Adaptation to a high-fat diet leads to hyperphagia and diminished sensitivity to cholecystokinin in rats

Manipulation of feeding patterns in high fat diet fed rats improves microbiota composition dynamics, inflammation and gut-brain signaling

Chronic consumption of high fat (HF) diets has been shown to increase meal size and meal frequency in rodents, resulting in overeating. Reducing meal frequency and establishing periods of fasting, independently of caloric intake, may improve obesity-associated metabolic disorders. Additionally, diet-driven changes in microbiota composition have been shown to play a critical role in the development and maintenance of metabolic disorders. In this study, we used a pair-feeding paradigm to reduce meal frequency and snacking episodes while maintaining overall intake and body weight in HF fed rats. We hypothesized that manipulation of feeding patterns would improve microbiota composition and metabolic outcomes. Male Wistar rats were placed in three groups consuming either a HF, low fat diet (LF, matched for sugar), or pair-fed HF diet for 7 weeks (n = 11-12/group). Pair-fed animals received the same amount of food consumed by the HF fed group once daily before dark onset (HF-PF). Rats underwent oral glucose tolerance and gut peptide cholecystokinin sensitivity tests. Bacterial DNA was extracted from the feces collected during both dark and light cycles and sequenced via Illumina MiSeq sequencing of the 16S V4 region. Our pair-feeding paradigm reduced meal numbers, especially small meals in the inactive phase, without changing total caloric intake. This shift in feeding patterns reduced relative abundances of obesity-associated bacteria and maintained circadian fluctuations in microbial abundances. These changes were associated with improved gastrointestinal (GI) function, reduced inflammation, and improved glucose tolerance and gut to brain signaling. We concluded from these data that targeting snacking may help improve metabolic outcomes, independently of energy content of the diet and hyperphagia.

Transfer with microbiota from lean donors prevents excessive weight gain and restores gut-brain vagal signaling in obese rats maintained on a high fat diet

Background

The collection of microorganisms, mainly bacteria, which live in the gastrointestinal (GI) tract are collectible known as the gut microbiota. GI bacteria play an active role in regulation of the host's immune system and metabolism, as well as certain pathophysiological processes. Diet is the main factor modulating GI microbiota composition and recent studies have shown that high fat (HF) diets induce detrimental changes, known as dysbiosis, in the GI bacterial makeup. HF diet induced microbiota dysbiosis has been associated with structural and functional changes in gut-brain vagally mediated signaling system, associated with overeating and obesity. Although HF-driven changes in microbiota composition are sufficient to alter vagal signaling, it is unknown if restoring normal microbiota in obesity can improve gut-brain signaling and metabolic outcomes. In this study, we evaluated the effect of lean gut microbiota transfer in obese, vagally compromised, rats on gut-brain communication, food intake, and body weight. Male Sprague-Dawley rats were maintained on regular chow, or 45% HF diet for nine weeks followed by three weeks of microbiota depletion using an antibiotic cocktail. The animals were then divided into four groups (n=10 each): LF - control group on regular chow, LF-LF - chow fed animals that received antibiotics and microbiota from chow fed animals, HF-LF - HF fed animals that received microbiota from chow fed animals, and HF-HF - HF fed animals that received microbiota from HF fed animals. Animals were gavaged with donor microbiota for three consecutive days on week one and once a week thereafter for three more weeks. HF-LF animals received inulin as a prebiotic to aid the establishment of the lean microbiome.

Results

We found that transferring a LF microbiota to HF fed animals (HF-LF) reduced caloric intake during the light phase when compared with HF-HF rats and prevented additional excessive weight gain. We did not observe significant changes in the density of vagal afferents terminating in the brainstem among the groups, however, HF-LF animals displayed an increase in postprandial activation of both primary sensory neurons innervating the GI tract and brainstem secondary neurons.

Conclusions

We concluded from these data that normalizing microbiota composition in obese rats improves gut-brain communication and restores normal feeding patterns which was associated with a reduction in weight gain.

Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling

Western diet (WD) consumption during early life developmental periods is associated with impaired memory function, particularly for hippocampus (HPC)-dependent processes. We developed an early life WD rodent model associated with long-lasting HPC dysfunction to investigate the neurobiological mechanisms mediating these effects. Rats received either a cafeteria-style WD (ad libitum access to various high-fat/high-sugar foods; CAF) or standard healthy chow (CTL) during the juvenile and adolescent stages (postnatal days 26-56). Behavioral and metabolic assessments were performed both before and after a healthy diet intervention period beginning at early adulthood. Results revealed HPC-dependent contextual episodic memory impairments in CAF rats that persisted despite the healthy diet intervention. Given that dysregulated HPC acetylcholine (ACh) signaling is associated with memory impairments in humans and animal models, we examined protein markers of ACh tone in the dorsal HPC (HPCd) in CAF and CTL rats. Results revealed significantly lower protein levels of vesicular ACh transporter in the HPCd of CAF vs. CTL rats, indicating chronically reduced ACh tone. Using intensity-based ACh sensing fluorescent reporter (iAChSnFr) in vivo fiber photometry targeting the HPCd, we next revealed that ACh release during object-contextual novelty recognition was highly predictive of memory performance and was disrupted in CAF vs. CTL rats. Neuropharmacological results showed that alpha 7 nicotinic ACh receptor agonist infusion in the HPCd during training rescued memory deficits in CAF rats. Overall, these findings reveal a functional connection linking early life WD intake with long-lasting dysregulation of HPC ACh signaling, thereby identifying an underlying mechanism for WD-associated memory impairments.

Palm-based tocotrienol-rich fraction (TRF) supplementation modulates cardiac sod1 expression, fxr target gene expression, and tauro-conjugated bile acid levels in aleptinemic mice fed a high-fat diet

Tocotrienol-rich fraction (TRF) has been reported to protect the heart from oxidative stress-induced inflammation. It is, however, unclear whether the protective effects of TRF against oxidative stress involve the activation of farnesoid X receptor (fxr), a bile acid receptor, and the regulation of bile acid metabolites. In the current study, we investigated the effects of TRF supplementation on antioxidant activities, expression of fxr and its target genes in cardiac tissue, and serum untargeted metabolomics of high-fat diet-fed mice. Mice were divided into high-fat diet (HFD) with or without TRF supplementation (control) for 6 weeks. At the end of the intervention, body weight (BW), waist circumference (WC), and random blood glucose were measured. Heart tissues were collected, and the gene expression of sod1, sod2, gpx, and fxr and its target genes shp and stat3 was determined. Serum was subjected to untargeted metabolomic analysis using UHPLC-Orbitrap. In comparison to the control, the WC of the TRF-treated group was higher (p >0.05) than that of the HFD-only group, in addition there was no significant difference in weight or random blood glucose level. Downregulation of sod1, sod2, and gpx expression was observed in TRF-treated mice; however, only sod1 was significant when compared to the HFD only group. The expression of cardiac shp (fxr target gene) was significantly upregulated, but stat3 was significantly downregulated in the TRF-treated group compared to the HFD-only group. Biochemical pathways found to be influenced by TRF supplementation include bile acid secretion, primary bile acid biosynthesis, and biotin and cholesterol metabolism. In conclusion, TRF supplementation in HFD-fed mice affects antioxidant activities, and more interestingly, TRF also acts as a signaling molecule that is possibly involved in several bile acid-related biochemical pathways accompanied by an increase in cardiac fxr shp expression. This study provides new insight into TRF in deregulating bile acid receptors and metabolites in high-fat diet-fed mice.

Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling

Western diet (WD) consumption during development yields long-lasting memory impairments, yet the underlying neurobiological mechanisms remain elusive. Here we developed an early life WD rodent model to evaluate whether dysregulated hippocampus (HPC) acetylcholine (ACh) signaling, a pathology associated with memory impairment in human dementia, is causally-related to WD-induced cognitive impairment. Rats received a cafeteria-style WD (access to various high-fat/high-sugar foods; CAF) or healthy chow (CTL) during the juvenile and adolescent periods (postnatal days 26-56). Behavioral, metabolic, and microbiome assessments were performed both before and after a 30-day healthy diet intervention beginning at early adulthood. Results revealed CAF-induced HPC-dependent contextual episodic memory impairments that persisted despite healthy diet intervention, whereas CAF was not associated with long-term changes in body weight, body composition, glucose tolerance, anxiety-like behavior, or gut microbiome. HPC immunoblot analyses after the healthy diet intervention identified reduced levels of vesicular ACh transporter in CAF vs. CTL rats, indicative of chronically reduced HPC ACh tone. To determine whether these changes were functionally related to memory impairments, we evaluated temporal HPC ACh binding via ACh-sensing fluorescent reporter in vivo fiber photometry during memory testing, as well as whether the memory impairments could be rescued pharmacologically. Results revealed dynamic HPC ACh binding during object-contextual novelty recognition was highly predictive of memory performance and was disrupted in CAF vs. CTL rats. Further, HPC alpha-7 nicotinic receptor agonist infusion during consolidation rescued memory deficits in CAF rats. Overall, these findings identify dysregulated HPC ACh signaling as a mechanism underlying early life WD-associated memory impairments.

The administration of Exendin-4 and CCK affects food intake differentially in female and male rats tested on an alternate day fasting paradigm

Alternate day fasting (ADF) which involves the repetition of a 2-day cycle of a day of free access to food followed by a day of limited or no access to food, is an effective dietary intervention for weight loss in both humans and rats. We have previously reported that when presented with a high energy (HE) and standard chow diet, rats maintained on an ADF schedule displayed decreased HE diet preference compared to controls. Both male and female ADF rats increased overall intake of chow. However, this increase was driven by both meal size and meal number for males and only number of meals for females. Administration of cholecystokinin (CCK) or the glucagon-like peptide 1 (GLP-1) receptor agonist Exendin-4 (Ex-4) reduces food intake. It appears that CCK decreases food intake primarily through satiety signals whereas GLP-1 signaling may reduce intake by satiety and reward cues. Here, female and male rats were administered (i.p.) saline, 3.0 µg/kg Ex-4 (3 h before test), 3.0 µg/kg CCK (15 min before test) or a combination of both. Next, all rats were presented 23-h access to both HE diet and chow following food-restriction (ADF) or free access to chow (CON). Compared to saline-control sessions, administration of the combination of Ex-4 and CCK, but not Ex-4 or CCK alone, resulted in a decrease in both HE and chow intake early in the session for male ADF rats but the combination primarily decreased chow diet intake early in the session for female ADF rats. Thus, it appears that under these energy homeostatic conditions, administration of Ex-4 or CCK alone does not affect intake in ADF rats, but the combination produces decreases in feeding that are more than the sum of their individual effects. These findings support a role for the combination of GLP-1 and CCK signaling in the changes in diet preference induced by an alternate day fasting paradigm differentially in female and male rats.

The possible protective role of N-acetyl cysteine on duodenal mucosa of high fat diet and orlistat treated adult male albino rats and the active role of tumor necrosis factor α (TNFα) and Interleukin 6 (IL6) (histological and biochemical study)

BACKGROUND

Obesity is a major universal health issue linked to a majority of illness.

AIM

To evaluate the histological and biochemical changes occurred in the duodenal mucosa of high fat diet HFD and orlistat fed rats and to assess the possible protective role of N-acetyl cysteine NAC supplementation.

MATERIAL AND METHOD

Sixty male albino rats weighing 180-200 g were classified randomly into control group I and three experimental groups (HFD group II, HFD + orlistat group III, and HFD + orlistat + NAC group IV). All experimental groups received HFD alone/and treatment for 6 weeks. Group III received orlistat (32 mg/kg/day) before meals and group IV received the same regimen as group III in addition to NAC (230 mg/kg/day) after meals. After completion of the experiment, duodenal sections were processed for histological examination, oxidative stress parameters, and semiqualitative real time PCR for proinflammatory mediators TNFα and IL6 evaluation. Also, plasma lipid parameters were assessed and morphometric duodenal results were analyzed statistically.

RESULTS

By histological examination of HFD and (HFD + orlistat) groups, we found severe to moderate duodenal structural disturbances, increased goblet cells, collagen fibers, and BAX and iNOS immunostaining. By Biochemical examination, both groups showed increased proinflammatory markers level (TNFα and IL6) with decreased all antioxidant parameters and increased MDA. Moreover, NAC treatment in group IV significantly reduced all structural changes, levels of proinflammatory mediators and increased all antioxidant parameter levels and decreased MDA.

CONCLUSION

All findings elucidated that NAC could be accounted to be a useful drug for protection of duodenal mucosa of HFD and orlistat treated animals.

Vitamin D mitigates diabetes-associated metabolic and cognitive dysfunction by modulating gut microbiota and colonic cannabinoid receptor 1

INTRODUCTION

Obesity is associated with elevated endocannabinoid tone, gut dysbiosis, and inflammation predisposing to diabetes. The endocannabinoid system mediates the effects of gut microbiota and regulates the gut barrier integrity. We examined the effects of vitamin D (VD) on colonic cannabinoid receptor 1(CB1R), tight junction proteins, gut dysbiosis, metabolic and cognitive dysfunction in a model of type 2 diabetes compared with metformin.

METHODS

Rats received high-fat, high-sucrose diet (HFSD) and either VD (500 IU/kg/day; p.o.), or metformin (200 mg/kg/day; p.o.) for 8 weeks. After 6 weeks, streptozotocin (STZ) (40 mg/kg; i.p) was injected. Behavioral, cognitive, and metabolic assessments were carried out. Finally, fecal, blood, and tissue samples were collected to examine Bacteroidetes/Firmicutes ratio, colonic CB1R, zonula occludens-1 (ZO-1), occludin, and Toll-like receptor 4 (TLR4); serum lipopolysaccharides (LPS), peptidoglycan (PGN), tumor necrosis factor-alpha (TNF-ɑ), glucagon-like peptide-1 (GLP-1), lipids, and VD; hippocampal brain-derived neurotrophic factor (BDNF) and inflammatory markers.

RESULTS

VD ameliorated HFSD/STZ-induced dysbiosis/gut barrier dysfunction as indicated by lower circulating LPS, PGN and TNF-ɑ levels, likely by downregulating colonic CB1R and upregulating ZO-1 and occludin expressions. Additionally, VD suppressed HFSD/STZ-induced hyperglycemia, hyperinsulinemia, dyslipidemia, and hippocampal neuroinflammation. These changes culminated in improved glycemic control and cognitive function. VD was more effective than metformin in decreasing serum LPS and TNF-ɑ levels; whereas metformin resulted in better glycemic control.

CONCLUSION

Targeting gut microbiota by VD could be a successful strategy in the treatment of diabetes and associated cognitive deficit. The crosstalk between VD axis and the endocannabinoid system needs further exploration.

Crème de la Créature: Dietary Influences on Behavior in Animal Models

In humans, alterations in cognitive, motivated, and affective behaviors have been described with consumption of processed diets high in refined sugars and saturated fats and with high body mass index, but the causes, mechanisms, and consequences of these changes remain poorly understood. Animal models have provided an opportunity to answer these questions and illuminate the ways in which diet composition, especially high-levels of added sugar and saturated fats, contribute to brain physiology, plasticity, and behavior. Here we review findings from invertebrate (flies) and vertebrate models (rodents, zebrafish) that implicate these diets with changes in multiple behaviors, including eating, learning and memory, and motivation, and discuss limitations, open questions, and future opportunities.

