The pathophysiology of diabetes as a disease is characterised by an inability to maintain normal glucose homeostasis. In type 1 diabetes, this is due to autoimmune destruction of the pancreatic β-cells and subsequent lack of insulin production, and in type 2 diabetes it is due to a combination of both insulin resistance and an inability of the β-cells to compensate adequately with increased insulin release. Animal models, in particular genetically modified mice, are increasingly being used to elucidate the mechanisms underlying both type 1 and type 2 diabetes, and as such the ability to study glucose homeostasis in vivo has become an essential tool. Several techniques exist for measuring different aspects of glucose tolerance and each of these methods has distinct advantages and disadvantages. Thus the appropriate methodology may vary from study to study depending on the desired end-points, the animal model, and other practical considerations. This review outlines the most commonly used techniques for assessing glucose tolerance in rodents and details the factors that should be taken into account in their use. Representative scenarios illustrating some of the practical considerations of designing in vivo experiments for the measurement of glucose homeostasis are also discussed.
James E Bowe, Zara J Franklin, Astrid C Hauge-Evans, Aileen J King, Shanta J Persaud, and Peter M Jones
S C Cwyfan Hughes, M R Johnson, G Heinrich, and J M P Holly
A number of dramatic changes have been documented in the insulin-like growth factors (IGFs-I and -II) and their binding proteins (IGFBPs) during pregnancy. In this study we have tested the hypothesis that a failure of the normal proteolytic modification of IGFBP-3 is responsible for gestational diabetes by examining serum samples taken in the third trimester from 29 women with uncomplicated pregnancies, 21 women with established Type 1 diabetes and 20 women with gestational diabetes. Analysis of IGFBP-3 by Western immunoblotting revealed that it was present in a modified form, migrating at around 29 kDa, in the circulation of all of the women investigated. Semiquantification of the activity of the protease which modifies the IGFBP-3 demonstrated considerable variation between individuals in their ability to fragment radiolabelled IGFBP-3 following a 45-min co-incubation. Surprisingly, in one individual (with gestational diabetes) there was no detectable protease activity even though her endogenous IGFBP-3 had been modified. However, overall there was no clear-cut difference in protease activity between the different groups.
Radioimmunometric analysis of IGF-I revealed significantly higher levels in women with gestational diabetes than either of the other two groups (P<0·05). Similarly IGFBP-3 levels were also increased in these same women (P<0·05). In contrast, IGF-II levels did not alter between the three groups.
In conclusion, our hypothesis was not supported by these data and gestational diabetes was found not to be associated with any reduction in the activity of the circulating IGFBP-3 protease which could have decreased the availability of the IGF nor with any alteration in IGFs which could explain the onset of diabetes in these women.
Journal of Endocrinology (1995) 147, 517–524
M Holstad and S Sandler
In earlier studies it has been shown that prolactin (PRL) is a stimulating factor for the immune system, and it has been suggested that PRL might antagonize immunosuppressive effects of glucocorticoids. PRL has been reported to affect the cytokine secretion pattern, by elevating cytokine gene expression in macrophages, after the onset of sepsis. It also promotes the antibody response in mice where it increases the production of interferon-gamma (IFN-gamma) and inhibits interleukin-1 (IL-1) production. Due to these properties, PRL might influence the development of autoimmune type 1 diabetes. The aim of the present study was to examine the effects of two drugs; PRL and bromocriptine (BC) in vivo on the development of hyperglycemia and pancreatic insulitis in mice treated with multiple doses of streptozotocin (STZ) (40 mg/kg body weight, i.p.). The dopaminergic agonist BC is known to inhibit PRL secretion. In another set of experiments, the direct effects of PRL on the function of pancreatic islets exposed to STZ in vitro were studied. Mice treated with STZ became gradually hyperglycemic, and concomitant treatment with PRL (4 mg/kg body weight) for 21 days significantly reduced the elevation in blood glucose levels from day 10 onwards (P<0.05). Morphologic examinations of the pancreas on day 21 of mice receiving STZ injections revealed a marked insulitis, but only moderate insulitis in the STZ treated animals given PRL. BC administration (10 mg/kg body weight) in combination with STZ did not significantly affect the elevation in blood glucose levels or the insulitis. PRL or BC administration alone did not change the serum glucose concentration. This study indicates that PRL may affect hyperglycemia in the early phase of autoimmune diabetes. We suggest that it might be due to counteraction of autoimmune immunologic mechanisms and/or enhancement of beta-cell regeneration.
