Hypothalamic malonyl-CoA as a mediator of feeding behavior

Physiologically relevant lactate accumulation from exercise or peripheral injection does not alter central or peripheral appetite signaling in mice

Lactate has been implicated in exercise-induced appetite suppression though little work has explored the mechanisms underpinning its role. Recent work suggests lactate accumulation via exercise and intracerebroventricular injection can alter central appetite regulating pathways, though a supraphysiological dose of lactate was administered centrally and there was no assessment of peripheral appetite markers. Therefore, we examined how physiologically relevant lactate accumulation via exercise or intraperitoneal injection altered central and peripheral appetite signaling pathways and whether the lactate dehydrogenase inhibitor oxamate could blunt any exercise effect. Forty 10-week-old C57BL/6 J male mice (n = 10/group) were assigned to either: 1) sedentary (SED + SAL; saline); 2) exercise (EX+SAL; saline); 3) exercise with oxamate (EX+OX; 750 mg‧kg-1 body mass); or 4) lactate (SED + LAC; 1.0 g‧kg-1 body mass). Blood, stomach, and hypothalamus samples were collected ∼2 h post-exercise/injection. Though oxamate blunted exercise-induced lactate accumulation compared to the EX+SAL condition (P = 0.044, d = 0.73), there were no differences in circulating acylated ghrelin or stomach ghrelin O-acyltransferase content between groups (P > 0.213, ηp2<0.125). There were also no differences in hypothalamic content for neuropeptide Y, proopiomelanocortin, agouti-related peptide, and alpha melanocyte-stimulating hormone (P > 0.150, ηp2<0.170). Exercise did increase phosphorylated-total signal transducer and activator of transcription 3 (pSTAT3) compared to EX+OX (p = 0.065, d = 1.23) but there were no differences in other markers of lactate signaling: phosphorylated-total adenosine monophosphate activated protein kinase, and protein kinase b (P > 0.121, ηp2<0.160). Our results suggest that lactate accumulation due to exercise or peripheral injection does not alter central or peripheral appetite signaling when measured 2 h post-exercise/injection, though pSTAT3 was blunted with oxamate.

Short-chain fatty acids: Important components of the gut-brain axis against AD

Alzheimer's disease (AD) comprises a group of neurodegenerative disorders with some changes in the brain, which could lead to the deposition of certain proteins and result in the degeneration and death of brain cells. Patients with AD manifest primarily as cognitive decline, psychiatric symptoms, and behavioural disorders. Short-chain fatty acids (SCFAs) are a class of saturated fatty acids (SFAs) produced by gut microorganisms through the fermentation of dietary fibre ingested. SCFAs, as a significant mediator of signalling, can have diverse physiological and pathological roles in the brain through the gut-brain axis, and play a positive effect on AD via multiple pathways. Firstly, differences in SCFAs and microbial changes have been stated in AD cases of humans and mice in this paper. And then, mechanisms of three main SCFAs in treating with AD have been summarized, as well as differences of gut bacteria. Finally, functions of SCFAs played in regulating intestinal flora homeostasis, modulating the immune system, and the metabolic system, which were considered to be beneficial for the treatment of AD, have been elucidated, and the key roles of gut bacteria and SCFAs were pointed out. All in all, this paper provides an overview of SCFAs and gut bacteria in AD, and can help people to understand the importance of gut-brain axis in AD.

Chronic cortisol stimulation enhances hypothalamus-specific enrichment of metabolites in the rainbow trout brain

The hypothalamus is a key integrating center that is involved in the initiation of the corticosteroid stress response, and in regulating nutrient homeostasis. Although cortisol, the principal glucocorticoid in humans and teleosts, plays a central role in feeding regulation, the mechanisms are far from clear. We tested the hypothesis that the metabolic changes to cortisol exposure signal an energy excess in the hypothalamus, leading to feeding suppression during stress in fish. Rainbow trout (Oncorhynchus mykiss) were administered a slow-release cortisol implant for 3 days, and the metabolite profiles in the plasma, hypothalamus, and the rest of the brain were assessed. Also, U-13C-glucose was injected into the hypothalamus by intracerebroventricular (ICV) route, and the metabolic fate of this energy substrate was followed in the brain regions by metabolomics. Chronic cortisol treatment reduced feed intake, and this corresponded with a downregulation of the orexigenic gene agrp, and an upregulation of the anorexigenic gene cart in the hypothalamus. The U-13C-glucose-mediated metabolite profiling indicated an enhancement of glycolytic flux and tricarboxylic acid intermediates in the rest of the brain compared with the hypothalamus. There was no effect of cortisol treatment on the phosphorylation status of AMPK or mechanistic target of rapamycin in the brain, whereas several endogenous metabolites, including leucine, citrate, and lactate were enriched in the hypothalamus, suggesting a tissue-specific metabolic shift in response to cortisol stimulation. Altogether, our results suggest that the hypothalamus-specific enrichment of leucine and the metabolic fate of this amino acid, including the generation of lipid intermediates, contribute to cortisol-mediated feeding suppression in fish.NEW & NOTEWORTHY Elevated cortisol levels during stress suppress feed intake in animals. We tested whether the feed suppression is associated with cortisol-mediated alteration in hypothalamus metabolism. The brain metabolome revealed a hypothalamus-specific metabolite profile suggesting nutrient excess. Specifically, we noted the enrichment of leucine and citrate in the hypothalamus, and the upregulation of pathways involved in leucine metabolism and fatty acid synthesis. This cortisol-mediated energy substrate repartitioning may modulate the feeding/satiety centers leading to the feeding suppression.

The Unrestrained Overeating Behavior and Clinical Perspective

Obesity-related co-morbidities decrease life quality, reduce working ability, and lead to early death. In the adult population, eating addiction manifests with excessive food consumption and the unrestrained overeating behavior, which is associated with increased risk of morbidity and mortality and defined as the binge eating disorder (BED). This hedonic intake is correlated with fat preference and the total amount of dietary fat consumption is the most potent risk factor for weight gain. Long-term BED leads to greater sensitivity to the rewarding effects of palatable foods and results in obesity fatefully. Increased plasma concentrations of non-esterified free fatty acids and lipid-overloaded hypertrophic adipocytes may cause insulin resistance. In addition to dietary intake of high-fat diet, sedentary lifestyle leads to increased storage of triglycerides not only in adipose tissue but also ectopically in other tissues. Lipid-induced apoptosis, ceramide accumulation, reactive oxygen species overproduction, endoplasmic reticulum stress, and mitochondrial dysfunction play role in the pathogenesis of lipotoxicity. Food addiction and BED originate from complex action of dopaminergic, opioid, and cannabinoid systems. BED may also be associated with both obesity and major depressive disorder. For preventing morbidity and mortality, as well as decreasing the impact of obesity-related comorbidities in appropriately selected patients, opiate receptor antagonists and antidepressant combination are recommended. Pharmacotherapy alongside behavioral management improves quality of life and reduces the obesity risk; however, the number of licensed drugs is very few. Thus, stereotactic treatment is recommended to break down the refractory obesity and binge eating in obese patient. As recent applications in the field of non-invasive neuromodulation, transcranial magnetic stimulation and transcranial direct current stimulation are thought to be important in image-guided deep brain stimulation in humans. Chronic overnutrition most likely provides repetitive and persistent signals that up-regulate inhibitor of nuclear factor kappa B (NF-κB) kinase beta subunit/NF-κB (IKKβ/NF-κB) in the hypothalamus before the onset of obesity. However, how the mechanisms of high-fat diet-induced peripheral signals affect the hypothalamic arcuate nucleus remain largely unknown.

HMBA ameliorates obesity by MYH9- and ACTG1-dependent regulation of hypothalamic neuropeptides

The global epidemic of obesity remains a daunting problem. Here, we report hexamethylene bisacetamide (HMBA) as a potent anti-obesity compound. Peripheral and central administration of HMBA to diet-induced obese mice regulated the expression of hypothalamic neuropeptides critical for energy balance, leading to beneficial metabolic effects such as anorexia and weight loss. We found that HMBA bound to MYH9 and ACTG1, which were required for the anti-obesity effects of HMBA in both NPY-expressing and POMC-expressing neurons. The binding of HMBA to MYH9 and ACTG1 elevated the expression of HEXIM1 and enhanced its interaction with MDM2, resulting in the dissociation of the HEXIM1-p53 complex in hypothalamic cells. Subsequently, the free HEXIM1 and p53 translocated to the nucleus, where they downregulated the transcription of orexigenic NPY, but p53 and acetylated histone 3 upregulated that of anorexigenic POMC. Our study points to a previously unappreciated efficacy of HMBA and reveals its mechanism of action in metabolic regulation, which may propose HMBA as a potential therapeutic strategy for obesity.

