Relationship between body weight change and glycaemic control with tirzepatide treatment in people with type 2 diabetes: A post hoc assessment of the SURPASS clinical trial programme

AIM

To assess the relationship between HbA1c and body weight reductions with tirzepatide treatment (5, 10 or 15 mg).

MATERIALS AND METHODS

HbA1c and body weight data at 40 weeks (SURPASS-1, -2 and -5) and 52 weeks (SURPASS-3 and -4) were analysed by trial.

RESULTS

Across the SURPASS clinical trials, HbA1c reductions from baseline were observed in 96%-99%, 98%-99% and 94%-99% of participants treated with tirzepatide 5, 10 and 15 mg, respectively. Moreover, 87%-94%, 88%-95% and 88%-97% of participants, respectively, experienced weight loss associated with HbA1c reductions. Statistically significant associations (correlation coefficients ranging from 0.1438 to 0.3130 across studies; P ≤ .038) between HbA1c and body weight changes were observed with tirzepatide in SURPASS-2, -3, -4 (all doses) and -5 (tirzepatide 5 mg only).

CONCLUSIONS

In this post hoc analysis, consistent reductions in both HbA1c and body weight were observed in most participants treated with tirzepatide at doses of 5, 10 or 15 mg. A statistically significant but modest association between HbA1c and body weight change was observed in SURPASS-2, SURPASS-3 and SURPASS-4, suggesting that both weight-independent and weight-dependent mechanisms are responsible for the tirzepatide-induced improvement in glycaemic control.

Risk of clinically relevant hypoglycaemia in patients with type 2 diabetes self-titrating insulin glargine U-100

AIMS

We evaluated risk factors for clinically relevant hypoglycaemia (blood glucose <3 mmol/L) in patients with type 2 diabetes during insulin glargine self-titration. Data were from two clinical trials in which patients were able to improve glycaemic control by self-titration of insulin glargine using a simple algorithm.

MATERIALS AND METHODS

We performed post hoc analyses of pooled treatment groups from each of two Phase 3 studies comparing LY2963016 with LANTUS: ELEMENT-2 (double-blind) and ELEMENT-5 (open label). Clinically relevant hypoglycaemia was analysed by category of HbA1c (<7%, 7%-8.5%, >8.5%) at Week 12 (titration period) and at Week 24 (overall study), and by subgroups of age (<65, ≥65 years) and previous insulin use (naïve or not).

RESULTS

In the ELEMENT-2 study (N = 756), there were no overall differences in rate or incidence of hypoglycaemia among HbA1c categories. In the ELEMENT-5 study (N = 493), patients with HbA1c greater than 8.5% had a lower rate and incidence of hypoglycaemia throughout the study compared to those in the lower HbA1c categories. In both studies, patients 65 years of age or older, compared to those less than 65 years, had a higher rate and incidence of hypoglycaemia during the titration phase, had lower baseline HbA1c, and experienced smaller increases in dose, with no differences in HbA1c post baseline. The rate and incidence of hypoglycaemia was similar between naïve patients and patients previously using basal insulin, across all levels of glycaemic control. With the exception of the older subgroup, hypoglycaemia rates were similar during titration and maintenance periods.

CONCLUSION

Our results support broader use of self-titration algorithms for patients with type 2 diabetes.

Adherence to Basal Insulin Therapy Among People with Type 2 Diabetes: A Retrospective Cohort Study of Costs and Patient Outcomes

INTRODUCTION

This research compares costs, resource utilization, and complications between adherent and nonadherent patients over the 3-year period post initiation on basal insulin therapy.

METHODS

The study utilized the US-based Truven Health MarketScan^® Research Databases from 2011 through 2015. Adults aged 18 years or older and identified with type 2 diabetes (T2D) who initiated therapy on basal insulin in 2012 were included. Patients were excluded if they were pregnant, filled their index basal insulin prescription via mail order, or were not continuously insured from 1 year before through 3 years following initiation of treatment with basal insulin. Instrumental variables were used to control for selection bias, and multivariable analyses were used to examine the associations between adherence to basal insulin therapy and costs, resource utilization, and acute complications.

