At indicated time points (A). VLDL-TG production rate was calculated from

At indicated time points (A). VLDL-TG production rate was calculated from the slopes of the individual TG-time graphs (B). At t = 120 min, mice were exsanguinated and VLDL fractions were isolated from serum by ultracentrifugation. 35S-apoB production was determined by scintillation counting of the isolated VLDL fraction (C). Values are means 6 SD (n = 8210). doi:10.1371/journal.pone.0055217.gCentral NPY and Hepatic VLDL Production in Micebetween the VLDL-TG production rate in controls (6.260.5 mmol/h) and that in mice treated with NPY (6.960.1, 6.260.1, 6.960.3, 6.860.5 or 6.960.5 mmol/h at 0.0002, 0.002, 0.02, 0.2 or 2.0 mg/kg BW, respectively, n.s., Fig. S1). Since the use of anesthetics theoretically could interfere with the modulation of central NPY signaling, we repeated the experiment in conscious mice. However, NPY (0.2 mg/kg BW) did not Human parathyroid hormone-(1-34) biological activity increase hepatic VLDL-TG or VLDL-apoB production in conscious mice (data not shown).Antagonizing Central NPY Signaling does not Affect Hepatic VLDL ProductionSince other modulators of NPY signaling have previously been shown to acutely interfere with VLDL-TG production in rats [12], we next assessed the effects of PYY3?6 and of GR231118, a synthetic Y1 receptor antagonist, on hepatic VLDL-TG and VLDL-apoB production. Central administration of GR231118 did not affect the hepatic 16985061 production of VLDL-TG (8.661.8 vs 8.761.4 mmol/h, n.s., Fig. 3A,B) or VLDL-apoB (55611 vs 5969 6103 dpm/h, n.s., Fig. 3C). In line with this finding, intravenous administration of PYY3?6, the endogenous antagonist of NPY, was also ineffective in lowering the hepatic production of VLDLTG (8.560.9 vs 7.560.9 mmol/h, n.s., Fig. 3D,E) and VLDLapoB (73618 vs 756136103 dpm/h, n.s., Fig. 3F).Third Ventricle NPY Administration Stimulates Food Intake in MiceIn contrast to the LV, the third ventricle (3V) is located at the base of the hypothalamus, the brain area that mediates NPYinduced feeding. To exclude that the absence of effect of modulation of central NPY signaling was due to LV versus 3V injection, we next performed 3V cannulations in mice. We first assessed the effects of 3V NPY (0.2 mg/kg BW) on food intake. NPY increased food intake during the first hour after POR8 cost injection by +367 (0.2160.08 vs 0.9860.44 g, p,0.001) as well as during the second hour after injection by +105 (0.2260.11 vs 0.4560.19, p,0.05) (Fig. 4).Third Ventricle NPY Administration does not Affect Hepatic VLDL-TG ProductionAlbeit that administration of NPY into the 3V also potently increased food intake, NPY (0.2 mg/kg BW) was still unable to increase hepatic VLDL production in conscious mice, as both the hepatic production rate of VLDL-TG (6.560.6 vs 6.060.9 mmol/ h, n.s., Fig. 5A,B) and VLDL-apoB (2263 vs 2262 6103 dpm/h, n.s., Fig. 5C) were unchanged. Collectively, these data thus show that acute modulation of central NPY signaling does not affect hepatic VLDL production in mice.DiscussionSince modulation of central NPY signaling acutely increases VLDL-TG production in rats, we initially set out to investigate the acute effects of central NPY administration on VLDL-TG production in mice, ultimately aimed at investigating the contribution of central NPY, by modulating VLDL production, to the development of atherosclerosis. We confirmed that central administration of NPY acutely increases food intake in mice, similarly as in rats. In contrast to the effects in rats, central administration of a wide dose range of NPY was unable to increase VLDL-TG producti.At indicated time points (A). VLDL-TG production rate was calculated from the slopes of the individual TG-time graphs (B). At t = 120 min, mice were exsanguinated and VLDL fractions were isolated from serum by ultracentrifugation. 35S-apoB production was determined by scintillation counting of the isolated VLDL fraction (C). Values are means 6 SD (n = 8210). doi:10.1371/journal.pone.0055217.gCentral NPY and Hepatic VLDL Production in Micebetween the VLDL-TG production rate in controls (6.260.5 mmol/h) and that in mice treated with NPY (6.960.1, 6.260.1, 6.960.3, 6.860.5 or 6.960.5 mmol/h at 0.0002, 0.002, 0.02, 0.2 or 2.0 mg/kg BW, respectively, n.s., Fig. S1). Since the use of anesthetics theoretically could interfere with the modulation of central NPY signaling, we repeated the experiment in conscious mice. However, NPY (0.2 mg/kg BW) did not increase hepatic VLDL-TG or VLDL-apoB production in conscious mice (data not shown).Antagonizing Central NPY Signaling does not Affect Hepatic VLDL ProductionSince other modulators of NPY signaling have previously been shown to acutely interfere with VLDL-TG production in rats [12], we next assessed the effects of PYY3?6 and of GR231118, a synthetic Y1 receptor antagonist, on hepatic VLDL-TG and VLDL-apoB production. Central administration of GR231118 did not affect the hepatic 16985061 production of VLDL-TG (8.661.8 vs 8.761.4 mmol/h, n.s., Fig. 3A,B) or VLDL-apoB (55611 vs 5969 6103 dpm/h, n.s., Fig. 3C). In line with this finding, intravenous administration of PYY3?6, the endogenous antagonist of NPY, was also ineffective in lowering the hepatic production of VLDLTG (8.560.9 vs 7.560.9 mmol/h, n.s., Fig. 3D,E) and VLDLapoB (73618 vs 756136103 dpm/h, n.s., Fig. 3F).Third Ventricle NPY Administration Stimulates Food Intake in MiceIn contrast to the LV, the third ventricle (3V) is located at the base of the hypothalamus, the brain area that mediates NPYinduced feeding. To exclude that the absence of effect of modulation of central NPY signaling was due to LV versus 3V injection, we next performed 3V cannulations in mice. We first assessed the effects of 3V NPY (0.2 mg/kg BW) on food intake. NPY increased food intake during the first hour after injection by +367 (0.2160.08 vs 0.9860.44 g, p,0.001) as well as during the second hour after injection by +105 (0.2260.11 vs 0.4560.19, p,0.05) (Fig. 4).Third Ventricle NPY Administration does not Affect Hepatic VLDL-TG ProductionAlbeit that administration of NPY into the 3V also potently increased food intake, NPY (0.2 mg/kg BW) was still unable to increase hepatic VLDL production in conscious mice, as both the hepatic production rate of VLDL-TG (6.560.6 vs 6.060.9 mmol/ h, n.s., Fig. 5A,B) and VLDL-apoB (2263 vs 2262 6103 dpm/h, n.s., Fig. 5C) were unchanged. Collectively, these data thus show that acute modulation of central NPY signaling does not affect hepatic VLDL production in mice.DiscussionSince modulation of central NPY signaling acutely increases VLDL-TG production in rats, we initially set out to investigate the acute effects of central NPY administration on VLDL-TG production in mice, ultimately aimed at investigating the contribution of central NPY, by modulating VLDL production, to the development of atherosclerosis. We confirmed that central administration of NPY acutely increases food intake in mice, similarly as in rats. In contrast to the effects in rats, central administration of a wide dose range of NPY was unable to increase VLDL-TG producti.