Guidelines for the diagnosis and management of osteoporosis in Poland : Update 2017

In the rapidly ageing society in Poland, osteoporosis is a growing epidemiological problem, and osteoporosis-related fractures are a cause of chronic disability and considerable increase of death risk. It turns out that 80 to 90% of patients suffering from osteoporosis, including osteoporosis accompanied by fractures, do not receive adequate pharmacotherapy. In this paper, a Guideline Working Group of experts from the Multidisciplinary Osteoporosis Forum update the existing Polish guidelines concerning the diagnosis and management of osteoporosis (last revised in 2013), taking account of the latest literature, availability and reimbursement of drugs, and current health care organisation. In the revised guidelines, we still postulate that tasks are divided between primary care doctors (stage I) and specialists in osteoporosis management (stage II). We emphasise the necessity of early initiation of pharmacotherapy and rehabilitation in all patients with low-energy fractures. We recommend that the 10-year fracture risk should be estimated in all patients (including those without fractures) who are over 50 years of age, and that the Polish threshold for therapeutic intervention should be adopted: ≥ 10% for FRAX PL calculator. We add strategies of drug choice and therapy monitoring with imaging, and densitometric and biochemical diagnostics. We define basic guidelines concerning prevention of falls, rehabilitation, and dietary procedures, and elimination of environmental and other fracture risk factors. We point to two vital elements for improving osteoporosis management: 1) strategy of supervision over fractures management - Fracture Liaison Service (FLS), and, optimally, 2) strategies of short-term monitoring of the therapeutic efficacy with the use of biochemical markers.

Impact of vitamin D supplementation during lactation on vitamin D status and body composition of mother-infant pairs: a MAVID randomized controlled trial

OBJECTIVE

The optimal vitamin D intake for nursing women is controversial. Deterioration, at least in bone mass, is reported during lactation. This study evaluated whether vitamin D supplementation during lactation enhances the maternal and infant's vitamin D status, bone mass and body composition.

DESIGN AND METHODS

After term delivery, 174 healthy mothers were randomized to receive 1200 IU/d (800 IU/d+400 IU/d from multivitamins) or 400 IU/d (placebo+400 IU/d from multivitamins) of cholecalciferol for 6 months while breastfeeding. All infants received 400 IU/d of cholecalciferol. Serum 25-hydroxyvitamin D [25(OH)D], iPTH, calcium, urinary calcium, and densitometry were performed in mother-offspring pairs after delivery, and at 3 and 6 months later.

RESULTS

A total of 137 (79%) (n = 70; 1200 IU/d, n = 67; 400 IU/d) completed the study. 25(OH)D was similar in both groups at baseline (13.7 ng/ml vs. 16.1 ng/ml; P = 0.09) and at 3 months (25.7 ng/ml vs. 24.5 ng/ml; P = 0.09), but appeared higher in the 1200 IU/d group at 6 months of supplementation (25.6 ng/ml vs. 23.1 ng/ml; P = 0.009). The prevalence of 25(OH)D <20 ng/ml was comparable between groups at baseline (71% vs. 64%, P = 0.36) but lower in the 1200 IU/d group after 3 months (9% vs. 25%, P = 0.009) and 6 months (14% vs. 30%, P = 0.03). Maternal and infants' iPTH, calciuria, bone mass and body composition as well as infants' 25(OH)D levels were not significantly different between groups during the study. Significant negative correlations were noted between maternal 25(OH)D and fat mass (R =  -0.49, P = 0.00001), android fat mass (R = -0.53, P = 0.00001), and gynoid fat mass (R = -0.43, P = 0.00001) after 6 months of supplementation.

CONCLUSIONS

Vitamin D supplementation at a dose of 400 IU/d was not sufficient to maintain 25(OH)D >20 ng/ml in nursing women, while 1200 IU/d appeared more effective, but had no effect on breastfed offspring vitamin D status, or changes in the bone mass and the body composition observed in both during breastfeeding.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01506557.

Vitamin d status in central europe

Little published information is available regarding epidemiological data on vitamin D status in the large geographical region of Central Europe (CE). We searched the journal literature with regard to 25(OH)D concentrations among community-dwelling or healthy people living in CE. 25(OH)D concentrations varied by age, season, study sample size, and methodological approach [i.e., 25(OH)D assay used]. Concentrations of 25(OH)D in CE appeared lower than 30 ng/mL, and the magnitude of hypovitaminosis D was similar to that reported in Western Europe. While most of the studies reviewed were cross-sectional studies, a longitudinal study was also included to obtain information on seasonal variability. The longitudinal study reported wintertime 25(OH)D values close to 21-23 ng/mL for all studied age groups, with a significant increase of 25(OH)D in August reaching 42 ng/mL for those aged 0-9 years, but only 21 ng/mL for the elderly aged 80-89 years. The decrease in 25(OH)D with respect to age was attributed to decreased time spent in the sun and decreased vitamin D production efficiency. Based on the literature review on vitamin D status in the CE populations, it can be concluded that 25(OH)vitamin D levels are on average below the 30 ng/mL level.

Effect of vitamin D status on pharmacological treatment efficiency: Impact on cost-effective management in medicine

At least 80% of the whole Polish population, including prepubertal children and adolescents, adults and seniors, are vitamin D deficient, defined as 25(OH)D < 50 nmol/L. 83% of Polish newborns start their lives at the state of vitamin D deficiency because 78% of their mothers are also deficient. It was observed that treating patient vitamin D deficiency to vitamin D status serum 25(OH)D) 75-100 nmol/L increased effectiveness of therapies in infectious diseases (chronic hepatitis C, tuberculosis), osteoporosis, multiple sclerosis, epilepsy, Chronic Kidney Diseases and atopic dermatitis. . For these reasons doctors should take special attention to vitamin D status in patients suffering for these diseases properly implementing recent vitamin D recommendation.

