Effects of high-fat diet on insulin receptor function in rat hippocampus and the level of neuronal corticosterone

Chronic High-Fat Diet Consumption Followed by Lipopolysaccharide Challenge Induces Persistent and Long-Lasting Microglial Priming, Mediates Synaptic Elimination via Complement C1q, and Leads to Behavioral Abnormalities in Male Wistar Rats

AIM

Microglia exhibit innate immune memory, altering their responses to subsequent challenges. Consumption of high-fat diet (HFD) triggers innate immune responses, but the characteristics of HFD-induced microglial priming remain unclear. We aim to investigate how HFD-induced microglial priming, followed by a lipopolysaccharide (LPS) challenge, affects brain functions.

METHODS

Male Wistar rats were divided into control, unprimed, and primed groups. The primed groups received either a single LPS injection (0.5 mg/kg, intraperitoneally) or HFD consumption for 4-8 weeks. Following the priming phase, all rats (except controls) were subjected to an LPS challenge with a 4- or 8-week interval. After 24 h of LPS challenge, cognition, anxiety-, and depressive-like behaviors were assessed. The brain and hippocampus were collected for further analysis.

RESULTS

Both LPS- and 4-week HFD-primed groups, followed by LPS challenge, exhibited increased peripheral and brain oxidative stress, impaired neurogenesis, disrupted neurotransmitter balance, and altered glycolysis and Krebs cycle substrates. These changes also caused microglial morphological alterations, elevated C1q levels, and synaptic loss, which were associated with anxiety- and depressive-like behaviors, indicating that 4-week HFD consumption has a similar immune priming ability to a single dose of LPS injection. Extending HFD priming to 8 weeks exacerbated microglial and brain inflammation, synaptic loss, and behavioral deficits. Furthermore, prolonging the interval between priming and LPS challenge worsened inflammation and cognitive decline, suggesting the persistent effects of microglial priming.

CONCLUSIONS

HFD consumption persistently and time-dependently primes microglia similar to a single LPS injection, influencing immune responses and contributing to behavioral abnormalities.

Early adversity and the comorbidity between metabolic disease and psychopathology

Although the co-existence of metabolic and psychiatric disorders in the same individual (comorbidity) is very prevalent, the mechanisms by which these disorders co-occur are poorly understood, but a history of early-life adversity is a common developmental risk factor. Exposure to adverse environments during critical periods of development (e.g. fetal life and infancy) modifies the metabolism and the function of the brain persistently, influencing behaviours that contribute to both metabolic and mental health disarrangements over the life course. We will review molecular and clinical evidence supporting the notion that early adversity is an important risk factor for the comorbidity between metabolic and psychiatric conditions. We will also discuss the possible mechanisms involved: neurometabolic programming, epigenetic alterations and the cumulative effects of altered inflammatory and oxidative pathways linked to early adversity.

Effects of Perilla Seed Oil on Blood Lipids, Oxidative Stress, and Inflammation in Hyperlipidemic Rats

A high-fat diet is a key factor contributing to hyperlipidemia. Perilla seed oil, a plant-based source of omega-3, has the potential to reduce this risk. However, its effects have not been fully established. This study aimed to evaluate the effects of perilla seed oil on blood lipid levels, oxidative stress, and inflammation in rats induced with hyperlipidemia through a high-fat diet. Male Wistar rats were administered perilla seed oil at a dosage of 0.67 g/kg body weight per day for 8 weeks. The results showed that perilla seed oil significantly reduced triglyceride levels by 38.00% and 41.88% and total cholesterol levels by 17.16% and 15.91% in the high-fat diet and normal diet groups, respectively (p < 0.05). However, perilla seed oil had no significant effect on HDL and LDL levels. Additionally, perilla seed oil supplementation significantly reduced malondialdehyde (MDA) levels, a biomarker of oxidative stress, by 68.18% in the high-fat diet group and 29.72% in the normal diet group. Regarding its anti-inflammatory effects, perilla seed oil reduced interleukin-6 (IL-6) levels by 15.21% and 64.27% in the high-fat diet and normal diet groups, respectively (p < 0.05). These findings suggest that perilla seed oil has the potential to reduce the risk of metabolic syndrome.

The impact of lactate on diabetic cognitive dysfunction: Insights from energy metabolism to epigenetic modulation

This manuscript elucidates the intricate roles of lactate in Diabetic Cognitive Dysfunction (DCD), extending beyond its conventional role as an energy substrate. The investigation centers on the participation of lactate in energy metabolism and epigenetic modulation, with a particular emphasis on its influence on cognitive faculties through histone lactylation. The discourse scrutinizes lactate's part in the metabolic equilibrium of the central nervous system, encompassing its fluctuating concentrations under various conditions and its pivotal function within the Astrocyte-Neuron Lactate Shuttle (ANLS) mechanism as an energy conduit. The involvement of lactate in DCD is multilayered, encompassing metabolic pathways, cellular signaling cascades, and the regulation of gene expression. Dysregulation in lactate metabolism and the histone lactylation process may modulate neuronal functionality by impacting genes integral to neuroplasticity and cognitive capabilities. These revelations offer novel insights into the molecular underpinnings of DCD and lay the groundwork for the discovery of potential therapeutic targets. Subsequent scholarly endeavors are poised to dissect the nuanced mechanisms by which lactate and its lactylation exert influence in DCD, pinpointing the critical genes modulated by lactylation and assessing their ramifications on neuronal function and signal transduction pathways. Given the intricate regulatory dynamics of lactate, contingent upon concentration, temporal factors, and disease etiology, a more profound elucidation of lactate's role in DCD necessitates an augmented cadre of animal experimentation and clinical observational research. Such investigative pursuits are anticipated to yield innovative approaches and methodologies for the comprehensive management of DCD, spanning prevention, diagnosis, and therapeutic intervention.

Cyclosorus terminans extract mitigates submandibular gland changes associated with high-fat diet consumption in male rats

OBJECTIVES

To investigate whether the prophylactic effect of Cyclosorus terminans extract mitigates metabolic impairment and submandibular gland changes, as indicated by increased aquaporin5 expression, decreased fibrosis, oxidative stress and inflammation, improved mitochondrial homeostasis/dynamics, and decreased cell death in the submandibular glands of high-fat diet (HFD)-feeding rats.

METHODS

Thirty-two male Wistar rats were assigned to either a normal diet (ND) as control rats (n=8) or a HFD (n=24) for 12 weeks. The HFD-treated rats were divided into 3 subgroups to receive either: 1) vehicle (HDV), 2) Cyclosorus terminans at a dose of 100 mg/kg/d (HF100), or 3) Cyclosorus terminans at a dose of 200 mg/kg/d (HF200). At week 13, metabolic parameters, systemic oxidative stress, and submandibular gland parameters were assessed.

RESULTS

Twelve weeks of HFD-feeding rats induced obese-insulin resistance and submandibular gland changes. Both HF100- and HF200-treated groups improved metabolic parameters and prevented gland changes by reducing fibrosis (TGF-β and p-38), malondialdehyde levels, inflammation (TNF-α, NF-κB, and Ifng), and cell death markers (Caspase 3, GSDMD, and MLKL). Both treatments supported balanced mitochondrial homeostasis/dynamics, as indicated by regulating related genes (Cpt1b, Ndufb8, Mfn1, Mfn2, Opa1, and Dnm1l). However, only the HF200-treated rats restored aquaporin-5 and antioxidants (SOD2 and GPX4) expression to control levels.

CONCLUSIONS

Cyclosorus terminans mitigates metabolic disturbances and submandibular gland changes in HFD-feeding rats. The high dose was more effective, improving gland function by increasing aquaporin5 and antioxidants. These results suggest Cyclosorus terminans may be a promising therapeutic for metabolic disturbances and submandibular gland changes in obese-insulin resistant patients.

IGF1 enhances memory function in obese mice and stabilizes the neural structure under insulin resistance via AKT-GSK3β-BDNF signaling

Obesity is a prevalent metabolic disorder linked to insulin resistance, hyperglycemia, increased adiposity, chronic inflammation, and cognitive dysfunction. Recent research has focused on developing therapeutic strategies to mitigate cognitive impairment associated with obesity. Insulin growth factor-1 (IGF1) deficiency is linked to insulin resistance, glucose intolerance, and the progression of obesity-related central nervous system (CNS) disorders. In this study, we investigated the neuroprotective effects of IGF1 in two obesity models: diet-induced obesity (high-fat diet mice) and genetic obesity (ob/ob mice which is genetically deficient in leptin), and in vitro Neuro2A neuronal cells and primary cortical neurons under insulin resistance conditions. We performed RNA sequencing analysis using the cortex of high-fat diet mice injected with IGF1. Also, we detected cytokine levels in blood of high-fat diet mice injected with IGF1. In addition, we conducted the Barnes maze test as a spatial memory function test and open field test as an anxiety behavior test in ob/ob mice. We measured the levels of proteins and mRNAs related to insulin signaling, including synaptic density proteins in brain cortex of ob/ob mice. Our results showed that IGF1 injection enhanced spatial memory function and synaptic plasticity in obese mice. Furthermore, in vitro data demonstrated that IGF1 treated neurons revealed enhanced neural complexity and improved neurite outgrowth under insulin resistance condition through the AKT-GSK3β-BDNF pathway related to antidepressant, cognitive function and anti-apoptotic mechanisms. Therefore, our results provided that IGF1 have potential to alleviate cognitive impairment by promoting synaptic plasticity and neural complexity in the obese brain.

