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Query: UMLS:C0011860 (type 2 diabetes)
 57,723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The myenteric plexus of the gastrointestinal tract was investigated in the obese diabetic mouse, an animal model of human type 2 diabetes. Sections were immunostained by the avidin-biotin complex method, using a general nerve marker, protein gene product 9.5 (PGP 9.5), as well as antibodies to several important neurotransmitters. Computerized image analysis was used for quantification. When diabetic mice were compared with controls, no difference was found in the density of PGP 9.5-immunoreactive (IR) nerve fibres in antrum, duodenum or colon. In antrum and duodenum, diabetic mice showed a decreased number of vasoactive intestinal peptide (VIP)-IR neurons in myenteric ganglia as well a decreased relative volume density in myenteric plexus (though not significantly in antrum, p=0.073). No difference was found regarding VIP-IR nerves in colon. The volume density of nitric oxide synthase (NOS)-IR nerve fibres was decreased in antrum and duodenum of diabetic mice, whereas no difference was found in colon. The density of galanin-IR nerve fibres was decreased in duodenum. Whereas neuropeptide Y (NPY)- and vesicular acetylcholine transporter (VAChT)-IR nerve fibres was increased in density in colon of diabetic mice, no difference was found in antrum and duodenum. Regarding substance P, there was no difference between diabetic and control mice in antrum, duodenum or colon. The present study shows that gut innervation is affected in this animal model of human type 2 diabetes. It is possible that the present findings may have some relevance for the gastrointestinal dysfunctions seen in patients with type 2 diabetes.
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PMID:Myenteric plexus of obese diabetic mice (an animal model of human type 2 diabetes). 1119 91

Mutations in the glucokinase (GK) gene cause two different diseases of blood glucose regulation: maturity onset diabetes of the young, type 2 (MODY-2) and persistent hyperinsulinemic hypoglycemia of infancy (PHHI). To gain further understanding of the pathophysiology of these disorders, we have used both transgenic and gene-targeting strategies to explore the relationship between GK gene expression in specific tissues and the blood glucose concentration. These studies, which have included the use of aCre/loxP gene-targeting strategy to perform both pancreatic beta-cell- and hepatocyte-specific knockouts of GK, clearly demonstrate multiple, cell-specific roles for this hexokinase that, together, contribute to the maintainance of euglycemia. In the pancreatic beta cell, GK functions as the glucose sensor, determining the threshold for insulin secretion. Mice lacking GK in the pancreatic beta cell die within 3 days of birth of profound hyperglycemia. In the liver, GK facilitates hepatic glucose uptake during hyperglycemia and is essential for the appropriate regulation of a network of glucose-responsive genes. While mice lacking hepatic GK are viable, and are only mildly hyperglycemic when fasted, they also have impaired insulin secretion in response to hyperglycemia. The mechanisms that enable hepatic GK to affect beta-cell function are not yet understood. Thus, the hyperglycemia that occurs in MODY-2 is due to impaired GK function in both the liver and pancreatic beta cell, although the defect in beta-cell function is clearly more dominant. Whether defects in GK gene expression also impair glucose sensing by neurons in the brain or enteroendocrine cells in gut, two other sites known to express GK, remains to be determined. Moreover, whether the pathophysiology of PHHI also involves multitissue dysfunction remains to be explored.
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PMID:Cell-specific roles of glucokinase in glucose homeostasis. 1123 13

