Lina Åkesson

Increased GABA(A) channel subunits expression in CD8(+) but not in CD4(+) T cells in BB rats developing diabetes compared to their congenic littermates.

GABA (γ-aminobutyric acid), the main inhibitory neurotransmitter in the central nervous system is also present in the pancreatic islet β cells where it may function as a paracrine molecule and perhaps as an immunomodulator of lymphocytes infiltrating the pancreatic islet. We examined CD4(+) and CD8(+) T cells from diabetes prone (DR(lyp/lyp)) or resistant (DR(+/+)) congenic biobreeding (BB) rats for expression of GABA(A) channels. Our results show that BB rat CD4(+) and CD8(+) T cells express α1, α2, α3, α4, α6, β3, γ1, δ, ρ1 and ρ2 GABA(A) channel subunits. In CD8(+) T cells from DR(lyp/lyp) animals the subunits were significantly upregulated relative to expression levels in the CD8(+) T cells from DR(+/+) rats as well as from CD4(+) T cells from both DR(lyp/lyp) and DR(+/+) rats. Functional channels were formed in the T cells and physiological concentrations of GABA (100 nM) decreased T cell proliferation. Our results are consistent with the hypothesis that GABA in the islets of Langerhans may diminish inflammation by inhibition of activated T lymphocytes.

Animal Models of Diabetic Macrovascular Complications: Key Players in the Development of New Therapeutic Approaches

Diabetes mellitus is a lifelong, incapacitating metabolic disease associated with chronic macrovascular complications (coronary heart disease, stroke, and peripheral vascular disease) and microvascular disorders leading to damage of the kidneys (nephropathy) and eyes (retinopathy). Based on the current trends, the rising prevalence of diabetes worldwide will lead to increased cardiovascular morbidity and mortality. Therefore, novel means to prevent and treat these complications are needed. Under the auspices of the IMI (Innovative Medicines Initiative), the SUMMIT (SUrrogate markers for Micro- and Macrovascular hard end points for Innovative diabetes Tools) consortium is working on the development of novel animal models that better replicate vascular complications of diabetes and on the characterization of the available models. In the past years, with the high level of genomic information available and more advanced molecular tools, a very large number of models has been created. Selecting the right model for a specific study is not a trivial task and will have an impact on the study results and their interpretation. This review gathers information on the available experimental animal models of diabetic macrovascular complications and evaluates their pros and cons for research purposes as well as for drug development.

Increased Lipid Oxidation Heralds Diabetes Onset in DR.lyp/lyp Rats.

AIM The BB rat model of type 1 diabetes exhibits altered body weight gain and body temperature regulation prior to hyperglycemia onset, implying the existence of as yet unidentified biomarkers of autoimmune processes that destroy pancreatic beta cells. To investigate this hypothesis, we compared the metabolic profile of diabetes-resistant DR.lyp/+ rats and their diabetes-prone, congenic DR.lyp/lyp littermates in the days leading up to diabetes onset. METHODS Except for the Gimap5 mutation on chromosome 4, congenic DR.lyp/lyp rats are genetically identical to DR.lyp/+ littermates. They invariably develop hyperglycemia at 46-81 days of age, whereas DR.lyp/+ rats do not develop diabetes. In addition to daily food intake and body weight, indirect calorimetry was performed continuously on male DR.lyp/lyp and DR.lyp/+ rats (n=6/group) for 6-18 days to measure locomotor activity, VO (2), VCO (2) and RQ. RESULTS DR.lyp/lyp rats exhibited a progressive decrease of RQ compared to DR.lyp/+ rats 0.005+/-0.001 units/day (p<0.005). Limiting the analysis to the six days prior to diabetes onset revealed a larger decrease of 0.007+/-0.002 units/day (p<0.001) in DR.lyp/lyp animals, whereas RQ of the DR.lyp/+ rats remained unchanged. This metabolic change occurred prior to hyperglycemia onset and was not associated with changes of any other parameter. CONCLUSIONS Diabetes onset in DR.lyp/lyp rats is heralded by a progressive shift towards lipid oxidation relative to carbohydrate metabolism.

Longitudinal analysis of hepatic transcriptome and serum metabolome demonstrates altered lipid metabolism following the onset of hyperglycemia in spontaneously diabetic BioBreeding rats

Type 1 diabetes is associated with abberations of fat metabolism before and after the clinical onset of disease. It has been hypothesized that the absence of the effect of insulin in the liver contributes to reduced hepatic fat synthesis. We measured hepatic gene expression and serum metabolites before and after the onset of hyperglycemia in a BioBreeding rat model of type 1 diabetes. Functional pathway annotation identified that lipid metabolism was differentially expressed in hyperglycemic rats and that these pathways significantly overlapped with genes regulated by insulin. 17 serum metabolites significantly changed in concentration. All but 2 of the identified metabolites had previously been reported in type 1 diabetes, and carbohydrates were overall the most upregulated class of metabolites. We conclude that lack of insulin in the liver contributes to the changes in fat metabolism observed in type 1 diabetes. Further studies are needed to understand the clinical consequences of a lack of insulin in the liver in patients with type 1 diabetes.

Immunohistochemical analysis of cannabinoid receptor 1 expression in steatotic rat livers

The primary aim of the present study was to determine the expression levels of cannabinoid receptor type 1 (CB1) in steatotic rat livers. The secondary aim was to clarify whether steatosis and inflammation are more marked in areas with increased CB1 overexpression. For ethical and economic reasons, the present study investigated tissue from archived liver blocks, which were obtained from 38 rats that had been euthanized during the course of previous research at the Karolinska Institute of the Karolinska University Hospital (Stockholm, Sweden) and Lund University (Malmö, Sweden). Liver tissue fixed in formalin and embedded in paraffin was used that had been sourced from 36 male Sprague Dawley rats (age, 7 weeks) and 2 rats (age, 180 days) lacking normal leptin receptors. The rat liver tissue was stained with antibodies against CB1 and counterstained with hematoxylin. The expression of CB1 and the number of cells overexpressing CB1 were determined. Steatosis was scored according to the Dixon scoring system. CB1 overexpression and steatosis were detected in hepatocytes from all 38 livers sampled. The expression of CB1 was more marked in hepatocytes localized next to portal triads. Near the central veins, the expression was significantly weaker. Steatosis was more marked in areas of increased CB1 overexpression. Lymphocyte infiltration was more commonly observed in areas of increased CB1 overexpression. Therefore, the present results indicate that CB1 receptors are overexpressed in areas with steatosis, and indicate that CB1 in hepatocytes contributes to the formation of steatosis in rats, even prior to its progression to steatohepatitis. These results are consistent with publications reporting that CB1 in hepatocytes increases lipogenesis and contributes to inflammation.