出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2013/03/08 15:21:14」(JST)
Diabetes type 1 | |
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Classification and external resources | |
A blue circle symbol for diabetes.[1] |
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ICD-10 | E10 |
ICD-9 | 250.01 |
OMIM | 222100 |
DiseasesDB | 3649 |
MedlinePlus | 000305 |
eMedicine | med/546 |
MeSH | D003922 |
Diabetes mellitus type 1 (type 1 diabetes, T1DM, formerly insulin dependent or juvenile diabetes) is a form of diabetes mellitus that results from autoimmune destruction of insulin-producing beta cells of the pancreas.[2] The subsequent lack of insulin leads to increased blood and urine glucose. The classical symptoms are polyuria (frequent urination), polydipsia (increased thirst), polyphagia (increased hunger), and weight loss.[3]
Incidence varies from 8 to 17 per 100,000 in Northern Europe and the U.S. with a high of about 35 per 100,000 in Scandinavia to a low of 1 per 100,000 in Japan and China.[4]
Eventually, type 1 diabetes is fatal unless treated with insulin. Injection is the most common method of administering insulin although other methods are insulin pumps and inhaled insulin. Other alternatives are Pancreatic transplants that have been used and also pancreatic islet cell transplantation. Transplantation is experimental yet growing.[5]
Most people who develop type 1 are otherwise healthy.[6] Although the cause of type 1 diabetes is still not fully understood, it is believed to be of immunological origin.
Type 1 can be distinguished from type 2 diabetes via a C-peptide assay, which measures endogenous insulin production.
Type 1 treatment must be continued indefinitely in all cases. Treatment should not significantly impair normal activities but can be done adequately if sufficient patient training, awareness, appropriate care, discipline in testing and dosing of insulin is taken. However, treatment remains quite burdensome for many people. Complications may be associated with both low blood sugar and high blood sugar, both largely due to the nonphysiological manner in which insulin is replaced. Low blood sugar may lead to seizures or episodes of unconsciousness, and requires emergency treatment. High blood sugar may lead to increased fatigue and can also result in long-term damage to organs.
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The classical symptoms of type 1 diabetes include: polyuria (frequent urination), polydipsia (increased thirst), Xerostomia (dry mouth), polyphagia (increased hunger), fatigue, and weight loss.[3] Before a person knows they have diabetes, blood sugar levels can be in a very high range for long periods of time which could cause diabetic ketoacidosis. These symptoms could be xeroderma (dry skin), rapid, deep breathing, drowsiness, abdominal pain, and vomiting.[7]
Diabetes type 1 is induced by one or more of the following: genetic susceptibility, a diabetogenic trigger and/or exposure to a driving antigen.[8]
Type 1 diabetes is a polygenic disease, meaning many different genes contribute to its onset. Depending on locus or combination of loci, it can be dominant, recessive, or somewhere in between. The strongest gene, IDDM1, is located in the MHC Class II region on chromosome 6, at staining region 6p21. Certain variants of this gene increase the risk for decreased histocompatibility characteristic of type 1. Such variants include DRB1 0401, DRB1 0402, DRB1 0405, DQA 0301, DQB1 0302 and DQB1 0201, which are common in North Americans of European ancestry and in Europeans.[9] Some variants also appear to be protective.[9]
The risk of a child developing type 1 diabetes is about 10% if the father has it, about 10% if a sibling has it, about 4% if the mother has type 1 diabetes and was aged 25 or younger when the child was born, and about 1% if the mother was over 25 years old when the child was born.[10]
Environmental factors can influence expression of type 1. For identical twins, when one twin had type 1 diabetes, the other twin only had it 30%–50% of the time. Despite having exactly the same genome, one twin had the disease, where the other did not; this suggests environmental factors, in addition to genetic factors, can influence disease prevalence.[11] Other indications of environmental influence include the presence of a 10-fold difference in occurrence among Caucasians living in different areas of Europe, and a tendency to acquire the incidence of the disease of the destination country for people who migrate.[8]
One theory, discussed by DeLisa Fairweather and Noel R. Rose, among others,[12] proposes that type 1 diabetes is a virus-triggered autoimmune response in which the immune system attacks virus-infected cells along with the beta cells in the pancreas. The Coxsackie virus family or rubella is implicated, although the evidence is inconclusive. In type 1, pancreatic beta cells in the islets of Langerhans are destroyed, decreasing endogenous insulin production. This distinguishes type 1's origin from type 2. The type of diabetes a patient has is determined only by the cause—fundamentally by whether the patient is insulin resistant (type 2) or insulin deficient without insulin resistance (type 1).