Changes in the numbers of serotonin- and substance P-immunoreactive (IR) cells occur in several animal models of diabetes. It is not known, however, whether these changes are a result of actual cell loss or are caused by modified gene expression in cells showing co-localization of serotonin and substance P. The pattern of mono- and co-expression of serotonin, as well as of substance P, was therefore investigated in gastrointestinal endocrine cells from animal models of human type 1 and type 2 diabetes, namely non-obese diabetic (NOD) and obese diabetic (ob/ob) mice. Immunocytochemical staining by the avidin-biotin complex method was performed for computerized image analysis of each cell type, and by immunofluorescence double staining to study co-localization. Tissues from antrum, proximal duodenum and distal colon were investigated. Co-localization of serotonin- and substance P-IR was found in all investigated parts of the gut. In antrum, substance P immunoreactivity was found exclusively in serotonin-IR cells. In both NOD and ob/ob mice there was a reduced number of substance P-IR cells, but an unchanged serotonin-IR cell count, which thus tallies with a shut-off of substance P expression in antral enterochromaffin cells. In duodenum, both diabetes models showed a decreased number of serotonin-IR cells. Furthermore there was a decreased number of substance P-IR cells in the type 2 model. The proportion of serotonin-IR cells showing substance P-immuno-reactivity was decreased in both diabetic models, thus indicating a shut-off of substance P-gene expression. However, this does not fully explain the changes in duodenum, but the diabetic state probably affects the number of mono-expressed cells as well. In colon, no change was found in diabetic mice regarding co-localization of substance P and serotonin. However, pre-diabetic NOD mice showed a decreased proportion of substance P in serotonin-IR cells, which might be explained by the increased number of serotonin-IR cells, combined with an unchanged number of substance P-IR cells. In conclusion, diabetic animal models of both type 1 and type 2 appear to have a combination of decreased expression of substance P in serotonin-IR cells of both antrum and duodenum, as well as a change in the number of mono-expressed cells. The pattern in colon, on the other hand, seems to be unaffected.
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PMID:Effect of diabetic state on co-localization of substance P and serotonin in the gut in animal models. 1133 94

We have previously reported that splanchnic glucose uptake, hepatic glycogen synthesis, and hepatic glucokinase activity are decreased in people with type 2 diabetes during intravenous glucose infusion. To determine whether these defects are also present during more physiological enteral glucose administration, we studied 11 diabetic and 14 nondiabetic volunteers using a combined organ catheterization-tracer infusion technique. Glucose was infused into the duodenum at a rate of 22 micromol. kg(-1). min(-1) while supplemental glucose was given intravenously to clamp glucose at approximately 10 mmol/l in both groups. Endogenous hormone secretion was inhibited with somatostatin, and insulin was infused to maintain plasma concentrations at approximately 300 pmol/l (i.e., twofold higher than our previous experiments). Total body glucose disappearance, splanchnic, and leg glucose extractions were markedly lower (P < 0.01) in the diabetic subjects than in the nondiabetic subjects. UDP-glucose flux, a measure of glycogen synthesis, was approximately 35% lower (P < 0.02) in the diabetic subjects than in the nondiabetic subjects. This was entirely accounted for by a decrease (P < 0.01) in the contribution of extracellular glucose because the contribution of the indirect pathway to hepatic glycogen synthesis was similar between groups. Neither endogenous and splanchnic glucose productions nor rates of appearance of the intraduodenally infused glucose in the portal vein differed between groups. In summary, both muscle and splanchnic glucose uptake are impaired in type 2 diabetes during enteral glucose administration. The defect in splanchnic glucose uptake appears to be due to decreased uptake of extracellular glucose, implying decreased glucokinase activity. Thus, abnormal hepatic and muscle (but not gut) glucose metabolism are likely to contribute to postprandial hyperglycemia in people with type 2 diabetes.
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PMID:Type 2 diabetes impairs splanchnic uptake of glucose but does not alter intestinal glucose absorption during enteral glucose feeding: additional evidence for a defect in hepatic glucokinase activity. 1137 36

