Short-Term Fructose Feeding Induces Inflammation and Oxidative Stress in the Hippocampus of Young and Adult Rats

Pregestational fructose-induced metabolic syndrome in Wistar rats causes sexually dimorphic behavioral changes in their offspring

Metabolic syndrome (MetS), marked by enduring metabolic inflammation, has detrimental effects on cognitive performance and brain structure, influencing behavior. This study aimed to investigate whether maternal MetS could negatively impact the neurodevelopment and metabolism of offspring. To test this hypothesis, 2 months old female Wistar rats were subjected to a 10-week regimen of tap water alone or supplemented with 20% fructose to induce MetS. Dams were mated with healthy males to generate litters: OC (offspring from control dams) and OMetS (offspring from dams with MetS). To isolate prenatal effects, all pups were breastfed by control nurse dams, maintaining a standard diet and water ad libitum until weaning. Behavioral assessments were conducted between postnatal days (PN) 22 and 95, and metabolic parameters were analyzed post-sacrifice on PN100. Results from the elevated plus maze, the open field, and the marble burying tests revealed a heightened anxiety-like phenotype in OMetS females. The novel object recognition test showed that exclusively OMetS males had long-term memory impairment. In the reciprocal social interaction test, OMetS displayed a lower number of social interactions, with a notable increase in "socially inactive" behavior observed exclusively in females. Additionally, in the three-chamber test, social preference and social novelty indexes were found to be lower solely among OMetS females. An increase in visceral fat concomitantly with hypertriglyceridemia was the relevant postmortem metabolic finding in OMetS females. In summary, maternal MetS leads to enduring damage and adverse effects on offspring neurobehavior and metabolism, with notable sexual dimorphism.

Mechanisms Underlying Memory Impairment Induced by Fructose

Fructose consumption has increased over the years, especially in adolescents living in urban areas. Growing evidence indicates that daily fructose consumption leads to some pathological conditions, including memory impairment. This review summarizes relevant data describing cognitive deficits after fructose intake and analyzes the underlying neurobiological mechanisms. Preclinical experiments show sex-related deficits in spatial memory; that is, while males exhibit significant imbalances in spatial processing, females seem unaffected by dietary supplementation with fructose. Recognition memory has also been evaluated; however, only female rodents show a significant decline in the novel object recognition test performance. According to mechanistic evidence, fructose intake induces neuroinflammation, mitochondrial dysfunction, and oxidative stress in the short term. Subsequently, these mechanisms can trigger other long-term effects, such as inhibition of neurogenesis, downregulation of trophic factors and receptors, weakening of synaptic plasticity, and long-term potentiation decay. Integrating all these neurobiological mechanisms will help us understand the cellular and molecular processes that trigger the memory impairment induced by fructose.

High sugar consumption for seven days in adult mice increased blood glucose variability, induced an anxiolytic effect and triggered oxidative stress in cerebral cortex

Brain function is highly altered by glucose toxicity related to diabetes. High consumption of sugar in normal conditions is suspected to affect as well brain integrity. The present study investigates the possible effects of short-term exposure to high sugar diet on brain redox homeostasis in healthy mice. Male adult healthy mice were divided into two groups: control (CG) and sugar-exposed group (SG), that was exposed continually to 10% of glucose in drinking water for 7 days and 20% sucrose pellets food. Behavior, blood glucose variability and cerebral cortex oxidative stress biomarkers were measured at the end of exposure. Animals exposed to the high sugar diet expressed a significant increase in blood glucose levels and high glucose variability compared to control. These animals expressed as well anxiolytic behavior as revealed by the plus maze test. Exposure to the sugar diet altered redox homeostasis in the brain cortex as revealed by an increase in lipid peroxidation and the activity of antioxidant enzymes superoxide dismutase (SOD) and glutathione-s-transferase (GST). On the other hand, catalase (CAT) activity was decreased, and reduced glutathione (GSH) level was not altered compared to control. Further studies are required to understand the mechanisms trigging oxidative stress (OS) in the brain in response to short term exposure to high sugar diet and glucose fluctuations.

Limosilactobacillus reuteri DSM 17938 relieves inflammation, endoplasmic reticulum stress, and autophagy in hippocampus of western diet-fed rats by modulation of systemic inflammation

The consumption of western diets, high in fats and sugars, is a crucial contributor to brain molecular alterations, cognitive dysfunction and neurodegenerative diseases. Therefore, a mandatory challenge is the individuation of strategies capable of preventing diet-induced impairment of brain physiology. A promising strategy might consist in the administration of probiotics that are known to influence brain function via the gut-brain axis. In this study, we explored whether Limosilactobacillus reuteri DSM 17938 (L. reuteri)-based approach can counteract diet-induced neuroinflammation, endoplasmic reticulum stress (ERS), and autophagy in hippocampus, an area involved in learning and memory, in rat fed a high fat and fructose diet. The western diet induced a microbiota reshaping, but L. reuteri neither modulated this change, nor the plasma levels of short-chain fatty acids. Interestingly, pro-inflammatory signaling pathway activation (increased NFkB phosphorylation, raised amounts of toll-like receptor-4, tumor necrosis factor-alpha, interleukin-6, GFAP, and Haptoglobin), as well as activation of ERS (increased PERK and eif2α phosphorylation, higher C/EBP-homologous protein amounts) and autophagy (increased beclin, P62-sequestosome-1, and LC3 II) was revealed in hippocampus of western diet fed rats. All these hippocampal alterations were prevented by L. reuteri administration, showing for the first time a neuroprotective role of this specific probiotic strain, mainly attributable to its ability to regulate western diet-induced metabolic endotoxemia and systemic inflammation, as decreased levels of lipopolysaccharide, plasma cytokines, and adipokines were also found. Therapeutic strategies based on the use of L. reuteri DSM17938 could be beneficial in reversing metabolic syndrome-mediated brain dysfunction and cognitive decline.

Fructose overconsumption-induced reprogramming of microglia metabolism and function

The overconsumption of dietary fructose has been proposed as a major culprit for the rise of many metabolic diseases in recent years, yet the relationship between a high fructose diet and neurological dysfunction remains to be explored. Although fructose metabolism mainly takes place in the liver and intestine, recent studies have shown that a hyperglycemic condition could induce fructose metabolism in the brain. Notably, microglia, which are tissue-resident macrophages (Mφs) that confer innate immunity in the brain, also express fructose transporters (GLUT5) and are capable of utilizing fructose as a carbon fuel. Together, these studies suggest the possibility that a high fructose diet can regulate the activation and inflammatory response of microglia by metabolic reprogramming, thereby altering the susceptibility of developing neurological dysfunction. In this review, the recent advances in the understanding of microglia metabolism and how it supports its functions will be summarized. The results from both in vivo and in vitro studies that have investigated the mechanistic link between fructose-induced metabolic reprogramming of microglia and its function will then be reviewed. Finally, areas of controversies and their associated implications, as well as directions that warrant future research will be highlighted.

Microglial activation and toll-like receptor 4-Dependent regulation of angiotensin II type I receptor-mu-opioid receptor 1 heterodimerization and hypertension in fructose-fed rats

Our previous study reported that the heterodimer of Angiotensin II Type I Receptor (AT1R) and Mu-Opioid Receptor 1 (MOR1) involves Nitric Oxide (NO) reduction which leads to elevation of blood pressure. Secondly, we showed that Toll-like Receptor 4 (TLR4) may be involved in the heterodimerization of AT1R and MOR1 in the brainstem Nucleus Tractus Solitarii (NTS), which regulates systemic blood pressure and gastric nitric oxide through the insulin pathway. Here, we investigated the role of microglial activation and TLR4 in the heterodimerization of AT1R and MOR1. Hypertensive rats were established after four weeks of fructose consumption. SBP of rats was measured using non-invasive blood pressure method. PLA technique was utilized to determine protein-protein interaction in the nucleus tractus solitarii. Results showed that the level of MOR-1 and AT1R was induced significantly in the fructose group compared with control. PLA signal potentially showed that AT1R and MOR1 were formed in the nucleus tractus solitarii after fructose consumption. Meanwhile, the innate immune cell in the CNS microglia was observed in the nucleus tractus solitarii using biomarkers and was activated. TLR4 inhibitor CLI-095, was administered to animals to suppress the neuroinflammation and microglial activation. CLI-095 treatment reduced the heterodimer formation of AT1R and MOR1 and restored nitric oxide production in the nucleus tractus solitarii. These findings imply that TLR4-primed neuroinflammation involves formation of heterodimers AT1R and MOR1 in the nucleus tractus solitarii which leads to increase in systemic blood pressure.

