Exploration of body weight regulation by polyunsaturated fatty acids in rat: potential association with hypothalamic neurogenesis

Of the environmental factors which influence body weight, nutrients have the most impact. Saturated fatty acids (SFAs) are a macronutrient, which induce obesity, characterised by metabolic dysfunction and altered feeding behaviour. Currently, there are no effective pharmaceutical treatments for obesity. Nutraceutical intervention, including consumption of polyunsaturated fatty acids (PUFAs), represents a promising alternative. PUFAs oppose the effects of SFAs, attenuating weight gain by enhancing satiety. However, in studies using human and rodent models findings are difficult to interpret, due to variation in protocols. The primary aim of this project was to create a rational model of chronic PUFA consumption. Obesity is underpinned by alterations in hypothalamic neuronal plasticity including impairment of neurogenesis. These changes occur in response to nutrients or by regulation of appetite-related hormones. In contrast, dietary restriction stimulates neurogenesis, and evidence has suggested that PUFAs enhance hypothalamic neurogenesis. The secondary aim of this project was to pilot methods for stimulating and observing neurogenesis in hypothalamus of rat. These two lines of enquiry were pursued to begin addressing the complex research question of whether PUFAs exert beneficial effects on body weight by stimulating hypothalamic neurogenesis. Wistar rats fed commercially formulated diets equally enriched with high concentrations of SFAs and PUFAs, from lard and fish oil, respectively, for two months showed no difference in energy intake or body weight. Both diets induced leptin and insulin resistance, but PUFAs reduced triglyceride concentrations. Hence, PUFAs improved lipid metabolism independently of induced obese phenotype. The meal pattern signatures associated with each diet were also similar; however, PUFA-fed animals demonstrated enhanced diurnal satiety. Closer examination of the diet compositions revealed the overlap of results was likely due to the presence of SFAs in the PUFA diet. This led to reformulation, using fatty acids of greater purity. The chosen sources were coconut oil (SFAs), and a commercial preparation of omega-3 PUFAs. A shorter-term, preliminary investigation involving three weeks’ dietary exposure was conducted. Energy intake was again similar between SFA- and omega-3-fed animals but weight gain was attenuated and adiposity reduced by omega-3 feeding. However, the enhanced satiety previously observed was not borne out. A rise in concentration of brain-derived neurotrophic factor, known to be associated with beneficial effects of PUFA intake, in the final study week suggests that studies of longer duration may be required to fully assess the effects of dietary PUFAs. Concurrent pilot work showed that hypothalamic cell proliferation could be stimulated in response to simple enrichment (play tube) introduced to the cage. However, a full study failed to repeat these findings, supporting the notion that neurogenesis is subject to many influences, including age, species, strain and stress, the degrees of influence of which would have to be determined in a series of systematically controlled studies. Failure to stimulate cell proliferation in PUFA-fed rats suggested further that change in dietary fatty acid composition is not a powerful enough intervention to stimulate neurogenesis, when used alone in Wistar rats. In conclusion, application of appropriate controls for dietary energy content and composition show that benefits to body weight metabolism of long-term consumption of diets highly enriched with PUFAs, and, in particular, omega-3 fatty acids can be successfully modelled in rat. However, further work is required to determine the precise timeline of their emergence and underlying mechanisms

Altered Left Ventricular Ion Channel Transcriptome in a High-Fat-Fed Rat Model of Obesity: Insight into Obesity-Induced Arrhythmogenesis

Introduction. Obesity is increasingly common and is associated with an increased prevalence of cardiac arrhythmias. The aim of this study was to see whether in obesity there is proarrhythmic gene expression of ventricular ion channels and related molecules. Methods and Results. Rats were fed on a high-fat diet and compared to control rats on a normal diet (). After 8 weeks, rats on the high-fat diet showed significantly greater weight gain and higher adiposity. Left ventricle samples were removed at 8 weeks and mRNA expression of ion channels and other molecules was measured using qPCR. Obese rats had significant upregulation of , HCN4, , RYR2, NCX1, SERCA2a, and RYR2 mRNA and downregulation of ERG mRNA. In the case of HCN4, it was confirmed that there was a significant increase in protein expression. The potential effects of the mRNA changes on the ventricular action potential and intracellular Ca2+ transient were predicted using computer modelling. Modelling predicted prolongation of the ventricular action potential and an increase in the intracellular Ca2+ transient, both of which would be expected to be arrhythmogenic. Conclusion. High-fat diet causing obesity results in arrhythmogenic cardiac gene expression of ion channels and related molecules

