R. D. G. Leslie

Elevated serum levels of macrophage-derived cytokines precede and accompany the onset of IDDM

SummaryTo determine whether cytokines could have a role in the development of insulin-dependent diabetes mellitus (IDDM), we measured serum levels of cytokines derived from T helper 1 (interleukin-2 and interferon-γ), T helper 2 (interleukin-4 and inter-leukin-10) lymphocytes and macrophages (tumour necrosis factor-α, interleukin-1 α and interleukin-1 Β) in patients before and after the onset of IDDM. Recently diagnosed IDDM patients had significantly higher levels of interleukin-2, interferon-γ, tumour necrosis factor-α and interleukin-1 α than patients with either long-standing IDDM, non-insulin-dependent diabetes (NIDDM), Graves disease, or control subjects (p<0.05 for all). Compared with control subjects, patients with long-standing IDDM and those with NIDDM had higher interleukin-2 and tumour necrosis factor-α levels (p<0.01 for all). Interleukin-4 and interleukin-10 were detectable in sera of patients with Graves disease only, while interleukin-1 Β was not detectable in the serum of any control or test subject. To investigate whether high cytokine levels precede the onset of IDDM, we studied 28 non-diabetic identical co-twins of patients with IDDM, followed-up prospectively for up to 6 years after the diagnosis of the index. Levels of tumour necrosis factor-α and interleukin-1 α were elevated above the normal range more frequently in the eight twins who developed diabetes than in those 20 who did not (p<0.005). Analysis of T helper 1 and T helper 2 profiles of the twin groups did not reveal a clear difference between prediabetic twins and twins remaining non-diabetic. These results support the notion that T helper 1 lymphocytes may play a role in the development of IDDM. This is associated with release of macrophage-derived cytokines, which is also a feature of the prediabetic period. The lack of evidence of a dominant T helper 1 profile of cytokine release before diabetes onset suggests that additional events, activating this arm of the cellular immune response, are required in the immediate prediabetic period.

Concordance rate for type II diabetes mellitus in monozygotic twins: Actuarial analysis

Summary To determine the concordance rate for Type II (non-insulin-dependent) diabetes mellitus in monozygotic twin pairs, initially ascertained discordant for diabetes, we carried out a prospective study on 44 non-diabetic subjects, each of whom had a sibling twin with diabetes (21 men, 23 women, median age 55 years, interquartile range 47–65). The subjects were referred as discordant for Type II diabetes. The twin pairs were part of the British Diabetic Twin Study and ascertained between May 1968 and January 1998. These subjects underwent an OGTT at time of referral and periodically thereafter. The mean follow-up was 8 years (range 0–18 years) and data were collected until January 1996. The percentage of twins who developed Type II diabetes was assessed by standard actuarial life-table methods and the pairwise concordance rate, that is the proportion of concordant pairs over the sum of concordant and discordant pairs, was calculated. The observed rates of concordance for Type II diabetes at 1, 5, 10, and 15 years follow-up were 17, 33, 57, and 76 %, respectively. The concordance rate for any abnormality of glucose metabolism (either Type II diabetes or impaired glucose tolerance) at 15 years follow-up was 96 %. The concordance rate for Type II diabetes in monozygotic twins is very high even in twins initially ascertained discordant for diabetes. [Diabetologia (1999) 42: 146–150]

Value of Antibodies to Islet Protein Tyrosine Phosphatase–Like Molecule in Predicting Type 1 Diabetes

Islet antigens associated with type 1 diabetes include a recently identified protein tyrosine phosphatase–like molecule IA-2, which contains the intracellular fragment IA-2ic. To determine whether combinations of antibodies including those to IA-2 characterize and predict type 1 diabetes, we studied antibodies to IA-2, IA-2ic, glutamic acid decarboxylase (GAD65), and islet cell antibodies (ICAs) in 1) 60 newly diagnosed type 1 diabetic patients followed for 1 year, 2) 31 monozygotic twin pairs discordant for type 1 diabetes followed up to 12 years (11 twins developed diabetes), 3) 18 dizygotic twin pairs discordant for type 1 diabetes, and 4) normal healthy control subjects. Newly diagnosed type 1 diabetic patients frequently had antibodies to IA-2 (62%), IA-2ic (67%), GAD65 (77%), and ICAs (85%). The intracellular fragment of IA-2 probably contains the immunodominant epitope as 137 of 143 samples with IA-2 antibodies from type 1 diabetic patients also had IA-2ic antibodies. Monozygotic twins were usually discordant for antibody specificities. Concordance was higher in monozygotic than matched dizygotic twins for both antibody combinations (33 vs. 6%, P < 0.05) and the development of diabetes (33 vs. 0%, P < 0.01). In monozygotic twins, all the antibodies were highly predictive of type 1 diabetes (positive predictive values all >87%), although antibodies were also detected in twins at low risk of disease. In summary, IA-2 emerges as a major antigen associated with type 1 diabetes and distinct from GAD65. Type 1 diabetes–associated autoimmunity, which is probably induced by environmental factors, does not necessarily herald progression to the disease. However, genetic factors may influence the development of combinations of disease-associated antibodies and the progression to type 1 diabetes.

