Age-dependent cardiac remodelling – role of sex hormones

Background

While cardiovascular mortality in women has exceeded those in men, women continue to be underrepresented in cardiovascular clinical trials. Further, preclinical experiments are predominantly conducted in male animals, rendering sex-specific variables contributing to cardiovascular disease largely unknown. As age and menopause remain to be key risk factors for cardiovascular disease in women, the aim of this study was to identify key variables of cardiac remodelling in the aging female and male heart, as well as to assess effects of sex hormone deprivation on left ventricular (LV) morphology, LV function and cardiac sympathetic activity.

Materials and methods

Gonadectomized and sham-operated FVB/N mice of both sexes were subjected to positron emission tomography (PET) and cardiac magnetic resonance (CMR) imaging at the age of 4 (young cohort) and 20 (aged cohort) months (total n=123, 55% females). Following tail-vein injection of [11C]meta-hydroxynorephedrine ([11C]mHED), a widely used PET probe in preclinical and clinical assessment of cardiac sympathetic integrity, animals were scanned and cardiac sympathetic outflow was derived from myocardial [11C]mHED uptake. Cardiac parameters including LV volumes and left ventricular ejection fraction (LVEF) were obtained from electrocardiogram (ECG)-gated CMR imaging.

Results and discussion

A significant increase of LVEF was observed in aging females (p=0.012, Figure 1), but not in males. The latter was not associated with a higher cardiac output, and was a consequence of reduced LV end-systolic volumes (p=0.008), unveiling a substantial reduction of size in the aging female heart. As this age-dependent observation was not present in gonadectomized animals (p=0.414), the lack of growth-stimulating estrogen might account for reduction of cardiac size in aging females. Thus, despite a significantly heightened body weight, female heart size is reduced with age. Accordingly, sufficient cardiac output was maintained via increased heart rate (p=0.005) and cardiac sympathetic activity (p=0.040, Figure 1). Gonadectomy accelerated age-dependent changes in LV morphology and function in female mice. While sex hormone deprivation blunted cardiac sympathetic activity and norepinephrine levels in male mice, an opposite trend was observed in females.

Conclusion

Despite increasing body weight with age, aged female and male hearts maintain a stable circulatory blood supply, however, by distinct mechanisms. While the “shrinking” female heart requires an increased heart rate and cardiac sympathetic activity to compensate for smaller ventricular volumes, aging males maintain cardiac size. Importantly, sex hormone deprivation at a young age accelerates age-dependent changes in LV morphology and function in female mice, but not in male mice. The increased sympathetic activity reflects a higher stress level in aged females that might expose them to a higher cardiac vulnerability at postmenopausal age.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation; Swissheart Foundation

The Teacher-Learner Contract (TLC): An Objectives-Based Checklist for Surgical Shadowing

OBJECTIVE

A lack of structure and communication in physician shadowing experiences may prevent medical students from accruing its potential benefits. In this study, we evaluated the use of an objectives-based surgical shadowing teacher-learner contract (TLC) on the outcomes of shadowing experiences.

DESIGN

Cross-sectional study with 30 unique student-surgeon pairs who participated in a 1-time shadowing experience between December 2016 and May 2017.

SETTING

Eight hospitals and clinics in Metro Vancouver, British Columbia, Canada.

PARTICIPANTS

A convenience sample of preclinical medical students attending University of British Columbia and local surgeons from a variety of specialties were recruited by email. A random sample of 30 students was selected from a pool of interested students.

RESULTS

Twenty-eight students and 18 surgeons completed the study. In general, students and surgeons reported that the TLC focused learning and improved communication between teachers and learners. Students also commented that using the TLC prompted them to reflect on their goals and consider how the shadowing experience might contribute to their overall medical education. Both students and surgeons found benefit in using the checklist (mean 3.5 ± 0.75 and mean 3.8 ± 1.1, respectively, where 1 was not useful and 5 was very useful). All participants rated the TLC as easy to use (mean 1.429 ± 1.271 and mean 1.333 ± 0.686, respectively, where 1 was not difficult and 5 was very difficult), and 80% of respondents said they would use the tool again. Participants who benefited the most were students with limited surgical shadowing experience and surgeons with less experience teaching preclerkship students.

