Vitamin D and its effects on glucose homeostasis, cardiovascular function and immune function

In recent years there has been increasing interest in the non-skeletal effects of vitamin D. It has been suggested that vitamin D deficiency may influence the development of diabetes, cardiovascular dysfunction and autoimmune diseases. This review focuses on the current knowledge of the effects of vitamin D and its deficiency on cardiovascular function, glucose homeostasis and immune function, with a particular focus on children. Although, there is good evidence to show that there is an association between vitamin D deficiency and an abnormality of the above systems, there is little evidence to show that vitamin D supplementation leads to an improvement in function, especially in childhood.

Recent trends and clinical features of childhood vitamin D deficiency presenting to a children's hospital in Glasgow

BACKGROUND

The incidence of vitamin D deficiency is unclear in the context of continuing demographic changes and the introduction of new public health measures.

METHODS

All cases in which vitamin D deficiency was suspected as the primary cause of the clinical presentation were studied.

RESULTS

Between 2002 and 2008, 160 cases of symptomatic vitamin D deficiency were identified with twice as many cases in 2008 (n, 42) as in the previous years. The median age of the cohort was 24 months (range 2 weeks-14 years).Three cases were recorded in children of European background, whereas the rest were in children of South Asian, Middle Eastern or sub-Saharan ethnic background. Presenting features included bowed legs in 64 (40%) and a fit in 19 (12%). In one infant, concerns were raised following a presentation with cardiac failure and hypocalcaemia.

SUMMARY

Symptomatic vitamin D deficiency remains prevalent in the West of Scotland. There is a need for effective public health education, action and surveillance.

Changes in quantitative ultrasound in infants born at less than 32 weeks' gestation over the first 2 years of life: influence of clinical and biochemical changes

Studies in preterm infants show reduced speed of sound (SOS) as measured by quantitative ultrasound (QUS) during the immediate neonatal period. There is a scarcity of data on SOS changes following hospital discharge. The aim of this study was to assess SOS over the first 2 years in preterm infants. Infants were recruited from a neonatal follow-up clinic. Tibial QUS was performed using the Omnisense 7000P scanner. Thirty-nine infants born at <32 weeks' gestation had a single SOS measurement (median 3,203 m/second, range 2,609-3,495) which correlated with corrected gestational age (CGA) (r = 0.8, P < 0.005). The majority of measurements were within the manufacturer's reference range for term infants. SOS standard deviation score (SDS) in infants aged 0-6 months CGA demonstrated a negative correlation with duration of total parenteral nutrition (r = 0.7, P < 0.05) and a positive correlation with serum phosphate (r = 0.6, P < 0.05.) Two groups of infants had serial measurements: eight had measurements performed at term CGA and early infancy (early) and seven had measurements in later infancy (late). In the early group SOS SDS increased (P < 0.005), and the greatest increase in SOS over time occurred in infants with the lowest SOS at term (r = 0.9). In the late group there was no significant change over time. SOS SDS change did not show any correlation to weight SDS change. Catch-up in SOS occurs postterm in most infants by 6 months and is independent of postnatal growth. Infants with the lowest SOS at term have the fastest rate of catch-up. The opportunity for catch-up may be greatest in early infancy.

Quantitative ultrasound assessment of bone health in the neonate

For a number of reasons there is a need to explore reliable non-invasive methods for assessing bone health in neonates and young infants. Epidemiological studies suggest that early events in life may predispose the adult to degenerative diseases such as osteoporosis. Preterm infants have an increased risk of low bone mass because of limited bone mass accretion in utero and a greater need for bone nutrients. Despite improvements in neonatal care fractures still occur. The diagnosis of osteopaenia of prematurity remains difficult as there is no screening test which is both sensitive and specific. Biochemical indices are non-diagnostic, and plain X-rays in the absence of fractures are poor at diagnosing bone disease. Although dual energy X-ray absorptiometry is increasingly used to assess bone mineral status in newborn infants, the size and immobility of the scanner, the length of time to perform the scan and use of ionising radiation make it unsuitable for routine use in the setting of the fragile very low birth weight infant. Quantitative ultrasound (QUS) was first developed in 1984, as a non-ionising, portable and low cost method of assessing bone health. The measurements obtained from QUS are thought to be related not only to the mineral density of the bone but also to reflect parameters of bone quality and strength. Preliminary studies suggest that this technique may be a useful method of assessing changes in bone health in preterm infants, but the data need to be interpreted carefully. This review will concentrate on the methodology of QUS and the studies that have already been performed in neonates.