Impact of Sustained Fructose Consumption on Gastrointestinal Function and Health in Wistar Rats: Glycoxidative Stress, Impaired Protein Digestion, and Shifted Fecal Microbiota

The gastrointestinal tract (GIT) is the target of assorted pathological conditions, and dietary components are known to affect its functionality and health. In previous in vitro studies, we observed that reducing sugars induced protein glycoxidation and impaired protein digestibility. To gain further insights into the pathophysiological effects of dietary sugars, Wistar rats were provided with a 30% (w/v) fructose water solution for 10 weeks. Upon slaughter, in vivo protein digestibility was assessed, and the entire GIT (digests and tissues) was analyzed for markers of oxidative stress and untargeted metabolomics. Additionally, the impact of sustained fructose intake on colonic microbiota was also evaluated. High fructose intake for 10 weeks decreased protein digestibility and promoted changes in the physiological digestion of proteins, enhancing intestinal digestion rather than stomach digestion. Moreover, at colonic stages, the oxidative stress was harmfully increased, and both the microbiota and the intraluminal colonic metabolome were modified.

Lipid peroxidation and neuroinflammation: A possible link between maternal fructose intake and delay of acquisition of neonatal reflexes in Wistar female rats

Fructose is a common sweetener found in the daily diet supplemented to many processed and ultra-processed foods and beverages. Consumption of fructose-sweetened beverages has drastically increased in the last decades and is widely associated with metabolic disease, systemic pro-inflammatory status, and adverse transgenerational effects. To date, the impact of maternal fructose intake in brain function of the offspring is less explored. Therefore, the aim of this study was first, to investigate adverse effects in developmental milestones of the progeny of mothers with metabolic syndrome (MetS), induced by ad libitum consumption of a 20% fructose solution, and second to identify possible molecular changes in the nervous system of the newborns associated with maternal fructose intake. Wistar rats were randomly separated into two groups with access to water or fructose (20% w/v in water) for 10 weeks. After MetS was confirmed, dams were mated with control males and continued drinking water or fructose solution during gestation. At postnatal day (PN) 1, a subgroup of offspring of each sex was sacrificed and brains were dissected for oxidative stress and inflammatory status analysis. Changes in the developmental milestones due to maternal fructose consumption were studied (PN3-PN21) in another subgroup of offspring. Sexually dimorphic effects were found on the progeny's acquisition of neurodevelopmental milestones, in brain lipid peroxidation, neuroinflammation, and antioxidative defensive response. Our results suggest that dams' MetS, induced by fructose intake, disrupts brain redox homeostasis in female offspring and affects sensorimotor brain circuitry which may have a translational value for studying neurodevelopmental diseases.

Dietary patterns, brain morphology and cognitive performance in children: Results from a prospective population-based study

Dietary patterns in childhood have been associated with child neurodevelopment and cognitive performance, while the underlying neurobiological pathway is unclear. We aimed to examine associations of dietary patterns in infancy and mid-childhood with pre-adolescent brain morphology, and whether diet-related differences in brain morphology mediate the relation with cognition. We included 1888 and 2326 children with dietary data at age one or eight years, respectively, and structural neuroimaging at age 10 years in the Generation R Study. Measures of brain morphology were obtained using magnetic resonance imaging. Dietary intake was assessed using food-frequency questionnaires, from which we derived diet quality scores based on dietary guidelines and dietary patterns using principal component analyses. Full scale IQ was estimated using the Wechsler Intelligence Scale for Children-Fifth Edition at age 13 years. Children with higher adherence to a dietary pattern labeled as 'Snack, processed foods and sugar' at age one year had smaller cerebral white matter volume at age 10 (B = -4.3, 95%CI -6.9, -1.7). At age eight years, higher adherence to a 'Whole grains, soft fats and dairy' pattern was associated with a larger total brain (B = 8.9, 95%CI 4.5, 13.3), and larger cerebral gray matter volumes at age 10 (B = 5.2, 95%CI 2.9, 7.5). Children with higher diet quality and better adherence to a 'Whole grains, soft fats and dairy' dietary pattern at age eight showed greater brain gyrification and larger surface area, clustered primarily in the dorsolateral prefrontal cortex. These observed differences in brain morphology mediated associations between dietary patterns and IQ. In conclusion, dietary patterns in early- and mid-childhood are associated with differences in brain morphology which may explain the relation between dietary patterns and neurodevelopment in children.

Age-Dependent Skeletal Muscle Mitochondrial Response to Short-Term Increased Dietary Fructose

The harmful effect of a long-term high-fructose diet is well established, but the age-dependent physiological responses that can be triggered by a short-term high-fructose diet in skeletal muscles have not been deeply explored. Therefore, the aim of this work was to compare the alterations in mitochondrial energetic and insulin responsiveness in the skeletal muscle induced by a short-term (2 weeks) fructose feeding in rats of different ages. For this purpose, fructose and uric acid levels, insulin sensitivity, mitochondrial bioenergetics and oxidative status were evaluated in the skeletal muscles from young (30 days old) and adult (90 days old) rats. We showed that, even in the short term, a high-fructose diet has a strong impact on skeletal muscle metabolism, with more marked effects in young rats than in adults ones. In fact, despite both groups showing a decrease in insulin sensitivity, the marked mitochondrial dysfunction was found only in the young rats, thus leading to an increase in the mitochondrial production of ROS, and therefore, in oxidative damage. These findings underscore the need to reduce fructose consumption, especially in young people, to preserve the maintenance of a metabolically healthy status.

Fructose Diet-Associated Molecular Alterations in Hypothalamus of Adolescent Rats: A Proteomic Approach

BACKGROUND

The enhanced consumption of fructose as added sugar represents a major health concern. Due to the complexity and multiplicity of hypothalamic functions, we aim to point out early molecular alterations triggered by a sugar-rich diet throughout adolescence, and to verify their persistence until the young adulthood phase.

METHODS

Thirty days old rats received a high-fructose or control diet for 3 weeks. At the end of the experimental period, treated animals were switched to the control diet for further 3 weeks, and then analyzed in comparison with those that were fed the control diet for the entire experimental period.

RESULTS

Quantitative proteomics identified 19 differentially represented proteins, between control and fructose-fed groups, belonging to intermediate filament cytoskeleton, neurofilament, pore complex and mitochondrial respiratory chain complexes. Western blotting analysis confirmed proteomic data, evidencing a decreased abundance of mitochondrial respiratory complexes and voltage-dependent anion channel 1, the coregulator of mitochondrial biogenesis PGC-1α, and the protein subunit of neurofilaments α-internexin in fructose-fed rats. Diet-associated hypothalamic inflammation was also detected. Finally, the amount of brain-derived neurotrophic factor and its high-affinity receptor TrkB, as well as of synaptophysin, synaptotagmin, and post-synaptic protein PSD-95 was reduced in sugar-fed rats. Notably, deregulated levels of all proteins were fully rescued after switching to the control diet.

CONCLUSIONS

A short-term fructose-rich diet in adolescent rats induces hypothalamic inflammation and highly affects mitochondrial and cytoskeletal compartments, as well as the level of specific markers of brain function; above-reported effects are reverted after switching animals to the control diet.

Fructose diet ameliorate effects of macrophage migration inhibitory factor deficiency on prefrontal cortex inflammation, neural plasticity, and behavior in male mice

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that represents a link between diet-induced inflammation and insulin resistance. Our aim was to examine whether fructose diet affects inflammation and insulin signaling in the prefrontal cortex (PFC) of Mif knockout mice (MIF-KO), and their possible link to neural plasticity and behavior. We analyzed nuclear factor κB (NF-κB) and glucocorticoid signaling, expression of F4/80, IL-1β, TNF-α, TLR-4, MyD88, arginase 1 (Arg-1), mannose receptor (Mrc-1), and leukemia inhibitory factor (Lif) to assess inflammation in the PFC of C57/BL6J and MIF-KO mice consuming 20% fructose solution for 9 weeks. Insulin receptor (IR), IRS-1 serine phosphorylations (307 and 1101) and activity of PKCα, Akt, GSK-3β and AMPKα were used to analyze insulin signaling. Brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF-1) mRNA levels, together with synapthophysin and PSD-95 protein level and calcium calmodulin-dependent kinase 2 (CaMKII) activity, were used as plasticity markers. Behavior was examined in elevated plus maze, light dark box and novel object recognition test. The results showed concomitant increase of Tnf-α, Tlr-4, MyD88 and M2 microglia markers (Arg-1, Mrc-1, Lif) in the PFC of MIF-KO, paralleled with unchanged glucocorticoid and insulin signaling. Increase of BDNF and IGF-1 was paralleled with increased CaMKII activity, decreased PSD-95 protein level, anxiogenic behavior, and impaired memory in MIF-KO mice. Fructose feeding restored these parameters in the PFC to the control level and mitigated behavioral changes, suggesting that ameliorating effects of fructose on neuroinflammation and behavior depend on the presence of MIF.

