Presentation on theme: "Targeting the Underlying Pathophysiology of Type 2 Diabetes"— Presentation transcript:
1Targeting the Underlying Pathophysiology of Type 2 Diabetes
2Aim Provide practical guidance on improving diabetes care through highlighting the need to:understand that insulin resistance and b-cell dysfunction are core defects of type 2 diabetesaddress the underlying pathophysiology
3Type 2 diabetes Characterized by chronic hyperglycemia Associated with microvascular and macrovascular complicationsGenerally arises from a combination of insulin resistance and -cell dysfunctionType 2 diabetes is a metabolic disorder with multiple causes, characterized by chronic hyperglycemia with disturbances of carbohydrate, fat and protein metabolism. It generally results from a combination of insulin resistance and loss of -cell function.1Insulin resistance places an increased secretory demand upon the -cell, leading to -cell dysfunction as the disease progresses.2In the long term, type 2 diabetes affects a number of organs and is associated with microvascular complications such as retinopathy, nephropathy and neuropathy. In addition, individuals with type 2 diabetes are at increased risk of macrovascular disease.1Often diagnosis of type 2 diabetes is made after the condition has been present for some years. In fact, more than 50% of individuals have evidence of vascular disease at diagnosis.31Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications. Department of Noncommunicable Disease Surveillance, World Health Organization, Geneva Available at:2International Diabetes Center (IDC), Minneapolis, Available at:3Laakso M. Int J Clin Pract Suppl. 2001; 121:8–12.Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications. Department of Noncommunicable Disease Surveillance, World Health Organization, Geneva Available at:
4What is insulin resistance? Major defect in individuals with type 2 diabetes1Reduced biological response to insulin1–3Strong predictor of type 2 diabetes4Closely associated with obesity5IRInsulin resistance is the inability of the body to use its own insulin.Insulin resistance is present to varying degrees in a high proportion of the general population.1Insulin resistance may lead to impaired glucose tolerance (IGT) and eventually to the development of type 2 diabetes.2,3> 80% of individuals with type 2 diabetes are insulin resistant.4Insulin resistance is also a strong predictor for the development of type 2 diabetes.4Many people with type 2 diabetes are obese – this can be up to ~85% in some populations,5 which may explain their insulin resistance.1American Diabetes Association. Diabetes Care 1998; 21:310–314.2Beck-Nielsen H & Groop LC. J Clin Invest 1994; 94:1714–1721.3Bloomgarden ZT. Clin Ther 1998; 20:216–231.4Haffner SM, et al. Circulation 2000; 101:975–980.5Boden G. Diabetes 1997; 46:3–10.1American Diabetes Association. Diabetes Care 1998; 21:310–314.2Beck-Nielsen H & Groop LC. J Clin Invest 1994; 94:1714– Bloomgarden ZT. Clin Ther 1998; 20:216–231.4Haffner SM, et al. Circulation 2000; 101:975–980. 5Boden G. Diabetes 1997; 46:3–10.
5What is -cell dysfunction? Major defect in individuals with type 2 diabetesReduced ability of -cells to secrete insulin in response to hyperglycemiaTogether with insulin resistance, -cell dysfunction is one of the two major defects involved in development of type 2 diabetes1 and is often inherited.-cell dysfunction may be a consequence of insulin resistance, but also occurs in insulin-sensitive individuals.2In the insulin-resistant state, the pancreas is able to initially compensate for insulin resistance through increased production of insulin.1 With time, however, the -cells are unable to maintain increased insulin secretion leading to the development of impaired glucose tolerance and type 2 diabetes.11DeFronzo RA, et al. Diabetes Care 1992; 15:318–354.2Haffner SM, et al. Circulation 2000; 101:975–980.DeFronzo RA, et al. Diabetes Care 1992; 15:318–354.
