Micro- and macrovesicular steatotic liver model for transplantation induced by ethanol and protein-deficient diet

Steatotic liver grafts are associated with a high incidence of primary nonfunction and initial poor function. Due to the increasing number of liver transplant candidates, centers are inclined to accept marginal donors more frequently. For a lack of a reliable fatty liver model, preservation concepts for fatty livers have hardly been evaluated. Moreover, there is an ongoing debate on the relevance and impact of micro- versus macrovesicular steatotic organs. We therefore intended to establish a steatotic liver model in pigs comprising both micro- and macrovesicular steatotic livers. Five groups of pigs received daily 1 to 6 g ethanol/kg body weight and/or a protein-deficient diet for up to 72 days. Liver biopsy was carried out at days 24, 48, and 72. With an increasing amount and duration of ethanol intake, higher levels of microvesicular steatosis were induced. Ethanol and protein deficient diet resulted in more than 60% microvesicular steatosis after 72 days. Exclusively protein-deficient diet without ethanol induced macrovesicular steatosis of more than 70% after 72 days. For the first time, we established a porcine model of hepatic steatosis that comprises both histologic types of fatty liver: micro- and macrovesicular steatosis induced by ethanol and a protein-deficient diet. We would like to conclude that our model is particularly qualified to study new concepts of preservation for steatotic livers to improve on the posttransplant outcome.

Glucose concentration and AMP-dependent kinase activation regulate expression of insulin receptor family members in rat islets and INS-1E beta cells

AIMS/HYPOTHESIS

Glucose and the peptide growth factors insulin, IGF-I and IGF-II strongly regulate beta cell mass. Furthermore, beta cell expression of IGF-I receptor (Igf1r) and insulin receptor (Insr) is mandatory for several steps of insulin secretion.

MATERIALS AND METHODS

We hypothesised that glucose concentration might regulate expression of Igf1r, Insr and insulin receptor-related receptor (Insrr) in islets and beta cells. Moreover, since the ratio of ATP:ADP is the most important intracellular mechanism involved in insulin secretion, and since depletion of ATP leads to AMP accumulation, we evaluated the role of AMP-activated protein kinase (AMPK) in glucose-dependent receptor regulation.

RESULTS

In rat islets, high glucose exposure (25 mmol/l) increased gene expression of Igf1r, Insr and Insrr but also of the metabolic glycolysis gene liver-type pyruvate kinase (Pklr) compared with intermediate (6.2 mmol/l) or low glucose concentration (1.6 mmol/l) after 24 h. In rat INS-1E beta cells, only Pklr expression was suppressed by low glucose as in islets, while Insr and Insrr were suppressed by high and increased by low glucose levels. Igf1r expression was suppressed by both high- and low- glucose concentration. Activation of AMPK by 5-amino-imidazolecarboxamide riboside (AICAR, 0.5 mmol/l) suppressed Pklr expression, but strongly stimulated gene expression of Igf1r, Insr and Insrr. Protein expression of IR and IGF-IR reflected glucose and AICAR-regulated mRNA expression of both receptors in INS-1E cells.

CONCLUSIONS/INTERPRETATION

We conclude that glucose directly interacts with islet and beta cell expression of growth factor receptors that are mandatory for both beta cell growth and insulin secretion. Stimulation of Igf1r and Insr gene expression by the AMPK-activator AICAR might indicate involvement of AMPK in the regulation of Igf1r, Insr and Insrr expression in beta cells.

Neurohumoral stimulation in type-2-diabetes as an emerging disease concept

Neurohumoral stimulation comprising both autonomic-nervous-system dysfunction and activation of hormonal systems including the renin-angiotensin-aldosterone system (RAAS) was found to be associated with Type-2-diabetes (T2D). Therapeutic strategies such as RAAS interference proved to be beneficial in both T2D treatment and prevention. In addition to an activated RAAS, hyperleptinemia in obesity, hyperinsulinemia in conditions of peripheral insulin resistance and overall oxidative stress in T2D represent known activators of the sympathetic component of the autonomic nervous system. Here, we hypothesize that sympathetic activation may cause peripheral insulin resistance defined as partial blocking of insulin effects on glucose uptake. Resulting hyperinsulinemia or hyperglycemia-related oxidative stress may further aggravate sympatho-excitation. This notion leads to a secondary hypothesis: sympathetic activation worsens from obesity towards insulin resistance, and further towards T2D. In this review, existing evidence relating to neurohumoral stimulation in T2D and consequences thereof, such as oxidative stress and inflammation, are discussed. The aim of this review is to provide a rationale for therapies, which are able to intercept neuroendocrine pathways in T2D and precursor states such as obesity.