Longitudinal changes in bone health as assessed by the speed of sound in very low birth weight preterm infants

OBJECTIVE

To assess longitudinal changes in speed of sound (SOS) in very low birth weight (VLBW) infants and investigate the relationship with markers of osteopathy of prematurity (OP) and clinical illness.

STUDY DESIGN

Twenty-five infants were recruited. Eighteen infants, median gestation 27 weeks (range 24-32), median birth weight 957 g (range 625-1500 g), had serial scans. SOS was measured at both tibiae weekly until 35 to 37 weeks corrected gestational age (CGA).

RESULTS

Initial median SOS standard deviation score (SDS) (Z) score was -0.07 (range-1.3-1.3). SOS correlated with gestation (r, 0.8, P<.005), and birth weight (r, 0.67, P<.005.) SOS fell from a median of 2923 m/s (2672-3107) at birth to 2802 m/s (2502-2991) at 35 to 37 weeks CGA (P<.05). This fall was greater in the 24- to 27-week gestation cohort with a median reduction of 2.2 SDS (1.6, 4.0) compared with 1.3 SDS (0.8-2.2) in those>28 weeks (P<.05). There was a negative correlation between SOS, at the end of the study, peak serum alkaline phosphatase (ALP) (r, 0.6, P<.05), CRIB (Clinical Risk Index for Babies)/CRIB II scores (both r, 0.6, P<.05), and duration of total parenteral nutrition (TPN) (r, 0.58, P<.05.)

CONCLUSIONS

Although tibial SOS was within the expected range at birth, there was a subsequent failure to gain SOS, and this was most marked in infants of a lower gestation.

Quantitative ultrasound assessment of bone in preterm and term neonates

There is a need to explore novel methods of assessing bone health in sick preterm infants. This study of the speed of sound in the long bones of newborn term and preterm infants shows that, in this population, this technique is not site specific and has a high degree of interobserver and intraobserver precision. The speed of sound in newborn infants is primarily dependent on gestation rather than birth weight.

Transgenic mice expressing surface markers for IFN-gamma and IL-4 producing cells

The detection of T(H)1-type and T(H)2-type cells directly in situ would be of great value in the study of T(H) development and function in vivo. Transgenic mice expressing human Thy1 and mouse Thy1.1 under the control of the murine IFN-gamma and IL-4 promoters, respectively, have been generated. The hThy1(+) cells represent (with some temporal lag) most of the IFN-gamma-producing CD4(+) T-cells, while the mThy1.1(+) cells represent only a percentage of IL-4 secreting cells. This may be due to mono-allelic expression of the IFN-gamma and IL-4 genes. Since permeabilization is not required for the detection of the transgenic surface markers, these transgenic mice can facilitate the detection of T(H)1-type and T(H)2-type cells by flow cytometry with surface immunofluorescent staining. These surface markers should permit isolation of viable cells according to their T(H) type for adoptive transfer experiments, and may serve as a model system for tracing the development of T(H)1 and T(H)2-type cells in vivo.

A new model for rheumatoid arthritis?

A chance observation has led to the development of a new murine model for inflammatory arthritis. Arthritis is induced, and transferred, by T-cell-dependent antibodies to glucose-6-phosphate isomerase. This enzyme is expressed in all cells, and is detectable in serum. There are several similarities to rheumatoid arthritis (RA) in the murine disease. This elegant model raises several questions as to how and why a systemic response focuses inflammation so strongly on synovial joints. The model also re-introduces the possibility that antibodies to widely expressed self-proteins may play a role in the pathogenesis of RA.