CONCLUSIONS

This study demonstrates that an objectives-based learning contract like the TLC can facilitate meaningful shadowing experiences for teachers and learners and may have longitudinal educational benefits. However, widespread implementation will require institutional support of this concept.

Enhanced recovery after surgery in colorectal surgery: Impact of protocol adherence on patient outcomes

STUDY OBJECTIVES

There is growing evidence internationally to support Enhanced Recovery After Surgery (ERAS) pathways. The impact of pathway compliance and the relative importance of individual components, however, remains less clear. Our institution implemented a multimodal ERAS protocol for elective colorectal surgery in November 2013. The objectives of this study were to investigate the impact of the introduction of the pathway, the relationship between pathway adherence and patient outcomes, and the relative importance of individual components.

DESIGN

This was a single-center, observational cohort study of elective colorectal surgical patients.

SETTING

A tertiary care and academic teaching hospital in Canada.

PATIENTS

Prospective data was collected from 495 consecutive major colorectal surgical patients following the ERAS launch. Retrospective data was also collected from a pre-ERAS cohort of 99.

MEASUREMENTS

Adherence to 12 ERAS components were measured, along with American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP®) defined patient complications and hospital length of stay (LOS). Post-ERAS patients were divided in to two groups: high compliance (≥75% process adherence) and low compliance (<75% adherence). Outcomes were compared between groups.

MAIN RESULTS

There was a significant reduction in both complication rate (31.5% vs 14.6%; p ≤0.05) and hospital mean LOS (10.1 vs 6.9 days; p ≤0.05) following introduction of the ERAS pathway. The high adherence group had a shorter mean LOS (5.7 vs 8.6 days; p ≤0.01) and lower rate of complications (11.2% vs 19.6%; p = 0.02) compared with the low compliance group.

CONCLUSIONS

Higher adherence to the standardized ERAS protocol was associated with improved patient outcomes, including reduced pulmonary complications. The cause-effect relationship is complex and likely influenced by confounding factors. Our data provides feedback to aid ongoing innovation of our pathway locally and adds to the growing body of evidence supporting the value of ERAS in general.

An overview of CEST MRI for non-MR physicists

The search for novel image contrasts has been a major driving force in the magnetic resonance (MR) research community, in order to gain further information on the body’s physiological and pathological conditions.

Chemical exchange saturation transfer (CEST) is a novel MR technique that enables imaging certain compounds at concentrations that are too low to impact the contrast of standard MR imaging and too low to directly be detected in MRS at typical water imaging resolution. For this to be possible, the target compound must be capable of exchanging protons with the surrounding water molecules. This property can be exploited to cause a continuous buildup of magnetic saturation of water, leading to greatly enhanced sensitivity.

The goal of the present review is to introduce the basic principles of CEST imaging to the general molecular imaging community. Special focus has been given to the comparison of state-of-the-art CEST methods reported in the literature with their positron emission tomography (PET) counterparts.

Why Canada needs networks to provide rural surgical care, including family doctors with essential surgical skills

SUMMARY

Time is long overdue for action to improve rural surgical services in Canada. In this issue of CJS, a proposed curriculum for the provision of enhanced surgical skills (ESS) to rural family physicians offers an opportunity to fortify a seamless network of high-quality surgical care for rural Canada. It is supported and enhanced by the best available evidence and measured advice from specialists and generalists alike. Publication of this curriculum proposal provides for essential dialogue with general surgeons. We discuss why we must play an active role in the development, teaching and evaluation of ESS, or we will have minimal influence and limited grounds on which to criticize its outcome or celebrate the opportunity of success it promises.

