Adenoviral vector-mediated glucagon-like peptide 1 gene therapy improves glucose homeostasis in Zucker diabetic fatty rats.

BACKGROUND: Glucagon-like peptide-1 (GLP-1) is a gut-derived incretin hormone that plays an important role in glucose homeostasis. Its functions include glucose-stimulated insulin secretion, suppression of glucagon secretion, deceleration of gastric emptying, and reduction in appetite and food intake. Despite the numerous antidiabetic properties of GLP-1, its therapeutic potential is limited by its short biological half-life due to rapid enzymatic degradation by dipeptidyl peptidase IV. The present study aimed to demonstrate the therapeutic effects of constitutively expressed GLP-1 in an overt type 2 diabetic animal model using an adenoviral vector system. METHODS: A novel plasmid (pAAV-ILGLP-1) and recombinant adenoviral vector (Ad-ILGLP-1) were constructed with the cytomegalovirus promoter and insulin leader sequence followed by GLP-1(7-37) cDNA. RESULTS: The results of an enzyme-linked immunosorbent assay showed significantly elevated levels of GLP-1(7-37) secreted by human embryonic kidney cells transfected with the construct containing the leader sequence. A single intravenous administration of Ad-ILGLP-1 into 12-week-old Zucker diabetic fatty (ZDF) rats, which have overt type 2 diabetes mellitus (T2DM), achieved near normoglycemia for 3 weeks and improved utilization of blood glucose in glucose tolerance tests. Circulating plasma levels of GLP-1 increased in GLP-1-treated ZDF rats, but diminished 21 days after treatment. When compared with controls, Ad-ILGLP-1-treated ZDF rats had a lower homeostasis model assessment for insulin resistance score indicating amelioration in insulin resistance. Immunohistochemical staining showed that cells expressing GLP-1 were found in the livers of GLP-1-treated ZDF rats. CONCLUSIONS: These data suggest that GLP-1 gene therapy can improve glucose homeostasis in fully developed diabetic animal models and may be a promising treatment modality for T2DM in humans.

Effect of capsaicin on cholecystokinin and neuropeptide Y expressions in the brain of high-fat diet fed rats.

Capsaicin, one of the pungent principles of hot pepper, has been reported to cause a cessation of increases in body weight and fat gain induced by high-fat feeding. Especially, in body weight and feeding control, cholecystokinin (CCK) has been well known as a satiety signal and neuropeptide Y (NPY) has been described as one of the most potent orexigenic signals. This study was carried out to investigate the effect of capsaicin on CCK- and NPY- immunoreactivities (IR) in the brain of high-fat fed rats. The animals were divided into normal-fat diet (NF), high-fat diet (HF) and high-fat diet containing capsaicin (HF-CAP) groups. Mean body weight gain (MBWG) of HF group was higher than that of NF group. However, in HF-CAP group, MBWG was lower than that of HF group. CCK-IR in suprachiasmatic nucleus (SCN), paraventricular nucleus (PVN), median eminence (ME), arcuate nucleus (ARC) and amygdala was not prominent in all the groups. In cerebral cortex, CCK-IR was more reduced in HF-CAP group than in the other groups. In the HF-CAP group, NPY-IR in the hypothalamic nuclei, amygdala and cerebral cortex was more poorly found than in the NF and HF groups. It is concluded that (1) NPY-IR may react more sensitively on capsaicin than CCK-IR, (2) no rapid increase of body weight in capsaicin treated rats may result from the diminished food intake through the low expression of NPY in hypothalamus in HF-CAP group.

Protective effects of N-acetylcysteine and selenium against doxorubicin toxicity in rats.

To investigate the neutralizing effect of N-acetylcysteine (NAC) and selenium (Se) against doxorubicin (DOX) toxicity in rats, NAC (140 mg/kg, p.o.) and Se (0.5 mg/kg, p.o.) were administered for 2 days before DOX injection and then 3 times a week. Cell viability and the level of lipid peroxidation were examined in cultured-rat astrocytes. Severe morphologic changes in the kidney of DOX group; thickening of Bowmans capsule, presence of multifocal tubular casts were observed, but not in the other treated groups. Vacuoles in some hepatic cells and focal aggregation of stellate macrophages were also detected in DOX group, but not in the other treated groups. However, the severe inhibition of spermatogenesis was found in all treated groups. The cell viability of DOX (10 mg/ml) treated group and NAC (5 mM) or Se (0.001 mg/ml) combined-treated group was 52.5-/+2.0 %, 85.3-/+4.5 % and 75.5-/+1.6 %, respectively. In MDA (malondialdehyde) assay, the level of lipid peroxidation on DOX (10 mg/ml), NAC (5 mM) and Se (0.001 mg/ml) was 0.77-/+0.06, 0.35-/+0.06 and 0.54-/+0.11 nmol/mg protein, respectively. Thus, it is known that NAC and Se have protective effects in kidney and liver but not in the testes. Morphological change was not detected in brain and heart in all groups for experiment period. From this in vitro study, it is known that NAC and Se protect well the astrocytes against DOX induced-cell damage.