Impact of vitamin D supplementation on markers of bone mineral metabolism in term infants

25-Hydroxyvitamin D (25OHD) may influence bone turnover. We compared the dynamics of bone markers in 30 infants on vitamin D supplementation (≅550 IU/day) with different degrees of hypovitaminosis D (25OHD <11 ng/ml - deficiency vs. ≥ 11 <20 ng/ml - insufficiency). Baseline and follow-up (after 10 weeks), 25OHD, 1,25-dihydroxyvitamin D (1,25(OH)(2)D), alkaline phosphatase (ALP), PTH, osteocalcin (OC), N-terminal propeptide of type I procollagen (PINP), C-terminal telopeptide of type I collagen (CTX), and amino-terminal propeptide of C-type natriuretic peptide (NT-proCNP) were measured. None of the newborns had craniotabes, hypocalcemia or hyperparathyroidism. The median (Q1;Q3) 25OHD increased from a baseline of 8.45 (7;11.9) ng/ml to 54.6 (34.7;67.3) ng/ml (p<0.001). The baseline 25OHD negatively correlated with total increment of 25OHD (r=-0.54; p=0.002). There were changes in ALP (241 vs. 331 IU; p<0.001), 1,25(OH)(2)D (48 vs. 95.5 pg/ml, p<0.001), OC (88.8 vs. 159.1 ng/ml, p<0.001), PINP (3886 vs. 2409 ng/ml; p<0.001), CTX (1.6 vs. 1.1 ng/ml; p<0.001), and NT-proCNP (75.1 vs. 35.1 pmol/l; p<0.001). Vitamin D deficient infants at baseline, compared to the insufficient group, revealed significantly higher percentage changes for 25OHD (745% vs. 167%, p<0.0001), OC (113% vs. 40%, p<0.05) and 1,25(OH)(2)D (95% vs. 58%, p<0.05).

CONCLUSIONS

Vitamin D supplements had little to no impact on markers of bone turnover in term infants in the first few months of life, with the exception of osteocalcin. Ten weeks of cholecalciferol supplementation at a dose of 550 IU/day led to a marked increase of 25OHD concentration. The magnitude of 25OHD increment was inversely related to vitamin D status at baseline. Irrespective of the severity of vitamin D deficiency, a secondary hyperparathyroidism with elevated iPTH, ALP, phosphaturia or hypophosphatemia was not observed in the studied neonates.

Bone metabolism in cholestatic children before and after living-related liver transplantation--a long-term prospective study

Bone disorders are common in children with end-stage liver diseases, especially those associated with cholestasis. Abnormal hepatocyte function, disordered vitamin D metabolism and calcium-phosphorous homeostasis, malnutrition, and immunosuppressive treatment are potential risk factors of bone tissue pathology before and after transplantation. The aim of the study was to analyze the long-term effect of successful living-related liver transplantation (LRLTx) on skeletal status and bone metabolism in cholestatic children. Eighteen cholestatic children (1.4±0.5yr old; 12 females [F]/6 males [M]) qualified for LRLTx were analyzed; 16 (5F/11M) of them participated in long-term observation (V4). Serum levels of osteocalcin (OC), procollagen type 1 N-terminal propeptide (P1NP), cross-linked telopeptide of type 1 collagen (CTx), insulin-like growth factor I (IGF-I), IGF-I binding protein 3 (IGFBP-3), parathyroid hormone (PTH), 25-hydroxyvitamin D (25(OH)D), and 1,25-dihydroxyvitamin D (1,25(OH)(2)D) were assayed before (V0) and 6mo (V1), 12mo (V2), 18mo (V3), and 4.4yr (V4) after LRLTx. Total body bone mineral content (TBBMC) and total body bone mineral density (TBBMD) were measured by dual-energy X-ray absorptiometry (DXA) at the same pattern. Before LRLTx, the OC, P1NP, CTx, IGF-I, and IGFBP-3 levels as well as TBBMC and TBBMD were decreased compared with age-matched control group. The mean serum levels of 25(OH)D and 1,25(OH)(2)D were within reference ranges from V0 to V4. After LRLTx, the OC, P1NP, CTx, IGF-I, and IGFBP-3 as well as TBBMC and TBBMD reached the age-matched reference values. At V4, the level of P1NP decreased below and the PTH increased above the reference range that coincided with reduced Z-scores of both TBBMC (-1.11±1.24) and TBBMD (-1.00±1.19). P1NP and CTx, both measured at V3, correlated with IGF-I at V2 (R=0.86, p=0.014 and R=0.78, p=0.021, respectively) and PTH at V3 for P1NP and V1 for CTx (R=0.64, p=0.048 and R=0.54, p=0.038, respectively). The TBBMC changes between V0 and V4 correlated with IGF-I (R=0.68, p=0.015) and 1,25(OH)(2)D (R=0.54, p=0.025), both assayed at V1. The change of TBBMC Z-scores between V0 and V4 correlated with P1NP at V1 (R=0.69, p=0.002). The TBBMD changes between V0 and V4 correlated with CTx at V1 (R=0.54, p=0.027) and P1NP change between V0 and V1 (R=0.51, p=0.038). In short-term observation, successful LRLTx led to bone metabolism normalization triggered by probable anabolic action of IGF-I and PTH and manifested by TBBMC and TBBMD increases. In long-term horizon, moderately impaired DXA assessed bone status coincided with disturbances in bone metabolism. Bone metabolism markers, especially P1NP and CTx, appeared to be good predictors of changes in bone status evaluated by DXA.

[Pathologies of calcium-phosphate homeostasis]

The colossal progress in understanding of vitamin D and phosphate metabolism introduces new perspectives in chronic kidney disease (CKD) therapy. Increasing demand for phosphate excretion per nephron triggers the vicious cycle that leads to increase in FGF-23 and PTH and decrease in vitamin D and Klotho. Restriction of dietary phosphate intake (low phosphate diet) and administration of phosphate binder can be regarded as the most important interventions in this case. Because the vicious cycle is likely activated long before hyperphosphatemia occurs during CKD progression, phosphate restriction would have been more effective if started before serum phosphate levels increased, perhaps as soon as serum FGF-23 levels rose. Phosphate restriction alleviates phosphate overload per nephron and can disrupt the vicious cycle: phosphate restriction can reduce serum FGF-23 levels and increase vitamin D, which in turn increase Klotho expression in kidney and parathyroid glands. Inhibitors of rennin-angiotensin system (rosiglitazone, angiotensin-converting enzyme inhibitors) and proper vitamin D supplementation may also up-regulate Klotho expression. Increased Klotho in the kidney may improve FGF-23 sensitivity, which further reduce the amount of FGF-23 required for excreting a given amount of phosphate. Increased Klotho in parathyroid may improve the ability of FGF-23 to suppress PTH. Proper supplementation with vitamin D increase the concentration of substrate for local 1,25(OH)2D synthesis 25(OH)D, which directly suppress PTH, increase Klotho, and decrease FGF-23 by proanabolic action on bone. Improving vitamin D status by inhibition of CYP24A is also under evaluation, as well as antibodies against FGF-23, as modern therapies in CKD.