Risk Factors for Cardiovascular Disease in IDDM: A Study of Identical Twins

Patients with insulin-dependent diabetes mellitus (IDDM) have an excess mortality, predominantly attributable to cardiovascular disease. To determine the effect of IDDM on potential risk factors for cardiovascular mortality, we studied subjects from the British Diabetic Twin Study Group. Forty-five identical twin pairs discordant for IDDM were recruited in addition to 45 matched nondiabetic singleton control subjects. All were selected to be normotensive and to have normal albumin excretion rates. Four variables differed significantly between the diabetic twins and their nondiabetic identical co-twins: diabetic twins had higher systolic blood pressure (sBP) ([mean ± SD] 127 ± 17 vs. 123 ± 18 mmHg, P < 0.05), high-density lipoprotein (HDL) cholesterol (1.36 ± 0.31 vs. 1.25 ± 0.29 mM, P < 0.05) and fibrinogen (3.23 ± 0.81 vs. 2.98 ± 0.71 mg/ml, P < 0.05) but lower factor VII (114 ± 34 vs. 122 ± 31%, P < 0.05). All four of these risk factors were significantly correlated (P < 0.001) within the identical twin pairs, as were the other risk factors. These significant correlations within twins for the risk factors studied reflects the impact of shared genetic and environmental influences. IDDM affects sBP, HDL cholesterol, fibrinogen, and factor VII, but only sBP and fibrinogen are affected adversely.

A role for innate immunity in type 1 diabetes

Two arms of the immune system, innate and adaptive immunity, differ in their mode of immune recognition. The innate immune system recognizes a few highly conserved structures on a broad range of microorganisms. On the other hand, recognition of self or autoreactivity is generally confined to the adaptive immune response. Whilst autoimmune features are relatively common, they should be distinguished from autoimmune disease that is infrequent. Type 1 diabetes is an immune‐mediated disease due to the destruction of insulin secreting cells mediated by aggressive immune responses, including activation of the adaptive immune system following genetic and environmental interaction. Hypotheses for the cause of the immune dysfunction leading to type 1 diabetes include self‐reactive T‐cell clones that (1) escape deletion in the thymus, (2) escape from peripheral tolerance or (3) escape from homeostatic control with an alteration in the immune balance leading to autoimmunity. Evidence, outlined in this review, raises the possibility that changes in the innate immune system could lead to autoimmunity, by either priming or promoting aggressive adaptive immune responses. Hostile microorganisms are identified by genetically determined surface receptors on innate effector cells, thereby promoting clearance of these invaders. These innate effectors include a few relatively inflexible cell populations such as monocytes/macrophages, dendritic cells (DC), natural killer (NK) cells, natural killer T (NKT) cells and γδ T cells. Recent studies have identified abnormalities in some of these cells both in patients with type 1 diabetes and in those at risk of the disease. However, it remains unclear whether these abnormalities in innate effector cells predispose to autoimmune disease. If they were to do so, then modulation of the innate immune system could be of therapeutic value in preventing immune‐mediated diseases such as type 1 diabetes. Copyright

Cytokine secretion patterns in twins discordant for Type I diabetes

Aims/hypothesis. The search for T-cell reactions that are associated with disease in Type I (insulin-dependent) diabetes mellitus is severely hampered because control groups cannot be matched for relevant immune response genes. We therefore compared T-cell responses between identical twins discordant for Type I diabetes. Methods. Pairs of monozygotic twins (n = 17) discordant for Type I diabetes were studied. Cultures were set up from whole blood immediately after sampling and cells were challenged with human recombinant hsp60, with the mitogen phytohaemagglutinin or with the staphylococcal superantigen. Supernatants were removed after 48 or 96 h and analysed for T-helper1 type cytokines interferon-γ, TNFα and T-helper2 type cytokines IL-4, IL-10 by sandwich-ELISA. Results. The height of the T-helper1 type cytokine response to hsp60, phytohaemagglutinin or staphylococcal enterotoxin B did not show disease association, i. e. it was similar between discordant twins. In contrast, the production of T-helper2 type cytokines differed between discordant twins. The IL-10 response to hsp60 was higher in twins at low disease risk (islet cell antibody-negative) than in their diabetic cotwins (p < 0.01), as was the IL-4 response to phytohaemagglutinin (p < 0.05). No difference was seen in the cytokine response between islet cell antibody-positive twins and their diabetic cotwins. Conclusions/interpretation. The data indicate an association between T-helper2 type cytokine secretion patterns and disease or disease risk. [Diabetologia (1999) 42: 1080–1085]

Personalized medicine: risk prediction, targeted therapies and mobile health technology

Personalized medicine is increasingly being employed across many areas of clinical practice, as genes associated with specific diseases are discovered and targeted therapies are developed. Mobile apps are also beginning to be used in medicine with the aim of providing a personalized approach to disease management. In some areas of medicine, patient-tailored risk prediction and treatment are applied routinely in the clinic, whereas in other fields, more work is required to translate scientific advances into individualized treatment. In this forum article, we asked specialists in oncology, neurology, endocrinology and mobile health technology to discuss where we are in terms of personalized medicine, and address their visions for the future and the challenges that remain in their respective fields.

