Really does temperature reduction and norepinephrine have similar effects on the energy metabolism in rat brown adipose tissue?

CONTEXT: Heat generation by brown adipose tissue (BAT) in response to temperature reduction seems to be entirely related to sympathetic nervous stimulation. OBJECTIVE: To analyse if temperature reduction and norepinephrine may differently affect the expression of proteins related to energy metabolism in BAT. MATERIALS AND METHODS: Isolated rats BAT was incubated with/without norepinephrine (10-6 mol/L, 24 h at 32 °C and 37 °C). RESULTS: In BAT, 32 °C increased the protein expression levels of carnitine palmitoyltransferase-I and -II, mitochondrial uncoupling protein-1 (UCP-1) and the expression and activity of lactate dehydrogenase. Mitochondrial F1-ATP synthase α-chain expression was decreased at 32 °C compared to 37 °C. Norepinephrine and at 32 °C exposure, UCP-1 expression was increased but cytochrome-c oxidase and F1-ATP synthase α-chain expression was reduced with respect to 37 °C. DISCUSSION: Sympathetic stimulation seems not to be the only factor associated with heat generation. CONCLUSIONS: Temperature reduction by itself exerts some different effects on the expression of proteins related to the energy metabolism than norepinephrine.

Metabolic differences between white and brown fat from fasting rabbits at physiological temperature.

It has been suggested that activated brown adipose tissue (BAT) shows increased glucose metabolic activity. However, less is known about metabolic activity of BAT under conditions of fasting and normal temperature. The aim of this study was to compare the possible differences in energetic metabolism between BAT and white adipose tissue (WAT) obtained from rabbits under the conditions of physiological temperature and 24 h after fasting conditions. The study was carried out on New Zealand rabbits (n=10) maintained for a period of 8 weeks at 23±2 °C. Food was removed 24 h before BAT and WAT were obtained. Protein expression levels of the glycolytic-related protein, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate dehydrogenase were higher in WAT than that in BAT. The expression level of carnitine palmitoyltransferase 1 (CPT1) and CPT2, two fatty acid mitochondrial transporters, and the fatty acid ß-oxidation-related enzyme, acyl CoA dehydrogenase, was higher in BAT than in WAT. Cytosolic malate dehydrogenase expression and malate dehydrogenase activity were higher in WAT than in BAT. However, lactate dehydrogenase expression and lactate content were significantly higher in BAT than in WAT. In summary, this study for the first time, to our knowledge, has described how under fasting and normal temperature conditions rabbit BAT seems to use anaerobic metabolism to provide energetic fuel, as opposed to WAT, where the malate-aspartate shuttle and, therefore, the gluconeogenic pathway seem to be potentiated.

La plaqueta como célula inflamatoria: modificación de la expresión proteica del citoesqueleto y sistema contráctil de la pared vascular / The platelet as a inflammatory cell: modification of cytoskeletal and contractile protein expression of the vascular wall

A pesar de su sencillez estructural, las plaquetas son células funcionalmente muy complejas debido a su capacidad para producir y liberar biomoléculas. De aquí su importancia en el desarrollo de la arteriosclerosis. Se realizó un experimento in vitro para estudiar la actividad de las plaquetas sobre la pared vascular observando los cambios en la expresión proteica del citoesqueleto en segmentos de aorta bovina incubados con plasma rico en plaquetas. Para intentar simular un estado inflamatorio (arteriosclerosis), se realizaron estas mismas determinaciones en segmentos preestimulados con factor de necrosis tumoral. Se observó una modulación de la expresión de la mayoría de las proteínas del citoesqueleto en los segmentos de aorta sana. Sin embargo, en los segmentos preestimulados el número de proteínas fue menor, pudiendo reflejar una capacidad dual de las plaquetas para alterar la contractilidad vascular en función del estado inflamatorio de la pared vascular (AU)

Despite its structural simplicity, platelets are functionally complex cells due to their ability to produce and release biomolecules. Hence its importance in the development of atherosclerosis. An in vitro experiment was conducted to study the effect of the platelets on the vascular wall by observing changes in the cytoskeletal protein expression in bovine aortic segments incubated with platelet rich plasma. With the aim of simulating an inflammatory state (atherosclerosis), these same measurements were performed on aortic segments pre-stimulated with tumour necrosis factor. We observed a modulation of the expression of most of the cytoskeletal proteins in healthy aorta segments. However, the number of modified proteins was less in pre-stimulated segments. These results may reflect a dual platelet capacity to alter vascular contractility in relation to the inflammatory condition of the vascular wall (AU)

Increased cyclic guanosine monophosphate production and endothelial nitric oxide synthase level in mononuclear cells from sildenafil citrate-treated patients with erectile dysfunction.