Aerobic exercise and metformin attenuate the cognitive impairment in an experimental model of type 2 diabetes mellitus: focus on neuroinflammation and adult hippocampal neurogenesis

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder that increases the prevalence of cognitive impairment in the geriatric population. Aerobic exercise is an excellent non-pharmacological therapeutic strategy to prevent Alzheimer's disease, the most common form of dementia. The exact molecular mechanism of aerobic exercise (Exe) as an intervention to counter cognitive decline is far from clear. Metformin is a first-line agent against T2DM with neuroprotective properties. The present study assessed the role of treadmill exercise in combination with a low dose of metformin (Met; 70 mg/kg) in cognitive impairment and its associated molecular mechanism in T2DM rats. The experimental model of T2DM-associated cognitive decline was created by administration of a high-fat diet (HFD) with a low dose of streptozotocin (STZ; 35 mg/kg). Neurobehavioral assessments were performed to evaluate spatial recognition and fear-conditioned memory across the groups: control, HFD + STZ, HFD + STZ + Exe, and HFD + STZ + Exe + Met. In addition, we performed immunohistochemistry and western blotting on the rat hippocampal tissue from the above groups for protein expression studies. T2DM rats showed a significant cognitive decline compared to the control group, which improved in the long-term exercise and metformin co-administered animals. The level of neuroinflammation was significantly elevated in the hippocampal tissue of T2DM rats compared to the control and lowered after exercise and metformin treatment. T2DM reduced mature neurons and neurogenesis while increasing astrogliosis and microgliosis, ameliorated by exercise and metformin treatment. Moreover, T2DM impaired hippocampal neurogenesis by reducing the canonical Wnt/β-catenin pathway, which got upregulated in exercise and metformin-co-administered rats. Long-term aerobic exercise with metformin treatment ameliorated neuroinflammation and promoted adult hippocampal neurogenesis via upregulating the canonical Wnt/β-catenin pathway in T2DM rats.

Gestational diabetes mellitus, not obesity, triggers postpartum brain inflammation and premature aging in Sprague-Dawley rats

Previous studies showed that women with gestational diabetes mellitus (GDM) are susceptible to cognitive dysfunction. We investigated the effects of GDM on brain pathologies and premature brain aging in rats. Seven-week-old female Sprague-Dawley rats were fed a normal diet (ND) or a high-fat diet (HFD) after two weeks of acclimatization. On pregnancy day 0, HFD-treated rats received streptozotocin (GDM group) or vehicle (Obese mothers). ND-treated rats received vehicle (ND-control mothers). On postpartum day 21, brains and blood were collected. The GDM group showed increased inflammatory and premature aging markers, mitochondrial changes, and compensatory increases in the blood-brain barrier and synaptic proteins in the prefrontal cortex and hippocampus. GDM triggers maternal brain inflammation and premature aging, suggesting compensatory mechanisms may protect against these effects.

Inhibition of 5-alpha reductase attenuates cardiac oxidative damage in obese and aging male rats via the enhancement of antioxidants and the p53 protein suppression

In aging and metabolic syndrome oxidative stress is a causative factor in the cardiovascular pathology. Upregulation of 5-⍺ reductase is associated with cardiac hypertrophy but how inhibition of 5-⍺ reductase affects cardiometabolic function during oxidative damage under those conditions is unclear. Our hypothesis was that Finasteride (Fin), a 5-⍺ reductase inhibitor, promotes an antioxidant response, leading to an improvement in cardiac function in obese and aging rats. Male rats were divided into 3 groups including normal diet (ND) fed rats, ND-fed rats treated with d-galactose (D-gal) to induce aging, and high-fat diet (HFD) fed rats to induce obesity. Rats received their assigned diet or D-gal for 18 weeks. At week 13, rats in each group were divided into 2 subgroups and received either a vehicle or Fin (5 mg/kg/day, oral gavage). Cardiometabolic and molecular parameters were subsequently investigated. Both D-gal and HFD successfully induced cardiometabolic dysfunction, oxidative stress, mitochondrial dysfunction, and DNA fragmentation. Fin treatment did not affect metabolic disturbances; however, it reduced cardiac sympathovagal imbalance, cardiac dysfunction through the inhibition of oxidative stress and promoted antioxidants, resulting in reduced p53 protein levels and DNA fragmentation. Surprisingly, Fin induced insulin resistance in ND-fed rats. Fin effectively improved cardiac function in both models by enhancing antioxidant levels, suppressing oxidative stress and DNA fragmentation. However, Fin treatment did not confer any beneficial effects on metabolic status. Fin administration effectively improved cardiac sympathovagal balance and cardiac function in rats with oxidative damage induced by either D-gal or HFD.

Obesity-induced neuronal senescence: Unraveling the pathophysiological links

Obesity is one of the most prevalent and increasing metabolic disorders and is considered one of the twelve risk factors for dementia. Numerous studies have demonstrated that obesity induces pathophysiological changes leading to cognitive decline; however, the underlying molecular mechanisms are yet to be fully elucidated. Various biochemical processes, including chronic inflammation, oxidative stress, insulin resistance, dysregulation of lipid metabolism, disruption of the blood-brain barrier, and the release of adipokines have been reported to contribute to the accumulation of senescent neurons during obesity. These senescent cells dysregulate neuronal health and function by exhibiting a senescence-associated secretory phenotype, inducing neuronal inflammation, deregulating cellular homeostasis, causing mitochondrial dysfunction, and promoting microglial infiltration. These factors act as major risks for the occurrence of neurodegenerative diseases and cognitive decline. This review aims to focus on how obesity upregulates neuronal senescence and explores both pharmacological and non-pharmacological interventions for preventing cognitive impairments, thus offering new insights into potential therapeutic strategies.

Assessment of the anti-inflammatory and anti-glycemic properties of Royal Jelly and Tocotrienol-rich fraction in an experimental study: Does irisin mediate these effects?

Irisin, a novel adipomyokine, has been proposed to be a therapeutic agent against obesity-related metabolic disease. Royal Jelly (RJ) and tocotrienol-rich fraction (TRF) are suggested to promote obesity and its related problems through potential mutual mechanistic pathways. This investigation intended to evaluate the glycemic and inflammation-promoting effects of RJ, TRF, and their combinations to evaluate their synergic effects through irisin action in obese rats induced by a high-fat diet (HFD) that underwent a calorie restriction diet (CRD). Fifty HFD-fed obese rats received the following interventions: RJ, TRF, or RJ + TRF in combination with a CRD for eight consecutive weeks. After the investigation, body weight, fasting blood sugar (FBS), irisin, insulin, C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), leptin, adiponectin, and insulin resistance (IR) were assessed. After 8 weeks of treatment, significant weight reduction was noticed in rats that received RJ and RJ + TRF related to the CRD rats (p < .001), although this reduction was not considerable in TRF-treated rats. RJ and RJ + TRF supplementation markedly elevated irisin concentrations in CRD rats (p < .05), but TRF did not. Glycemic indices, inflammatory indices including IL-1β and CRP levels, and leptin concentrations were significantly decreased after RJ, TRF, and their combinations were added to CRD (p < .05). According to the mediational analysis results, irisin mediated the promoting effects of RJ on glycemic hemostasis. Based on the results of this investigation, RJ and TRF are novel nutrients that have the potential to improve obesity-related disorders. This research suggests that RJ exerts its beneficial glycemic regulatory effects through irisin.

Long-term Treatment with a 5-Alpha-Reductase Inhibitor Alleviates Depression-like Behavior in Obese Male Rats

Several studies have reported side effects of finasteride (FIN), such as anxiety/depression in young men. Obesity is also positively associated with anxiety/depression symptoms; however, the impacts of long-term FIN treatment and FIN withdrawal in young obese individuals are still elusive. The present study aimed to investigate the effect of long-term treatment and its withdrawal on anxiety/depression and brain pathologies in lean and obese adult male rats. Forty-eight male Wistar rats were equally divided into two groups and fed either a normal or high-fat diet. At age 13 weeks, rats in each dietary group were divided into three subgroups: 1) the control group receiving drinking water, 2) the long-term treatment group receiving FIN orally at 5 mg/kg/day for 6 weeks, and 3) the withdrawal group receiving FIN orally at 5 mg/kg/day for 2 weeks followed by a 4-week withdrawal period. Anxiety/depression-like behaviors, biochemical analysis, brain inflammation, oxidative stress, neuroactive steroids, brain metabolites, and microglial complexity were tested. The result showed that lean rats treated with long-term FIN and its withdrawal exhibited metabolic disturbances, depressive-like behavior, and both groups showed increased neurotoxic metabolites and reduced microglial complexity. Obesity itself led to metabolic disturbances and brain pathologies, including increased inflammation, oxidative stress, and quinolinic acid, as well as reduced microglial complexity, resulting in increased anxiety- and depression-like behaviors. Interestingly, the long-term FIN treatment group in obese rats showed attenuation of depressive-like behaviors, brain inflammation, and oxidative stress, along with increased brain antioxidants, suggesting the possible benefits of FIN in obese conditions.