Type 2 diabetes is a heterogeneous disorder characterized by defects in insulin secretion and action. Insulin resistance is a key feature of type 2 diabetes. However, insulin resistance alone does not appear to be sufficient to cause diabetes. Longitudinal studies have shown that the development of overt hyperglycemia is associated with a decline in beta-cell secretion. In patients with impaired glucose tolerance or in the early stages of type 2 diabetes, first-phase insulin release is almost invariably lost despite the enhancement of second-phase secretion. Both animal and human studies support the critical physiologic role of the first-phase of insulin secretion in the maintenance of postmeal glucose homeostasis. This effect is primarily mediated at the level of the liver, allowing prompt inhibition of endogenous glucose production (EGP) and thereby restraining the mealtime rise in plasma glucose. In type 2 diabetes, the loss of the early surge of insulin release is a precocious and quite common defect that plays a pathogenic role in postmeal hyperglycemia and one that may require specific therapeutic intervention. This becomes even more apparent if the negative impact of prandial glucose spikes is taken into consideration. Epidemiological evidence exists to indicate that 2-h postload plasma glucose levels are strongly associated with all-cause and cardiovascular mortality relative risk. Indeed the acute elevation of plasma glucose concentration triggers an array of tissue responses that may contribute to the development of diabetic complications. Considering that type 2 diabetes begins with meal-related hyperglycemia in many patients, it becomes apparent that normalization of postmeal plasma glucose levels should be the target for rational therapy and the goal in the early stages of the disease. If a primary goal of diabetes therapy is control of postmeal glucose excursion, then the regulation of glucose absorption from the gut and entry into the circulation is an important mechanism to consider. The restoration of the rapid increase in plasma insulin concentration may be quite an efficient therapeutic approach.
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PMID:The importance of first-phase insulin secretion: implications for the therapy of type 2 diabetes mellitus. 1142 29

The search for intestinal factors regulating the endocrine secretion of the pancreas started soon after the discovery of secretin, i.e. nearly 100 years ago. Insulinotropic factors of the gut released by nutrients and stimulating insulin secretion in physiological concentrations in the presence of elevated blood glucose levels have been named incretins. Of the known gut hormones only gastric inhibitory polypeptide (GIP) and glucagon-like polypeptide-1 (GLP-1 [7-36] amide) fulfill this definition.--The incretin effect (i.e. the ratio between the integrated insulin response to an oral glucose load and an isoglycaemic intravenous glucose infusion) is markedly diminished in patients with type 2 diabetes mellitus, while the plasma levels of GIP and GLP-1 and their responses to nutrients are in the normal range. Therefore, a reduced responsiveness of the islet B-cells to incretins has been postulated. This insensitivity of the diabetic B-cells towards incretins can be overcome by supraphysiological (pharmacological) concentrations of GLP-1 [7-36], however not of GIP. Accordingly, fasting and postprandial glucose levels can be normalized in patients with type 2 diabetes by infusions of GLP-1 [7-36]. Further studies revealed that this is partially due to the fact that GLP-1 [7-36]--in addition to its insulinotropic effect--also inhibits glucagon secretion and delays gastric emptying. These three antidiabetic effects qualify GLP-1 [7-36] as an interesting therapeutic tool, mainly for type 2 diabetes. However, because of its short plasma half life time natural GLP-1 [7-36] is not suitable for subcutaneous application. At present methods are being developed to improve the pharmacokinetics of GLP-1 by inhibition of the cleaving enzyme dipeptidyl peptidase IV (DPP-IV) or by synthesis of DPP-IV resistant GLP-1 analogues. Also naturally occurring GLP-1 analogues (for instance exendin-4) with a much longer half life time than GLP-1 [7-36] are being tested.--Thus, after 100 years of speculations and experimentations, incretins and their analogues are emerging as new antidiabetic drugs.
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PMID:The entero-insular axis in type 2 diabetes--incretins as therapeutic agents. 1146 May 78

