Supervised physical activity in Sweden: in theory and practice

The aim of this study was to assess to which extent community-run projects including physical activity could be identified, described and analysed in terms of objectives, organisation, evaluation and financing, as a resource in prevention and treatment of common lifestyle-related medical problems. The Swedish database Spriline was used as a main source of information. Identification of ongoing Swedish activities was followed by a mail questionnaire. In total, 151 projects were eventually identified. A semistructured questionnaire containing about 30 questions was mailed to the individual listed as responsible for the project, with a reminder 2 months later. Only 52 projects were viable; a follow-up of nonresponders showed that no relevant activity program had ever existed or that the person responsible had left. Walking, aerobics and water activities were the dominating types of activity. Most projects addressed both sexes, but eight weight reduction programs were designed for women only. Evaluation ranged from 'measuring attendance' to 'scientific evaluation'. Physical activity programs may not be as systematically organised as the Swedish database suggests and cannot generally be relied upon as support in patient care, unless critically evaluated in advance.

Deficiency of phosphofructo-1-kinase/muscle subtype in humans is associated with impairment of insulin secretory oscillations

In healthy humans, insulin is secreted in an oscillatory manner. While the underlying mechanisms generating these oscillations are not fully established, increasing evidence suggests a central role for phosphofructo-1-kinase/muscle subtype (PFK1-M), which also serves as the predominantly active PFK1 subtype in the pancreatic beta-cell. The fact that normal oscillatory secretion is impaired in subjects with impaired glucose tolerance and healthy relatives of patients with type 2 diabetes suggests that this defect may be involved in the secretory dysfunction. To evaluate a possible link between inherited PFK1-M deficiency in humans (Tarui's disease or glycogenosis type VII) and altered insulin oscillations, in vivo studies were performed. We determined basal insulin oscillations during 2 h of frequent plasma sampling in two related teen-aged individuals with homozygous and heterozygous PFK1-M deficiency compared with nondeficient, unrelated control subjects. As predicted by the underlying hypothesis, normal oscillations in insulin secretion were completely abolished in the individual with homozygous deficiency of PFK1-M and significantly impaired in the heterozygous individual, as shown by spectral density and autocorrelation analyses. Thus, deficiency of PFK1-M subtype in humans appears to be associated with an impaired oscillatory insulin secretion pattern and may contribute to the commonly observed secretion defects occurring in type 2 diabetes.

Low birth weight, family history of diabetes, and glucose intolerance in Swedish middle-aged men

OBJECTIVE

To investigate the association between low birth weight and glucose intolerance in relation to family history of diabetes.

RESEARCH DESIGN AND METHODS

We conducted a population-based cross-sectional study of 2,237 men born in 1938-1957 in four municipalities in the outskirts of Stockholm, 50% of whom had a family history of diabetes (at least one first-degree or two second-degree relatives with diabetes). Oral glucose tolerance testing detected 35 cases of type 2 diabetes, 102 cases of impaired glucose tolerance, and 57 cases of impaired fasting glucose.

RESULTS

In subjects without a family history of diabetes, low (< or = 3,000 g) birth weight was associated with an odds ratio of 2.3 (95% confidence intervals = 0.4-14.4) for diabetes, 1.8 (0.7-4.3) for impaired glucose tolerance, and 3.3 (1.0-10.4) for impaired fasting glucose. In subjects with a family history of diabetes, the corresponding figures were approximately similar, except for diabetes, for which the odds ratio was 5.4 (2.0-14.9). For men with low birth weight in combination with a family history of diabetes, the odds ratio was 10.9 (2.9-41.2) for diabetes, 2.4 (1.1-5.6) for impaired glucose tolerance, and 5.9 (2.1-16.3) for impaired fasting glucose.

CONCLUSIONS

This study indicated that low birth weight is associated with type 2 diabetes, impaired glucose tolerance, and impaired fasting glucose in men. This finding was most pronounced in subjects with diabetes in the family, but it was also indicated in those without a family history of diabetes. Men with the combination of low birth weight and family history of diabetes seem to be at particularly high risk of developing type 2 diabetes.

Dysfunction of the islet lysosomal system conveys impairment of glucose-induced insulin release in the diabetic GK rat

Accumulated evidence links an important signal involved in glucose-stimulated insulin release to the activation of the islet lysosomal glycogenolytic enzyme acid glucan-1,4-alpha-glucosidase. We have analyzed the function of the lysosomal system/lysosomal enzyme activities in pancreatic islets of young (6-8 weeks), spontaneously diabetic, GK (Goto-Kakizaki) rats and Wistar control rats in relation to glucose-induced insulin release. The insulin secretory response to glucose was markedly impaired in the GK rat, but was restored by the adenylate cyclase activator forskolin. Islet activities of classical lysosomal enzymes, e.g.. acid phosphatase, N-acetyl-beta-D-glucosaminidase, beta-glucuronidase, and cathepsin D, were reduced by 20-35% in the GK rat compared with those in Wistar controls. In contrast, the activities of the lysosomal alpha-glucosidehydrolases, i.e.. acid glucan-1,4-alpha-glucosidase and acid alpha-glucosidase, were increased by 40-50%. Neutral alpha-glucosidase (endoplasmic reticulum) was unaffected. Comparative analysis of liver tissue showed that lysosomal enzyme activities were of the same magnitude in GK and Wistar rats. Notably, in Wistar rats, the activities of acid glucan-1,4-alpha-glucosidase and acid alpha-glucosidase were approximately 15-fold higher in islets than in liver. Other lysosomal enzymes did not display such a difference. Normalization of glycemia in GK rats by phlorizin administered for 9 days did not influence either the lysosomal alpha-glucosidehydrolase activities or other lysosomal enzyme activities in GK islets. Finally, the pseudotetrasaccharide acarbose, which accumulates in the lysosomal system, inhibited acid glucan-1,4-alpha-glucosidase activity in parallel with its inhibitory action on glucose-induced insulin release in intact Wistar islets, whereas no effect was recorded for either parameter in intact GK islets. In contrast, acarbose inhibited the enzyme activity equally in islet homogenates from both GK and Wistar rats, showing that the catalytic activity of the enzyme itself in disrupted cells was unaffected. We propose that dysfunction of the islet lysosomal/vacuolar system is an important defect impairing the transduction mechanisms for glucose-induced insulin release in the GK rat.

Effects of vasopressin-mastoparan chimeric peptides on insulin release and G-protein activity

Two chimeric peptides, consisting of the linear vasopressin receptor V1 antagonist PhAc-D-Tyr(Me)-Phe-Gln-Asn-Arg-Pro-Arg-Tyr, in the N-terminus and mastoparan in the C-terminus connected directly (M375) or via 6-aminohexanoic acid (M391), have been synthesised. At 10 microM concentration, these novel peptides increased insulin secretion from isolated rat pancreatic islet cells 18-26-fold at 3.3 mM glucose and 3.5-5-fold at 16.7 mM glucose. PTX pretreatment of the islets decreased the peptide-induced insulin release. M375 and M391 bind to V1a vasopressin receptors with affinities lower than the unmodified vasopressin antagonist, but with K(D) values of 3.76 nM and 9.02 nM, respectively, both chimeras are high affinity ligands. The GTPase activity and GTPgammaS binding in the presence of these peptides has been characterised in Rin m5F cells. Comparison of the influence of the peptides M375 and M391 on GTPase activity in native and pertussis toxin-treated cells suggests a selective activation of G alpha(i)/G alpha(o) subunits, combined with a suppression of other GTPases, primarily G alpha(s). However, the GTPgammaS binding data show that the peptides retain some of the activating property even in PTX-treated cell membranes. In conclusion, the conjugation of mastoparan with the V1a receptor antagonists produce peptides with properties different from the parent peptides that could be used to elucidate the role of different G proteins in insulin release.

Different modes of action of the imidazoline compound RX871024 in pancreatic beta-cells. Blocking of K+ channels, mobilization of Ca2+ from endoplasmic reticulum, and interaction with exocytotic machinery

The imidazoline compound RX871024 glucose-dependently potentiates the release of insulin in pancreatic islets and beta-cell lines. This activity of the compound is not related to its action by stimulating alpha 2-adrenoceptors and I1- and I2-imidazoline receptors. There are at least three modes of action of RX871024 in beta-cells: (1) RX871024 blocks the ATP-dependent, Ca(2+)-activated, and delayed rectifier K+ channel activity; (2) RX871024 causes mobilization of Ca2+ from thapsigargin-sensitive intracellular stores, the effect probably controlled by cytochrome P450; and (3) the stimulatory activity of RX871024 on insulin release involves interaction of the compound with the exocytotic machinery, unrelated to the changes in membrane potential and cytoplasmic-free Ca2+ concentration, whereas protein phosphorylation plays an important role in this process. The maximal insulinotropic effect of RX871024 is much higher than that of the sulfonylurea glibenclamide. RX871024 stimulates insulin release and normalizes blood glucose levels in rats in vivo without affecting blood pressure and heart rate.