Targeting carnitine palmitoyltransferase 1 isoforms in the hypothalamus: A promising strategy to regulate energy balance

Tackling the growing incidence and prevalence of obesity urgently requires uncovering new molecular pathways with therapeutic potential. The brain, and in particular the hypothalamus, is a major integrator of metabolic signals from peripheral tissues that regulate functions such as feeding behavior and energy expenditure. In obesity, hypothalamic capacity to sense nutritional status and regulate these functions is altered. An emerging line of research is that hypothalamic lipid metabolism plays a critical role in regulating energy balance. Here, we focus on the carnitine palmitoyltransferase 1 (CPT1) enzyme family responsible for long-chain fatty acid metabolism. The evidence suggests that two of its isoforms expressed in the brain, CPT1A and CPT1C, play a crucial role in hypothalamic lipid metabolism, and their promise as targets in food intake and bodyweight management is currently being intensively investigated. In this review we describe and discuss the metabolic actions and potential up- and downstream effectors of hypothalamic CPT1 isoforms, and posit the need to develop innovative nanomedicine platforms for selective targeting of CPT1 and related nutrient sensors in specific brain areas as potential next-generation therapy to treat obesity.

Excess glucose or fat differentially affects metabolism and appetite-related gene expression during zebrafish embryogenesis

Zebrafish embryos use their yolk sac reserve as the sole nutrient source during embryogenesis. The two main forms of energy fuel can be found in the form of glucose or fat. Zebrafish embryos were exposed to glucose or injected with free fatty acid/Triacylglycerol (FFA/TAG) into the yolk sac at 24 hpf. At 72 hpf, glucose exposed or FFA/TAG injected had differential effects on gene expression in embryos, with fat activating lipolysis and β-oxidation and glucose activating the insulin pathway. Bulk RNA-seq revealed that more gene expression was affected by glucose exposure compared to FFA/TAGs injection. Appetite-controlling genes were also differently affected by glucose exposure or FFA/TAG injections. Because the embryo did not yet feed itself at the time of our analysis, gene expression changes occurred in absence of actual hunger and revealed how the embryo manages its nutrient intake before active feeding.

Effects of Essential Oils and Fragrant Compounds on Appetite: A Systematic Review

Appetite dysregulation is one of the factors contributing to anorexia, bulimia nervosa, obesity, and diabetes. Essential oils or fragrant compounds have been proven to regulate food intake and energy expenditure; hence, this study aimed to summarize their effects on appetite and the underlying mechanisms. The PubMed and Web of Science databases were searched until July 2022. Only two of the 41 studies were performed clinically, and the remaining 39 used animal models. Oral administration was the most common route, and a dosage range of 100-2000 mg/kg for mice or 2-32 mg/kg for rats was applied, with a duration of 12 days to 4 weeks, followed by inhalation (10^-6-10^-3 mg/cage or 10^-9-10^-2 mg/cm³ within 1 h). Approximately 11 essential oil samples and 22 fragrant compounds were found to increase appetite, while 12 essential oils and seven compounds decreased appetite. These fragrant components can exert appetite-regulating effects via leptin resistance, the activity of sympathetic/parasympathetic nerves, or the mRNA expression of neuropeptide Y (NPY)/agouti-related protein (AgRP), cocaine- and amphetamine-regulated transcript (CART)/proopiomelanocortin (POMC) in the hypothalamus. Fragrance memory and cognitive processes may also play roles in appetite regulation. The findings of this study accentuate the potential of essential oils and fragrant compounds to regulate appetite and eating disorders.

CPT1A in AgRP neurons is required for sex-dependent regulation of feeding and thirst

BACKGROUND

Fatty acid metabolism in the hypothalamus has an important role in food intake, but its specific role in AgRP neurons is poorly understood. Here, we examined whether carnitinea palmitoyltransferase 1A (CPT1A), a key enzyme in mitochondrial fatty acid oxidation, affects energy balance.

METHODS

To obtain Cpt1aKO mice and their control littermates, Cpt1a(flox/flox) mice were crossed with tamoxifen-inducible AgRPCreERT2 mice. Food intake and body weight were analyzed weekly in both males and females. At 12 weeks of age, metabolic flexibility was determined by ghrelin-induced food intake and fasting-refeeding satiety tests. Energy expenditure was analyzed by calorimetric system and thermogenic activity of brown adipose tissue. To study fluid balance the analysis of urine and water intake volumes; osmolality of urine and plasma; as well as serum levels of angiotensin and components of RAAS (renin-angiotensin-aldosterone system) were measured. At the central level, changes in AgRP neurons were determined by: (1) analyzing specific AgRP gene expression in RiboTag-Cpt1aKO mice obtained by crossing Cpt1aKO mice with RiboTag mice; (2) measuring presynaptic terminal formation in the AgRP neurons with the injection of the AAV1-EF1a-DIO-synaptophysin-GFP in the arcuate nucleus of the hypothalamus; (3) analyzing AgRP neuronal viability and spine formations by the injection AAV9-EF1a-DIO-mCherry in the arcuate nucleus of the hypothalamus; (4) analyzing in situ the specific AgRP mitochondria in the ZsGreen-Cpt1aKO obtained by breeding ZsGreen mice with Cpt1aKO mice. Two-way ANOVA analyses were performed to determine the contributions of the effect of lack of CPT1A in AgRP neurons in the sex.

RESULTS

Changes in food intake were just seen in male Cpt1aKO mice while only female Cpt1aKO mice increased energy expenditure. The lack of Cpt1a in the AgRP neurons enhanced brown adipose tissue activity, mainly in females, and induced a substantial reduction in fat deposits and body weight. Strikingly, both male and female Cpt1aKO mice showed polydipsia and polyuria, with more reduced serum vasopressin levels in females and without osmolality alterations, indicating a direct involvement of Cpt1a in AgRP neurons in fluid balance. AgRP neurons from Cpt1aKO mice showed a sex-dependent gene expression pattern, reduced mitochondria and decreased presynaptic innervation to the paraventricular nucleus, without neuronal viability alterations.

CONCLUSIONS

Our results highlight that fatty acid metabolism and CPT1A in AgRP neurons show marked sex differences and play a relevant role in the neuronal processes necessary for the maintenance of whole-body fluid and energy balance.

Atomoxetine and Fluoxetine Activate AMPK-ACC-CPT1 Pathway in Human SH-SY5Y and U-87 MG Cells

OBJECTIVE

Atomoxetine and fluoxetine are psychopharmacologic agents associated with loss of appetite and weight. Adenosine monophosphate-activated protein kinase (AMPK) is the cellular energy sensor that regulate metabolism and energy, being activated by fasting and inhibited by feeding in the hypothalamus.

METHODS

Human brain cell lines (SH-SY5Y and U-87 MG cells) were used to study the outcome of atomoxetine and fluoxetine treatment in the activity of AMPK-acetyl-CoA carboxylase (ACC)- carnitine palmitoyl transferase 1 (CPT1) pathway and upstream regulation by calcium/calmodulin-dependent kinase kinase β (CaMKKβ) using immunoblotting and CPT1 enzymatic activity measures.

RESULTS

Phosphorylation of AMPK and ACC increased significantly after atomoxetine and fluoxetine treatment in the first 30-60 minutes of treatment in the two cell lines. Activation of AMPK and inhibition of ACC was associated with an increase by 5-fold of mitochondrial CPT1 activity. Although the neuronal isoform CPT1C could be detected by immunoblotting, activity was not changed by the drug treatments. In addition, the increase in phospho-AMPK and phospho-ACC expression induced by atomoxetine was abolished by treatment with STO-609, a CaMKKβ inhibitor, indicating that AMPK-ACC-CPT1 pathway is activated through CaMKKβ phosphorylation.