Mononuclear cells express enzymes involved in the NO/cyclic guanosine monophosphate (cGMP) generating system, as well as PDE5. The objective of the study was to determine the effect of sildenafil citrate administration on the level of proteins involved in the NO/cGMP generating system in mononuclear cells from patients with ED. Twenty-one patients with ED (International Index of Erectile Function-Erectile Function Domain (IIEF-EFD) 17.9+/-0.8) were enrolled and 100 mg sildenafil citrate on-demand was administered during 12 weeks. All patients showed cardiovascular risk factors. After sildenafil citrate administration, IIEF-EFD score was improved (26+/-1.2 P<0.05). In the mononuclear cells, the protein level of endothelial NO synthase (eNOS) was higher after sildenafil citrate treatment. It was accompanied by reduction in the circulating plasma levels of both high-sensitive C-reactive protein and soluble intercellular adhesive molecule-1. The protein level of soluble guanylate cyclase and PDE5 did not change in the mononuclear cells after sildenafil citrate treatment. However, in the mononuclear cells exogenous NO induced a higher cGMP production after 12-weeks sildenafil citrate administration. In conclusion, in mononuclear cells from patients with ED sildenafil citrate administration increased the level of eNOS protein and increased cGMP production in response to NO. Moreover, sildenafil citrate administration reduced the plasma circulating levels of two biomarkers associated with inflammation.

Soluble guanylate cyclase beta1-subunit expression is increased in mononuclear cells from patients with erectile dysfunction.

The aim was to determine in circulating mononuclear cells from patients with erectile dysfunction (ED), the level of expression of endothelial nitric oxide synthase (eNOS), soluble guanylate cyclase (sGC) beta1-subunit and phosphodiesterase type-V (PDE-V). Peripheral mononuclear cells from nine patients with ED of vascular origin and nine patients with ED of neurological origin were obtained. Fourteen age-matched volunteers with normal erectile function were used as control. Reduction in eNOS protein was observed in the mononuclear cells from patients with ED of vascular origin but not in those from neurological origin. Although sGC beta1-subunit expression was increased in mononuclear cells from patients with ED, the sGC activity was reduced. However, only the patients with ED of vascular origin showed an increased expression of PDE-V. This work shows for the first time that, independently of the aetiology of ED, the expression of sGC beta1-subunit was increased in circulating mononuclear cells; however, the expression of both eNOS and PDE-V was only modified in the circulating mononuclear cells from patients with ED of vascular origin.

Involvement of endothelium and endothelin-1 in lead-induced smooth muscle cell dysfunction in rats.

Lead exposure induces dysfunction of the cyclic guanosine monophosphate-dependent vasodilator system through downregulation of soluble guanylate cyclase (sGC) expression. The endothelium not only releases vasodilators but also vasoconstrictors such as endothelin-1 (ET-1). Our aim was to explore the role of the vascular endothelium and ET-1 as possible mediators of lead-induced downregulation of sGC. Isolated aortic segments from Wistar Kyoto rats were incubated in the presence or absence of lead (1 parts per million) for 24 h. Endothelium was mechanically removed in some of the aorta segments. As reported previously, lead exposure induced downregulation of sGC protein expression in the intact aortic segments. However, lead exposure failed to significantly modify sGC-beta1 subunit expression in the endothelium-denuded aortic segments. Incubation with a selective ETA-type receptor inhibitor, BQ-123 (10(-6) mol/l), restored sGC protein expression in lead-exposed intact aortic segments. As it has also been previously observed, incubation in lead-containing medium resulted in the upregulation of cyclooxygenase-2 (COX-2) in the intact aortic segments. Denudation of endothelium partially abrogated this effect of lead. Incubation with BQ-123 prevented the lead-induced upregulation COX-2 in the intact aortic segments. However, neither ET-1 content nor ETA-type receptor expression were modified by lead exposure of the aortic segments. As conclusion, the endothelium through the activation of ETA-type receptors mediates the downregulation of sGC expression by lead in the vascular wall.

Role of nitric oxide-related mechanisms in renal function in ageing rats.

