table_1_Daily Gene Expression Rhythms in Rat White Adipose Tissue Do Not Differ Between Subcutaneous and Intra-Abdominal Depots.PDF

<p>White adipose tissue (WAT) is present in different depots throughout the body. Although all depots are exposed to systemic humoral signals, they are not functionally identical. Studies in clock gene knockout animals and in shift workers suggest that daily rhythmicity may play an important role in lipid metabolism. Differences in rhythmicity between fat depots might explain differences in depot function; therefore, we measured mRNA expression of clock genes and metabolic genes on a 3-h interval over a 24-h period in the subcutaneous inguinal depot and in the intra-abdominal perirenal, epididymal, and mesenteric depots of male Wistar rats. We analyzed rhythmicity using CircWave software. Additionally, we measured plasma concentrations of glucose, insulin, corticosterone, and leptin. The clock genes (Bmal1/Per2/Cry1/Cry2/RevErbα/DBP) showed robust daily gene expression rhythms, which did not vary between WAT depots. Metabolic gene expression rhythms (SREBP1c/PPARα/PPARγ/FAS/LPL/Glut4/HSL/CPT1b/leptin/visfatin/resistin) were more variable between depots. However, no distinct differences between intra-abdominal and subcutaneous rhythms were found. Concluding, specific fat depots are not associated with differences in clock gene expression rhythms and, therefore, do not provide a likely explanation for the differences in metabolic function between different fat depots.</p

image_2_Daily Gene Expression Rhythms in Rat White Adipose Tissue Do Not Differ Between Subcutaneous and Intra-Abdominal Depots.PDF

<p>White adipose tissue (WAT) is present in different depots throughout the body. Although all depots are exposed to systemic humoral signals, they are not functionally identical. Studies in clock gene knockout animals and in shift workers suggest that daily rhythmicity may play an important role in lipid metabolism. Differences in rhythmicity between fat depots might explain differences in depot function; therefore, we measured mRNA expression of clock genes and metabolic genes on a 3-h interval over a 24-h period in the subcutaneous inguinal depot and in the intra-abdominal perirenal, epididymal, and mesenteric depots of male Wistar rats. We analyzed rhythmicity using CircWave software. Additionally, we measured plasma concentrations of glucose, insulin, corticosterone, and leptin. The clock genes (Bmal1/Per2/Cry1/Cry2/RevErbα/DBP) showed robust daily gene expression rhythms, which did not vary between WAT depots. Metabolic gene expression rhythms (SREBP1c/PPARα/PPARγ/FAS/LPL/Glut4/HSL/CPT1b/leptin/visfatin/resistin) were more variable between depots. However, no distinct differences between intra-abdominal and subcutaneous rhythms were found. Concluding, specific fat depots are not associated with differences in clock gene expression rhythms and, therefore, do not provide a likely explanation for the differences in metabolic function between different fat depots.</p

image_1_Daily Gene Expression Rhythms in Rat White Adipose Tissue Do Not Differ Between Subcutaneous and Intra-Abdominal Depots.PDF

<p>White adipose tissue (WAT) is present in different depots throughout the body. Although all depots are exposed to systemic humoral signals, they are not functionally identical. Studies in clock gene knockout animals and in shift workers suggest that daily rhythmicity may play an important role in lipid metabolism. Differences in rhythmicity between fat depots might explain differences in depot function; therefore, we measured mRNA expression of clock genes and metabolic genes on a 3-h interval over a 24-h period in the subcutaneous inguinal depot and in the intra-abdominal perirenal, epididymal, and mesenteric depots of male Wistar rats. We analyzed rhythmicity using CircWave software. Additionally, we measured plasma concentrations of glucose, insulin, corticosterone, and leptin. The clock genes (Bmal1/Per2/Cry1/Cry2/RevErbα/DBP) showed robust daily gene expression rhythms, which did not vary between WAT depots. Metabolic gene expression rhythms (SREBP1c/PPARα/PPARγ/FAS/LPL/Glut4/HSL/CPT1b/leptin/visfatin/resistin) were more variable between depots. However, no distinct differences between intra-abdominal and subcutaneous rhythms were found. Concluding, specific fat depots are not associated with differences in clock gene expression rhythms and, therefore, do not provide a likely explanation for the differences in metabolic function between different fat depots.</p

Acute Peripheral but Not Central Administration of Olanzapine Induces Hyperglycemia Associated with Hepatic and Extra-Hepatic Insulin Resistance

