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Definition, Diagnosis and Classification of Diabetes in Youth
Abstract
Early Descriptions of Diabetes Ancient records up to 3000 years old describe a disease in youth that was sudden in onset, resulted in acute metabolic decompensation, and culminated in death. Although this clinical picture described millennia ago was likely that of diabetes, the first accepted description of diabetes as a disorder associated with increased urine output came from ancient Egypt (the Ebers papyrus) around 1550 B.C. It was not until the second century B.C. that the term “diabetes” was used. Credit for coining “diabetes” is given to Demetrios of Apamaia who derived the term from the Greek word diabeinein, meaning “siphon” or “pass through.”
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To test the hypothesis that interaction between genetic, immunological, clinical and metabolic risk factors influences the outcome of Type II (non-insulin-dependent) diabetes mellitus, we examined which of the above factors present at baseline were associated with mortality in 134 Type II diabetic patients followed for 9 years. Thirty-eight patients (29%) died during the follow-up period; the majority of whom (68%) died from cardiovascular disease. At baseline, the deceased patients had higher HbA1c values (p = 0.002), higher LDL-triglycerides (p = 0.007), lower HDL-cholesterol (p = 0.007), higher non-esterified fatty acid (NEFA) concentrations (p = 0.014), and higher albumin excretion rate (p < 0.0001) than the patients who survived. In addition, the frequency of HLA-DR4 (21 vs 39%, p = 0.048) and of parietal cell antibodies (5 vs 14%, p = 0.016) were decreased in the deceased as compared to the living patients. Patients who died during follow-up also had more retinopathy (42 vs 16%, p = 0.002), neuropathy (57 vs 23%, p < 0.001), microalbuminuria (45 vs 6%, p < 0.0001), coronary heart disease (50 vs 13%, p < 0.0001), and peripheral vascular disease (27 vs 9%, p = 0.005) at baseline than patients who survived. In a multiple logistic regression analysis macroangiopathy (p = 0.004), neuropathy (p = 0.007), HbA1c (p = 0.018) and albumin excretion rate (p = 0.016) were independent risk factors for death. In patients free of cardiovascular disease at baseline, conventional risk factors such as LDL-cholesterol (p = 0.005) and age (p = 0.003) were associated with subsequent development of cardiovascular disease. In conclusion, in addition to coexisting macroangiopathy, increased albumin excretion rate, poor glycaemic control and neuropathy are risk factors for cardiovascular mortality in patients with Type II diabetes. The presence of HLA-DR4 and signs of autoimmunity may be associated with decreased risk of cardiovascular disease.
There is substantial evidence for a role of genetic factors in the development of diabetic nephropathy. In Pima Indians, a link between susceptibility to diabetic nephropathy and Type II (non-insulin-dependent) diabetes mellitus has been proposed. In this study, our aim was to examine the association between a family history of Type II diabetes and diabetic nephropathy in patients with Type I (insulin-dependent) diabetes mellitus.
In a cross-sectional case-control study, we assessed the prevalence of Type II diabetes in the parents of 137 Type I diabetic patients with diabetic nephropathy (albuminuria > 300 microg/min in two of three overnight urine collections) compared with the parents of 54 Type I diabetic patients without nephropathy (albuminuria < 20 microg/min).
Thirty-four (25 %) of the patients with nephropathy compared with five (9 %) of the patients without nephropathy had a parental history of Type II diabetes (p = 0.019). A parental history of Type II diabetes was associated with a three-fold risk [odds ratio 2.95 (95% confidence interval: 1.03 to 8.40), p = 0.043] of diabetic nephropathy after adjustment for sex, glycaemic control and family history of hypertension. Furthermore, there was an excess of risk factors for development of Type II diabetes (higher fasting plasma glucose concentrations, higher prevalence of hypertension, higher waist-hip ratio and a tendency towards more glucose intolerance) among previously non-diabetic parents of patients with nephropathy.
Genetic or environmental factors or both related to familial Type II diabetes increase susceptibility to diabetic nephropathy in patients with Type I diabetes.
Hyperglycaemia predicts microvascular complications but data on macrovascular disease are limited. We searched for predictors of carotid artery intima-media thickness in young adults with Type I (insulin-dependent) diabetes mellitus.