Glucagon-like peptide-1 (GLP-1) is released from gut endocrine cells following nutrient ingestion and acts to regulate nutrient assimilation via effects on gastrointestinal motility, islet hormone secretion, and islet cell proliferation. Exogenous administration of GLP-1 lowers blood glucose in normal rodents and in multiple experimental models of diabetes mellitus. Similarly, GLP-1 lowers blood glucose in normal subjects and in patients with type 2 diabetes. The therapeutic utility of the native GLP-1 molecule is limited by its rapid enzymatic degradation by the serine protease dipeptidyl peptidase IV. This review highlights recent advances in our understanding of GLP-1 physiology and GLP-1 receptor signaling, and summarizes current pharmaceutical strategies directed at sustained activation of GLP-1 receptor-dependent actions for glucoregulation in vivo. Given the nutrient-dependent control of GLP-1 release, neutraceuticals or modified diets that enhance GLP-1 release from the enteroendocrine cell may exhibit glucose-lowering properties in human subjects. The utility of GLP-1 derivatives engineered for sustained action and/or DP IV-resistance, and the biological activity of naturally occurring GLP-1-related molecules such as exendin-4 is reviewed. Circumventing DP IV-mediated incretin degradation via inhibitors that target the DP IV enzyme represents a complementary strategy for enhancing GLP-1-mediated actions in vivo. Finally, the current status of alternative GLP-1-delivery systems via the buccal and enteral mucosa is briefly summarized. The findings that the potent glucose-lowering properties of GLP-1 are preserved in diabetic subjects, taken together with the potential for GLP-1 therapy to preserve or augment beta cell mass, provides a powerful impetus for development of GLP-1-based human pharmaceuticals.
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PMID:Development of glucagon-like peptide-1-based pharmaceuticals as therapeutic agents for the treatment of diabetes. 1147 75

Type 2 diabetes is a common disorder often accompanied by numerous metabolic abnormalities leading to a high risk of cardiovascular morbidity and mortality. Results from the UKPDS have confirmed that intensive glucose control delays the onset and retards the progression of microvascular disease and possibly of macrovascular disease in patients with type 2 diabetes. In the early stages of the disease, insulin resistance plays a major role in the development of hyperglycemia and other metabolic abnormalities, and patients with type 2 diabetes often benefit from measures to improve insulin sensitivity such as weight loss, dietary changes, and exercise. Later, the use of oral insulin secretagogues and insulin sensitizers as monotherapy and in combination helps maintain glycemia for varying periods of time. Ultimately, because of the progressive nature of the disease and the progressive decline in pancreatic beta-cell function, insulin therapy is almost always obligatory to achieve optimal glycemic goals. Not all patients are candidates for aggressive insulin management; therefore, the goals of therapy should be modified, especially in elderly individuals and those with co-morbid conditions. Candidates for intensive management should be motivated, compliant, and educable, without other major medical conditions and physical limitations that would preclude accurate and reliable HGM and insulin administration. In selected patients, combination therapy with insulin and oral antidiabetic medications can be an effective method for normalizing glycemia without the need for rigorous multiple-injection regimens. The patients for whom combination therapy is most commonly successful are those who do not achieve adequate glycemic control using daytime oral agents but who still show some evidence of responsiveness to the medications. Bedtime intermediate-acting or predinner premixed intermediate- and rapid-acting insulin is administered and progressively increased until the FPG concentration is normalized. If combination therapy is not successful, a split-mixed regimen of intermediate- and rapid-acting insulin equally divided between the prebreakfast and pre-dinner periods is advised for oese patients, and more intensive regimens are advised for thin patients. Insulin therapy is invariably associated with weight gain and hypoglycemia. The use of metformin or glitazones in combination with insulin has been demonstrated to have insulin-sparing properties. Also, metformin use may ameliorate weight gain. The use of continuous subcutaneous insulin infusion pumps can be particularly beneficial in treating patients with type 2 diabetes mellitus who do not respond satisfactorily to more conventional treatment strategies. Intraperitoneal insulin delivery systems hold considerable promise in type 2 diabetes because of their more physiologic delivery of insulin and their ability to inhibit hepatic glucose production selectively, with less peripheral insulinemia than with subcutaneous insulin injections. Newer insulin analogues such as the rapidly acting Lispro insulin and the peakless, long-acting glargine insulin are increasingly being used because of their unique physiologic pharmacokinetics. New developments such as inhaled and buccal insulin preparations will also make it easier for many patients to initiate and maintain a proper insulin regimen. Finally, a new generation of gut peptides such as amylin and GLP-1 will add a new dimension to glycemic control through modification of nutrient delivery and other mechanisms; however, the ultimate goal in the management of type 2 diabetes is the primary prevention of the disease. The Diabetes Prevention Program (DPP) sponsored by the National Institutes of Health has currently randomly assigned more than 3000 persons with impaired glucose tolerance and at high risk of developing diabetes into three treatment arms: metformin arm, an intensive lifestyle-modification arm, and a placebo arm. The study will conclude in 2002 after all participants have been followed for 3 to 6 years.
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PMID:Insulin therapy in type 2 diabetes. 1172 6

