. Secondary outcomes included change in kyphometer-measured kyphosis, physical function (modified Physical Performance Test, gait speed, Timed Up and Go, Timed Loaded Standing, 6-Min Walk), and health-related quality of life (HRQoL) (PROMIS global health and physical function indexes, SRS-30 self-image domain). ANCOVA was used to assess treatment effects on change from baseline to 6 months in all outcomes.

RESULTS

There was a -3.0° (95% CI -5.2, -0.8) between-group difference in change in Cobb angle, p = 0.009, favoring the intervention and approximating the magnitude of change from an incident vertebral fracture. Kyphometer-measured kyphosis (p = 0.03) and SRS-30 self-esteem (p < 0.001) showed favorable between-group differences in change, with no group differences in physical function or additional HRQoL outcomes, p > 0.05.

CONCLUSIONS

Spine-strengthening exercise and posture training over 6 months reduced kyphosis compared to control. Our randomized controlled trial results suggest that a targeted kyphosis-specific exercise program may be an effective treatment option for older adults with hyperkyphosis.

TRIAL REGISTRATION NUMBER AND NAME OF TRIAL REGISTER

ClinicalTrials.gov; identifier NCT01751685.

Regulation of Ligand and Shear Stress-induced Insulin-like Growth Factor 1 (IGF1) Signaling by the Integrin Pathway

Mechanical loading of the skeleton, as achieved during daily movement and exercise, preserves bone mass and stimulates bone formation, whereas skeletal unloading from prolonged immobilization leads to bone loss. A functional interplay between the insulin-like growth factor 1 receptor (IGF1R), a major player in skeletal development, and integrins, mechanosensors, is thought to regulate the anabolic response of osteogenic cells to mechanical load. The mechanistic basis for this cross-talk is unclear. Here we report that integrin signaling regulates activation of IGF1R and downstream targets in response to both IGF1 and a mechanical stimulus. In addition, integrins potentiate responsiveness of IGF1R to IGF1 and mechanical forces. We demonstrate that integrin-associated kinases, Rous sarcoma oncogene (SRC) and focal adhesion kinase (FAK), display distinct actions on IGF1 signaling; FAK regulates IGF1R activation and its downstream effectors, AKT and ERK, whereas SRC controls signaling downstream of IGF1R. These findings linked to our observation that IGF1 assembles the formation of a heterocomplex between IGF1R and integrin β3 subunit indicate that the regulation of IGF1 signaling by integrins proceeds by direct receptor-receptor interaction as a possible means to translate biomechanical forces into osteoanabolic signals.

Quantitation of CYP24A1 enzymatic activity with a simple two-hybrid system

CONTEXT

Mutations of the CYP24A1 gene encoding the 24-hydroxylase (24OHase) that inactivates metabolites of vitamin D can cause hypercalcemia in infants and adults; in vitro assays of 24OHase activity have been difficult.

OBJECTIVE

We sought an alternative assay to characterize a CYP24A1 mutation in a young adult with bilateral nephrolithiasis and hypercalcemia associated with ingestion of excess vitamin D supplements and robust dairy intake for 5 years.

METHODS

CYP24A1 exons were sequenced from leukocyte DNA. Wild-type and mutant CYP24A1 cDNAs were expressed in JEG-3 cells, and 24OHase activity was assayed by a two-hybrid system.

RESULTS

The CYP24A1 missense mutation L409S was found on only one allele; no other mutation was found in exons or in at least 30 bp of each intron/exon junction. Based on assays of endogenous 24OHase activity and of activity from a transiently transfected CYP24A1 cDNA expression vector, JEG-3 cells were chosen over HepG2, Y1, MA10, and NCI-H295A cells for two-hybrid assays of 24OHase activity. The apparent Michaelis constant, Km(app), was 9.0 ± 2.0 nM for CYP24A1 and 8.6 ± 2.2 nM for its mutant; the apparent maximum velocity, Vmax(app), was 0.71 ± 0.055 d(-1) for the wild type and 0.22 ± 0.026 d(-1) for the mutant. As assessed by Vmax/Km, the L409S mutant has 32% of wild-type activity (P = .0012).

