High-fat diet-induced alterations in the feeding suppression of low-dose nisoxetine, a selective norepinephrine reuptake inhibitor

Coconut Oil Saturated Fatty Acids Improved Energy Homeostasis but not Blood Pressure or Cognition in VCD-Treated Female Mice

Obesity, cardiometabolic disease, cognitive decline, and osteoporosis are symptoms of postmenopause, which can be modeled using 4-vinylcyclohexene diepoxide (VCD)-treated mice to induce ovarian failure and estrogen deficiency combined with high-fat diet (HFD) feeding. The trend of replacing saturated fatty acids (SFAs), for example coconut oil, with seed oils that are high in polyunsaturated fatty acids, specifically linoleic acid (LA), may induce inflammation and gut dysbiosis, and worsen symptoms of estrogen deficiency. To investigate this hypothesis, vehicle (Veh)- or VCD-treated C57BL/6J mice were fed a HFD (45% kcal fat) with a high LA:SFA ratio (22.5%: 8%), referred to as the 22.5% LA diet, or a HFD with a low LA:SFA ratio (1%: 31%), referred to as 1% LA diet, for a period of 23 to 25 weeks. Compared with VCD-treated mice fed the 22.5% LA diet, VCD-treated mice fed the 1% LA diet showed lower weight gain and improved glucose tolerance. However, VCD-treated mice fed the 1% LA diet had higher blood pressure and showed evidence of spatial cognitive impairment. Mice fed the 1% LA or 22.5% LA diets showed gut microbial taxa changes that have been associated with a mix of both beneficial and unfavorable cognitive and metabolic phenotypes. Overall, these data suggest that consuming different types of dietary fat from a variety of sources, without overemphasis on any particular type, is the optimal approach for promoting metabolic health regardless of estrogen status.

High-fat diet promotes adrenaline production by visceral adipocytes

PURPOSE

Catecholamines (CA) play a major role in metabolism and immune response. Recent reports showing adipose tissue can synthetize CA enlighten new roles for these amines in obesity. This study aimed to evaluate the expression of both tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) and CA content along preadipocytes differentiation, under normal and obesigenic conditions.

METHODS

8-9 week-old male C57BL/6 mice were divided in two groups: one fed with a high-fat diet (HFD) and other with a standard diet (SD) for 20 weeks. Afterwards, both TH and PNMT expression, localization, and CA content in adipocytes, were evaluated.

RESULTS

qPCR results showed no changes for TH and PNMT expression during the differentiation process for visceral and subcutaneous preadipocytes from mice fed with SD. Comparing to SD, HFD increased TH gene expression of subcutaneous preadipocytes and PNMT gene expression of both visceral preadipocytes and adipocytes. HPLC-ED analyses revealed HFD increased visceral adipocytes noradrenaline intracellular content comparing with preadipocytes (p = 0.037). When compared with SD, HFD raised and decreased noradrenaline content, respectively, in visceral adipocytes (p = 0.004) and subcutaneous preadipocytes (p = 0.001). Along the differentiation process, HFD increased visceral adrenaline intracellular content comparing with SD (p < 0.001). HFD increased visceral comparing to subcutaneous adrenaline content for both preadipocytes (p = 0.004) and adipocytes (p = 0.001).

CONCLUSIONS

TH and PNMT expression in adipose tissue is differently modulated in visceral and subcutaneous adipose depots, and seems to depend on diet. Differences observed in visceral adipose CA handling in HFD-fed mice might uncover novel pharmacological/nutritional strategies against obesity and cardiovascular risk.

Cocaine and desipramine elicit distinct striatal noradrenergic and behavioral responses in selectively bred obesity-resistant and obesity-prone rats

Previous studies have demonstrated a role for norepinephrine (NE) in energy regulation and feeding, and basal differences have been observed in hypothalamic NE systems in obesity-prone vs. obesity-resistant rats. Differences in the function of brain reward circuits, including in the nucleus accumbens (NAc), have been shown in obesity-prone vs. obesity-resistant populations, leading many researchers to explore the role of striatal dopamine in obesity. However, alterations in NE transmission also affect NAc mediated behaviors. Therefore, here we examined differences in striatal NE and the response to norepinephrine transporter blockers in obesity-prone and obesity-resistant rats. We found that striatal NE levels increase following systemic cocaine administration in obesity-prone, but not obesity-resistant rats. This could result from either blockade of striatal norepinephrine transporters (NET) by cocaine leading to reduced NE reuptake, or circuit-based responses following cocaine administration resulting in increased NE release. Retrodialysis of the NET inhibitor, desipramine, into the ventral striatum did not cause selective increases in striatal NE levels in obesity-prone rats, suggesting that circuit-based mechanisms underlie NE increases following systemic cocaine administration. Consistent with this, systemic desipramine treatment decreased locomotor activity in obesity-prone, but not obesity-resistant rats. Furthermore, obesity-prone rats were also more sensitive to desipramine-induced reductions in food intake compared to obesity-resistant rats. Taken together, these data expand our understanding of differences in NE systems of obesity-prone vs. resistant rats, and provide new insights into basal differences in striatal systems that may influence feeding behavior.

