Resistance to diet-induced adiposity in cannabinoid receptor-1 deficient mice is not due to impaired adipocyte function

Background: Overactivity and/or dysregulation of the endocannabinoid system (ECS) contribute to development of obesity. In vitro studies indicate a regulatory role for the cannabinoid receptor 1 (CB1) in adipocyte function and CB1-receptor deficient (CB1-/-) mice are resistant to high fat diet-induced obesity. Whether this phenotype of CB1-/- mice is related to altered fat metabolism in adipose tissue is unknown. Methods: We evaluated adipose tissue differentiation/proliferation markers and quantified lipogenic and lipolytic activities in fat tissues of CB1-/- and CB1+/+ mice fed a high-fat (HF) or a high-fat/fish oil (HF/FO) diet as compared to animals receiving a low-fat chow diet. Comparison between HF diet and HF/FO diet allowed to investigate the influence of dietary fat quality on adipose tissue biology in relation to CB1 functioning. Results: The adiposity-resistant phenotype of the CB1-/- mice was characterized by reduced fat mass and adipocyte size in HF and HF/FO-fed CB1-/- mice in parallel to a significant increase in energy expenditure as compared to CB1+/+ mice. The expression levels of adipocyte differentiation and proliferation markers were however maintained in these animals. Consistent with unaltered lipogenic gene expression, the fatty acid synthesis rates in adipose tissues from CB1-/- and CB1+/+ mice were unchanged. Whole-body and adipose-specific lipoprotein lipase (LPL) activities were also not altered in CB1-/- mice. Conclusions: These findings indicate that protection against diet-induced adiposity in CB1-deficient mice is not related to changes in adipocyte function per se, but rather results from increased energy dissipation by oxidative and non-oxidative pathways.

Measuring serotonin synthesis: from conventional methods to PET tracers and their (pre)clinical implications

The serotonergic system of the brain is complex, with an extensive innervation pattern covering all brain regions and endowed with at least 15 different receptors (each with their particular distribution patterns), specific reuptake mechanisms and synthetic processes. Many aspects of the functioning of the serotonergic system are still unclear, partially because of the difficulty of measuring physiological processes in the living brain. In this review we give an overview of the conventional methods of measuring serotonin synthesis and methods using positron emission tomography (PET) tracers, more specifically with respect to serotonergic function in affective disorders. Conventional methods are invasive and do not directly measure synthesis rates. Although they may give insight into turnover rates, a more direct measurement may be preferred. PET is a noninvasive technique which can trace metabolic processes, like serotonin synthesis. Tracers developed for this purpose are α-[11C]methyltryptophan ([11C]AMT) and 5-hydroxy-L-[β-11C]tryptophan ([11C]5-HTP). Both tracers have advantages and disadvantages. [11C]AMT can enter the kynurenine pathway under inflammatory conditions (and thus provide a false signal), but this tracer has been used in many studies leading to novel insights regarding antidepressant action. [11C]5-HTP is difficult to produce, but trapping of this compound may better represent serotonin synthesis. AMT and 5-HTP kinetics are differently affected by tryptophan depletion and changes of mood. This may indicate that both tracers are associated with different enzymatic processes. In conclusion, PET with radiolabelled substrates for the serotonergic pathway is the only direct way to detect changes of serotonin synthesis in the living brain

Serotonin-2C antagonism augments the effect of citalopram on serotonin and dopamine levels in the ventral tegmental area and nucleus accumbens

Many patients with major depression do not respond to selective serotonin reuptake inhibitors (SSRIs). Lack of response could be due to inhibition of dopamine (DA) release by serotonin (5-HT) through 5-HT2c receptors. Combining an SSRI with a 5-HT2c antagonist may result in improved efficacy by causing simultaneous increases of 5-HT and DA. In order to test this augmentation strategy, male Wistar rats were treated (s.c.) with an acute dose of the SSRI citalopram (Cit, 5 mg/ kg), the 5-HT2c antagonist SB 242084 (SB, 2 mg/ kg), or Cit + SB, and the effect on 5-HT and DA release in the nucleus accumbens (NAcc) was assessed by microdialysis. In a separate experiment, animals were treated with vehicle, Cit (20 mg/kg/ d), SB (2 mg/kg/d) or Cit + SB for a period of 2 days (s.c.), and the impact on the release of 5-HT and DA in the ventral tegmental area (VIA) and NAcc was studied. On the day of microdialysis, 5-HT2c receptor sensitivity was assessed with an SB challenge. Acutely administered Cit + SB increased 5-HT release in the NAcc more than Cit alone. SB alone increased DA release in the NAcc (not in the VTA), but when administered together with Cit, this effect was abolished. A 2-day treatment with Cit or Cit + SB increased 5-HT release in both VTA and NAcc. Combining Cit with SB augmented the effect of Cit in the VTA. DA release in VTA and NAcc was only significantly increased after 2-days of treatment with Cit + SB. In conclusion, Cit + SB had synergistic effects on 5-HT and DA release after 2-days of treatment, probably related to a decreased tonic inhibition of DA release via 5-HT2c receptors. Regional differences occur and future studies should elucidate if this augmentation strategy is beneficial at the behavioral level. (C) 2014 Elsevier Ltd. All rights reserved