A total of 71 children (F/M = 34/37) were followed after their diagnosis until they reached 32 +/- 1 years of age, when duration of diabetes averaged 22 +/- 1 years. Cardiovascular risk markers [lipids, blood pressure, smoking, urinary albumin excretion rate, lifetime glycaemic exposure (A(1c) months), exercise habits, alcohol consumption, family history] were evaluated at age 21 +/- 1 for the baseline examination and at age 32 +/- 1 years for the follow-up examination years. During follow-up, intima-media thickness of common and internal carotid arteries and the carotid bulb were quantitated using a high-resolution B-mode ultrasound.
In univariate analysis, age, BMI, blood pressure, lifetime glycaemic exposure, a positive family history of Type II (non-insulin-dependent) diabetes mellitus, hypertension and cardiovascular disease were predictors of carotid intima-media thickness. In multivariate analysis, a positive family history of Type II diabetes predicted maximal ( p< 0.05) and common ( p< 0.005) carotid artery intima-media thickness, family history of hypertension predicted increases in maximal ( p< 0.04), and far wall ( p< 0.006) carotid artery intima-media thickness, and lifetime glycaemic exposure was an independent predictor of increased carotid bulb thickness ( p< 0.03).
Positive family histories of Type II diabetes and hypertension are independent predictors of carotid intima-media thickness in patients with Type I diabetes, and could therefore predispose these patients to atherosclerosis
Glucose homeostasis is determined by an interplay between insulin secretion and insulin action. In type 1 diabetes, autoimmune destruction of pancreatic beta cells leads to impaired insulin secretion. However, the contribution of impaired insulin action (insulin resistance) to the development of type 1 diabetes has received little attention. We investigated whether insulin resistance was a risk factor for progression to type 1 diabetes.
Islet-antibody-positive first-degree relatives of type 1 diabetes probands were followed for 4.0 years (median). Insulin secretion was measured as first-phase insulin response (FPIR) to intravenous glucose. Insulin resistance was estimated by homeostasis model assessment of insulin resistance (HOMA-R). We compared subjects who progressed (n=43) and subjects who did not progress (n=61) to diabetes, including 21 pairs matched for age, sex, islet antibodies and FPIR.
Progressors had higher insulin resistance relative to insulin secretion at baseline (median HOMA-R : FPIR 0.033 vs 0.013, p<0.0001). According to Cox proportional hazards analysis, islet antibody number, FPIR, fasting plasma glucose, fasting serum insulin, HOMA-R and log(HOMA-R : FPIR) were each predictive of progression to diabetes. However, log(HOMA-R : FPIR) (hazard ratio 2.57 per doubling, p<0.001) was the only metabolic variable independently associated with progression. In the matched comparison, progressors had higher fasting glucose, fasting insulin, HOMA-R and HOMA-R : FPIR, both at baseline and during the follow-up pre-clinical phase.
Relatives positive for islet antibodies who progress most rapidly to diabetes have a subtle disturbance of insulin-glucose homeostasis years before the onset of symptoms, distinguished by greater insulin resistance for their level of insulin secretion. Taking steps to reduce this insulin resistance could therefore delay the development of type 1 diabetes.
'Latent autoimmune diabetes in adults' (LADA) is the term coined to describe adults who have a slowly progressive form of autoimmune or type 1 diabetes that can be treated initially without insulin injections. The diagnosis of LADA is currently based on three clinical criteria: (1) adult age at onset of diabetes; (2) the presence of circulating islet autoantibodies, which distinguishes LADA from type 2 diabetes; and (3) insulin independence at diagnosis, which distinguishes LADA from classic type 1 diabetes. The prevalence of LADA in adults presenting with non-insulin-requiring diabetes is approximately 10%. Recognition of LADA expands the concept and prevalence of autoimmune diabetes, but LADA remains poorly understood at both a clinical and research level. In this perspective, we review the nomenclature, diagnostic criteria, genetics, pathology and therapy of LADA, to arrive at recommendations that might advance knowledge and management of this form of diabetes.
Heterozygous activating mutations in KCNJ11, encoding the Kir6.2 subunit of the ATP-sensitive potassium (K(ATP)) channel, cause 30 to 58 percent of cases of diabetes diagnosed in patients under six months of age. Patients present with ketoacidosis or severe hyperglycemia and are treated with insulin. Diabetes results from impaired insulin secretion caused by a failure of the beta-cell K(ATP) channel to close in response to increased intracellular ATP. Sulfonylureas close the K(ATP) channel by an ATP-independent route.