TY Tai, JY Lu, CL Chen, MY Lai, PJ Chen, JH Kao, CZ Lee, HS Lee, LM Chuang, and YM Jeng
This study aimed at elucidating the effects of interferon (IFN)-alpha on glucose metabolism in patients with chronic hepatitis B and C infections. Twenty-eight biopsy-proven patients with chronic hepatitis B (ten cases) and hepatitis C (18 cases) were given IFN-alpha for a total of 24 weeks. The patients received a 75 g oral glucose tolerance test (OGTT), glucagon stimulation test, tests for type 1 diabetes-related autoantibodies and an insulin suppression test before and after IFN-alpha therapy. Ten of the 28 patients responded to IFN-alpha therapy. Steady-state plasma glucose of the insulin suppression test decreased significantly in responders (13.32+/-1.48 (S.E.M.) vs 11.33+/-1.19 mmol/l, P=0.0501) but not in non-responders (12.29+/-1.24 vs 11.11+/-0.99 mmol/l, P=0.2110) immediately after completion of IFN-alpha treatment. In the oral glucose tolerance test, no significant difference was observed in plasma glucose in either responders (10.17+/-0.23 vs 10.03+/-0.22 mmol/l) or non-responders (10.11+/-0.22 vs 9.97+/-0.21 mmol/l) 3 Months after completion of IFN-alpha treatment. However, significant differences were noted in C-peptide in both responders (2.90+/-0.13 vs 2.20+/-0.09 nmol/l, P=0.0040) and non-responders (2.45+/-0.11 vs 2.22+/-0.08 nmol/l, P=0.0287) before vs after treatment. The changes of C-peptide in an OGTT between responders and non-responders were also significantly different (P=0.0028), with responders reporting a greater reduction in C-peptide. No case developed autoantibodies during the treatment. In patients who were successfully treated with IFN-alpha, insulin sensitivity improved and their plasma glucose stayed at the same level without secreting as much insulin from islet beta-cells.
CN Street, Lakey JR, K Seeberger, L Helms, RV Rajotte, AM Shapiro, and GS Korbutt
The discovery of a pancreatic adult stem cell would have significant implications for cell-based replacement therapies for type 1 diabetes mellitus. Nestin, a marker for neural precursor cells, has been suggested as a possible marker for islet progenitor cells. We have characterized the expression and localization of nestin in both the intact human pancreas and clinical human pancreatic islet grafts. Nestin was found to be expressed at different levels in the acinar component of human pancreatic biopsies depending on donor, as well as in ductal structures and islets to some degree. In islets, insulin-producing beta-cells rarely co-expressed the protein, and in the ducts a small percentage (1-2%) of cells co-expressed nestin and cytokeratin 19 (CK19) while most expressed only CK19 (90%) or nestin (5-10%) alone. Assessment of nestin expression in neonatal pancreatic sections revealed an increased number of islet-associated positive cells as compared with adult islets. Nestin immunoreactivity was also found in cells of the pancreatic vasculature and mesenchyme as evidenced by co-localization with smooth muscle actin and vimentin. Samples from post-islet isolation clinical islet grafts revealed a pronounced heterogeneity in the proportion of nestin-positive cells (<1-72%). Co-localization studies in these grafts showed that nestin is not co-expressed in endocrine cells and rarely (<5%) with cytokeratin-positive ductal cells. However, relatively high levels of co-expression were found with acinar cells and cells expressing the mesenchymal marker vimentin. In conclusion we have shown a diffuse and variable expression of nestin in human pancreas that may be due to a number of different processes, including post-mortem tissue remodeling and cellular differentiation. For this reason nestin may not be a suitable marker solely for the identification of endocrine precursor cells in the pancreas.
SJ Fisher, ZQ Shi, HL Lickley, S Efendic, M Vranic, and A Giacca
At supraphysiological levels, IGF-I bypasses some forms of insulin resistance and has been proposed as a therapeutic agent in the treatment of diabetes. Unfortunately, side effects of high-dose IGF-I (100-250 microg/kg) have precluded its clinical use. Low-dose IGF-I (40-80 microg/kg), however, shows minimal side effects but has not been systematically evaluated. In our previous study under conditions of declining glucose, low-dose IGF-I infusion was more effective in stimulating glucose utilization, but less effective in suppressing glucose production and lipolysis than low-dose insulin. However, under conditions of hyperglycemia, we could not observe any differential effects between high-dose infusions of IGF-I and insulin. To determine whether the differential effects of IGF-I and insulin are dose-related or related to the prevailing glucose level, 3 h glucose clamps were performed in the same animal model as in the previous studies, i.e. the moderately hyperglycemic (175 mg/dl) insulin-infused depancreatized dog, with additional infusions of low-dose IGF-I (67.8 microg/kg, i.e. 29.1 microg/kg bolus plus 0.215 microg/kg( )per min infusion; n=5) or insulin 49.5 mU/kg (9 mU/kg bolus plus 0.45 mU/kg per min; n=7). As in the previous study under conditions of declining glucose, low-dose IGF-I had significant metabolic effects in vivo, in our model of complete absence of endogenous insulin secretion. Glucose production was similarly suppressed with both IGF-I and insulin, by 54+/-3 and 56+/-2% s.e. (P=NS) respectively. Glucose utilization was stimulated to the same extent (IGF-I 5.2+/-0.2, insulin 5.5+/-0.3 mg/kg per min, P=NS). Glucagon, free fatty acid, glycerol, alanine and beta-hydroxybutyrate, were suppressed, while lactate and pyruvate levels were raised, similarly with IGF-I and insulin. We conclude that: (i) differential effects of IGF-I and insulin may be masked under hyperglycemic conditions, independent of the hormone dose; (ii) low-dose IGF-I has no selective advantage over additional insulin in suppressing glucose production and lipolysis, nor in stimulating glucose utilization during hyperglycemia and subbasal insulin infusion when insulin secretion is absent, as in type 1 diabetes mellitus.