CONCLUSIONS

The two-hybrid system in JEG-3 cells provides a simple, sensitive, quantitative assay of 24OHase activity. Heterozygous mutation of CYP24A1 may cause hypercalcemia in the setting of excessive vitamin D intake, but it is also possible that the patient had another, unidentified CYP24A1 mutation on the other allele.

Skeletal unloading-induced insulin-like growth factor 1 (IGF-1) nonresponsiveness is not shared by platelet-derived growth factor: the selective role of integrins in IGF-1 signaling

Integrin receptors bind extracellular matrix proteins, and this link between the cell membrane and the surrounding matrix may translate skeletal loading to biologic activity in osteoprogenitor cells. The interaction between integrin and growth factor receptors allows for mechanically induced regulation of growth factor signaling. Skeletal unloading leads to decreased bone formation and osteoblast proliferation that can be explained in part by a failure of insulin-like growth factor 1 (IGF-1) to activate its signaling pathways in unloaded bone. The aim of this study is to determine whether unloading-induced resistance is specific for IGF-1 or common to other skeletal growth factors, and to examine the regulatory role of integrins in IGF-1 signaling. Bone marrow osteoprogenitor (BMOp) cells were isolated from control or hindlimb suspended rats. Unloaded BMOp cells treated with IGF-1 failed to respond with increased proliferation, receptor phosphorylation, or signaling activation in the setting of intact ligand binding, whereas the platelet-derived growth factor (PDGF) response was fully intact. Pretreatment of control BMOp cells with an integrin inhibitor, echistatin, failed to disrupt PDGF signaling but blocked IGF-1 signaling. Recovery of IGF-1 signaling in unloaded BMOp cells followed the recovery of marked reduction in integrin expression induced by skeletal unloading. Selective targeting of integrin subunits with siRNA oligonucleotides revealed that integrin β1 and β3 are required for normal IGF-1 receptor phosphorylation. We conclude that integrins, in particular integrin β3, are regulators of IGF-1, but not PDGF, signaling in osteoblasts, suggesting that PDGF could be considered for investigation in prevention and/or treatment of bone loss during immobilization and other forms of skeletal unloading.

Role of IGF-I signaling in regulating osteoclastogenesis

We showed that IGF-I deficiency impaired osteoclastogenesis directly and/or indirectly by altering the interaction between stromal/osteoblastic cells and osteoclast precursors, reducing RANKL and M-CSF production. These changes lead to impaired bone resorption, resulting in high BV/TV in IGF-I null mice.

INTRODUCTION

Although IGF-I has been clearly identified as an important growth factor in regulating osteoblast function, information regarding its role in osteoclastogenesis is limited. Our study was designed to analyze the role of IGF-I in modulating osteoclastogenesis using IGF-I knockout mice (IGF-I(-/-)).

MATERIALS AND METHODS

Trabecular bone volume (BV/TV), osteoclast number, and morphology of IGF-I(-/-) or wildtype mice (IGF-I(+/+)) were evaluated in vivo by histological analysis. Osteoclast precursors from these mice were cultured in the presence of RANKL and macrophage-colony stimulating factor (M-CSF) or co-cultured with stromal/osteoblastic cells from either genotype. Osteoclast formation was assessed by measuring the number of multinucleated TRACP+ cells and pit formation. The mRNA levels of osteoclast regulation markers were determined by quantitative RT-PCR.