6Genetic susceptibility, obesity, Western lifestyle Insulin resistance and -cell dysfunction are core defects of type 2 diabetesInsulinresistanceGenetic susceptibility,obesity, Western lifestyleType 2 diabetesIRb-celldysfunctionA number of factors, both genetic and environmental, influence the development of insulin resistance and -cell dysfunction. In addition to the risk posed by inherited factors, a Western lifestyle (i.e. sedentary lifestyle, high-fat diet) can contribute to obesity, a strong risk factor for insulin resistance.Insulin resistance at the tissue level contributes significantly to hyperglycemia and is due primarily to abnormalities in the way that the effects of insulin are carried from the receptor on the cell’s surface to intracellular proteins that regulate glucose transport. The consequences of insulin resistance include reduced glucose uptake into fat and muscle, and increased glucose production by the liver.1-cell dysfunction is characterized by a reduced ability to respond to raised glucose levels leading to reduced insulin secretion, which in turn results in chronic hyperglycemia.Together, these two factors often lead to the development of type 2 diabetes, and so are key targets for therapeutic intervention.1Rhodes CJ & White MF. Eur J Clin Invest 2002; 32 (Suppl. 3):3–13.Rhodes CJ & White MF. Eur J Clin Invest 2002; 32 (Suppl. 3):3–13.
7How do insulin resistance and -cell dysfunction combine to cause type 2 diabetes? Abnormalglucose toleranceHyperinsulinemia,then -cell failureNormal IGT* Type 2 diabetesPost-prandial glucoseInsulin resistanceIncreased insulin resistanceFasting glucoseHyperglycemiaInsulinsecretion*IGT = impaired glucose toleranceAdapted from Type 2 Diabetes BASICS. International Diabetes Center (IDC), Minneapolis, 2000.Over time, changes in insulin resistance and secretion lead to the onset of type 2 diabetes.In the early stages, as insulin resistance rises, there is a compensatory increase in insulin secretion and glucose levels remain normal (normoglycemia).In the long term, however, as the b-cells begin to fail, insulin secretion falls, IGT and hyperglycemia become apparent and frank type 2 diabetes develops.IGT may be defined as higher than normal blood glucose levels, but not high enough to be called diabetes. People with IGT may or may not go on to develop diabetes.Glucose levels both before (fasting) and after (post-prandial) meals increase steadily as the individual progresses from normoglycemia to IGT and, finally, type 2 diabetes.International Diabetes Center (IDC), Minneapolis, 2000.
8How is insulin resistance measured? Several methods exist, including:continuous sampling of insulin/glucose1gold standard, but impractical for large-scale usesingle measure of insulin/glucose2simple estimate from fasting insulin and glucoseuseful for assessment on a larger scaleMethods to measure insulin resistance include challenging individuals with glucose (known as the clamp) and the mathematical homeostasis model assessment (HOMA).1,2The clamp technique is considered the ‘gold standard’ for measuring insulin resistance, but this method is demanding and expensive and, therefore, not appropriate for large-scale studies.1HOMA is more appropriate where rapid or repeated assessment of insulin sensitivity is required on a larger scale.1,31Bergman RN, et al. Eur J Clin Invest 2002; 32 (Suppl. 3):35–45.2Matthews DR, et al. Diabetologia 1985; 28:412–419.3Bonora E, et al. Diabetes Care 2000; 23:57–63.1Bergman RN, et al. Eur J Clin Invest 2002; 32 (Suppl. 3):35–45.2Matthews DR, et al. Diabetologia 1985; 28:412–419.
9More than 80% of patients progressing to type 2 diabetes are insulin resistant Insulin sensitive; low insulin secretion (16%)Insulin sensitive; good insulin secretion (1%)Insulin resistant; low insulin secretion (54%)83%The 7-year follow-up of the San Antonio Heart Study revealed that 195 of 1,734 subjects (11%) progressed to type 2 diabetes.These 195 converters could be characterized into four groups:insulin resistant; low insulin secretion (54%)insulin resistant; good insulin secretion (29%)insulin sensitive; low insulin secretion (16%)insulin sensitive; good insulin secretion (1%).In the study, insulin resistance was most strongly associated with progression to type 2 diabetes, with 83% of converters being insulin resistant.The lowest risk of developing type 2 diabetes was in subjects who were insulin sensitive combined with good insulin secretory capacity (1%).Haffner SM, et al. Circulation 2000; 101:975–980.Insulin resistant; good insulin secretion (29%)Haffner SM, et al. Circulation 2000; 101:975–980.