Effects of a high-fat diet on cognition and brain distribution of intranasal insulin in E3 and E4 male and female mice

There are genetic and environmental risk factors that contribute to the development of cognitive decline in Alzheimer's disease (AD). Some of these include the genetic predisposition of the apolipoprotein E4 genotype, consuming a high-fat diet (HFD), and the female sex. Brain insulin receptor resistance and deficiency have also been shown to be associated with AD and cognitive impairment. Intranasal (INL) insulin enhances cognition in AD, but the response varies due to genotype, diet, and sex. We investigated here the combination of these risk factors in a humanized mouse model, expressing E3 or E4, following a HFD in males and females on cognitive performance and the brain distribution of insulin following INL delivery. The HFD had a negative effect on survival in male mice only, requiring sex to be collapsed. We found many genotype, diet, and genotype x diet effects in anxiety-related tasks. We further found beneficial effects of INL insulin in our memory tests, with the most important findings showing a beneficial effect of INL insulin in mice on a HFD. We found insulin distribution throughout the brain after INL delivery was largely unaffected by diet and genotype, indicating these susceptible groups can still receive adequate levels of insulin following INL delivery. Our findings support the involvement of brain insulin signaling in cognition and highlight continuing efforts investigating mechanisms resulting from treatment with INL insulin.

Resistance training boosts lactate transporters and synaptic proteins in insulin-resistance mice

Background

This investigation delineates the influence of resistance training on the expression of synaptic plasticity-related proteins in the hippocampi of insulin-resistant mice and explores the underlying molecular mechanisms.

Methods

Six-week-old male C57BL/6 J mice were stratified into a control group and a high-fat diet group to induce insulin resistance over a 12-week period. Subsequently, the mice were further divided into sedentary and resistance training cohorts, with the latter engaging in a 12-week ladder-climbing regimen. Post-intervention, blood, and hippocampal specimens were harvested for analytical evaluation.

Results

In the insulin-resistant mice, elevated blood lactate levels were observed alongside diminished expression of synaptic plasticity-related proteins, monocarboxylate transporters (MCTs), and reduced phosphorylation of protein kinase B (Akt) and mechanistic target of rapamycin (mTOR). In contrast, the expression of eukaryotic translation initiation factor 4 E-binding protein 2 was significantly augmented. Resistance training mitigated insulin resistance, decreased blood lactate levels, and enhanced the expression and phosphorylation of mTOR, regulatory-associated protein of mTOR, MCTs, and synaptic plasticity-related proteins.

Conclusions

Resistance training mitigates insulin resistance and improves hippocampal synaptic plasticity by normalizing blood lactate levels and enhancing mTOR, MCTs, and synaptic plasticity-related proteins. It may also activate mTORC1 via the PI3K/Akt pathway, promote lactate utilization, and enhance synaptic plasticity proteins, potentially alleviating peripheral insulin resistance. Further research is needed to confirm these mechanisms.

Metabolism changes caused by glucose in normal and cancer human brain cell lines by Raman imaging and chemometric methods

Glucose is the main source of energy for the human brain. This paper presents a non-invasive technique to study metabolic changes caused by glucose in human brain cell lines. In this paper we present the spectroscopic characterization of human normal brain (NHA; astrocytes) and human cancer brain (CRL-1718; astrocytoma and U-87 MG; glioblastoma) control cell lines and cell lines upon supplementation with glucose. Based on Raman techniques we have identified biomarkers that can monitor metabolic changes in lipid droplets, mitochondria and nucleus caused by glucose. We have studied the vibrations at 750 cm-1, 1444 cm-1, 1584 cm-1 and 1656 cm-1 as a function of malignancy grade. We have compared the concentration of cytochrome, lipids and proteins in the grade of cancer aggressiveness in normal and cancer human brain cell lines. Chemometric analysis has shown that control normal, control cancer brain cell lines and normal and cancer cell lines after supplementation with glucose can be distinguished based on their unique vibrational properties. PLSDA (Partial Least Squares Discriminant Analysis) and ANOVA tests have confirmed the main role of cytochromes, proteins and lipids in differentiation of control human brain cells and cells upon supplementation with glucose. We have shown that Raman techniques combined with chemometric analysis provide additional insight to monitor the biology of astrocytes, astrocytoma and glioblastoma after glucose supplementation.

Cyclosorus Terminans Extract Alleviates Neuroinflammation in Insulin Resistant Rats

High-fat diet consumption for an extended period causes obesity, systemic metabolic disturbance, and brain insulin resistance, resulting in neuroinflammation. Although the beneficial effect of Cyclosorus terminans extract on obesity-related insulin resistance has been demonstrated, little is known about how it affects neuroinflammation and brain insulin resistance in obese rats. Male Wistar rats were given either a normal diet (ND, n = 6) or a high-fat diet (HFD, n = 24) for a total of 14 weeks. At the beginning of the week, 13 rats in the ND group were given vehicle orally for 2 weeks, while rats on HFD diets were randomized to one of four groups and given either vehicle, 100 mg/kg/day of Cyclosorus terminans extract, 200 mg/kg/day of Cyclosorus terminans extract, or 20 mg/kg/day of pioglitazone orally for 2 weeks. After the experimental period, blood and brain samples were taken to assess metabolic and brain parameters. HFD-fed rats had obesity, systemic and brain insulin resistance, brain inflammation, microglial and astrocyte hyperactivity, and brain necroptosis. Treatment with 200 mg/kg/day of Cyclosorus terminans extract and pioglitazone equally attenuated obesity, insulin resistance, brain insulin dysfunction, and neuroinflammation in insulin resistant rats. Our findings suggest that Cyclosorus terminans extract may hold promise as a therapeutic agent for insulin resistance and neuroinflammation in obese conditions.

Excision of the endothelial blood-brain barrier insulin receptor does not alter spatial cognition in mice fed either a chow or high-fat diet

Insulin is transported across the blood-brain barrier (BBB) endothelium to regulate aspects of metabolism and cognition. Brain insulin resistance often results from high-fat diet (HFD) consumption and is thought to contribute to spatial cognition deficits. To target BBB insulin function, we used Cre-LoxP genetic excision of the insulin receptor (InsR) from endothelial cells in adult male mice. We hypothesized that this excision would impair spatial cognition, and that high-fat diet consumption would exacerbate these effects. Excision of the endothelial InsR did not impair performance in two spatial cognition tasks, the Y-Maze and Morris Water Maze, in tests held both before and after 14 weeks of access to high-fat (or chow control) diet. The HFD increased body weight gain and induced glucose intolerance but did not impair spatial cognition. Endothelial InsR excision tended to increase body weight and reduce sensitivity to peripheral insulin, but these metabolic effects were not associated with impairments to spatial cognition and did not interact with HFD exposure. Instead, all mice showed intact spatial cognitive performance regardless of whether they had been fed chow or a HFD, and whether the InsR had been excised or not. Overall, the results indicate that loss of the endothelial InsR does not impact spatial cognition, which is in line with pharmacological evidence that other mechanisms at the BBB facilitate insulin transport and allow it to exert its pro-cognitive effects.

Modulation of Sirtuin 3 by N-Acetylcysteine Preserves Mitochondrial Oxidative Phosphorylation and Restores Bisphenol A-Induced Kidney Damage in High-Fat-Diet-Fed Rats

Bisphenol A (BPA) and high-fat diets (HFD) are known to adversely affect the kidneys. However, the combined effects of both cases on kidney health and the potential benefits of N-acetylcysteine (NAC) in mitigating these effects have not been investigated. To explore these aspects, male Wistar rats were fed with HFD and allocated to receive a vehicle or BPA. At week twelve, the BPA-exposed rats were subdivided to receive a vehicle or NAC along with BPA until week sixteen. Rats fed HFD and exposed to BPA showed renal dysfunction and structural abnormalities, oxidative stress, inflammation, and mitochondrial dysfunction, with alterations in key proteins related to mitochondrial oxidative phosphorylation (OXPHOS), bioenergetics, oxidative balance, dynamics, apoptosis, and inflammation. Treatment with NAC for 4 weeks significantly improved these conditions. The findings suggest that NAC is beneficial in protecting renal deterioration brought on by prolonged exposure to BPA in combination with HFD, and modulation of sirtuin 3 (SIRT3) signaling by NAC appears to play a key role in the preservation of homeostasis and integrity within the mitochondria by enhancing OXPHOS activity, maintaining redox balance, and reducing inflammation. This study provides valuable insights into potential therapeutic strategies for preserving kidney health in the face of environmental and dietary challenges.