CONCLUSION

These findings indicate that at the cellular level atomoxetine and fluoxetine treatments may activate AMPK-ACC-CPT1 pathways through CaMKKβ in human SH-SY5Y and U-87 MG cells.

Nanomedicine targeting brain lipid metabolism as a feasible approach for controlling the energy balance

Targeting brain lipid metabolism is a promising strategy to regulate the energy balance and fight metabolic diseases such as obesity. The development of stable platforms for selective delivery of drugs, particularly to the hypothalamus, is a challenge but a possible solution for these metabolic diseases. Attenuating fatty acid oxidation in the hypothalamus via CPT1A inhibition leads to satiety, but this target is difficult to reach in vivo with the current drugs. We propose using an advanced crosslinked polymeric micelle-type nanomedicine that can stably load the CPT1A inhibitor C75-CoA for in vivo control of the energy balance. Central administration of the nanomedicine induced a rapid attenuation of food intake and body weight in mice via regulation of appetite-related neuropeptides and neuronal activation of specific hypothalamic regions driving changes in the liver and adipose tissue. This nanomedicine targeting brain lipid metabolism was successful in the modulation of food intake and peripheral metabolism in mice.

Fatty acid-sensing mechanisms in the hypothalamus of European sea bass (Dicentrarchus labrax): The potential role of monounsaturated and polyunsaturated fatty acids

This study aimed to evaluate the hypothalamus fatty acid (FA)-sensing mechanisms response to different FA in European sea bass. For that purpose, fish (body weight of 90 g) were intraperitoneally (IP) injected (time 0 h) with five long-chain unsaturated fatty acids, namely, docosahexaenoic acid (DHA; C22:5n3); eicosapentaenoic acid (EPA; C20:4n3); α-linolenic (ALA; C18:3n3); linoleic acid (LA; C18:2n6) and oleic acid (OA; C18:1n9) at a dose of 300 μg kg^-1, or with 0.9% saline solution (control). Feed intake (FI) was recorded at 3, 6, and 24 h after the IP injection. One week later, fish were IP injected with the same FA, and the hypothalamus was collected 3 h after the IP injection for measurement of molecules related to FI regulation and FA-sensing mechanisms. Cumulative FI (g/kg/day) was not affected by treatments. However, compared to the control, FI increased with the OA treatment at 6 h after the IP injection. FI decreased with mealtime in the DHA and LA groups. Gene expression of orexigenic (npy/agrp) and anorexigenic (cart2/pomc1) neurons was not affected by the FA treatments. Attending the enzymes involved in the FA-sensing mechanisms activation, compared to the control carnitine palmitoyltransferase I (CPT1) and ATP citrate lyase (ACLY) activity were not affected by FA treatments. Contrarily the key enzymes of lipid metabolisms, malic enzyme and hydroxyacylCoA dehydrogenase was higher in fish that received the EPA and OA treatment, than fish treated to the control. Overall, the results of the present study indicate that gene expression of orexigenic and anorexigenic neurons was not affected at 3 h after IP injection with different FA. However, the activity of key enzymes of lipid metabolism was differently affected by circulating FA, indicating that FA-sensing mechanisms respond to different FA. Further studies are required involving different sampling times to further characterize the response of FA-sensing mechanisms to FA. These findings may be of relevance to the aquaculture industry in an era where alternative lipid sources are being increasingly used.

Acetyl-CoA-mediated autoacetylation of fatty acid synthase as a metabolic switch of de novo lipogenesis in Drosophila

De novo lipogenesis is a highly regulated metabolic process, which is known to be activated through transcriptional regulation of lipogenic genes, including fatty acid synthase (FASN). Unexpectedly, we find that the expression of FASN protein remains unchanged during Drosophila larval development from the second to the third instar larval stages (L2 to L3) when lipogenesis is hyperactive. Instead, acetylation of FASN is significantly upregulated in fast-growing larvae. We further show that lysine K813 residue is highly acetylated in developing larvae, and its acetylation is required for elevated FASN activity, body fat accumulation, and normal development. Intriguingly, K813 is autoacetylated by acetyl-CoA (AcCoA) in a dosage-dependent manner independent of acetyltransferases. Mechanistically, the autoacetylation of K813 is mediated by a novel P-loop-like motif (N-xx-G-x-A). Lastly, we find that K813 is deacetylated by Sirt1, which brings FASN activity to baseline level. In summary, this work uncovers a previously unappreciated role of FASN acetylation in developmental lipogenesis and a novel mechanism for protein autoacetylation, through which Drosophila larvae control metabolic homeostasis by linking AcCoA, lysine acetylation, and de novo lipogenesis.

Comparison of oral administration of fructose and glucose on food intake and physiological parameters in broiler chicks

Like glucose, fructose is a monosaccharide, but the mechanisms of its absorption and metabolism in the body are very different between the 2 molecules. In this study, we investigated the effects of oral administration of glucose and fructose on food intake, diencephalic gene expression, and plasma metabolite concentrations in broiler chicks. The animals used in this study were 4-day-old male broiler chicks (Ross 308). They were given glucose, fructose (200 mg/ 0.5 mL/ bird), or a similar volume of distilled water orally after 6 h fasting. After treatment, measurements of food intake (at 0, 30, and 60 min), and blood glucose as well as insulin concentrations were measured over time; however, diencephalic (hypothalamus) gene expression and plasma metabolites were measured at 30 min. The results showed that glucose administration suppressed food intake, but fructose administration did not suppress food intake and it was at the same level as distilled water administration. In addition, fructose administration did not increase plasma glucose and insulin levels as did glucose administration. In the diencephalon, expression levels of genes related to the melanocortin system were unaffected by the treatment, while gene expression levels related to intracellular energy regulation, such as AMP-activated protein kinase were affected by the glucose treatment in the fasted chicks. These results suggest that fructose administration does not suppress feeding behavior as a result of possible reduction in the energy levels in the diencephalon and associated energy metabolism.

Diet-Induced Metabolic Dysfunction of Hypothalamic Nutrient Sensing in Rodents

A sedentary lifestyle and excessive nutrient intake resulting from the consumption of high-fat and calorie-rich diets are environmental factors contributing to the rapid growth of the current pandemic of type 2 diabetes mellitus (DM2). Fasting hyperglycemia, an established hallmark of DM2, is caused by excessive production of glucose by the liver, resulting in the inability of insulin to suppress endogenous glucose production. To prevent inappropriate elevations of circulating glucose resulting from changes in nutrient availability, mammals rely on complex mechanisms for continuously detecting these changes and to respond to them with metabolic adaptations designed to modulate glucose output. The mediobasal hypothalamus (MBH) is the key center where nutritional cues are detected and appropriate modulatory responses are integrated. However, certain environmental factors may have a negative impact on these adaptive responses. For example, consumption of a diet enriched in saturated fat in rodents resulted in the development of a metabolic defect that attenuated these nutrient sensing mechanisms, rendering the animals prone to developing hyperglycemia. Thus, high-fat feeding leads to a state of “metabolic disability” in which animals’ glucoregulatory responses fail. We postulate that the chronic faltering of the hypothalamic glucoregulatory mechanisms contributes to the development of metabolic disease.

Understanding the Effects of Antipsychotics on Appetite Control

Antipsychotic drugs (APDs) represent a cornerstone in the treatment of schizophrenia and other psychoses. The effectiveness of the first generation (typical) APDs are hampered by so-called extrapyramidal side effects, and they have gradually been replaced by second (atypical) and third-generation APDs, with less extrapyramidal side effects and, in some cases, improved efficacy. However, the use of many of the current APDs has been limited due to their propensity to stimulate appetite, weight gain, and increased risk for developing type 2 diabetes and cardiovascular disease in this patient group. The mechanisms behind the appetite-stimulating effects of the various APDs are not fully elucidated, partly because their diverse receptor binding profiles may affect different downstream pathways. It is critical to identify the molecular mechanisms underlying drug-induced hyperphagia, both because this may lead to the development of new APDs, with lower appetite-stimulating effects but also because such insight may provide new knowledge about appetite regulation in general. Hence, in this review, we discuss the receptor binding profile of various APDs in relation to the potential mechanisms by which they affect appetite.