[Gastrointestinal peptides among new therapeutic agents used in type 2 diabetes]

The pharmacological arsenal available today for the treatment of type II diabetes is often insufficient to allow optimal control of the disease. Each agent corrects only one or a few of the multiple defects that characterise type II diabetes. Currently, new drugs are under development that target several of the clinical abnormalities. These agents include the gastrointestinal peptides, glucagon-like polypeptide-1 (GLP-1) and amylin, and their analogues. New rapid- and long-acting insulin analogues will also constitute interesting treatment alternatives.

An endogenous peptide isolated from the gut, NK-lysin, stimulates insulin secretion without changes in cytosolic free Ca2+ concentration

We have recently isolated and cloned a novel endogenous peptide from pig intestine, NK-lysin (NKL). In the present study we show that NKL (1-100 nM) potently and reversibly stimulates insulin secretion in rat pancreatic islets and in the beta-cell line HIT T15. This effect of NKL was not accompanied by changes in cytoplasmic free calcium concentration. The stimulatory activity of NKL on insulin release was also observed in permeabilized islets under Ca2+-clamped conditions. Preincubation of HIT T15 cells with NKL for 1 h or 24 h did not influence cell viability. Possible mechanisms of insulinotropic activity of NKL are discussed.

Preserved initiatory and potentiatory effect of alpha-ketoisocaproate on insulin release in islets of glucose intolerant rats

Insulin responses to glucose and non-glucose secretagogues were studied in short-term cultured pancreatic islets and perfused pancreata of the glucose intolerant F1 hybrid rats of spontaneously diabetic Goto-Kakizaki and control Wistar rats. After culture at 5.5 mmol/l glucose, hybrid islet responses to 11.1, 16.7 and 27.0 mmol/l glucose were between 60 and 40% of control islet responses. A combination of 1 mmol/l isobutylmethylxanthine and 16.7 mmol/l glucose induced a pronounced insulin release, which was of similar magnitude in hybrid and control rat islets. This response was not further augmented by addition of glibenclamide and arginine. The slope of potentiation of arginine (10 mmol/l)-stimulated insulin secretion by glucose (5.5-16.7 mmol/l) was greatly impaired in hybrid islets. In contrast to glucose, alpha-ketoisocaproate (KIC), which is metabolized in Krebs cycle, dose-dependently stimulated insulin secretion to similar levels in hybrid and control islets, cultured at 5.5 mmol/l glucose. Also in hybrid islets depolarized by potassium chloride (30 mmol/l) and with adenosine triphosphate-sensitive K+-channels kept open by diazoxide, insulin responses to glucose were greatly impaired but intact to KIC. Furthermore, KIC potentiated normally the insulin response to arginine in hybrid islets. In the isolated perfused pancreas, KIC induced similar insulin responses in hybrid rats and control rats. The potentiating effect by 5.5 mmol/l glucose on the KIC-stimulated insulin responses was, however, greatly reduced in isolated islets and absent in the perfused pancreata of hybrid rats. Taken together, these findings suggest an intact capacity for insulin release, although the initiating and potentiating effect by glucose on insulin release are defective in the Goto-Kakizaki-hybrid rats. An abnormal beta-cell glucose metabolism proximal to the Krebs cycle is likely to account for the impairment of insulin release.

Weight history, glucose intolerance, and insulin levels in middle-aged Swedish men

The association between weight history and glucose intolerance was examined in a cross-sectional study consisting of 3,128 Swedish men aged 35-56 years, 52 percent of whom had a family background of diabetes mellitus. Oral glucose tolerance testing detected 55 cases of type 2 (non-insulin-dependent) diabetes and 172 cases of impaired glucose tolerance. Among men with no family history of diabetes, the estimated odds ratios for impaired glucose tolerance associated with short (<5 years) and long (> or =10 years) durations of obesity (body mass index (weight (kg)/height2 (m2) > or =25.0) were 1.3 (95% confidence interval (CI) 0.2-7.7) and 11.8 (95% CI 3.3-41.9), respectively. Among men with a family history of diabetes, the odds ratios were 2.0 (95% CI 0.8-4.7) and 4.0 (95% CI 1.8-9.1), respectively. Corresponding estimates of the odds of type 2 diabetes, adjusted for family history of diabetes, were 1.9 (95% CI 0.5-7.1) and 7.3 (95% CI 2.2-23.7), respectively. The odds of high (> or =30.0 mU/liter) fasting insulin levels in subjects with impaired glucose tolerance were 6.9 (95% CI 0.6-74.2) and 21.0 (95% CI 2.1-206.4) for short and long durations of obesity, respectively. Corresponding estimated odds of low 2-hour insulin response (< or =71.9 mU/liter) were 0.7 (95% CI 0.2-2.9) and 3.3 (95% CI 1.2-8.9). Homeostasis model assessment of insulin resistance yielded an odds ratio of 6.7 (95% CI 0.6-73.4) for a short duration of obesity and 20.0 (95% CI 2.0-200.6) for a long duration. Examination of beta-cell function with homeostasis model assessment resulted in odds ratios of 0.2 (95% CI 0.0-1.6) and 2.0 (95% CI 0.7-5.4) for short and long durations of obesity, respectively. These data indicate that obesity decreases glucose tolerance by way of progressively increased insulin resistance and, in the case of prolonged duration, by decreased insulin secretion as well.

Increased glucocorticoid sensitivity in islet beta-cells: effects on glucose 6-phosphatase, glucose cycling and insulin release

Glucose-6-phosphatase (G6Pase) activity and the rate of glucose cycling are increased in islets from animal models of Type II (non-insulin-dependent) diabetes mellitus. Glucocorticoid treatment further stimulates these processes and inhibits glucose-induced insulin release. To determine whether these effects result from a direct action of glucocorticoids on the beta-cells, we used isolated islets. The islets were from transgenic mice overexpressing the glucocorticoid receptor in their beta-cells to increase the cells' sensitivity to glucocorticoid. Islets from transgenic and non-transgenic control mice utilized and oxidized the same amount of glucose. In contrast, islet G6Pase activity was 70 % higher, glucose cycling was increased threefold and insulin release was 30 % lower in islets from transgenic mice. Hepatic G6Pase activity was the same in transgenic and control mice. Dexamethasone administration increased G6Pase activity and glucose cycling and decreased insulin release in both transgenic and control mouse islets. We conclude that glucocorticoids stimulate islet G6Pase activity and glucose cycling by acting directly on the beta-cell. That activity may be linked to the inhibition of insulin release.

Glucose metabolism in Goto-Kakizaki rat islets

Islets from Goto-Kakizaki (GK) rats from our colony, despite marked impairment of glucose-induced insulin release, used glucose and produced CO2 at a rate 3 times that of islets from control Wistar rats. Almost all glucose used was accounted for in CO2 and lactate production. The percentages of glucose carbon used collected in CO2 and lactate were similar for control and GK islets. GK islets also oxidized 40% more acetate and leucine to CO2 than did control islets. The fraction of carbon leaving the Krebs cycle relative to CO2 production was the same in GK and control islets. The capacities of mitochondria from GK islets to generate ATP from glutamate and malate were similar and that to generate ATP from succinate and rotenone was somewhat less from GK islets. The reason for the enhanced utilization of substrates by islets of the GK rat is not apparent. In conclusion, there is no decrease in islet glucose utilization, glucose oxidation, Krebs cycle function, or the electron transport system evident from these measurements to explain the impaired insulin release in islets from GK rats.

Signaling and sites of interaction for RX-871024 and sulfonylurea in the stimulation of insulin release

The objective of this study was to compare effects of RX-871024, a compound with imidazoline structure, and the sulfonylurea glibenclamide, representatives of two groups of ATP-dependent potassium channel (KATP) blockers, on insulin secretion and cytoplasmic free calcium concentration ([Ca2+]i). Furthermore, we studied the interaction of the compounds on these two parameters. The experiments were performed in the perfused rat pancreas, isolated rat pancreatic islets, and dispersed beta-cells. At maximal effective concentrations of the compounds, RX-871024 had a more pronounced insulinotropic effect than glibenclamide, but the increase in [Ca2+]i was similar. Glibenclamide enhanced the insulinotropic effect of suboptimal concentrations of RX-871024 at 3.3 and 16.7 mM glucose. Notably, glibenclamide and RX-871024 also stimulated insulin secretion under Ca(2+)-clamped conditions, i.e., during plasma membrane depolarization with KCl and glucose or in permeabilized islets. The magnitudes of insulin stimulation under the latter types of conditions were similar for both compounds. It is concluded that RX-871024 and the sulfonylurea glibenclamide promote insulin secretion by two mechanisms, namely closure of KATP channels and a direct stimulation of exocytosis. At a similar increase in [Ca2+]i, the maximal stimulatory effect of RX-871024 on insulin secretion was stronger than that of glibenclamide, implying that RX-871024 also affects insulin secretion by a signal transduction pathway that is not activated by glibenclamide.