RESULTS

In vivo, IGF-I(-/-) mice have higher BV/TV and fewer (76% of IGF-I(+/+)) and smaller osteoclasts with fewer nuclei. In vitro, in the presence of RANKL and M-CSF, osteoclast number (55% of IGF-I(+/+)) and resorptive area (30% of IGF-I(+/+)) in osteoclast precursor cultures from IGF-I(-/-) mice were significantly fewer and smaller than that from the IGF-I(+/+) mice. IGF-I (10 ng/ml) increased the size, number (2.6-fold), and function (resorptive area, 2.7-fold) of osteoclasts in cultures from IGF-I(+/+) mice, with weaker stimulation in cultures from IGF-I(-/-) mice. In co-cultures of IGF-I(-/-) osteoblasts with IGF-I(+/+) osteoclast precursors, or IGF-I(+/+) osteoblasts with IGF-I(-/-) osteoclast precursors, the number of osteoclasts formed was only 11% and 48%, respectively, of that from co-cultures of IGF-I(+/+) osteoblasts and IGF-I(+/+) osteoclast precursors. In the long bones from IGF-I(-/-) mice, mRNA levels of RANKL, RANK, M-CSF, and c-fms were 55%, 33%, 60%, and 35% of that from IGF-I(+/+) mice, respectively.

CONCLUSIONS

Our results indicate that IGF-I regulates osteoclastogenesis by promoting their differentiation. IGF-I is required for maintaining the normal interaction between the osteoblast and osteoclast to support osteoclastogenesis through its regulation of RANKL and RANK expression.

Water vapor-nitrogen absorption at CO(2) laser frequencies

In this paper we report the results of a series of pressure-broadened water vapor absorption measurements at 27 CO(2) laser frequencies between 935 cm(-1) and 1082 cm(-1). Both multiple traversal cell and optoacoustic (spectrophone) techniques were utilized together with an electronically stabilized cw CO(2) laser. Comparison of the results obtained by these two methods shows remarkable agreement, indicating a precision which has not been previously achieved in pressure-broadened studies of water vapor. The data of 10.59 microm substantiate the existence of the large (>200) self-broadening coefficients determined in an earlier study by McCoy. In this work we have treated the case of water vapor in N(2) at a total pressure of 1 atm. We have also studied water vapor in air and will report those results separately.

Effects of oxygen addition on pressure-broadened water-vapor absorption in the 10-microm region

We have measured the monochromatic transmittances of pressure-broadened room-temperature water vapor samples at five laser frequencies of the CO(2) laser in the 10.4-microm band. Three different buffer gases were used. They were pure nitrogen, an 80:20 mixture of nitrogen and oxygen, and a 60:40 mixture of nitrogen and oxygen. The measurements at the five laser lines imply that oxygen is a less efficient broadener than nitrogen. The ratio of the oxygen-broadening coefficient to the nitrogen-broadening coefficient was measured to be 0.75 based on the data at the R(20) laser line. Results of this study demonstrate that pure nitrogen should not be used as a broadener for atmospheric modeling of monochromatic transmittances in the laboratory.

Comparative Studies of Extinction and Backscattering by Aerosols, Fog, and Rain at 10.6 micro and 0.63 micro

Theoretical calculations using continental, fog, and precipitation aerosol size distribution models are presented here for extinction and backscatter coefficients along horizontal propagation paths at sea level. The coefficients are presented for various atmospheric conditions and for wavelengths between 0.34 micro and 10.6 micro. Finally, the theoretical results are confirmed by comparison with outdoor transmission studies at 10.6 micro and 0.63 micro.

Water Vapor Continuum Absorption of Carbon Dioxide Laser Radiation near 10micro

Laboratory measurements using a stabilized CO(2) laser and a 1-km long path absorption cell are presented here for pure water vapor and water vapor-air mixtures. An empirical extinction coefficient equation is presented and used to compute absorption for a variety of atmospheric slant paths. Finally, the laboratory results are confirmed by comparison with outdoor transmission studies over a 1.95-km path.

Atmospheric absorption at the line center of P(20) CO(2) laser radiation

Atmospheric CO(2) absorption at the line center of P(20) CO(2) laser radiation has been calculated at different altitudes by using the relationship 1 - exp(-integral(l)(2)(l)(1) kdl). In this calculation, the absorption caused by water vapor has not been included. The line strength and the half-width at 295 K and 1 atm pressure used are 5.09 x 10(-4) cm(-2) atm -(1) and 0.07 cm -(1) atm (-1), respectively.