Preventive and curative effect of melatonin on mammary carcinogenesis induced by dimethylbenz[a]anthracene in the female Sprague–Dawley rat

INTRODUCTION: It has been well documented that the pineal hormone, melatonin, which plays a major role in the control of reproduction in mammals, also plays a role in the incidence and growth of breast and mammary cancer. The curative effect of melatonin on the growth of dimethylbenz [a]anthracene-induced (DMBA-induced) mammary adenocarcinoma (ADK) has been previously well documented in the female Sprague–Dawley rat. However, the preventive effect of melatonin in limiting the frequency of cancer initiation has not been well documented. METHODS: The aim of this study was to compare the potency of melatonin to limit the frequency of mammary cancer initiation with its potency to inhibit tumor progression once initiation, at 55 days of age, was achieved. The present study compared the effect of preventive treatment with melatonin (10 mg/kg daily) administered for only 15 days before the administration of DMBA with the effect of long-term (6-month) curative treatment with the same dose of melatonin starting the day after DMBA administration. The rats were followed up for a year after the administration of the DMBA. RESULTS: The results clearly showed almost identical preventive and curative effects of melatonin on the growth of DMBA-induced mammary ADK. Many hypotheses have been proposed to explain the inhibitory effects of melatonin. However, the mechanisms responsible for its strong preventive effect are still a matter of debate. At least, it can be envisaged that the artificial amplification of the intensity of the circadian rhythm of melatonin could markedly reduce the DNA damage provoked by DMBA and therefore the frequency of cancer initiation. CONCLUSION: In view of the present results, obtained in the female Sprague–Dawley rat, it can be envisaged that the long-term inhibition of mammary ADK promotion by a brief, preventive treatment with melatonin could also reduce the risk of breast cancer induced in women by unidentified environmental factors

Stroke genetics informs drug discovery and risk prediction across ancestries

Previous genome-wide association studies (GWASs) of stroke — the second leading cause of death worldwide — were conducted predominantly in populations of European ancestry1,2. Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis3, and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach4, we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry5. Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries

Stroke genetics informs drug discovery and risk prediction across ancestries

Previous genome-wide association studies (GWASs) of stroke - the second leading cause of death worldwide - were conducted predominantly in populations of European ancestry(1,2). Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis(3), and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach(4), we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry(5). Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries.</p

Tamoxifen Stimulates Melatonin Secretion After Exposure to a Mammary Carcinogen, the Dimethyl Benz(a)Anthracene, in Sprague Dawley Female Rat

International audienceA single intragastric administration of 7,12-dimethylbenz(a)anthracene (DMBA) has been shown to induce mammary tumors in young cycling female Sprague-Dawley rats. The appearance of the tumors is preceded, during the la-tency phase, by a series of neuroendocrine disturbances, including attenuation of the preovulatory Luteinizing Hormone surge and Gonadotropin-Releasing Hormone release and amplification of the preovulatory 17-Estradiol (E2) surge. Also, E2 treatment leads to a complete blunting of the Isoproterenol-induced stimulation of Melatonin secretion.In this study, we examined the hypothesis that Tamoxifen, an antagonist of E2, would stimulate the Isoproterenol-induced Mela-tonin (MT) secretion from the pineal gland, during the latency phase. Sprague-Dawley rats, 55-60 days of age, received, on the Estrous day of the Estrous cycle, a single dose of 15 mg DMBA delivered by intragastric intubation. In order to avoid possible interactions with endogenous steroids or mammary tumor-derived compounds, they were ovariectomized 5 days later and, one month later, sacrificed by decapitation at 10 a.m. Then, pineal glands were removed and placed in perifusion chambers containing Hanks 199 medium. The medium was satured with O 2 /CO 2 (95 %/5 %) and its pH was 7.4. Ten independent chambers were immersed in a water bath at 37°C. Each pineal gland received medium (flow rate : 0.16 ml/min) through a system of input lines. The fractions were collected every 10 min, and immediately frozen at –20°C until Melatonin RIA. Experiments were repeated to obtain up to five experimental points for each treatment. Tamoxifen (10-9 to 10-7 M) was applied during the entire perifusion period (7 hours). Isoproterenol (10-6 M) was applied for 20 min after 3 hours in perifusion. Melatonin concentrations and Areas Under the Curves were compared using two-factor ANOVA as well as parametric or nonparametric two-sample methods after testing sample normality. In vehicle treated rats, Tamoxifen treatment, at the concentration of 10-9 M, leads to a non significant amplification of the Isoproterenol-induced stimulation of Melatonin secretion. In DMBA-treated rats, Tamoxifen treatment leads,starting from 10-9 M to a dose-dependent increase (up to 400% increase) of the Isoproterenol-induced stimulation of Melatonin. The results suggest that in addition to the well documented beneficial effects of Tamoxifen at the mammary gland level, this E2 antagonist may also have, after DMBA treatment, an additional beneficial effect at the pineal gland level throughout the stimulation of Melatonin, which exerts an inhibitory action on the induction and on the growth of breast cancers