Fluorescent cholangiography in laparoscopic cholecystectomy: the initial Canadian experience

BACKGROUND

Bile duct injury remains a worrisome complication of laparoscopic cholecystectomy. Indocyanine Green (ICG) fluorescent cholangiography (FC) is a new approach that facilitates real-time intraoperative identification of biliary anatomy. This technology is hoped to improve the safety of dissection within Calot's triangle.

METHOD

Demographics, intraoperative details, and subjective surgeon data were recorded for elective cholecystectomy cases involving ICG. Goals were to identify rates of bile duct identification, and assess the perceived benefit of the device.

RESULTS

ICG was used in 12 biliary cases in Canada. Visualization rates of the cystic and common bile ducts were 100% and 83%, respectively. Also, 83% of surgeons felt that FC incorporated smoothly into the operation. No complications have been related to the technology.

CONCLUSIONS

FC allows noninvasive real-time visualization of the extrahepatic biliary tree. This novel technique has received positive feedback in its initial Canadian use and will likely be a durable adjunct for minimally invasive surgery.

Hybrid microPET imaging for dosimetric applications in mice: improvement of activity quantification in dynamic microPET imaging for accelerated dosimetry applied to 6-[18 F]fluoro-L-DOPA and 2-[18 F]fluoro-L-tyrosine

PURPOSE

Dynamic microPET imaging has advantages over traditional organ harvesting, but is prone to quantification errors in small volumes. Hybrid imaging, where microPET activities are cross-calibrated using post scan harvested organs, can improve quantification. Organ harvesting, dynamic imaging and hybrid imaging were applied to determine the human and mouse radiation dosimetry of 6-[18 F]fluoro-L-DOPA and 2-[18 F]fluoro-L-tyrosine and compared.

PROCEDURES

Two-hour dynamic microPET imaging was performed with both tracers in four separate mice for 18 F-FDOPA and three mice for 18 F-FTYR. Organ harvesting was performed at 2, 5, 10, 30, 60 and 120 min post tracer injection with n = 5 at each time point for 18 F-FDOPA and n = 3 at each time point for 18 F-FTYR. Human radiation dosimetry projected from animal data was calculated for the three different approaches for each tracer using OLINDA/EXM. S-factors for the MOBY phantom were used to calculate the animal dosimetry.

RESULTS

Correlations between dose estimates based on organ harvesting and imaging was improved from r = 0.997 to r = 0.999 for 18 F-FDOPA and from r = 0.985 to r = 0.996 (p < 0.0001 for all) for 18 F-FTYR by using hybrid imaging.

CONCLUSION

Hybrid imaging yields comparable results to traditional organ harvesting while partially overcoming the limitations of pure imaging. It is an advantageous technique in terms of number of animals needed and labour involved.

Joint position paper on rural surgery and operative delivery

Our professional organizations have prepared this paper as part of an integrated, multidisciplinary plan to ensure the availability of well-trained practitioner teams to sustain safe, effective and high-quality rural surgical and operative delivery services. Without these robust local (or nearby) surgical services, sustaining rural maternity care is much more difficult. This paper describes the "network model" as a health human resources solution to meet the surgical needs, including operative delivery, of rural residents; outlines necessary policy directions for achieving this solution; and poses a series of enabling recommendations.

Quantitative cerebral perfusion imaging in children and young adults with Moyamoya disease: comparison of arterial spin-labeling-MRI and H(2)[(15)O]-PET

BACKGROUND AND PURPOSE

Cerebral perfusion assessment is important in the preoperative evaluation and postoperative follow-up of patients with Moyamoya disease. The objective of this study was to evaluate the correlation of quantitative CBF measurements performed with arterial spin-labeling-MR imaging and H2[(15)O]-PET in children and young adults with Moyamoya disease.