An acute bout of resistance exercise increases BDNF in hippocampus and restores the long-term memory of insulin-resistant rats

A sedentary lifestyle, inadequate diet, and obesity are substantial risk factors for Type 2 diabetes mellitus (T2DM) development. A major picture of T2DM is insulin resistance (IR), which causes many impairments in brain physiology, such as increased proinflammatory state and decreased brain-derived neurotrophic factor (BDNF) concentration, hence reducing cognitive function. Physical exercise is a non-pharmacological tool for managing T2DM/IR and its complications. Thus, this study investigated the effects of IR induction and the acute effects of resistance exercise (RE) on memory, neurotrophic, and inflammatory responses in the hippocampus and prefrontal cortex of insulin-resistant rats. IR was induced by a high-fat diet and fructose-rich beverage. Insulin-resistant rats performed acute resistance exercise (IR.RE; vertical ladder climb at 50-100% of the maximum load) or rest (IR.REST; 20 min). Cognitive parameters were assessed by novel object recognition (NOR) tasks, and biochemical analyses were performed to assess BDNF concentrations and inflammatory profile in the hippocampus and prefrontal cortex. Insulin-resistant rats had 20% worse long-term memory (LTM) (p < 0.01) and lower BDNF concentration in the hippocampus (-14.6%; p < 0.05) when compared to non-insulin-resistant rats (CON). An acute bout of RE restored LTM (-9.7% pre vs. post; p > 0.05) and increased BDNF concentration in the hippocampus (9.1%; p < 0.05) of insulin-resistant rats compared to REST. Thus, an acute bout of RE can attenuate the adverse effects of IR on memory and neurotrophic factors in rats, representing a therapeutic tool to alleviate the IR impact on the brain.

Affective and Cognitive Impairments in Rodent Models of Diabetes

Diabetes and related acute and long-term complications have a profound impact on cognitive, emotional, and social behavior, suggesting that the central nervous system (CNS) is a crucial substrate for diabetic complications. When anxiety, depression, and cognitive deficits occur in diabetic patients, the symptoms and complications related to the disease worsen, contributing to lower quality of life while increasing health care costs and mortality. Experimental models of diabetes in rodents are a fundamental and valuable tool for improving our understanding of the mechanisms underlying the close and reciprocal link between diabetes and CNS alterations, including the development of affective and cognitive disorders. Such models must reproduce the different components of this pathological condition in humans and, therefore, must be associated with affective and cognitive behavioral alterations. Beyond tight glycemic control, there are currently no specific therapies for neuropsychiatric comorbidities associated with diabetes; animal models are, therefore, essential for the development of adequate therapies. To our knowledge, there is currently no review article that summarizes changes in affective and cognitive behavior in the most common models of diabetes in rodents. Therefore, in this review, we have reported the main evidence on the alterations of affective and cognitive behavior in the different models of diabetes in rodents, the main mechanisms underlying these comorbidities, and the applicable therapeutic strategy.

Pancreatic GLUT2 protein expression and isolated islets insulin secretion decreased in high-fat fed rat dams

Purpose

Chronic consumption of high-fat foods during the reproductive period may endanger the dams' metabolic homeostasis and might adversely affect pregnancy outcome. In this regard the present study aimed to investigate the effect of long-term high-fat feeding on pancreatic glucose transporter-2 (GLUT2) protein expression and isolated islets glucose-stimulated insulin secretion in Wistar rat dams.

Materials and methods

Female rats were randomly divided into normal (N) and high-fat (HF; containing cow butter) diet groups and consumed their respective diets for 10 weeks (from prepregnancy to the end of lactation). After lactation, fasting plasma concentrations of glucose and insulin were measured to calculate HOMA-IR index, then intraperitoneal glucose tolerance test (IPGTT) was performed. Moreover, the pancreatic GLUT2 protein expression and insulin secretion from isolated islets at basal (5.6 mM) and stimulated (16.7 mM) glucose concentrations were assessed.

Results

In HF group compared to N group, the plasma insulin level increased, whereas the plasma glucose level did not change in fasting state. Accordingly, the HOMA-IR index increased in HF fed animals. Furthermore, the IPGTT revealed glucose intolerance based on the plasma glucose and insulin results. Also, the pancreatic GLUT2 expression and isolated islets insulin secretion, in response to high glucose concentration, were decreased.

Conclusion

The chronic consumption of high-fat foods during prepregnancy, pregnancy, and lactation periods can lead to glucose intolerance, insulin resistance, and inhibition of pancreatic GLUT2 expression, which impairs glucose homeostasis. Therefore, it is crucial to carefully monitor the diet composition of dams during this critical period.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01274-6.

Bariatric Surgery and Gut-Brain-Axis Driven Alterations in Cognition and Inflammation

Obesity is associated with systemic inflammation, comorbidities like diabetes, cardiovascular disease and several cancers, cognitive decline and structural and functional brain changes. To treat, or potentially prevent these related comorbidities, individuals with obesity must achieve long-term sustainable weight loss. Often life style interventions, such as dieting and increased physical activity are not successful in achieving long-term weight loss. Meanwhile bariatric surgery has emerged as a safe and effective procedure to treat obesity. Bariatric surgery causes changes in physiological processes, but it is still not fully understood which exact mechanisms are involved. The successful weight loss after bariatric surgery might depend on changes in various energy regulating hormones, such as ghrelin, glucagon-like peptide-1 and peptide YY. Moreover, changes in microbiota composition and white adipose tissue functionality might play a role. Here, we review the effect of obesity on neuroendocrine effects, microbiota composition and adipose tissue and how these may affect inflammation, brain structure and cognition. Finally, we will discuss how these obesity-related changes may improve after bariatric surgery.

Differential temporal therapies with pharmacologically targeted mitochondrial fission/fusion protect the brain against acute myocardial ischemia-reperfusion injury in prediabetic rats: The crosstalk between mitochondrial apoptosis and inflammation

An imbalance of brain mitochondrial dynamics, increases in brain inflammation and apoptosis, and increasing cognitive dysfunction, have been reported as being associated with prediabetes and myocardial ischemia-reperfusion (IR) injury. Since inhibiting mitochondrial fission with Mdivi-1 or promoting fusion with M1 had cardioprotective effects in myocardial IR injury and obesity, the neuroprotective roles of Mdivi-1 and M1 when administered at different time points of myocardial IR injury in obese prediabetes have never been determined. Ninety-six male Wistar rats were fed with either a normal (ND: n = 8) or a high-fat diet to induce prediabetes (HFD: n = 88) for 12 weeks. At week 13, all rats were subjected to left anterior descending coronary artery ligation for 30 min, followed by reperfusion for 120 min. HFD rats were randomly divided into 10 groups and assigned into either a pre-ischemic group treated with vehicle (HFV), pre-ischemic, during-ischemic, or onset of reperfusion groups treated with either Mdivi-1 (MDV), M1, or combined (COM). Heart function was examined invasively, with the heart being terminated to investigate myocardial infarction. Brains were collected to determine mitochondrial functions, inflammation, apoptosis, and pathological markers. Mdivi-1, M1, and COM treatment at different periods exerted cardioprotection against myocardial IR injury in HFD-fed rats by reducing infarct size and left ventricular dysfunction. All interventions also improved all brain pathologies against myocardial IR injury in prediabetic rats. These findings suggest that differential temporal modulation of mitochondrial dynamics may be appropriate regimens for preventing heart and brain complications after myocardial IR injury in obese prediabetes.

Diabetes and cognitive decline: Challenges and future direction

There is growing evidence that diabetes can induce cognitive decline and dementia. It is a slow, progressive cognitive decline that can occur in any age group, but is seen more frequently in older individuals. Symptoms related to cognitive decline are worsened by chronic metabolic syndrome. Animal models are frequently utilized to elucidate the mechanisms of cognitive decline in diabetes and to assess potential drugs for therapy and prevention. This review addresses the common factors and pathophysiology involved in diabetes-related cognitive decline and outlines the various animal models used to study this condition.

Endoplasmic reticulum stress inhibition ameliorated WFS1 expression alterations and reduced pancreatic islets' insulin secretion induced by high-fat diet in rats

Endoplasmic reticulum (ER) stress is involved in the development of glucose homeostasis impairment. When ER stress occurs, the unfolded protein response (UPR) is activated to cope with it. One of the UPR components is WFS1 (Wolfram syndrome 1), which plays important roles in ER homeostasis and pancreatic islets glucose-stimulated insulin secretion (GSIS). Accordingly and considering that feeding high-fat food has a major contribution in metabolic disorders, this study aimed to investigate the possible involvement of pancreatic ER stress in glucose metabolism impairment induced by feeding high-fat diet (HFD) in male rats. After weaning, the rats were divided into six groups, and fed on normal diet and HFD for 20 weeks, then 4-phenyl butyric acid (4-PBA, an ER stress inhibitor) was administered. Subsequently, in all groups, after performing glucose tolerance test, the animals were dissected and their pancreases were removed to extract ER, islets isolation and assessment of GSIS. Moreover, the pancreatic ER stress [binding of immunoglobulin protein (BIP) and enhancer-binding protein homologous protein (CHOP)] and oxidative stress [malondialdehyde (MDA), glutathione (GSH) and catalase] biomarkers as well as WFS1 expression level were evaluated. HFD decreased pancreatic WFS1 protein and GSH levels, and enhanced pancreatic catalase activity, MDA content, BIP and CHOP protein and mRNA levels as well as Wfs1 mRNA amount. Accordingly, it increased BIP, CHOP and WFS1 protein levels in the extracted ER of pancreas. In addition, the HFD caused glucose intolerance, and decreased the islets' GSIS and insulin content. However, 4-PBA administration restored the alterations. It seems that, HFD consumption through inducing pancreatic ER stress, altered WFS1 expression levels, reduced the islets' GSIS and insulin content and finally impaired glucose homeostasis.