Effect of sex, age, and anthropometric parameters on the size and shape of vertebrae in densitometric morphometry: results of the EPOLOS study

INTRODUCTION

Morphometric densitometry (morphometric X-ray absorptiometry - MXA) allows to identify vertebral fractures, based on the objective measurement of vertebral dimensions.

OBJECTIVES

The aim of the study was to assess the effect of sex, age, height, and body mass index (BMI) on selected parameters of vertebral size and shape measured by MXA.

PATIENTS AND METHODS

A random study sample comprised 829 patients (520 women and 309 men) aged 20 to 79 years, none of whom had been previously treated for osteoporosis. Lateral densitometric scans of the thoracic-lumbar spine (T4-L4) were performed using a fan-beam densitometer. Anterior (Ha), central (Hc), and posterior (Hp) vertebral heights were determined.

RESULTS

The analysis included 9632 vertebrae. Higher values of Ha, Hc, and Hp were observed in men (P <0.001). The Ha/Hp ratio from T7 to L3 was lower in men compared with women (P <0.05). The Hc/Hp ratio was lower in T12 to L3 vertebrae in men (P <0.05). Wedging was significantly greater in men in thoracic vertebrae, and significantly lower in L3 and L4 (P <0.05). Concavity was similar in men and women in thoracic vertebrae from T5 to T10. We observed weak and moderate negative correlations between age and vertebral heights, Ha/Hp and Hc/Hp (P <0.001), and a moderate positive correlation between body height and vertebral heights (P <0.001). There were no statistically significant correlations between the body mass index and the remaining variables.

CONCLUSIONS

Morphometric parameters of vertebrae vary depending on sex and age, which has to be considered when choosing reference groups. Knowledge about the differences in vertebral size and shape may prevent diagnostic errors and bias.

[Recommendations of prophylaxis of vitamin D deficiency in Poland (2009)]

Adequate vitamin D intake and its status as well outdoor physical activity are important not only for normal bone development and Ca-P metabolism, but for optimal function of many organs and tissues throughout the body. Due to documented changes in dietary habits and physical activity level, both observed in growing children and adults, the prevalence of vitamin D insufficiency is continuously increasing. National Consultants and experts in this field established the Polish recommendations for prophylactic vitamin D supplementation in infants, toddlers, children and adolescents as well as in adults, including pregnant and lactating women based on current literature review. Taking into consideration pleyotropic vitamin D action and safety aspects serum 25-hydroxyvitamin D (25-OHD) level of 20-60 ng/ml (50-750 nmol/l) in children and 30-80 ng/ml (75-200 nmol/I) in adults is considered as optimal. Sunlight exposure inducing vitamin D production in the skin is main endogen source of vitamin D in the body but sunscreens may reduce skin synthesis by 90%. In Poland, skin synthesis is effective only from April to September so other sources of vitamin D such as diet and supplements play an important role. All newborns should be supplemented with 400 IU/d of vitamin D beginning from the first few days of life and continue during infancy. In formula fed infants vitamin D intake from the diet should be taken into account. In preterm infants higher total vitamin D intake (400-800 IU/day) is recommended till 40 weeks post conception. Total vitamin D intake in children and adolescents required from all sources (diet and/or supplements) should be 400 IU/d between October and March and throughout the whole year in case of inadequate vitamin D skin synthesis during the summer months. In overweight/obese children supplementation with higher dosage of vitamin D up to 800-1000 IU/d should be considered. Adults require 800-1000 IU/d of vitamin D. In pregnant and lactating women such supplementation is recommended in case of inadequate intake from diet and/or skin synthesis supplementation. Monitoring of serum 25-OHD level to define optimal dosage should be considered.

[Prophylaxis of vitamin D deficiency--Polish recommendation 2009]

Adequate vitamin D intake and its status are important not only for bone health and Ca-P metabolism, but for optimal function of many organs and tissues throughout the body. Due to documented changes in dietary habits and physical activity level, both observed in growing children and adults, the prevalence of vitamin D insufficiency is continuously increasing. Basing on current literature review and opinions of National Consultants and experts in the field, polish recommendations for prophylactic vitamin D supplementation in infants, toddlers, children and adolescents as well as in adults, including pregnant and lactating women have been established.

[Prophylaxis of vitamin D deficiency--Polish recommendations 2009]

Appropriate state procurement system for vitamin D is important not only for the proper functioning of the skeletal, maintaining calcium and phosphorus homeostasis, but also for a number of other organs and tissues in our body. In connection with the change in lifestyle including dietary habits change, the widespread use of UV filters and less outdoor activity, observed an increase in the percentage of vitamin D deficiency, both in population and developmental age and adults. Based on the results of recent scientific research team of experts provides recommendations for preventive Polish supply of vitamin D in infants, children, adolescents and adults, including pregnant women and nursing mothers.

SURF1 missense mutations promote a mild Leigh phenotype

SURF1 gene mutations are the most common cause of Leigh syndrome (LS), a rare progressive neurodegenerative disorder of infancy, characterized by symmetric necrotizing lesions and hypervascularity in the brainstem and basal ganglia, leading to death before the age of 4 years. Most of the reported mutations create premature termination codons, whereas missense mutations are rare. The aim of the study was to characterize the natural history of LS patients carrying at least one missense mutation in the SURF1 gene. Nineteen such patients (8 own cases and 11 reported in the literature) were compared with a reference group of 20 own c.845_846delCT homozygous patients, and with other LS(SURF-) cases described in the literature. Disease onset in the studied group was delayed. Acute failure to thrive and hyperventilation episodes were rare, respiratory failure did not appear before the age of 4 years. Dystonia, motor regression and eye movement dissociation developed slowly. The number of patients who survived 7 years of life totaled 9 out of 15 (60%) in the 'missense group' and 1 out of 26 (4%) patients with mutations leading to truncated proteins.

IN CONCLUSION

(i) The presence of a missense mutation in the SURF1 gene may correlate with a milder course and longer survival of Leigh patients, (ii) normal magnetic resonance imaging (MRI) findings, normal blood lactate value, and only mild decrease of cytochrome c oxidase (COX) activity are not sufficient reasons to forego SURF1 mutation analysis in differential diagnosis.

Identification of vertebral deformities in the Polish population by morphometric X-ray absorptiometry - results of the EPOLOS study

INTRODUCTION

The aim of the study was the determination of the prevalence of asymptomatic vertebral deformities in healthy persons of the Polish population, based on morphometric X-ray absorptiometry (MXA), and comparison of the results with data from literature, obtained by other techniques.