Acetyl-CoA Metabolism and Histone Acetylation in the Regulation of Aging and Lifespan

Acetyl-CoA is a metabolite at the crossroads of central metabolism and the substrate of histone acetyltransferases regulating gene expression. In many tissues fasting or lifespan extending calorie restriction (CR) decreases glucose-derived metabolic flux through ATP-citrate lyase (ACLY) to reduce cytoplasmic acetyl-CoA levels to decrease activity of the p300 histone acetyltransferase (HAT) stimulating pro-longevity autophagy. Because of this, compounds that decrease cytoplasmic acetyl-CoA have been described as CR mimetics. But few authors have highlighted the potential longevity promoting roles of nuclear acetyl-CoA. For example, increasing nuclear acetyl-CoA levels increases histone acetylation and administration of class I histone deacetylase (HDAC) inhibitors increases longevity through increased histone acetylation. Therefore, increased nuclear acetyl-CoA likely plays an important role in promoting longevity. Although cytoplasmic acetyl-CoA synthetase 2 (ACSS2) promotes aging by decreasing autophagy in some peripheral tissues, increased glial AMPK activity or neuronal differentiation can stimulate ACSS2 nuclear translocation and chromatin association. ACSS2 nuclear translocation can result in increased activity of CREB binding protein (CBP), p300/CBP-associated factor (PCAF), and other HATs to increase histone acetylation on the promoter of neuroprotective genes including transcription factor EB (TFEB) target genes resulting in increased lysosomal biogenesis and autophagy. Much of what is known regarding acetyl-CoA metabolism and aging has come from pioneering studies with yeast, fruit flies, and nematodes. These studies have identified evolutionary conserved roles for histone acetylation in promoting longevity. Future studies should focus on the role of nuclear acetyl-CoA and histone acetylation in the control of hypothalamic inflammation, an important driver of organismal aging.

The return of malonyl-CoA to the brain: Cognition and other stories

Nutrients, hormones and the energy sensor AMP-activated protein kinase (AMPK) tightly regulate the intracellular levels of the metabolic intermediary malonyl-CoA, which is a precursor of fatty acid synthesis and a negative regulator of fatty acid oxidation. In the brain, the involvement of malonyl-CoA in the control of food intake and energy homeostasis has been known for decades. However, recent data uncover a new role in cognition and brain development. The sensing of malonyl-CoA by carnitine palmitoyltransferase 1 (CPT1) proteins regulates a variety of functions, such as the fate of neuronal stem cell precursors, the motility of lysosomes in developing axons, the trafficking of glutamate receptors to the neuron surface (necessary for proper synaptic function) and the metabolic coupling between astrocytes and neurons. We discuss the relevance of those recent findings evidencing how nutrients and metabolic disorders impact cognition. We also enumerate all nutritional and hormonal conditions that are known to regulate malonyl-CoA levels in the brain, reflect on protein malonylation as a new post-translational modification, and give a reasoned vision of the opportunities and challenges that future research in the field could address.

Prenatal and early postnatal food restrictions cause changes in brain oxidative status and orexigenic/anorexigenic hormones in the offspring of rats: prevention by quercetin and kaempferol

Brain oxidative signaling pathways have been identified as important targets for alleviating food deprivation-induced changes in metabolic gate-ways. Previous studies have shown that prenatal and early postnatal malnutrition alters leptin and ghrelin signaling via oxidative pathways. Thus, it has been hypothesized that agents with antioxidant properties might be beneficial for the mitigation of prenatal and early postnatal food scarcity-induced oxidative damage. Quercetin and kaempferol are natural bioflavonoids with proven antioxidant properties. In this study, we evaluated their effects on prenatal maternal food consumption, maternal and pup weights, biomarkers of orexigenic and anorexigenic hormones and oxidative stress in rats. Rats were allotted into different treatment groups (n ​= ​6) in three different experiments (prenatal, postnatal food-deprivations or both). Prenatal-food restriction (PrNFR) was induced by 50% of ad libitum accessible diet during pregnancy till parturition and postnatal-food restriction (PsNFR) was simulated by litter-enlargement to 16 pups per mother from postnatal day (PND) 2. Rats in each experiment were concurrently treated with vehicle (10 ​mL/kg), quercetin (50, 100 and 200 ​mg/kg, p.o.) or kaempferol (50, 100 and 200 ​mg/kg, p.o.) respectively. A third experimental group consisted of both protocols. Quercetin and kaempferol dose-dependently increased the body weights of pups exposed to PrNFR, PsNFR and PrNFR-PsNFR at PNDs 1-22 respectively. Both compounds increased maternal body weights but attenuated maternal food-intake at prenatal days 7 and 14 due by PrNFR. Quercetin and kaempferol reduced brain malondialdehyde concentrations and increased glutathione levels in PrNFR, PsNFR and PrNFR-PsNFR-exposed offspring of rats. Importantly, quercetin and kaempferol significantly (p ​< ​0.05) prevented PrNFR-, PsNFR- or PrNFR-PsNFR-induced alterations in leptin and ghrelin levels. Cumulatively, quercetin and kaempferol increased pup and maternal weights and attenuated maternal food-intake of rats submitted to PrNFR, PsNFR and PrNFR-PsNFR respectively, likely via nutrigenomic modulations of orexigenic/anorexigenic hormones and inhibition of brain oxidative stress.

Coenzyme A and Its Thioester Pools in Obese Zucker and Zucker Diabetic Fatty Rats

Feeding behavior is closely related to hypothalamic malonyl-CoA level in the brain and diet-induced obesity affects total CoA pools in liver. Herein, we performed a comprehensive analysis of the CoA pools formed in thirteen tissues of Zucker and Zucker diabetic fatty (ZDF) rats. Hypothalamic malonyl-CoA levels in obese rats remained low and were almost the same as those of lean rats, despite obese rats having much higher content of leptin, insulin, and glucose in their sera. Regardless of the fa-genotypes, larger total CoA pools were formed in the livers of ZDF rats and the size of hepatic total CoA pools in Zucker rats showed almost one tenth of the size of ZDF rats. The decreased total CoA pool sizes in Zucker rats was observed in the brown adipose tissues, while ZDF-fatty rats possessed 6% of total CoA pool in the lean rats in response to fa deficiency. This substantially lower CoA content in the obese rats would be disadvantageous to non-shivering thermogenesis. Thus, comparing the intracellular CoA behaviors between Zucker and ZDF rats, as well as the lean and fatty rats of each strain would help to elucidate features of obesity and type 2 diabetes in combination with result (s) of differential gene expression analysis and/or comparative genomics.

Evolved resistance to partial GAPDH inhibition results in loss of the Warburg effect and in a different state of glycolysis

Aerobic glycolysis or the Warburg effect (WE) is characterized by increased glucose uptake and incomplete oxidation to lactate. Although the WE is ubiquitous, its biological role remains controversial, and whether glucose metabolism is functionally different during fully oxidative glycolysis or during the WE is unknown. To investigate this question, here we evolved resistance to koningic acid (KA), a natural product that specifically inhibits glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a rate-controlling glycolytic enzyme, during the WE. We found that KA-resistant cells lose the WE but continue to conduct glycolysis and surprisingly remain dependent on glucose as a carbon source and also on central carbon metabolism. Consequently, this altered state of glycolysis led to differential metabolic activity and requirements, including emergent activities in and dependences on fatty acid metabolism. These findings reveal that aerobic glycolysis is a process functionally distinct from conventional glucose metabolism and leads to distinct metabolic requirements and biological functions.

Physiological Effect of Ghrelin on Body Systems

Ghrelin is a relatively novel multifaceted hormone that has been found to exert a plethora of physiological effects. In this review, we found/confirmed that ghrelin has effect on all body systems. It induces appetite; promotes the use of carbohydrates as a source of fuel while sparing fat; inhibits lipid oxidation and promotes lipogenesis; stimulates the gastric acid secretion and motility; improves cardiac performance; decreases blood pressure; and protects the kidneys, heart, and brain. Ghrelin is important for learning, memory, cognition, reward, sleep, taste sensation, olfaction, and sniffing. It has sympatholytic, analgesic, antimicrobial, antifibrotic, and osteogenic effects. Moreover, ghrelin makes the skeletal muscle more excitable and stimulates its regeneration following injury; delays puberty; promotes fetal lung development; decreases thyroid hormone and testosterone; stimulates release of growth hormone, prolactin, glucagon, adrenocorticotropic hormone, cortisol, vasopressin, and oxytocin; inhibits insulin release; and promotes wound healing. Ghrelin protects the body by different mechanisms including inhibition of unwanted inflammation and induction of autophagy. Having a clear understanding of the ghrelin effect in each system has therapeutic implications. Future studies are necessary to elucidate the molecular mechanisms of ghrelin actions as well as its application as a GHSR agonist to treat most common diseases in each system without any paradoxical outcomes on the other systems.