Long-Lasting Impact of Sugar Intake on Neurotrophins and Neurotransmitters from Adolescence to Young Adulthood in Rat Frontal Cortex

The detrimental impact of fructose, a widely used sweetener in industrial foods, was previously evidenced on various brain regions. Although adolescents are among the highest consumers of sweet foods, whether brain alterations induced by the sugar intake during this age persist until young adulthood or are rescued returning to a healthy diet remains largely unexplored. To shed light on this issue, just weaned rats were fed with a fructose-rich or control diet for 3 weeks. At the end of the treatment, fructose-fed rats underwent a control diet for a further 3 weeks until young adulthood phase and compared with animals that received from the beginning the healthy control diet. We focused on the consequences induced by the sugar on the main neurotrophins and neurotransmitters in the frontal cortex, as its maturation continues until late adolescence, thus being the last brain region to achieve a full maturity. We observed that fructose intake induces inflammation and oxidative stress, alteration of mitochondrial function, and changes of brain-derived neurotrophic factor (BDNF) and neurotrophin receptors, synaptic proteins, acetylcholine, dopamine, and glutamate levels, as well as increased formation of the glycation end-products Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL). Importantly, many of these alterations (BDNF, CML, CEL, acetylcholinesterase activity, dysregulation of neurotransmitters levels) persisted after switching to the control diet, thus pointing out to the adolescence as a critical phase, in which extreme attention should be devoted to limit an excessive consumption of sweet foods that can affect brain physiology also in the long term.

Short-term fructose feeding alters tissue metabolic pathways by modulating microRNAs expression both in young and adult rats

Dietary high fructose (HFrD) is known as a metabolic disruptor contributing to the development of obesity, diabetes, and dyslipidemia. Children are more sensitive to sugar than adults due to the distinct metabolic profile, therefore it is especially relevant to study the metabolic alterations induced by HFrD and the mechanisms underlying such changes in animal models of different ages. Emerging research suggests the fundamental role of epigenetic factors such as microRNAs (miRNAs) in metabolic tissue injury. In this perspective, the aim of the present study was to investigate the involvement of miR-122-5p, miR-34a-5p, and miR-125b-5p examining the effects induced by fructose overconsumption and to evaluate whether a differential miRNA regulation exists between young and adult animals. We used young rats (30 days) and adult rats (90 days) fed on HFrD for a short period (2 weeks) as animal models. The results indicate that both young and adult rats fed on HFrD exhibit an increase in systemic oxidative stress, the establishment of an inflammatory state, and metabolic perturbations involving the relevant miRNAs and their axes. In the skeletal muscle of adult rats, HFrD impair insulin sensitivity and triglyceride accumulation affecting the miR-122-5p/PTP1B/P-IRS-1(Tyr612) axis. In liver and skeletal muscle, HFrD acts on miR-34a-5p/SIRT-1: AMPK pathway resulting in a decrease of fat oxidation and an increase in fat synthesis. In addition, liver and skeletal muscle of young and adult rats exhibit an imbalance in antioxidant enzyme. Finally, HFrD modulates miR-125b-5p expression levels in liver and white adipose tissue determining modifications in de novo lipogenesis. Therefore, miRNA modulation displays a specific tissue trend indicative of a regulatory network that contributes in targeting genes of various pathways, subsequently yielding extensive effects on cell metabolism.

Activation of farnesoid X receptor suppresses ER stress and inflammation via the YY1/NCK1/PERK pathway in large yellow croaker (Larimichthys crocea)

Unfolded protein responses from endoplasmic reticulum (ER) stress have been implicated in inflammatory signaling. The vicious cycle of ER stress and inflammation makes regulation even more difficult. This study examined effects of farnesoid X receptor (FXR) in ER-stress regulation in large yellow croakers. The soybean-oil-diet-induced expression of ER stress markers was decreased in fish with FXR activated. In croaker macrophages, FXR activation or overexpression significantly reduced inflammation and ER stress caused by tunicamycin (TM), which was exacerbated by FXR knockdown. Further investigation showed that the TM-induced phosphorylation of PERK and EIF2α was inhibited by the overexpression of croaker FXR, and it was increased by FXR knockdown. Croaker NCK1 was then confirmed to be a regulator of PERK, and its expression in macrophages is increased by FXR overexpression and decreased by FXR knockdown. The promoter activity of croaker NCK1 was inhibited by yin-yang 1 (YY1). Furthermore, the results show that croaker FXR overexpression could suppress the P65-induced promoter activity of YY1 in HEK293t cells and decrease the TM-induced expression of yy1 in macrophages. These results indicate that FXR could suppress P65-induced yy1 expression and then increase NCK1 expression, thereby inhibiting the PERK pathway. This study may benefit the understanding of ER stress regulation in fish, demonstrating that FXR can be used in large yellow croakers as an effective target for regulating ER stress and inflammation.

Aging Increases Susceptibility to Develop Cardiac Hypertrophy following High Sugar Consumption

Aging and poor diet are independent risk factors for heart disease, but the impact of high-sucrose (HS) consumption in the aging heart is understudied. Aging leads to impairments in mitochondrial function that result in muscle dysfunction (e.g., cardiac remodeling and sarcopenia). We tested whether HS diet (60%kcal sucrose) would accelerate muscle dysfunction in 24-month-old male CB6F1 mice. By week 1 on HS diet, mice developed significant cardiac hypertrophy compared to age-matched chow-fed controls. The increased weight of the heart persisted throughout the 4-week treatment, while body weight and strength declined more rapidly than controls. We then tested whether HS diet could worsen cardiac dysfunction in old mice and if the mitochondrial-targeted drug, elamipretide (ELAM), could prevent the diet-induced effect. Old and young mice were treated with either ELAM or saline as a control for 2 weeks, and provided with HS diet or chow on the last week. As demonstrated in the previous experiment, old mice had age-related cardiac hypertrophy that worsened after one week on HS and was prevented by ELAM treatment, while the HS diet had no detectable effect on hypertrophy in the young mice. As expected, mitochondrial respiration and reactive oxygen species (ROS) production were altered by age, but were not significantly affected by HS diet or ELAM. Our findings highlight the vulnerability of the aged heart to HS diet that can be prevented by systemic targeting of the mitochondria with ELAM.

A high-fat, high-fructose diet induced hepatic steatosis, renal lesions, dyslipidemia, and hyperuricemia in non-obese rats

Excessive consumption of fat and sugar is associated with various chronic diseases. However, the variation of fat and sugar content in the diet greatly affected the outcome. In this study, a high-fat, high-fructose diet (HFHFD) formula was made with a composition of 31.99% carbohydrate, 40.7% fat, 11.8% protein, and an additional 30% fructose drink to confirm the effects of HFHFD on metabolic health and pathological changes in organs, especially the liver, kidneys, pancreas, muscles, and spleen. A total of 24 male Wistar rats aged 8–12 weeks were divided into four groups: standard chow (SC), HFHFD, SC + carbon tetrachloride (CCl4), and HFHFD + CCl4. After eight weeks of dietary intervention, body mass index, obesity index, lipid profiles, liver function tests, fasting blood glucose, serum uric acid and urea levels, and tissue histopathology were examined. HFHFD with the main unsaturated fatty acids of linoleic acid (14.57%) and palmitoleic acid (8.28%), the main saturated fatty acids of stearic acid (13.62%) and myristic acid (10.09%), and a low trans-fatty acids content, did not promote the rats to become obese. However, liver histology examination showed severe hepatic steatosis (78.33%), leading to steatohepatitis accompanied by an increase in serum ALP (p < 0.01), triglyceride (p < 0.001), total cholesterol (p < 0.05), and uric acid (p < 0.001) levels. Other histological features showed moderate lesions (45%) of the kidney, slight vacuolization of the pancreas, and a mild increase of inflammatory cells in the spleen and muscle. So, this study found that although HFHFD did not promote obesity within 8 weeks of administration, it induced hepatic and renal lesions, dyslipidemia, and hyperuricemia as a metabolic consequence of excessive fatty acids and fructose.