The glutathione levels are reduced in Goto-Kakizaki rat retina, but are not influenced by aminoguanidine treatment

PURPOSE

To examine the levels of the free radical protecting enzyme glutathione and the endothelial/pericyte ratio in retinal capillaries in the Goto-Kakizaki (GK) Wistar rat, with and without aminoguanidine treatment.

METHODS

Eight-month-old GK rats, with non-obese, spontaneous non-insulin-dependent diabetes mellitus (NIDDM), were examined after a six month period of aminoguanidine treatment. Glutathione levels were measured with high performance liquid chromatography and the endothelial/pericyte ratio was calculated in trypsin digested vessel preparations.

RESULTS

The levels of glutathione in GK rat retina were significantly lower compared to controls (p = 0.0108). There was no difference in the endothelial/pericyte ratio compared to matched control rats (1.8 +/- 0.2 vs. 1.8 +/- 0.1, respectively). Aminoguanidine treatment did not influence either the degree of hyperglycemia, the levels of glutathione or the endothelial/pericyte ratio in GK or control rat retina.

CONCLUSIONS

The results indicate that impaired glucose metabolism may influence one of the defense mechanisms for oxidative stress, but also suggest that decreased glutathione levels occur prior to morphological signs of pericyte loss and/or endothelial cell proliferation in this animal model of hereditary NIDDM.

Food frequency questionnaire versus 7-day weighed dietary record information on dietary fibre and fat intake in middle-aged Swedish men

To study the magnitude of agreement between a short self-administered food frequency questionnaire and a 7-day weighed dietary record regarding the consumption of fibre and fat, we collected information from 92 randomly selected middle-aged Swedish men. The participants first recorded all foods and drinks consumed over seven consecutive days by means of a digital scale. One month after the 7-day weighed record had been completed, a self-administered food frequency questionnaire on habitual consumption of foods containing fibre or fat during the preceding month was sent to the subjects. The 20 largest contributors of fibre and fat in the diet accounted for 71% and 52% of the total intake, respectively, based on the 7-day weighed record. The estimated mean consumption of fibre was 19.0 grams per day based on the 7-day weighed record and 18.3 grams per day based on the food frequency questionnaire. Corresponding estimated mean consumption of fat was 88.6 grams per day versus 46.9 grams per day. Men with high physical activity and low BMI, respectively, had higher intake of fibre and fat. These differences were seen for both dietary measurement methods but were more marked using the 7-day weighed record. The agreement between methods for each individual was also assessed. Based on five categories of fibre consumption, 61% of the respondents in the highest quintile according to the 7-day weighed record were classified in one of the two highest quintiles according to the food frequency questionnaire. The corresponding figure for fat intake was 56%. We conclude that the short self-administered food frequency questionnaire used in the present study can assess the absolute intake of fibre, but not of fat, with good precision. Also, the ranking of individuals in broad categories of consumption of fibre and fat was not largely misclassified based on this short questionnaire.

Identification, isolation, and characterization of daintain (allograft inflammatory factor 1), a macrophage polypeptide with effects on insulin secretion and abundantly present in the pancreas of prediabetic BB rats

A bioactive macrophage factor, the polypeptide daintain/allograft inflammatory factor 1 (AIF1), has been isolated from porcine intestine. It was discovered when searching for intestinal peptides with effects on insulin release, and its purification was monitored by the influence of the peptide fractions on pancreatic glucose-induced insulin secretion. Daintain/AIF1 is a 146-aa residue polypeptide with a mass of 16,603 Da and an acetylated N terminus. An internal 44-residue segment with the sequence pattern -KR-KK-GKR- has a motif typical of peptide hormone precursors, i.e., dibasic sites for potential activation cleavages and at the sequentially last such site, the structure GKR. The latter is a signal for C-terminal amide formation in the processing of peptide hormones. Daintain/AIF1 is immunohistochemically localized to microglial cells in the central nervous system and to dendritic cells and macrophages in several organs. A particularly dense accumulation of daintain/AIF1-immunoreactive macrophages was observed in the insulitis affecting the pancreatic islets of prediabetic BB rats. When injected intravenously in mice, daintain/AIF1 at 75 pmol/kg inhibited glucose (1 g/kg)-stimulated insulin secretion, with a concomitant impairment of the glucose elimination, whereas at higher doses (7.5 and 75 nmol/kg), daintain/AIF1 potentiated glucose-stimulated insulin secretion and enhanced the glucose elimination. Its dual influence on insulin secretion in vivo at different peptide concentrations, and the abundance of macrophages expressing daintain/AIF1 in the pancreatic islets of prediabetic rats, suggest that daintain/AIF1 may have a role in connection with the pathogenesis of insulin-dependent diabetes mellitus.

Decreased cortical bone thickness in spontaneously non-insulin-dependent diabetic GK rats

We studied the occurrence of osteopenia, as reflected by decreased cortical bone thickness, in a nonobese animal model of hereditary non-insulin-dependent diabetes with long duration, i.e., 8-month-old Goto-Kakizaki (GK) rats. In addition, motor nerve-conduction velocity was measured in the GK rats. Age- and weight-matched Wistar rats served as controls. The GK rats displayed marked glucose intolerance, as compared to control rats, in an intraperitoneal glucose tolerance test. Decreased cortical bone thickness by approximately 15%, was evident in X-ray analysis of metatarsal bones (p < 0.001) and humerus (p < 0.05) of the GK rats. Motor nerve-conduction velocity, measured in the sciatic nerve, was also decreased (by 10%) in the GK as compared with the age-matched control rats (p < 0.05). In conclusion, reduction of cortical bone thickness is present in 8-month-old GK rats, which simultaneously demonstrate signs of peripheral neuropathy. Thus, the GK rat appears to be a model of NIDDM suitable for studies of diabetic bone disease in the absence of obesity.

Characterization of dopuin, a polypeptide with special residue distributions

A 62-residue polypeptide, dopuin, has been isolated from pig small intestine. It is distinguished by an N-terminal part with a high content of proline (7 in a 26-residue segment), a C-terminal part with a high proportion of histidine (3 in a 9-residue segment), and six half-cystine residues in three intrachain disulphide bridges (connecting positions 22-25, 23-54 and 35-44). The Cys and Pro distributions suggest a tight and special conformation. In contrast to PEC-60 and somatostatin, it has no established inhibitory effect on insulin secretion. At 10 nM concentration, a weak inhibitory tendency is less than half of that of the other two peptides. Like gastrointestinal trefoil peptides, dopuin has three disulphide bridges, Ala-Pro segments, and many charged residues, but they are differently distributed and dopuin belongs to a separate, apparently novel family. However, dopuin is similar to a peptide corresponding to an expressed-sequence-tag cDNA of human fetal liver and spleen, establishing the nature of the mature form of the product of this cDNA, and showing a general tissue, age, and species distribution of this peptide. A truncated form of vimentin, composed of its C-terminal 37 residues, vimentin-C37, was also purified and structurally characterized. These two peptides increase the complexity of known intestinal polypeptides and at least dopuin has properties compatible with specific biofunctions.

Pancreatic beta cells are important targets for the diabetogenic effects of glucocorticoids

Abnormalities contributing to the pathogenesis of non-insulin-dependent diabetes mellitus include impaired beta cell function, peripheral insulin resistance, and increased hepatic glucose production. Glucocorticoids are diabetogenic hormones because they decrease glucose uptake and increase hepatic glucose production. In addition, they may directly inhibit insulin release. To evaluate that possible role of glucocorticoids in beta cell function independent of their other effects, transgenic mice with an increased glucocorticoid sensitivity restricted to their beta cells were generated by overexpressing the glucocorticoid receptor (GR) under the control of the insulin promoter. Intravenous glucose tolerance tests showed that the GR transgenic mice had normal fasting and postabsorptive blood glucose levels but exhibited a reduced glucose tolerance compared with their control littermates. Measurement of plasma insulin levels 5 min after intravenous glucose load demonstrated a dramatic decrease in acute insulin response in the GR transgenic mice. These results show that glucocorticoids directly inhibit insulin release in vivo and identify the pancreatic beta cell as an important target for the diabetogenic action of glucocorticoids.