Noradrenaline transporter availability on [11C]MRB PET predicts weight loss success in highly obese adults

PURPOSE

Although the mechanisms by which the central noradrenaline (NA) system influences appetite and controls energy balance are quite well understood, its relationship to changes in body weight remains largely unknown. The main goal of this study was to further clarify whether the brain NA system is a stable trait or whether it can be altered by dietary intervention.

METHODS

We aimed to compare central NA transporter (NAT) availability in ten obese, otherwise healthy individuals with a body mass index (BMI) of 42.4 ± 3.7 kg/m² (age 34 ± 9 years, four women) and ten matched non-obese, healthy controls (BMI 23.9 ± 2.5 kg/m², age 33 ± 10 years, four women) who underwent PET with the NAT-selective radiotracer (S,S)-[¹¹C]O-methylreboxetine (MRB) before and 6 months after dietary intervention.

RESULTS

MRI-based individual volume-of-interest analyses revealed an increase in binding potential (BP_ND) in the insula and the hippocampus of obese individuals, which correlated well with changes in BMI (-3.3 ± 5.3%; p = 0.03) following completion of the dietary intervention. Furthermore, voxel-wise regression analyses showed that lower BP_ND in these regions, but also in the midbrain and the prefrontal cortex, at baseline was associated with higher achieved weight loss (e.g., hippocampal area R² = 0.80; p < 0.0001). No changes were observed in non-obese controls.

CONCLUSION

These first longitudinal interventional data on NAT availability in highly obese individuals indicate that the central NA system is modifiable. Our findings suggest that NAT availability before intervention could help predict the amount and success of weight loss in obese individuals and help adjust treatment options individually by allowing prediction of the benefit of a dietary intervention.

Anti-adipogenic effect of Artemisia annua in diet-induced-obesity mice model

Obesity has increased continuously in western countries during the last several decades and recently become a problem in developing countries. Currently, anti-obesity drugs originating from natural products are being investigated for their potential to overcome adverse effects associated with chemical drugs. Artemisinic acid, which was isolated from the well-known anti-malaria herb Artemisia annua (AA) L., was recently shown to possess anti-adipogenic effects in vitro. However, the anti-adipogenic effects of AA in animal models have not yet been investigated. Therefore, we conducted daily oral administration with AA water extract in a diet-induced obesity animal model and treated 3T3-L1 cells with AA to confirm the anti-adipogenic effects in the related protein expressions. We then evaluated the physiology, adipose tissue histology and mRNA expressions of many related genes. Inhibition of adipogenesis by the AA water extract was observed in vitro. In the animal model, weight gain was significantly lower in the AA treated group, but there were no changes in food intake volume or calories. Reductions in lipid droplet size and mRNA expression associated with adipogenesis were also observed in animal epididymal fat. This study is the first to report that AA has an anti-obese effects in vivo.

Ketogenic diet exposure during the juvenile period increases social behaviors and forebrain neural activation in adult Engrailed 2 null mice

Prolonged consumption of ketogenic diets (KD) has reported neuroprotective benefits. Several studies suggest KD interventions could be useful in the management of neurological and developmental disorders. Alterations in the Engrailed (En) genes, specifically Engrailed 2 (En2), have neurodevelopmental consequences and produce autism-related behaviors. The following studies used En2 knockout (KO; En2(-/-)), and wild-type (WT; En2(+/+)), male mice fed either KD (80% fat, 0.1% carbohydrates) or control diet (CD; 10% fat, 70% carbohydrates). The objective was to determine whether a KD fed from weaning at postnatal day (PND) 21 to adulthood (PND 60) would alter brain monoamines concentrations, previously found dysregulated, and improve social outcomes. In WT animals, there was an increase in hypothalamic norepinephrine content in the KD-fed group. However, regional monoamines were not altered in KO mice in KD-fed compared with CD-fed group. In order to determine the effects of juvenile exposure to KD in mice with normal blood ketone levels, separate experiments were conducted in mice removed from the KD or CD and fed standard chow for 2days (PND 62). In a three-chamber social test with a novel mouse, KO mice previously exposed to the KD displayed similar social and self-grooming behaviors compared with the WT group. Groups previously exposed to a KD, regardless of genotype, had more c-Fos-positive cells in the cingulate cortex, lateral septal nuclei, and anterior bed nucleus of the stria terminalis. In the novel object condition, KO mice previously exposed to KD had similar behavioral responses and pattern of c-Fos immunoreactivity compared with the WT group. Thus, juvenile exposure to KD resulted in short-term consequences of improving social interactions and appropriate exploratory behaviors in a mouse model that displays autism-related behaviors. Such findings further our understanding of metabolic-based therapies for neurological and developmental disorders.

Enhanced motivation for food reward induced by stress and attenuation by corticotrophin-releasing factor receptor antagonism in rats: implications for overeating and obesity

RATIONALE

Overeating beyond individuals' homeostatic needs critically contributes to obesity. The neurobehavioral mechanisms underlying the motivation to consume excessive foods with high calories are not fully understood.