10Insulin resistance – reduced response to circulating insulin LiverMuscleAdipose tissue Glucose output Glucose uptake Glucose uptakeThe consequences of insulin resistance at the tissue level include reduced glucose uptake into peripheral sites, that is, fat and muscle.Combined with excessive glucose output by the liver, this leads to hyperglycemia.Hyperglycemia
11Overall, 75% of patients with type 2 diabetes die from cardiovascular disease Most deaths in type 2 diabetes are due to cardiovascular disease, especially coronary heart disease.1Overall mortality for coronary heart disease is two to four times higher in diabetic individuals than in those without diabetes.2IGT is also an independent risk factor for cardiovascular disease.31Gray RP & Yudkin JS. Cardiovascular disease in diabetes mellitus. In Textbook of Diabetes 2nd Edition, Blackwell Sciences.2Haffner SM & Miettinen H. Am J Med 1997; 103:152–162.3Qiao Q, et al. Diabetes Care 2003; 26:2910–2914.Gray RP & Yudkin JS. Cardiovascular disease in diabetes mellitus. In Textbook of Diabetes 2nd Edition, Blackwell Sciences.
12Odds ratio for incident CVD Total cholesterol: HDL cholesterol Insulin resistance is as strong a risk factor for cardiovascular disease as smoking220.127.116.11Odds ratio for incident CVD1.21.0Insulin resistance is strongly associated with the incidence of cardiovascular disease.1In a prospective analysis of 1,326 subjects in the Verona Diabetes Complications Study, insulin resistance (as measured by estimates of HOMA) was confirmed as an independent risk factor for cardiovascular disease.2Moreover, insulin resistance was as strong a risk factor as smoking. Both of these factors carried a greater risk for developing cardiovascular disease than either age or total:HDL cholesterol ratio.21Hanley AJ, et al. Diabetes Care 2002; 25:1177–1184.2Bonora E, et al. Diabetes Care 2002; 25:1135–118.104.22.168AgeSmokingTotal cholesterol: HDL cholesterolInsulin resistanceBonora E, et al. Diabetes Care 2002; 25:1135–1141.
13Insulin resistance is closely linked to cardiovascular disease Present in > 80% of people with type 2 diabetes1Approximately doubles the risk of a cardiac event2Implicated in almost half of CHD events in individuals with type 2 diabetes2IRInsulinresistanceMore than 80% of individuals with type 2 diabetes are insulin resistant.1Insulin resistance almost doubles the risk of a cardiovascular event.2Insulin resistance is implicated in almost 50% of annual cardiovascular events in individuals with type 2 diabetes, compared with only 6% in non-diabetic individuals.2Preventing or modifying insulin resistance should decrease the burden of cardiovascular disease.21Haffner SM, et al. Circulation 2000; 101:975–980.2Strutton D, et al. Am J Manag Care 2001; 7:765–773.1Haffner SM, et al. Circulation 2000; 101:975–980.2Strutton D, et al. Am J Man Care 2001; 7:765–773.
14Insulin resistance is linked to a range of cardiovascular risk factors AtherosclerosisHyperglycemiaDyslipidemiaHypertensionDamage to blood vesselsClotting abnormalitiesInflammationInsulinresistanceIRInsulin resistance is closely linked to a number of cardiovascular risk factors, collectively known as the Metabolic Syndrome or Insulin Resistance Syndrome.Components of the Metabolic Syndrome include well known cardiovascular risk factors such as hyperglycemia, dyslipidemia and hypertension. Additional cardiovascular risk factors, that is damage to blood vessels (endothelial dysfunction), clotting abnormalities (hypofibrinolysis) and inflammation, have also been recognized as key components of the Metabolic Syndrome.Together, the cluster of cardiovascular risk factors that make up the Metabolic Syndrome significantly increases the risk of atherosclerosis.Zimmet P. Trends Cardiovasc Med 2002; 12:354–362.Zimmet P. Trends Cardiovasc Med 2002; 12:354–362.