RESULTS

A total of 21,363 individuals were included in the study. Three years after initiating therapy on basal insulin, patients who were adherent over time to basal insulin treatment therapy (33.8% of patients) had significantly higher diabetes-related drug costs. However, patients' adherence was associated with significantly lower diabetes-related outpatient, acute care, and total costs. Results for all-cause costs were similar. Adherent patients also had significantly fewer all-cause and diabetes-related hospitalizations and emergency room visits and were significantly less likely to be diagnosed with an acute complication.

CONCLUSIONS

Results of this study illustrate that despite higher drug costs, there are disease-specific and all-cause cost offsets and improved patient outcomes associated with adherence to basal insulin therapy for people with T2D.

FUNDING

Eli Lilly and Company.

Introduction of biosimilar insulins in Europe

Regulatory approval of the first biosimilar insulin in Europe, LY2963016 insulin glargine (Abasaglar^® ), in 2014 expanded the treatment options available to people with diabetes. As biosimilar insulin products come to market, it is important to recognize that insulin products are biologicals manufactured through complex biotechnology processes, and thus biosimilar insulins cannot be considered identical to their reference products. Strict regulatory guidelines adopted by authorities in Europe, the USA and some other countries help to ensure that efficacy and safety profiles of biosimilar insulins are not meaningfully different from those of the reference products, preventing entry of biological compounds not meeting quality standards and potentially affecting people's glycaemic outcomes. This review explains the concept of biosimilar medicines and outlines regulatory requirements for registration of biosimilar insulins in Europe, which is illustrated by the successful development of LY2963016 insulin glargine and MK-1293 insulin glargine (Lusduna^® ). Preclinical and clinical comparative studies of the biosimilar insulin glargine programmes include in vitro bioassays for insulin and insulin-like growth factor 1 receptor binding, assessment of in vitro biological activity, evaluation of pharmacokinetic/pharmacodynamic profiles in phase I studies and assessment of long-term safety and efficacy in phase III studies. The emergence of biosimilar insulins may help broaden access to modern insulins, increase individualized treatment options and reduce costs of insulin therapy.

Biosimilar insulins: a European perspective

Biosimilar insulins are likely to enter clinical practice in Europe in the near future. It is important that clinicians are familiar with and understand the concept of biosimilarity and how a biosimilar drug may differ from its reference product. The present article provides an overview of biosimilars, the European regulatory requirements for biosimilars and safety issues. It also summarizes the current biosimilars approved in Europe and the key clinical issues associated with the use of biosimilar insulins.

Initiation and gradual intensification of premixed insulin lispro therapy versus Basal {+/-} mealtime insulin in patients with type 2 diabetes eating light breakfasts

OBJECTIVE

We compared two strategies initiating and intensifying insulin treatment and tested for noninferiority of premixed insulin to basal ± mealtime insulin analog in patients eating light breakfasts.

RESEARCH DESIGN AND METHODS

This randomized, open-label, 48-week study compared two algorithms. Up to three injections of insulin lispro mix 25 and/or insulin lispro mix 50 (premix; premixed insulin lispro) or basal insulin glargine plus up to three injections of insulin lispro (basal+; glargine + insulin lispro) were used in type 2 diabetic patients uncontrolled with oral antihyperglycemic medication and consuming <15% daily calories at breakfast. The hypothesis was to test noninferiority of premix to basal+ for glycemic control measured by HbA1c after 48 weeks, assessed using ANCOVA with a 0.4% margin.