Decreased Growth Velocity Before IDDM Onset

Diabetes can retard growth. Growth was studied prospectively in 12 nondiabetic identical twins aged <14 yr and in their co-twins with insulin-dependent diabetes mellitus (IDDM) to determine whether changes in growth occur before the onset of IDDM. Seven of the 12 nondiabetic twins subsequently developed IDDM; the remainder are now unlikely to become diabetic. A significantly reduced growth velocity was observed more frequently in the nondiabetic twins (7 of 12) than in their diabetic co-twins (1 of 12; P = 0.03). Of the 7 nondiabetic twins who were prediabetic, 6 had a reduction in growth velocity to below the 3rd percentile before the onset of diabetes compared with 1 of their diabetic co-twins (P = 0.03). However, only 1 of the 5 nondiabetic twins who did not develop diabetes showed a reduction in growth velocity. The nadir of growth in the twins who developed diabetes occurred a mean of 1.2 yr before diagnosis (range 0.3–2.3 yr). All 7 of the prediabetic twins had islet cell antibodies when first seen, and 3 had them before they showed either decreased growth velocity or impaired glucose tolerance. In 4 prediabetic twins, the decreased growth preceded impaired glucose tolerance. The prediabetic twins tested had lower testosterone or estradiol levels at the time they showed decreased growth than their diabetic twins. We conclude that decreased growth velocity is an early sensitive marker of IDDM.

Principles of Autoantibodies as Disease-specific Markers

The immune system is designed by nature to protect us from our environment. But activation of the immune response not only protects us from disease, as in infectious diseases, it can cause disease, as in autoimmunity. Indeed, about 20% of North American and European populations suffer from autoimmune or inflammatory diseases mediated by this immune response. The normal immune response involves activation of both innate and adaptive immune systems. Adaptive immunity is associated with activation of both T and B cells, the latter producing antibodies. Autoantibodies can be detected in the sera and, in recent years, have been valuable in both the diagnosis and the prediction of disease. It is our opinion that the practical value of autoantibodies has not been fully realised in the majority of diseases in which they can be detected. Realising the clinical potential of autoantibodies could be extremely valuable, and in this article we set out the principles for measuring autoantibodies both as diagnostic markers of disease activity and disease classification or as predictive markers of progression to clinical disease. Observations supporting this position are presented and whilst they are broadly based on the study of autoimmune diseases, it remains possible that the general principles they encompass can be applied to other disease processes, including cancer. Studies using autoantibodies in autoimmune diseases suggest several principles. First, autoantibodies can reflect the disease process and, when detected during a prolonged disease prodrome, autoantibodies can predict clinical disease. Second, when there is aetiological heterogeneity in clinical disease, autoantibodies can help classify the disease process. Both these points are particularly relevant when autoantibodies themselves have the capacity to damage tissue. Third, a number of distinct autoantibodies are associated with any one disease, and some are more predictive of progression to clinical symptoms than others. Fourth, the risk of progression to disease, the rate of progression, and the severity of the clinical disease can be predicted to a degree by the number of autoantibodies, the type of autoantibody and the titer of the autoantibody. – 8] In addition, associated features including genetic risk and evidence of target organ failure can enhance the predictive value of autoantibodies. These points will now be set out in more detail.

Alterations in T-Lymphocyte Subpopulations in Type I Diabetes: Exploration of Genetic Influence in Identical Twins

To evaluate factors influencing the alteration in subsets of T-lymphocytes, we studied 24 pairs of identical twins discordant for insulin-dependent (type I) diabetes mellitus. Subsets were assessed by monoclonal antibodies and a pure preparation of peripheral blood mononuclear cells obtained by centrifugation of heparinized whole blood with a Ficoll/Triosil gradient. In 12 pairs studied within 5 yr of diagnosis, we observed a reduction in the percentage of cells reacting with OKT8 (recognizing the CD8 antigen present on the suppressor/cytotoxic subset) (P < .05), but a similar level was detected in their nondiabetic cotwins. In 12 pairs studied >5 yr after the diagnosis and in whom the nondiabetic twin is less likely to develop diabetes, the percentage of cells reacting with OKT8 was reduced in both the diabetic (P < .05) and the nondiabetic (P < .01) twins. Reductions were also seen with OKT3 (recognizing the CD3 antigen present on the total T-lymphocyte population) and OKT4 (recognizing the CD4 antigen present on the helper/inducer subset), but only in the diabetic twins from the group with longer discordance. We conclude that a reduced percentage of suppressor/cytotoxic cells is associated with type I diabetes, but the reduction appears to be genetically determined. Total T-lymphocytes are also reduced but mainly in the helper/inducer subset and only in diabetic patients of long duration. Such a reduction cannot therefore be primarily genetically determined.