l-Arginine supplementation induces glutathione synthesis in interscapular brown adipose tissue through activation of glutamate-cysteine ligase expression: The role of nitric oxide.

We examined whether nitric oxide (NO) in vivo could induce interscapular brown adipose tissue (IBAT) glutathione synthesis. Data show that NO induces in vivo IBAT glutathione synthesis through activation of glutamate-cysteine ligase (GCL) mRNA and protein expression. This NO effect appeared to be mediated by nuclear factor-kappaB (NF-kappaB) activation. We have also observed a complex series of in vivo cellular responses during chronic inhibition of NO synthesis, suggesting that regulatory pathways unrelated to GCL alteration underlie glutathione level increase induced by N(omega)-nitro-l-arginine methyl ester (l-NAME). In general, glutathione synthesis in IBAT seemed to be finely tuned by NO to provide glutathione for either mediating the effects of NO, or for preventing potential nitrosative stress.

Beneficial effects of L-arginine nitric oxide-producing pathway in rats treated with alloxan.

In an attempt to elucidate molecular mechanisms and factors involved in beta cell regeneration, we evaluated a possible role of the L-arginine-nitric oxide (NO)-producing pathway in alloxan-induced diabetes mellitus. Diabetes was induced in male Mill Hill rats with a single alloxan dose (120 mg kg(-1)). Both non-diabetic and diabetic groups were additionally separated into three subgroups: (i) receiving L-arginine . HCl (2.25%), (ii) receiving L-NAME . HCl (0.01%) for 12 days as drinking liquids, and (iii) control. Treatment of diabetic animals started after diabetes induction (glucose level > or = 12 mmol l(-1)). We found that disturbed glucose homeostasis, i.e. blood insulin and glucose levels in diabetic rats was restored after L-arginine treatment. Immunohistochemical findings revealed that L-arginine had a favourable effect on beta cell neogenesis, i.e. it increased the area of insulin-immunopositive cells. Moreover, confocal microscopy showed colocalization of insulin and pancreas duodenum homeobox-1 (PDX-1) in both endocrine and exocrine pancreas. This increase in insulin-expressing cells was accompanied by increased cell proliferation (observed by proliferating cell nuclear antigen-PCNA immunopositivity) which occurred in a regulated manner since it was associated with increased apoptosis (detected by the TUNEL method). Furthermore, L-arginine enhanced both nuclear factor-kB (NF-kB) and neuronal nitric oxide synthase (nNOS) immunopositivities. The effect of L-arginine on antioxidative defence was observed especially in restoring to control level the diabetes-induced increase in glutathione peroxidase activity. In contrast to L-arginine, diabetic pancreas was not affected by L-NAME supplementation. In conclusion, the results suggest beneficial L-arginine effects on alloxan-induced diabetes resulting from the stimulation of beta cell neogenesis, including complex mechanisms of transcriptional and redox regulation.

The effects of cold acclimation and nitric oxide on antioxidative enzymes in rat pancreas.

Alterations of pancreatic antioxidative defense (AD) and possible nitric oxide (NO) role in AD organization of adult rats receiving l-arginine.HCl (2.25%) or N(omega)-nitro-l-arginine methyl ester (L-NAME.HCl, 0.01%) as drinking liquids and maintained at room (22+/-1 degrees C) or low (4+/-1 degrees C) temperature for 45 days were studied. For that purpose, copper, zinc- and manganese superoxide dismutase (CuZnSOD, MnSOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST) and glutathione reductase (GR) activities were determined. Cold-induced decrease of CuZnSOD was inhibited with L-NAME, while l-arginine produced the same effect as cold in both supplemented groups. Cold acclimation elevated GSH-Px activity. l-Arginine and L-NAME expressed no effect on GSH-Px in rats kept at room temperature. L-NAME additionally elevated cold-induced GSH-Px activity, l-arginine expressing a similar trend. Cold-induced increase in GST activity was inhibited by L-NAME, while l-arginine inhibited this enzyme in both supplemented groups. Cold acclimation increased GR activity in control and L-NAME-treated group and l-arginine expressed a similar trend. Neither of the treatments affected MnSOD and CAT activities. Cold-induced changes of pancreatic AD were additionally affected by the alterations in l-arginine-NO-producing pathway. Some AD changes in the same direction with l-arginine or L-NAME point to the complexity of nitrogen compounds metabolism and function, accompanied by tissue-specific response.

The effects of L-arginine and L-NAME supplementation on redox-regulation and thermogenesis in interscapular brown adipose tissue.

Changes in inducible nitric oxide synthase (iNOS) protein levels and its relationship with the hyperplasia and uncoupling protein 1 (UCP1) levels were examined in interscapular brown adipose tissue (IBAT) of adult rat males receiving L-arginine (L-Arg; 2.25%) or N-nitro-L-arginine methyl ester (L-NAME; 0.01%) as a drinking liquid and maintained at low (4+/-1 degrees C) or room (22+/-1 degrees C) temperature for 45 days. Cold generally diminished both iNOS immunopositivity and protein level in IBAT, as well as the rate of apoptosis. Among groups acclimated to cold, higher iNOS immunopositivity and protein levels were detected only in the L-Arg-treated group. Furthermore, chronic L-Arg treatment increased IBAT mass and UCP1 protein content, while L-NAME had an opposite effect, decreasing both IBAT mass and UCP1 protein level, as compared to the control maintained at 4+/-1 degrees C. These data suggest that nitric oxide (NO) produced by iNOS could also contribute to overall NO-associated regulation of thermogenesis in IBAT. Namely, that iNOS, i.e. NO, in correlation with enhanced thermogenesis, additionally induced IBAT hyperplasia and UCP1 level compared to that induced by low temperature. Cooperative action of decreased apoptosis accompanied by increased tissue hyperplasia and UCP1 level, observed in IBAT of cold-acclimated rats, would be a way of meeting the metabolic requirements for increased thermogenesis.