Delayed Ca2+ response to glucose in diabetic GK rat

The spontaneously diabetic non-obese GK (Goto-Kakizaki) rat exhibits high basal plasma glucose and insulin levels and poor glucose-induced insulin secretion, which makes it a suitable model for non-insulin dependent diabetes mellitus, NIDDM. The aim of this study was to investigate the handling of cytosolic free Ca2+ concentration ([Ca2+]i), the key regulator of insulin secretion, in GK rat single pancreatic islets. For this purpose the influence of high glucose (16.7 mM) and arginine (20 mM) on [Ca2+]i was studied in GK and Wistar rat islets, which served as controls. The data obtained suggest that glucose which through its metabolism generates ATP needed for closure of the KATP channels and membrane depolarization, induces a delayed [Ca2+]i response in the GK rat pancreatic islet. This delay in [Ca2+]i response is likely to result from a defective metabolism of glucose in the diabetic islet.

Galparan: a powerful insulin-releasing chimeric peptide acting at a novel site

Galparan is a 27-amino acid long chimeric peptide, GWTLNSAGYLLGP-INLKALAALAKKIL amide, consisting of galanin-(1-13) linked to mastoparan amide via a peptide bond to provide the mastoparan and galanin effector parts of the molecules. Galparan (10 microM) powerfully stimulates insulin secretion from isolated rat pancreatic islets in a reversible and dose-dependent manner; the stimulation is 26-fold at 3.3 mM glucose and 6-fold at 16.7 mM glucose. Galparan also enhances insulin secretion to a similar extent from islets of diabetic GK rats. The stimulatory effect of galparan on insulin release is not directly dependent on extracellular Ca2+, nor can it be explained only by changes in free cytosolic Ca2+ concentrations. Furthermore, galparan is effective in evoking insulin release in B cells depolarized by 25 mM KCl when ATP-sensitive K+ channels are kept open by diazoxide. Thus, galparan, like mastoparan, stimulates exocytosis of insulin at a distal site in the stimulus-secretion coupling of the B cell. This distal site is not identical to that used by mastoparan, as pertussis toxin pretreatment does not influence the insulinogenic effect of galparan. In conclusion, galparan evokes a large and reversible insulin secretion, acting at a yet unknown distal site and also promoting exocytosis in depolarized B cells from normal rats as well as diabetic GK rats.

Islet capillary blood pressure increase mediated by hyperglycemia in NIDDM GK rats

This study was performed to measure pancreatic islet capillary pressure under basal conditions and after an acute glucose stimulation of insulin release in normal rats. In addition, the islet capillary pressure was estimated in GK rats, an animal model of NIDDM. Hydrostatic pressure in single pancreatic islet capillaries was determined in vivo by direct measurement using the micropuncture technique. The pancreatic islets were visualized by injection of neutral red. This intravital staining had no effect on islet function, whole pancreatic and islet blood flow, and capillary blood pressure in the exocrine pancreas. Islet capillary blood pressure in normoglycemic Wistar F rats was estimated at 3.1 +/- 0.3 mmHg (n = 15). Administration of D-glucose (1 g/kg) doubled this value, whereas no effect was seen after injection of an equimolar dose of the non-metabolizable glucose-derivative 3-O-methyl glucose. In GK rats, basal islet capillary blood pressure was increased (5.7 +/- 0.4 mmHg; n = 10; P < 0.001) when compared with the control Wistar F rats. Reduction of blood glucose levels in GK rats with phlorizin treatment showed this increased basal islet capillary pressure in GK rats to be glucose dependent and reversible. In the present study, we have for the first time shown that both acute and chronic hyperglycemia augment islet capillary pressure. The effects of a chronically increased islet capillary pressure on long-term islet function remain to be determined.

Altered endothelial/pericyte ratio in Goto-Kakizaki rat retina

The Goto-Kakizaki (GK) rat represents a model of hereditary non-insulin-dependent diabetes mellitus (NIDDM), characterized by nonobesity, mild hyperglycemia from early life, impaired glucose tolerance test results, and a markedly defective insulin response to glucose. The rats develop signs of both nephropathy and neuropathy, but, to our knowledge, retinal changes have not been reported so far in this model of NIDDM. Hence, the aim of the present study was to assess whether morphological vascular changes could be demonstrated in retinal vessel preparations of GK rats. The endothelial/pericyte ratio was found to be higher in GK rats aged 8 months as well as after 24-30 months compared to their matched controls (2.3 +/- 0.2 versus 2.0 +/- 0.1; p < 0.01, and 2.6 +/- 0.2 versus 1.9 +/- 0.1; p < 0.001, respectively). Furthermore, in 24 to 30-months-old GK rats, the endothelial/pericyte ratio was higher than in 8 month old GK rats (p < 0.05). Thus, the GK rat appears to be a suitable model for experimental studies of chronic complications, including diabetic retinopathy, in NIDDM.

Full-length and N-terminally truncated chicken intestinal diazepam-binding inhibitor. Purification, structural characterization and influence on insulin release

Two forms of diazepam-binding inhibitor (DBI) have been purified from chicken intestine and identified as the intact avian polypeptide (residues 1-86) and a truncated variant (residues 35-86). At 10 nM concentration, both the intact and the truncated peptide suppress in vitro-monitored glucose-induced insulin release by 50 (p < 0.02) and 64% (p < 0.01) respectively. The truncation starts at a segment. -Thr-Val-Gly-Asp-, that is strictly conserved between characterized DBI species, indicating special restrictions on the structure. However, overall DBI conservation appears to be complex. A number of differently bioactive fragments with separate processings and tissue distributions have been observed, suggesting multiple functions of DBI and its sub-segments.

Gastric inhibitory polypeptide and splanchnic blood perfusion: augmentation of the islet blood flow increase in hyperglycemic rats

The aim of the study was to investigate how the incretin candidate hormone gastric inhibitory polypeptide (GIP) affects splanchnic blood flow, especially pancreatic islet blood flow. For this purpose, male Sprague-Dawley rats were injected intravenously with either saline or GIP (5 or 15 micrograms/kg body weight) 10 min before blood flow measurements by a microsphere technique. Furthermore, 3 min before the blood flow measurements, 1 ml of either saline or 30% D-glucose was given intravenously. All glucose-injected animals were markedly hyperglycemic (> 20 mmol/liter) at the time of the blood flow measurements. Both doses of GIP potentiated basal and glucose-stimulated insulin release. In the normoglycemic rats, the lowest dose of GIP did not affect the blood perfusion to any of the investigated organs. The highest dose of GIP decreased whole pancreatic and duodenal blood flow, whereas islet blood flow was unaffected. As a result, fractional islet blood flow was increased. In the hyperglycemic rats, where the islet blood flow was increased compared with control animals, both doses of GIP further enhanced islet blood flow. No effect on pancreatic, fractional islet, or duodenal blood flow was seen after GIP administration to hyperglycemic animals. It is concluded that administration of GIP can further augment the glucose-induced stimulation of islet blood flow. This may contribute to facilitating release of insulin from the islets.

Imidazoline compounds stimulate insulin release by inhibition of K(ATP) channels and interaction with the exocytotic machinery

A novel imidazoline compound, RX871024, was used to investigate the mechanisms by which imidazoline derivatives promote insulin secretion in rat pancreatic beta-cells and HIT T15 cells. RX871024 stimulated insulin release from rat pancreatic beta-cells and HIT T15 cells in a glucose-dependent way. This effect was not related to alpha2-adrenergic, I1-, and I2-imidazoline receptors. RX871024 promoted insulin release by at least two modes of action. One included an increase in cytoplasmic free Ca2+ concentration ([Ca2+]i), subsequent to blocking of ATP-dependent K+ channels, membrane depolarization, and activation of voltage-dependent Ca2+ channels. The other, a more distal effect of imidazoline, affected the exocytotic machinery and was unrelated to changes in membrane potential and [Ca2+]i. The mechanism of RX871024-induced insulin release was dependent on protein kinases A and C. The sensitizing effect of a low dose of RX871024 on glucose-induced insulin secretion suggests that imidazoline compounds of this kind may constitute the basis for development of a new class of oral hypoglycemic agents.