MATERIALS AND METHODS

Thirteen children and young adults (8 female patients; age, 9.7 ± 7.1 years; range, 1-23 years) with Moyamoya disease underwent cerebral perfusion imaging with H2[(15)O]-PET (Discovery STE PET/CT, 3D Fourier rebinning filtered back-projection, 128 × 128 × 47 matrix, 2.34 × 2.34 × 3.27 mm(3) voxel spacing) and arterial spin-labeling (3T scanner, 3D pulsed continuous arterial spin-labeling sequence, 32 axial sections, TR = 5.5 seconds, TE = 25 ms, FOV = 24 cm, 128 × 128 matrix, 1.875 × 1.875 × 5 mm(3) voxel spacing) within less than 2 weeks of each other. Perfusion of left and right anterior cerebral artery, MCA, and posterior cerebral artery territories was qualitatively assessed for arterial spin-labeling-MR imaging and H2[(15)O]-PET by 2 independent readers by use of a 3-point-Likert scale. Quantitative correlation of relative CBF with cerebellar normalization between arterial spin-labeling-MR imaging and H2[(15)O]-PET was evaluated in a volume-based approach for each vascular territory after 3D image coregistration.

RESULTS

Interreader agreement was good (κ = 0.67-0.69), and strong and significant correlations were found between arterial spin-labeling-MR imaging and H2[(15)O]-PET for both qualitative perfusion scoring (ρ = 0.77; P < .001) and quantitative perfusion assessment of relative CBF with cerebellar normalization (r = 0.67, P < .001).

CONCLUSIONS

In children and young adults with Moyamoya disease, quantitative evaluation of CBF is possible with the use of arterial spin-labeling-MR imaging without ionizing radiation or contrast injection with a good correlation to H2[(15)O]-PET after cerebellar normalization.

Pancreatic β-cell prosurvival effects of the incretin hormones involve post-translational modification of Kv2.1 delayed rectifier channels

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the major incretin hormones that exert insulinotropic and anti-apoptotic actions on pancreatic β-cells. Insulinotropic actions of the incretins involve modulation of voltage-gated potassium (Kv) channels. In multiple cell types, Kv channel activity has been implicated in cell volume changes accompanying initiation of the apoptotic program. Focusing on Kv2.1, we examined whether regulation of Kv channels in β-cells contributes to the prosurvival effects of incretins. Overexpression of Kv2.1 in INS-1 β-cells potentiated apoptosis in response to mitochondrial and ER stress and, conversely, co-stimulation with GIP/GLP-1 uncoupled this potentiation, suppressing apoptosis. In parallel, incretins promoted phosphorylation and acetylation of Kv2.1 via pathways involving protein kinase A (PKA)/mitogen- and stress-activated kinase-1 (MSK-1) and histone acetyltransferase (HAT)/histone deacetylase (HDAC). Further studies demonstrated that acetylation of Kv2.1 was mediated by incretin actions on nuclear/cytoplasmic shuttling of CREB binding protein (CBP) and its interaction with Kv2.1. Regulation of β-cell survival by GIP and GLP-1 therefore involves post-translational modifications (PTMs) of Kv channels by PKA/MSK-1 and HAT/HDAC. This appears to be the first demonstration of modulation of delayed rectifier Kv channels contributing to the β-cell prosurvival effects of incretins and of 7-transmembrane G protein-coupled receptor (GPCR)-stimulated export of a nuclear lysine acetyltransferase that regulates cell surface ion channel function.

Suppression of p38 MAPK and JNK via Akt-mediated inhibition of apoptosis signal-regulating kinase 1 constitutes a core component of the beta-cell pro-survival effects of glucose-dependent insulinotropic polypeptide