Chronic Pharmacological Modulation of Mitochondrial Dynamics Alleviates Prediabetes-Induced Myocardial Ischemia-Reperfusion Injury by Preventing Mitochondrial Dysfunction and Programmed Apoptosis

PURPOSE

There is an increasing body of evidence to show that impairment in mitochondrial dynamics including excessive fission and insufficient fusion has been observed in the pre-diabetic condition. In pre-diabetic rats with cardiac ischemia-reperfusion (I/R) injury, acute treatment with a mitochondria fission inhibitor (Mdivi-1) and a fusion promoter (M1) showed cardioprotection. However, the potential preventive effects of chronic Mdivi-1 and M1 treatment in a pre-diabetic model of cardiac I/R have never been elucidated.

METHODS

Male Wistar rats (n = 40) were fed with a high-fat diet (HFD) for 12 weeks to induce prediabetes. Then, all pre-diabetic rats received the following treatments daily via intraperitoneal injection for 2 weeks: (1) HFDV (Vehicle, 0.1% DMSO); (2) HFMdivi1 (Mdivi-1 1.2 mg/kg); (3) HFM1 (M1 2 mg/kg); and (4) HFCom (Mdivi-1 + M1). At the end of treatment protocols, all rats underwent 30 min of coronary artery ligation followed by reperfusion for 120 min.

RESULTS

Chronic Mdivi-1, M1, and the combined treatment showed markedly improved cardiac mitochondrial function and dynamic control, leading to a decrease in cardiac arrhythmias, myocardial cell death, and infarct size (49%, 42%, and 51% reduction for HFMdivi1, HFM1, and HFCom, respectively vs HFDV). All of these treatments improved cardiac function following cardiac I/R injury in pre-diabetic rats.

CONCLUSION

Chronic inhibition of mitochondrial fission and promotion of fusion exerted cardioprevention in prediabetes with cardiac I/R injury through the relief of cardiac mitochondrial dysfunction and dynamic alterations, and reduction in myocardial infarction, thus improving cardiac function.

Obesity-Induced Brain Neuroinflammatory and Mitochondrial Changes

Obesity is defined as abnormal and excessive fat accumulation, and it is a risk factor for developing metabolic and neurodegenerative diseases and cognitive deficits. Obesity is caused by an imbalance in energy homeostasis resulting from increased caloric intake associated with a sedentary lifestyle. However, the entire physiopathology linking obesity with neurodegeneration and cognitive decline has not yet been elucidated. During the progression of obesity, adipose tissue undergoes immune, metabolic, and functional changes that induce chronic low-grade inflammation. It has been proposed that inflammatory processes may participate in both the peripheral disorders and brain disorders associated with obesity, including the development of cognitive deficits. In addition, mitochondrial dysfunction is related to inflammation and oxidative stress, causing cellular oxidative damage. Preclinical and clinical studies of obesity and metabolic disorders have demonstrated mitochondrial brain dysfunction. Since neuronal cells have a high energy demand and mitochondria play an important role in maintaining a constant energy supply, impairments in mitochondrial activity lead to neuronal damage and dysfunction and, consequently, to neurotoxicity. In this review, we highlight the effect of obesity and high-fat diet consumption on brain neuroinflammation and mitochondrial changes as a link between metabolic dysfunction and cognitive decline.

Combined caloric restriction and exercise provides greater metabolic and neurocognitive benefits than either as a monotherapy in obesity with or without estrogen deprivation

Neurodegeneration, as indicated by brain dysfunction and cognitive decline, is one of the complications associated with obesity and estrogen deprivation. Calorie restriction and exercise regimes improved brain function in neurodegenerative diseases. However, the comparative effects of a combination of calorie restriction with exercise, calorie restriction, and an exercise regime alone on brain/cognitive function in obesity with or without estrogen deprivation have not been investigated. Sixty female rats were fed a normal diet (ND) or a high-fat diet (HFD) for 27 weeks. At week 13, the ND-fed rats underwent a sham operation with sedentary lifestyle, HFD-fed rats were divided into two groups: each having either a sham operation (HFS) or ovariectomy (HFO). At week 20, HFD-fed rats in each group were divided into four subgroups undergoing either a sedentary lifestyle, calorie restriction, exercise regime or a combination of calorie restriction and exercise for 7 weeks. Insulin resistance, cognitive decline and hippocampal pathologies were found in both HFS and HFO rats. HFO rats had higher levels of insulin resistance and hippocampal reactive oxygen species levels than HFS rats. Calorie restriction decreased metabolic disturbance and hippocampal oxidative stress but failed to attenuate cognitive decline in HFS and HFO rats. Exercise attenuated metabolic/hippocampal dysfunctions, resulting in improved cognition only in HFS rats. Combined therapies restored brain function, and cognitive function in HFS and HFO rats. Therefore, a combination of calorie restriction with exercise is probably the greatest lifestyle modification to diminish the brain pathologies and cognitive decline in obesity with or without estrogen deprivation.

Cognitive Benefits of Physical Exercise, Physical-Cognitive Training, and Technology-Based Intervention in Obese Individuals with and without Postmenopausal Condition: A Narrative Review

Obesity and estrogen deprivation have been identified as significant risk factors for cognitive impairment. Thus, postmenopausal conditions when paired with obesity may amplify the risks of developing dementia. Physical exercise has been recommended as a primary treatment for preventing obesity-related comorbidities and alleviating menopausal symptoms. This narrative review aimed to summarize the effects of exercise on cognition in obese individuals with and without menopausal condition, along with potential physiological mechanisms linking these interventions to cognitive improvement. Research evidence has demonstrated that exercise benefits not only physical but also cognitive and brain health. Among various types of exercise, recent studies have suggested that combined physical-cognitive exercise may exert larger gains in cognitive benefits than physical or cognitive exercise alone. Despite the scarcity of studies investigating the effects of physical and combined physical-cognitive exercise in obese individuals, especially those with menopausal condition, existing evidence has shown promising findings. Applying these exercises through technology-based interventions may be a viable approach to increase accessibility and adherence to the intervention. More evidence from randomized clinical trials with large samples and rigorous methodology is required. Further, investigations of biochemical and physiological outcomes along with behavioral changes will provide insight into underlying mechanisms linking these interventions to cognitive improvement.

Inside the diabetic brain: Insulin resistance and molecular mechanism associated with cognitive impairment and its possible therapeutic strategies

Type 2 diabetes mellitus (T2DM) the most prevalent metabolic disease that has evolved into a major public health issue. Concerning about its secondary complications, a growing body of evidence links T2DM to cognitive impairment and neurodegenerative disorders. The underlying pathology behind this secondary complication disease is yet to be fully known. Nonetheless, they are likely to be associated with poor insulin signaling as a result of insulin resistance. We have combed through a rising body of literature on insulin signaling in the normal and diabetic brains along with various factors like insulin resistance, hyperglycemia, obesity, oxidative stress, neuroinflammation and Aβ plaques which can act independently or synergistically to link T2DM with cognitive impairments. Finally, we explored several pharmacological and non-pharmacological methods in the hopes of accelerating the rational development of medications for cognitive impairment in T2DM by better understanding these shared pathways.

Recent Advances in Progresses and Prospects of IL-37 in Central Nervous System Diseases

Interleukin-37 (IL-37) is an effective anti-inflammatory factor and acts through intracellular and extracellular pathways, inhibiting the effects of other inflammatory cytokines, such as IL-1β, IL-6, and tumor necrosis factor-α (TNF-α), thereby exerting powerful anti-inflammatory effects. In numerous recent studies, the anti-inflammatory effects of IL-37 have been described in many autoimmune diseases, colitis, and tumors. However, the current research on IL-37 in the field of the central nervous system (CNS) is not only less, but mainly for clinical research and little discussion of the mechanism. In this review, the role of IL-37 and its associated inflammatory factors in common CNS diseases are summarized, and their therapeutic potential in CNS diseases identified.

D-galactose-induced aging aggravates obesity-induced bone dyshomeostasis

We aimed to compare the time-course effect of D-galactose (D-gal)-induced aging, obesity, and their combined effects on bone homeostasis. Male Wistar rats were fed with either a normal diet (ND; n = 24) or a high-fat diet (HFD; n = 24) for 12 weeks. All rats were then injected with either vehicle or 150 mg/kg/day of D-gal for 4 or 8 weeks. Blood was collected to measure metabolic, aging, oxidative stress, and bone turnover parameters. Bone oxidative stress and inflammatory markers, as well as bone histomorphometry were also evaluated. Additionally, RAW 264.7 cells were incubated with either D-gal, insulin, or D-gal plus insulin to identify osteoclast differentiation capacity under the stimulation of receptor activator of nuclear factor κB ligand. At week 4, D-gal-induced aging significantly elevated serum malondialdehyde level and decreased trabecular thickness in ND- and HFD-fed rats, when compared to the control group. At week 8, D-gal-induced aging further elevated advanced glycation end products, increased bone inflammation and resorption, and significantly impaired bone microarchitecture in HFD-fed rats. The osteoclast number in vitro were increased in the D-gal, insulin, and combined groups to a similar extent. These findings suggest that aging aggravates bone dyshomeostasis in the obese condition in a time-dependent manner.