BACKGROUND: The impaired renal function and vasodilatation that accompany age need to be re-addressed based upon the new knowledge concerning vascular nitric oxide (NO)-dependent systems. The present study examined the effects of age on the NO-related renal response. METHODS: The study was performed in euvolaemic, conscious Wistar rats, aged 5 and 18 months. Renal function and haemodynamic measurements with fluorescent microspheres were employed to assess differences between groups. RESULTS: A first set of experiments showed that ageing rats had a reduced natriuretic and diuretic response to acetylcholine, whereas the response to sodium nitroprusside was preserved. In the same regard, a reduction of the renal functional effects of L-arginine (L-Arg) and L-glycine (L-Gly) was found in the older rats. In the ageing rats, these responses were accompanied by an enhanced effect of the L-Arg competitive analogue, NwNLA, which provoked a marked reduction of renal function. This effect of NwNLA was blocked by the simultaneous administration of a small dose of L-Arg in the ageing but not in the young rats. Systemic haemodynamic studies revealed that in ageing rats, NwNLA reduced renal blood flow and increased renal vascular resistances in a significantly higher proportion than in younger animals. However, flow to other organs, namely, brain, spleen or liver, was affected in a similar manner in both young and old rats. Ultrastructural alterations were found in endothelial cells, which might constitute the anatomical basis for the observed functional derangements. CONCLUSIONS: The present experiments reveal that ageing is accompanied by significant differences in NO-related responses in the kidney which do not appear to affect blood flow to other organs. The response to L-Arg and L-Arg competitive analogues supports the existence of a marked dependency on NO-related mechanisms in the ageing rats, but not of a decreased baseline activity of the NO-dependent pathways.

Mechanisms of aluminum-induced microcytosis: lessons from accidental aluminum intoxication.

Twenty-three hemodialysis patients exposed to an accidental aluminum overload, showed increased erythropoietin requirements and decreased erythrocyte mean corpuscular volume (MCV). At the peak of the intoxication, MCV and plasma aluminum levels changed from unrelated (r = 0.02) to strongly related (r = 0.425) variables. The molar proportion of plasma aluminum to plasma iron increased dramatically (from 1:13.8 to 1:2.4). This significant increment in the aluminum/iron ratio made higher the relative offer of aluminum with respect to iron to the erythroid precursor cells. Accordingly, in a subset of 13 randomly selected aluminum-intoxicated patients we found increased intraerythrocytic aluminum, which paralleled the increase in plasma aluminum. Furthermore, in the aluminum-intoxicated group, intraerythrocytic ferritin, a marker of iron content, and the ratio between erythrocyte and plasma ferritin were lower (P < 0.01 and < 0.001, respectively), than in the control group. These findings support the hypothesis that in some cases of aluminum-related microcytosis, a ferropenic mycrocitosis, as expression of erythroid ferropenia, may exist in spite of the presence of normal body iron stores.

Mechanisms of the endothelial toxicity of cyclosporin A. Role of nitric oxide, cGMP, and Ca2+.

Cyclosporin A (CyA) is an efficient immunosuppressive agent, which, however, causes functional and structural alterations in endothelial cells. The aim of the present study was to examine the mechanisms of CyA-induced endothelial disfunction. CyA administration (Wistar rats, 25 mg/kg per day for 15 days) induced a significant inhibition of endothelium-dependent relaxation to acetylcholine on isolated femoral arteries. No changes with CyA were detected in the relaxation response to the endothelium-independent agent (sodium nitroprusside) or the endothelium-dependent receptor-independent agent (Ca2+ ionophore). The addition of L-arginine (10(-5) mol/L) shifted to the left the acetylcholine-mediated vasorelaxing response in CyA-treated segments, an effect that was accompanied by a marked increase of cGMP. 45Ca2+ uptake was higher in CyA-treated segments with respect to control segments but became normalized after incubation with L-arginine or sodium nitroprusside. De-endothelialization or incubation with the L-arginine competitive analogue N omega-nitro-L-arginine (NwNLA) increased 45Ca2+ uptake in control segments but not in CyA-treated segments. In conclusion, in isolated rat arteries, chronic CyA therapy affects endothelial function by uncoupling the acetylcholine-mediated relaxation and interfering with an endothelium-mediated pathway that regulates 45Ca2+ uptake by a mechanism reversed by an L-arginine-dependent cGMP generation.