R Riachy, B Vandewalle, S Belaich, J Kerr-Conte, V Gmyr, F Zerimech, M d'Herbomez, J Lefebvre, and F Pattou
We examined whether 1,25 dihydroxyvitamin D(3) (1,25 D(3)), the active form of vitamin D involved in the regulation of the immune system, may also protect human pancreatic islet cells from destruction induced by cytokines. In this study, we specifically investigated the effect of 1,25 D(3) on oxidative stress and major histocompatibility complex (MHC) induction, both implicated in cytokine-induced islet cell dysfunction and destruction. We also investigated the effects of 1,25 D(3) on interleukin (IL)-6, a pleiotropic cytokine implicated in the pathogenesis of immunoinflammatory disorders. Human pancreatic islets, isolated from heart-beating donors, were treated with a combination of three cytokines, IL-1beta+tumor necrosis factor alpha+interferon gamma, in the presence or absence of vitamin D, and compared with with untreated control cells. Metabolic activity was assessed by cell viability and insulin content. Oxidative stress was estimated by heat shock protein 70 (hsp70) expression, cell manganese superoxide dismutase (MnSOD) activity and nitrite release, a reflexion of nitric oxide (NO) synthesis. Variation of immunogenicity of islet preparations was determined by analysis of the MHC class I and class II transcripts. Inflammatory status was evaluated by IL-6 production. After 48 h of contact with cytokines, insulin content was significantly decreased by 40% but cell viability was not altered. MHC expression significantly increased six- to sevenfold as well as NO and IL-6 release (two- to threefold enhancement). MnSOD activity was not significantly induced and hsp70 expression was not affected by the combination of cytokines. The addition of 1,25 D(3) significantly reduced nitrite release, IL-6 production and MHC class I expression which then became not significantly different from controls. These results suggest that the effect of 1,25 D(3) in human pancreatic islets cells may be a reduction of the vulnerability of cells to cytotoxic T lymphocytes and a reduction of cytotoxic challenge. Hence, 1,25 D(3) might play a role in the prevention of type 1 diabetes and islet allograft rejection.
G Papaccio, E Ammendola, and FA Pisanti
Pancreases of untreated and nicotinamide (NIC)-treated pre-diabetic (10-week-old) and overtly diabetic (25-week-old) female NOD (non-obese diabetic) mice and of NON (non-obese non-diabetic) control mice were studied, with the following results. (1) Islets and ducts of overtly diabetic untreated NOD mice (25-week-old) were found to express low levels of MHC class I and II molecules, like NON controls, and high levels of adhesive molecules. (2) NIC was able to slightly affect glycaemia and insulitis, slowing down diabetes progression. Moreover it significantly decreased MHC class II expression (but not class I) in vivo by week 10, and significantly enhanced intercellular adhesion molecule-1 (ICAM-1) expression, mainly by week 25, within the pancreas, where 5-bromo-2'-deoxyuridine positive nuclei and insulin positive cells were present, demonstrating that a stimulation of endocrine cell proliferation occurs. (3) In addition, NIC partly counteracted the fall of superoxide dismutase levels, observed in untreated diabetic NOD animals. (4) In vitro studies demonstrated that NIC: (i) was able to significantly reduce nitrite accumulation and to increase NAD+NADH content significantly, and (ii) was able to increase the levels of interleukin-4, a T helper 2 lymphocyte (Th2) protective cytokine, and of interferon-alpha (IFN-alpha), which is known to be able to induce MHC class I and ICAM-1 but not MHC class II expression, as well as IFN-gamma, which is also known to be able to induce MHC class I and ICAM-1 expression. The latter, although known to be a proinflammatory Th1 cytokine, has also recently been found to exert an anti-diabetogenic role. This study therefore clearly shows that adhesive mechanisms are ongoing during the later periods of diabetes in pancreatic ducts of NOD mice, and suggests they may be involved in a persistence of the immune mechanisms of recognition, adhesion and cytolysis and/or endocrine regeneration or differentiation processes, as both NIC-increased ICAM-1 expression and 5-bromo-2'-deoxyuridine positivity imply. The effects of NIC on MHC class II (i.e. a reduction) but not class I, and, mainly, on ICAM-1 expression (i.e. an increase), together with the increase in Th2 protective cytokine levels are very interesting, and could help to explain its mechanism of action and the reasons for alternate success or failure in protecting against type 1 diabetes development.
Frank H Bloomfield
-communicable diseases. Population studies in Northern Ireland ( Cardwell et al . 2005 ), England ( Goldacre 2017 ), Western Australia ( Haynes et al . 2007 ) and Sweden ( Crump et al . 2011 ) have reported a 17–43% increased risk of type 1 diabetes following
James M Evans, Laura S Morris, and Julian R Marchesi
generating compounds that interact with our own endocrine system. Diabetes and gut bacteria Diabetes is a chronic metabolic disorder that affects an estimated 347 million people throughout the world ( WHO 2012 ). Type 1 diabetes, also known as juvenile