<div><p>Atypical antipsychotic drugs such as Olanzapine induce weight gain and metabolic changes associated with the development of type 2 diabetes. The mechanisms underlying the metabolic side-effects of these centrally acting drugs are still unknown to a large extent. We compared the effects of peripheral (intragastric; 3 mg/kg/h) versus central (intracerebroventricular; 30 µg/kg/h) administration of Olanzapine on glucose metabolism using the stable isotope dilution technique (Experiment 1) in combination with low and high hyperinsulinemic-euglycemic clamps (Experiments 2 and 3), in order to evaluate hepatic and extra-hepatic insulin sensitivity, in adult male Wistar rats. Blood glucose, plasma corticosterone and insulin levels were measured alongside endogenous glucose production and glucose disappearance. Livers were harvested to determine glycogen content. Under basal conditions peripheral administration of Olanzapine induced pronounced hyperglycemia without a significant increase in hepatic glucose production (Experiment 1). The clamp experiments revealed a clear insulin resistance both at hepatic (Experiment 2) and extra-hepatic levels (Experiment 3). The induction of insulin resistance in Experiments 2 and 3 was supported by decreased hepatic glycogen stores in Olanzapine-treated rats. Central administration of Olanzapine, however, did not result in any significant changes in blood glucose, plasma insulin or corticosterone concentrations nor in glucose production. In conclusion, acute intragastric administration of Olanzapine leads to hyperglycemia and insulin resistance in male rats. The metabolic side-effects of Olanzapine appear to be mediated primarily via a peripheral mechanism, and not to have a central origin.</p> </div

Effects of adrenalectomy on daily gene expression rhythms in the rat suprachiasmatic and paraventricular hypothalamic nuclei and in white adipose tissue

<div><p>It is assumed that in mammals the circadian rhythms of peripheral clocks are synchronized to the environment via neural, humoral and/or behavioral outputs of the central pacemaker in the suprachiasmatic nucleus of the hypothalamus (SCN). With regard to the humoral outputs, the daily rhythm of the adrenal hormone corticosterone is considered as an important candidate. To examine whether adrenal hormones are necessary for the maintenance of daily rhythms in gene expression in white adipose tissue (WAT), we used RT-PCR to check rhythmic as well as 24 h mean gene expression in WAT from adrenalectomized (ADX) and sham-operated rats. In addition, we investigated the effect of adrenalectomy on gene expression in the hypothalamic SCN and paraventricular nucleus (PVN). Adrenalectomy hardly affected daily rhythms of clock gene expression in WAT. On the other hand, >80% of the rhythmic metabolic/adipokine genes in WAT lost their daily rhythmicity in ADX rats. Likewise, in the hypothalamus adrenalectomy had no major effects on daily rhythms in gene expression, but it did change the expression level of some of the neuropeptide genes. Together, these data indicate that adrenal hormones are important for the maintenance of daily rhythms in metabolic/adipokine gene expression in WAT, without playing a major role in clock gene expression in either WAT or hypothalamus.</p></div

Effects of ICV infusion of Olanzapine.

<p>(Vehicle group n = 6, Olanzapine group n = 9). 2a: Glucose evolution before (t = 90 to t = 100) and during (t = 120 to t = 260) ICV Olanzapine infusion (30 µg/kg/h). No significant differences between the 2 groups were detected (ANOVA repeated measures; <i>Time,</i> p<0.001; <i>Time * Group,</i> p = 0.59; <i>Group,</i> p = 0.635). 2b: Endogenous glucose production before (t = 90 to t = 100) and during (t = 120 to t = 260) ICV Olanzapine infusion. No significant changes were detected (ANOVA repeated measures; <i>Time,</i> p = 0.731; <i>Time * Group,</i> p = 0.709; <i>Group,</i> p = 0.84). 2c: Corticosterone levels before (t = 90 to t = 100) and during (t = 120 to t = 260) ICV Olanzapine infusion. No significant changes were detected (ANOVA repeated measures; <i>Time,</i> p = 0.971; <i>Time * Group,</i> p = 0.631; <i>Group,</i> p = 0.546). 2d: Plasma insulin levels before (mean of time points t = 90 and t = 100) and at the end (mean of time points t = 220 and t = 260) of the ICV infusion of Olanzapine. No significant changes were detected (ANOVA repeated measures; <i>Time,</i> p = 0.722; <i>Time * Group,</i> p = 0.638; <i>Group,</i> p = 0.274). Vehicle-treated animals  =  white dots; Olanzapine-treated animals  =  black dots.</p

Effects of intragastric infusion of Olanzapine on liver glycogen content in Experiments 1, 2 and 3.