This vulnerability is not shared by everyone, for not everyone infected by the suspected virus develops type 1 diabetes. This has suggested presence of a genetic vulnerability[13] and there is indeed an observed inherited tendency to develop type 1. It has been traced to particular HLA genotypes, though the connection between them and the triggering of an autoimmune reaction is still poorly understood.
Some researchers believe the autoimmune response is influenced by antibodies against cow's milk proteins.[14] No connection has been established between autoantibodies, antibodies to cow's milk proteins, and type 1 diabetes. A subtype of type 1 (identifiable by the presence of antibodies against beta cells) typically develops slowly, so is often confused with type 2. In addition, a small proportion of type 2 cases manifest a genetic form of the disease called maturity onset diabetes of the young.[citation needed]
Vitamin D in doses of 2000 IU per day given during the first year of a child's life has been connected in one study in northern Finland (where intrinsic production of Vitamin D is low due to low natural light levels) with an 80% reduction in the risk of getting type 1 diabetes later in life. The causal connection, if any, is obscure.
Short breastfeeding period and short attendance at day care is associated with the risk of type 1 diabetes in Czech children.[15]
Some chemicals and drugs preferentially destroy pancreatic cells. Pyrinuron (Vacor, N-3-pyridylmethyl-N'-p-nitrophenyl urea), a rodenticide introduced in the United States in 1976, selectively destroys pancreatic beta cells, resulting in type 1 diabetes after accidental or intentional ingestion. Vacor was withdrawn from the U.S. market in 1979, but is still used in some countries. Zanosar is the trade name for streptozotocin, an antibiotic and antineoplastic agent used in chemotherapy for pancreatic cancer; it also kills beta cells, resulting in loss of insulin production. Other pancreatic problems, including trauma, pancreatitis or tumors (either malignant or benign), can also lead to loss of insulin production.
The pathophysiology in diabetes type 1 is basically a destruction of beta cells in the pancreas, regardless of which risk factors or causative entities have been present.
Individual risk factors can have separate pathophysiological processes to, in turn, cause this beta cell destruction. Still, a process that appears to be common to most risk factors is an autoimmune response towards beta cells, involving an expansion of autoreactive CD4+ and CD8+ T helper cells, autoantibody-producing B cells and activation of the innate immune system.[9][16]
Condition | 2 hour glucose | Fasting glucose | HbA1c |
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mmol/l(mg/dl) | mmol/l(mg/dl) | % | |
Normal | <7.8 (<140) | <6.1 (<110) | <6.0 |
Impaired fasting glycaemia | <7.8 (<140) | ≥ 6.1(≥110) & <7.0(<126) | 6.0–6.4 |
Impaired glucose tolerance | ≥7.8 (≥140) | <7.0 (<126) | 6.0–6.4 |
Diabetes mellitus | ≥11.1 (≥200) | ≥7.0 (≥126) | ≥6.5 |
Diabetes mellitus is characterized by recurrent or persistent hyperglycemia, and is diagnosed by demonstrating any one of the following:[19]
About a quarter of people with new type 1 diabetes have developed some degree of diabetic ketoacidosis (a type of metabolic acidosis which is caused by high concentrations of ketone bodies, formed by the breakdown of fatty acids and the deamination of amino acids) by the time the diabetes is recognized. The diagnosis of other types of diabetes is usually made in other ways. These include ordinary health screening, detection of hyperglycemia during other medical investigations, and secondary symptoms such as vision changes or unexplainable fatigue. Diabetes is often detected when a person suffers a problem that may be caused by diabetes, such as a heart attack, stroke, neuropathy, poor wound healing or a foot ulcer, certain eye problems, certain fungal infections, or delivering a baby with macrosomia or hypoglycemia.