Plasma nitrate levels are related to metabolic syndrome and are not altered by treatment with DPP-4 inhibitor linagliptin: a randomised, placebo-controlled trial in patients with early type 2 diabetes mellitus

The depletion of nitrate and nitrite, stable nitric oxide (NO) end-products, promotes adipose tissue dysfunction and insulin resistance (IR). Dipeptidyl peptidase-4 (DPP-4) inhibitors have the potentially beneficial side effect of increasing NO availability. In this study, nitrate and nitrite levels and the effects of DPP-4 inhibitor linagliptin were investigated in relation to metabolic syndrome (MetS) markers. Treatment-naive patients with early type 2 diabetes mellitus (T2DM) (n = 40, median age 63 IQR (55-67) years, 63% male, mean HbA1c 45 ± 4.4 mmol/mol) were randomized (1:1) to linagliptin (5 mg/day) or placebo. MetS-related markers (body mass index (BMI), triglycerides, HOMA-IR, gamma-glutamyltransferase (GGT), C-reactive protein (CRP), and adiponectin), plasma levels of nitrate, nitrite, total free thiols (TFT) and vegetable intake were estimated at baseline and after 4 and 26 weeks of treatment. Plasma nitrate, but not nitrite, correlated positively with vegetable intake (r = 0.38, p = 0.018) and was inversely associated with HOMA-IR (r = -0.44, p = 0.006), BMI (r = -0.35, p = 0.028), GGT (r = -0.37, p = 0.019) and CRP (r = -0.34, p = 0.034). The relationship between nitrate and HOMA-IR remained significant after adjusting for BMI, CRP, vegetable intake and GGT. With stable vegetable intake, nitrate and nitrite, TFT, adipokines and CRP did not change after 26 weeks of linagliptin treatment. While plasma nitrate is inversely associated with MetS, linagliptin treatment does not significantly influence nitrate and nitrite concentrations, oxidative stress, adipose tissue function and systemic inflammation.</p

Analysis of 5-HT2A Receptor Binding with [C-11]MDL 100907 in Rats:Optimization of Kinetic Modeling

<p>Preclinical positron emission tomography studies are important to follow disease progression and develop new pharmacological agents. We investigated whether kinetic modeling of 5-HT2A tracer [C-11]MDL 100907 is possible in rats.</p><p>Kinetic modeling with either metabolite-corrected plasma curve or with the cerebellum as a reference tissue resulted in a good correlation of nondisplaceable binding potential (BPND) calculated from a two-tissue compartment model (2TCM) or different reference tissue models. Injecting the tracer by a slower bolus decreases the variation in 2TCM outcome parameters and results in a good correlation between k(3)/k(4) and the other models. Application of 0.2 mg/kg cold MDL 100907 resulted in almost complete occupancy of 5-HT2A receptors.</p><p>A reference tissue model can be used for [C-11]MDL kinetic modeling in rats, which is preferable in pharmacological or longitudinal studies.</p>

Coverage of Lateral Lymph Nodes in Rectal Cancer Patients with Routine Radiation Therapy Practice and Associated Locoregional Recurrence Rates

Purpose: Involved internal iliac and obturator lateral lymph nodes (LLNs) are a known risk factor for the occurrence of ipsilateral local recurrences (LLR) in rectal cancer. This study examined coverage of LLNs with routine radiation therapy practice in the Netherlands and associated LLR rates. Methods and Materials: Patients with a primary tumor ≤8 cm of the anorectal junction, cT3-4 stage, and at least 1 internal iliac or obturator LLN with short axis ≥5 mm who received neoadjuvant (chemo)radiation therapy, were selected from a national, cross-sectional study of patients with rectal cancer treated in the Netherlands in 2016. Magnetic resonance images and radiation therapy treatment plans were reviewed regarding segmented LLNs as gross tumor volume (GTV), location of LLNs within clinical target volume (CTV), and received proportion of the planned radiation therapy dose. Results: A total of 223 out of 3057 patients with at least 1 LLN ≥5 mm were selected. Of those, 180 (80.7%) LLNs were inside the CTV, of which 60 (33.3%) were segmented as GTV. Overall, 202 LLNs (90.6%) received ≥95% of the planned dose. Four-year LLR rates were not significantly higher for LLNs situated outside the CTV compared with those inside (4.0% vs 12.5%, P =.092) or when receiving &lt;95% versus ≥95% of the planned radiation therapy dose (7.1% vs 11.3%, P =.843), respectively. Two of 7 patients who received a dose escalation of 60 Gy developed an LLR (4-year LLR rate of 28.6%). Conclusions: This evaluation of routine radiation therapy practice showed that adequate coverage of LLNs was still associated with considerable 4-year LLR rates. Techniques resulting in better local control for patients with involved LLNs need to be explored further.</p