OBJECTIVE

The present study examined whether a pharmacological stressor, yohimbine, enhances the motivation to procure food reward with an emphasis on comparisons between standard lab chow and high-fat foods. The effects of corticotropin-releasing factor (CRF) receptor blockade by a CRF1-selective antagonist NBI on the stress-enhanced motivation for food reward were also assessed.

METHODS

Male Sprague-Dawley rats with chow available ad libitum in their home cages were trained to press a lever under a progressive ratio schedule for deliveries of either standard or high-fat food pellets. For testing yohimbine stress effects, rats received an intraperitoneal administration of yohimbine 10 min before start of the test sessions. For testing effects of CRF1 receptor blockade on stress responses, NBI was administered 20 min prior to yohimbine challenge.

RESULTS

The rats emitted higher levels of lever responses to procure the high-fat food pellets compared with their counterparts on standard food pellets. Yohimbine challenge facilitated lever responses for the reward in all of the rats, whereas the effect was more robust in the rats on high-fat food pellets compared with their counterparts on standard food pellets. An inhibitory effect of pretreatment with NBI was observed on the enhancing effect of yohimbine challenge but not on the responses under baseline condition without yohimbine administration.

CONCLUSIONS

Stress challenge significantly enhanced the motivation of satiated rats to procure extra food reward, especially the high-fat food pellets. Activation of CRF1 receptors is required for the stress-enhanced motivation for food reward. These results may have implications for our better understanding of the biobehavioral mechanisms of overeating and obesity.

Dietary-induced binge eating increases prefrontal cortex neural activation to restraint stress and increases binge food consumption following chronic guanfacine

Binge eating is a prominent feature of bulimia nervosa and binge eating disorder. Stress or perceived stress is an often-cited reason for binge eating. One notion is that the neural pathways that overlap with stress reactivity and feeding behavior are altered by recurrent binge eating. Using young adult female rats in a dietary-induced binge eating model (30 min access to binge food with or without 24-h calorie restriction, twice a week, for 6 weeks) we measured the neural activation by c-Fos immunoreactivity to the binge food (vegetable shortening mixed with 10% sucrose) in bingeing and non-bingeing animals under acute stress (immobilization; 1 h) or no stress conditions. There was an increase in the number of immunopositive cells in the dorsal medial prefrontal cortex (mPFC) in stressed animals previously exposed to the binge eating feeding schedules. Because attention deficit hyperactive disorder (ADHD) medications target the mPFC and have some efficacy at reducing binge eating in clinical populations, we examined whether chronic (2 weeks; via IP osmotic mini-pumps) treatment with a selective alpha-2A adrenergic agonist (0.5 mg/kg/day), guanfacine, would reduce binge-like eating. In the binge group with only scheduled access to binge food (30 min; twice a week; 8 weeks), guanfacine increased total calories consumed during the 30-min access period from the 2-week pre-treatment baseline and increased binge food consumption compared with saline-treated animals. These experiments suggest that mPFC is differentially activated in response to an immobilization stress in animals under different dietary conditions and chronic guanfacine, at the dose tested, was ineffective at reducing binge-like eating.

Binge-like eating attenuates nisoxetine feeding suppression, stress activation, and brain norepinephrine activity

Stress is often associated with binge eating. A critical component of the control of stress is the central norepinephrine system. We investigated how dietary-induced binge eating alters central norepinephrine and related behaviors. Young male Sprague Dawley rats received calorie deprivation (24 h) and /or intermittent sweetened fat (vegetable shortening with sucrose; 30 min) twice a week for 10 weeks. The groups were Restrict Binge (calorie deprivation/sweetened fat), Binge (sweetened fat), Restrict (calorie deprivation), and Naive (no calorie deprivation/no sweetened fat). Dietary-induced binge eating was demonstrated by Restrict Binge and Binge, which showed an escalation in 30-min intake over time. Feeding suppression following nisoxetine (3 mg/kg; IP), a selective norepinephrine reuptake inhibitor, was not evident in Restrict Binge (Restrict Binge: 107±13, Binge: 52±9, Restrict: 80±8, Naive: 59±13% of saline injection at 1 h). In subsequent experiments with Restrict Binge and Naive, Restrict Binge had reduced corticosterone (Restrict Binge: 266±25; Naive: 494±36 ng/ml) and less feeding suppression (Restrict Binge: 81±12, Naive: 50±11% of non-restraint intake at 30 min) following restraint stress (1 h). Dietary-induced binge eating in Restrict Binge was not altered by a dorsal noradrenergic bundle lesion caused by N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4), but frontal cortex norepinephrine was positively correlated with the average 30-min intake post-lesion (0.69; p<0.01). In a separate set of animals, single-unit in vivo electrophysiological recording of locus coeruleus–norepinephrine neural activity demonstrated reduced sensory-evoked response as a consequence of the Restrict Binge schedule (Restrict Binge: 8.1±0.67, Naive: 11.9±1.09 Hz). These results, which suggest that a consequence of dietary-induced binge eating is to attenuate the responsiveness of the brain norepinephrine system, will further our understanding of how highly palatable foods dampen the stress neuraxis.