Rheumatoid arthritis and its animal models: the role of TNF-alpha and the possible absence of specific immune reactions

Rheumatoid arthritis is an organ-specific inflammatory disease of humans. Recent studies have focused on associations with non-MHC genes, new autoantigens and the role of innate immune responses. The success of anti-TNF-alpha in the majority (but, interestingly, not all) of patients has implications for disease mechanisms but the dangers of long-term therapy are becoming clearer. A number of new models of arthritis have been defined and emphasize the importance of the genetic make-up of the host. Attention has also focused on why the joint is a particularly vulnerable site for inflammatory responses.

Identification of autoantigen epitopes in MHC class II transgenic mice

MHC class II molecules function by selective binding of antigenic peptides, thereby both shaping the T-cell receptor (TCR) repertoire in the thymus and influencing presentation of immunogenic peptides to CD4+ T cells in the periphery. The strong association between a number of human autoimmune diseases (type 1 diabetes, rheumatoid arthritis, and multiple sclerosis) and certain HLA-DR/DQ alleles suggests that it may be possible to alter pathological autoimmune responses by deliberate introduction of autoantigenic peptides in a "tolerogenic" manner. Since there are likely to be differences in epitope selection and epitope spreading in different patients over time, this approach requires identification of all the immunogenic CD4+ T-cell epitopes (dominant, subdominant, or cryptic) of an autoantigen which elicit T-cell responses restricted to the HLA-DR/DQ alleles predisposing to these autoimmune diseases. This paper describes a new approach for the identification of immunogenic peptide epitopes of human autoantigenic proteins using HLA-DR and DQ transgenic mice. These mice are engineered to select a full TCR repertoire which can identify immunogenic peptide epitopes similar or identical to human subjects of the same HLA-DR/DQ genotype. This experimental system also allows comparison of autoantigenic immune responses restricted to disease-susceptible and disease-resistant HLA-DR/DQ alleles.

Prevention of insulin-dependent diabetes mellitus in nonobese diabetic mice by immunogenic but not by tolerated peptides

In the nonobese diabetic (NOD) mouse, susceptibility to insulin-dependent diabetes mellitus is in part controlled by a single expressed class II major histocompatibility complex (MHC) molecule, I-Ag7. This molecule probably exerts its control through the representation of a self-peptide, derived from an unknown beta cell antigen, leading to T cell activation and eventual islet destruction. In this paper, synthetic peptides have been used to compete for binding to the I-Ag7 molecule in an attempt to suppress the autoimmune response. The administration of an I-Ag7-binding immunogenic peptide, lambda repressor (cI) 12-26, in a water and oil emulsion (incomplete Freund's adjuvant) can prevent the transfer of IDDM into irradiated recipients by spleen cells from diabetic donors. Nonbinding, nonimmunogenic peptides have no effect in this situation. However, the immune response to the "blocking" peptide in these experiments was a complicating factor in interpreting the results. To establish that the effect was at the level of competition for MHC binding, two additional approaches were tried. First, tolerance was induced to the immunogenic peptide, cI 12-26, before using it to "block" disease. Tolerance abolished the effect on diabetes transfer. Second, an effort was made to identify peptides that were nonimmunogenic but that bound to I-Ag7. Such a peptide, mouse prostatic secretory glycoprotein precursor 63-76, had no effect on the incidence of transferred disease. We conclude that the "blocking" effects seen in initial experiments in the NOD mouse were not caused by blockade of MHC presentation, but by other unknown effects related to the immunogenicity of the "blocking" peptide.