Independent effects of sex and stress on fructose-induced salt-sensitive hypertension

Proximal tubule fructose metabolism is key to fructose-induced hypertension, but the roles of sex and stress are unclear. We hypothesized that females are resistant to the salt-sensitive hypertension caused by low amounts of dietary fructose compared to males and that the magnitude of the increase in blood pressure (BP) depends, in part, on amplification of the stress response of renal sympathetic nerves. We measured systolic BP (SBP) in rats fed high salt with either no sugar (HS), 20% glucose (GHS) or 20% fructose (FHS) in the drinking water for 7-8 days. FHS increased SBP in both males (Δ22 ± 9 mmHg; p < 0.046) and females (Δ16 ± 3 mmHg; p < 0.0007), while neither GHS nor HS alone induced changes in SBP in either sex. The FHS-induced increase in SBP as measured by telemetry in the absence of added stress (8 ± 2 mmHg) was significantly lower than that measured by plethysmography (24 ± 5 mmHg) (p < 0.014). However, when BP was measured by telemetry simulating the stress of plethysmography, the increase in SBP was significantly greater (15 ± 3 mmHg) than under low stress (8 ± 1 mmHg) (p < 0.014). Moderate-stress also increased telemetric diastolic (p < 0.006) and mean BP (p < 0.006) compared to low-stress in FHS-fed animals. Norepinephrine excretion was greater in FHS-fed rats than HS-fed animals (Male: 6.4 ± 1.7 vs.1.8 ± 0.4 nmole/kg/day; p < 0.02. Female 54 ± 18 vs. 1.2 ± 0.6; p < 0.02). We conclude that fructose-induced salt-sensitive hypertension is similar in males and females unlike other forms of hypertension, and the increase in blood pressure depends in part on an augmented response of the sympathetic nervous system to stress.

Ethanol Extract of Pinus koraiensis Leaves Mitigates High Fructose-Induced Hepatic Triglyceride Accumulation and Hypertriglyceridemia

Pinus koraiensis is a valuable plant source of functional health foods and medicinal materials. Hypertriglyceridemia affects about 15–20% of adults and is related to stroke, metabolic syndromes, cardiovascular diseases, and diabetes mellitus. Dietary fructose, a risk factor for developing hypertriglyceridemia, significantly increases postprandial triglyceride (TG) levels and aggravates non-alcoholic fatty liver disease. In this study, we aimed to analyze the effect of ethanol extract from P. koraiensis needles (EPK) on fructose (Fr)-induced cell culture and animal models, respectively. Our team determined the bioactivity, such as anti-cancer, anti-obesity, anti-diabetic, and anti-hyperlipidemic functions, of P. koraiensis needle extract. The EPK markedly reduced TG levels in the liver and serum and enhanced TG excretion through feces in high-fructose-fed rats. Furthermore, the EPK inhibited de novo lipogenesis and its markers—carbohydrate response element-binding protein (ChREBP), sterol regulatory element-binding protein 1 (SREBP-1), fatty acid synthase (FAS), 3-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR), and tumor necrosis factor-alpha (TNF-α), a pro-inflammatory marker. Consistent with the results of the in vivo experiment, the EPK decreased SREBP-1, ChREBP, HMGCR, FAS, TNF-α, and iNOS expression levels, resulting in slower lipid accumulation and lower TG levels in Fr-induced HepG2 cells. These findings suggest that EPK mitigates hypertriglyceridemia and hepatic TG accumulation by inhibiting de novo lipogenic and pro-inflammatory factors.

Glucose Stimulates Glial Cell Line-Derived Neurotrophic Factor Gene Expression in Microglia through a GLUT5-Independent Mechanism

Feeding-regulating neurotrophic factors are expressed in both neurons and glial cells. However, nutritional regulation of anorexigenic glial cell line-derived neurotrophic factor (GDNF) and orexigenic mesencephalic astrocyte-derived neurotrophic factor (MANF) expression in specific cell types remains poorly understood. Hypothalamic glucose sensing plays a critical role in the regulation of food intake. It has been theorized that local glucose concentration modulates microglial activity partially via glucose transporter 5 (GLUT5). We hypothesized that an increased local glucose concentration stimulates GDNF expression while inhibiting MANF expression in the hypothalamus and microglia via GLUT5. The present study investigated the effect of glucose on Gdnf and Manf mRNA expression in the mouse hypothalamus and murine microglial cell line SIM-A9. Intracerebroventricular glucose treatment significantly increased Gdnf mRNA levels in the hypothalamus without altering Manf mRNA levels. Exposure to high glucose caused a significant increase in Gdnf mRNA expression and a time-dependent change in Manf mRNA expression in SIM-A9 cells. GLUT5 inhibitor treatment did not block glucose-induced Gdnf mRNA expression in these cells. These findings suggest that microglia are responsive to changes in the local glucose concentration and increased local glucose availability stimulates the expression of microglial GNDF through a GLUT5-independent mechanism, contributing to glucose-induced feeding suppression.

Differential effects of excess high-fructose corn syrup on the DNA methylation of hippocampal neurotrophic factor in childhood and adolescence

Consumption of fructose-containing beverages such as high-fructose corn syrup (HFCS) is increasing, raising concerns about the negative effects of excessive fructose intake. A recent report indicated that excess HFCS intake impairs hippocampal function. In this study, we focused on neurotrophic factors (NFs) in the hippocampus from the viewpoint of epigenetics to clarify the adverse effects of fructose. We analyzed the effects of HFCS intake on hippocampal function in three age categories: childhood and adolescence (postnatal day (PD) 21–60), young adulthood (PD60-100), and late adulthood (PD100-140). For the experiments, male Sprague-Dawley rats were divided into three age categories, the control group was received distilled water and the HFCS group was received 20% HFCS solution for 40 days in each period. We analyzed mRNA and protein levels for qPCR and western blotting, respectively, of a hippocampal NF, brain-derived neurotrophic factor (Bdnf). HFCS consumption reduced hippocampal Bdnf mRNA and protein expressions in childhood and adolescence. Moreover, pyrosequencing assays revealed increased DNA methylation at the Bdnf promoter in childhood and adolescence. This Bdnf levels reduction may be due to hypermethylation of the promoter regions. It should be noted that this phenomenon was observed only in childhood and adolescence fructose consumption. Our results indicate that the sensitivity of the hippocampus to fructose may vary with age. This study provides insight into the adverse effects of excessive HFCS consumption on the hippocampus in children.

Masseter muscle and gingival tissue inflammatory response following treatment with high-fructose corn syrup in rats: Anti-inflammatory and antioxidant effects of kefir

The aim of the study was to evaluate whether high-fructose corn syrup (HFCS) intake (20% beverages) impacts antioxidative structures and inflammation in the gingival tissue and masseter muscle of rats. Kefir was tested for its potential utility on changes induced by HFCS. Animals were randomly divided into four groups as control, kefir, HFCS, and HFCS plus kefir. HFCS was given as 20% solutions in drinking water while kefir supplementations were given by gastric gavage for 8 weeks. It has been clearly determined that the HFCS diet increased expressions of interleukin (IL)-6, IL-1β, and tumor necrosis factor-α proinflammatory structures via lymphocyte infiltration by suppressing antioxidant enzymes such as catalase, superoxide dismutase, and glutathione peroxidase in both tissues. Kefir improved these undesirable changes in rats fed with HFCS. The results of this current study, the first investigation to examine the effects of kefir on masseter muscle and gingival tissue, may provide new access to the restorative effects of kefir consumption on oral health disorders caused by high fructose in the diet. PRACTICAL APPLICATIONS: In this study, at an early age, the effects of kefir on improving inflammation via antioxidation in the masseter muscle and gingival tissue were investigated for the first time. We showed that kefir feeding ameliorates lymphocyte infiltration on the high-fructose corn syrup (HFCS)-induced masseter muscle and gingival tissue inflammation in rats. The mRNA expressions of inflammatory parameters measured in the study were supported by protein measurements via ELISA or immunohistochemistry. In the present study, kefir may play an important role in the antioxidation and inflammation process on the masseter muscle and gingival tissue against HFCS.

Regulation of the Fructose Transporter Gene Slc2a5 Expression by Glucose in Cultured Microglial Cells

Microglia play a role in the regulation of metabolism and pathogenesis of obesity. Microglial activity is altered in response to changes in diet and the body’s metabolic state. Solute carrier family 2 member 5 (Slc2a5) that encodes glucose transporter 5 (GLUT5) is a fructose transporter primarily expressed in microglia within the central nervous system. However, little is known about the nutritional regulation of Slc2a5 expression in microglia and its role in the regulation of metabolism. The present study aimed to address the hypothesis that nutrients affect microglial activity by altering the expression of glucose transporter genes. Murine microglial cell line SIM-A9 cells and primary microglia from mouse brain were exposed to different concentrations of glucose and levels of microglial activation markers and glucose transporter genes were measured. High concentration of glucose increased levels of the immediate-early gene product c-Fos, a marker of cell activation, Slc2a5 mRNA, and pro-inflammatory cytokine genes in microglial cells in a time-dependent manner, while fructose failed to cause these changes. Glucose-induced changes in pro-inflammatory gene expression were partially attenuated in SIM-A9 cells treated with the GLUT5 inhibitor. These findings suggest that an increase in local glucose availability leads to the activation of microglia by controlling their carbohydrate sensing mechanism through both GLUT5-dependent and –independent mechanisms.