Isoforms of endoplasmic reticulum Ca(2+)-ATPase are differentially expressed in normal and diabetic islets of Langerhans

Glucose-dependent sequestration of Ca2+ into endoplasmic reticulum and its subsequent release play an important role in the control of intracellular Ca2+ concentration, which regulates insulin secretion in pancreatic beta-cells. The active uptake of cytosolic Ca2+ into endoplasmic reticulum is mediated by sarco-(endo)plasmic reticulum Ca(2+)-ATPases (SERCAs). We found, using RT-PCR with isoform-specific primers, that SERCA 2 and SERCA 3 mRNAs are co-expressed in human and rat islets of Langerhans and in the RINm5F beta-cell line. Immunochemical analysis also revealed the existence of two SERCA proteins with molecular masses of 110 and 115 kDa in beta-cell membranes. The 115 kDa protein was identified as SERCA 2b by its reaction with an isoform-specific antibody and the 110 kDa protein most probably corresponds to SERCA 3. The presence of two functionally different SERCA isoforms raises the possibility that they are located in distinct Ca2+ stores. There is evidence that altered Ca2+ handling in the beta-cell may contribute to the decreased insulin secretion seen in non-insulin dependent diabetes mellitus (NIDDM). We therefore investigated SERCA 2 and SERCA 3 mRNA expression by quantitative RT-PCR in islets prepared from Goto-Kakizaki (GK) rats, a non-obese spontaneous model of NIDDM. We found a significant reduction (about 68%) in SERCA 3 isoform expression. Since SERCA 2 expression was not significantly reduced, these genes are independently regulated and probably play distinct roles in islets of Langerhans. The marked decrease of SERCA 3 expression may constitute a defect in Ca2+ signalling in GK rat islets which could be a component of NIDDM.

Increased storage and secretion of islet amyloid polypeptide relative to insulin in the spontaneously diabetic GK rat

We have investigated whether a possible dysregulation of the storage and function of islet amyloid polypeptide (IAPP) in the endocrine pancreas of 4-month-old spontaneously diabetic Goto-Kakizaki (GK) rats might contribute to the impairment of glucose-induced insulin secretion previously reported in these rats. Immunocytochemical studies indicated a significantly lower degree of labeling per beta-cell granule of insulin but not of IAPP in GK islets compared to control islets. Further, the GK rats displayed lower plasma levels of both insulin and IAPP in the fasting state. The pancreatic concentrations of both IAPP and insulin were also significantly lower in the GK rats than in the controls. Following an intraperitoneal glucose injection, the plasma IAPP and insulin concentration of the GK rats did not increase at all, whereas a significant increase in both IAPP and insulin concentration was recorded in the control animals. However, the plasma IAPP/insulin ratio was significantly higher in the GK rats at both 30 and 60 min after glucose injection, which may be a reflection of an increased negative feedback effect of IAPP on insulin release. A relative hypersecretion of IAPP might be one of several factors contributing to the impairment of glucose-induced insulin secretion in this rat model of non-insulin-dependent diabetes mellitus. This is further supported by our electron microscopic observations showing disproportionate IAPP/insulin labeling of beta-cell granules in the GK islets.

Normal hepatic insulin sensitivity in lean, mild noninsulin-dependent diabetic patients

We studied hepatic and extrahepatic insulin sensitivity and insulin release in seven nonobese patients with mild noninsulin-dependent diabetes mellitus (NIDDM) and 10 control subjects, matched for age, body mass index, and physical fitness. Glucose turnover was studied during sequential hyperinsulinemic euglycemic clamps (insulin infusion, 0.25 and 1.0 mU/kg BW.min), applying the hot-GINF (tracer-enriched glucose infusion) technique and using [6-3H]glucose. Hepatic glucose production was lower in hyperglycemic NIDDM patients during the basal period (P < 0.01), but was equivalent at similar glucose and insulin levels attained during both clamps. In contrast, during the low and high insulin clamps, glucose utilization was lower in NIDDM [14.90 +/- 1.00 vs. 17.24 +/- 0.83 (P < 0.01) and 41.37 +/- 3.05 vs. 50.54 +/- 3.61 mumol/kg BW.min (P < 0.01)]. Accordingly, the glucose infusion rate necessary to maintain euglycemia was lower in NIDDM [7.72 +/- 2.00 vs. 10.68 +/- 1.17 (P < 0.05) and 42.14 +/- 4.50 vs. 51.60 +/- 4.28 mumol/kg BW.min (P < 0.01)]. There was, however, a considerable overlap between patients and controls in the parameters describing insulin sensitivity. The insulin response to orally administered glucose as well as that to a standardized glucose infusion test (GIT) were diminished in NIDDM [average incremental insulin secretion during an oral glucose tolerance test, 88 +/- 28 vs. 251 +/- 50 pmol/L.min (P < 0.05); during first 10 min of GIT, 7 +/- 16 vs. 234 +/- 29 pmol/L.min (P < 0.001)]. There was no overlap in acute phase insulin secretion during the GIT between the groups. In conclusion, nonobese, mild NIDDM patients showed no impairment in hepatic, but a slight reduction in extrahepatic insulin sensitivity, with extensive overlap between diabetic and control subjects. In contrast, impairment of insulin release was very pronounced and without overlap.

Pituitary adenylate cyclase activating polypeptide (PACAP) redistributes the blood within the pancreas of anesthetized rats

The aim of the study was to evaluate the effects of pituitary adenylate cyclase activating polypeptide-38 (PACAP-38) on splanchnic blood flow in anesthetized rats. For this purpose, either PACAP-38 dissolved in saline or saline alone was injected intravenously 5 (10 nmol/kg body weight (bw) PACAP-38) and 30 min (5 or 10 nmol/kg) before measurements. The blood flow to the whole pancreas, islets, duodenum and colon was then measured with a microsphere technique. The higher dose of PACAP-38 slightly increased blood glucose concentrations at both 5 and 30 min after administration, whereas the lower had no effect. Both doses of PACAP-38 induced a transient initial decrease in mean arterial blood pressure. The lower dose of PACAP-38 decreased fractional islet blood flow 30 min after administration, but did not affect the other blood flows. The higher dose of the peptide (10 nmol/kg bw) caused an increase in whole pancreatic blood flow at both 5 and 30 min after administration, whereas islet blood flow was only increased at the former time. At both time points PACAP-38 redistributed the blood flow within the pancreas in favour of the exocrine pancreas. This resulted in a decreased fractional islet blood flow, i.e., the fraction of whole pancreatic blood flow diverted through the islets. At 5 min after PACAP-38 administration duodenal blood flow was decreased, whereas after 30 min no effects on duodenal or colonic blood flow were observed. Administration of a VIP antagonist intravenously (20 nmol/kg bw) decreased the PACAP-38-induced pancreatic blood flow increase and intrapancreatic redistribution. When only the VIP antagonist was given both pancreatic and islet blood decreased in concert. It is concluded that administration of PACAP-38 induces a blood flow increase in the pancreas, preferably in the exocrine parts of the gland, by actions mediated by PACAP-38 receptors shared with VIP.

Impaired coupling of glucose signal to the exocytotic machinery in diabetic GK rats: a defect ameliorated by cAMP

The GK rat is a spontaneous model of NIDDM. The insulin response to 16.7 mmol/l glucose was markedly impaired in both isolated perfused pancreas and isolated islets from GK rats compared with control Wistar rats. Depolarization with 30 mmol/l KCl in the presence of 3.3 mmol/l glucose and 250 micromol/l diazoxide induced similar insulin responses in perfused pancreases of GK and control rats. In contrast, the glucose-stimulated insulin release was also severely impaired in GK pancreases in the depolarized state. Forskolin (1 micromol/l) markedly enhanced insulin release at 3.3 mmol/l glucose in GK but not control pancreases (54 +/- 15 vs. 3 +/- 1 pmol/10 min, P < 0.001). Dibutyryl cAMP (1 mmol/l) exerted effects similar to forskolin on insulin release in the perfused pancreas. In depolarized pancreases of GK but not control rats, forskolin also induced a marked insulin response at 3.3 mmol/l glucose (163 +/- 48 vs. 16 +/- 1 pmol/20 min, P < 0.03). Similarly, in studies on isolated islets from GK rats cultured in 5.5 or 16.7 mmol/l glucose for 48 h, forskolin (5 pmol/l) restored insulin release in response to 16.7 mmol/l glucose but had no effect on islet glucose utilization at 3.3 or 16.7 mmol/l glucose. Forskolin markedly stimulated insulin release at 3.3 mmol/l glucose in GK but not control rat islets cultured for 48 h in 5.5 mmol/l glucose, whereas 20 mmol/l arginine had an almost identical effect in both islet varieties. However, in islets cultured in 16.7 mmol/l glucose, forskolin stimulated insulin release similarly both in control and GK islets at 3.3 mmol/l glucose. In conclusion, this study suggests that the insulinotropic effects of glucose are coupled to a direct regulation of the exocytotic machinery in the pancreatic beta-cell. This pathway is markedly impaired in GK rats, contributing to defective insulin response to glucose. In this model, cAMP generation restores the insulin response to 16.7 mmol/l glucose and exerts a marked insulin release even at 3.3 mmol/l glucose.