GH is a positive regulator of tumor necrosis factor alpha-induced adipose related protein in 3T3-L1 adipocytes

Tumor necrosis factor (TNF) alpha-induced adipose-related protein (TIARP) has recently been cloned as a TNFalpha-stimulated protein expressed in adipocytes. Its expression is differentiation-dependent and potentially involved in mediating TNFalpha-induced insulin resistance. To further characterize regulation of TIARP gene expression, 3T3-L1 adipocytes were treated with key hormones modulating insulin sensitivity and influencing adipocyte metabolism, and TIARP gene expression was determined by quantitative real-time RT-PCR. Interestingly, TIARP mRNA expression was stimulated almost 9-fold after 500 ng/ml GH were added for 16 h whereas addition of 10 microM isoproterenol, 100 nM insulin and 100 nM dexamethasone for 16 h significantly decreased TIARP gene expression to between 35 and 50% of control levels. In contrast, angiotensin 2 (10 microM) and triiodothyronine (1 microM) did not have any effect. The stimulatory effect of GH was time- and dose-dependent with stimulation occurring as early as 1 h after effector addition and at concentrations as low as 5 ng/ml GH. Moreover, pharmacological inhibition of Janus kinase 2 and p42/44 mitogen-activated protein kinase reversed the stimulatory effect of GH, suggesting that both signaling molecules are involved in activation of TIARP gene expression by GH. Furthermore, an increase of TIARP mRNA could be completely reversed to control levels by withdrawal of GH for 24 h. Taken together, these results show that TIARP is not only responsive to TNFalpha but also to important other hormones influencing glucose homeostasis and adipocyte metabolism. Thus, this factor may play an integrative role in the pathogenesis of insulin resistance and its link to obesity.

Improvement of insulin sensitivity after adrenalectomy in patients with pheochromocytoma

OBJECTIVE

Decreased insulin secretion is considered to be the main cause for pheochromocytoma-associated diabetes mellitus. Data from animal and evidence from clinical studies suggest that catecholamines can induce insulin resistance. However, there is no study investigating the effect of catecholamine excess on insulin resistance in patients with pheochromocytopma by the euglycemic hyperinsulinaemic clamp technique.

RESEARCH DESIGN AND METHODS

We characterized the effect of high catecholamine plasma concentrations on glucose metabolism and insulin resistance. Euglycemic hyperinsulinemic clamps were performed in 10 patients with pheochromocytoma with and without diabetes mellitus before and 5 wk after adrenalectomy.

RESULTS

In five patients with diabetes mellitus, glucose infusion rate required to maintain euglycemia during the clamp (mean +/- SEM) significantly improved from 27.5 +/- 6.5 micro mol/kg.min before surgery to 44.6 +/- 12.3 micro mol/kg.min 5 wk after adrenalectomy (P < 0.05). In five individuals without diabetes, total glucose disposal improved from 105 +/- 13.6 to 130 +/- 11.2 (P < 0.05). Improved insulin sensitivity after surgery was confirmed by a decrease of fasting hyperinsulinemia from 210 +/- 74 pmol/liter (diabetes mellitus) and 69 +/- 9 pmol/liter (no diabetes) before to 134 +/- 56 pmol/liter and 54 +/- 8 after surgery respectively (P < 0.01). In three patients, diabetes and hyperinsulinemia were reversed by the surgical removal of the pheochromocytoma.

CONCLUSION

Our data provide evidence that endogenous catecholamine excess in patients with pheochromocytoma can induce or aggravate insulin resistance both in patients with type 2 diabetes and patients with normal glucose tolerance.