Isolation of nonobese diabetic mouse T-cells that recognize novel autoantigens involved in the early events of diabetes

Insulin-dependent diabetes mellitus (IDDM) is thought to result from chronic, cell-mediated, autoimmune islet damage. Our aim was to identify the earliest T-cell autoantigen in IDDM, reasoning that this antigen could be causally involved in the initiation of the disease. Identification of the earliest beta-cell-specific autoantigen is extremely important in allowing advances in prevention and treatment of initial events in the development of inflammatory insulitis that precedes beta-cell destruction and overt diabetes. Therefore, we analyzed the proliferative responses of peripheral T-cells from young, female nonobese diabetic (NOD) mice to extracts of pancreatic beta-cell lines. We were able to demonstrate that T-cells responsive to beta-cell antigens exist in the peripheral lymphoid tissue of these mice in the absence of deliberate priming before the manifestation of histologically detectable insulitis. T-cell lines and clones isolated from the peripheral lymphatic tissues of young, unimmunized, female NOD mice were also shown to react with extracts of beta-cells. Fractionation of the beta-cell extracts showed that these T-cell clones recognized multiple beta-cell-specific autoantigens but none of the previously reported putative autoantigens (glutamic acid decarboxylase [GAD]65, GAD67, Hsp65, insulin, ICA 69, carboxypeptidase-H, and peripherin). Thus, we can conclude that these responses are specific for novel beta-cell autoantigens. Finally, NOD T-cell proliferative responses were also seen to an extract of human islets suggesting potential shared antigenic determinants between human and mouse beta-cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Competitive inhibition of antigen presentation in animal models of autoimmune disease

Competition between peptides for binding to class II major histocompatibility complex (MHC) molecules has been demonstrated both in vitro and in vivo. Peptide competition may provide a way to interfere with T cell activation in the treatment of autoimmune diseases. It may be possible to provide a substitute 'blocking' peptide to compete for presentation of an autoantigenic peptide to T cells. The approach described is a general one, which may be applicable to a number of T cell mediated MHC-linked autoimmune diseases, and to other undesirable immune responses. So far, peptide competitors have only been successfully used in the prevention of experimental autoimmune encephalomyelitis (EAE). Whether or not this approach will work in treating spontaneous disease models remains to be tested, although work in other test systems is encouraging.

HLA-DQ beta-chain polymorphism linked to myasthenia gravis

The HLA-DR3 haplotype is associated with increased risk of myasthenia gravis (MG) and a number of other autoimmune diseases, including insulin-dependent diabetes mellitus (IDDM), coeliac disease, and premature ovarian failure (POF). With a cDNA probe for a DQ beta gene, a 15 kb Hinc II restriction fragment has been demonstrated in genomic DNA from 7 of 16 HLA-DR3 patients with MG, 1 of 19 healthy DR3 controls, and none of 24 DR3 patients with IDDM, coeliac disease, or POF. The HLA-DQ polymorphism may be closely linked to a genetic locus regulating immune responsiveness to acetylcholine receptor and susceptibility to MG.

Identification of stage-specific polypeptides synthesized during murine preimplantation development

[35S]Methionine-labeled extracts of mouse ova and preimplantation embryos were analyzed by two dimensional polyacrylamide gel electrophoresis. Of the 400-600 molecular species that have been resolved as distinct spots on autoradiograms of gels for every stage of development from unfertilized eggs to early blastocysts, particular attention has been paid to the identification of 36 of these proteins, each of which is expressed only for a portion of the period under investigation. These molecules are referred to as stage-specific polypeptides and they are biochemical markers of early embryonic development and differentiation.

Use of high dose X-irradiation to block back stimulation in the MLC reaction

Paradoxical stimulation, "back stimulation" was observed in MLR (mixed lymphocyte culture reaction) in both family and population studies. This is one of the major problems in obtaining clear cut-off points for stimulation and non-stimulation in MLR using LD (lymphocyte defined) homozygous typing cells. The ability to provoke back stimulation was found to be different among LD homozygous typing cells. The presence of nonspecific blastogenic factors in supernatant from mixed culture of LD homozygous cells and heterozygous cells, which might be responsible for back stimulation, was confirmed. It was clearly shown that irradiation of LD homozygous typing cells with 6,000 rads instead of the widely used 3,000 rads can greatly reduce or eliminate this back stimulation without introducing any false non-stimulation.