Normalization by insulin treatment of low mitochondrial glycerol phosphate dehydrogenase and pyruvate carboxylase in pancreatic islets of the GK rat

The enzyme activity of the mitochondrial glycerol phosphate dehydrogenase (mGPD) in the pancreatic islet has been reported to be less than one-half of normal in the Goto-Kakizaki (GK) rat, a genetic model of NIDDM. In the current study, mGPD enzyme activity and the amount of mGPD protein, as judged by Western analysis, were 35-40% of normal in the islets of these animals. With the exception of pyruvate carboxylase, the activities of other enzymes were not abnormal. The assayable activity and amount of pyruvate carboxylase protein were decreased approximately 50% in the islets of the GK rats. Because mGPD, which is the key enzyme of the glycerol phosphate shuttle, and pyruvate carboxylase, which is the key component of the pyruvate malate shuttle, have been proposed to be essential for stimulus-secretion coupling in the pancreatic beta-cell, an important question is whether the decreases in these enzymes have a causal role in the hyperglycemia or whether the diabetic syndrome caused the decreases. To attempt to differentiate between these two possibilities, GK rats were treated with insulin to normalize their blood sugars. The activities of both mGPD and pyruvate carboxylase were also normalized by insulin treatment. An incidental discovery of this study was the identification of a high level of propionyl-CoA carboxylase activity and a lesser amount of methylcrotonyl-CoA carboxylase activity in pancreatic islets. These enzymes were normal in the islets of the GK rats. This is the first report on the presence of these two carboxylases in the islet and of low pyruvate carboxylase activity in the islet in NIDDM. We conclude that the decreased mGPD and pyruvate carboxylase in the pancreatic islet of the GK rat result from the diabetic syndrome.

Increased amounts of a high molecular weight insulin-like growth factor II (IGF-II) peptide and IGF-II messenger ribonucleic acid in pancreatic islets of diabetic Goto-Kakizaki rats

Insulin-like growth factor II (IGF-II), a member of the insulin family, regulates cell growth and differentiation. The IGF-II gene is localized close to the insulin gene in man and rat. IGF-II peptide binds weakly to the insulin receptor and exerts insulin-like effects on the blood glucose level. We studied IGF-II in endocrine pancreas in an animal model of noninsulin-dependent diabetes mellitus, the Goto-Kakizaki (GK) rat. At the age of 2 months, these rats have structural islet changes, with fibrosis and irregular configuration, so-called starfish-shaped islets. Immunohistochemical investigation revealed IGF-II immunoreactivity in the beta-cells in both GK and control rats. Pancreatic extraction, followed by size separation using gel chromatography, disclosed a high mol wt form of IGF-II in all animals, and RIA measurements revealed a considerably larger amount of the IGF-II peptide in the 2-and 6-month-old GK rats than in the 1-month GK and control rats. In situ hybridization of 3-month-old GK rats showed increased IGF-II messenger RNA expression in the starfish-shaped islets of GK rats than in the islets with normal structure in both diabetic and control animals. The reason for the increased amount of IGF-II is unclear. As the animals are diabetic before the islet changes occur, it might be a compensatory effect in response to hyperglycemia, but could also be a cause of the islet fibrosis.

Acute effects of the alpha 2-adrenoreceptor antagonist idazoxan on hormonal responses and symptoms of hypoglycaemia in patients with type 1 diabetes mellitus

The aim of the present study was to evaluate the effect of the alpha 2-adrenoceptor antagonist idazoxan on hormonal responses and hypoglycaemia symptoms in patients with insulin-dependent (Type 1) diabetes mellitus. Six male Type 1 diabetic patients were studied with and without intravenous infusion of idazoxan. Hypoglycaemia was induced by an intravenous infusion of insulin (100 mU.kg-1.h-1), together with a glucose clamp, to obtain an arterialised venous blood glucose level of 2.3 mmol/l. Idazoxan was given at a dose of 295 micrograms/kg. Venous blood samples were obtained for analyses of free insulin, growth hormone (GH), glucagon and catecholamines. Symptoms were scored on a visual-analogue rating scale. Areas under the curves with and without idazoxan were respectively 22.4 +/- 7.0 vs 33.0 +/- 9.6 micrograms.l-1.h (p = 0.17) for GH, 4.1 +/- 1.1 vs 2.4 +/- 0.9 nmol.l-1h (p < 0.05) for adrenaline, 5.6 +/- 0.9 vs 1.3 +/- 0.5 nmol.l-1.h (p < 0.05) for noradrenaline and 51 +/- 38 vs -40 +/- 11 ng.l-1.h (p < 0.05) for glucagon. Sweating and palpitations were more pronounced during idazoxan infusion than during the control test. It is concluded that idazoxan increases catecholamine and glucagon responses as well as some of the warning signals of hypoglycaemia in Type 1 diabetic patients, whereas the GH response seems less affected by idazoxan.

Genetic analysis of non-insulin dependent diabetes mellitus in the GK rat

Non-insulin dependent diabetes mellitus (NIDDM) is a major public health problem, but its aetiology remains poorly understood. We have performed a comprehensive study of the genetic basis of diabetes in the Goto-Kakizaki (GK) rat, the most widely used animal model of non-obese NIDDM. The genetic dissection of NIDDM using this model has allowed us to map three independent loci involved in the disease. In addition, we identify a major factor affecting body weight, but not glucose tolerance, on chromosome 7 and map a further 10 regions that are suggestive for linkage. We conclude that NIDDM is polygenic and fasting hyperglycaemia and postprandial hyperglycaemia clearly have distinct genetic bases.

A defective stimulus-secretion coupling rather than glucotoxicity mediates the impaired insulin secretion in the mildly diabetic F1 hybrids of GK-Wistar rats

Adult F1 hybrids of male GK and female Wistar control rats exhibit mild, spontaneous non-insulin-dependent diabetes mellitus characterized by impaired glucose-induced insulin secretion. Using isolated pancreatic islets of hybrid rats, we first studied whether impaired glucose-induced insulin response is present not only in adult but also in neonatal rats. Furthermore, we investigated whether the impaired glucose-induced insulin response can be restored by long-term normalization of glycemia. Both 1-week- and 2- to 3-month-old hybrid rats had similar body weights but increased fed blood glucose levels (P < 0.05) compared with age-matched control rats. At 5.5 mmol/l glucose, insulin release was two- to threefold lower in isolated islets of hybrid than in control rats of both age groups (P < 0.05). At 16.7 mmol/l glucose, insulin secretion from hybrid islets was approximately 25% of that from control islets of both 1-week- and 2- to 3-month-old rats. For the second objective, batches of 250 islets from hybrid or control rats were transplanted under the kidney capsule of athymic, normoglycemic nude mice and maintained there for 4 weeks. Perfusion of kidneys demonstrated that glucose-induced (16.7 mmol/l) insulin secretion was impaired markedly in hybrid grafts compared with that in control grafts (0.66 +/- 0.23 vs. 1.8 +/- 0.38 pmol/20 min; P < 0.01), whereas stimulation by 20 mmol/l arginine resulted in similar insulin responses in both groups. The volumes of the grafted islets were similar in kidneys bearing either control or hybrid islets.(ABSTRACT TRUNCATED AT 250 WORDS)

Deficiency of pyruvate dehydrogenase activity in pancreatic islets of diabetic GK rats

We investigated the role of islet pyruvate dehydrogenase (PDH) enzyme activity and fatty acid oxidation in the impaired insulin secretion in spontaneously diabetic GK rats. Blood glucose levels were elevated in 2- to 3-month-old GK rats (8.7 +/- 0.5 vs. 6.5 +/- 0.3 mM in control Wistar rats; P < 0.01), whereas serum insulin levels were comparable to those in control rats. Insulin and DNA contents were similar in freshly isolated islets from GK and control rats, whereas insulin responses to 27 mM glucose from GK islets were reduced by 52%. The effect of acetate or pyruvate on insulin responses evoked by succinate monomethylester (SAM) were compared to indirectly assess deficient generation of acetyl-coenzyme A from pyruvate. Acetate potentiated SAM-induced insulin secretion similarly in GK and control islets, whereas 10 mM pyruvate (which supplies acetyl-coenzyme A through PDH enzyme activity) failed to normally potentiate insulin secretion in GK islets (92% of SAM-induced response in GK vs. 154% in control islets). The PDH activity (active form) was decreased in GK islets by 35% (P < 0.001). The proportion of active form PDH to total PDH activity was reduced in GK islets (56% vs. 71% in control islets; P < 0.01). The activity of PDH kinase (which inactivates PDH by phosphorylation) was increased in GK islets, the rate of ATP-dependent inactivation of PDH was -0.29 +/- 0.02 vs. -0.19 +/- 0.02/min in control islets (P < 0.05). Culturing GK islets for 48 h at 5.5 mM glucose failed to correct the impaired insulin response to glucose and the decreased PDH activity. Serum FFA levels and islet triglyceride contents did not differ between GK and control rats. Etomoxir (1.0 and 10 microM), a carnitine palmitoyl transferase I inhibitor, failed to enhance glucose-induced insulin release in GK islets. The following conclusions were reached: 1) a kinase-mediated decrease in PDH activity in islets of GK rats may in part account for the decreased ratio of oxidized to utilized glucose and impaired insulin release in these islets; and 2) impaired insulin release in the GK rats is not linked to an inhibitory influence of islet fatty acid oxidation.