15~90% of people with type 2 diabetes are overweight or obese ~90% of people with type 2 diabetes are overweight or obeseThe World Health Organization reports that around 90% of individuals with type 2 diabetes are overweight or obese.1Fat distribution in the body may be either abdominal (android or central obesity – often referred to as ‘apple-shaped’) or affect the lower body (mainly thighs and buttocks; gynoid obesity – often referred to as ‘pear-shaped’).2Central obesity (indicated by, for example, high waist:hip ratio; that is waist:hip ratio > 0.90 for men, > 0.85 for women) is a strong risk factor for insulin resistance.31 World Health Organization,2Basdevant A, et al. Presse Med 1987; 16:167–170.3Ascaso JF, et al. Eur J Intern Med 2003; 14:101–106.World Health Organization,
16How is -cell function measured? -cell function is difficult to measure and most methods are impractical for large-scale use1Homeostasis model assessment (HOMA) provides a simple estimate of -cell function2Proinsulin:insulin ratio is sometimes used as a marker of -cell dysfunction1Over the years, a number of techniques have been used to assess -cell function.1However, -cell function is difficult to measure and most of these methods are impractical for large-scale use.HOMA is more appropriate for large-scale studies and provides a simple estimate of -cell function from fasting insulin and glucose.2Sometimes used as a marker for -cell dysfunction, the ratio of proinsulin (the precursor of insulin that is converted to insulin) to total insulin provides a measure of the efficiency of proinsulin processing.11Bergman RN, et al. Eur J Clin Invest 2002; 32 (Suppl. 3):35–45.2Matthews DR, et al. Diabetologia 1985; 28:412–419.1Matthews DR, et al. Diabetologia 1985; 28:412–419.2Bergman RN, et al. Eur J Clin Invest 2002; 32 (Suppl. 3):35–45.
17Why does the -cell fail? Oversecretion of insulin to compensate for insulin resistance1,2Glucotoxicity2Lipotoxicity3Chronic hyperglycemiaPancreasHigh circulating free fatty acidsAt physiological levels, both glucose and free fatty acids stimulate insulin secretion.1,2-cell dysfunction may occur as a result of genetic factors.Chronic hyperglycemia, however, may negatively affect the -cell through a process known as glucotoxicity.2Glucotoxicity is the ability of glucose to stimulate the death of -cells.2Similarly, chronically elevated free fatty acids have a lipotoxic effect upon the pancreas, inducing -cell dysfunction.3Lipotoxicity is the ability of free fatty acids to stimulate the death of -cells.3Oversecretion of insulin to compensate for insulin resistance also contributes to -cell dysfunction.1Boden G & Shulman GI. Eur J Clin Invest 2002; 32:14–23. 2Kaiser N, et al. J Pediatr Endocrinol Metab 2003; 16:5–22. 3Finegood DT & Topp B. Diabetes Obes Metab 2001; 3 (Suppl. 1):S20–S27.-celldysfunction1Boden G & Shulman GI. Eur J Clin Invest 2002; 32:14–23.2Kaiser N, et al. J Pediatr Endocrinol Metab 2003; 16:5–22.3Finegood DT & Topp B. Diabetes Obes Metab 2001; 3 (Suppl. 1):S20–S27.
18Glycemic control declines over time Years from randomizationDietSulfonylurea or insulin6.2% upper limit of normal rangeMedian HbA1c (%)9876The UK Prospective Diabetes Study (UKPDS) was started in 1977 and was designed to establish whether intensive blood glucose control could reduce the risk of macrovascular or microvascular complications in patients with type 2 diabetes.In the diet-treated group, HbA1c increased steadily over the course of the study.In the sulfonylurea- or insulin-treated group, there was an initial decrease in HbA1c during the first year of the study, followed by a subsequent, progressive increase similar to that seen in the diet-treated group.UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837–853.UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837–853.