RESULTS

Patients (n = 344; 176 [51%] females; mean [SD] age 54.3 [8.8] years; BMI 29.4 [4.6] kg/m(2); baseline HbA1c 9.02 [0.97]%) were randomized to premix (n = 171) or basal+ (n = 173). In the per-protocol analysis (n = 230), least squares means (95% CI) end point HbA1c were 7.40% (7.15-7.65) and 7.55% (7.27-7.82) in respective arms. Between-treatment difference was -0.14% (-0.42 to 0.13), with noninferiority met. Significantly more patients in premix achieved HbA1c targets of <7.0% compared with basal+ (48.2 vs. 36.2%; P = 0.024). Self-monitored blood glucose profiles, body weight changes, total insulin doses, and overall hypoglycemia (65 vs. 60%) were similar in premix and basal+ (P = 0.494), except nocturnal episodes (34.3 vs. 23.7%; P = 0.018) were more common in premix.

CONCLUSIONS

Both intensive insulin strategies improved glycemic control; however, final HbA1c levels were seen above those achieved in previous treat-to-target trials, likely due to the inadequate insulin titrations and probably due to the complexity of tested insulin regimens. A higher percentage of patients achieved target HbA1c <7% with multiple premixed insulins, but this treatment resulted in more nocturnal hypoglycemia than a basal-bolus regimen.

Treatment outcomes after initiation of exenatide twice daily or insulin in clinical practice: 12-month results from CHOICE in six European countries

OBJECTIVE

The CHanges to treatment and Outcomes in patients with type 2 diabetes initiating InjeCtablE therapy (CHOICE) study assessed time to, and reasons for, significant treatment change after patients with type 2 diabetes (T2DM) initiated their first injectable glucose-lowering therapy (exenatide twice daily [BID] or insulin) in routine clinical practice, and these patients' clinical outcomes, in six European countries. This paper reports interim data from the first 12 months of the study.

RESEARCH DESIGN AND METHODS

CHOICE (NCT00635492) is a prospective, noninterventional, observational study. Clinical data were collected at initiation of first injectable therapy and after approximately 3, 6, and 12 months.

RESULTS

Of 2497 patients enrolled in CHOICE, 1096 in the exenatide BID and 1239 in the insulin cohorts had ≥1 post-baseline assessment and were included in this analysis. Overall, 32.2% of the exenatide BID cohort and 29.1% of the insulin cohort (Kaplan-Meier estimates) had significant treatment change during the first 12 months, most commonly discontinuing injectable therapy or adding new T2DM therapy, respectively. Glycemic control improved in both cohorts, but weight loss occurred only in the exenatide BID cohort (mean change -3.3 kg). Hypoglycemia occurred in 13.2% of the exenatide BID cohort and 28.6% of the insulin cohort (82.8% and 55.6% of these patients, respectively, received sulfonylureas). The post hoc endpoint of glycated hemoglobin < 7%, no weight gain, and no hypoglycemia was attained at 12 months by 24.3% and 10.3% of patients who had data at 12 months and who were receiving exenatide BID and insulin, respectively.

CONCLUSION

About 30% of patients in CHOICE changed treatment in the first 12 months after initiation of first injectable therapy (exenatide BID or insulin). Overall, both cohorts achieved improved glycemic control, which was accompanied by a mean weight loss in the exenatide BID cohort.

Patients with Type 2 Diabetes Initiating Exenatide Twice Daily or Insulin in Clinical Practice: CHOICE Study

INTRODUCTION

Changes to Treatment and Outcomes in Patients with Type 2 Diabetes Initiating Injectable Therapy (CHOICE) is a European prospective, observational cohort study assessing time to, and factors associated with, a significant change in therapy after type 2 diabetes patients initiate their first injectable glucose-lowering therapy, and these patients' clinical outcomes over 24 months. The authors report baseline data and factors associated with the injectable treatment regimen.

METHODS

Demographic, clinical, and healthcare resource-use data were collected at initiation of injectable therapy and analyzed using univariate tests between cohorts and multivariate logistic regression analysis for treatment.