P-fimbriation and haemolysin production are the most important virulence factors in diabetic patients with Escherichia coli bacteraemia: a multivariate statistical analysis of seven bacterial virulence factors

Diabetic patients, as compared to non-diabetic subjects, run an increased risk of acquiring Gram-negative bacteraemia. We therefore studied the prevalence and coexpression of seven bacterial virulence markers of 69 Escherichia coli strains isolated from 64 bacteraemic patients with diabetes mellitus and 67 E. coli strains from faeces of healthy controls. The strains were analyzed for haemolysin (HLY) production, aerobactin-mediated iron uptake (AMI), cytotoxic necrotizing factor (CNF) production, expression of cell surface hydrophobicity, P-fimbriae, mannose-resistant haemagglutination (MRHA) and mannose-sensitive haemagglutination (MSHA). All bacterial properties were significantly more common among the bacteraemic strains (P < 0.02 vs. controls). Correlations between HLY and CNF (P < 0.0004) and between P-fimbriae and MRHA (P < 0.0001), MSHA (P < 0.0002) or AMI (P < 0.05), as well as between MRHA and MSHA (P < 0.0005) were observed. In patients with proteinuria, as sign of diabetic complications in the urinary tract, HLY-negative strains, P-fimbriae-negative strains, and strains which were both HLY-/CNF-negative, were more common (P = 0.04, P < 0.01 and P = 0.048, respectively). Using a multivariate statistical analysis, production of HLY and the expression of P-fimbriae were the two virulence factors with the highest discrimination between bacteraemic and control strains. In conclusion, all virulence factors studied were more prevalent in bacteraemic than in control strains, although HLY and P-fimbriae were shown to be of greatest and independent importance. Low virulent strains (P-fimbriae-, HLY- and CNF-negative) were more prevalent in diabetic patients with signs of renal complications.

Insulin-stimulated glucose uptake is enhanced in sedentary and endurance-trained low insulin responders

The mechanisms by which healthy sedentary subjects with low insulin response (LIR; 5-min insulin response to glucose load within lowest quartile of healthy population) maintain a normal glucose tolerance are not clear. We studied glucose uptake and hepatic glucose production in LIR, in healthy subjects with high insulin response (HIR; two highest quartiles of insulin response) matched for weight and physical fitness, and in endurance-trained subjects (ET). For this purpose, we performed hyperinsulinemic euglycemic clamps using the "hot-GINF" method with high-pressure liquid chromatography purified [6-3H]glucose. All groups had a similar basal glucose appearance rate (Ra). During clamps, plasma insulin levels were doubled to 169 +/- 9 pmol/l, whereas Ra decreased similarly in all groups. Glucose utilization rate increased more in LIR and ET than in HIR (to 20.9 +/- 1.5 mumol.kg-1.min-1 in LIR, P < 0.001 vs. HIR; 27.4 +/- 3.6 in ET, P < 0.01 vs. HIR and LIR; and 14.3 +/- 0.6 in HIR). In conclusion, the present study demonstrates increased insulin sensitivity in LIR and ET with respect to glucose uptake but not glucose production.

Preserved beta-cell density in the endocrine pancreas of young, spontaneously diabetic Goto-Kakizaki (GK) rats

The Goto-Kakizaki (GK) rat represents a spontaneous animal model of non-insulin-dependent diabetes mellitus (NIDDM) characterized by impaired glucose-stimulated insulin release from the pancreatic beta cells. To study whether an alteration in their islet beta-cell numbers occurs in parallel with the impairment of insulin secretion in this model, the relative volume density of beta cells was determined by means of conventional point sampling in immunostained 4-microns-thick sections of the pancreata from 8-week-old GK rats. The pancreata of nondiabetic Wistar rats were used as control parenchyma. In the GK pancreata the majority of islets was found to have a normal structure; only a few of the islets demonstrated an irregular shape (starfish-shaped islets) with fibrosis. The relative volume of the total endocrine parenchyma was found to be 2.0 +/- 0.6% (mean +/- SEM) of the whole pancreatic parenchyma in GK rats. In the control rats the corresponding value was 2.3 +/- 0.5%. The islet beta-cell density was also similar in GK and control rat islets, amounting to 75.2 +/- 8.5 and 66.9 +/- 6.6%, respectively. Thus, the total relative volume of beta cells was 1.5 +/- 0.5% in GK rats and 1.6 +/- 0.4% in controls. In conclusion, the density of beta cells is preserved in the pancreata of the young, diabetic GK rats, suggesting the absence of a causal relationship between the relative pancreatic beta-cell volume and the impaired glucose-induced insulin secretion in this NIDDM animal model.

Development of decreased insulin-induced glucose transport in skeletal muscle of glucose-intolerant hybrids of diabetic GK rats

1. The effect of glucose intolerance on insulin-stimulated glucose transport in isolated skeletal muscles was investigated in male F1 hybrids of spontaneously diabetic GK (Goto-Kakizaki) and control Wistar rats at 1 and 2 months of age. 2. Hybrid rats are characterized by markedly impaired glucose-induced insulin secretion. The area under the blood glucose curve was significantly higher following an intraperitoneal glucose injection (2 g/kg) in hybrid rats in both age groups than in the control rats (P < 0.001). In 2-month-old hybrid rats the incremental area under the insulin curve during the intraperitoneal glucose tolerance test was not different from that of control rats. Serum cholesterol, triacylglycerol or plasma free fatty acid levels did not differ between the groups. Fasting and post-prandial plasma glucose concentrations were elevated in 2-month-old hybrid rats compared with control rats (54%, P < 0.05, and 27%, P < 0.05, respectively), but were not different in 1-month-old rats. Plasma insulin did not differ between the hybrid and control rats in the fasting or post-prandial state at either age studied. 3. The insulin dose-response curves for 3-O-methylglucose transport did not differ between 1-month-old hybrid and control rats for either the soleus or epitrochlearis muscle. The insulin dose-response curve for the epitrochlearis, but not for the soleus, muscle from 2-month-old hybrid rats was shifted to the right compared with the curve from the control animals (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Glycogen synthase, glycogen phosphorylase and alpha-amylase activity in homogenates of islets of GK rats: comparison with hepatic and pancreatic extracts

Glycogen accumulation in pancreatic islet cells in situations of sustained hyperglycaemia may participate in the phenomenon of so-called B-cell glucotoxicity. Unexpectedly, however, previously little if any glycogen was found in islet cells of non-insulin-dependent diabetic Goto-Kakizaki rats (GK rats). Therefore, the activities of glycogen synthase, glycogen phosphorylase and alpha-amylase were measured in islets of control and GK rats. No significant difference in enzymatic activity was observed between the control and diabetic animals. In the liver, the activity of glycogen synthase appeared even somewhat higher in GK rats than in control animals. It is concluded that the diabetic syndrome in the GK rats does not involve any major anomaly of glycogen synthase and glycogen phosphorylase activity in the liver of these animals, as well as alpha-amylase, in pancreatic islets.

