Ove Svendsen

Capsaicin-sensitive sensory fibers in the islets of Langerhans contribute to defective insulin secretion in Zucker diabetic rat, an animal model for some aspects of human type 2 diabetes

The system that regulates insulin secretion from β‐cells in the islet of Langerhans has a capsaicin‐sensitive inhibitory component. As calcitonin gene‐related peptide (CGRP)‐expressing primary sensory fibers innervate the islets, and a major proportion of the CGRP‐containing primary sensory neurons is sensitive to capsaicin, the islet‐innervating sensory fibers may represent the capsaicin‐sensitive inhibitory component. Here, we examined the expression of the capsaicin receptor, vanilloid type 1 transient receptor potential receptor (TRPV1) in CGRP‐expressing fibers in the pancreatic islets, and the effect of selective elimination of capsaicin‐sensitive primary afferents on the decline of glucose homeostasis and insulin secretion in Zucker diabetic fatty (ZDF) rats, which are used to study various aspects of human type 2 diabetes mellitus. We found that CGRP‐expressing fibers in the pancreatic islets also express TRPV1. Furthermore, we also found that systemic capsaicin application before the development of hyperglycemia prevents the increase of fasting, non‐fasting, and mean 24‐h plasma glucose levels, and the deterioration of glucose tolerance assessed on the fifth week following the injection. These effects were accompanied by enhanced insulin secretion and a virtually complete loss of CGRP‐ and TRPV1‐coexpressing islet‐innervating fibers. These data indicate that CGRP‐containing fibers in the islets are capsaicin sensitive, and that elimination of these fibers contributes to the prevention of the deterioration of glucose homeostasis through increased insulin secretion in ZDF rats. Based on these data we propose that the activity of islet‐innervating capsaicin‐sensitive fibers may have a role in the development of reduced insulin secretion in human type 2 diabetes mellitus.

High-fat high-energy feeding impairs fasting glucose and increases fasting insulin levels in the Göttingen minipig: results from a pilot study.

Abstract: High‐fat diet and obesity are known to be of major importance for development of type 2 diabetes in humans. High‐fat feeding can induce syndromes of glucose intolerance and/or insulin resistance in several species, and the Göttingen minipig might be a useful model for studying the effect of dietary high‐fat intake and obesity on glucose homeostasis and the susceptibility to diabetes. The present study was designed as a pilot study to investigate the effects of obesity caused by high‐fat high‐energy feeding on oral and intravenous glucose tolerance. Male Göttingen minipigs were fed a control diet (CD) or a high‐fat high‐energy diet (HFD) for 3 months. Body weight (32.6 ± 2.4 kg vs. 24.9 ± 0.5 kg, p < 0.001) and total (13.2 ± 3.2% vs. 6.1 ± 0.5%, p= 0.002) and truncal (11.0 ± 3.9% vs. 1.8 ± 1.1%, p= 0.001) fat percent were increased significantly, whereas relative lean body mass was decreased (84.8 ± 3.3% vs. 91.9 ± 0.5%, p= 0.002) in the HFD group compared to CD. Fasting plasma glucose (4.3 ± 0.4 mM vs. 3.6 ± 0.3 mM, p= 0.023) and insulin (80 ± 23 pM vs. 23 ± 21 pM, p= 0.012) were increased in the HFD group compared to CD, but oral glucose tolerance was not significantly changed. Insulin responses to intravenous glucose were increased (6741 ± 2538 vs. 3938 ± 771 pM 3 min, p= 0.050), while glucose clearance was not changed by HFD vs. CD, thus indicating insulin resistance. In conclusion, changes in body weight and composition, resulting in minor abnormalities in glucose tolerance and insulin sensitivity, characterized by slight hyperglycemia and compensatory hyperinsulinemia, can be induced in the male Göttingen minipig by high‐fat high‐energy feeding for 3 months. This approach seems to be an interesting and promising method for establishment of a nonrodent model of insulin resistance or type 2 diabetes.

Importance of guanine nitration and hydroxylation in DNA in vitro and in vivo.