Dietary Regulation of Gut-Brain Axis in Alzheimer's Disease: Importance of Microbiota Metabolites

Alzheimer's disease (AD) is a neurodegenerative disease that impacts 45 million people worldwide and is ranked as the 6th top cause of death among all adults by the Centers for Disease Control and Prevention. While genetics is an important risk factor for the development of AD, environment and lifestyle are also contributing risk factors. One such environmental factor is diet, which has emerged as a key influencer of AD development/progression as well as cognition. Diets containing large quantities of saturated/trans-fats, refined carbohydrates, limited intake of fiber, and alcohol are associated with cognitive dysfunction while conversely diets low in saturated/trans-fats (i.e., bad fats), high mono/polyunsaturated fats (i.e., good fats), high in fiber and polyphenols are associated with better cognitive function and memory in both humans and animal models. Mechanistically, this could be the direct consequence of dietary components (lipids, vitamins, polyphenols) on the brain, but other mechanisms are also likely to be important. Diet is considered to be the single greatest factor influencing the intestinal microbiome. Diet robustly influences the types and function of micro-organisms (called microbiota) that reside in the gastrointestinal tract. Availability of different types of nutrients (from the diet) will favor or disfavor the abundance and function of certain groups of microbiota. Microbiota are highly metabolically active and produce many metabolites and other factors that can affect the brain including cognition and the development and clinical progression of AD. This review summarizes data to support a model in which microbiota metabolites influence brain function and AD.

Mitochondrial defects: An emerging theranostic avenue towards Alzheimer's associated dysregulations

Mitochondria play a crucial role in expediting the energy homeostasis under varying environmental conditions. As mitochondria are controllers of both energy production and apoptotic pathways, they are also distinctively involved in controlling the neuronal cell survival and/or death. Numerous factors are responsible for mitochondria to get degraded with aging and huge functional failures in mitochondria are also found to be associated with the commencement of numerous neurodegenerative conditions, including Alzheimer's disease (AD). A large number of existing literatures promote the pivotal role of mitochondrial damage and oxidative impairment in the pathogenesis of AD. Numerous mitochondria associated processes such as mitochondrial biogenesis, fission, fusion, mitophagy, transportation and bioenergetics are crucial for proper functioning of mitochondria but are reported to be defective in AD patients. Though, the knowledge on the precise and in-depth mechanisms of these actions is still in infancy. Based upon the outcome of various significant studies, mitochondria are also being considered as therapeutic targets for AD. Here, we review the current status of mitochondrial defects in AD and also summarize the possible role of these defects in the pathogenesis of AD. The various approaches for developing the mitochondria-targeted therapies are also discussed here in detail. Consequently, it is suggested that improving mitochondrial activity via pharmacological and/or non-pharmacological interventions could postpone the onset and slow the development of AD. Further research and consequences of ongoing clinical trials should extend our understanding and help to validate conclusions regarding the causation of AD.

Amyotrophic lateral sclerosis alters the metabolic aging profile in patient derived fibroblasts

Aging is a major risk factor for neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). As metabolic alterations are a hallmark of aging and have previously been observed in ALS, it is important to examine the effect of aging in the context of ALS metabolic function. Here, using a newly established phenotypic metabolic approach, we examined the effect of aging on the metabolic profile of fibroblasts derived from ALS cases compared to controls. We found that ALS fibroblasts have an altered metabolic profile, which is influenced by age. In control cases, we found significant increases with age in NADH metabolism in the presence of several metabolites including lactic acid, trehalose, uridine and fructose, which was not recapitulated in ALS cases. Conversely, we found a reduction of NADH metabolism with age of biopsy, age of onset and age of death in the presence of glycogen in the ALS cohort. Furthermore, we found that NADH production correlated with disease progression rates in relation to a number of metabolites including inosine and α-ketoglutaric acid. Inosine or α-ketoglutaric acid supplementation in ALS fibroblasts was bioenergetically favourable. Overall, we found aging related defects in energy substrates that feed carbon into glycolysis at various points as well as the tricarboxylic acid (TCA) cycle in ALS fibroblasts, which was validated in induced neuronal progenitor cell derived iAstrocytes. Our results suggest that supplementing those pathways may protect against age related metabolic dysfunction in ALS.

Neural mechanisms underlying the role of fructose in overfeeding

Fructose consumption has been linked with metabolic syndrome and obesity. Fructose-based sweeteners like high fructose corn syrup taste sweeter, improve food palatability, and are increasingly prevalent in our diet. The increase in fructose consumption precedes the rise in obesity and is a contributing driver to the obesity epidemic worldwide. The role of dietary fructose in obesity can be multifactorial by promoting visceral adiposity, hypertension, and insulin resistance. Interestingly, one emergent finding from human and animal studies is that dietary fructose promotes overfeeding. As the brain is a critical regulator of food intake, we reviewed the evidence that fructose can act in the brain and elucidated the major brain systems underlying fructose-induced overfeeding. We found that fructose acts on multiple interdependent brain systems to increase orexigenic drive and the incentive salience of food while decreasing the latency between food bouts and reducing cognitive control to disinhibit feeding. We concluded that the collective actions of fructose may promote feeding behavior by producing a hunger-like state in the brain.

Are fat and sugar just as detrimental in old age?

Aging and poor nutrition are independent risk factors for the development of chronic disease. When young animals are given diets high in fat or sugar, they exhibit hallmarks of aging like mitochondrial dysfunction and inflammation, and also develop a greater risk for age-related disease. The same mitochondrial dysfunction and inflammation that progress with aging may also further predispose older individuals to dietary insults by fat and sugar. The purpose of this work is to review the most recent studies that address the impact of fat and sugar consumption on hallmarks of aging (mitochondrial dysfunction and inflammation). Findings from these studies show that obesogenic, high-fat diets can exacerbate age-related disease and hallmarks of aging in young animals, but high-fat diets that are non-obesogenic may play a beneficial role in old age. In contrast, high-sugar diets do not require an obesogenic effect to induce mitochondrial dysfunction or inflammation in young rodents. Currently, there is a lack of experimental studies addressing the impact of sugar in the context of aging, even though empirical evidence points to the detrimental effect of sugar in aging by contributing to a variety of age-related diseases. Fig. 1 Mitochondrial dysfunction and altered cellular communication (e.g. inflammation) progress with advancing age and increase the risk for age-related disease (ARD). Given the physiological changes that occur with age, the impact of high-fat (HFD) and high-sugar diets (HSD) may differ in later and earlier stages of life. HFD can promote the development of hallmarks of aging in young animals and can also exacerbate the risk for ARD when consumed at an old age. However, non-obesogenic high-fat diets may also reduce the risk for ARD in old age by acting on these hallmarks of aging. On the other hand, HSD promotes mitochondrial dysfunction and inflammation without necessarily inducing weight gain in young animals. Empirical evidence points to sugar as a major contributor to age-related disease and more experimental studies are needed to clarify whether aged individuals are more susceptible to its effects.

Metforminium Decavanadate (MetfDeca) Treatment Ameliorates Hippocampal Neurodegeneration and Recognition Memory in a Metabolic Syndrome Model

The consumption of foods rich in carbohydrates, saturated fat, and sodium, accompanied by a sedentary routine, are factors that contribute to the progress of metabolic syndrome (MS). In this way, they cause the accumulation of body fat, hypertension, dyslipidemia, and hyperglycemia. Additionally, MS has been shown to cause oxidative stress, inflammation, and death of neurons in the hippocampus. Consequently, spatial and recognition memory is affected. It has recently been proposed that metformin decavanadate (MetfDeca) exerts insulin mimetic effects that enhance metabolism in MS animals; however, what effects it can cause on the hippocampal neurons of rats with MS are unknown. The objective of the work was to evaluate the effect of MetfDeca on hippocampal neurodegeneration and recognition memory in rats with MS. Administration of MetfDeca for 60 days in MS rats improved object recognition memory (NORt). In addition, MetfDeca reduced markers of oxidative stress and hippocampal neuroinflammation. Accompanied by an increase in the density and length of the dendritic spines of the hippocampus of rats with MS. We conclude that MetfDeca represents an important therapeutic agent to treat MS and induce neuronal and cognitive restoration mechanisms.