Gastrointestinal peptides in eating-related disorders

Food intake is tightly controlled by homeostatic signals sensitive to metabolic need for the regulation of body weight. This review focuses on the peripherally-secreted gastrointestinal peptides (i.e., ghrelin, cholecystokinin, glucagon-like peptide 1, and peptide tyrosine tyrosine) that contribute to the control of appetite and discusses how these peptides or the signals arising from their release are disrupted in eating-related disorders across the weight spectrum, namely anorexia nervosa, bulimia nervosa, and obesity, and whether they are normalized following weight restoration or weight loss treatment. Further, the role of gut peptides in the pathogenesis and treatment response in human weight conditions as identified by rodent models are discussed. Lastly, we review the incretin- and hormone-based pharmacotherapies available for the treatment of obesity and eating-related disorders.

Microbiota's Role in Diet-Driven Alterations in Food Intake: Satiety, Energy Balance, and Reward

The gut microbiota plays a key role in modulating host physiology and behavior, particularly feeding behavior and energy homeostasis. There is accumulating evidence demonstrating a role for gut microbiota in the etiology of obesity. In human and rodent studies, obesity and high-energy feeding are most consistently found to be associated with decreased bacterial diversity, changes in main phyla relative abundances and increased presence of pro-inflammatory products. Diet-associated alterations in microbiome composition are linked with weight gain, adiposity, and changes in ingestive behavior. There are multiple pathways through which the microbiome influences food intake. This review discusses these pathways, including peripheral mechanisms such as the regulation of gut satiety peptide release and alterations in leptin and cholecystokinin signaling along the vagus nerve, as well as central mechanisms, such as the modulation of hypothalamic neuroinflammation and alterations in reward signaling. Most research currently focuses on determining the role of the microbiome in the development of obesity and using microbiome manipulation to prevent diet-induced increase in food intake. More studies are necessary to determine whether microbiome manipulation after prolonged energy-dense diet exposure and obesity can reduce intake and promote meaningful weight loss.

The critical role of CCK in the regulation of food intake and diet-induced obesity

In 1973, Gibbs, Young, and Smith showed that exogenous cholecystokinin (CCK) administration reduces food intake in rats. This initial report has led to thousands of studies investigating the physiological role of CCK in regulating feeding behavior. CCK is released from enteroendocrine I cells present along the gastrointestinal (GI) tract. CCK binding to its receptor CCK1R leads to vagal afferent activation providing post-ingestive feedback to the hindbrain. Vagal afferent neurons' (VAN) sensitivity to CCK is modulated by energy status while CCK signaling regulates gene expression of other feeding related signals and receptors expressed by VAN. In addition to its satiation effects, CCK acts all along the GI tract to optimize digestion and nutrient absorption. Diet-induced obesity (DIO) is characterized by reduced sensitivity to CCK and every part of the CCK system is negatively affected by chronic intake of energy-dense foods. EEC have recently been shown to adapt to diet, CCK1R is affected by dietary fats consumption, and the VAN phenotypic flexibility is lost in DIO. Altered endocannabinoid tone, changes in gut microbiota composition, and chronic inflammation are currently being explored as potential mechanisms for diet driven loss in CCK signaling. This review discusses our current understanding of how CCK controls food intake in conditions of leanness and how control is lost in chronic energy excess and obesity, potentially perpetuating excessive intake.

Intact vagal gut-brain signalling prevents hyperphagia and excessive weight gain in response to high-fat high-sugar diet

Aim

The tools that have been used to assess the function of the vagus nerve lack specificity. This could explain discrepancies about the role of vagal gut‐brain signalling in long‐term control of energy balance. Here we use a validated approach to selectively ablate sensory vagal neurones that innervate the gut to determine the role of vagal gut‐brain signalling in the control of food intake, energy expenditure and glucose homoeostasis in response to different diets.

Methods

Rat nodose ganglia were injected bilaterally with either the neurotoxin saporin conjugated to the gastrointestinal hormone cholecystokinin (CCK), or unconjugated saporin as a control. Food intake, body weight, glucose tolerance and energy expenditure were measured in both groups in response to chow or high‐fat high‐sugar (HFHS) diet. Willingness to work for fat or sugar was assessed by progressive ratio for orally administered solutions, while post‐ingestive feedback was tested by measuring food intake after an isocaloric lipid or sucrose pre‐load.

Results

Vagal deafferentation of the gut increases meal number in lean chow‐fed rats. Switching to a HFHS diet exacerbates overeating and body weight gain. The breakpoint for sugar or fat solution did not differ between groups, suggesting that increased palatability may not drive HFHS‐induced hyperphagia. Instead, decreased satiation in response to intra‐gastric infusion of fat, but not sugar, promotes hyperphagia in CCK‐Saporin‐treated rats fed with HFHS diet.

Conclusions

We conclude that intact sensory vagal neurones prevent hyperphagia and exacerbation of weight gain in response to a HFHS diet by promoting lipid‐mediated satiation.

Desacetyl-α-MSH and α-MSH have sex specific interactions with diet to influence mouse gut morphology, metabolites and microbiota

The melanocortin peptides have an important role in regulating body weight and appetite. Mice that lack the desacetyl-α-MSH and α-MSH peptides (Pomctm1/tm1) develop obesity. This effect is exacerbated by a high fat diet (HFD). However, development of obesity in female Pomctm1/tm1 mice during chronic HFD conditions is not fully accounted for by the increased energy intake. We hypothesized that the protection against chronic HFD-induced obesity imparted by MSH peptides in females is mediated by sex-specific alterations in the gut structure and gut microbiota. We determined that female WT mice had reduced jejunum villus length and increased crypt depth in response to chronic HFD. WT males and Pomctm1/tm1 mice lacked this adaptation to a chronic HFD. Both Pomctm1/tm1 genotype and chronic HFD were significantly associated with gut microbiota composition. Sex-specific associations between Pomctm1/tm1 genotype and gut microbiota were observed in the presence of a chronic HFD. Pomctm1/tm1 females had significantly reduced fecal acetate and propionate concentrations when compared to WT females. We conclude that MSH peptides influence jejunum villus length, crypt depth and the structure of the gut microbiota. These effects favor reduced nutrient absorption and occur in addition to the recognized roles of desacetyl-α-MSH and α-MSH peptides in appetite control.

Gut microbiota composition modulates inflammation and structure of the vagal afferent pathway

Vagal afferent neurons (VAN), located in the nodose ganglion (NG) innervate the gut and terminate in the nucleus of solitary tract (NTS) in the brainstem. They are the primary sensory neurons integrating gut-derived signals to regulate meal size. Chronic high-fat diet (HFD) consumption impairs vagally mediated satiety, resulting in overfeeding. There is evidence that HFD consumption leads to alterations in both vagal nerve function and structural integrity. HFD also leads to marked gut microbiota dysbiosis; in rodent models, dysbiosis is sufficient to induce weight gain. In this study, we investigated the effect of microbiota dysbiosis on gut-brain vagal innervation independently of diet. To do so, we recolonized microbiota-depleted rats with gastrointestinal (GI) contents isolated from donor animals fed either a HFD (45 or 60% fat) or a low fat diet (LFD, 13% fat). We used two different depletion models while maintaining the animals on LFD: 1) conventionally raised Fischer and Wistar rats that underwent a depletion paradigm using an antibiotic cocktail and 2) germ free (GF) raised Fischer rats. Following recolonization, receiver animals were designated as ConvLF and ConvHF. Fecal samples were collected throughout these studies and analyzed via 16S Illumina sequencing. In both models, bacteria that were identified as characteristic of HFD were successfully transferred to recipient animals. Three weeks post-colonization, ConvHF rats showed significant increases in ionized calcium-binding adapter molecule-1 (Iba1) positive immune cells in the NG compared to ConvLF animals. Additionally, using isolectin B4 (IB4) staining to identify c-fibers, we found that, compared to ConvLF animals, ConvHF rats displayed decreased innervation at the level of the medial NTS; c-fibers at this level are believed to be primarily of vagal origin. This alteration in vagal structure was associated with a loss in satiety induced by the gut peptide cholecystokinin (CCK). Increased presence of immunocompetent Iba1⁺ cells along the gut-brain axis and alterations in NTS innervation were still evident in ConvHF rats compared to ConvLF animals 12 weeks post-colonization and were associated with increases in food intake and body weight (BW). We conclude from these data that microbiota dysbiosis can alter gut-brain vagal innervation, potentially via recruitment and/or activation of immune cells.