Guanine (Gua) modification by nitrating and hydroxylating systems was investigated in DNA. In isolated calf thymus DNA, 8-NO(2)-Gua and 8-oxo-Gua were dose-dependently formed with peroxynitrite, and 8-NO(2)-Gua was released in substantial amounts. Myeloperoxidase (MPO) with H(2)O(2) and NO(2)(-) reacted with calf thymus DNA to form 8-NO(2)-Gua dose dependently without release of 8-NO(2)-Gua. The frequency of strand breaks was higher than the sum of 8-NO(2)-Gua and 8-oxo-Gua, particularly in the MPO-treated DNA, indicating the importance of other types of damage. The activation of human neutrophils and lymphocytes with phorbol ester did not induce 8-NO(2)-Gua and 8-oxo-Gua in their nuclear DNA. However, 8-NO(2)-Gua was found in calf thymus DNA co-incubated with activated neutrophils in the presence of NO(2)(-). No significant formation of 8-NO(2)-Gua was found in liver DNA from mice treated with Escherichia coli lipopolysaccharide. The incubation of peroxynitrite or MPO-H(2)O(2)-NO(2)(-)-treated DNA with formamidopyrimidine glycosylase (Fpg) released 8-oxo-Gua, but not 8-NO(2)-Gua, indicating that 8-NO(2)-Gua is not a substrate for Fpg. Although 8-NO(2)-Gua was generated in isolated DNA by different nitrating systems, other types of damage were formed in abundance, and the lesion could not be found reliably in nuclear DNA, suggesting that the biological importance is limited.

Plasma digoxin after parenteral administration Local reaction after intramuscular injection

Concentrations of digoxin in plasma after intravenous or intramuscular administration were measured in 8 sub;ects. Two hours after intramuscular in;ection concentrations were higher than after intravenous in;ection. A similar difference between the concentrations of digoxin in plasma was observed after intravenous and intramuscular administration to pigs. The shape of the curves was also similar to that of curves in man. Postmortem examination of the iniection sites in pigs revealed large necrotic areas after intramuscular in;ection of digoxin. The size of the necrotic area increased with the volume iniected. Necrotic areas were also demonstrated after intramuscular in;ection of the vehicle without digoxin, but they were smaller.

Increased manganese concentration in the liver after oral intake1

RATIONALE AND OBJECTIVES Manganese is a well-known liver-specific agent used in magnetic resonance imaging. For this purpose, manganese is now administered intravenously. In theory it should be possible to increase the gastrointestinal uptake of manganese through the use of nutritional products as promoters. Such an agent has now been formulated. As part of a primary pharmacologic investigation, the uptake of manganese in the kidney, heart, and liver was studied. MATERIALS AND METHODS One hundred two female Sprague Dawley rats fasted for 18 hours before the agent (CMC-001) was given orally by gavage. One hundred micromol/kg BW was given to all rats except six, who served as controls. Various concentrations of the promoters (vitamin D3 and the amino acid alanine) were also given. Three hours after administration the rats were killed and the heart, the liver and kidneys were removed. The manganese content was determined by atomic absorption. RESULTS No systematic increased concentration of manganese was found in either the kidneys or the heart; whereas the manganese content of the liver (approximately 100%) increased significantly compared with the controls and the group receiving pure manganese. No side effects were observed. CONCLUSION It is possible to increase the gastrointestinal uptake of manganese in fasting rats and thereby increase the concentration in the liver.

The young göttingen minipig as a model of childhood and adolescent obesity: Influence of diet and gender

Gender and sex hormones influence the development of obesity and metabolic syndrome in humans and Göttingen minipigs. The aim of this study was to investigate possible gender differences in the metabolic response to a high energy diet in young Göttingen minipigs as a model of childhood/adolescent obesity.

Influence of castration-induced testosterone and estradiol deficiency on obesity and glucose metabolism in male Göttingen minipigs.

Low testosterone and estradiol concentrations are predictive for the development of the metabolic syndrome in men and women, respectively. The aim of this study was to investigate the influence of sex hormone deficiency on food intake, body weight, body composition and glucose metabolism in male Göttingen minipigs. Five adult male Göttingen minipigs were studied before castration (pre-cast), 10-18 days (post-cast 1) and 10-11 weeks (post-cast 2) after castration. Parameters of interest were food intake, body weight, body fat percentage and sex hormone concentrations. Furthermore glucose tolerance, glucagon suppression, insulin resistance, beta cell function and disposition index were evaluated by oral and intravenous glucose tolerance tests. Castration led to almost complete disappearance of circulating testosterone and estradiol and secondarily to increased food intake, body weight and body fat percentage. Ten-eighteen days sex hormone deficiency (post-cast 1) did not significantly change any of the investigated metabolic parameters compared to pre-cast levels. Ten weeks after castration (post-cast 2) significant insulin resistance, glucose intolerance and hyperglucagonemia was found, and the beta cell function and the disposition index both were decreased. In conclusion, castration-induced sex hormone deficiency in male Göttingen minipigs results in hyperphagia, obesity and disturbed glucose metabolism, which are some of the features typical for the human metabolic syndrome.