MATERIAL AND METHODS

The study involved 829 persons, including 520 women and 309 men, aged 18-79 years, untreated for osteoporosis before. The Th(4) to L(4) vertebrae were examined. Lateral scans of the thoracic-lumbar spine were made by an Expert-XL densitometer. Six point digitization was used to calculate the anterior (Ha), central (Hc), and posterior (Hp) height of the Th(4)-L(4) vertebral bodies. The vertebrae were defined as having prevalent deformities when at least one ratio value (Ha/Hp, Hc/Hp, Hp/Hp up, or Hp/Hp low) fell 3 SDs below or even more than the reference mean of that ratio at any vertebral level.

RESULTS

The analysis was performed on 9629 vertebrae, of which 167 (1.75%), evaluated as deformed and considered as fractures, were observed in 113 patients (13.63 % of the examined patients). In 81 persons (74% of the patients with fractures; 9.7% of the studied population), single fractures were demonstrated, while in 28 persons, multiple deformities prevailed. Fractures occurred in 108 women (20.7% of the examined women) and 42 men (13.5% of the examined men). The highest incidence of deformities was observed in women over 55 years of age. First-degree deformities dominated. Deformities of the Th(8) and Th(6) vertebrae were most frequently observed.

CONCLUSIONS

1. Using MXA, it was found that in the Polish population deformities of vertebrae are common, as was demonstrated in X-ray morphometric studies in the European Vertebral Observation Study (EVOS). 2. Densitometric morphometry, as a non-invasive technique, may become a useful tool in the diagnostics of vertebral fractures.

Critical points in strategies for the diagnosis and treatment of osteoporosis

Current treatment decisions for osteoporosis depend on the fracture risk calculated based on the results of comprehensive diagnostic procedures [clinical risk factors (CRF), densitometry (BMD), morphometry, and bone turnover markers (BTM)]. Recently developed fracture risk assessment tool (FRAX) represents an important new achievement as a 10-year fracture risk calculation based on femoral neck densitometry and age combined with independent clinical fracture risk factors. FRAX presents several options: FRAX BMI (body mass index) is advocated as a helpful screening tool to identify the group of patients with high fracture risk, independently of access to densitometry and FRAX, utilizing hip densitometry. In both cases, the probability of major fractures or hip fractures are calculated during performed diagnostic evaluations. Operating FRAX algorithm does not include spinal bone mineral density, which is its main limitation. With the aim of improvement of anti-fracture efficacy of therapeutic management of osteoporosis, we have extended our discussion to three integral elements of existent strategy: 1) screening outlines, 2) principles of drug selection, and 3) treatment benefit evaluation. Since osteoporosis is a chronic disease, long-term adherence to the treatment is important. The suitability of the drug, the patient's preference, tolerability, and convenience should all be considered. Anti-catabolic drugs are most appropriate in patients with high bone turnover, while anabolic drugs demonstrate efficacy irrespective of bone turnover. BMD measurement is most widely used for long-term assessment of the efficacy of osteoporosis treatment. The measurements of bone turnover markers (BTMs) can be considered a useful shortterm (at 3 months) monitoring tool in selected patients. In both BTM and BMD, the least significant change (LSC) method should be used for interpretation of the results. Fractures are not a reliable clinical endpoint for evaluating the effectiveness of therapy in individual patients because of their stochastic nature. If fractures occur, however, the need for drug change and additional non-pharmacological treatment (fall prevention, balance training, muscle strengthening) should always be considered.

High prevalence of SURF1 c.845_846delCT mutation in Polish Leigh patients

Leigh syndrome is a neuropathological disorder with typical morphological changes in brain, appearing regardless of diverse molecular background. One of the most common enzymatic defects in Leigh patients is cytochrome c oxidase deficiency associated with recessive mutations in the SURF1 gene. To assess the SURF1 mutation profile among Polish patients we studied 41 affected children from 34 unrelated families by PCR-SSCP and sequencing. Four novel mutations, c.39delG, c.752-1G>C, c.800_801insT, c.821A>G, and five described pathogenic changes, c.311_312insAT312_321del10, c.688C>T, c.704T>C, c.756_757delCA, c.845_846delCT, were identified in 85.3% of analysed probands. One mutation, c.845_846delCT, was identified in 77.6% of SURF1 alleles. Up to now, it has been reported only in 9% of alleles in other parts of the world. The deletion was used as LS(SURF1-) marker in population studies. Eight heterozygous carriers of the mutation were found in a cohort of 2890 samples. The estimated c.845_846delCT allele frequency is 1:357 (0.28+/-0.2%), and the lowest predicted LS(SURF1-) frequency in Poland 1:126,736.births. Relatively high frequency of LS(SURF1-) in Poland with remarkable c.845_846delCT mutation dominance allows one to start the differential diagnosis of LS in each patient of Polish (and probably Slavonic) origin from the direct search for c.845_846delCT SURF1 mutation.

Feasibility of simultaneous measurement of bone formation and bone resorption markers to assess bone turnover rate in postmenopausal women: an EPOLOS study

BACKGROUND

One of the most important risk factors for osteoporotic fractures in postmenopausal women is elevated bone turnover (EBT), occurring in 25-30% of this population. This study's aim was to find a correlation between bone resorption and bone formation markers to assess bone turnover rate and qualify an individual postmenopausal woman as a possible EBT subject.

MATERIAL/METHODS

Three hundred twenty postmenopausal women (> or = one year after the last menstruation, < or = 70 years old) were enrolled at seven clinical sites in this cross-sectional observational study conducted within the EPOLOS. The group was a random sample of the population. The study was performed in a referral center involved in the diagnosis and treatment of osteoporosis. The exclusion criteria included pregnancy, cancer, fracture in the last year, and overweight (> 100 kg). Bone mineral density (BMD) measurements of the lumbar spine, total hip, trochanter, and femoral neck regions were performed. Bone resorption and formation rates were evaluated by serum levels of C-terminal telopeptide of type I collagen (CTX) and osteocalcin (OC), respectively.

RESULTS

Using logistic regression to correlate the concentrations of CTX and OC it was possible not only to distinguish the EBT subgroup, but also to construct a simple nomogram for easy classification of individual patients as possible EBT subjects. EBT patients showed generally decreased BMD values and increased bone formation and resorption rates.

CONCLUSIONS

Evaluation of both CTX and OC levels enables a more proper indication for EBT. The proposed nomogram may assist in evaluating outcome from the two markers of bone turnover.

Large-scale analysis of association between polymorphisms in the transforming growth factor beta 1 gene (TGFB1) and osteoporosis: the GENOMOS study

INTRODUCTION

The TGFB1 gene which encodes transforming growth factor beta 1, is a strong candidate for susceptibility to osteoporosis and several studies have reported associations between bone mineral density (BMD), osteoporotic fractures and polymorphisms of TGFB1, although these studies have yielded conflicting results.