A positive result, in the absence of unequivocal hyperglycemia, should be confirmed by a repeat of any of the above-listed methods on a different day. Most physicians prefer to measure a fasting glucose level because of the ease of measurement and the considerable time commitment of formal glucose tolerance testing, which takes two hours to complete and offers no prognostic advantage over the fasting test.[21] According to the current definition, two fasting glucose measurements above 126 mg/dL (7.0 mmol/L) is considered diagnostic for diabetes mellitus.
Patients with fasting glucose levels from 100 to 125 mg/dL (5.6 to 6.9 mmol/L) are considered to have impaired fasting glucose. Patients with plasma glucose at or above 140 mg/dL (7.8 mmol/L), but not over 200 mg/dL (11.1 mmol/L), two hours after a 75 g oral glucose load are considered to have impaired glucose tolerance. Of these two pre-diabetic states, the latter in particular is a major risk factor for progression to full-blown diabetes mellitus and cardiovascular disease.[22]
The appearance of diabetes-related autoantibodies has been shown to be able to predict the appearance of diabetes type 1 before any hyperglycemia arises, the main ones being islet cell autoantibodies, insulin autoantibodies, autoantibodies targeting the 65-kDa isoform of glutamic acid decarboxylase (GAD) and autoantibodies targeting the phosphatase-related IA-2 molecule.[8] By definition, the diagnosis of diabetes type 1 can be made first at the appearance of clinical symptoms and/or signs, but the emergence of autoantibodies may itself be termed "latent autoimmune diabetes". Not everyone with autoantibodies progresses to diabetes type 1, but the risk increases with the number of antibody types, with three to four antibody types giving a risk of progressing to diabetes type 1 of 60%–100%.[8] The time interval from emergence of autoantibodies to frank diabetes type 1 can be a few months in infants and young children, but in some people it may take years – in some cases more than 10 years.[8] Islet cell autoantibodies are detected by conventional immunofluorescence, while the rest are measured with specific radiobinding assays.[8]
Type 1 diabetes is not currently preventable.[23] Some researchers believe it might be prevented at the latent autoimmune stage, before it starts destroying beta cells.[9]
Cyclosporine A, an immunosuppressive agent, has apparently halted destruction of beta cells (on the basis of reduced insulin usage), but its nephrotoxicity and other side effects make it highly inappropriate for long-term use.[9]
Anti-CD3 antibodies, including teplizumab and otelixizumab, had suggested evidence of preserving insulin production (as evidenced by sustained C-peptide production) in newly diagnosed type 1 diabetes patients.[9] A probable mechanism of this effect was believed to be preservation of regulatory T cells that suppress activation of the immune system and thereby maintain immune system homeostasis and tolerance to self-antigens.[9] The duration of the effect is still unknown, however.[9] In 2011, Phase III studies with otelixizumab and teplizumab both failed to show clinical efficacy, potentially due to an insufficient dosing schedule.[24][25]
An anti-CD20 antibody, rituximab, inhibits B cells and has been shown to provoke C-peptide responses three months after diagnosis of type 1 diabetes, but long-term effects of this have not been reported.[9]
Some research has suggested breastfeeding decreases the risk in later life;[26][27] various other nutritional risk factors are being studied, but no firm evidence has been found.[28] Giving children 2000 IU of Vitamin D during their first year of life is associated with reduced risk of type 1 diabetes, though the causal relationship is obscure.[29]
Children with antibodies to beta cell proteins (i.e. at early stages of an immune reaction to them) but no overt diabetes, and treated with vitamin B3 (niacin), had less than half the diabetes onset incidence in a seven-year time span than did the general population, and an even lower incidence relative to those with antibodies as above, but who received no vitamin B3.[30]
Type 1 is treated with insulin replacement therapy—either via subcutaneous injection or insulin pump, along with attention to dietary management, typically including carbohydrate tracking, and careful monitoring of blood glucose levels using glucose meters. Today, the most common insulins are biosynthetic products produced using genetic recombination techniques; formerly, cattle or pig insulins were used, and even sometimes insulin from fish.[31] Major global suppliers include Eli Lilly and Company, Novo Nordisk, and Sanofi-Aventis. A more recent trend, from several suppliers, is insulin analogs which are slightly modified insulins with different onset or duration of action times.