Effect of long-chain saturated and unsaturated fatty acids on hypothalamic fatty acid sensing in Chinese perch (Siniperca chuatsi)

In order to evaluate fatty acid (FA) sensing systems based on binding to FAT/CD36 in hypothalamus of Chinese perch (Siniperca chuatsi) and its sensitivity to FAs with the same chain length and different unsaturation levels. The effects of Stearate (SA; C18:0), oleate (OA; C18:1 n-9), linoleic acid (LA; C18:2 n-6), and α-linolenic acid (ALA; C18:3 n-3) on hypothalamic FA sensing were evaluated by intracerebroventricular (ICV) administration. Food intake was assessed after 2, 4, 6, 8 and 12 h. Gene expression associated with FA sensing mechanism such as cd36, pparα and srebp1c, and neuropeptides controlling appetite such as pomca, cart, agrp2 and npy were assessed after 6 h. The ICV treatment of OA, LA and ALA activated FAT/CD36 and PPARα, rather than SA, and modulated gene expression levels of hypothalamic neuropeptides associated with appetite. And then, OA, LA and ALA inhibited food intake, which was consistent with the activation of hypothalamus FA sensing. Our data indicated some mechanisms of the hypothalamic FA sensing systems also existed in Chinese perch. It's worth noting that polyunsaturated fatty acids (PUFA) could also activate hypothalamic FA sensing mechanisms in Chinese perch. The unsaturation of FA appears to be extremely important for FA sensing mechanisms, since no major influences in Chinese perch after SA treatment. Our findings will contribute to the study of long-chain FAs sensing mechanisms in fish hypothalamus and highlight the importance of PUFAs in fish species.

Inborn errors of mitochondrial acyl-coenzyme a metabolism: acyl-CoA biology meets the clinic

The last decade saw major advances in understanding the metabolism of Coenzyme A (CoA) thioesters (acyl-CoAs) and related inborn errors (CoA metabolic diseases, CAMDs). For diagnosis, acylcarnitines and organic acids, both derived from acyl-CoAs, are excellent markers of most CAMDs. Clinically, each CAMD is unique but strikingly, three main patterns emerge: first, systemic decompensations with combinations of acidosis, ketosis, hypoglycemia, hyperammonemia and fatty liver; second, neurological episodes, particularly acute "stroke-like" episodes, often involving the basal ganglia but sometimes cerebral cortex, brainstem or optic nerves and third, especially in CAMDs of long chain fatty acyl-CoA metabolism, lipid myopathy, cardiomyopathy and arrhythmia. Some patients develop signs from more than one category. The pathophysiology of CAMDs is not precisely understood. Available data suggest that signs may result from CoA sequestration, toxicity and redistribution (CASTOR) in the mitochondrial matrix has been suggested to play a role. This predicts that most CAMDs cause deficiency of CoA, limiting mitochondrial energy production, and that toxic effects from the abnormal accumulation of acyl-CoAs and from extramitochondrial functions of acetyl-CoA may also contribute. Recent progress includes the following. (1) Direct measurements of tissue acyl-CoAs in mammalian models of CAMDs have been related to clinical features. (2) Inborn errors of CoA biosynthesis were shown to cause clinical changes similar to those of inborn errors of acyl-CoA degradation. (3) CoA levels in cells can be influenced pharmacologically. (4) Roles for acetyl-CoA are increasingly identified in all cell compartments. (5) Nonenzymatic acyl-CoA-mediated acylation of intracellular proteins occurs in mammalian tissues and is increased in CAMDs.

The Short-Chain Fatty Acid Acetate in Body Weight Control and Insulin Sensitivity

The interplay of gut microbiota, host metabolism, and metabolic health has gained increased attention. Gut microbiota may play a regulatory role in gastrointestinal health, substrate metabolism, and peripheral tissues including adipose tissue, skeletal muscle, liver, and pancreas via its metabolites short-chain fatty acids (SCFA). Animal and human data demonstrated that, in particular, acetate beneficially affects host energy and substrate metabolism via secretion of the gut hormones like glucagon-like peptide-1 and peptide YY, which, thereby, affects appetite, via a reduction in whole-body lipolysis, systemic pro-inflammatory cytokine levels, and via an increase in energy expenditure and fat oxidation. Thus, potential therapies to increase gut microbial fermentation and acetate production have been under vigorous scientific scrutiny. In this review, the relevance of the colonically and systemically most abundant SCFA acetate and its effects on the previously mentioned tissues will be discussed in relation to body weight control and glucose homeostasis. We discuss in detail the differential effects of oral acetate administration (vinegar intake), colonic acetate infusions, acetogenic fiber, and acetogenic probiotic administrations as approaches to combat obesity and comorbidities. Notably, human data are scarce, which highlights the necessity for further human research to investigate acetate’s role in host physiology, metabolic, and cardiovascular health.

Spilanthol from Traditionally Used Spilanthes acmella Enhances AMPK and Ameliorates Obesity in Mice Fed High-Fat Diet

Spilanthol (SP) is a bioactive compound found in Spilanthes acmella, giving the flowers and leaves a spicy taste. Studies found that phyto-ingredients stored in spice plants act against obesity-related diseases. SP has antimicrobial, anti-inflammatory, and analgesic properties, but the effects on obesity are not yet known. We investigated the effects of SP in differentiated adipocytes (3T3-L1 cells) and mice fed a high-fat diet (HFD). SP significantly inhibited intracellular lipid accumulation and significantly reduced the expression of lipogenesis-related proteins, including acetyl-CoA carboxylase (ACC) and fatty-acid synthase (FAS). In contrast, SP increased the expression of carnitine palmitoyltransferase (CPT)1 and AMP-activated protein kinase (AMPK) in adipocytes. However, SP suppressed the levels of cyclooxygenase-2 (COX-2), phospho-p38 (pp38), and phospho-JNK (c-Jun N-terminal kinase) (pJNK) in LPS (lipopolysaccharide)-stimulated murine pre-adipocytes. SP administered to HFD-induced obese mice via intraperitoneal injections twice a week for 10 weeks decreased body weight gain, visceral adipose tissue weight, and adipocyte size. SP inhibited lipogenic proteins FAS and ACC, and suppressed adipogenic transcription factors, enhancing lipolysis and AMPK protein expression in the liver. SP has anti-obesity effects, upregulating AMPK to attenuate lipogenic and adipogenic transcription factors.

Dietary R, S-1,3-butanediol diacetoacetate reduces body weight and adiposity in obese mice fed a high-fat diet

The dietary R-3-hydroxybutyrate- R-1,3-butanediol monoester increases resting energy expenditure (REE) and markers of brown and white adipose thermogenesis in lean mice. The purpose of this investigation was to determine whether the ketone ester, R, S-1,3-butanediol diacetoacetate (BD-AcAc2), increases energy expenditure and markers of adipose tissue thermogenesis in the context of high-fat diet (HFD)-induced obesity. Thirty-five-week-old male C57BL/6J mice were placed on an ad libitum HFD (45% kcal) for 10 wk. The mice were then randomized to 1 of 3 groups ( n = 10 per group) for an additional 12 wk: 1) control (Con), continuous HFD, 2) pair-fed (PF) to ketone ester (KE); and 3) KE: HFD+30% energy from BD-AcAc2. Mean energy intake throughout the study was ∼26% lower in the KE compared to the Con group (8.2 ± 0.5 vs. 11.2 ± 0.7 kcal/d; P < 0.05). Final body weight (26.8 ± 3.6 vs. 34.9 ± 4.8 g; P < 0.001) and fat mass (5.2 ± 1.2 vs. 11.3 ± 4.5 g; P < 0.001) of the KE group was significantly lower than PF, despite being matched for energy provisions. Differences in body weight and adiposity were accompanied by higher REE and total energy expenditure in the KE group compared to PF after adjustment for lean body mass and fat-mass ( P = 0.001 and 0.007, respectively). Coupled or uncoupled mitochondrial respiratory rates in skeletal muscle were not different among groups, but markers of mitochondrial uncoupling and thermogenesis (uncoupling protein-1, deiodinase-2, and peroxisome proliferator-activated receptor γ coactivator-1α) were higher in interscapular brown adipose tissue (BAT) of mice receiving the KE diet. The absence of mitochondrial uncoupling in skeletal muscle and increased markers of mitochondrial uncoupling in BAT suggest that BD-AcAc2 initiates a transcriptional signature consistent with BAT thermogenesis in the context of HFD-induced obesity.-Davis, R. A. H., Deemer, S. E., Bergeron, J. M., Little, J. T., Warren, J. L., Fisher, G., Smith, D. L., Jr., Fontaine, K. R., Dickinson, S. L., Allison, D. B., Plaisance, E. P. Dietary R, S-1,3-butanediol diacetoacetate reduces body weight and adiposity in obese mice fed a high-fat diet.