Pharmacological Targeting of Mitochondrial Fission and Fusion Alleviates Cognitive Impairment and Brain Pathologies in Pre-diabetic Rats

It has recently been accepted that long-term high-fat diet (HFD) intake is a significant possible cause for prediabetes and cognitive and brain dysfunction through the disruption of brain mitochondrial function and dynamic balance. Although modulation of mitochondrial dynamics by inhibiting fission and promoting fusion has been shown to reduce the morbidity and mortality associated with a variety of chronic diseases, the impact of either pharmacological inhibition of mitochondrial fission (Mdivi-1) or stimulation of fusion (M1) on brain function in HFD-induced prediabetic models has never been studied. Thirty-two male Wistar rats were separated into 2 groups and fed either a normal diet (ND, n = 8) or HFD (n = 24) for 14 weeks. At week 12, HFD-fed rats were divided into 3 subgroups (n = 8/subgroup) and given an intraperitoneal injection of either saline, Mdivi-1 (1.2 mg/kg/day), or M1 (2 mg/kg/day) for 2 weeks. Cognitive function and metabolic parameters were determined toward the end of the protocol. The rats then were euthanized, and the brain was immediately removed in order to evaluate brain mitochondrial function and mitochondrial dynamics. HFD-fed rats experienced prediabetes, evidenced by elevated plasma insulin and the HOMA index, impaired mitochondrial function in the brain, altered dynamic regulation, and cognitive impairment were also found. Mdivi-1 and M1 treatment exerted neuroprotection to a similar extent by improving metabolic parameters, balancing mitochondrial dynamics, and reducing mitochondrial dysfunction, resulting in a gradual increase in cognitive function. Therefore, pharmacological targeting of mitochondrial fission and fusion protected the brain against chronic HFD-induced prediabetes.

Sexual dimorphism in cardiometabolic and cardiac mitochondrial function in obese rats following sex hormone deprivation

OBJECTIVE

Our study aims to test the hypothesis that poorer function of cardiac mitochondria in males, under sex hormone-deprived and obese-insulin-resistant conditions, is responsible for a worse cardiometabolic function than females.

METHODS

One hundred and forty-four rats were subjected to receive either 12 weeks of normal diet (ND) or a high-fat diet (HFD) consumption following the induction of sex hormone deprivation. Temporal evaluations of metabolic parameters, cardiac autonomic modulation, left ventricular (LV) contractile, and mitochondrial functions were measured after starting each feeding protocol for 4, 8, and 12 weeks.

RESULTS

After HFD feeding for 8 weeks, increased plasma insulin and HOMA index were initially observed in male HFD-fed sham-operated rats (M-HFS), male HFD-fed orchiectomized rats (M-HFO), female ND-fed ovariectomized rats (F-OVX), female HFD-fed sham-operated rats (F-HFS), and female HFD-fed ovariectomized rats (F-HFO) groups. In addition, as early as week 4, male ND-fed orchiectomized rats (M-ORX) and M-HFO exhibited impaired cardiac autonomic balance, LV contractile and mitochondrial functions, whereas M-HFS and F-HFO developed these impairments at week 8 and F-OVX and F-HFS exhibited them at week 12.

CONCLUSION

We concluded that sex hormone-deprived females are prone to develop metabolic impairments, whereas males are more likely to have cardiac autonomic impairment, LV contractile and mitochondrial dysfunction even in the absence of obese-insulin-resistant condition. However, under estrogen-deprived condition, these impairments were further accelerated and aggravated by obese-insulin resistance.

Effectiveness of high cardiorespiratory fitness in cardiometabolic protection in prediabetic rats

Background

Caloric restriction and exercise are lifestyle interventions that effectively attenuate cardiometabolic impairment. However, cardioprotective effects of long-term lifestyle interventions and short-term lifestyle interventions followed by weight maintenance in prediabetes have never been compared. High cardiorespiratory fitness (CRF) has been shown to provide protection against prediabetes and cardiovascular diseases, however, the interactions between CRF, prediabetes, caloric restriction, and exercise on cardiometabolic health has never been investigated.

Methods

Seven-week-old male Wistar rats were fed with either a normal diet (ND; n = 6) or a high-fat diet (HFD; n = 30) to induce prediabetes for 12 weeks. Baseline CRF and cardiometabolic parameters were determined at this timepoint. The ND-fed rats were fed continuously with a ND for 16 more weeks. The HFD-fed rats were divided into 5 groups (n = 6/group) to receive one of the following: (1) a HFD without any intervention for 16 weeks, (2) 40% caloric restriction for 6 weeks followed by an ad libitum ND for 10 weeks, (3) 40% caloric restriction for 16 weeks, (4) a HFD plus an exercise training program for 6 weeks followed by a ND without exercise for 10 weeks, or (5) a HFD plus an exercise training program for 16 weeks. At the end of the interventions, CRF and cardiometabolic parameters were re-assessed. Then, all rats were euthanized and heart tissues were collected.

Results

Either short-term caloric restriction or exercise followed by weight maintenance ameliorated cardiometabolic impairment in prediabetes, as indicated by increased insulin sensitivity, improved blood lipid profile, improved mitochondrial function and oxidative phosphorylation, reduced oxidative stress and inflammation, and improved cardiac function. However, these benefits were not as effective as those of either long-term caloric restriction or exercise. Interestingly, high-level baseline CRF was correlated with favorable cardiac and metabolic profiles at follow-up in prediabetic rats, both with and without lifestyle interventions.

Conclusions

Short-term lifestyle modification followed by weight maintenance improves cardiometabolic health in prediabetes. High CRF exerted protection against cardiometabolic impairment in prediabetes, both with and without lifestyle modification. These findings suggest that targeting the enhancement of CRF may contribute to the more effective treatment of prediabetes-induced cardiometabolic impairment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00458-9.

Profiles of gut microbiota in obese-insulin-resistant rats treated with biotics

PURPOSE

Our previous studies demonstrated the beneficial effects of the probiotic Lactobacillus paracasei HII01, prebiotic xylooligosaccharide (XOS), and synbiotics on several parameters in high-fat diet (HFD)-induced obese rats. However, the gut microbiota composition in these rats has not been investigated. Therefore, this study aimed to investigate the impact of biotic therapies on gut microbiota in HFD-induced obese-insulin-resistant rats.

METHODS

Male Wistar rats were fed with a normal diet (ND, n = 5) and a HFD (n = 20) for 24 weeks. At week 13, HFD-fed rats were given either a probiotic (L. paracasei, HF-Pro, n = 5), prebiotic (XOS, HF-Pre, n = 5), synbiotic (XOS + L. paracasei, HF-Syn, n = 5), or vehicle (HF-V, n = 5) for 12 weeks. ND-fed rats received vehicle (ND-V, n = 5). At week 24, all rats were decapitated, and metabolic parameters and gut microbiota were analyzed.

RESULTS

HF-V rats developed an obese-insulin-resistant condition as indicated by impaired metabolic parameters. The prebiotic and synbiotic restored those metabolic parameters to the same level of ND-V rats. The gut microbiota composition of ND-V and HF-V rats differed as indicated by beta diversity. Verrucomicrobia in ND-V rats and Firmicutes and Proteobacteria in HF-V rats were dominant. Interestingly, Verrucomicrobia was also prominent in the HF-Syn rats. HF-Pre rats showed a distinct gut microbiota the predominant family being Ruminococcaceae.

CONCLUSION

The changes in gut microbiota after HFD consumption included increased Firmicutes and Proteobacteria. The treatment with the prebiotic and synbiotic showed an association with the increase in Ruminococcaceae and Verrucomicrobia, respectively. These changes in gut microbiota due to biotics may mediate the beneficial effects on metabolic parameters.

Hyperbaric oxygen therapy improves age induced bone dyshomeostasis in non-obese and obese conditions

AIMS

To investigate the effects of hyperbaric oxygen therapy (HBOT) on metabolic disturbance, aging and bone remodeling in D-galactose-induced aging rats with and without obesity by determining the metabolic parameters, aging and oxidative stress markers, bone turnover markers, bone microarchitecture, and bone biomechanical strength.

MATERIALS AND METHODS

Male Wistar rats were fed either a normal diet (ND; n = 18) or a HFD (n = 12) for 22 weeks. At week 13, vehicle (0.9% NaCl) was injected into ND-fed rats (NDV; n = 6), while 150 mg/kg/day of D-galactose was injected into 12 ND-fed rats (NDD) and 12 HFD-fed rats (HFDD) for 10 weeks. At week 21, rats were treated with either sham (NDVS, NDDS, or HFDDS; n = 6/ group) or HBOT (NDDH, or HFDDH; n = 6/group) for 14 days. Rats were then euthanized. Blood samples, femora, and tibiae were collected.

KEY FINDINGS

Both NDD and HFDD groups developed aging as indicated by increased AGE level, increased inflammation and oxidative stress as shown by raised serum TNF-α and MDA levels, impaired bone remodeling as indicated by an increase in levels of CTX-1, TRACP-5b, and impaired bone structure/strength, when compared with those of the NDVS group. HFD aggravated these indicators of bone dyshomeostasis in D-galactose-treated rats. HBOT restored bone remodeling and bone structure/strength in the NDD group, however HBOT ameliorated bone dyshomeostasis in the HFDD group.