Implication du système mélatoninergique dans la carcinogénèse mammaire induite par le 7,12-Diméthylbenz(a)anthracène(DMBA)chez la ratte de souche Sprague-Dawley

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Monitoring type 2 diabetes from volatile faecal metabolome in cushing’s syndrome and single Afmid mouse models via a longitudinal study

The analysis of volatile organic compounds (VOCs) as a non-invasive method for disease monitoring, such as type 2 diabetes (T2D) has shown potential over the years although not yet set in clinical practice. Longitudinal studies to date are limited and the understanding of the underlying VOC emission over the age is poorly understood. This study investigated longitudinal changes in VOCs present in faecal headspace in two mouse models of T2D – Cushing’s syndrome and single Afmid knockout mice. Longitudinal changes in bodyweight, blood glucose levels and plasma insulin concentration were also reported. Faecal headspace analysis was carried out using selected ion flow tube mass spectrometry (SIFT-MS) and thermal desorption coupled to gas chromatography-mass spectrometry (TD-GC-MS). Multivariate data analysis of the VOC profile showed differences mainly in acetic acid and butyric acid able to discriminate the groups Afmid and Cushing’s mice. Moreover, multivariate data analysis revealed statistically significant differences in VOCs between Cushing’s mice/wild-type (WT) littermates, mainly short-chain fatty acids (SCFAs), ketones, and alcohols, and longitudinal differences mainly attributed to methanol, ethanol and acetone. Afmid mice did not present statistically significant differences in their volatile faecal metabolome when compared to their respective WT littermates. The findings suggested that mice developed a diabetic phenotype and that the altered VOC profile may imply a related change in gut microbiota, particularly in Cushing’s mice. Furthermore, this study provided major evidence of age-related changes on the volatile profile of diabetic mice

Loss of arylformamidase with reduced thymidine kinase expression leads to impaired glucose tolerance

Tryptophan metabolites have been linked in observational studies with type 2 diabetes, cognitive disorders, inflammation and immune system regulation. A rate-limiting enzyme in tryptophan conversion is arylformamidase (Afmid), and a double knockout of this gene and thymidine kinase (Tk) has been reported to cause renal failure and abnormal immune system regulation. In order to further investigate possible links between abnormal tryptophan catabolism and diabetes and to examine the effect of single Afmid knockout, we have carried out metabolic phenotyping of an exon 2 Afmid gene knockout. These mice exhibit impaired glucose tolerance, although their insulin sensitivity is unchanged in comparison to wild-type animals. This phenotype results from a defect in glucose stimulated insulin secretion and these mice show reduced islet mass with age. No evidence of a renal phenotype was found, suggesting that this published phenotype resulted from loss of Tk expression in the double knockout. However, despite specifically removing only exon 2 of Afmid in our experiments we also observed some reduction of Tk expression, possibly due to a regulatory element in this region. In summary, our findings support a link between abnormal tryptophan metabolism and diabetes and highlight beta cell function for further mechanistic analysis