Untreated type 1 diabetes commonly leads to coma, often from diabetic ketoacidosis, which is fatal if untreated. Ketoacidosis causes cerebral edema (accumulation of liquid in the brain). This complication is very life-threatening; it makes ketoacidosis the most common cause of death in pediatric diabetes.[32]
Continuous glucose monitors have been developed and marketed which can alert patients to the presence of dangerously high or low blood sugar levels, but technical limitations have limited the impact these devices have had on clinical practice so far.
Treatment of diabetes focuses on lowering blood sugar or glucose (BG) to the near normal range, approximately 80–140 mg/dl (4.4–7.8 mmol/L).[33] The ultimate goal of normalizing BG is to avoid long-term complications that affect the nervous system (e.g. peripheral neuropathy leading to pain and/or loss of feeling in the extremities), and the cardiovascular system (e.g. heart attacks, vision loss). People with type 1 diabetes always need to use insulin, but treatment can lead to low BG (hypoglycemia), i.e. BG less than 70 mg/dl (3.9 mmol/l). Hypoglycemia is a very common occurrence in people with diabetes, usually the result of a mismatch in the balance among insulin, food and physical activity, although the nonphysiological method of delivery also plays a role.
Sulfonylureas: These drugs stimulate the pancreas to make more insulin. Biguanides: These agents decrease the amount of glucose produced by the liver. Alpha-glucosidase inhibitors: These agents slow absorption of the starches a person eats. This slows down glucose production. Thiazolidinediones: These agents increase sensitivity to insulin. Meglitinides: These agents stimulate the pancreas to make more insulin. D-phenylalanine derivatives: These agents stimulate the pancreas to produce more insulin more quickly. Amylin synthetic derivatives: Amylin is a naturally occurring hormone secreted by the pancreas along with insulin. An amylin derivative, such as pramlintide (Symlin), is indicated when blood sugar control is not achieved despite optimal insulin therapy. Pramlintide is administered as a subcutaneous injection along with insulin and helps achieve lower blood sugar levels after meals, helps reduce fluctuation of blood sugar levels throughout the day, and improves hemoglobin A1C levels. Incretin mimetics: Incretin mimetics promote insulin secretion by the pancreas and mimics other blood sugar level lowering actions that naturally occur in the body. Exenatide (Byetta) was the first incretin mimetic agent approved in the United States. It is indicated for diabetes mellitus type 2 in addition to metformin or a sulfonylurea when these agents have not attained blood sugar level control alone. Insulins: Synthetic hyuman insulin is now the only type of insulin available in the United States; it is less likely to cause allergic reactions than animal-derived varieties of insulin used in the past. The type of insulin chosen to customize treatment for an individual is based on the goal of providing optimal blood sugar control. Different types of insulin are available and categorized according to their times of action onset and duration. Commercially prepared mixtures of insulin may also be used to provide constant (basal) control and immediate control. Examples of rapid-acting insulins Regular insulin (Humulin R, Novolin R) Insulin lispro (Humalog) Insulin aspart (Novolog) Insulin glulisine (Apidra) Prompt insulin zinc (Semilente, slightly slower acting) Examples of intermediate-acting insulins Isophane insulin, neutral protamine Hagedorn (NPH) (Humulin N, Novolin N) Insulin zinc (Lente) Examples of long-acting insulins Extended insulin zinc insulin (Ultralente) Insulin glargine (Lantus) Insulin detemir (Levemir)
In more extreme cases, a pancreas transplant can restore proper glucose regulation. However, the surgery and accompanying immunosuppression required is considered by many physicians to be more dangerous than continued insulin replacement therapy, so is generally only used with or some time after a kidney transplant. One reason for this is that introducing a new kidney requires taking immunosuppressive drugs such as cyclosporine. Nevertheless this allows the introduction of a new, functioning pancreas to a patient with diabetes without any additional immunosuppressive therapy. However, pancreas transplants alone can be wise in patients with extremely labile type 1 diabetes mellitus.[34]
Experimental replacement of beta cells (by transplant or from stem cells) is being investigated in several research programs. Islet cell transplantation is less invasive than a pancreas transplant, which is currently the most commonly used approach in humans.