Inhibition of nitric oxide synthase by NG-nitro-L-arginine causes a preferential decrease in pancreatic islet blood flow in normal rats and spontaneously diabetic GK rats

To elucidate the effect of nitric oxide (NO) on the blood flow of the pancreatic islets, the NO synthase inhibitor NG-nitro-L-arginine (N-arg; 25 mg/kg BW) was administered iv to rats 10 min before pancreatic blood flow was measured with a nonradioactive microsphere technique. In male Sprague-Dawley rats, N-arg induced a marked decrease in islet blood flow (16 +/- 4 vs. 44 +/- 8 microliters/min.g pancreas; P < 0.001) and a less pronounced decrease in whole pancreatic blood flow (0.27 +/- 0.04 vs. 0.43 +/- 0.06 ml/min.g; P < 0.05), leading to a markedly decreased fractional islet blood flow (5.5 +/- 0.9% vs. 10.3 +/- 1.3%; P < 0.02). In a second experiment, injection of D-glucose (300 mg/kg BW, iv) in male Sprague-Dawley rats induced a selective increase in islet blood flow (P < 0.05). Such an increase has previously been shown to be mediated by a vagal cholinergic mechanism. Administration of N-arg to these rats resulted in decreased pancreatic (P < 0.05), islet (P < 0.001), and fractional (P < 0.001) islet blood flow, which did not differ from those observed in normoglycemic rats after treatment with N-arg. Furthermore, we studied the mechanism behind the previously described increase in islet blood perfusion, mediated by the vagus nerve, in F1-hybrids of the GK (Goto-Kakizaki) rat, a spontaneous animal model of noninsulin-dependent diabetes mellitus. Administration of N-arg to female GK rats resulted in decreases in islet (P < 0.001), pancreatic (P < 0.01), and fractional islet blood flow (P < 0.001) to the levels observed in female Wistar rats treated in parallel. These data are consistent with the possibility that NO is an important physiological regulator of islet blood flow. Furthermore, the vagally dependent high levels of islet blood flow demonstrated in the GK rat appear to be mediated by a mechanism involving NO.

Inter-relationship between serum concentrations of glucose, glucagon and insulin during the first two days of life in healthy newborns

The relationship between serum concentrations of glucose, insulin and glucagon during the first two days of life was studied in healthy newborns. The first capillary blood sample was obtained at 3-15 h of age (median 6 h; day 0) and a second sample approximately 24 h later (day 1). Serum glucose concentrations in the first sample averaged 2.1 +/- 0.07 mmol/l (mean +/- SEM; n = 60) and were positively correlated with postnatal age (p < 0.01). Serum glucagon concentrations in the first sample averaged 570 +/- 32 pg/ml and were inversely correlated with glucose concentrations (p < 0.0001). At the second sampling, serum glucose concentrations had increased to 2.9 +/- 0.07 mmol/l (p < 0.001; n = 57) and serum glucagon concentrations had decreased to 403 +/- 22 pg/ml (p < 0.001). Serum insulin concentrations were 11.7 +/- 0.3 microU/ml and 10.2 +/- 0.3 microU/ml at the two samplings and did not correlate with serum glucose concentrations. The relationship of serum glucose and hormone concentrations to maternal and infant characteristics was studied by stepwise regression analysis. Serum glucose concentration on day 0 was positively correlated with postnatal age (p < 0.01) and birth weight (p < 0.05) but inversely correlated with duration of labour (p < 0.05). Serum glucose concentration on day 1 was positively correlated with birth weight (p < 0.0001) and inversely correlated with maternal prep-pregnancy weight (p < 0.05). Similar analyses of serum hormone concentrations did not demonstrate any relationships with maternal or infant characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Physical fitness and insulin sensitivity in human subjects with a low insulin response to glucose

1. We have assessed insulin secretion, insulin sensitivity, exercise capacity and muscle fibre composition in healthy men with a low insulin response to glucose (low insulin responders and endurance-trained subjects) and in healthy men with a normally high insulin response. Low insulin responders have been considered as prediabetic subjects. 2. During glucose infusion, low insulin responders and endurance-trained subjects had acute-phase (0-10 min) insulin responses that were 26% (P < 0.001) and 31% (P < 0.001), and C-peptide responses that were 35% (P < 0.001) and 42% (P < 0.01), respectively of the responses in high insulin responders. Also, the late-phase (10-60 min) insulin and C-peptide responses were lower in low insulin responders and endurance-trained subjects. Endurance-trained subjects, compared with high and low insulin responders, had higher insulin sensitivity (blood glucose concentration during a somatostatin-insulin-glucose infusion test 3.6 +/- 0.4 versus 6.3 +/- 0.6 mmol/l in high insulin responders, P < 0.01, and 5.5 +/- 0.4 mmol/l in low insulin responders, P < 0.01), exercise capacity (4.2 +/- 0.2 versus 3.0 +/- 0.2 W/kg body weight, P < 0.001, and 2.8 +/- 0.1 W/kg body weight, P < 0.001) and a higher percentage of slow-twitch fibres (58.2 +/- 5.2 versus 38.5 +/- 3.5%, P < 0.01 and 40.9 +/- 3.0%, P < 0.001). 3. In conclusion, we demonstrate that low insulin responders exhibited decreased insulin and C-peptide responses to glucose, despite normal insulin sensitivity and exercise capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition by rat diazepam-binding inhibitor/acyl-CoA-binding protein of glucose-induced insulin secretion in the rat

Diazepam-binding inhibitor (DBI) has been localized immunohistochemically in many organs. In porcine and rat pancreas, DBI is present in non-B-cells of the pancreatic islets. Porcine peptide also has been shown to suppress insulin secretion from rat pancreas in vitro. Recently, acyl-CoA-binding protein (ACBP) was isolated from rat liver and shown to be identical structurally to DBI isolated from rat brain. Using this rat DBI/ACBP, we have studied its effects on glucose-stimulated insulin secretion in the rat, both in vivo and in isolated pancreatic islets. Infusion iv of rDBI/ACBP (25 pmol/min) during glucose stimulation induced a moderate and transient reduction of plasma insulin levels. Moreover, rDBI/ACBP suppressed insulin release from batch-incubated isolated islets, stimulated by 16.7 mmol/l glucose, by 24% at 10 nmol/l (p < 0.05) and by 40% at 100 nmol/l (p < 0.01). The peptide (100 nmol/l) also inhibited the insulin response to glucose (16.7 mmol/l) from perifused rat islets by 31% (p < 0.05), mainly by affecting the acute-phase response. Finally, incubation of isolated islets in the presence of rDBI/ACBP antiserum (diluted 1:100 and 1:300) augmented the insulin response to 16.7 mmol/l glucose (p < 0.05 or even less). We conclude that rDBI/ACBP, administered iv or added to the incubation media, suppresses insulin secretion in the rat but that the effect is moderate despite the high concentration used. It is therefore unlikely that the peptide modulates islet hormone release, acting as a classical hormone via the circulation. However, the occurrence of DBI/ACBP in the islets and the enhancing effect by the rDBI/ACBP antibodies on glucose-stimulated insulin release suggest that the peptide is a local modulator of insulin secretion.

Pancreatic and islet blood flow in F1-hybrids of the non-insulin-dependent diabetic GK-Wistar rat

Previous studies have indicated that various conditions under which an increased functional load is posed on the pancreatic islets, e.g. partial pancreatectomy and continuous glucose infusions, may influence the microcirculation of the pancreas. To investigate further the effects of elevated functional demand on the islets, the blood perfusion of the whole pancreas and the pancreatic islets was measured with a microsphere technique in an animal model presenting impaired glucose tolerance and mild hyperglycemia, namely F1-hybrids of the spontaneously non-insulin-dependent diabetic GK-Wistar rat. Normal Wistar rats served as controls. All hybrids had a pathological intraperitoneal glucose tolerance test 1 week before the blood flow measurements, which were performed in 10-12-week-old rats. Both the whole pancreatic and the islet blood flows were increased in the hybrids compared to controls. The fractional islet blood flow, i.e. the fraction of whole pancreatic blood flow diverted through the islets, also was increased in the hybrid rats (12.6 +/- 0.6% vs 9.8 +/- 0.5% in controls, p < 0.01). A bilateral abdominal vagotomy performed 30 min before the blood flow measurement markedly decreased the blood flow values of the islets and the whole pancreas in both groups of rats. After vagotomy, the islet blood flow in the hybrid rats was similar to that of the vagotomized control animals (8.2 +/- 0.8 and 7.5 +/- 1.4%, respectively). It is concluded that the increased pancreatic and islet blood perfusion observed in F1-hybrids of the GK-Wistar rat depends on a mechanism mediated by the vagus nerve.

A porcine gut polypeptide identical to the pancreatic hormone PP (pancreatic polypeptide)

A peptide hormone has been isolated from porcine intestine. Its primary structure was found to consist of 36 amino acid residues in a sequence identical to that of the porcine pancreatic polypeptide, previously not isolated from intestines or a tissue other than pancreas. The gut polypeptide significantly suppresses glucose-induced insulin secretion in vitro. Using an immunohistochemical technique, we also identified cells in the porcine gastrointestinal tract that were immunoreactive with pancreatic polypeptide. The immunoreactivity disappeared after absorption with the isolated gut polypeptide or synthetic human pancreatic polypeptide.