Catecholaminergic stimulation restores high-sucrose diet-induced hippocampal dysfunction

Increasing evidence suggests that long-term consumption of high-caloric diets increases the risk of developing cognitive dysfunctions. In the present study, we assessed the catecholaminergic activity in the hippocampus as a modulatory mechanism that is altered in rats exposed to six months of a high-sucrose diet (HSD). Male Wistar rats fed with this diet developed a metabolic disorder and showed impaired spatial memory in both water maze and object location memory (OLM) tasks. Intrahippocampal free-movement microdialysis showed a diminished dopaminergic and noradrenergic response to object exploration during OLM acquisition compared to rats fed with normal diet. In addition, electrophysiological results revealed an impaired long-term potentiation (LTP) of the perforant to dentate gyrus pathway in rats exposed to a HSD. Local administration of nomifensine, a catecholaminergic reuptake inhibitor, prior to OLM acquisition or LTP induction, improved long-term memory and electrophysiological responses, respectively. These results suggest that chronic exposure to HSD induces a hippocampal deterioration which impacts on cognitive and neural plasticity events negatively; these impairments can be ameliorated by increasing or restituting the affected catecholaminergic activity.

Fructose Removal from the Diet Reverses Inflammation, Mitochondrial Dysfunction, and Oxidative Stress in Hippocampus

Young age is often characterized by high consumption of processed foods and fruit juices rich in fructose, which, besides inducing a tendency to become overweight, can promote alterations in brain function. The aim of this study was therefore to (a) clarify brain effects resulting from fructose consumption in juvenile age, a critical phase for brain development, and (b) verify whether these alterations can be rescued after removing fructose from the diet. Young rats were fed a fructose-rich or control diet for 3 weeks. Fructose-fed rats were then fed a control diet for a further 3 weeks. We evaluated mitochondrial bioenergetics by high-resolution respirometry in the hippocampus, a brain area that is critically involved in learning and memory. Glucose transporter-5, fructose and uric acid levels, oxidative status, and inflammatory and synaptic markers were investigated by Western blotting and spectrophotometric or enzyme-linked immunosorbent assays. A short-term fructose-rich diet induced mitochondrial dysfunction and oxidative stress, associated with an increased concentration of inflammatory markers and decreased Neurofilament-M and post-synaptic density protein 95. These alterations, except for increases in haptoglobin and nitrotyrosine, were recovered by returning to a control diet. Overall, our results point to the dangerous effects of excessive consumption of fructose in young age but also highlight the effect of partial recovery by switching back to a control diet.

High Fructose Diet Induces Sex-specific Modifications in Synaptic Respiration and Affective-like Behaviors in Rats

The consequences of excessive fructose intake extend beyond those of metabolic disorder to changes in emotional regulation and cognitive function. Long-term consumption of fructose, particularly common when begun in adolescence, is more likely to lead to deleterious consequences than acute consumption. These long-term consequences manifest differently in males and females, suggesting a sex-divergent mechanism by which fructose can impair physiology and neural function. The purpose of the current project was to investigate a possible sex-specific mechanism by which elevated fructose consumption drives behavioral deficits and accompanying metabolic symptoms - specifically, synaptic mitochondrial function. Male and female rats were fed a high fructose diet beginning at weaning and maintained into adulthood. Measures of physiological health across the diet consumption period indicated that females were more likely to gain weight than males while both displayed increased circulating blood glucose. As adults, females fed the high fructose diet displayed increased floating behavior in the forced swim task while males exhibited increased exploratory behavior in the open field. Synaptic respiration was altered by diet in both females and males but the effect was sex-divergent - fructose-fed females had increased synaptic respiration while males showed a decrease. When exposed to an acute energetic challenge, the pattern was reversed. Taken together, these data indicate that diet-induced alterations to neural function and physiology are sex-specific and highlight the need to consider sex as a biological variable when treating metabolic disease. Furthermore, these data suggest that synaptic mitochondrial function may contribute directly to the behavioral consequences of elevated fructose consumption.

Facilitating fructose-driven metabolism exerts a protective effect on anoxic stress in Drosophila

Hypoxic stress is linked to various cardiovascular disorders (e.g., stroke, myocardial infarction), mediated, at least in part, by a reduction in ATP synthesis. Fructose-driven glycolysis is proposed as an alternative pathway capable of sustaining ATP production even under anoxic conditions. Here, we tested the hypothesis that facilitating fructose-driven metabolism exerts a protective effect against anoxic stress in Drosophila. Genetically modified flies with the human fructose transporter (GluT5) and ketohexokinase (KHK) genes downstream of upstream activating sequence (UAS) were constructed. The GAL4-UAS system was confirmed to: (i) increase the expression of GluT5 and KHK in a tissue-specific and a time-dependent manner (i.e., whole flies [with Act5c-gene switch GAL4 driver], neurons [with elav-gene switch GAL4 driver]) and (ii) reduce mortality of flies when placed under anoxic stress. Taken together, these data suggest that increasing fructose metabolism may be a clinically relevant approach to minimize hypoxia-induced cellular damage.

Dietary fructose as a model to explore the influence of peripheral metabolism on brain function and plasticity

High consumption of fructose has paralleled an explosion in metabolic disorders including obesity and type 2 diabetes. Even more problematic, sustained consumption of fructose is perceived as a threat for brain function and development of neurological disorders. The action of fructose on peripheral organs is an excellent model to understand how systemic physiology impacts the brain. Given the recognized action of fructose on liver metabolism, here we discuss mechanisms by which fructose can impact the brain by interacting with liver and other organs. The interaction between peripheral and central mechanisms is a suitable target to reduce the pathophysiological consequences of neurological disorders.

Sweet but Bitter: Focus on Fructose Impact on Brain Function in Rodent Models

Fructose consumption has drastically increased during the last decades due to the extensive commercial use of high-fructose corn syrup as a sweetener for beverages, snacks and baked goods. Fructose overconsumption is known to induce obesity, dyslipidemia, insulin resistance and inflammation, and its metabolism is considered partially responsible for its role in several metabolic diseases. Indeed, the primary metabolites and by-products of gut and hepatic fructolysis may impair the functions of extrahepatic tissues and organs. However, fructose itself causes an adenosine triphosphate (ATP) depletion that triggers inflammation and oxidative stress. Many studies have dealt with the effects of this sugar on various organs, while the impact of fructose on brain function is, to date, less explored, despite the relevance of this issue. Notably, fructose transporters and fructose metabolizing enzymes are present in brain cells. In addition, it has emerged that fructose consumption, even in the short term, can adversely influence brain health by promoting neuroinflammation, brain mitochondrial dysfunction and oxidative stress, as well as insulin resistance. Fructose influence on synaptic plasticity and cognition, with a major impact on critical regions for learning and memory, was also reported. In this review, we discuss emerging data about fructose effects on brain health in rodent models, with special reference to the regulation of food intake, inflammation, mitochondrial function and oxidative stress, insulin signaling and cognitive function.

Maternal high fructose-induced hippocampal neuroinflammation in the adult female offspring via PPARγ-NF-κB signaling

The mechanisms beneath the initiation of neuroinflammation are still inconclusive. Growing evidence proposes the maternal effect on the development of neuroinflammation. In this study, we evaluated the upstream regulators and the indices of neuroinflammation in the hippocampi of female offspring at 3 months old. The accumulation of nuclear factor-κB (NF-κB, 65 kDa), a cytokine-encoding transcription factor, was increased in microglia. The enhanced microglial activation was detected in CA1, CA3 and dentate gyrus (DG) HFD group with upregulation of CD11b and ionized calcium binding adaptor molecule 1 (Iba-1). Moreover, proinflammatory cytokines (including TNFα, IL-1β and IL-6) were significantly increased in HFD group. Peroxisome proliferator-activated receptors γ (PPARγ) is a transcription factor involved in the suppression of NF-κB expression and in encoding endogenous antioxidants (such as catalase and glutathione peroxidases). On the contrary, the expression of nuclear PPARγ was suppressed in hippocampal neurons of the HFD group. In addition, the expressions of glutathione peroxidase 1 (GPx1) was suppressed in HFD group. Oral application with pioglitazone, a PPARγ agonist, effectively ceased the neuroinflammation and reversed the expression of antioxidants in HFD group. Together, these results for the first time demonstrated that maternal HFD triggered the waxing and waning of NF-κB and PPARγ may initiate neuroinflammation in the hippocampus of adult female offspring. Our findings further suggest that PPARγ could be the feasible targets to reprogram the hippocampal impairment induced by maternal HFD.