In one variant of this procedure, islet cells are injected into the patient's liver, where they take up residence and begin to produce insulin. The liver is expected to be the most reasonable choice because it is more accessible than the pancreas, and islet cells seem to produce insulin well in that environment. The patient's body, however, will treat the new cells just as it would any other introduction of foreign tissue, unless a method is developed to produce them from the patient's own stem cells or an identical twin is available who can donate stem cells. The immune system will attack the cells as it would a bacterial infection or a skin graft. Thus, patients now also need to undergo treatment involving immunosuppressants, which reduce immune system activity.
Recent studies have shown islet cell transplants have progressed to the point where 58% of the patients in one study were insulin-independent one year after transplantion.[35] Scientists in New Zealand with Living Cell Technologies are currently in human trials with Diabecell, placing pig islets within a protective capsule derived of seaweed which enables insulin to flow out and nutrients to flow in, while protecting the islets from immune system attack via white blood cells.
Stem Cell Educator Therapy induces immune balance by using cord blood-derived multipotent stem cells[36] with embryonic and hematopoietic characteristics. A closed-loop system that circulates a patient's blood through a blood cell separator, briefly co-cultures the patient's lymphocytes with adherent cord blood stem cells in vitro, and returns the educated lymphocytes (but not the cord blood stem cells) to the patient's circulation.[37] Through the Stem Cell Education process the patient's lymphocytes are modified by the Autoimmune Regulator AIRE that activates certain genes due to contact with the cord blood stem cells.
The clinical trial (NCT01350219) reveals that a single treatment with the Stem Cell Educator provides lasting reversal of autoimmunity that allows improvement of metabolic control[38] in subjects with long-standing type 1 diabetes. The on-going phase II clinical study about Stem Cell Educator Therapy has proved 100% effectiveness in type 1 diabetics, even in patients who lost the ability to produce their own insulin (C-peptide < 0,01 µg/l before treatment).
After treatment, the increased expression of co-stimulating molecules (specifically, CD28 and ICOS), increases in the number of CD4+CD25+Foxp3+ Tregs, and restoration of Th1/Th2/Th3 cytokine balance indicate this therapy reverses autoimmunity, induces tolerance and promotes regeneration of islet beta cells[39] without showing any adverse effects so far.
Successful immune modulation by cord blood stem cells and the resulting clinical improvement in patient status may have important implications for other autoimmune diseases but does not raise any safety or ethical issues.
Depression and depressive symptoms are generally more common in people living with Type 1 Diabetes. One review article suggested that the prevalence rate of depression is more than three times higher in Diabetes than none Diabetics; an average prevalence of 12% was found (range of 5.8%-43.4% in studies reviewed)[40] Women with Type 1 Diabetes are more likely to be depressed than men with Type 1 Diabetes, [41] and an increased incidence of depression has also been associated with youth with Type 1 Diabetes.[42] According to the Canadian Diabetes Association, 15% of people living with Diabetes have major depression.[43] Psychological distress is also reported in the parents of youth with Type 1 Diabetes.[44] Recent evidence has suggested that reduced pre-frontal cortical thickness is associated with depression in people with Type 1 Diabetes. These neurological changes may be caused by long-term reduced glycemic control and may increase risk of depression.[45]
Recent research has found that eating disorders are more common in females with Type 1 Diabetes[46] (prevalence = 10.15%) than in females without it (prevalence = 4.5%), as were sub-threshold eating disorders (13.8% vs. 7.6%)[47] Some participants (11.0%) in the same study reported manipulating insulin dosages to promote weight loss. Higher blood-sugar levels are associated with polyuria and reduced appetite, which can result in weight loss. Similarly, mean hemoglobin A1c levels were higher in participant with a DSM-IV disorder (9.4%) than those without (8.6%). This behavior was reported by 42% of participant who had a DSM-IV disorder.