The glucagon-like peptides (GLP-1 and GLP-2) are proglucagon-derived peptides cosecreted from gut endocrine cells in response to nutrient ingestion. GLP-1 acts as an incretin to lower blood glucose via stimulation of insulin secretion from islet beta cells. GLP-1 also exerts actions independent of insulin secretion, including inhibition of gastric emptying and acid secretion, reduction in food ingestion and glucagon secretion, and stimulation of beta-cell proliferation. Administration of GLP-1 lowers blood glucose and reduces food intake in human subjects with type 2 diabetes. GLP-2 promotes nutrient absorption via expansion of the mucosal epithelium by stimulation of crypt cell proliferation and inhibition of apoptosis in the small intestine. GLP-2 also reduces epithelial permeability, and decreases meal-stimulated gastric acid secretion and gastrointestinal motility. Administration of GLP-2 in the setting of experimental intestinal injury is associated with reduced epithelial damage, decreased bacterial infection, and decreased mortality or gut injury in rodents with chemically induced enteritis, vascular-ischemia reperfusion injury, and dextran sulfate-induced colitis. GLP-2 also attenuates chemotherapy-induced mucositis via inhibition of drug-induced apoptosis in the small and large bowel. GLP-2 improves intestinal adaptation and nutrient absorption in rats after major small bowel resection, and in humans with short bowel syndrome. The actions of GLP-2 are mediated by a distinct GLP-2 receptor expressed on subsets of enteric nerves and enteroendocrine cells in the stomach and small and large intestine. The beneficial actions of GLP-1 and GLP-2 in preclinical and clinical studies of diabetes and intestinal disease, respectively, has fostered interest in the potential therapeutic use of these gut peptides. Nevertheless, the actions of the glucagon-like peptides are limited in duration by enzymatic inactivation via cleavage at the N-terminal penultimate alanine by dipeptidyl peptidase IV (DP IV). Hence, inhibitors of DP IV activity, or DP IV-resistant glucagon-like peptide analogues, may be alternative therapeutic approaches for treatment of human diseases.
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PMID:Biological actions and therapeutic potential of the glucagon-like peptides. 1183 66

Ageing is associated with an increased incidence of hypertension, macrovascular disease and type 2 diabetes (non-insulin-dependent diabetes). It has been suggested that a common mechanism may be responsible for all of these pathological states since all of these conditions often cluster in the same individual. Epidemiological and clinical data have consistently demonstrated an association between insulin resistance and/or hyperinsulinaemia and glucose intolerance, dyslipidaemia and elevated systolic blood pressures. Therefore, insulin resistance and hyperinsulinaemia have been proposed as the causal link among the elements of the clusters. The elderly are more glucose intolerant and insulin resistant, but it remains controversial whether this decrease in function is due to an inevitable consequence of 'biological ageing' or due to environmental or lifestyle variables, noticeably increased adiposity/altered fat distribution and physical inactivity. An increase of these modifiable factors has been shown to result in increases in insulin resistance and hyperinsulinaemia and vice versa. However, insulin secretion appears to decrease with age even after adjustments for differences in adiposity, fat distribution and physical activity. The glucose intolerance of ageing may be due, in part, to decreased insulin sensitivity of pancreatic / cells to insulinotropic gut hormones (GLP1/GIP) and in part to alterations of hepatic glucose production.
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PMID:Glucose tolerance, glucose utilization and insulin secretion in ageing. 1185 90


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