19Loss of -cell function occurs before diagnosis 100Up to 50% loss80Diagnosis60-cell function (%)4020Extrapolation of the observed rate of decline of -cell function in diet-treated subjects in the UKPDS suggests that loss of -cell function can begin at least 10 years before diagnosis.In the UKPDS, long-term increases in fasting plasma glucose were accompanied by progressive -cell dysfunction as assessed by HOMA.1Mean -cell function was already less than 50% at diagnosis,2 and none of the therapies used in the study (sulfonylureas, metformin and insulin) were able to prevent or delay the progressive deterioration of -cell function.1On average, -cell function declines by 1% per year with normal aging, compared with 4% per year in diabetes.1,31UKPDS Group. UKPDS 16. Diabetes 1995; 44:1249–1258.2Holman RR. Diabetes Res Clin Prac 1998; 40 (Suppl.):S21–S25.3Chiu KC, et al. Clin Endocrinol 2000; 53:569–575.-10-9-8-7-6-5-4-3-2-1123456Time from diagnosis (years)Holman RR. Diabetes Res Clin Prac 1998; 40 (Suppl.):S21–S25.
20Oral antidiabetic agents – do they target insulin resistance and -cell dysfunction?
21Barriers to achieving good glycemic control Inadequate targeting of underlying pathophysiologyA number of factors are likely to contribute to the complexities of controlling blood glucose levels in individuals with type 2 diabetes.The Global Partnership has identified several key areas that can help the diabetes care team to increase the proportion of individuals achieving good glycemic control and thus decrease the risk of complications.These include the need to target the underlying pathophysiology of type 2 diabetes.
22Primary sites of action of oral antidiabetic agents Carbohydrate breakdown/ absorption-glucosidase inhibitors Insulin secretionSulfonylureas/ meglitinidesBiguanidesThiazolidinediones-glucosidase inhibitors (e.g. acarbose) – delay digestion and absorption of carbohydrates in the gastrointestinal tract.1,2Sulfonylureas and meglitinides – stimulate insulin secretion from the pancreas.1,2Biguanides (e.g. metformin) – suppress liver glucose output, enhance insulin sensitivity in the liver and stimulate insulin-mediated glucose disposal. They do not stimulate insulin secretion.1,2Thiazolidinediones – decrease insulin resistance in fat, muscle and liver. In addition, they improve estimates of -cell function.1,21Kobayashi M. Diabetes Obes Metab 1999; 1 (Suppl. 1):S32–S40.2Nattrass M & Bailey CJ. Baillieres Best Pract Res Clin Endocrinol Metab 1999; 13:309–329. Glucose output Insulin resistance Insulin resistanceKobayashi M. Diabetes Obes Metab 1999; 1 (Suppl. 1):S32–S40.Nattrass M & Bailey CJ. Baillieres Best Pract Res Clin Endocrinol Metab 1999; 13:309–329.
23The dual action of thiazolidinediones reduces HbA1c IR+Insulinresistance-cellfunctionClinical studies have shown that treatment with the thiazolidinediones – rosiglitazone and pioglitazone – significantly decreases insulin resistance and improves -cell function in people with type 2 diabetes (as estimated by HOMA).1,21Lebovitz HE, et al. J Clin Endocrinol Metab 2001; 86:280–288.2Rosenblatt S, et al. Coron Artery Dis 2001; 12:413–423.HbA1cLebovitz HE, et al. J Clin Endocrinol Metab 2001; 86:280–288.