RESULTS

Overall, 1,177 patients initiated exenatide twice daily (b.i.d.) and 1,315 initiated insulin. Most patients were recruited by secondary-care physicians. Univariate analyses revealed statistically significant differences between the characteristics of patients who initiated exenatide b.i.d. and patients who initiated insulin. On multivariate analysis, higher body mass index [BMI; 5 kg/m(2) higher: odds ratio (OR) 2.10, 95% confidence intervals (CI) 1.84-2.40], lower glycated hemoglobin (HbA(1c); 1% higher: OR 0.77, 95% CI 0.69-0.86), and lower age (5 years older: OR 0.82, 95% CI 0.76-0.88) were the variables most strongly associated with increased probability of receiving exenatide b.i.d. (P < 0.0001). Patients initiating exenatide b.i.d. had a mean BMI of 35.3 ± 6.5 kg/m(2), HbA(1c) of 8.4 ± 1.4%, and age of 58 ± 10 years, compared with 29.7 ± 5.4 kg/m(2), 9.2 ± 1.9%, and 64 ± 11 years, respectively, in patients initiating insulin (P < 0.0001). Other characteristics significantly associated with exenatide b.i.d. initiation were "disinhibited eating" (Diabetes Health Profile-18), lower random blood glucose, less blood glucose self-monitoring, lower low-density lipoprotein cholesterol, and receipt of diet/exercise advice.

CONCLUSIONS

Patients who initiated exenatide b.i.d. were on average younger and more obese with lower HbA(1c) than those initiating insulin.

Efficacy and safety of prandial premixed therapy using insulin lispro mix 50/50 3 times daily compared with progressive titration of insulin lispro mix 75/25 or biphasic insulin aspart 70/30 twice daily in patients with type 2 diabetes mellitus: a randomized, 16-week, open-label study

BACKGROUND

Prandial premixed therapy 3 times daily has been proposed recently for type 2 diabetes mellitus (T2DM) patients who fail to achieve glycemic control with commonly used premixed insulin analogs, insulin lispro mix 75/25 (LM75/25) and biphasic insulin aspart 70/30 (BIAsp70/30) BID.

OBJECTIVE

The aim of this work was to compare the efficacy and safety of 3-times daily insulin lispro mix 50/50 (TID group) with progressive titration of twice-daily LM75/25 or BIAsp70/30 (BID group) administered along with metformin in T2DM patients.

METHODS

This was an open-label, 16-week, multicenter, randomized, parallel trial. End point glycosylated hemoglobin (HbA(1c)) was the primary efficacy measure; HbA(1c) reduction from baseline to end point, percentage of patients reaching target HbA(1c) (<7.0% and ≤6.5%), postprandial blood glucose (BG), and BG excursions after lunch were secondary measures. Safety was evaluated by collecting adverse events.

RESULTS

A total of 302 patients with mean (SD) age 57.7 (9.27) years, diabetes duration 11.2 (6.47) years, HbA(1c) 8.5% (1.23), fasting BG 184.0 (53.04) mg/dL, body weight 86.8 (14.79) kg, body mass index 31.7 (4.23) kg/m(2), and daily insulin dose ∼48 IU were randomized. No significant difference was observed in end point HbA(1c) between the 2 groups. Seven-point BG profiles showed lower fasting and postbreakfast BG in the BID group but lower postlunch BG in the TID group. Daily insulin dose change was similar in both groups, with more weight gain in the TID group (P = 0.0009). Overall hypoglycemic rates were similar in both groups, but nocturnal hypoglycemia was more frequent in the BID group (P = 0.0063).

CONCLUSIONS

In patients with T2DM who have not achieved adequate glycemic control with LM75/25 and BiAsp70/30 BID plus metformin and who are not candidates for basal bolus therapy, switching either to treatment with LM50/50 TID or to progressive titration of premix insulin analogs BID did not produce sufficient evidence of a difference of overall glycemic control between the 2 treatment groups. Short study duration and less intensive dose adjustments might have contributed to these results.