Glucose-dependent insulinotropic polypeptide (GIP) potentiates glucose-stimulated insulin secretion, insulin biosynthesis, and beta-cell proliferation and survival. In previous studies GIP was shown to promote beta-cell survival by modulating the activity of multiple signaling modules and regulating gene transcription of pro- and anti-apoptotic bcl-2 family proteins. We have now evaluated the mechanisms by which GIP regulates the dynamic interactions between cytoplasmic bcl-2 family members and the mitochondria in INS-1 cells during apoptosis induced by treatment with staurosporine (STS), an activator of the mitochondria-mediated apoptotic pathway. STS induced translocation of bad and bimEL, activation of mitochondrial bax, release of mitochondrial cytochrome c, cleavage of caspase-3, and apoptosis. Each response was significantly diminished by GIP. Using selective enzyme inhibitors, overexpression of dominant-negative Akt, and Akt siRNA, it was demonstrated that GIP promoted beta-cell survival via Akt-dependent suppression of p38 MAPK and JNK and that combined inhibition was sufficient to explain the entire pro-survival responses to GIP during STS treatment. This signaling pathway also explained the pro-survival effects of GIP on INS-1 cells exposed to two other promoters of stress: thapsigargin (endoplasmic reticulum stress) and etoposide (genotoxic stress). Importantly, we discovered that GIP suppressed p38 MAPK and JNK via Akt-mediated changes in the phosphorylation state of the apoptosis signal-regulating kinase 1 in INS-1 cells and human islets, resulting in inhibition of its activity. Inhibition of apoptosis by GIP is therefore mediated via a key pathway involving Akt-dependent inhibition of apoptosis signal-regulating kinase 1, which subsequently prevents the pro-apoptotic actions of p38 MAPK and JNK.

A Novel Mechanism for the Suppression of a Voltage-gated Potassium Channel by Glucose-dependent Insulinotropic Polypeptide

The mechanisms involved in glucose regulation of insulin secretion by ATP-sensitive (K(ATP)) and calcium-activated (K(CA)) potassium channels have been extensively studied, but less is known about the role of voltage-gated (K(V)) potassium channels in pancreatic beta-cells. The incretin hormone, glucose-dependent insulinotropic polypeptide (GIP) stimulates insulin secretion by potentiating events underlying membrane depolarization and exerting direct effects on exocytosis. In the present study, we identified a novel role for GIP in regulating K(V)1.4 channel endocytosis. In GIP receptor-expressing HEK293 cells, GIP reduced A-type peak ionic current amplitude of K(V)1.4 via activation of protein kinase A (PKA). Using mutant forms of K(V)1.4 with Ala-Ser/Thr substitutions in a potential PKA phosphorylation site, C-terminal phosphorylation was shown to be linked to GIP-mediated current amplitude decreases. Proteinase K digestion and immunocytochemical studies on mutant K(V)1.4 localization following GIP stimulation demonstrated phosphorylation-dependent rapid endocytosis of K(V)1.4. Expression of K(V)1.4 protein was also demonstrated in human beta-cells; GIP treatment resulting in similar decreases in A-type potassium current peak amplitude to those in HEK293 cells. Transient overexpression in INS-1 beta-cells (clone 832/13) of wild-type (WT) K(V)1.4, or a T601A mutant form resistant to PKA phosphorylation, resulted in reduced glucose-stimulated insulin secretion; WT K(V)1.4 overexpression potentiated GIP-induced insulin secretion, whereas this response was absent in T601A cells. These results strongly support an important novel role for GIP in regulating K(V)1.4 cell surface expression and modulation of A-type potassium currents, which is likely to be critically important for its insulinotropic action.

A combination of two common thrombomodulin gene variants (-1208-1209TTdelTT and A455V) influence risk of coronary heart disease: a prospective study in men