METHODS

We investigated associations between TGFB1 polymorphisms and BMD and fracture in the GENOMOS study: a prospective multicenter study involving 10 European research studies including a total of 28,924 participants. Genotyping was conducted for known TGFB1 polymorphisms at the following sites: G-1639-A (G-800-A, rs1800468), C-1348-T (C-509-T, rs1800469), T29-C (Leu10Pro, rs1982073), G74-C (Arg25Pro, rs1800471) and C788-T (Thr263Ile, rs1800472). These polymorphisms were genotyped prospectively and methodology was standardized across research centers. Genotypes and haplotypes were related to BMD at the lumbar sine and femoral neck and fractures.

RESULTS

There were no significant differences in either women or men at either skeletal site for any of the examined polymorphisms with the possible exception of a weak association with reduced BMD (-12 mg/cm2) in men with the T-1348 allele (p<0.05). None of the haplotypes was associated with BMD and none of the polymorphisms or haplotypes significantly affected overall risk of fractures, however, the odds ratio for incident vertebral fracture in carriers of the rare T788 allele was 1.64 (95% CI: 1.09-2.64), p<0.05.

CONCLUSIONS

This study indicates that polymorphic variation in the TGFB1 gene does not play a major role in regulating BMD or susceptibility to fractures. The weak associations we observed between the C-1348-T and lumbar spine BMD in men and between C788-T and risk of incident vertebral fractures are of interest but could be chance findings and will need replication in future studies.

Light and electron microscopy characteristics of the muscle of patients with SURF1 gene mutations associated with Leigh disease

AIMS

Leigh syndrome (LS) is characterised by almost identical brain changes despite considerable causal heterogeneity. SURF1 gene mutations are among the most frequent causes of LS. Although deficiency of cytochrome c oxidase (COX) is a typical feature of the muscle in SURF1-deficient LS, other abnormalities have been rarely described. The aim of the present work is to assess the skeletal muscle morphology coexisting with SURF1 mutations from our own research and in the literature.

METHODS

Muscle samples from 21 patients who fulfilled the criteria of LS and SURF1 mutations (14 homozygotes and 7 heterozygotes of c.841delCT) were examined by light and electron microscopy.

RESULTS

Diffuse decreased activity or total deficit of COX was revealed histochemically in all examined muscles. No ragged red fibres (RRFs) were seen. Lipid accumulation and fibre size variability were found in 14 and 9 specimens, respectively. Ultrastructural assessment showed several mitochondrial abnormalities, lipid deposits, myofibrillar disorganisation and other minor changes. In five cases no ultrastructural changes were found. Apart from slight correlation between lipid accumulation shown by histochemical and ultrastructural techniques, no other correlations were revealed between parameters investigated, especially between severity of morphological changes and the patient's age at the biopsy.

CONCLUSION

Histological and histochemical features of muscle of genetically homogenous SURF1-deficient LS were reproducible in detection of COX deficit. Minor muscle changes were not commonly present. Also, ultrastructural abnormalities were not a consistent feature. It should be emphasised that SURF1-deficient muscle assessed in the light and electron microscopy panel may be interpreted as normal if COX staining is not employed.

G8363A mitochondrial DNA mutation is not a rare cause of Leigh syndrome - clinical, biochemical and pathological study of an affected child

Leigh syndrome (LS), or subacute necrotizing encephalomyelopathy, having relatively homogeneous clinical symptomatology and pattern of neuropathological changes, shows remarkable heterogeneity in biochemical and molecular background. G8363A mitochondrial DNA mutation typical for MERRF syndrome and progressive cardiomyopathy may also be associated with LS. Clinical, biochemical and pathological findings in a boy aged 28 months who died with classical COX-deficientLSassociatedwithmtG8363Aisdescribedindetail.Hyperlactataemia,LCHAD-like organic acids profile and respiratory alkalosis(pH7.47,pCO2 4.9 mmHg, HCO3 3.0 mmol/l) were observed. Spectrophotometric assay showed deficit of respiratory chain complexes IVand I. Skeletal muscle biopsy revealed mosaic cytochrome oxidase deficit,lipid accumulation and ultrastructural abnormalities of mitochondria. Postmortem examination confirmed the presence of typical LS central nervous system lesions as well as hypertrophy of the left ventricle of the heart.

CONCLUSION

mtG8363A "MERRF-like" mutation should be included in the differential diagnosis of classical LS in infants. This case is in agreement with our hypothesis that hyperventilation plays a substantial role in progression of central nervous system damage.

Bone mineral metabolism in children with biliary atresia after living related liver transplantation. Evaluation of selected parameters

BACKGROUND

Aim of the study was to analyze the effect of living related liver transplantation on selected parameters of bone formation and resorption in children with liver cirrhosis caused by biliary atresia.

MATERIAL/METHODS

20 children (13F/7M) with biliary atresia aged from 6 month to 2.4 years were enrolled into the study 4-9 days before liver transplantation. Osteocalcin, procollagen 1 aminoterminal propeptide, collagen type 1 crosslinked C-telopeptide, parathyroid hormone and metabolites of vitamin D: 25(OH)D3, 1,25(OH)2D3 were measured before, 3, 6 and 12 months after liver transplantation.

RESULTS

Three months after living related liver transplantation statistically significant increase of osteocalcin, collagen type 1 crosslinked C-telopeptide, parathyroid hormone and 1,25(OH)2D3 levels were found. We didn't observe further increase of these parameters during the next 9 months after liver transplantation. There was no difference in 25(OH)D3 levels in patients before and after liver transplantation.

CONCLUSIONS

In children after successful living related liver transplantation we observed improvement of selected parameters of bone formation and resorption which indicate stimulation of growing processes and mechanisms of bone geometry modelling.