Urine profiles and kidney histology after intravenous injection of ionic and nonionic radiologic and magnetic resonance contrast media in normal rats

RATIONALE AND OBJECTIVES Previous studies showed that both high-osmolality and low-osmolality iodinated contrast media cause temporary albuminuria and enzymuria (presence of enzymes in urine) in normal rats. Whether the same is true with ionic high-osmolality and nonionic low-osmolality magnetic resonance (MR) contrast media is unknown. We studied urine profiles and histology after intravenous injection of four types of contrast media in rats with normal kidneys. METHODS Urine profiles were monitored 4, 24, 48, and 72 hr after intravenous injection of saline, diatrizoate, iohexol, gadopentetate dimeglumine, and gadodiamide (4.59 mmol/kg of body weight) in normal rats. Each group included 20 male rats. After sacrifice, both kidneys were removed for examination by light microscopy (LM) and electron microscopy (EM). RESULTS All four contrast agents caused a temporary (< 22 hr) increase in the excretion of albumin (2-5 times) and of cytoplasmic (30-100 times) and brush border (10-100 times) renal enzymes when compared with saline. The degree of albuminuria correlated well (r = 0.90) with the osmolality of the injected media, whereas the increased level of enzymuria was unrelated to the osmolality. No major differences in the enzymuric effects of the four agents were noted. LM revealed vacuoles in all kidneys exposed to radiologic contrast media but not in kidneys exposed to MR contrast media or saline. Slight vacuolation was revealed by EM after the use of MR contrast media, and significant vacuolation was evident via EM after the use of radiologic contrast media. No difference between ionic and nonionic media within each drug group was detected by either LM or EM. CONCLUSIONS Transient renal effects are induced by both ionic and nonionic high-osmolality and low-osmolality radiologic and MR contrast media in normal rats. Both osmotic (e.g., albuminuria) and chemotoxic (e.g., enzymuria) mechanisms seem to be involved. From a morphologic point of view, the chemotoxic mechanisms seem to be of major importance.

Valine Pyrrolidide Preserves Intact Glucose-Dependent Insulinotropic Peptide and Improves Abnormal Glucose Tolerance in Minipigs With Reduced β-Cell Mass

The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are important in blood glucose regulation.However, both incretin hormones are rapidly degraded by the enzyme dipeptidyl peptidase IV (DPPIV). The concept of DPPIV inhibition as a treatment for type 2 diabetes was evaluated in a new large animal model of insulin-deficient diabetes and reduced β-cell mass, the nicotinamide (NIA) (67 mg/kg) and streptozotocin (STZ) (125 mg/kg)–treated minipig, using the DPPIV inhibitor, valine pyrrolidide (VP) (50 mg/kg).VP did not significantly affect levels of intact GLP-1 but increased levels of intact GIP (from 4543 ± 1880 to 9208 ± 3267 pM × min; P<.01), thus improving glucose tolerance (area under the curve [AUC] for glucose reduced from 1904 ± 480 to 1582 ± 353 mM × min;P = .05).VP did not increase insulin levels during the oral glucose tolerance test (OGTT) but increased the insulinogenic index in normal animals (from 83 ± 42 to 192 ± 108; P < .05), but not after NIA + STZ, possibly because of less residual insulin secretory capacity in these animals. GIP seems to contribute to the antihyperglycemic effect of VP in this model; however, additional mechanisms for the effect of DPPIV inhibition cannot be excluded. The authors conclude that DPPIV inhibitors may be useful to treat type 2 diabetes, even when this is due to reduced β-cell mass.

Determination of the disappearance rate of iodine-125 labelled oils from the injection site after intramuscular and subcutaneous administration to pigs.

The rate of disappearance of clinically used vegetable oils, Viscoleo, sesame oil, castor oil and isopropyl myristate, from the injection site after intramuscular (i.m.) or subcutaneous (s.c.) administration to pigs were determined by using a non-invasive gamma-scintigraphy method. All the oil vehicles were spiked with 2.5% (v/v) (125)I-triolein and six injections of 1.9 ml were given to each of 12 pigs. No significant difference (ANOVA) in disappearance rate of each individual oil vehicle from the different injection sites was observed after administration of the oils: i.m. in the lower back, s.c. in the neck and s.c. in the mid-back. Likewise, no inter-individual difference between the pigs was observed. The half-life of 14 days for Viscoleo was significantly smaller than those of the other oil vehicles (P<0.0001), i.e. 23,20,20 days for sesame oil, castor oil and isopropyl myristate, respectively. Due to the spreading effect of the oils and reflux of the oils through the injection canal, the half-lives were calculated omitting the data for the first sampling day.