Analysis of the relationship between PPAR-gamma 2 gene variants and severe insulin resistance in obese patients with impaired glucose tolerance

Mutations in the peroxisome proliferator-activated receptor-gamma 2 (PPAR-gamma 2) gene may cause obesity and insulin resistance. Therefore we investigated whether known variants in the PPAR-gamma 2 gene are associated with obesity and extreme insulin resistance in obese patients with impaired glucose tolerance (IGT). The Pro115 Gln, Pro12Ala, Pro467Leu, Val290Met and a silent polymorphism C478 T were examined in 48 subjects with IGT and insulin resistance (IR), characterized by euglycemic hyperinsulinemic clamps, and in 52 healthy insulin sensitive (IS) controls. We found one proband in the IR group with the Pro115 Gln variant. This subject showed a lower whole body glucose uptake (18 micromol/kg per min) compared to the entire IR group (29 micromol/kg per min). The body weight of the proband (BMI 28.5 kg/m2) was within the average of the IR group (30.3 +/- 0.8 kg/m2). The Pro12Ala variant was not associated with differences in BMI, in the degree of insulin resistance between the IR and IS group. The Pro467Leu, Val290Met mutations and the silent polymorphism CAC478CAT were not detected in any group. In conclusion, the Pro115 Gln variant, but not the Pro12Ala mutation in the PPAR-gamma 2 gene, could be a rare cause of severe insulin resistance.

Lack of association between peroxisome proliferator-activated receptor-gamma-2 gene variants and the occurrence of coronary heart disease in patients with diabetes mellitus

OBJECTIVE

Recent evidence indicates that peroxisome proliferator-activated receptor-gamma (PPARgamma) is expressed at high levels in foam cells of atherosclerotic lesions, that PPARgamma agonists may directly modulate vessel wall function and that mutations in the PPARgamma-2 gene are associated with a reduced risk of coronary artery disease.

METHODS

We investigated whether known variants in the PPARgamma-2 gene are associated with the occurrence of coronary heart disease (CHD) in 365 patients with type 2 diabetes, prospectively characterised for the presence or absence of CHD. The Pro115Gln, Pro12Ala, Pro467Leu, Val290Met mutations and two polymorphisms C478T and C161T of the PPARgamma-2 gene were examined using PCR, denaturing gradient gel electrophoresis and direct sequencing.

RESULTS

The distribution of the Pro12Ala, Ala12Ala, C161T and T161T variants was not significantly different between patients with and without CHD, independent of the gender. The Pro12Ala (P=0.011) and the Ala12Ala (P=0.006) variant were associated with a higher body mass index (BMI) compared with the Pro12Pro genotype. A multiple logistic regression analysis introducing the typical risk factors for CHD (age, sex, hypertension, smoking, BMI >26 kg/m2, elevated low density lipoprotein cholesterol and haemoglobin A1c >7%) identified age >60, male gender, hypertension and a higher BMI, but not the PPARgamma-2 variants, as significant risk factors for CHD in our study groups.

CONCLUSION

The PPARgamma-2 genotype was not associated with an increased or reduced risk of the occurrence of CHD and can therefore not be regarded as an independent risk factor for CHD in patients with diabetes mellitus.

Relation between glycaemic control, hyperinsulinaemia and plasma concentrations of soluble adhesion molecules in patients with impaired glucose tolerance or Type II diabetes

AIMS/HYPOTHESIS

Increased plasma concentrations of circulating adhesion molecules in patients with Type II (non-insulin-dependent) diabetes mellitus could be associated with the increased cardiovascular risk in these patients. However, it is controversial whether increased adhesion molecule plasma concentrations are primarily related to hyperglycaemia or to hyperinsulinaemia.

METHODS

We evaluated the plasma concentrations of soluble E-selectin, intracellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) at baseline and during euglycaemic hyperinsulinaemic clamp in three different groups without additional cardiovascular risk factors: group A (control group), 28 healthy volunteers with normal glucose tolerance; group B, 24 subjects with fasting hyperinsulinaemia, normal fasting glucose but impaired glucose tolerance; group C, 32 patients with Type II diabetes, fasting hyperinsulinaemia and chronic hyperglycaemia.