We assessed glycemic control in 49 consecutive patients with Kir6.2 mutations who received appropriate doses of sulfonylureas and, in smaller subgroups, investigated the insulin secretory responses to intravenous and oral glucose, a mixed meal, and glucagon. The response of mutant K(ATP) channels to the sulfonylurea tolbutamide was assayed in xenopus oocytes.
A total of 44 patients (90 percent) successfully discontinued insulin after receiving sulfonylureas. The extent of the tolbutamide blockade of K(ATP) channels in vitro reflected the response seen in patients. Glycated hemoglobin levels improved in all patients who switched to sulfonylurea therapy (from 8.1 percent before treatment to 6.4 percent after 12 weeks of treatment, P<0.001). Improved glycemic control was sustained at one year. Sulfonylurea treatment increased insulin secretion, which was more highly stimulated by oral glucose or a mixed meal than by intravenous glucose. Exogenous glucagon increased insulin secretion only in the presence of sulfonylureas.
Sulfonylurea therapy is safe in the short term for patients with diabetes caused by KCNJ11 mutations and is probably more effective than insulin therapy. This pharmacogenetic response to sulfonylureas may result from the closing of mutant K(ATP) channels, thereby increasing insulin secretion in response to incretins and glucose metabolism. (ClinicalTrials.gov number, NCT00334711 [ClinicalTrials.gov].).
The ATP-sensitive potassium (K(ATP)) channel, composed of the beta-cell proteins sulfonylurea receptor (SUR1) and inward-rectifying potassium channel subunit Kir6.2, is a key regulator of insulin release. It is inhibited by the binding of adenine nucleotides to subunit Kir6.2, which closes the channel, and activated by nucleotide binding or hydrolysis on SUR1, which opens the channel. The balance of these opposing actions determines the low open-channel probability, P(O), which controls the excitability of pancreatic beta cells. We hypothesized that activating mutations in ABCC8, which encodes SUR1, cause neonatal diabetes.
We screened the 39 exons of ABCC8 in 34 patients with permanent or transient neonatal diabetes of unknown origin. We assayed the electrophysiologic activity of mutant and wild-type K(ATP) channels.
We identified seven missense mutations in nine patients. Four mutations were familial and showed vertical transmission with neonatal and adult-onset diabetes; the remaining mutations were not transmitted and not found in more than 300 patients without diabetes or with early-onset diabetes of similar genetic background. Mutant channels in intact cells and in physiologic concentrations of magnesium ATP had a markedly higher P(O) than did wild-type channels. These overactive channels remained sensitive to sulfonylurea, and treatment with sulfonylureas resulted in euglycemia.
Dominant mutations in ABCC8 accounted for 12 percent of cases of neonatal diabetes in the study group. Diabetes results from a newly discovered mechanism whereby the basal magnesium-nucleotide-dependent stimulatory action of SUR1 on the Kir pore is elevated and blockade by sulfonylureas is preserved.
Transient (TNDM) and Permanent (PNDM) Neonatal Diabetes Mellitus are rare conditions occurring in 1:300,000-400,000 live births. TNDM infants develop diabetes in the first few weeks of life but go into remission in a few months, with possible relapse to a permanent diabetes state usually around adolescence or as adults. The pancreatic dysfunction in this condition may be maintained throughout life, with relapse initiated at times of metabolic stress such as puberty or pregnancy. In PNDM, insulin secretory failure occurs in the late fetal or early post-natal period and does not go into remission. Patients with TNDM are more likely to have intrauterine growth retardation and less likely to develop ketoacidosis than patients with PNDM. In TNDM, patients are younger at the diagnosis of diabetes and have lower initial insulin requirements. Considerable overlap occurs between the two groups, so that TNDM cannot be distinguished from PNDM based on clinical features. Very early onset diabetes mellitus seems to be unrelated to autoimmunity in most instances. A number of conditions are associated with PNDM, some of which have been elucidated at the molecular level. Among these, the very recently elucidated mutations in the KCNJ11 and ABCC8 genes, encoding the Kir6.2 and SUR1 subunit of the pancreatic KATP channel involved in regulation of insulin secretion, account for one third to half of the PNDM cases. Molecular analysis of chromosome 6 anomalies (found in more than 60% in TNDM), and the KCNJ11 and ABCC8 genes encoding Kir6.2 and SUR1, provides a tool to identify TNDM from PNDM in the neonatal period. This analysis also has potentially important therapeutic consequences leading to transfer some patients, those with mutations in KCNJ11 and ABCC8 genes, from insulin therapy to sulfonylureas. Recurrent diabetes is common in patients with "transient" neonatal diabetes mellitus and, consequently, prolonged follow-up is imperative. Realizing how difficult it is to take care of a child of this age with diabetes mellitus should prompt clinicians to transfer these children to specialized centers. Insulin therapy and high caloric intake are the basis of the treatment. Insulin pump may offer an interesting therapeutic tool in this age group in experienced hands.