Consumption of Spinacia Oleracea (spinach) and aerobic exercise controls obesity in rats by an inhibitory action on pancreatic lipase

Context: Spinaciaoleracea (spinach) is abundant in antioxidant phytoconstituents, termed as the natural antioxidant mixture (NAO).Objective: This study evaluates the anti-hyperlipidemicand anti-obesity effects of an antioxidant-rich extract of Spinaciaoleracea (NAOE) and aerobic exercise (AE) in rats fed with high fat diet (HFD).Methods: Rats received NAOE (200 and 400 mg/kg), the standard drug orlistat (10 mg/kg), AE and NAOEAE (NAOE 400 mg/kg + AE) daily with HFD for 21 d.Results: Orlistat, NAOE and NAOEAE treatments to HFD-fed rats significantly reduced the HFD-elevated food intake, weight gain, pancreatic lipase activity and lipid peroxidation, and successfully restored the HFD-skewed lipid profile and antioxidant levels.Conclusions: It may be concluded that NAOE exhibited a promising anti-hyperlipidemic effect by its inhibitory action on pancreatic lipase. The combination treatment NAOEAE produced the best results indicating the essential role of exercise along with consumption of antioxidant-rich foods in maintaining a normal lipid profile and controlling obesity.

Resveratrol attenuates metabolic, sperm, and testicular changes in adult Wistar rats fed a diet rich in lipids and simple carbohydrates

High-fat diets affect male reproduction and sexual function. Therefore, we evaluated the effects of prolonged resveratrol administration on the metabolic, sperm, and testicular parameters of rats fed a cafeteria diet. Male Wistar rats were divided at weaning into control (C, n = 20) and cafeteria (CAF, n = 16) groups. At 3 months, half of them were given daily supplementations of resveratrol (C-R, n = 10; CAF-R, n = 8) at a dosage of 30 mg kg^-1 body mass for 2 months. Animals were killed at 5 months of age, and blood, spermatozoa, and testes were collected for further analysis. Data were analyzed by one-way ANOVA, and P < 0.05 was considered statistically significant. The CAF diet promoted hyperglycemia (P < 0.0001), and treatment with resveratrol reversed this condition (P < 0.0001). The CAF diet reduced sperm viability and motility, while resveratrol improved these parameters (P < 0.05). Regarding testicular morphology, the height of the seminiferous epithelium was reduced in the CAF group compared with that of the C group (P = 0.0007). Spermatogenic cell proliferation was also reduced in the CAF group compared with that of the C group. However, the CAF-R showed an increase in cell proliferation rate compared with that of the untreated CAF group (P = 0.0024). Although it did not modify body mass, the consumption of a CAF diet promoted hyperglycemia, adverse testicular morphology remodeling, and abnormal sperm, which were attenuated by treatment with resveratrol, thus suggesting a protective effect of this antioxidant on spermatogenesis.

A herbal premix containing Macrotyloma uniflorum, ginger, and whey curtails obesity in rats fed a high-fat diet by a novel mechanism

The present study designed and evaluated a polyherbal premix comprising Macrotyloma uniflorum, whey protein, Zingiber officinale, and Mentha piperita. Animals were fed a high-fat diet (HFD) for 30 days and were daily administered the premix (1.5 g/kg) in milk (PM) and water (PW), aerobic exercise (AE), premix in milk and water along with AE (PMAE and PWAE), ferulic acid (100 mg/kg), and the reference drug fluoxetine (6 mg/kg). All treatments showed significant reduction in food intake, weight gain, abdominal circumference, and body mass index compared with their initial values. All treatments generated a faster peak of the satiety marker cholecystokinin compared with the HFD group and control groups; PMAE and PWAE exhibited sustained satiety. The HFD-elevated blood glucose levels were significantly attenuated on the 30th day by all treatments when compared with their 15th day and basal values; PMAE exhibited the best results. All treatments significantly attenuated the HFD-elevated serum insulin, homeostasis model assessment of insulin resistance, C-reactive protein, triglycerides, total cholesterol, very-low-density lipoprotein, and low-density lipoprotein levels and significantly restored the HFD-depleted high-density lipoprotein and adiponectin levels. HFD-elevated thiobarbituric acid reactive substances values were attenuated successfully and the HFD-depleted reduced glutathione, superoxide dismutase, and catalase levels were significantly restored by all treatments. The histological findings corroborated the biochemical results. Novelty The polyherbal premix brought about appetite regulation and induction of satiety to control obesity in HFD-fed rats through homeostasis of energy metabolism. The premix along with exercise is a complete way to combat obesity.

Dietary fatty acid content influences the expression of genes involved in the lipid turnover and inflammation in mouse colon and spleen

BACKGROUND

Dietary interventions can improve gastrointestinal (GI) symptoms. We determined the effects of fatty acids (FAs) supplementation with medium- and long-chain saturated FAs on mouse GI motility and correlated them with the expression of genes for free FA receptors (FFAR)1-4, FA binding protein 4 (FABP4) and inflammation.

METHODS

Forty-eight BalbC were assigned to: standard diet (STD), diet rich in medium-chain saturated FAs (COCO) and long-chain saturated FAs (HF) (7% by weight). Body weight (BW) and food intake (FI) were monitored for 8-weeks. GI motility was determined by fecal pellet output (FPO) and colon bead expulsion tests. FABP4 inhibitor, BMS309403 (1mg/kg, ip) was injected to half of each group 2 days/week. mRNA expression of FABP4, (FFAR)1-4, and pro-inflammatory cytokines were measured in colonic and splenic tissues using real-time PCR.

RESULTS

COCO and HF decreased FI. COCO accelerated overall GI transit (p<0.05). COCO increased the mRNA expression of FFAR2 (p<0.001) and TNFα (p<0.01); HF increased the expression of FABP4 and FFAR4 (p<0.05), and FFAR2 (p<0.001) in the colon, and decreased FFAR1 and FFAR4 (p<0.001), TNFα (p<0.01) and IL-1β (p<0.05) in splenic tissues. BMS309403 decreased the FI and delayed colonic transit in STD+BMS and COCO+BMS vs. STD (p<0.05). HF+BMS increased colonic expression of FFAR3 (p<0.01), TNFα (p<0.01), IL-6 (p<0.01), and reduced FFAR4 (p<0.05); COCO+BMS decreased TNFα (p<0.01).

CONCLUSION

Diversification in the dietary lipid content affected GI motility in mice and the expression of FFARs and pro-inflammatory cytokines in vivo.