RESULTS

Plasma soluble E-selectin, ICAM-1, and VCAM-1 concentrations were higher ( p < 0.05) in patients with Type II diabetes (group C) compared with the other groups. The adhesion molecule concentrations correlate with the fasting plasma glucose ( r = 0.59, p < 0.001), the 2-h OGTT plasma glucose ( r = 0.70, p < 0.01), and the HbA(1 c) value ( r = 0.61, p < 0.05). The E-selectin but not the ICAM-1 and VCAM-1 plasma concentrations correlated with the fasting insulin concentrations ( r = 0.62, p < 0.05) or the whole body glucose uptake ( r = 0.59, p < 0.05) in the clamp. The hyperinsulinaemia during the euglycaemic hyperinsulinaemic clamp had no significant effect on the plasma concentrations of E-selectin, ICAM-1, and VCAM-1 in all three groups.

CONCLUSION/INTERPRETATION

Our results suggest that increased E-selectin concentrations are related to hyperglycaemia, hyperinsulinaemia and insulin resistance, whereas increased ICAM-1 and VCAM-1 plasma concentrations in patients with Type II diabetes are rather related to hyperglycaemia than to hyperinsulinaemia or insulin resistance.

Influence of dietary intake and physical activity on annual rhythm of human blood cholesterol concentrations

Seasonal variation in the plasma total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) have been repeatedly reported, with contradictory results regarding the pattern of seasonal variation of these parameters. Furthermore, it is still not well established whether the variation is due to changes in the nutrition or changes in physical activity depending on the season. The aim of this study was therefore to determine plasma TC and HDL-C in different groups of healthy participants: 19 vegetarians with a constant diet independent of the season, 14 athletes with almost constant physical activity over the year, and 114 controls in the age groups 20-26 years (mean age 24 + 1.5 years) and 40-48 years (mean age 44.3 + 2.1 years). Over 2 years, blood samples were collected every 2-3 months and were analyzed for plasma TC and HDL-C. At all visits, body mass index (BMI) and waist-to-hip ratio (WHR) were calculated, and nutrition and physical activity profiles were obtained. The seasonal model was calculated using object-oriented software for the analysis of longitudinal data in S (OSWALD); multiple regression analysis was used to determine the influence of age, gender, diet, and physical activity on seasonal changes of the lipid parameters. In all groups, we found an annual rhythm of the plasma TC and HDL-C concentrations, which can be mathematically described by a sine curve with a maximum in winter and a minimum in summer. This rhythm was independent of the age, gender, BMI, diet, or physical activity. The observed seasonal differences between the maximum and the minimum were about 5%-10% for TC and about 5%-8% for HDL-C concentration. These differences were greater than the determined circadian (TC 3.5%, HDL-C 4%) and day-to-day changes for TC and HDL-C (coefficient of variation <5% for both). In conclusion, annual rhythm of TC and HDL-C is not primarily induced by seasonal differences in dietary intake or physical activity. Therefore, the annual rhythm in cholesterol levels is most likely determined by endogenous factors or factors directly related to seasonal changes in the environment.

Plasma levels of tumor necrosis factor-alpha, angiotensin II, growth hormone, and IGF-I are not elevated in insulin-resistant obese individuals with impaired glucose tolerance

OBJECTIVE

To investigate the relationship between insulin resistance and plasma concentrations of free fatty acids (FFAs), leptin, and potential agonists of the insulin receptor substrate (IRS) system, including tumor necrosis factor-alpha (TNF-alpha), IGF-I, growth hormone (GH), and angiotensin II in individuals with impaired glucose tolerance (IGT).

RESEARCH DESIGN AND METHODS

Because glucose toxicity per se leads to insulin resistance, the determination of the primary metabolic alterations leading to insulin resistance is best accomplished in individuals who are at an increased risk to develop type 2 diabetes. Therefore, 48 subjects with IGT and insulin resistance (IR), characterized by hyperinsulinemic-euglycemic clamps, were compared with 52 healthy insulin-sensitive (IS) control subjects with respect to the relationship between the plasma levels of TNF-alpha, IGF-I, GH, angiotensin II, FFA, leptin, and insulin resistance.

