9 research outputs found
Diurnal rhythms of plasma leptin concentrations.
<p>(a) Analysis of absolute concentration revealed a significant effect of group (<i>p</i><0.001; 2-way repeated measures ANOVA) but not of time or time x group interaction. *<i>p</i><0.05 lean vs type 2 diabetic subjects. (b–c) Following normalisation of each individual’s raw data to their own mean concentration, the group values were calculated and fitted with a cosinor curve. Normalised data are expressed relative to (b) external time of day and (c) endogenous circadian time, estimated using DLMO where 360°  =  time of DLMO. The DLMO of two participants in the type 2 diabetic participant group could not be calculated due to the absence of a peak in the melatonin profile; their data were thus excluded. Statistical analysis showed a significant effect of time (<i>p</i><0.001; 2-way repeated measures ANOVA) but not for group or interaction in both (b) and (c). (a–b) The light-dark conditions are indicated by the bars below the x-axes. In all panels, diamonds, solid red line  =  lean subjects (n = 8); square, dashed blue line  =  obese non-diabetic subjects (n = 10); triangle, dotted black line  =  type 2 diabetic subjects (n = 7).</p
Expression of leptin mRNA in white adipose biopsies.
<p>(a) Data represent mean ± SEM of leptin mRNA in 6-hourly serial biopsies. There was a significant effect of group (<i>p</i><0.05; 2-way repeated measures ANOVA), but not of time or time x group interaction. There were no significant (<i>p</i>>0.05; Bonferroni post-hoc test) pair wise differences in leptin mRNA expression between the subject groups. The light-dark conditions are indicated by the bars below the x-axis. Diamonds, solid red line  =  lean subjects (n = 8); squares, dashed blue line  =  obese non-diabetic subjects (n = 10); triangles, dotted black line  =  type 2 diabetic group (n = 7). The average leptin mRNA expression for each subject was significantly (<i>p</i><0.05) correlated with both (b) average plasma leptin concentrations and (c) subjects’ BMI. (d) The average plasma leptin concentration for each subject was significantly (<i>p</i><0.001) correlated with subjects’ BMI.</p
Pre-screen participant data.
*<p><i>P</i><0.05 compared to lean participants; <sup>+</sup><i>P</i><0.05 compared to obese non-diabetic participants (1-way ANOVA with Bonferroni post-hoc test).</p
Acrophase (peak time) and amplitude of the leptin rhythms determined by cosinor analysis.
<p>A cosine wave was fitted to each individual leptin profile. There was no significant (<i>p</i>>0.05; 1-way ANOVA) effect of group on either the acrophase (peak time) or amplitude of the rhythms. The acrophase of the leptin rhythm was also corrected to the dim light melatonin onset (DLMO).</p
Differences in amplitude, but not onset time, of nocturnal plasma melatonin concentration.
<p>(a) Data in the top panel represent mean ± SEM of plasma melatonin concentrations over 25 hours. Diamonds, solid red line  =  lean subjects (n = 8); squares, dashed blue line  =  obese non-diabetic subjects (n = 10); triangles, dotted black lines  =  type 2 diabetic subjects (n = 7). The light-dark conditions are indicated by the bar below the x-axis. There was a significant (<i>p</i>0.001; 2-way repeated measures ANOVA) effect of time, group and time x group interaction. Nocturnal melatonin concentrations were significantly higher in the obese non-diabetic group (<sup>+</sup><i>p</i><0.05, vs lean, **<i>p</i><0.01 vs type 2 diabetic subjects). (b) Data in the bottom panel represent mean ± SEM of the dim light melatonin onset (DLMO) in each group. There was no significant (<i>p</i>>0.05, 1-way ANOVA) difference between the group averages. Lean  =  lean healthy participant group; ow  =  obese non-diabetic group; T2DM  =  type 2 diabetic group.</p
Regulation of rat <i>Mt1</i> promoter activity by PITX-1 and EGR-1 in vitro.
<p>COS-7 cells were co-transfected with an <i>Mt1</i>-luciferase reporter construct and a combination of control vector, PITX-1 expression vector and EGR-1 expression vector. Horizontal bars indicate mutagenesis of PITX-1 and EGR-1 binding sites. P1: distal PITX-1 consensus site; P2: proximal PITX-1 consensus site; E: EGR-1 consensus site. *** p<0.001 vs control group; ### p<0.001 vs PITX-1 group (one-way ANOVA with Bonferroni post-hoc test).</p
Pituitary <i>Mt1</i> expression is unaltered in adult <i>Egr-1<sup>−</sup></i><sup>/−</sup> mice.
<p>Brain and pituitary tissue from adult wild type (WT) and <i>Egr-1<sup>−</sup></i><sup>/−</sup> mice was dissected with the pituitary stalk intact, frozen on dry ice and stored at −80°C. Twenty micron sagittal sections were cut and <i>Mt1</i> mRNA expression determined by in situ hybridisation histochemistry. Quantification of <i>Mt1</i> expression by densitometry revealed no significant difference (p>0.05 unpaired t-test) of genotype. Representative autoradiographs are shown above the respective bar.</p
Treatment of rats with GnRH antagonist impairs reproductive status but does not affect <i>Mt1</i> expression.
<p>Male Wistar rats were given a daily i.p. injection of the GnRH antagonist cetrorelix (100 µg/day) or saline control for 4 weeks. (A) Serum LH was measured by ELISA. (B–C) Testis morphology was assessed by (B) paired testis weight and (C) histological analysis of tissue sections using hematoxylin and eosin staining. Scale bar = 25 µm (D–E) Brain and pituitary tissue from saline and cetrorelix-treated rats was dissected with the pituitary stalk intact, frozen on dry ice and stored at −80°C. Twenty micron sagittal sections were cut and <i>Mt1</i> mRNA expression determined by in situ hybridisation histochemistry. (D) Representative autoradiographs. In both treatment groups, strong pituitary expression was observed in the pars tuberalis and along the rostral extent of the ventral pars distalis; weaker expression was observed throughout the rest of the pars distalis. (E) Quantification of <i>Mt1</i> expression by densitometry. *** p<0.001 saline vs cetrorelix group (unpaired t-test). Sal: saline-treated; Cet: cetrorelix-treated.</p
GnRH agonist treatment induces EGR-1 and inhibits <i>Mt1</i> expression in αT3-1 gonadotroph cells.
<p>Cells were treated with 100(A) Total mRNA was extracted for analysis of <i>Egr-1</i> mRNA, expressed relative to <i>Gapdh</i>, by qRT-PCR. *** p<0.001 vs time 0 (one-way ANOVA with Bonferroni post-hoc test). (B) Cytoplasmic and nuclear-enriched lysates were prepared for analysis of EGR-1 and actin protein expression by western blot. (C) Following 20 hours of GnRH agonist treatment, total mRNA was extracted for analysis of <i>Mt1</i> mRNA, expressed relative to <i>Gapdh</i>, by qRT-PCR. * p<0.05 control vs treated group (unpaired t-test).</p