Skeletal and muscular status in juveniles with GFD treated clinical and newly diagnosed atypical celiac disease--preliminary data

Undiagnosed and untreated celiac disease (CD) constitutes an increasing skeletal health problem due to its association with low bone density and fractures. Examinations of skeletal status in children using dual-energy X-ray absorptiometry (DXA) are prone to size-related misinterpretation. In contrary, the analysis of muscle-bone relationship seems to limit a possibility of misdiagnosis because skeletal status is evaluated from the functional perspective. The study was aimed to assess skeletal status of children suffering from CD with the use of muscle-bone functional algorithm. The study group comprised 29 celiac patients (13.7yr+/-2.9) on gluten-free diet (GFD), and 24 newly diagnosed atypical celiac patients, including subgroup with normal height (n=14; 12.6yr+/-3.9) and subgroup with short stature (n=10; 12.2yr+/-2.9). Muscular and skeletal status was evaluated by DXA (DPX-L, GE). Anthropometry, total body bone mineral density (TBBMD, g/cm(2)). and total body bone mineral content (TBBMC, g) as well as lean body mass (LBM, g) were evaluated. Muscle-bone interactions were estimated using TBBMC/LBM ratio. Previously established references for healthy controls were used for the calculation of Z-scores (age-matched) and SD-scores (height-matched). GFD treated celiacs and atypical celiacs with normal body height had TBBMD, TBBMC, LBM, and TBBMC/LBM ratio Z-scores and SD-scores within normal range for healthy controls. In contrary, atypical celiacs with short stature had significantly lower Z-scores for TBBMD (-2.3+/-0.4), TBBMC (-2.1+/-0.3), LBM (-1.4+/-0.3). and TBBMC/LBM ratio (-2.3+/-0.6) when compared to respective values observed in GFD treated celiacs (p<0.001, p<0.001, p<0.05, p<0.01) and atypical celiacs with normal height (p<0.01, p<0.01, p<0.05, p<0.01). When body-height matching of DXA data was used to limit the influence of body size, the atypical celiacs with short stature had SD-scores for TBBMD (-1.3+/-0.7), TBBMC (-1.3+/-0.6), and LBM (+0.8+/-0.3) not significantly different from the corresponding SD-scores obtained in the remaining 2 groups. Nevertheless, short stature in atypical celiacs still coincided with significantly lower TBBMC/LBM ratio SD-score of -1.9+/-0.7 when compared to values observed in GFD treated celiacs (+0.04+/-0.2; p<0.05) and atypical celiacs with normal height (-0.4+/-0.2; p<0.05). GFD regime in classic celiacs corresponded with physiological values of DXA assessed indicators of bone and muscle status as well as normal muscle-bone interactions. Untreated atypical celiacs may present a broad spectrum of heterogeneous abnormalities from normal to markedly depressed TBBMC/LBM ratio values pointing on the marked imbalance between TBBMC and LBM.

The association between common vitamin D receptor gene variations and osteoporosis: a participant-level meta-analysis

BACKGROUND

Polymorphisms of the vitamin D receptor (VDR) gene have been implicated in the genetic regulation of bone mineral density (BMD). However, the clinical impact of these variants remains unclear.

OBJECTIVE

To evaluate the relation between VDR polymorphisms, BMD, and fractures.

DESIGN

Prospective multicenter large-scale association study.

SETTING

The Genetic Markers for Osteoporosis consortium, involving 9 European research teams.

PARTICIPANTS

26,242 participants (18,405 women).

MEASUREMENTS

Cdx2 promoter, FokI, BsmI, ApaI, and TaqI polymorphisms; BMD at the femoral neck and the lumbar spine by dual x-ray absorptiometry; and fractures.

RESULTS

Comparisons of BMD at the lumbar spine and femoral neck showed nonsignificant differences less than 0.011 g/cm2 for any genotype with or without adjustments. A total of 6067 participants reported a history of fracture, and 2088 had vertebral fractures. For all VDR alleles, odds ratios for fractures were very close to 1.00 (range, 0.98 to 1.02) and collectively the 95% CIs ranged from 0.94 (lowest) to 1.07 (highest). For vertebral fractures, we observed a 9% (95% CI, 0% to 18%; P = 0.039) risk reduction for the Cdx2 A-allele (13% risk reduction in a dominant model).

LIMITATIONS

The authors analyzed only selected VDR polymorphisms. Heterogeneity was detected in some analyses and may reflect some differences in collection of fracture data across cohorts. Not all fractures were related to osteoporosis.

CONCLUSIONS

The FokI, BsmI, ApaI, and TaqI VDR polymorphisms are not associated with BMD or with fractures, but the Cdx2 polymorphism may be associated with risk for vertebral fractures.

Large-scale evidence for the effect of the COLIA1 Sp1 polymorphism on osteoporosis outcomes: the GENOMOS study

BACKGROUND

Osteoporosis and fracture risk are considered to be under genetic control. Extensive work is being performed to identify the exact genetic variants that determine this risk. Previous work has suggested that a G/T polymorphism affecting an Sp1 binding site in the COLIA1 gene is a genetic marker for low bone mineral density (BMD) and osteoporotic fracture, but there have been no very-large-scale studies of COLIA1 alleles in relation to these phenotypes.

METHODS AND FINDINGS

Here we evaluated the role of COLIA1 Sp1 alleles as a predictor of BMD and fracture in a multicenter study involving 20,786 individuals from several European countries. At the femoral neck, the average (95% confidence interval [CI]) BMD values were 25 mg/cm2 (CI, 16 to 34 mg/cm2) lower in TT homozygotes than the other genotype groups (p < 0.001), and a similar difference was observed at the lumbar spine; 21 mg/cm2 (CI, 1 to 42 mg/cm2), (p = 0.039). These associations were unaltered after adjustment for potential confounding factors. There was no association with fracture overall (odds ratio [OR] = 1.01 [CI, 0.95 to 1.08]) in either unadjusted or adjusted analyses, but there was a non-significant trend for association with vertebral fracture and a nominally significant association with incident vertebral fractures in females (OR = 1.33 [CI, 1.00 to 1.77]) that was independent of BMD, and unaltered in adjusted analyses.

CONCLUSIONS

Allowing for the inevitable heterogeneity between participating teams, this study-which to our knowledge is the largest ever performed in the field of osteoporosis genetics for a single gene-demonstrates that the COLIA1 Sp1 polymorphism is associated with reduced BMD and could predispose to incident vertebral fractures in women, independent of BMD. The associations we observed were modest however, demonstrating the importance of conducting studies that are adequately powered to detect and quantify the effects of common genetic variants on complex diseases.