T cell interactions with extracellular matrix proteins in patients with thyroid-associated ophthalmopathy

Although thyroid-associated ophthalmopathy (TAO) is now generally accepted as an autoimmune inflammatory disorder of the extraocular muscles and the orbital connective tissue, its aetiopathogenesis remains poorly understood. Recent data indicate that impaired interactions between T cells and extracellular matrix (ECM) proteins may play an important role in development and maintaining of an inflammatory process. We report here results of the study focusing on interactions between T lymphocytes and collagen-I (Coll-I), collagen-IV (Coll-IV), fibronectin (FN), laminin (LM) in patients with TAO. Using a standard peripheral blood mononuclear cells (PBMC) proliferation assay, we observed a markedly enhanced T cell response to Coll-I in patients with active TAO (mean SI=4.5). The proliferatory response to Coll-I was significantly greater (Wilcoxon test; p < 0.001) than in normal subjects (mean SI=1.88), patients with stable TAO (mean SI=2.05) and patients with thyroid autoimmune diseases (AITD) without ophthalmopathy (mean SI=2.49). PBMC stimulation by Coll-I is likely to be antigen-dependent requiring engagement of the T cell receptor with collagen peptides, rather than mediated via integrins. The percentage of circulating CD29+ (beta1 integrin chain) T cells was not increased in patients with active TAO. Additionally in the assay of costimulation of CD3-mediated proliferation, we found that peripheral blood T cells from patients with TAO and AITD were costimulated only by FN. On the other hand a markedly enhanced costimulation of CD3-mediated proliferative responses by Coll-I, Coll-IV, FN and LM were observed in a retrobulbar T cell line. We conclude that abnormalities in T cell interactions with ECM proteins, especially Coll-I may play a role in the pathogenesis of TAO.

Role of the eye muscles in thyroid eye disease: identification of the principal autoantigens

Thyroid-associated ophthalmopathy (TAO) is a progressive orbital disorder associated with Graves' hyperthyroidism and, less often, Hashimoto's thyroiditis in which autoantibodies react with orbital antigens and lead to exophthalmos and eye muscle inflammation. Eye muscle (EM) membrane proteins initially reported as 55 and 64 kd are the best markers of ophthalmopathy. The "64-kd protein" is now shown to be the flavoprotein subunit of mitochondrial succinate dehydrogenase and to have a correct molecular weight of 67 kd. We have cloned a fragment of a novel eye muscle protein, which we call G2s, and sequenced 1.4 kb of the full length cDNA. G2s does not share any significant homologies with other reported proteins. The 5.9 kb G2s mRNA, that corresponds to a protein of approximately 220 kd, is expressed in EM, other skeletal muscle and thyroid, but not in other tissues tested. We have also cloned and sequenced a 63-kd eye muscle protein identified as the calcium binding protein calsequestrin. Antibodies against calsequestrin were found in 40% of patients with active ophthalmopathy, but in 0% of normal subjects. Finally, we have sequenced a 19 amino acid fragment of a 55-kd porcine eye muscle membrane protein that exactly matched porcine and human sarcalumenin, a 160-kd glycoprotein localized in the lumen of the longitudinal sarcoplasmic reticulum of the skeletal muscle fiber where it binds calcium. A 53-kd glycoprotein fragment of the molecule corresponds to the 55-kd protein. In a preliminary study, serum antibodies against purified sarcalumenin were detected in 40% of patients with active TAO of less than 1 year duration, but in no controls tested. We porpose that the primary autoantigen in TAO is G2s, which would also explain the association of ophthalmopathy with thyroid autoimmunity, and that antibodies against the intracellular proteins flavoprotein, calsequestrin, and sarcalumenin are secondary markers of an immune-mediated reaction in eye muscle in patients with thyroid autoimmunity.