<p>6a: During Experiment-1 hepatic glycogen levels show a non-significant increase in the Olanzapine-treated animals (p = 0.096; T-test). 6b: During the low-level hyperinsulinemic-euglycemic clamp (Experiment-2) hepatic glycogen levels are decreased in the Olanzapine-treated animals (p = 0.007; T-test). 6c: During the high-level hyperinsulinemic-euglycemic clamp (Experiment-3) the Olanzapine-treated animals show significantly less hepatic glycogen storage than the control group (p = 0.043; T-test). Vehicle-treated animals  =  white bars; Olanzapine-treated animals  =  black bars. Abs/mg  =  Absorption measured at 600 nm per mg wet tissue.</p

Plasma Olanzapine levels after intragastric (IG) and intracerebroventricular (ICV) infusion of Olanzapine.

<p>(IG: Vehicle group n = 5, Olanzapine group n = 6 and ICV Vehicle group n = 8 and Olanzapine group n = 12) Plasma Olanzapine levels are significantly higher in IG-Olanzapine-treated than in IG-vehicle-infused animals (One-Way ANOVA, p<0.001), or ICV-Olanzapine animals (2-Way ANOVA, <i>Administration route * Treatment</i> p<0.001). Plasma Olanzapine levels of ICV-Olanzapine animals are not significantly different from the ICV-Vehicle animals (One-Way ANOVA, p = 0.2). Vehicle-treated animals  =  white bars; Olanzapine-treated animals  =  black bars; *p<0.001.</p

Effects of intragastric infusion of Olanzapine.

<p>(Vehicle group n = 5, Olanzapine group n = 6). 1a: Glucose evolution before (t = 90 to t = 100) and during (t = 120 to t = 240) the intragastric infusion of Olanzapine infusion (3 mg/kg/h). Glycemia significantly increased after 60 min of Olanzapine infusion (*p<0.05, **p<0.001; ANOVA repeated measures; <i>Time,</i> p<0.001; <i>Time * Group,</i> p<0.001; <i>Group,</i> p = 0.001). 1b: Endogenous glucose production before (t = 90 to t = 100) and during (t = 120 to t = 240) intragastric Olanzapine infusion. No significant changes were observed (ANOVA repeated measures; <i>Time,</i> p = 0.426; <i>Time * Group,</i> p = 0.937; <i>Group,</i> p = 0.356). 1c: Corticosterone levels before (t = 90 to t = 100) and during (t = 120 to t = 240) intragastric Olanzapine infusion. Corticosterone levels are significantly higher in the Olanzapine group only at t = 220 (*p<0.05; ANOVA repeated measures; <i>Time,</i> p<0.001; <i>Time * Group,</i> p = 0.58; <i>Group,</i> p = 0.039). 1d: Plasma insulin levels before (mean of time points t = 90 and t = 100) and at the end (mean of time points t = 180 and t = 220) of the intragastric infusion of Olanzapine. No significant differences were detected (ANOVA repeated measures; <i>Time,</i> p = 0.601; <i>Time * Group,</i> p = 0.981; <i>Group,</i> p = 0.834). Vehicle-treated animals  =  white dots; Olanzapine-treated animals  =  black dots.</p

Effects of intragastric infusion of Olanzapine on liver insulin sensitivity (Experiment 2).

<p>(Vehicle group n = 8, Olanzapine group n = 7) 4a: Endogenous glucose production at basal (mean of 3 time points: t = 90 to t = 100; white bars) and during the hyperinsulinemic state (mean of 5 time points: t = 250 to t = 290; black bars). EGP significantly decreased during the hyperinsulinemic state for the vehicle group (p = 0.018, One-Way ANOVA) and remained unchanged in the Olanzapine group (p = 0.111, One-Way ANOVA). 4b: Glucose uptake at basal (mean of 3 time points: t = 90 to t = 100; white bars) and during the hyperinsulinemic state (mean of 5 time points: t = 250 to t = 290; black bars). Glucose uptake is significantly increased in both the vehicle (p = 0.002, One-Way ANOVA) and Olanzapine group (p = 0.046, One-Way ANOVA). 4c: Plasma corticosterone levels were significantly elevated by the IG infusion of Olanzapine (ANOVA repeated measures; <i>Time,</i> p<0.001; <i>Time * Group,</i> p<0.001; <i>Group,</i> p = 0.039). Vehicle-treated animals  =  white dots; Olanzapine-treated animals  =  black dots. 4d: Plasma insulin levels were elevated 1.3-fold during the hyperinsulinemic state (mean of 3 time points; black bars) compared to the basal level (mean of 2 time points; white bars) (ANOVA repeated measures; <i>Time,</i> p = 0.062; <i>Time * Group,</i> p = 0.956; <i>Group,</i> p = 0.706). *p<0.05,**p<0.001.</p