Results from recent research suggest that people with Type 1 Diabetes may neglect precise self-care due to social fear related to fear of hypoglycemia. [48] Type 1 Diabetics may also neglect physical activity due to reduced perceived position effects as well as increased perceived negative aspects of that activity.[49]
Complications of poorly managed type 1 diabetes mellitus may include cardiovascular disease, diabetic neuropathy, and diabetic retinopathy, among others. However, cardiovascular disease[50] as well as neuropathy[51] may have an autoimmune basis, as well.
Studies conducted in the United States[52] and Europe[53] showed that drivers with type 1 diabetes had twice as many collisions as their nondiabetic spouses, demonstrating the increased risk of driving collisions in the type 1 diabetes population. Diabetes can compromise driving safety in several ways. First, long-term complications of diabetes can interfere with the safe operation of a vehicle. For example, diabetic retinopathy (loss of peripheral vision or visual acuity), or peripheral neuropathy (loss of feeling in the feet) can impair a driver’s ability to read street signs, control the speed of the vehicle, apply appropriate pressure to the brakes, etc.
Second, hypoglycemia can affect a person’s thinking processes, coordination, and state of consciousness.[54][55] This disruption in brain functioning, neuroglycopenia, can impair driving ability.[54][56] A study involving people with type 1 diabetes found that individuals reporting two or more hypoglycemia-related driving mishaps differ physiologically and behaviorally from their counterparts who report no such mishaps.[57] For example, during hypoglycemia, drivers who had two or more mishaps reported fewer warning symptoms, their driving was more impaired, and their body released less epinephrine (a hormone that helps raise BG). Additionally, individuals with a history of hypoglycemia-related driving mishaps appear to use sugar at a faster rate[58] and are relatively slower at processing information.[59] These findings indicate that although anyone with type 1 diabetes may be at some risk of experiencing disruptive hypoglycemia while driving, there is a subgroup of type 1 drivers who are more vulnerable to such events.
Given the above research findings, drivers with type 1 diabetes and a history of driving mishaps are recommended to never drive when their BG is less than 70 mg/dl. Instead, these drivers are advised to treat hypoglycemia and delay driving until their BG is above 90 mg/dl.[57] Such drivers should also learn as much as possible about what causes their hypoglycemia, and use this information to avoid future hypoglycemia while driving.
Studies funded by the National Institutes of Health (NIH) have demonstrated that face-to-face training programs designed to help individuals with type 1 diabetes better anticipate, detect, and prevent extreme BG can reduce the occurrence of future hypoglycemia-related driving mishaps.[60][61][62] An internet-version of this training has also been shown to have significant beneficial results.[63] Additional NIH funded research to develop internet interventions specifically to help improve driving safety in drivers with type 1 diabetes is currently underway.[64]
Type 1 diabetes causes an estimated 5–10% of all diabetes cases[65] or 11–22 million worldwide.[23] In 2006 it affected 440 thousand children under 14 years of age and was the primary cause of diabetes in those less than 10 years of age.[66] The incidence of type 1 diabetes has been increasing by about 3% per year.[66]
Rates vary widely by country. In Finland, the incidence is a high of 35 per 100,000 per year, in Japan and China a low of 1 to 3 per 100,000 per year, and in Northern Europe and the U.S., an intermediate of 8 to 17 per 100,000 per year.[4][67]
Type 1 diabetes was previously known as juvenile diabetes to distinguish it from type 2 diabetes, which generally has a later onset; however, the majority of new-onset type 1 diabetes is seen in adults. Studies using antibody testing (glutamic acid decarboxylase antibodies, islet cell antibodies, and insulinoma-associated autoantibodies) to distinguish between type 1 and type 2 diabetes demonstrate that most new-onset type 1 diabetes is seen in adults. Adult-onset type 1 autoimmune diabetes is two to three times more common than classic childhood-onset autoimmune diabetes.[68]
In the US in 2008, about one million people were diagnosed with type 1 diabetes. The disease was estimated to cause $10.5 billion in annual medical costs ($875 per month per diabetic) and an additional $4.4 billion in indirect costs ($366 per month per diabetic).[69]
The Juvenile Diabetes Research Foundation funds type 1 diabetes research and has offices in the UK, Denmark, USA, Canada, Australia, Israel, Mexico and India. The Diabetes Research Institute Foundation was founded by a group of parents of children with diabetes and funds research for a cure for type 1 diabetes. The International Diabetes Federation is a worldwide alliance of over 160 countries to address diabetes research and treatment.