In a previous case control study of myocardial infarction (MI), we identified risk associated with the combination of two variants in the thrombomodulin (TM) gene (-1208-1209TTdelTT and A455V) and an interaction with increased body mass index (BMI). The rare alleles at these two common variant sites in the TM gene occur in most individuals on the same allele (V/delTT) and are in strong linkage disequilibrium (Delta=0.67, P <0.0005). We have extended these findings in a prospective study of 2700 UK middle age men; the second Northwick Park Heart Study (NPHSII), in which 227 coronary heart disease (CHD) events have been reported to date. Risk was analysed by tertile of BMI, systolic blood pressure (SBP) and triglyceride. The strongest risk for the V/delTT haplotype was in the mid- and top-tertile of triglyceride; RR 1.95 (CI 1.12-3.40) and 1.77 (CI 1.02-3.09), respectively, compared to non-carriers in the lowest tertile (after adjusting for age, practice, smoking, SBP, BMI; interaction P=0.016). No significant risk was identified for increased triglyceride levels in those with the common TM haplotype. There was a suggestion for greater inflammatory response (C-reactive protein levels, CRP) in those with V/delTT compared to those with the common allele, as triglyceride levels increased. Overall, these findings may suggest that the common TM allele confers protection against the adverse CHD effect of either plasma triglyceride-containing lipoproteins, or the underlying atherosclerotic mechanism of the metabolic syndrome, and that this process is defective in carriers of V/delTT.

Dermoid cyst of the maxillary sinus

Dermoid cysts are rare developmental teratomatous lesions composed of ectodermally derived stratified squamous epithelium and mesodermally derived skin adnexal structures. As part of the teratomatous lesion group, dermoid cysts are related to teratoid cysts, true teratomas, and epignathi. Although several theories have been postulated, the pathogenesis of dermoid cysts, and teratomatous lesions in general, is unclear. Most commonly affecting sites within the head and neck, dermoid cysts may be found in the frontotemporal/lateral brow area, central nasal area, oral cavity, lateral neck, and other sites. We present what is believed to be the first reported case arising within the maxillary sinus and briefly discuss the possible pathogenesis.

Differential expression of GAD65 and GAD67 in human, rat, and mouse pancreatic islets

The smaller form of the autoantigen glutamic acid decarboxylase, GAD65 (formerly the 64,000 M(r) autoantigen), is a major target of humoral autoimmunity in type I diabetes. Human autoantisera have been used extensively to characterize the GAD65 antigen in both rat and human islets, but the protein has escaped detection in mouse islets. We have now analyzed the expression of GAD65 and GAD67, the larger glutamic acid decarboxylase protein, in human, rat, and mouse islets of Langerhans and brain, using human monoclonal islet cell autoantibodies, human autoantisera, and experimentally raised antibodies to glutamic acid decarboxylase. Human monoclonal autoantibodies and experimentally raised antibodies reacted with mouse GAD65 produced in a baculovirus expression system by Western blotting and immunoprecipitation and with GAD65 in mouse brain by immunohistochemistry but failed to detect GAD65 in mouse islets by the latter two methods. However, analysis of mouse islets by Western blotting technique, using the most sensitive experimentally raised antibody, showed that mouse islets express both GAD65 and GAD67 but at levels that are severalfold lower than those in mouse brain or in human and rat islets. Furthermore, both human and rat islets predominantly express GAD65, whereas GAD67 is the major glutamic acid decarboxylase protein in mouse islets. Human islets are significantly distinct from mouse and rat islets and from brain because they only express GAD65, which is consistent with the predominant role of this form as a target of autoantibodies associated with beta-cell destruction in humans. Human as well as rat islet GAD65 are found in both membrane-bound and soluble forms. The low level of glutamic acid decarboxylase expression in mouse islets compared with human and rat islets is likely to have implications for both the development of tolerance to glutamic acid decarboxylase as well as the homing of glutamic acid decarboxylase-specific lymphocytes to the mouse beta-cell. In this context, the results suggest 1) that the mouse is ideal for studies of the consequences of an expression of high levels of glutamic acid decarboxylase in the beta-cell from a transgene and 2) that the rat may be better suited than the mouse for development of nontransgenic animal models of glutamic acid decarboxylase autoimmunity by immunization.