SIGNIFICANCE

HBOT is a potential intervention to decrease the risk of osteoporosis and bone fracture in aging with or without obesity.

Peripheral versus central insulin and leptin resistance: Role in metabolic disorders, cognition, and neuropsychiatric diseases

Insulin and leptin are classically regarded as peptide hormones that play key roles in metabolism. In actuality, they serve several functions in both the periphery and central nervous system (CNS). Likewise, insulin and leptin resistance can occur both peripherally and centrally. Metabolic disorders such as diabetes and obesity share several key features including insulin and leptin resistance. While the peripheral effects of these disorders are well-known (i.e. cardiovascular disease, hypertension, stroke, dyslipidemia, etc.), the CNS complications of leptin and insulin resistance have come into sharper focus. Both preclinical and clinical findings have indicated that insulin and leptin resistance are associated with cognitive deficits and neuropsychiatric diseases such as depression. Importantly, these studies also suggest that these deficits in neuroplasticity can be reversed by restoration of insulin and leptin sensitivity. In view of these observations, this review will describe, in detail, the peripheral and central functions of insulin and leptin and explain the role of insulin and leptin resistance in various metabolic disorders, cognition, and neuropsychiatric diseases.

Modulating mitochondrial dynamics attenuates cardiac ischemia-reperfusion injury in prediabetic rats

Mitochondria are extraordinarily dynamic organelles that have a variety of morphologies, the status of which are controlled by the opposing processes of fission and fusion. Our recent study shows that inhibition of excessive mitochondrial fission by Drp1 inhibitor (Mdivi-1) leads to a reduction in infarct size and left ventricular (LV) dysfunction following cardiac ischemia-reperfusion (I/R) injury in high fat-fed induced pre-diabetic rats. In the present study, we investigated the cardioprotective effects of a mitochondrial fusion promoter (M1) and a combined treatment (M1 and Mdivi-1) in pre-diabetic rats. Wistar rats were given a high-fat diet for 12 weeks to induce prediabetes. The rats then subjected to 30 min-coronary occlusions followed by reperfusion for 120 min. These rats were intravenously administered M1 (2 mg/kg) or M1 (2 mg/kg) combined with Mdivi-1 (1.2 mg/kg) prior to ischemia, during ischemia or at the onset of reperfusion. We showed that administration of M1 alone or in combination with Mdivi-1 prior to ischemia, during ischemia or at the onset of reperfusion all significantly attenuated cardiac mitochondrial ROS production, membrane depolarization, swelling and dynamic imbalance, leading to reduced arrhythmias and infarct size, resulting in improved LV function in pre-diabetic rats. In conclusion, the promotion of mitochondrial fusion at any time-points during cardiac I/R injury attenuated cardiac mitochondrial dysfunction and dynamic imbalance, leading to decreased infarct size and improved LV function in pre-diabetic rats.

Lactiplantibacillus plantarum dfa1 Outperforms Enterococcus faecium dfa1 on Anti-Obesity in High Fat-Induced Obesity Mice Possibly through the Differences in Gut Dysbiosis Attenuation, despite the Similar Anti-Inflammatory Properties

Fat reduction and anti-inflammation are commonly claimed properties of probiotics. Lactiplantibacillus plantarum and Enterococcus faecium were tested in high fat-induced obesity mice and in vitro experiments. After 16 weeks of probiotics, L. plantarum dfa1 outperforms E. faecium dfa1 on the anti-obesity property as indicated by body weight, regional fat accumulation, serum cholesterol, inflammatory cytokines (in blood and colon tissue), and gut barrier defect (FITC-dextran assay). With fecal microbiome analysis, L. plantarum dfa1 but not E. faecium dfa1 reduced fecal abundance of pathogenic Proteobacteria without an alteration in total Gram-negative bacteria when compared with non-probiotics obese mice. With palmitic acid induction, the condition media from both probiotics similarly attenuated supernatant IL-8, improved enterocyte integrity and down-regulated cholesterol absorption-associated genes in Caco-2 cell (an enterocyte cell line) and reduced supernatant cytokines (TNF-α and IL-6) with normalization of cell energy status (extracellular flux analysis) in bone-marrow-derived macrophages. Due to the anti-inflammatory effect of the condition media of both probiotics on palmitic acid-activated enterocytes was neutralized by amylase, the active anti-inflammatory molecules might, partly, be exopolysaccharides. As L. plantarum dfa1 out-performed E. faecium dfa1 in anti-obesity property, possibly through the reduced fecal Proteobacteria, with a similar anti-inflammatory exopolysaccharide; L. plantarum is a potentially better option for anti-obesity than E. faecium.

Inhibition of myeloid differentiation factor 2 attenuates cardiometabolic impairments via reducing cardiac mitochondrial dysfunction, inflammation, apoptosis and ferroptosis in prediabetic rats

Systemic inflammation is a key mediator of left ventricular dysfunction (LV) in prediabetes via the activation of myeloid differentiation factor 2 (MD2)/toll-like receptor 4 complex. The MD2 inhibitor L6H21 effectively reduced systemic and cardiac inflammation in obese mice. However, its effects on cardiac function and regulated cell death pathways in the heart in prediabetes are still unknown. The prediabetic rats were divided into 3 subgroups to receive vehicle, L6H21 (10, 20, 40 mg/kg) or metformin (300 mg/kg) for 1, 2 and 4 weeks. Then, metabolic parameters, cardiac sympathovagal balance, LV function, cardiac mitochondrial function, oxidative stress, inflammation, apoptosis, necroptosis, and ferroptosis were determined. All prediabetic rats exhibited cardiac sympathovagal imbalance, LV dysfunction, and cardiac mitochondrial dysfunction. All doses of L6H21 treatment for 2- and 4-weeks attenuated insulin resistance. L6H21 at 40 mg/kg attenuated cardiac autonomic imbalance and LV dysfunction after 1 week of treatment. Both 10 and 20 mg/kg of L6H21 required longer treatment duration to show these benefits. Mechanistically, all doses of L6H21 reduced cardiac mitochondrial dysfunction after 1 week of treatment, resulting in alleviated oxidative stress and inflammation. L6H21 also effectively suppressed cardiac apoptosis and ferroptosis, but it did not affect necroptosis in prediabetic rats. L6H21 provided the cardioprotective efficacy in dose- and time-dependent manners in prediabetic rats via reduction in apoptosis and ferroptosis.

Management of diabetic neuropathy

Diabetic neuropathy is a neurodegenerative disorder that may alter both the somatic and autonomic peripheral nervous systems in the context of diabetes mellitus (DM). It is a prevalent and burdensome chronic complication of DM, that requires timely management. Optimized glycemic control (mainly for type 1 DM), multifactorial intervention (mainly for type 2 DM), with lifestyle intervention/physical exercise, and weight loss represent the basis of management for diabetic distal symmetrical polyneuropathy, and should be implemented early in the disease course. Despite better understanding of the pathogenetic mechanisms of diabetic peripheral neuropathy, there is still a stringent need for more pathogenetic-based agents that would significantly modify the natural history of the disease. The paper reviews the available drugs and current recommendations for the management of distal symmetrical polyneuropathy, including pain management, and for diabetic autonomic neuropathy. Evaluation of drug combinations that would perhaps be more efficient in slowing the progression of the disease or even reversing it, and that would provide a better pain management is still needed.

Effects of apolipoprotein E isoform, sex, and diet on insulin BBB pharmacokinetics in mice

Age, apolipoprotein E (apoE) isoform, sex, and diet can independently affect the risk for the development of Alzheimer’s disease (AD). Additionally, synergy between some of these risk factors have been observed. However, the relation between the latter three risk factors has not been investigated. Central nervous system (CNS) insulin resistance is commonly involved in each of these risk factors. CNS insulin is primarily derived from the periphery in which insulin must be transported across the blood–brain barrier (BBB). Additionally, insulin can bind the brain endothelial cell to affect intracellular signaling. Therefore, we hypothesized CNS access to insulin could be affected by the combination of apoE isoform, sex, and diet. We analyzed insulin BBB pharmacokinetics in aged apoE targeted replacement (E3 and E4) male and female mice on a low-fat and high-fat diet. There were differences within males and females due to apoE genotype and diet in insulin interactions at the BBB. These sex-, diet-, and apoE isoform-dependent differences could contribute to the cognitive changes observed due to altered CNS insulin signaling.

Palonosetron/Methyllycaconitine Deactivate Hippocampal Microglia 1, Inflammasome Assembly and Pyroptosis to Enhance Cognition in a Novel Model of Neuroinflammation

Since westernized diet-induced insulin resistance is a risk factor in Alzheimer's disease (AD) development, and lipopolysaccharide (LPS) coexists with amyloid β (Aβ)1-42 in these patients, our AD novel model was developed to resemble sporadic AD by injecting LPS into high fat/fructose diet (HFFD)-fed rats. The neuroprotective potential of palonosetron and/or methyllycaconitine, 5-HT3 receptor and α7 nAChR blockers, respectively, was evaluated after 8 days of daily administration in HFFD/LPS rats. All regimens improved histopathological findings and enhanced spatial memory (Morris Water Maze); however, palonosetron alone or with methyllycaconitine promoted animal performance during novel object recognition tests. In the hippocampus, all regimens reduced the expression of glial fibrillary acidic protein and skewed microglia M1 to M2 phenotype, indicated by the decreased M1 markers and the enhanced M2 related parameters. Additionally, palonosetron and its combination regimen downregulated the expression of ASC/TMS1, as well as levels of inflammasome downstream molecules and abated cleaved caspase-1, interleukin (IL)-1β, IL-18 and caspase-11. Furthermore, ACh and 5-HT were augmented after being hampered by the insult. Our study speculates that blocking 5-HT3 receptor using palonosetron overrides methyllycaconitine to combat AD-induced neuroinflammation and inflammasome cascade, as well as to restore microglial function in a HFFD/LPS novel model for sporadic AD.