Tributyrin in Inflammation: Does White Adipose Tissue Affect Colorectal Cancer?

Colorectal cancer affects the large intestine, leading to loss of white adipose tissue (WAT) and alterations in adipokine secretion. Lower incidence of colorectal cancer is associated with increased fibre intake. Fructooligosaccharides (FOS) are fibres that increase production of butyrate by the intestinal microbiota. Tributyrin, a prodrug of butyric acid, exerts beneficial anti-inflammatory effects on colorectal cancer. Our aim was to characterise the effects of diets rich in FOS and tributyrin within the context of a colon carcinogenesis model, and characterise possible support of tumorigenesis by WAT. C57/BL6 male mice were divided into four groups: a control group (CT) fed with chow diet and three colon carcinogenesis-induced groups fed either with chow diet (CA), tributyrin-supplemented diet (BUT), or with FOS-supplemented diet. Colon carcinogenesis decreased adipose mass in subcutaneous, epididymal, and retroperitoneal tissues, while also reducing serum glucose and leptin concentrations. However, it did not alter the concentrations of adiponectin, interleukin (IL)-6, IL-10, and tumour necrosis factor alpha (TNF)-α in WAT. Additionally, the supplements did not revert the colon cancer affected parameters. The BUT group exhibited even higher glucose tolerance and levels of IL-6, VEGF, and TNF-α in WAT. To conclude our study, FOS and butyrate supplements were not beneficial. In addition, butyrate worsened adipose tissue inflammation.

Electroacupuncture Mitigates Skeletal Muscular Lipid Metabolism Disorder Related to High-Fat-Diet Induced Insulin Resistance through the AMPK/ACC Signaling Pathway

The aim of this work is to investigate the effect of electroacupuncture (EA) on insulin sensitivity in high-fat diet (HFD) induced insulin resistance (IR) rats and to evaluate expression of AMPK/ACC signaling components. Thirty-two male Sprague-Dawley rats were randomized into control group, HFD group, HFD+Pi (oral gavage of pioglitazone) group, and HFD+EA group. Acupuncture was subcutaneously applied to Zusanli (ST40) and Sanyinjiao (SP6). For Zusanli (ST40) and Sanyinjiao (SP6), needles were connected to an electroacupuncture (EA) apparatus. Fasting plasma glucose was measured by glucose oxidase method. Plasma fasting insulin (FINS) and adiponectin (ADP) were determined by ELISA. Triglyceride (TG) and cholesterol (TC) were determined by Gpo-pap. Proteins of adiponectin receptor 1 (adipoR1), AMP-activated Protein Kinase (AMPK), and acetyl-CoA carboxylase (ACC) were determined by Western blot, respectively. Compared with the control group, HFD group exhibits increased levels of FPG, FINS, and homeostatic model assessment of insulin resistance (HOMA-IR) and decreased level of ADP and insulin sensitivity index (ISI). These changes were reversed by both EA and pioglitazone. Proteins of adipoR1 and AMPK were decreased, while ACC were increased in HFD group compared to control group. Proteins of these molecules were restored back to normal levels upon EA and pioglitazone. EA can improve the insulin sensitivity of insulin resistance rats; the positive regulation of the AMPK/ACC pathway in the skeletal muscle may be a possible mechanism of EA in the treatment of IR.

Role of the gut, melanocortin system and malonyl-CoA in control of feed intake in non-ruminant animals

Regulation of feed intake is under complex control, involving physical, chemical, hormonal and neuronal responses. Understanding the regulation of feed intake in farm animals is key to optimisation of intake to meet production and profitability goals. Fundamental mechanisms regulating feed intake include constraints imposed by the gut, systems monitoring current and long-term energy status to increase or decrease intake, and hedonic, reward-related drives. Feed intake is closely related to the rate of passage of digesta and the capacity of the gastrointestinal tract. Indigestible fibre increases the rate of digesta passage and feed intake until excess distension sends signals of satiety to the brain. The presence of partially digested nutrients and products of microbial fermentation in the distal intestines releases peptides (PYY, OXM, GPL-1, Apo A-IV, amylin) from gut and pancreas to activate the intestinal brake, which slows the rate of passage and reduces feed intake. These peptides also act on orexigenic (NPY, AgRP) and anorexigenic (POMC, CART) peptides of the melanocortin system of the hypothalamus to reduce intake over the long term. Immediate energy status of the animal is monitored through the ratio of AMP : ATP via adenosine monophosphate-activated kinase and mammalian target of rapamycin, whereas the overall animal energy status is monitored by insulin, leptin and ghrelin. These energy-monitoring systems control short- and long-term intakes through the melanocortin system of the hypothalamus, primarily via malonyl-CoA, to alter the relative expression of orexigenic and anorexigenic peptides. Gut and hypothalamic control of feed intake can be over-ridden by hedonic, reward-related centres of the brain, predominantly through the release of dopamine. These hedonic responses can lead to over-consumption and obesity under some circumstances or reduced feed intake under stressful or other negative environmental situations. Knowledge of these mechanisms can be used to identify practical strategies for either increasing or decreasing voluntary intake in pigs.

Zinc enhances the cellular energy supply to improve cell motility and restore impaired energetic metabolism in a toxic environment induced by OTA

Exogenous nutrient elements modulate the energetic metabolism responses that are prerequisites for cellular homeostasis and metabolic physiology. Although zinc is important in oxidative stress and cytoprotection processes, its role in the regulation of energetic metabolism remains largely unknown. In this study, we found that zinc stimulated aspect in cell motility and was essential in restoring the Ochratoxin A (OTA)-induced energetic metabolism damage in HEK293 cells. Moreover, using zinc supplementation and zinc deficiency models, we observed that zinc is conducive to mitochondrial pyruvate transport, oxidative phosphorylation, carbohydrate metabolism, lipid metabolism and ultimate energy metabolism in both normal and toxic-induced oxidative stress conditions in vitro, and it plays an important role in restoring impaired energetic metabolism. This zinc-mediated energetic metabolism regulation could also be helpful for DNA maintenance, cytoprotection and hereditary cancer traceability. Therefore, zinc can widely adjust energetic metabolism and is essential in restoring the impaired energetic metabolism of cellular physiology.

Brain Ceramide Metabolism in the Control of Energy Balance

The regulation of energy balance by the central nervous system (CNS) is a key actor of energy homeostasis in mammals, and deregulations of the fine mechanisms of nutrient sensing in the brain could lead to several metabolic diseases such as obesity and type 2 diabetes (T2D). Indeed, while neuronal activity primarily relies on glucose (lactate, pyruvate), the brain expresses at high level enzymes responsible for the transport, utilization and storage of lipids. It has been demonstrated that discrete neuronal networks in the hypothalamus have the ability to detect variation of circulating long chain fatty acids (FA) to regulate food intake and peripheral glucose metabolism. During a chronic lipid excess situation, this physiological lipid sensing is impaired contributing to type 2 diabetes in predisposed subjects. Recently, different studies suggested that ceramides levels could be involved in the regulation of energy balance in both hypothalamic and extra-hypothalamic areas. Moreover, under lipotoxic conditions, these ceramides could play a role in the dysregulation of glucose homeostasis. In this review we aimed at describing the potential role of ceramides metabolism in the brain in the physiological and pathophysiological control of energy balance.