High Fat Diet Attenuates Cholecystokinin-Induced cFos Activation of Prolactin-Releasing Peptide-Expressing A2 Noradrenergic Neurons in the Caudal Nucleus of the Solitary Tract

Cholecystokinin (CCK) released from the small intestine increases the activity of vagal afferents that relay satiety signals to the caudal nucleus of the solitary tract (cNTS). A caudal subset of A2 noradrenergic neurons within the cNTS that express prolactin-releasing peptide (PrRP) have been proposed to mediate CCK-induced satiety. However, the ability of exogenous CCK to activate cFos expression by PrRP neurons has only been reported in rats and mice after a very high dose (i.e., 50 μg/kg BW) that also activates the hypothalamic-pituitary-adrenal stress axis. The present study examined the ability of a much lower CCK dose (1.0 µg/kg BW, i.p) to activate PrRP-positive neurons in the rat cNTS. We further examined whether maintenance of rats on high fat diet (HFD; 45% kcal from fat) alters CCK-induced activation of PrRP neurons, since HFD blunts the ability of CCK to suppress food intake. Rats maintained on HFD for 7 weeks consumed more kcal and gained more BW compared to rats maintained on Purina chow (13.5% kcal from fat). CCK-treated rats displayed increased numbers of cFos-positive cNTS neurons compared to non-injected and saline-injected controls, with no effect of diet. In chow-fed rats, a significantly larger proportion of PrRP neurons were activated after CCK treatment compared to controls; conversely, CCK did not increase PrRP neuronal activation in HFD-fed rats. Collectively, these results indicate that a relatively low dose of exogenous CCK is sufficient to activate PrRP neurons in chow-fed rats, and that this effect is blunted in rats maintained for several weeks on HFD.

High-fat diet-induced vagal afferent dysfunction via upregulation of 2-pore domain potassium TRESK channel

Research shows that rats and humans on a high-fat diet (HFD) are less sensitive to satiety signals known to act via vagal afferent pathways. We hypothesize that HFD causes an upregulation of 2-pore domain potassium channels, resulting in hyperpolarization of nodose ganglia (NG) and decreased vagal response to satiety signals, which contribute to hyperphagia. We show that a 2-week HFD caused an upregulation of 2-pore domain TWIK-related spinal cord K+ (TRESK) and TWIK-related acid-sensitive K+ 1 (TASK1) channels by 330% ± 50% and 60% ± 20%, respectively, in NG. Patch-clamp studies of isolated NG neurons demonstrated a decrease in excitability. In vivo single-unit NG recordings showed that a 2-week HFD led to a 55% reduction in firing frequency in response to CCK-8 or leptin stimulation. NG electroporation with TRESK siRNA restored NG responsiveness to CCK-8 and leptin. Rats fed a 2-week HFD consumed ~40% more calories compared with controls. Silencing NG TRESK but not TASK1 channel expression in HFD-fed rats restored normal calorie consumption. In conclusion, HFD caused upregulation of TRESK channels, resulting in NG hyperpolarization and decreased vagal responsiveness to satiety signals. This finding provides a pharmacological target to prevent or treat HFD-induced hyperphagia.

Macronutrient intake and physical activity levels in individuals with and without metabolic syndrome: An observational study in an urban population

BACKGROUND

We aimed to compare dietary macronutrient intake and physical activity level (PAL) between community-based samples of Iranian adults with metabolic syndrome (MetS+) and without metabolic syndrome (MetS-).

METHODS

This cross-sectional study was conducted among 3800 men and women aged 35-65 years. The International Diabetes Federation (IDF) criteria were used to define MetS. A 24-hour recall was used to evaluate dietary intake. The James and Schofield human energy requirements equations were used to calculate PAL and questions were categorized into time spent on activities during work (including housework), during non-work time, and in bed.

RESULTS

The mean ± standard deviation (SD)age of the MetS+ and MetS- subjects was, respectively, 48.8 ± 7.8 years (521 men and 1178 women) and 47.6 ± 7.5 years (714 men and 1222 women) (P = 0.930). The mean energy intake was higher in the MetS+ men compared with MetS- men (1977.4 ± 26.6 vs. 1812.7 ± 21.7 Kcal; P < 0.001). Crude and energy-adjusted intake from total fat was lower in MetS+ women compared with MetS- women (both P < 0.010). PALs were lower in MetS+ compared with MetS- participants (P < 0.001). After adjusting for confounders, no significant association was observed between the intake of individual macronutrients and MetS. In contrast, PAL was inversely associated with the incidence of MetS [OR = 0.34 (95% CI: 0.17-0.57); P < 0.001].

CONCLUSION

In the current study, there was an inverse relationship between PAL and the risk of MetS, but no association between individual dietary macronutrients intake and the incidence of MetS.

Effects of Sleeve Gastrectomy on Blood Pressure and the Renal Renin-Angiotensin System in Rats with Diet-Induced Obesity

OBJECTIVE

Sleeve gastrectomy (SG) has been reported to decrease blood pressure (BP), although the reason has not been revealed. The present study aimed to establish the reason why SG decreases BP.

METHODS

Male Sprague-Dawley rats were subjected to surgical (sham operation or SG) and dietary interventions (fed a normal diet or high-fat diet ad libitum or fed by pair-feeding [PF]). Systolic BP (SBP), urinary sodium excretion, and endocrine parameters were examined 4 weeks after surgery.

RESULTS

Both SG and PF rats had reduced body weight compared with SO rats fed normal diet or high-fat diet ad libitum. SG rats exhibited a reduction in SBP compared with PF, which was associated with a reduction in renal renin, angiotensin II, and catechol-O-methyltransferase levels (P < 0.01 for each). SG increased plasma cholecystokinin (CCK) levels compared with PF (P < 0.0001 for each), whereas glucagon-like peptide 1 and peptide YY were not changed in fasting. Exogenous administration of CCK reduced renal catechol-O-methyltransferase (P = 0.0233), renin (P < 0.0001), and angiotensin II (P < 0.0001) levels and SBP (P = 0.0053).

CONCLUSIONS

SG reduced SBP, at least in part, through suppression of sympathetic nerve action by elevation of CCK, which was followed by suppression of the intrarenal renin-angiotensin system.

Hedonic Eating and the "Delicious Circle": From Lipid-Derived Mediators to Brain Dopamine and Back

Palatable food can be seductive and hedonic eating can become irresistible beyond hunger and negative consequences. This is witnessed by the subtle equilibrium between eating to provide energy intake for homeostatic functions, and reward-induced overeating. In recent years, considerable efforts have been devoted to study neural circuits, and to identify potential factors responsible for the derangement of homeostatic eating toward hedonic eating and addiction-like feeding behavior. Here, we examined recent literature on “old” and “new” players accountable for reward-induced overeating and possible liability to eating addiction. Thus, the role of midbrain dopamine is positioned at the intersection between selected hormonal signals involved in food reward information processing (namely, leptin, ghrelin, and insulin), and lipid-derived neural mediators such as endocannabinoids. The impact of high fat palatable food and dietary lipids on endocannabinoid formation is reviewed in its pathogenetic potential for the derangement of feeding homeostasis. Next, endocannabinoid signaling that regulates synaptic plasticity is discussed as a key mechanism acting both at hypothalamic and mesolimbic circuits, and affecting both dopamine function and interplay between leptin and ghrelin signaling. Outside the canonical hypothalamic feeding circuits involved in energy homeostasis and the notion of “feeding center,” we focused on lateral hypothalamus as neural substrate able to confront food-associated homeostatic information with food salience, motivation to eat, reward-seeking, and development of compulsive eating. Thus, the lateral hypothalamus-ventral tegmental area-nucleus accumbens neural circuitry is reexamined in order to interrogate the functional interplay between ghrelin, dopamine, orexin, and endocannabinoid signaling. We suggested a pivotal role for endocannabinoids in food reward processing within the lateral hypothalamus, and for orexin neurons to integrate endocrine signals with food reinforcement and hedonic eating. In addition, the role played by different stressors in the reinstatement of preference for palatable food and food-seeking behavior is also considered in the light of endocannabinoid production, activation of orexin receptors and disinhibition of dopamine neurons. Finally, type-1 cannabinoid receptor-dependent inhibition of GABA-ergic release and relapse to reward-associated stimuli is linked to ghrelin and orexin signaling in the lateral hypothalamus-ventral tegmental area-nucleus accumbens network to highlight its pathological potential for food addiction-like behavior.