Retrospective, multicentric study of 180 children with cytochrome C oxidase deficiency

A retrospective, multicenter study of 180 children with cytochrome c oxidase (COX) deficiency analyzed the clinical features, prognosis, and molecular bases of the COX deficiency. Clinical symptoms including failure to thrive, encephalopathy, hypotony, Leigh syndrome, cardiac involvement, and hepatopathy appeared in most patients early after birth or in early childhood. Two thirds of all children died. Biochemical examination revealed an isolated COX deficiency in 101 children and COX deficiency combined with disturbances of other respiratory chain complexes in 79 children. Blood and cerebrospinal fluid lactate increased in 85% and 81% of examined cases, respectively. Pathogenic mutations in mitochondrial or nuclear DNA were established in 75 patients. Mutations in surfeit locus protein 1 gene (SURF1) were found in 47 children with Leigh syndrome; 2bp deletion 845-846delCT was found in 89% of independent alleles. Mutations in a mitochondrial copper-binding protein (SCO2) gene were found in nine children with encephalomyopathy and/or cardiomyopathy; all of them were homozygotes or heterozygotes for 1541G>A mutation. Different mitochondrial DNA (mtDNA) deletion or depletion were found in nine children, mtDNA mutation 3243A>G in six, mtDNA mutation 8363G>A in two children with Leigh syndrome and mtDNA mutations 8344A>G, and 9205-9206delTA in one child each. COX deficiency represents a heterogeneous group of diseases with unfavorable prognosis. Marked prevalence of two nuclear DNA mutations (845-846delCT in the SURF1 gene and 1541G>A in the SCO2 gene) associated with COX deficiency in a Slavonic population suggests the existence of regional differences in the genetic basis of COX deficiency.

Beneficial effect of liver transplantation on bone mineral density in small infants with cholestasis

Reports of bone mineral density in children after liver transplantation are few. Eleven cholestatic children were analyzed before and 6 months after liver transplantation. No changes in serum levels of calcium, alkaline phosphates, or 25OHD were observed before versus after LTx. The serum levels of phosphorus and 1-25(OH)2D3 as well as total bone mass density and Cole index were significantly increased after liver transplantation.

Diversity of clinical symptoms in A3243G mitochondrial DNA mutation (MELAS syndrome mutation)

BACKGROUND

MELAS (mitochondrial myopathy, lactic acidosis and stroke-like episodes) is one of the most common mitochondrial encephalomyopathies.

MATERIAL/METHODS

We present four children with A3243G MELAS mtDNA mutation and give a summary of clinical MELAS symptoms reported in the literature. Serum lactate elevation, mosaic pattern of COX deficit and decreased activity of complex I and IV in the muscle biopsy were found in all cases. RRFs were recognized in three out of four.

RESULTS

The main features seen in all our patients were poor growth and fatigability with muscle weakness. All presented epileptic jerks of various character, some deformation features (recurrent pretibial and peritarsal edema, large swollen-looking hands and feet, hypertelorism and protruding ears) and some cutaneous lesions (atopic dermatitis, local melanoderma, asymmetric vascular dilatation). Stroke-like episodes, multihormonal hypopituitarism, sensorineural hypoacusis, pigmentary retinal degeneration, intracranial calcification, heart involvement, recurrent vomiting or abdominal pain were seen only in individual cases. The homonymous hemianopia frequently reported in the literature was not a feature of our patients. One of them suffered from nonspecific sialoadenitis never mentioned in the literature.

CONCLUSIONS

Morphological, enzymatic and molecular investigations of a muscle biopsy sample should be undertaken to improve early MELAS detection in patients with any multiorgan disease associated with serum lactate elevation.

[MELAS--mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes syndrome--two cases confirmed by biochemical and molecular investigations. Differential diagnosis of stroke causes]

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome (MELAS) is a maternally inherited multisystem disease caused by mutations of the mitochondrial DNA. The characteristic clinical features are: encephalopathy manifesting as dementia and seizures, stroke-like episodes at young age (usually < 40), lactic acidosis and myopathy with ragged-red fibres. Other frequent manifestations include: sensorineural deafness, diabetes, hypoparathyroidism, peripheral neuropathy and cardiomyopathy. We present two patients with MELAS who were diagnosed 4 and 9 years respectively following the onset of the disease despite the characteristic clinical pictures. The differential diagnostics of inborn and acquired disorders causing stroke is included. We regard that mitochondrial diseases are still insufficiently known and are frequently misdiagnosed. The knowledge is indispensable for establishing diagnosis and accurate genetic counselling. Although there is no specific therapy for mitochondrial diseases to date, coenzyme Q and various vitamins as well as moderate degree exercise might be recommended.

Compulsory hyperventilation and hypocapnia of patients with Leigh syndrome associated with SURF1 gene mutations as a cause of low serum bicarbonates

Experimental data show that elevation of intracellular pH leads to severe lesions of brain cells. Acidification of intracellular fluid by accumulation of lactate may compensate the effect of respiratory alkalosis. Increased serum pH, and low PCO2, associated with hyperlactataemia (sometimes incorrectly called 'acidosis') have been reported in children with Leigh syndrome (LS). The aim of the study was to determine whether respiratory alkalosis is characteristic of patients with LS due to SURF1 mutations. All venous blood gas data (88 samples) of 18 spontaneously breathing LS patients with recently established SURF1 mutations, hospitalized during 1986-2000, were retrospectively reviewed. The data of an affected boy who survived on a respirator for more than 3 months (79 daily samples) were analysed separately. In spontaneously breathing patients, the data indicated that the patients had compensated or partially compensated respiratory alkalosis (pH 7.388+/-0.060, Pco2 29.2+/-5.7 mmHg, HCO3- 17.4+/-3.0 mmol/L, BE -6.7+/-3.2 mmol/L). Bicarbonate excretion was detected in urine of two examined LS cases in spite of decreased serum HCO3-. In the affected child maintained on a respirator, simple manipulation of the inspired CO2 tension to establish a normal pressure of 35-45 mmHg automatically caused an increase of serum HCO3- concentration to a normal value of 26.3+/-2.9 mmol/L (and BE to +2.2+/-3.1 mmol/L), in spite of cytochrome oxidase (COX) deficiency due to a confirmed SURF1 mutation. We suggest that respiratory alkalosis (hypocapnia) of Leigh syndrome patients with SURF1 mutations results from compulsory hyperventilation and speculate that hypocapnia may contribute to Leigh-like brain damage in the SURF1-deficient patients as well as in other patients presenting with Leigh-like syndrome. The supposition that accumulation of lactate may protect the brain of LS patients from alkalosis-related damage requires further study. Avoidance of any factors stimulating hyperventilation of LS patients and caution when attempting to correct low plasma bicarbonate are suggested.