The presence of cytoplasmic islet-cell autoantibodies has been recognized as a risk factor for the development of diabetes mellitus in relatives of patients with insulin-dependent diabetes mellitus (IDDM), but the magnitude of the risk is unknown, as is the influence of other factors, such as age, sex, and race.
From 1979 through 1989, we studied 4015 initially nondiabetic relatives of 1590 probands with IDDM to determine the risk of IDDM according to the presence and titer of autoantibodies, as well as other factors.
Of the 4015 nondiabetic relatives, 125 (3.1 percent) had islet-cell antibodies in their initial serum samples, and 40 contracted IDDM. Islet-cell antibodies were most frequent (4.3 percent) in relatives who were under 20 years of age (P = 0.001) and in those (4.8 percent) from families with more than one affected member (a multiplex pedigree) (P = 0.003). Independent risk factors for the development of diabetes in the relatives included age of less than 10 years at the time of the initial study (P = 0.001), membership in a multiplex pedigree (P = 0.02), and a positive test for islet-cell antibodies in the initial serum sample (P = 0.0001). Twenty-seven of the relatives in whom diabetes developed (67.5 percent) had positive tests for islet-cell antibodies before the diagnosis of IDDM, giving a relative risk of IDDM of 68 (95 percent confidence interval, 34 to 134) for antibody-positive relatives. Islet-cell-antibody titers of 20 Juvenile Diabetes Foundation units or higher were associated with an increasing risk of diabetes.
Nondiabetic relatives of probands with IDDM who are in the first two decades of life, are members of multiplex pedigrees, and have increased titers of islet-cell antibodies are the most likely to contract IDDM themselves.
Blood glucose concentrations are controlled by a loop incorporating two components, the beta cells which secrete insulin and the insulin-sensitive tissues (liver, muscle, adipose) which respond to it. Loss of blood glucose control might result from failure of the beta cells to secrete insulin, resistance of the tissues to its action, or a combination of both. The distinctions between Type I (insulin-dependent) and Type II (non-insulin-dependent) diabetes mellitus are becoming increasingly blurred both clinically and aetiologically, where beta-cell insufficiency is the shared characteristic. The 'Accelerator Hypothesis' identifies three processes which variably accelerate the loss of beta cells through apoptosis: constitution, insulin resistance and autoimmunity. None of the accelerators leads to diabetes without excess weight gain, a trend which the 'Accelerator Hypothesis' deems central to the rising incidence of both types of diabetes in the industrially developed world. Weight gain causes an increase in insulin resistance, which results in the weakening of glucose control. The rising blood glucose (glucotoxicity) accelerates beta-cell apoptosis directly in all and, by inducing beta-cell immunogens, further accelerates it in a subset genetically predisposed to autoimmunity. Rather than overlap between two types of diabetes, the 'Accelerator Hypothesis' envisages overlay. Body mass is central to the development and rising incidence of all diabetes. Only tempo distinguishes the 'types'. The control of weight gain, and with it insulin resistance, could be the means of minimising both.
Libman IM, Becker DJ. Coexistence of type 1 and type 2 diabetes mellitus: double diabetes?
Wolfram syndrome is caused by mutations in WFS1 encoding wolframin, a polytopic membrane protein of the endoplasmic reticulum. Here, we investigated the molecular pathomechanisms of four missense and two truncating mutations in WFS1. Expression in COS-7 cells as well as direct analysis of patient cells revealed that WFS1 mutations lead to drastically reduced steady-state levels of wolframin. All mutations resulted in highly unstable proteins which were delivered to proteasomal degradation. No wolframin aggregates were found in patient cells suggesting that Wolfram syndrome is not a disease of protein aggregation. Rather, WFS1 mutations cause loss-of-function by cellular depletion of wolframin.