Hypothalamic Integration of Metabolic, Endocrine, and Circadian Signals in Fish: Involvement in the Control of Food Intake

The regulation of food intake in fish is a complex process carried out through several different mechanisms in the central nervous system (CNS) with hypothalamus being the main regulatory center. As in mammals, a complex hypothalamic circuit including two populations of neurons: one co-expressing neuropeptide Y (NPY) and Agouti-related peptide (AgRP) and the second one population co-expressing pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) is involved in the integration of information relating to food intake control. The production and release of these peptides control food intake, and the production results from the integration of information of different nature such as levels of nutrients and hormones as well as circadian signals. The present review summarizes the knowledge and recent findings about the presence and functioning of these mechanisms in fish and their differences vs. the known mammalian model.

Similarities and interactions between the ageing process and high chronic intake of added sugars

In our societies, the proportions of elderly people and of obese individuals are increasing. Both factors are associated with high health-related costs. During obesity, many authors suggest that it is a high chronic intake of added sugars (HCIAS) that triggers the shift towards pathology. However, the majority of studies were performed in young subjects and only a few were interested in the interaction with the ageing process. Our purpose was to discuss the metabolic effects of HCIAS, compare with the effects of ageing, and evaluate how deleterious the combined action of HCIAS and ageing could be. This effect of HCIAS seems mediated by fructose, targeting the liver first, which may lead to all subsequent metabolic alterations. The first basic alterations induced by fructose are increased oxidative stress, protein glycation, inflammation, dyslipidaemia and insulin resistance. These alterations are also present during the ageing process, and are closely related to each other, one leading to the other. These basic alterations are also involved in more complex syndromes, which are also favoured by HCIAS, and present during ageing. These include non-alcoholic fatty liver disease, hypertension, neurodegenerative diseases, sarcopenia and osteoporosis. Cumulative effects of ageing and HCIAS have been seldom tested and may not always be strictly additive. Data also suggest that some of the metabolic alterations that are more prevalent during ageing could be related more with nutritional habits than to intrinsic ageing. In conclusion, it is clear that HCIAS interacts with the ageing process, accelerates the accumulation of metabolic alterations, and that it should be avoided.

Nutrient Sensing Systems in Fish: Impact on Food Intake Regulation and Energy Homeostasis

Evidence obtained in recent years in a few species, especially rainbow trout, supports the presence in fish of nutrient sensing mechanisms. Glucosensing capacity is present in central (hypothalamus and hindbrain) and peripheral [liver, Brockmann bodies (BB, main accumulation of pancreatic endocrine cells in several fish species), and intestine] locations whereas fatty acid sensors seem to be present in hypothalamus, liver and BB. Glucose and fatty acid sensing capacities relate to food intake regulation and metabolism in fish. Hypothalamus is as a signaling integratory center in a way that detection of increased levels of nutrients result in food intake inhibition through changes in the expression of anorexigenic and orexigenic neuropeptides. Moreover, central nutrient sensing modulates functions in the periphery since they elicit changes in hepatic metabolism as well as in hormone secretion to counter-regulate changes in nutrient levels detected in the CNS. At peripheral level, the direct nutrient detection in liver has a crucial role in homeostatic control of glucose and fatty acid whereas in BB and intestine nutrient sensing is probably involved in regulation of hormone secretion from endocrine cells.

Eat and Death: Chronic Over-Eating

Obesity-related co-morbidities decrease life quality, reduce working ability and lead to early death. The total amount of dietary fat consumption may be the most potent food-related risk factor for weight gain. In this respect, dietary intake of high-caloric, high-fat diets due to chronic over-eating and sedentary lifestyle lead to increased storage of triglycerides not only in adipose tissue but also ectopically in other tissues . Increased plasma concentrations of non-esterified free fatty acids and lipid-overloaded hypertrophic adipocytes may cause insulin resistance in an inflammation-independent manner. Even in the absence of metabolic disorders, mismatch between fatty acid uptake and utilization leads to the accumulation of toxic lipid species resulting in organ dysfunction. Lipid-induced apoptosis, ceramide accumulation, reactive oxygen species overproduction, endoplasmic reticulum stress, and mitochondrial dysfunction may play role in the pathogenesis of lipotoxicity. The hypothalamus senses availability of circulating levels of glucose, lipids and amino acids, thereby modifies feeding according to the levels of those molecules. However, the hypothalamus is also similarly vulnerable to lipotoxicity as the other ectopic lipid accumulated tissues. Chronic overnutrition most likely provides repetitive and persistent signals that up-regulate inhibitor of nuclear factor kappa B kinase beta subunit/nuclear factor kappa B (IKKβ/NF-κB) in the hypothalamus before the onset of obesity. However, the mechanisms by which high-fat diet induced peripheral signals affect the hypothalamic arcuate nucleus remain largely unknown. In this chapter, besides lipids and leptin, the role of glucose and insulin on specialized fuel-sensing neurons of hypothalamic neuronal circuits has been debated.

Brain Regulation of Energy Metabolism

In healthy individuals, energy intake is in balance with energy expenditure, which helps to maintain a normal body weight. The brain's inability to control energy homeostasis underlies the pathology of hyperphagia and obesity. The brain detects body energy excess and deficit by sensing the levels of circulating metabolic hormones and nutrients and by receiving metabolic information from the periphery via the autonomic nervous system. A specialized neuronal network coordinates energy intake behavior and the metabolic processes affecting energy expenditure. Here, we briefly review neuronal mechanisms by which our body maintains energy balance.

Recent advances in targeting the fatty acid biosynthetic pathway using fatty acid synthase inhibitors

INTRODUCTION

Elevated lipogenesis has been associated with a variety of diseases including obesity, cancer and nonalcoholic fatty liver disease (NAFLD). Fatty acid synthase (FASN) plays a pivotal role in de novo lipogenesis, making this multi-catalytic protein an attractive target for therapeutic intervention. Recently, the first FASN inhibitor successfully advanced through the drug development process and entered clinical evaluation in oncology. Areas covered: This review discusses the biological roles of FASN in three prominent disease areas: cancer, obesity-related disorders and NAFLD. Recent advances in drug discovery strategies and design of newer FASN inhibitors are also highlighted. Expert opinion: Despite the abundance of evidence linking the lipogenic pathway to cancer, progression of FASN-targeted molecules has been rather slow and challenging and no compounds have moved past the preclinical phase. The landscape has recently changed with the recent advancement of the first FASN inhibitor into clinical evaluation for solid tumors. Needless to say, the successful translation into the clinical setting will open opportunities for expanding the therapeutic utility of FASN inhibitors not just in oncology but in other diseases associated with elevated lipogenesis such as obesity, type 2 diabetes, and NAFLD.

Hypothalamic AMPK as a Regulator of Energy Homeostasis

Activated in energy depletion conditions, AMP-activated protein kinase (AMPK) acts as a cellular energy sensor and regulator in both central nervous system and peripheral organs. Hypothalamic AMPK restores energy balance by promoting feeding behavior to increase energy intake, increasing glucose production, and reducing thermogenesis to decrease energy output. Besides energy state, many hormones have been shown to act in concert with AMPK to mediate their anorexigenic and orexigenic central effects as well as thermogenic influences. Here we explore the factors that affect hypothalamic AMPK activity and give the underlying mechanisms for the role of central AMPK in energy homeostasis together with the physiological effects of hypothalamic AMPK on energy balance restoration.

The Role of Circulating Amino Acids in the Hypothalamic Regulation of Liver Glucose Metabolism

A pandemic of diabetes and obesity has been developing worldwide in close association with excessive nutrient intake and a sedentary lifestyle. Variations in the protein content of the diet have a direct impact on glucose homeostasis because amino acids (AAs) are powerful modulators of insulin action. In this work we review our recent findings on how elevations in the concentration of the circulating AAs leucine and proline activate a metabolic mechanism located in the mediobasal hypothalamus of the brain that sends a signal to the liver via the vagus nerve, which curtails glucose output. This neurogenic signal is strictly dependent on the metabolism of leucine and proline to acetyl-coenzyme A (CoA) and the subsequent production of malonyl-CoA; the signal also requires functional neuronal ATP-sensitive potassium channels. The liver then responds by lowering the rate of gluconeogenesis and glycogenolysis, ultimately leading to a net decrease in glucose production and in concentrations of circulating glucose. Furthermore, we review here how our work with proline suggests a new role of astrocytes in the central regulation of glycemia. Last, we outline how factors such as the consumption of fat-rich diets can interfere with glucoregulatory mechanisms and, in the long term, may contribute to the development of hyperglycemia, a hallmark of type 2 diabetes.