Serum antibodies reactive with eye muscle antigens and the TSH receptor in a euthyroid subject who developed ophthalmopathy and Graves' hyperthyroidism

Serum antibodies reactive with eye muscle autoantigens, in particular a 64-kDa protein that is also expressed in the thyroid, and the TSH receptor, are associated with the ophthalmopathy that occurs in about 50% of patients with Graves' hyperthyroidism. We have had the opportunity to study a euthyroid, apparently normal, 35-year-old woman with a family history of thyroid autoimmunity and "colitis" but no clinical or biochemical evidence for thyroid disease or ophthalmopathy, who developed Graves' hyperthyroidism and ophthalmopathy together 18 months later. Serum taken when the patient was first seen was positive for antibodies reactive with (i) 9 different eye muscle proteins ranging in size from 15 to 130 kDa, notably those of 64, 55, and 50 kDa, by immunoblotting with eye muscle membranes, (ii) eye muscle and Müller's muscle cell membrane antigens in antibody-dependent cell-mediated cytotoxicity (ADCC), (iii) an eye muscle cytoplasmic antigen in indirect immunofluorescence, and (iv) the TSH receptor as measured in a radioreceptor binding inhibition assay. When she developed Graves' disease, serum concentration of antibodies to the 55-kDa protein had decreased from +2 to +/-, those reactive with other eye muscle antigens had not changed significantly, and TSH receptor antibodies had increased 3-fold. This case report suggests that antibodies reactive with eye muscle antigens and the TSH receptor are markers of the ophthalmopathy and able to predict its development in predisposed subjects. The significance of these findings needs to be confirmed in a prospective study of first-degree relatives of patients with thyroid-associated ophthalmopathy and patients with Graves' hyperthyroidism without eye signs.

Antibody-dependent cell-mediated cytotoxicity against orbital target cells in thyroid-associated ophthalmopathy and related disorders; close relationship between serum cytotoxic antibodies and parameters of eye muscle dysfunction

We have carried out tests for antibody-dependent cell-mediated cytotoxicity (ADCC) against extra ocular muscle (EOM), Müller's muscle, orbital fibroblasts and skeletal muscle in patients with thyroid-associated ophthalmopathy (TAO) and related eye disorders. Cytotoxicity was measured as lactate dehydrogenase (LDH) release and results expressed as % cytotoxicity. Tests were positive, with EOM cells, in 65% of patients with TAO, 75% with ocular myopathy, a variant of TAO in which periorbital inflammation is minimal, 50% with euthyroid Graves' disease defined as ophthalmopathy associated with subclinical thyroiditis and in 50% of patients with stable lid lag and retraction but no other signs of progressive ophthalmopathy, but in only 13% of patients with Graves' hyperthyroidism without ophthalmopathy, 10% with Hashimoto's thyroiditis and 14% of patients with other thyroid disorders. Tests were positive, with Müller's muscle cells, in 40% of patients with TAO, 25% with ocular myopathy, 40% with euthyroid Graves' disease, 44% with lid lag, 19% with Graves'hyperthyroidism, 50% with Hashimoto's thyroiditis and in 37.5% of patients with other thyroid disorders. When skeletal muscle cells were used as target, tests were positive in 13% of patients with TAO, 31% with lid lag, 25% with Graves' hyperthyroidism and in 29% of patients with Hashimoto's thyroiditis, but in no patient with euthyroid Graves' disease or other thyroid disorders. Tests were negative in all patients and normals tested when EOM-derived fibroblasts were used as targets in ADCC. A significant positive correlation between % cytotoxicity against EOM cells and the severity of the eye muscle dysfunction expressed as an eye muscle index, was observed in patients with TAO. There was a significant negative correlation between the duration of eye disease and % cytotoxicity against EOM cells, suggesting higher titers of cytotoxic antibodies in the early stages of TAO. There was no correlation between % cytotoxicity and serum level of anti-TSH receptor antibodies, measured in a radioreceptor assay. These findings suggest that autoimmunity against Müller's muscle may play a role in the pathogenesis of persistent lid lag and retraction. The nature of the EOM and Müller's muscle autoantigens recognized by cytotoxic antibodies in the serum of patients with TAO and related eye disorders is unknown.