RESULTS

Between the IR and the IS groups, there were no significant differences in the plasma concentrations of TNF-alpha, GH, angiotensin II, IGF-I, and leptin. However, plasma FFA levels were significantly elevated in the IR group compared with the IS group after matching for BMI.

CONCLUSIONS

The plasma concentrations of FFA, but not TNF-alpha, IGF-I, GH, and angiotensin II, are elevated in patients at an early stage of insulin resistance, suggesting that FFAs, but not the other modulators of the IRS system, may be a primary metabolic abnormality leading to insulin resistance.

Fas and Fas ligand gene expression in autoimmune thyroiditis in BB/W rats

OBJECTIVE

Apoptosis via the Fas pathway is a potential mechanism for thyroid tissue destruction leading to clinical hypothyroidism in Hashimoto's thyroiditis (HT). Recent studies reported contradictory results regarding the regulation of Fas/Fas ligand (FasL) expression by cytokines in vitro. We therefore determined the Fas and FasL gene expression in the BioBreeding/Worcester (BB/W) rat thyroiditis model, which can be regarded as a model for HT.

METHODS

In order to obtain BB/W rats with spontaneous, iodine-induced or without lymphocytic thyroiditis (LT), rats were divided into 3 groups: 55-day-old rats after 24 days of iodine administration, 75-day-old rats after 45 days of iodine administration, and 101-day-old rats respectively. The gene expression of Fas, FasL, and interleukin (IL)-1beta was determined by Genescan fragment analysis using reverse polymerase chain reaction. Serum thyroglobulin (TG) antibody concentrations were measured and the extent of lymphocytic infiltration of one thyroid lobe was histologically graded.

RESULTS

Fas and FasL gene expression was significantly higher in rats with LT and correlated with the extent of lymphocytic infiltration and the TG antibody level. There was no evidence that the expression of IL-1beta or other cytokines is related to the expression of Fas or its ligand.

CONCLUSIONS

The increased expression of Fas and FasL in LT of BB/W rats suggests the involvement of the Fas pathway in the pathogenesis of LT in BB/W rats. However, in contrast to results of recent in vitro studies, in the BB/W rat Fas/FasL expression is not regulated by IL-2, -4, -6, -10, -12, interferon gamma, and tumor necrosis factor alpha.

Cytokine gene expression in autoimmune thyroiditis in BioBreeding/Worcester rats

The intrathyroidal cytokine gene expression in human autoimmune thyroid disease is difficult to interpret because surgical specimens mostly reflect the autoimmune disease at a late stage. Because it is not possible to investigate early stages of thyroiditis in humans, the Bio Breeding/Worcester (BB/W) rat was used as a model. To characterize the lymphocytic thyroiditis (LT) of BB/W rats further and to evaluate early increases of cytokine gene expression in LT, we investigated the interleukin (IL)-2, -4, -6, -10, -12p40, interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) gene expression in the thyroids, spleens, and livers of BB/W rats with and without histological evidence for thyroiditis. The gene expression of these cytokines was determined by Genescan (PE Applied Biosystems, Foster City, CA) fragment analysis using reverse polymerase chain reaction (RT-PCR). Serum thyroglobulin (Tg) antibody concentrations were measured and the extent of lymphocytic infiltration of one thyroid lobe was histologically graded. Cytokine gene expression in rats with and without LT was compared in three groups of rats: 55-day-old rats after 24 days of iodine administration, 75-day-old rats after 45 days of iodine administration, and 101-day-old rats. In the thyroids of the BB/W rats no expression of IL-4 or IL-10 was detectable. The number of rats with detectable TNF-alpha, IFN-gamma, IL-2, IL-12p40 gene expression was significantly higher in rats with LT. Rats with LT had significantly higher IL-12p40 mRNA levels. There were no significant differences in the IL-6 gene expression between rats with and without LT. A correlation between the level of lymphocytic infiltration and the TNF-alpha (r = 0.56, p < 0.0065) and TG antibody concentration (r = 0.62, p < 0.0065) was found. Therefore, the early cytokine gene expression in the BB/W rat is characterized by Th1-related cytokines like IL-2 and IFN-gamma. Whether the detected IL-12p40 (10 rats) and IFN-gamma (5 rats) gene expression in animals without LT is an early indicator for the development of LT remains to be determined.