A cafeteria diet triggers intestinal inflammation and oxidative stress in obese rats

The gastrointestinal alterations associated with the consumption of an obesogenic diet, such as inflammation, permeability impairment and oxidative stress, have been poorly explored in both diet-induced obesity (DIO) and genetic obesity. The aim of the present study was to examine the impact of an obesogenic diet on the gut health status of DIO rats in comparison with the Zucker (fa/fa) rat leptin receptor-deficient model of genetic obesity over time. For this purpose, female Wistar rats (n 48) were administered a standard or a cafeteria diet (CAF diet) for 12, 14·5 or 17 weeks and were compared with fa/fa Zucker rats fed a standard diet for 10 weeks. Morphometric variables, plasma biochemical parameters, myeloperoxidase (MPO) activity and reactive oxygen species (ROS) levels in the ileum were assessed, as well as the expressions of proinflammatory genes (TNF-α and inducible nitric oxide synthase (iNOS)) and intestinal permeability genes (zonula occludens-1, claudin-1 and occludin). Both the nutritional model and the genetic obesity model showed increased body weight and metabolic alterations at the final time point. An increase in intestinal ROS production and MPO activity was observed in the gastrointestinal tracts of rats fed a CAF diet but not in the genetic obesity model. TNF-α was overexpressed in the ileum of both CAF diet and fa/fa groups, and ileal inflammation was associated with the degree of obesity and metabolic alterations. Interestingly, the 17-week CAF group and the fa/fa rats exhibited alterations in the expressions of permeability genes. Relevantly, in the hyperlipidic refined sugar diet model of obesity, the responses to chronic energy overload led to time-dependent increases in gut inflammation and oxidative stress.

Loss of Vagal Sensitivity to Cholecystokinin in Rats Born with Intrauterine Growth Retardation and Consequence on Food Intake

Perinatal malnutrition is associated with low birth weight and an increased risk of developing metabolic syndrome in adulthood. Modification of food intake (FI) regulation was observed in adult rats born with intrauterine growth retardation induced by maternal dietary protein restriction during gestation and maintained restricted until weaning. Gastrointestinal peptides and particularly cholecystokinin (CCK) play a major role in short-term regulation of FI by relaying digestive signals to the hindbrain via the vagal afferent nerve (VAN). We hypothesized that vagal sensitivity to CCK could be affected in rats suffering from undernutrition [low protein (LP)] during fetal and postnatal life, leading to an altered gut-brain communication and impacting satiation. Our aim was to study short-term FI along with signals of appetite and satiation in adult LP rats compared to control rats. The dose-response to CCK injection was investigated on FI as well as the associated signaling pathways activated in nodose ganglia. We showed that LP rats have a reduced first-meal satiety ratio after a fasting period associated to a higher postprandial plasmatic CCK release, a reduced sensitivity to CCK when injected at low concentration and a reduced presence of CCK-1 receptor in nodose ganglia. Accordingly, the lower basal and CCK-induced phosphorylation of calcium/calmodulin-dependent protein kinase in nodose ganglia of LP rats could reflect an under-expressed vanilloid family of transient receptor potential cation channels on VAN. Altogether, the present data demonstrated a reduced vagal sensitivity to CCK in LP rats at adulthood, which could contribute to deregulation of FI reported in this model.

Fermented Barley Supplementation Modulates the Expression of Hypothalamic Genes and Reduces Energy Intake and Weight Gain in Rats

Dietary fiber and proteins are individually known to decrease feeding, but could result greater weight management benefit when both are combined. We hypothesized that supplementing the diet with fermented barley, being rich in both dietary fiber and proteins, could lower energy intake by modulating the mRNA expression level of hypothalamic genes associated with the regulation of feeding behavior and satiety; thereby decreasing body weight gain. To test our hypothesis, four groups of Sprague Dawley rats were arranged in a 2 × 2 factorial design (n = 6), low-fat diet with either guar gum (LFD-G) or fermented barley (LFD-FB) and high-fat diet with either guar gum (HFD-G) or fermented barley (HFD-FB). Using oral gavage, fermented barley was given at a dosage of 1500 mg/kg body weight and guar gum was supplemented in an equivalent quantity to that of the fiber in the fermented barley. After 19 weeks, the fermented barley-supplemented groups showed a significant reduction in energy intake, triglyceride, body weight gain, and serum leptin, compared to the guar gum-supplemented groups in both the low- and high-fat diet groups. Likewise, the anorexigenic gene proopiomelanocortin (POMC) and cocaine and amphetamine-regulated transcript (CART) mRNA level were significantly higher in the fermented barley-supplemented groups compared to the guar gum-supplemented groups in rats fed on both high- and low-fat diets. In conclusion, fermented barley supplementation upregulated hypothalamic POMC/CART, decreased energy intake in both low- and high-fat diet groups, and prevented excessive weight gain in rats.

Role of the vagus nerve in the development and treatment of diet-induced obesity

This review highlights evidence for a role of the vagus nerve in the development of obesity and how targeting the vagus nerve with neuromodulation or pharmacology can be used as a therapeutic treatment of obesity. The vagus nerve innervating the gut plays an important role in controlling metabolism. It communicates peripheral information about the volume and type of nutrients between the gut and the brain. Depending on the nutritional status, vagal afferent neurons express two different neurochemical phenotypes that can inhibit or stimulate food intake. Chronic ingestion of calorie-rich diets reduces sensitivity of vagal afferent neurons to peripheral signals and their constitutive expression of orexigenic receptors and neuropeptides. This disruption of vagal afferent signalling is sufficient to drive hyperphagia and obesity. Furthermore neuromodulation of the vagus nerve can be used in the treatment of obesity. Although the mechanisms are poorly understood, vagal nerve stimulation prevents weight gain in response to a high-fat diet. In small clinical studies, in patients with depression or epilepsy, vagal nerve stimulation has been demonstrated to promote weight loss. Vagal blockade, which inhibits the vagus nerve, results in significant weight loss. Vagal blockade is proposed to inhibit aberrant orexigenic signals arising in obesity as a putative mechanism of vagal blockade-induced weight loss. Approaches and molecular targets to develop future pharmacotherapy targeted to the vagus nerve for the treatment of obesity are proposed. In conclusion there is strong evidence that the vagus nerve is involved in the development of obesity and it is proving to be an attractive target for the treatment of obesity.

Maternal high-fat diet increases independent feeding in pre-weanling rat pups

In laboratory settings, the adult offspring of rodent dams that are maintained on high-fat diet (HFD) before conception and/or during pregnancy/lactation display an increased incidence of obese phenotypic markers, including increased body weight and adiposity, reduced leptin sensitivity, and impaired glucose tolerance. In rat pups raised by dams consuming HFD, these obese markers emerge during the first postnatal week. Since the week-old offspring of HFD dams consume excess amounts of milk during experimental tests of independent feeding (i.e., intake away from the dam), we hypothesized that maternal diet affects suckling and/or independent ingestion by pups in the home-cage environment. In the present study, this hypothesis was tested by conducting detailed analyses of ingestive behaviors expressed by pups in the home cage. Pups raised by dams consuming HFD displayed an earlier onset of independent feeding and more amounts of calorie intake from solid food during the third postnatal week compared to pups raised by dams consuming regular chow, with no diet-related differences in suckling behavior. Independent ingestion by pups in both diet groups was most frequently observed after nursing, with offspring of HFD dams engaged more frequently in post-nursing independent feeding episodes compared to offspring of chow-fed dams, particularly when the prior nursing episode was nutritive (i.e., including milk receipt by pups). We conclude that early-life exposure to HFD enhances the facilitative effect of nutritive suckling on independent feeding in pups, promoting increased caloric intake from solid food in the home-cage environment.

Activation of nuclear factor kappa B pathway and reduction of hypothalamic oxytocin following hypothalamic lesions

Background

Hypothalamic obesity (HO) occurs in patients with tumors and lesions in the medial hypothalamic region. In this study, a hyperphagic rat model of combined medial hypothalamic lesions (CMHL) was used to test which specific inflammatory molecules are involved.