Empagliflozin nanoparticles attenuates type2 diabetes induced cognitive impairment via oxidative stress and inflammatory pathway in high fructose diet induced hyperglycemic mice

There is snowballing evidence that type 2 diabetes (T2D) predisposes to neuropathophysiological alterations including oxidative stress and triggered inflammatory responses in brain that eventually culminates into cognitive impairment.Accumulating evidences suggest that SGLT2 inhibitor can be a promising intervention for cognitive decline in T2DM. In the present paper, the potential effects of Empagliflozin (EMPA), a SGLT2 inhibitor, against T2D induced cognitive dysfunction have been explored. The effect of EMPA on array of inflammatory mediators including Interleukin-6(IL-6), Interleukin -1β (IL-1β), and Tumour necrosis factor-α(TNF-α)), neuronal proteins including glycogen synthase kinase-3β (GSK- 3β), Phosphorylated tau (p-tau), amyloid beta (Aβ) (1-40, 1-42) and altered oxidative parameters including SOD, catalase, TBARS was determined in the high fructose diet induced hyperglycaemic mice. The obtained results were compared with EMPA nanoparticles (Nps) formulated in our laboratory and found that EMPA Nps significantly showed reduced levels of inflammatory mediators and oxidative stress. Further, decrease in levels of p-tau, Aβ (1-40) and Aβ (1-42) were also observed with EMPA nanoparticles.Thus, the study has demonstrated that EMPA Nps could be a promising therapy to alleviate the progression of cognitive decline in T2D.

The Role of BMI, Body Fat Mass and Visceral Fat in Executive Function in Individuals with Overweight and Obesity

Evidence accumulated to date suggests that excess weight in the adult population is associated with a wide range of impairments in executive function. However, most studies have only examined the influence of body mass index (BMI) on the cognitive function of individuals with overweight and obesity. This study examined the potential associations of markers of adiposity (BMI, body fat, and visceral fat) with five domains of executive function including cognitive flexibility, inhibition, monitoring, planning, and working memory in a sample of 87 adult with overweight (n = 34) and obesity (n = 53). The results show that obese people had poorer working memory than those with overweight. After controlling for educational levels and physical activity, the results suggest that neither the waist-hip index not visceral fat were associated with cognitive function. In overweight, body fat was negatively associated with executive components of inhibition (p = 0.05) and monitoring (p = 0.02). In the obesity subgroup, body fat was negatively associated with inhibition (0.02) and working memory (0.04). The results provide evidence of the importance of adiposity for cognitive function. The implications for understanding the influence of markers of adiposity in adults with overweight and obesity are discussed.

Activation of Hippocampal IR/IRS-1 Signaling Contributes to the Treatment with Zuogui Jiangtang Jieyu Decoction on the Diabetes-Related Depression

Background

Zuogui Jiangtang Jieyu decoction (ZJJ) is mainly used for the treatment of diabetes-related depression in current clinical applications and research. This study aims to investigate whether the brain IR/IRS-1 signaling pathway is involved in the therapeutic effect of ZJJ on depression-like behavior in diabetic rats.

Methods

Sprague–Dawley rats were fed with high-fat diet and subjected to streptozotocin injection to establish the diabetes animal model. After treatment with different doses of ZJJ (20.530 g/kg or 10.265 g/kg) for 4 weeks, the blood glucose level and peripheral insulin resistance were measured. The forced-swimming test (FST) and Morris water maze test (MWMT) were applied for the mood and cognitive function assessment. Then, the Western blot method was used to analyze the protein levels of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), phosphatidylonositol-3-kinase (PI3K), and protein kinase B (PKB, also as known as AKT) in the hippocampus of diabetic rats. Meanwhile, the immunofluorescence method was performed to analyze the above proteins' expression in the neuron and astrocyte. At last, the levels of glycogen, lactate, and ATP were tested by the ELISA method. Additionally, the insulin-sensitive glucose transporter 4 (GLUT4) and the lactate transporter monocarboxylate transporter 4 (MCT4) were analyzed by the Western blot method.

Results

ZJJ administration significantly decreased the level of blood glucose and improved the peripheral insulin resistance in diabetic rats. Besides, ZJJ attenuated the depression-like behavior and the cognitive dysfunction in rats with diabetes. Furthermore, we found the upregulation of protein expression of phospho-IR, phospho-IRS-1, phospho-PI3K, and phospho-AKT in the hippocampus of diabetic rats after being treated with ZJJ. Moreover, the above proteins are increased not only in the neuron but also in the astrocyte after ZJJ administration. In addition, ZJJ increased the content of ATP, glycogen, and lactate, as well as the expression of GLUT4 and MCT4 in the hippocampus of diabetic rats.

Conclusions

These findings suggest that ZJJ improves the depression-like behavior of diabetic rats by activating the IR/IRS-1 signaling pathway in both hippocampal neuron and astrocyte. And the brain IR/IRS-1 signaling pathway plays an important role in astrocyte-neuron metabolic coupling, providing a potential mechanism by which the IR/IRS-1 signaling pathway may contribute to the treatment of ZJJ on diabetes-related depression.

Lactobacillus acidophilus LA5 improves saturated fat-induced obesity mouse model through the enhanced intestinal Akkermansia muciniphila

Obesity, a major healthcare problem worldwide, induces metabolic endotoxemia through the gut translocation of lipopolysaccharides (LPS), a major cell wall component of Gram-negative bacteria, causing a chronic inflammatory state. A combination of several probiotics including Lactobacillus acidophilus 5 (LA5), a potent lactic acid-producing bacterium, has previously been shown to attenuate obesity. However, data on the correlation between a single administration of LA5 versus microbiota alteration might be helpful for the probiotic adjustment. LA5 was administered daily together with a high-fat diet (HFD) for 8 weeks in mice. Furthermore, the condition media of LA5 was also tested in a hepatocyte cell-line (HepG2 cells). Accordingly, LA5 attenuated obesity in mice as demonstrated by weight reduction, regional fat accumulation, lipidemia, liver injury (liver weight, lipid compositions, and liver enzyme), gut permeability defect, endotoxemia, and serum cytokines. Unsurprisingly, LA5 improved these parameters and acidified fecal pH leads to the attenuation of fecal dysbiosis. The fecal microbiome analysis in obese mice with or without LA5 indicated; (i) decreased Bacteroidetes (Gram-negative anaerobes that predominate in non-healthy conditions), (ii) reduced total fecal Gram-negative bacterial burdens (the sources of gut LPS), (iii) enhanced Firmicutes (Gram-positive bacteria with potential benefits) and (iv) increased Verrucomycobia, especially Akkermansia muciniphila, a bacterium with the anti-obesity property. With LA5 administration, A. muciniphila in the colon were more than 2,000 folds higher than the regular diet mice as determined by 16S rRNA. Besides, LA5 produced anti-inflammatory molecules with a similar molecular weight to LPS that reduced cytokine production in LPS-activated HepG2 cells. In conclusion, LA5 attenuated obesity through (i) gut dysbiosis attenuation, partly through the promotion of A. muciniphila (probiotics with the difficulty in preparation processes), (ii) reduced endotoxemia, and (iii) possibly decreased liver injury by producing the anti-inflammatory molecules.

The chemical chaperon 4-phenyl butyric acid restored high-fat diet- induced hippocampal insulin content and insulin receptor level reduction along with spatial learning and memory deficits in male rats

This study assessed the effect of a chronic high-fat diet (HFD) on plasma and hippocampal insulin and corticosterone levels, the hippocampus insulin receptor amount, and spatial learning and memory with or without receiving 4-phenyl butyric acid (4-PBA) in male rats. Rats were divided into high-fat and normal diet groups, then each group was subdivided into dimethyl sulfoxide (DMSO) and 4-PBA groups. After weaning, the rats were fed with HFD for 20 weeks. Then, 4-PBA or DMSO were injected for 3 days. Subsequently, oral glucose tolerance test was done. On the following day, spatial memory tests were performed. Then the hippocampus Bip, Chop, insulin, corticosterone, and insulin receptor levels were determined. HFD increased plasma glucose, leptin and corticosterone concentrations, hippocampus Bip, Chop and corticosterone levels, food intake, abdominal fat weight and body weight along with impaired glucose tolerance. It decreased plasma insulin, and insulin content, and its receptor amount in hippocampus. HFD lengthened escape latency and shortened the duration spent in target zone. 4-PBA administration improved the HFD- induced adverse changes. Chronic HFD possibly through the induction of endoplasmic reticulum (ER) stress and subsequent changes in the levels of hippocampal corticosterone, insulin and insulin receptor along with possible leptin resistance caused spatial learning and memory deficits.