Quantitative analysis of islet glutamic acid decarboxylase p64 autoantibodies in insulin-dependent diabetes mellitus

Autoantibodies against the beta-cell M(r) 64,000 protein (p64), recently identified as an isoform of glutamic acid decarboxylase (GAD), are prevalent in patients with insulin-dependent diabetes mellitus (IDDM). Dog islets were found to represent an abundant source of native p64 allowing the study of antigen-antibody interactions in IDDM. A quantitative, standardized assay for p64 antibodies based on dog islets was developed and evaluated. Utilizing dog and human islets the p64 antibodies were detected in 17/19 (89%) new onset 15-32-year-old patients, compared to 15/19 (79%) in a rat islet assay. ICA were detected in 15/19 (79%) patients and correlated with the presence of p64 antibodies (rs = 0.59, P < 0.004) but not with age at onset, sex, or C-peptide levels. Sensitivity therefore is improved with the dog islet p64 antibody assay which will allow future studies requiring native p64 antigen in larger quantities are possible based on our findings.

Risk for developing type 1 (insulin-dependent) diabetes mellitus and the presence of islet 64K antibodies

First-degree relatives of Type 1 (insulin-dependent) diabetic patients are at increased risk for developing clinical diabetes. The presence of islet cell or insulin autoantibodies further identifies relatives at greater risk, but not all immunologic-marker-positive relatives progress to disease. Beta-cell dysfunction, however, seems to be more prevalent than clinical Type 1 diabetes, since stable subclinical pancreatic Beta-cell dysfunction may occur. Antibodies against a Mr 64,000 (64K) islet Beta-cell protein, identified as glutamic acid decarboxylase, have been reported both at and several years prior to the clinical onset of Type 1 diabetes. We measured 64K antibodies in first-degree relatives with varying degrees of Beta-cell dysfunction and risk for subsequent Type 1 diabetes to determine whether 64K antibodies improve the predictive power of islet cell antibodies and/or insulin autoantibodies. In the Seattle Family Study first-degree relatives of Type 1 diabetic patients are followed prospectively using detailed Beta-cell function tests, insulin sensitivity, quantitative evaluation of islet cell antibodies and fluid phase assay insulin autoantibodies. 64K antibodies were measured using dog islets. Relatives were selected, based on Beta-cell function to represent individuals at high (n = 6) and low (n = 30) risk for subsequent Type 1 diabetes. The 30 low-risk individuals followed-up for 78 months, had stable Beta-cell function, and six (20%) were negative for all autoantibodies, ten (33%) were positive for insulin autoantibodies, 16 (53%) were islet cell antibody positive while six (20%) were positive for 64K antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Revelation of specificity of 64K autoantibodies in IDDM serums by high-resolution 2-D gel electrophoresis. Unambiguous identification of 64K target antigen

Antibodies in serums from newly diagnosed insulin-dependent (type I) diabetes mellitus (IDDM) patients and individuals experiencing early phases of beta-cell destruction specifically immunoprecipitate a minor pancreatic islet cell membrane protein of 64,000 Mr (64K). In this report, we demonstrate the use of two-dimensional (2-D) gel electrophoresis to unambiguously identify the 64K antigen. By nonequilibrium pH-gradient gel electrophoresis in the first dimension and sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the second dimension, the 64K protein separates into two components, designated alpha and beta, that differ in size but display identical charge heterogeneity. The high resolution of the 2-D method efficiently separates the 64K components from background proteins in immunoprecipitates from crude detergent lysates of islets. The background proteins were identified as major cellular proteins carried nonspecifically through the immunoprecipitation procedure. The high affinity and specificity of the 64K autoantibodies were demonstrated by the exclusive and greater than 1000-fold purification of this minor protein by immunoprecipitation with IDDM serums. The 2-D analyses did not reveal additional proteins specifically immunoprecipitated by IDDM serums, suggesting that the 64K protein is the only protein antigen specifically and consistently recognized by IDDM autoantibodies in the relatively stringent conditions of immunoprecipitation. Moreover, the 2-D analyses demonstrate that purification of membrane protein fractions from both human and rat islets before the immunoprecipitation efficiently removes background proteins and substantially increases the specificity of 64K autoantibody measurements by traditional methods.