Methods

In order to target specific homeostatic medial hypothalamic nuclei (arcuate, ventromedial, and dorsomedial nuclei), male Sprague-Dawley rats (age of 8 weeks, ~250 g body weight) received four electrolytic lesions or sham surgery. Post-surgery food intake and weight changes were tracked and hypothalamic gene expression for inflammatory molecules as well as anorexigenic peptide oxytocin 7 days and 7 months post-surgery were tested.

Results

Seven days post-surgery, average food intake increased by 23%, and body weight gain had increased by 68%. Toll-like 4 receptor/nuclear factor–κB (TLR4/NF–κB)—pathway was specifically activated in the mediobasal hypothalamus (MBH), resulting in 3-fold higher tumor necrosis factor (TNF)-α, 10-fold higher interleukin (IL) 1-β mRNA levels, and higher expression of suppression of cytokine signaling (SOCS) 3, while oxytocin mRNA levels were significantly reduced in CMHL rats versus sham surgery rats 7 days post-surgery. At 7 months, inflammation was less stimulated in MBH of CMHL rats compared to 7 days post-surgery and SOCS 3 as well as oxytocin mRNA levels were comparable between the two groups.

Conclusion

Medial hypothalamic lesions are associated with strong post-surgery hyperphagia and activation of TLR4/NF–κB—pathway as well as reduced expression of oxytocin in the hypothalamus.

Chronic CNS oxytocin signaling preferentially induces fat loss in high-fat diet-fed rats by enhancing satiety responses and increasing lipid utilization

Based largely on a number of short-term administration studies, growing evidence suggests that central oxytocin is important in the regulation of energy balance. The goal of the current work is to determine whether long-term third ventricular (3V) infusion of oxytocin into the central nervous system (CNS) is effective for obesity prevention and/or treatment in rat models. We found that chronic 3V oxytocin infusion between 21 and 26 days by osmotic minipumps both reduced weight gain associated with the progression of high-fat diet (HFD)-induced obesity and elicited a sustained reduction of fat mass with no decrease of lean mass in rats with established diet-induced obesity. We further demonstrated that these chronic oxytocin effects result from 1) maintenance of energy expenditure at preintervention levels despite ongoing weight loss, 2) a reduction in respiratory quotient, consistent with increased fat oxidation, and 3) an enhanced satiety response to cholecystokinin-8 and associated decrease of meal size. These weight-reducing effects persisted for approximately 10 days after termination of 3V oxytocin administration and occurred independently of whether sucrose was added to the HFD. We conclude that long-term 3V administration of oxytocin to rats can both prevent and treat diet-induced obesity.

Hypothalamic Obesity in Craniopharyngioma Patients: Disturbed Energy Homeostasis Related to Extent of Hypothalamic Damage and Its Implication for Obesity Intervention

Hypothalamic obesity (HO) occurs in patients with tumors and lesions in the medial hypothalamic region. Hypothalamic dysfunction can lead to hyperinsulinemia and leptin resistance. This review is focused on HO caused by craniopharyngiomas (CP), which are the most common childhood brain tumors of nonglial origin. Despite excellent overall survival rates, CP patients have substantially reduced quality of life because of significant long-term sequelae, notably severe obesity in about 50% of patients, leading to a high rate of cardiovascular mortality. Recent studies reported that both hyperphagia and decreased energy expenditure can contribute to severe obesity in HO patients. Recognized risk factors for severe obesity include large hypothalamic tumors or lesions affecting several medial and posterior hypothalamic nuclei that impact satiety signaling pathways. Structural damage in these nuclei often lead to hyperphagia, rapid weight gain, central insulin and leptin resistance, decreased sympathetic activity, low energy expenditure, and increased energy storage in adipose tissue. To date, most efforts to treat HO have shown disappointing long-term success rates. However, treatments based on the distinct pathophysiology of disturbed energy homeostasis related to CP may offer options for successful interventions in the future.

Lipid transport in cholecystokinin knockout mice

Cholecystokinin (CCK) is released in response to lipid feeding and regulates pancreatic digestive enzymes vital to the absorption of nutrients. Our previous reports demonstrated that cholecystokinin knockout (CCK-KO) mice fed for 10 weeks of HFD had reduced body fat mass, but comparable glucose uptake by white adipose tissues and skeletal muscles. We hypothesized that CCK is involved in energy homeostasis and lipid transport from the small intestine to tissues in response to acute treatment with dietary lipids. CCK-KO mice with comparable fat absorption had increased energy expenditure and were resistant to HFD-induced obesity. Using intraduodenal infusion of butter fat and intravenous infusion using Liposyn III, we determined the mechanism of lipid transport from the small intestine to deposition in lymph and adipocytes in CCK-KO mice. CCK-KO mice had delayed secretion of Apo B48-chylomicrons, lipid transport to the lymphatic system, and triglyceride (TG)-derived fatty acid uptake by epididymal fat in response to acute treatment of intraduodenal lipids. In contrast, CCK-KO mice had comparable TG clearance and lipid uptake by white adipocytes in response to TGs in chylomicron-like emulsion. Thus, we concluded that CCK is important for lipid transport and energy expenditure to control body weight in response to dietary lipid feeding.

Effects of 5-aminolevulinic acid on a murine model of diet-induced obesity

The effects of 5-aminolevulinic acid (5-ALA) on obesity were investigated using a murine model (diet-induced obese mice). Diet-induced obese mice were divided into 4 groups: a control group (C group), which was fed a high-fat diet; a low-5-ALA dose (10 mg/kg/day) group (10A group); a moderate-5-ALA dose (30 mg/kg/day) group (30A group); and a high-5-ALA dose (100 mg/kg/day) group (100A group). 5-ALA was administered by mixing the high fat diet for 8 weeks. Body weight increases in the 30A and 100A groups were significantly smaller compared with those of the C group. Body fat measurements by X-ray computed tomography indicated that the 100A group showed a tendency toward low visceral fat quantities during the final week of the study. Visceral fat weights in the 30A and 100A groups were slightly low. The levels of serum alanine aminotransferase (ALT) and total cholesterol (TC) in the 10A group was slightly low, whereas the 30A and 100A groups showed significantly lower ALT and TC values. Liver lipid concentration showed a dose-dependent decrease with ALA. Thus, in this diet-induced obese murine model, administration of 5-ALA had a significantly beneficial impact on the visceral fat, serum ALT and TC, and liver lipid concentration.

Specific role of dietary fat in modifying cardiovascular and locomotor activity 24-h rhythms

Meal-fed conscious rabbits normally exhibit postprandial elevation in blood pressure, heart rate (HR) and locomotor activity, which is abolished by consumption of a high-fat diet (HFD). Here, we assessed whether the cardiovascular changes are attributable to the increased caloric intake due to greater fat content or to hyperphagia. Rabbits were meal-fed during the baseline period then maintained on either an ad libitum normal fat diet (NFD) or ad libitum HFD for 2 weeks. Blood pressure, HR and locomotor activity were measured daily by radio-telemetry alongside food intake and body weight. Caloric intake in rabbits given a NFD ad libitum rose 50% from baseline but there were no changes in cardiovascular parameters. By contrast, HR increased by 10% on the first day of the ad libitum HFD (p < 0.001) prior to any change in body weight while blood pressure increased 7% after 4 d (p < 0.01) and remained elevated. Baseline 24-h patterns of blood pressure and HR were closely associated with mealtime, characterised by afternoon peaks and morning troughs. When the NFD was changed from meal-fed to ad libitum, blood pressure and HR did not change but afternoon activity levels decreased (p < 0.05). By contrast, after 13 d ad libitum HFD, morning HR, blood pressure and activity increased by 20%, 8% and 71%, respectively. Increased caloric intake specifically from fat, but not as a result of hyperphagia, appears to directly modulate cardiovascular homeostasis and circadian patterns, independent of white adipose tissue accumulation.