The American Diabetes Association funds some type 1 research along with other a variety of diabetes-related research (not necessarily cure-specific), including type 2 diabetes, gestational diabetes and others) that looks at treatments and prevention, as well as some cure-specific research. Diabetes Australia is involved in promoting research and education in Australia on both type 1 and type 2 diabetes. The Canadian Diabetes Association is involved in educating, researching, and sustaining type 1 diabetes patients in Canada. Pacific Northwest Diabetes Research Institute conducts clinical and basic research on type 1 and type 2 diabetes.
Injections with a vaccine containing GAD65, an autoantigen involved in type 1 diabetes, has in clinical trials delayed the destruction of beta cells when treated within six months of diagnosis.[9] Patients treated with the substance showed higher levels of regulatory cytokines, thought to protect the beta cells.[70] Phase III trials are under way in the USA[71] and in Europe.[72][73][74] Two prevention studies, where the vaccine is given to persons who have not yet developed diabetes are underway.[75][76][77]
If a biochemical mechanism can be found to prevent the immune system from attacking beta cells, it may be administered to prevent commencement of diabetes type 1. Several groups are trying to achieve this by causing the activation state of the immune system to change from type 1 T helper cell (Th1) state ("attack" by killer T Cells) to Th2 state (development of new antibodies). This Th1-Th2 shift occurs via a change in the type of cytokine signaling molecules being released by T-cells. Instead of proinflammatory cytokines, the T-cells begin to release cytokines that inhibit inflammation.[78] This phenomenon is commonly known as "acquired immune tolerance".
Insulin-dependent diabetes characterized by dramatic and recurrent swings in glucose levels, often occurring for no apparent reason, is sometimes known as brittle diabetes, unstable diabetes or labile diabetes, although some experts say the "brittle diabetes" concept "has no biologic basis and should not be used".[79] The results of such swings can be irregular and unpredictable hyperglycemias, frequently involving ketosis, and sometimes serious hypoglycemias. Brittle diabetes occurs no more frequently than in 1% to 2% of diabetics.[80] An insulin pump may be recommended for brittle diabetes to reduce the number of hypoglycemic episodes and better control the morning rise of blood sugar due to the dawn phenomenon.[81] In a small study, 10 of 20 brittle diabetic patients aged 18-23 years who could be traced had died within 22 years, and the remainder, though suffering high rates of complications, were no longer brittle.[82] These results were similar to those of an earlier study by the same authors which found a 19% mortality in 26 patients after 10.5 years.[83]
Because brittle diabetes is defined as "episodes of hypoglycemia or hyperglycemia that, whatever their cause, constantly disrupt a patient's life", it can have many causes, some of which include:[84]
One of these biological factors is the production of insulin autoantibodies. High antibody titers can cause episodes of hyperglycemia by neutralizing the insulin, cause clinical insulin resistance requiring doses of over 200 IU/day. However, antibodies may also fail to buffer the release of the injected insulin into the bloodstream after subcutaneous injection, resulting in episodes of hypoglycemia. In some cases, changing the type of insulin administered can resolve this problem.[84] There have been a number of reports that insulin autoantibodies can act as a "sink" for insulin and affect the time to peak, half-life, distribution space, and metabolic clearance, though in most patients these effects are small.[85]
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リンク元 | 「不安定型糖尿病」「brittle型糖尿病」「ブリットル型糖尿病」「unstable diabetes」 |
関連記事 | 「brittle」「diabetes」 |
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