Obesity development in neuron-specific lipoprotein lipase deficient mice is not responsive to increased dietary fat content or change in fat composition

We have previously reported that mice with neuron-specific LPL deficiency (NEXLPL-/-) become obese by 16weeks of age on chow. Moreover, these mice had reduced uptake of triglyceride (TG)-rich lipoprotein-derived fatty acids and lower levels of n-3 long chain polyunsaturated fatty acids (n-3 PUFAs) in the hypothalamus. Here, we asked whether increased dietary fat content or altered dietary composition could modulate obesity development in NEXLPL-/- mice. Male NEXLPL-/- mice and littermate controls (WT) were randomly assigned one of three synthetic diets; a high carbohydrate diet (HC, 10% fat), a high-fat diet (HF, 45% fat), or a HC diet supplemented with n-3 PUFAs (HCn-3, 10% fat, Lovaza, GSK®). After 42weeks of HC feeding, body weight and fat mass were increased in the NEXLPL-/- mice compared to WT. WT mice fed a HF diet displayed typical diet-induced obesity, but weight gain was only marginal in HF-fed NEXLPL-/- mice, with no significant difference in body composition. Dietary n-3 PUFA supplementation did not prevent obesity in NEXLPL-/- mice, but was associated with differential modifications in hypothalamic gene expression and PUFA concentration compared to WT mice. Our findings suggest that neuronal LPL is involved in the regulation of body weight and composition in response to either the change in quantity (HF feeding) or quality (n-3 PUFA-enriched) of dietary fat. The precise role of LPL in lipid sensing in the brain requires further investigation.

Hypothalamic AMPK: a canonical regulator of whole-body energy balance

AMP-activated protein kinase (AMPK) has a major role in the modulation of energy balance. AMPK is activated in conditions of low energy, increasing energy production and reducing energy consumption. The AMPK pathway is a canonical route regulating energy homeostasis by integrating peripheral signals, such as hormones and metabolites, with neuronal networks. Current evidence has implicated AMPK in the hypothalamus and hindbrain with feeding, brown adipose tissue thermogenesis and browning of white adipose tissue, through modulation of the sympathetic nervous system, as well as glucose homeostasis. Interestingly, several potential antiobesity and/or antidiabetic agents, some of which are currently in clinical use such as metformin and liraglutide, exert some of their actions by acting on AMPK. Furthermore, the orexigenic and weight-gain effects of commonly used antipsychotic drugs are also mediated by hypothalamic AMPK. Overall, this evidence suggests that hypothalamic AMPK signalling is an interesting target for drug development, but is this approach feasible? In this Review we discuss the current understanding of hypothalamic AMPK and its role in the central regulation of energy balance and metabolism.

Differential gene regulation of GHSR signaling pathway in the arcuate nucleus and NPY neurons by fasting, diet-induced obesity, and 17β-estradiol

Ghrelin's receptor, growth hormone secretagogue receptor (GHSR), is highly expressed in the arcuate nucleus (ARC) and in neuropeptide Y (NPY) neurons. Fasting, diet-induced obesity (DIO), and 17β-estradiol (E2) influence ARC Ghsr expression. It is unknown if these effects occur in NPY neurons. Therefore, we examined the expression of Npy, Agrp, and GHSR signaling pathway genes after fasting, DIO, and E2 replacement in ARC and pools of NPY neurons. In males, fasting increased ARC Ghsr and NPY Foxo1 but decreased NPY Ucp2. In males, DIO decreased ARC and NPY Ghsr and Cpt1c. In fed females, E2 increased Agrp, Ghsr, Cpt1c, and Foxo1 in ARC. In NPY pools, E2 decreased Foxo1 in fed females but increased Foxo1 in fasted females. DIO in females suppressed Agrp and augmented Cpt1c in NPY neurons. In summary, genes involved in GHSR signaling are differentially regulated between the ARC and NPY neurons in a sex-dependent manner.

Imbalanced insulin action in chronic over nutrition: Clinical harm, molecular mechanisms, and a way forward

The growing worldwide prevalence of overnutrition and underexertion threatens the gains that we have made against atherosclerotic cardiovascular disease and other maladies. Chronic overnutrition causes the atherometabolic syndrome, which is a cluster of seemingly unrelated health problems characterized by increased abdominal girth and body-mass index, high fasting and postprandial concentrations of cholesterol- and triglyceride-rich apoB-lipoproteins (C-TRLs), low plasma HDL levels, impaired regulation of plasma glucose concentrations, hypertension, and a significant risk of developing overt type 2 diabetes mellitus (T2DM). In addition, individuals with this syndrome exhibit fatty liver, hypercoagulability, sympathetic overactivity, a gradually rising set-point for body adiposity, a substantially increased risk of atherosclerotic cardiovascular morbidity and mortality, and--crucially--hyperinsulinemia. Many lines of evidence indicate that each component of the atherometabolic syndrome arises, or is worsened by, pathway-selective insulin resistance and responsiveness (SEIRR). Individuals with SEIRR require compensatory hyperinsulinemia to control plasma glucose levels. The result is overdrive of those pathways that remain insulin-responsive, particularly ERK activation and hepatic de-novo lipogenesis (DNL), while carbohydrate regulation deteriorates. The effects are easily summarized: if hyperinsulinemia does something bad in a tissue or organ, that effect remains responsive in the atherometabolic syndrome and T2DM; and if hyperinsulinemia might do something good, that effect becomes resistant. It is a deadly imbalance in insulin action. From the standpoint of human health, it is the worst possible combination of effects. In this review, we discuss the origins of the atherometabolic syndrome in our historically unprecedented environment that only recently has become full of poorly satiating calories and incessant enticements to sit. Data are examined that indicate the magnitude of daily caloric imbalance that causes obesity. We also cover key aspects of healthy, balanced insulin action in liver, endothelium, brain, and elsewhere. Recent insights into the molecular basis and pathophysiologic harm from SEIRR in these organs are discussed. Importantly, a newly discovered oxide transport chain functions as the master regulator of the balance amongst different limbs of the insulin signaling cascade. This oxide transport chain--abbreviated 'NSAPP' after its five major proteins--fails to function properly during chronic overnutrition, resulting in this harmful pattern of SEIRR. We also review the origins of widespread, chronic overnutrition. Despite its apparent complexity, one factor stands out. A sophisticated junk food industry, aided by subsidies from willing governments, has devoted years of careful effort to promote overeating through the creation of a new class of food and drink that is low- or no-cost to the consumer, convenient, savory, calorically dense, yet weakly satiating. It is past time for the rest of us to overcome these foes of good health and solve this man-made epidemic.

S-nitrosylation of fatty acid synthase regulates its activity through dimerization

NO regulates a variety of physiological processes, including cell proliferation, differentiation, and inflammation. S-nitrosylation, a NO-mediated reversible protein modification, leads to changes in the activity and function of proteins. In particular, the role of S-nitrosylation during adipogenesis is largely unknown. We hypothesized that the normal physiological levels of NO, but not the excess levels generated under severe conditions, such as inflammation, may be critically involved in the proper regulation of adipogenesis. We found that endogenous S-nitrosylation of proteins was required for adipocyte differentiation. By performing a biotin-switch assay, we identified FAS, a key lipogenic enzyme in adipocytes, as a target of S-nitrosylation during adipogenesis. Interestingly, we also observed that the dimerization of FAS increased in parallel with the amount of S-nitrosylated FAS during adipogenesis. In addition, we found that exogenous NO enhanced the dimerization and the enzymatic activity of FAS. Moreover, site-directed mutagenesis of three predicted S-nitrosylation sites indicated that S-nitrosylation of FAS at Cys(1471)and Cys(2091), but not at Cys(1127), increased its enzymatic activity. Taken together, these results suggest that the S-nitrosylation of FAS at normal physiological levels of NO increases its activity through dimerization and may contribute to the proper regulation of adipogenesis.