High-fat diet decreases energy expenditure and expression of genes controlling lipid metabolism, mitochondrial function and skeletal system development in the adipose tissue, along with increased expression of extracellular matrix remodelling- and inflammation-related genes

The aim of the present study was to identify the genes differentially expressed in the visceral adipose tissue in a well-characterised mouse model of high-fat diet (HFD)-induced obesity. Male C57BL/6J mice (n 20) were fed either HFD (189 % of energy from fat) or low-fat diet (LFD, 42 % of energy from fat) for 16 weeks. HFD-fed mice exhibited obesity, insulin resistance, dyslipidaemia and adipose collagen accumulation, along with higher levels of plasma leptin, resistin and plasminogen activator inhibitor type 1, although there were no significant differences in plasma cytokine levels. Energy intake was similar in the two diet groups owing to lower food intake in the HFD group; however, energy expenditure was also lower in the HFD group than in the LFD group. Microarray analysis revealed that genes related to lipolysis, fatty acid metabolism, mitochondrial energy transduction, oxidation-reduction, insulin sensitivity and skeletal system development were down-regulated in HFD-fed mice, and genes associated with extracellular matrix (ECM) components, ECM remodelling and inflammation were up-regulated. The top ten up- or down-regulated genes include Acsm3, mt-Nd6, Fam13a, Cyp2e1, Rgs1 and Gpnmb, whose roles in the deterioration of obesity-associated adipose tissue are poorly understood. In conclusion, the genes identified here provide new therapeutic opportunities for prevention and treatment of diet-induced obesity.

Liver glycogen reduces food intake and attenuates obesity in a high-fat diet-fed mouse model

We generated mice that overexpress protein targeting to glycogen (PTG) in the liver (PTG(OE)), which results in an increase in liver glycogen. When fed a high-fat diet (HFD), these animals reduced their food intake. The resulting effect was a lower body weight, decreased fat mass, and reduced leptin levels. Furthermore, PTG overexpression reversed the glucose intolerance and hyperinsulinemia caused by the HFD and protected against HFD-induced hepatic steatosis. Of note, when fed an HFD, PTG(OE) mice did not show the decrease in hepatic ATP content observed in control animals and had lower expression of neuropeptide Y and higher expression of proopiomelanocortin in the hypothalamus. Additionally, after an overnight fast, PTG(OE) animals presented high liver glycogen content, lower liver triacylglycerol content, and lower serum concentrations of fatty acids and β-hydroxybutyrate than control mice, regardless of whether they were fed an HFD or a standard diet. In conclusion, liver glycogen accumulation caused a reduced food intake, protected against the deleterious effects of an HFD, and diminished the metabolic impact of fasting. Therefore, we propose that hepatic glycogen content be considered a potential target for the pharmacological manipulation of diabetes and obesity.

Fat sensing and metabolic syndrome

Overconsumption of dietary fat contributes to the development of obesity and metabolic syndrome. Recent evidence suggests that high dietary fat may promote these metabolic states not only by providing calories but also by inducing impaired control of energy balance. In normal metabolic states, fat interacts with various organs or receptors to generate signals for the regulation of energy balance. Many of these interactions are impaired by high-fat diets or in obesity, contributing to the development or maintenance of obesity. These impairments may arise largely from fundamental alterations in the hypothalamus where all peripheral signals are integrated to regulate energy balance. This review focuses on various mechanisms by which fat is sensed at different stages of ingestion, circulation, storage, and utilization to regulate food intake, and how these individual mechanisms are altered by high-fat diets or in obesity.

Chronic exposure to low dose bacterial lipopolysaccharide inhibits leptin signaling in vagal afferent neurons

Bacterially derived factors are implicated in the causation and persistence of obesity. Ingestion of a high fat diet in rodents and obesity in human subjects is associated with chronic elevation of low plasma levels of lipopolysaccharide (LPS), a breakdown product of Gram-negative bacteria. The terminals of vagal afferent neurons are positioned within the gut mucosa to convey information from the gut to the brain to regulate food intake and are responsive to LPS. We hypothesized that chronic elevation of LPS could alter vagal afferent signaling. We surgically implanted osmotic mini-pumps that delivered a constant, low-dose of LPS into the intraperitoneal cavity of rats (12.5 μg/kg/hr for 6 weeks). LPS-treated rats developed hyperphagia and showed marked changes in vagal afferent neuron function. Chronic LPS treatment reduced vagal afferent leptin signaling, characterized by a decrease in leptin-induced STAT3 phosphorylation. In addition, LPS treatment decreased cholecystokinin-induced satiety. There was no alteration in leptin signaling in the hypothalamus. These findings offer a mechanism by which a change in gut microflora can promote hyperphagia, possibly leading to obesity.

Vagal afferents are not necessary for the satiety effect of the gut lipid messenger oleoylethanolamide

The endogenous lipid messenger oleoylethanolamide (OEA) inhibits eating and modulates fat metabolism supposedly through the activation of peroxisome proliferator-activated receptor-α (PPARα) and vagal sensory fibers. We tested in adult male rats whether OEA stimulates fatty acid oxidation (FAO) and ketogenesis and whether it increases plasma levels of the satiating gut peptides glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). We also explored whether OEA still inhibits eating after subdiaphragmatic vagal deafferentation (SDA). We found that intraperitoneally injected OEA (10 mg/kg body wt) reduced ( P < 0.05) food intake mainly by increasing meal latency and that this effect was stronger in rats fed a 60% high-fat diet (HFD) than in chow-fed rats. OEA increased ( P < 0.05) postprandial plasma nonesterified fatty acids and β-hydroxybutyrate (BHB) in the hepatic portal vein (HPV) and vena cava (VC) 30 min after injection, which was more pronounced in HFD- than in chow-fed rats. OEA also increased the protein expression of the key ketogenetic enzyme, mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase, in the jejunum of HFD-fed rats, but not in the liver or duodenum of either diet group. Furthermore, OEA decreased GLP-1 and PYY concentrations ( P < 0.05) in the HPV and VC 30 min after administration. Finally, OEA reduced food intake in SDA and sham-operated rats similarly. Our findings indicate that neither intact abdominal vagal afferents nor prandial increases in GLP-1 or PYY are necessary for the satiety effect of OEA. The enhanced FAO and ketogenesis raise the possibility of an involvement of intestine-derived BHB in OEA's satiety effect under certain conditions.

Intraperitoneal CCK and fourth-intraventricular Apo AIV require both peripheral and NTS CCK1R to reduce food intake in male rats

Apolipoprotein AIV (Apo AIV) and cholecystokinin (CCK) are secreted in response to fat consumption, and both cause satiation via CCK 1 receptor (CCK-1R)-containing vagal afferent nerves to the nucleus of the solitary tract (NTS), where Apo AIV is also synthesized. Fasted male Long-Evans rats received ip CCK-8 or fourth-ventricular (i4vt) Apo AIV alone or in combination. Food intake and c-Fos proteins (a product of the c-Fos immediate-early gene) were assessed. i4vt Apo AIV and/or ip CCK at effective doses reduced food intake and activated c-Fos proteins in the NTS and hypothalamic arcuate nucleus and paraventricular nucleus. Blockade of the CCK-1R by i4vt lorglumide adjacent to the NTS attenuated the satiating and c-Fos-stimulating effects of CCK and Apo AIV, alone or in combination. Maintenance on a high-fat diet (HFD) for 10 weeks resulted in weight gain and attenuation of both the behavioral and c-Fos responses to a greater extent than occurred in low-fat diet-fed and pair-fed HFD animals. These observations suggest that NTS Apo AIV or/and peripheral CCK requires vagal CCK-1R signaling to elicit satiation and that maintenance on a HFD reduces the satiating capacity of these 2 signals.