CX3CR1-microglia mediates neuroinflammation and blood pressure regulation in the nucleus tractus solitarii of fructose-induced hypertensive rats

BACKGROUND

Inflammation is a common pathophysiological trait found in both hypertension and cardiac vascular disease. Recent evidence indicates that fractalkine (FKN) and its receptor CX3CR1 have been linked to inflammatory response in the brain of hypertensive animal models. Here, we investigated the role of CX3CR1-microglia in nitric oxide (NO) generation during chronic inflammation and systemic blood pressure recovery in the nucleus tractus solitarii (NTS).

METHODS

The hypertensive rat model was used to study the role of CX3CR1-microglia in NTS inflammation following hypertension induction by oral administration of 10% fructose water. The systolic blood pressure was measured by tail-cuff method of non-invasive blood pressure. The CX3CR1 inhibitor AZD8797 was administered intracerebroventricularly (ICV) in the fructose-induced hypertensive rat. Using immunoblotting, we studied the nitric oxide synthase signaling pathway, NO concentration, and the levels of FKN and CX3CR1, and pro-inflammatory cytokines were analyzed by immunohistochemistry staining.

RESULTS

The level of pro-inflammatory cytokines IL-1β, IL-6, TNF-α, FKN, and CX3CR1 were elevated two weeks after fructose feeding. AZD8797 inhibited CX3CR1-microglia, which improved the regulation of systemic blood pressure and NO generation in the NTS. We also found that IL-1β, IL-6, and TNF-α levels were recovered by AZD8797 addition.

CONCLUSION

We conclude that CX3CR1-microglia represses the nNOS signaling pathway and promotes chronic inflammation in fructose-induced hypertension. Collectively, our results reveal the role of chemokines such as IL-1β, IL-6, and TNF-α in NTS neuroinflammation with the involvement of FKN and CX3CR1.

Adipose Tissue and Brain Metabolic Responses to Western Diet-Is There a Similarity between the Two?

Dietary fats and sugars were identified as risk factors for overweight and neurodegeneration, especially in middle-age, an earlier stage of the aging process. Therefore, our aim was to study the metabolic response of both white adipose tissue and brain in middle aged rats fed a typical Western diet (high in saturated fats and fructose, HFF) and verify whether a similarity exists between the two tissues. Specific cyto/adipokines (tumor necrosis factor alpha (TNF-α), adiponectin), critical obesity-inflammatory markers (haptoglobin, lipocalin), and insulin signaling or survival protein network (insulin receptor substrate 1 (IRS), Akt, Erk) were quantified in epididymal white adipose tissue (e-WAT), hippocampus, and frontal cortex. We found a significant increase of TNF-α in both e-WAT and hippocampus of HFF rats, while the expression of haptoglobin and lipocalin was differently affected in the various tissues. Interestingly, adiponectin amount was found significantly reduced in e-WAT, hippocampus, and frontal cortex of HFF rats. Insulin signaling was impaired by HFF diet in e-WAT but not in brain. The above changes were associated with the decrease in brain derived neurotrophic factor (BDNF) and synaptotagmin I and the increase in post-synaptic protein PSD-95 in HFF rats. Overall, our investigation supports for the first time similarities in the response of adipose tissue and brain to Western diet.

Early Hepatic Oxidative Stress and Mitochondrial Changes Following Western Diet in Middle Aged Rats

To assess the effect of 4 weeks of high fat-high fructose feeding on whole body composition, energy balance, specific markers of oxidative stress and inflammation, and insulin sensitivity in the liver of middle-aged rats, rats (1 year) were fed a diet rich in saturated fatty acids and fructose (HFF rats), mimicking the “Western diet”, and compared with rats of the same age that were fed a low fat diet (LF rats). HFF rats exhibited a significant increase in the gain of body weight, energy, and lipids compared to LF rats. HFF rats also showed hepatic insulin resistance, together with an increase in plasma triglycerides, cholesterol, and tumor necrosis factor alpha. Hepatic lipids, triglycerides and cholesterol were higher in HFF rats, while a significant decrease in Stearoyl-CoA desaturase activity was found in this tissue. A marked increase in the protein amount of complex I, concomitant to a decrease in its contribution to mitochondrial respiration, was found in HFF rats. Lipid peroxidation and Nitro-Tyrosine content, taken as markers of oxidative stress, as well as NADPH oxidase activity, were significantly higher in HFF rats, while the antioxidant enzyme catalase decreased in these rats. Myeloperoxidase activity and lipocalin content increased, while peroxisome proliferator activated receptor gamma decreased in HFF rats. The present results provide evidence that middle-aged rats show susceptibility to a short-term “Western diet”, exhibiting altered redox homeostasis, insulin resistance, and early mitochondrial alterations in the liver. Therefore, this type of dietary habits should be drastically limited to pursue a “healthy aging”.

KRIT1 Deficiency Promotes Aortic Endothelial Dysfunction

Loss-of-function mutations of the gene encoding Krev interaction trapped protein 1 (KRIT1) are associated with the pathogenesis of Cerebral Cavernous Malformation (CCM), a major cerebrovascular disease characterized by abnormally enlarged and leaky capillaries and affecting 0.5% of the human population. However, growing evidence demonstrates that KRIT1 is implicated in the modulation of major redox-sensitive signaling pathways and mechanisms involved in adaptive responses to oxidative stress and inflammation, suggesting that its loss-of-function mutations may have pathological effects not limited to CCM disease. The aim of this study was to address whether KRIT1 loss-of-function predisposes to the development of pathological conditions associated with enhanced endothelial cell susceptibility to oxidative stress and inflammation, such as arterial endothelial dysfunction (ED) and atherosclerosis. Silencing of KRIT1 in human aortic endothelial cells (HAECs), coronary artery endothelial cells (HCAECs), and umbilical vein endothelial cells (HUVECs) resulted in increased expression of endothelial proinflammatory adhesion molecules vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) and in enhanced susceptibility to tumor necrosis factor alpha (TNF-α)-induced apoptosis. These effects were associated with a downregulation of Notch1 activation that could be rescued by antioxidant treatment, suggesting that they are consequent to altered intracellular redox homeostasis induced by KRIT1 loss-of-function. Furthermore, analysis of the aorta of heterozygous KRIT1^+/- mice fed a high-fructose diet to induce systemic oxidative stress and inflammation demonstrated a 1.6-fold increased expression of VCAM-1 and an approximately 2-fold enhanced fat accumulation (7.5% vs 3.6%) in atherosclerosis-prone regions, including the aortic arch and aortic root, as compared to corresponding wild-type littermates. In conclusion, we found that KRIT1 deficiency promotes ED, suggesting that, besides CCM, KRIT1 may be implicated in genetic susceptibility to the development of atherosclerotic lesions.

Mitochondria as Potential Targets in Alzheimer Disease Therapy: An Update

Alzheimer disease (AD) is a progressive and deleterious neurodegenerative disorder that affects mostly the elderly population. At the moment, no effective treatments are available in the market, making the whole situation a compelling challenge for societies worldwide. Recently, novel mechanisms have been proposed to explain the etiology of this disease leading to the new concept that AD is a multifactor pathology. Among others, the function of mitochondria has been considered as one of the intracellular processes severely compromised in AD since the early stages and likely represents a common feature of many neurodegenerative diseases. Many mitochondrial parameters decline already during the aging, reaching an extensive functional failure concomitant with the onset of neurodegenerative conditions, although the exact timeline of these events is still unclear. Thereby, it is not surprising that mitochondria have been already considered as therapeutic targets in neurodegenerative diseases including AD. Together with an overview of the role of mitochondrial dysfunction, this review examines the pros and cons of the tested therapeutic approaches targeting mitochondria in the context of AD. Since mitochondrial therapies in AD have shown different degrees of progress, it is imperative to perform a detailed analysis of the significance of mitochondrial deterioration in AD and of a pharmacological treatment at this level. This step would be very important for the field, as an effective drug treatment in AD is still missing and new therapeutic concepts are urgently needed.