Abnormal calcium homeostasis in fibroblasts from patients with Leigh disease

Recently, we reported that in various cell lines under conditions of deenergization of the mitochondrial membrane, the release of Ca(2+) from the endoplasmic reticulum (ER) does not produce the expected activation of store-operated calcium channels (SOCs) in the plasma membrane. In the present work, we examined the activation of SOCs in fibroblasts derived from three patients with Leigh disease (LS). We identified mutations in the SURF-1 gene in all these cells. Consequently, cytochrome oxidase (COX) deficiency was found in all these (LS(COX)) cell lines and, thus, the main mitochondrial mechanism of generation of the electrochemical proton gradient on the mitochondrial membrane was naturally depressed. We demonstrated that, in untreated LS(COX) fibroblasts, the rate of Ca(2+)-inflow through SOCs was low compared to the fibroblasts from healthy individuals even after thapsigargin-induced maximal release of Ca(2+) from the ER. Moreover, the pretreatment of LS(COX) fibroblasts with a protonophore did not modify this rate. Thus, in LS(COX) fibroblasts, the activation of SOCs was naturally impaired. Our findings suggest that altered calcium metabolism, apart from severe energy production failure, may also contribute to developing pathological conditions in patients with COX-deficient Leigh disease related to SURF-1 gene mutation.

The role of endogenous nitric oxide in inhibition of ischemia/reperfusion-induced cardiomyocyte apoptosis

The effect of nitric oxide (NO) synthase inhibition on apoptosis of cardiomyocytes during ischemia/reperfusion was investigated. Isolated perfused guinea-pig hearts were subjected to 35 min ischemia (I) followed by 30 min reperfusion (IR) in the presence or absence of NO synthase inhibitors, L-NAME or L-NMMA or a superoxide scavenger, SOD. Apoptosis was assessed by immunohistochemistry (TUNEL assay, Bax protein staining), by spectrophotometric measurement of cytochrome oxidase activity (COX), and by ultrastructural analysis. Inhibition of NOS significantly increased apoptosis with activation of Bax protein and decrease of COX. SOD infusion had a protective effect on these apoptotic markers. The results suggest that endogenous NO synthesis during I/R protects the heart against apoptotic cell death.

SURF1 gene mutations in Polish patients with COX-deficient Leigh syndrome

One of the most frequent forms of Leigh syndrome (LS), a severe neurodegenerative, genetically heterogenous disease, is associated with cytochrome c oxidase (COX) deficiency. No mutations in any of the 13 polypeptide subunits of human COX have been detected in LS patients. Recently, SURF1, a positional candidate gene for LS has been identified on chromosome 9q34. We present the identification of SURF1 mutations in a randomly chosen group of Polish patients with a classical form of LS. Sequence analysis revealed the presence of a novel 704T-->C transition (Met235Thr), and two recurrent dinucleotide deletions (758delCA, 845delCT), as well as one novel polymorphic 573C-->G transversion (Thr191Thr). 845delCT was identified in 66% of all our patients in homozygous or heterozygous form. Our study confirms the recent observations that SURF1 is consistently involved in disorders of the mitochondrial respiratory chain in patients with typical Leigh syndrome.

Improvement of titanium alloy for biomedical applications by nitriding and carbonitriding processes under glow discharge conditions

Although titanium alloys are used in medicine, they present low wear resistance. In this paper we present the results of studies on surface layers produced by nitriding at three different temperatures, and by carbonitriding under glow discharge conditions in order to improve wear resistance, hardness, and to modulate microstructure and chemical composition of surface layers. A cell culture model using human fibroblasts was chosen to study the effect of such treatments on the cytocompatibility of these materials. The results showed that nitrided and carbonitrided surface layers were cytocompatible. Modulation of surface microstructure by temperature in the nitriding process and chemical composition of surface layers by carbonitriding led to differences in cellular behaviour. Cell proliferation appeared to be slightly reduced from the 6th day of culture on nitrided surfaces produced at 730 degrees C and 1000 degrees C, however after 12 days of culture, the best growth was on surface layers produced at 850 degrees C. The best viability was observed on the carbonitrided layer. The orientation and shape of the cells corresponded to surface topography. Nitriding and carbonitriding under glow discharge conditions may constitute interesting techniques allowing the formation of surface layers on parts with sophisticated shapes. They may also permit modulating surface topography in a way improving the features of titanium alloys for various applications in medicine.

Vitamin B-6 deficiency alters rat enterocyte calcium homeostasis but not duodenal transport

Isolated enterocytes were used as differential transporting cells to examine calcium homeostasis in control and vitamin B-6-deficient rats. Kinetic analysis of calcium fluxes, as well as biochemical determinations, indicated that enterocytes from control animals had high concentrations of cytosol ionized calcium (318.5 +/- 22.4 nmol/L) and a large pool of exchangeable calcium (2.72 nmol/mg protein, or 86% of total cell calcium). Vitamin B-6 deficiency resulted in a 44% reduction in total cellular calcium (1.71 +/- 0.24 vs. 3.07 +/- 0.29 nmol/mg protein), a 69% reduction in total exchangeable calcium (0.85 vs. 2.72 nmol/mg protein) and a 56% reduction in cytosol ionized calcium concentration (141.4 +/- 13.5 vs. 318.5 +/- 22.4 nmol/L). Calcium fluxes between all cellular compartments were markedly diminished as a result of vitamin B-6 deficiency. However, vitamin B-6 deficiency did not affect the basic morphological or functional features of the enterocytes, such as cell viability, cell volume, membrane permeability and protein content. Moreover, intestinal calcium transport in vivo was not affected during vitamin B-6 deficiency, perhaps due to the greater paracellular ion movement compensating for the lower transcellular transport.

Activation of liver cytosol phosphoenolpyruvate carboxykinase by Ca2+ through intracellular redistribution of Mn2+

Calcium has no known direct effect on phosphoenolpyruvate carboxykinase from rat liver cytosol. However, addition of calcium salts to liver postnuclear supernatant led to an increase in assayable enzyme activity in cytosols. This indicates that mitochondria and microsomes present in postnuclear supernatant can participate in observed enzyme activation. The stimulation of phosphoenolpyruvate carboxykinase was prevented by the manganese complexion 1-(2-pyridylazo)-2-naphthol, was not additive with activation by MnCl2 and was inhibited by La3+, Sr2+ and ruthenium red. These data indicate that manganese and mitochondrial or microsomal calcium carriers participate in the mechanism of indirect calcium effect. Measuring of manganese content in cytosols directly, by atomic absorption spectrometry, has provided evidence that there is a pool of manganese associated with mitochondrial and microsomal fraction of rat liver that can be mobilized to the cytosol by calcium ions. The direct addition of this pool of manganese to the cytosol caused the stimulation of phosphoenolpyruvate carboxykinase activity to the same levels as did calcium ions in the postnuclear supernatant. It is postulated that calcium can effect enzyme activity indirectly by releasing manganese from specific cellular compartments into the cytosol.