24Potential to prevent progression to type 2 diabetes in at-risk women Troglitazone reduced progression to type 2 diabetes by > 50%Troglitazone* 400 mg/day0.6Placebo0.50.4Proportion with diabetes0.30.2The Troglitazone in Prevention of Diabetes (TRIPOD) study highlighted the potential of thiazolidinediones to reduce progression to type 2 diabetes in at-risk individuals.In this study, women with previous gestational diabetes were treated with placebo (n = 133) or troglitazone 400 mg/day (n = 133) for 5 years.Treatment with troglitazone delayed or prevented the onset of type 2 diabetes (P = 0.009) by at least 50%.Average annual diabetes incidence rates were 12% and 5% in women assigned to placebo and troglitazone, respectively (P < 0.01).This protective effect was associated with preservation of pancreatic b-cell function and seemed to be due to a reduction in the stress placed on b-cells by chronic insulin resistance.Protection from diabetes in the troglitazone group persisted 8 months after study medications were stopped, suggesting that the effect was mediated through changes in the natural history of the condition, rather than through effects on circulating glucose levels.Although troglitazone is no longer available, it is generally thought that other agents in this class are likely to have the same effect.Buchanan TA, et al. Diabetes 2002; 51:2796–2803.0.10.0102030405060Time on trial (months)*Troglitazone is no longer availableBuchanan TA, et al. Diabetes 2002; 51:2796–2803.
25Can thiazolidinediones delay progression from IGT to T2DM? PlaceboRosiglitazone 8 mg/day100T2DM11%80IGT56%60Subjects (%)IGTIGTIGT100%89%100%40Thiazolidinediones have the potential to delay the progression from IGT to type 2 diabetes.In a study of subjects with IGT, randomized to rosiglitazone 8 mg/day (n = 9) or placebo (n = 9), participants underwent an oral glucose tolerance test (OGTT, which measures the body's ability to metabolize glucose) at screening and after 12 weeks’ treatment.In the rosiglitazone group, 44% developed normal glucose tolerance (NGT) and 56% retained IGT by week 12 (P = versus placebo). By contrast, in the placebo group, no subjects normalized their glucose tolerance; 11% developed type 2 diabetes and 89% remained IGT.Bennett SM, et al. Diabet Med 2004; 21:415–422.NGT2044%ScreeningWeek 12ScreeningWeek 12Bennett SM, et al. Diabet Med 2004; 21:415–422.
26Myocardial infarction Myocardial infarction Does decreasing insulin resistance decrease macrovascular complications?Myocardial infarctionNot significantAll-cause mortalitySulfonylureas/insulinMyocardial infarctionSignificantAll-cause mortalityMetformin21%8%39%36%The UKPDS showed that use of either sulfonylureas or insulin does not significantly reduce the risk of myocardial infarction (P = 0.11) or all-cause mortality (P = 0.49) in overweight patients compared with diet only.In contrast, metformin treatment significantly reduced the risk of myocardial infarction (P = 0.01) and all-cause mortality (P = 0.02) in overweight patients compared with diet only.The effect of metformin on macrovascular outcomes is believed to occur as a consequence of its weak insulin sensitizing effect.UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:854–865.UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:854–865.
27Insulin sensitizers reduce cardiovascular events in type 2 diabetes 60504012-month combined event rate (%)3020Insulin sensitizers are associated with reduced cardiovascular events in individuals with type 2 diabetes.Individuals were divided into two groups: insulin sensitizers (n = 50; thiazolidinediones or biguanides) or non-sensitizers (n = 67; insulin, sulfonylureas or diet).Clinical events were defined as target vessel revascularization (TVR), myocardial infarction (MI), non-TVR and death.After 12 months, treatment with an insulin sensitizer significantly reduced the combined event rate compared with treatment with non-sensitizers (P = 0.041) and reduced deaths (P = 0.049).Kao JA, et al. J Am Coll Cardiol 2004; 43:37A.10Non-sensitizersSensitizersKao JA, et al. J Am Coll Cardiol 2004; 43:37A.
28How can diabetes care and outcomes be improved? The Global Partnership recommends:Address the underlying pathophysiology, including treatment of insulin resistanceDel Prato S, et al. Int J Clin Pract 2005; 59:1345–1355.