Effect of Initial Aging and High-Fat/High-Fructose Diet on Mitochondrial Bioenergetics and Oxidative Status in Rat Brain

Middle age is an early stage of the aging process, during which the consumption of diets rich in saturated fats and/or simple sugars might influence brain function, but only few data are available on this issue. We therefore investigated the impact of a diet rich in saturated fat and fructose (HFF) on mitochondrial physiology in hippocampus and frontal cortex of middle-aged rats (1 year old), by including a group of adult rats (90 days) as a "negative control," lacking the putative effect of aging. Middle-aged rats were fed HFF or control diet for 4 weeks. Mitochondrial function was analyzed by high-resolution respirometry and by assessing the amount of respiratory complexes. Markers of oxidative balance, as well as the protein content of uncoupling protein 2 (UCP2), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and peroxisome proliferator-activated receptor alpha (PPARα), were also assessed. A decrease in the activity of complex I was detected in both brain areas of middle-aged rats. In hippocampus, mitochondrial respiratory capacity and complex IV content decreased with age and increased with HFF diet. Higher protein oxidative damage, decreased antioxidant defenses, and increased UCP2 and PGC-1α content were found in hippocampus of middle-aged rats. HFF feeding induced a significant reduction in the amount of UCP2, PGC-1α, and PPARα, together with higher protein oxidative damage, in both brain areas. Overall, our results point to middle age as a condition of early brain aging for mitochondrial function, with hippocampus being an area more susceptible to metabolic impairment than frontal cortex.

24S-hydroxycholesterol affects redox homeostasis in human glial U-87 MG cells

The cholesterol metabolite 24(S)-hydroxycholesterol (24S-OHC) allows cholesterol excretion from the brain and was suggested to be critically involved in physiological as well as neurodegenerative processes. It induces on human neuronal cell cultures a dose dependent toxicity associated with increased reactive oxygen species production. Since glial cells play a key role in assisting neuronal function, here we investigated the effects of increased concentrations of 24S-OHC on a glial cell model (human glioblastoma U-87 MG cells). We determined the content of PGC-1α and TFAM, involved in the biogenesis of mitochondria, both mitochondrial complexes activity and protein amount, lipid and protein oxidative damage, cellular reactive oxygen species (ROS) release and both the activities and amount of the antioxidant enzymes glutathione peroxidase and catalase. Low concentration of 24S-OHC increased cellular content of PGC-1α and TFAM and the activities of mitochondrial complexes I and II, with no marked changes in their protein amount. Interestingly, 24S-OHC at lower concentrations reduced while at higher concentration increased lipid and protein oxidative damage. Conversely, the content of nitro-tyrosine increased only with the highest 24S-OHC concentration. Also, cell H₂O₂ release was reduced by lower and increased by higher 24S-OHC used concentrations. The cell activity of glutathione peroxidase was reduced by 24S-OHC at higher concentration while that of catalase was reduced by all the assayed concentrations. Further, a dose dependent decrease of both enzymes levels was observed. In conclusion, we demonstrated that 24S-OHC exerts different effects on U-87 MG cells depending on its level. At lower concentrations it stimulates cellular processes critical to maintain redox homeostasis, while at higher dose its effect on the glial cell here used resemble its action on neurons.

Reversion of down-regulation of intestinal multidrug resistance-associated protein 2 in fructose-fed rats by geraniol and vitamin C: Potential role of inflammatory response and oxidative stress

Intestinal multidrug resistance-associated protein 2 is an ABC transporter that limits the absorption of xenobiotics ingested orally, thus acting as essential component of the intestinal biochemical barrier. Metabolic Syndrome (MetS) is a pathological condition characterized by dyslipidemia, hyperinsulinemia, insulin resistance, chronic inflammation, and oxidative stress (OS). In a previous study we demonstrated that MetS-like conditions induced by fructose in drinking water (10% v/v, during 21 days), significantly reduced the expression and activity of intestinal Mrp2 in rats. We here evaluated the potential beneficial effect of geraniol or vitamin C supplementation, natural compounds with anti-inflammatory and anti-oxidant properties, in reverse fructose-induced Mrp2 alterations. After MetS-like conditions were induced (21 days), animals were cotreated with geraniol or vitamin C or vehicle for another 14 days. Decreased expression of Mrp2 protein and mRNA due to fructose administration was reversed by geraniol and by vitamin C, consistent with restoration of Mrp2 activity evaluated in everted intestinal sacs. Concomitantly, increased intestinal IL-1β and IL-6 levels induced by fructose were totally and partially counterbalanced, respectively, by geraniol administration. The intestinal redox unbalance generated by fructose was improved by geraniol and vitamin C, as evidenced by decreasing lipid peroxidation products and activity of Superoxide Dismutase and by normalizing glutathione reduced/oxidized glutathione ratio. The restoration effects exhibited by geraniol and vitamin C suggest that local inflammatory response and OS generated under MetS-like conditions represent important mediators of the intestinal Mrp2 down-regulation. Additionally, both agents could be considered of potential therapeutic value to preserve Mrp2 function under MetS conditions.

Short-Term Neonatal Oral Administration of Oleanolic Acid Protects against Fructose-Induced Oxidative Stress in the Skeletal Muscles of Suckling Rats

Nutritional manipulations in the neonatal period are associated with the development of negative or positive health outcomes later in life. Excessive fructose consumption has been attributed to the increase in the global prevalence of metabolic syndrome (MetS) and the development of oxidative stress. Oleanolic acid (OA) has anti-diabetic and anti-obesity effects. We investigated the protective potential of orally administering OA in the neonatal period, to prevent fructose-induced oxidative stress, adverse health outcomes and maturation of the gastrointestinal tract (GIT) in suckling rats. Seven-day old Sprague-Dawley rats (N = 30) were gavaged daily with 10 mL/kg of: distilled water (DW), oleanolic acid (OA; 60 mg/kg), high fructose solution (HF; 20% w/v), or OAHF for 7 days. On day 14, tissue samples were collected to determine clinical health profiles, hepatic lipid content, and activity of anti-oxidant enzymes. Furthermore, biomarkers of oxidative stress and anti-oxidant capacity in the skeletal muscles were assessed. The gastrointestinal tract (GIT) morphometry was measured. Rats in all groups grew over the 7-day treatment period. There were no significant differences in the terminal body masses, GIT morphometry, surrogate markers of general health, liver lipid content across all treatment groups (p < 0.05). Neonatal fructose administration decreased the activity of catalase, depleted GSH and increased lipid peroxidation. However, the level of GSH and catalase activity were improved by neonatal OA treatment. Short-term oral OA administration during the critical developmental period protects against fructose-induced oxidative stress without adverse effects on health outcomes associated with MetS or precocious development of the GIT in suckling male and female rats.

Chronic Consumption of Fructose Induces Behavioral Alterations by Increasing Orexin and Dopamine Levels in the Rat Brain

It has been widely described that chronic intake of fructose causes metabolic alterations which can be associated with brain function impairment. In this study, we evaluated the effects of fructose intake on the sleep–wake cycle, locomotion, and neurochemical parameters in Wistar rats. The experimental group was fed with 10% fructose in drinking water for five weeks. After treatment, metabolic indicators were quantified in blood. Electroencephalographic recordings were used to evaluate the sleep architecture and the spectral power of frequency bands. Likewise, the locomotor activity and the concentrations of orexin A and monoamines were estimated. Our results show that fructose diet significantly increased the blood levels of glucose, cholesterol, and triglycerides. Fructose modified the sleep–wake cycle of rats, increasing the waking duration and conversely decreasing the non-rapid eye movement sleep. Furthermore, these effects were accompanied by increases of the spectral power at different frequency bands. Chronic consumption of fructose caused a slight increase in the locomotor activity as well as an increase of orexin A and dopamine levels in the hypothalamus and brainstem. Specifically, immunoreactivity for orexin A was increased in the ventral tegmental area after the intake of fructose. Our study suggests that fructose induces metabolic changes and stimulates the activity of orexinergic and dopaminergic neurons, which may be responsible for alterations of the sleep–wake cycle.

High-fructose diet during adolescent development increases neuroinflammation and depressive-like behavior without exacerbating outcomes after stroke

Diseases, disorders, and insults of aging are frequently studied in otherwise healthy animal models despite rampant co-morbidities and exposures among the human population. Stressor exposures can increase neuroinflammation and augment the inflammatory response following a challenge. The impact of dietary exposure on baseline neural function and behavior has gained attention; in particular, a diet high in fructose can increase activation of the hypothalamic-pituitary-adrenal axis and alter behavior. The current study considers the implications of a diet high in fructose for neuroinflammation and outcomes following the cerebrovascular challenge of stroke. Ischemic injury may come as a "second hit" to pre-existing metabolic pathology, exacerbating inflammatory and behavioral sequelae. This study assesses the neuroinflammatory consequences of a peri-adolescent high-fructose diet model and assesses the impact of diet-induced metabolic dysfunction on behavioral and neuropathological outcomes after middle cerebral artery occlusion. We demonstrate that consumption of a high-fructose diet initiated during adolescent development increases brain complement expression, elevates plasma TNFα and serum corticosterone, and promotes depressive-like behavior. Despite these adverse effects of diet exposure, peri-adolescent fructose consumption did not exacerbate neurological behaviors or lesion volume after middle cerebral artery occlusion.