Significance of tissue specific and tissue non specific autoimmune reactions of Graves' disease

The relationship between the many immunologic abnormalities demonstrated in the peripheral blood of patients with Graves' disease (GD) and the broad spectrum of clinical features with which patients may present has not yet been addressed in detail. In this review we examine the evidence to support the notion that GD could be considered a multi-system autoimmune disorder in which tissue damage is restricted to the thyroid gland, connective tissue of the skin and orbit, extra-ocular and other skeletal muscles and, possibly, the lacrimal glands. Apart from the well recognized reactions of autoantibodies and sensitized T lymphocytes with epitopes on the thyroid specific TSH receptor, thyroid peroxidase and thyroglobulin, in patients with hyperthyroidism, there is also good evidence for autoantibody and, to a lesser extent, T lymphocyte reactivity with several eye muscle, other skeletal muscle and connective tissue, antigens in patients with ophthalmopathy, systemic myopathy, dermopathy and acropachy. There is also some evidence for immunoreactivity against lacrimal gland antigens in patients with ophthalmopathy associated with other features of GD. There are, in addition, a variety of organ non-specific reactions in GD; antinuclear antibodies are detected in serum from about one-third of patients with hyperthyroidism and ophthalmopathy, while from 5% to 10% have antibodies reactive with several other ubiquitous tissue proteins. Cloned proteins which are autoantigenic in some patients with hyperthyroidism or Hashimoto's thyroiditis and ophthalmopathy include collagen XIII, nebulin, the calcium binding protein calmitine, and the Mac-II antigen. All antibodies reactive with eye muscle antigens, except the 64 kDa protein which is also expressed in the thyroid, cross react with the same, or a related, protein in other skeletal muscle. Future research should focus on the underlying mechanisms for this broad loss of tolerance to self antigens and the effect of environmental factors such as stress, radioiodine and viral infection of the thyroid gland and other target tissues, in precipitating disease.

Failure to demonstrate cell-mediated immunity to orbital tissue antigens and epitopic fragments of a 64 kDa protein in the majority of patients with thyroid-associated ophthalmopathy

We have studied a possible role of T cell sensitization to eye muscle antigens in patients with thyroid-associated ophthalmology (TAO). Peripheral blood mononuclear cell (PBMC) proliferation in response to crude porcine orbital tissue antigens, partially purified porcine eye muscle membrane proteins and predicted epitopic fragments of the recombinant 64 kDa protein 1D, was determined in patients with TAO and thyroid autoimmunity without eye disease. When membrane and cytosol fractions were used as antigen PBMC from 43% of patients with TAO but only 12.5% of normal subjects were responsive to a crude orbital connective tissue membrane fraction, although this difference was not significant. We were unable to demonstrate specific recognition of partially purified eye muscle membrane fractions; although most of the fractions tested were occasionally recognized by T cells from patients with ophthalmopathy, this was also the case for patients with autoimmune thyroid disease without ophthalmopathy and normal subjects. We did not clearly identify epitopic sequences within the 1D protein, most of the predicted peptides tested being recognized not only by T cells from a small proportion of patients with TAO, but also by those from some patients with autoimmune thyroid disease without ophthalmopathy and normal subjects. It is noteworthy however that approximately 22% of TAO patients, but no normal subjects, were positive to one or more of three peptides, suggesting that reactivity to the 1D protein may play a role in the pathogenesis of the eye disorder in some patients with TAO. The inconsistent and generally low T cell responses to crude and purified antigens noted in a few patients with TAO could be explained by low numbers of specifically sensitized lymphocytes in peripheral blood.

Should Graves' disease be considered a collagen disorder of the thyroid, skeletal muscle and connective tissue?

Graves' disease comprises hyperthyroidism, ophthalmopathy, pretibial myxedema and acropachy, which occur separately or in various combinations. We have used the indirect immunofluorescence test to investigate reactivity of sera from patients with autoimmune thyroid disorders with and without ophthalmopathy, with porcine extra ocular muscle (EOM) and control tissue substrates. Sera from 75% of patients with Graves' hyperthyroidism (GH) and ophthalmopathy, which we call thyroid-associated opthalmopathy (TAO), contained one or more antibodies reactive with EOM compared to 32% of those with GH without the eye disorder, 41% of patients with Hashimoto's thyroiditis (HT), and 16% of normals. Antibodies reactive with an EOM connective tissue antigen(s), seen as fluorescence of the interstitium and endomysium, were found in sera from 10% of patients with TAO and 16% of those with GH, but not from any patient with HT or normal subject. Similar patterns of connective tissue reactivity were also found in lacrimal gland, skeletal muscle, kidney and salivary gland. Antinuclear antibodies were detected in sera from 31% of patients with TAO, but from only 8% with HT, in no patient with GH and in only 3% of normal subjects. The most common pattern was a fine speckled fluorescence, found in 45% of sera, consistent with reactivity against the Sm antigen or nuclear RNP. The finding of a high prevalence of ANA and, less often, anti-connective tissue antibodies in patients with thyroid autoimmunity and ophthalmopathy, is consistent with Graves' disease being a "collagen-like disorder". The reason why inflammation and resulting tissue damage is limited to the thyroid, connective tissue of the skin and orbit, skeletal muscle and, possibly, the lacrimal gland, is unclear. One possibility is cross reaction of ANA with tissue specific membrane proteins in these sites. The extent of immunologic abnormalities, and the resulting clinical features, in patients with Graves' disease may reflect the severity of a putative defect in immune regulation.

Native gel electrophoresis and isoelectric focusing of a 64-kilodalton eye muscle protein shows that it is an important target for serum autoantibodies in patients with thyroid-associated ophthalmopathy and not expressed in other skeletal muscle

Although sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting are widely used to detect serum antibodies in patients with autoimmune disorders, this procedure unfolds and denatures proteins and may alter antibody-binding sites. We have used a gentle protocol for the preparation and purification of a 64-kilodalton (kDa) eye muscle (EM) membrane antigen associated with thyroid-associated ophthalmopathy (TAO) for use as antigen in immunoblotting. Pig EM membrane proteins were prepared from crude homogenates by high speed centrifugation and solubilized by hand homogenization. These native membrane proteins (NMprot) were then electrophoresed on an 8.5% polyacrylamide gel in the absence of SDS, reducing agents, or urea, and proteins from individual bands were eluted, applied to standard SDS-PAGE, and immunoblotted with selected TAO patient sera. A prominent 64-kDa protein, present in most of the bands, was recognized by autoantibodies in sera from 35% of the patients with TAO and 47% of those with Graves' hyperthyroidism without evident ophthalmopathy, but in only 4% of normal subjects. To further purify the 64-kDa protein and increase the sensitivity of immunoblotting, NMprot were separated by isoelectric focusing (IEF) in the absence of SDS, reducing agent, and urea. The 64-kDa protein appeared mainly in IEF fraction 7 and had an isoelectric point of 6.1-6.2. Similar results were found for a human EM protein of 64 kDa. Sera from groups of patients and normal subjects were tested in immunoblotting against a pig EM 64-kDa protein prepared from NMprot and purified in IEF. Tests were positive in 67% of patients with TAO, in 37.5% of those with Graves' hyperthyroidism without eye disease, in 11% of patients with Hashimoto's thyroiditis without eye disease, and in 9% of normal subjects. The 64-kDa protein was not found in other skeletal muscle. The demonstration that a native 64-kDa protein that is specifically targeted by autoantibodies in the serum of patients with TAO is expressed in EM, but not other skeletal muscle, greatly enhances its possible significance in the pathogenesis of this eye disorder.