Chow Diet Research Articles

Smilax china L. polysaccharide prevents HFD induced-NAFLD by regulating hepatic fat metabolism and gut microbiota

BackgroundThe increasing incidence of nonalcoholic fatty liver disease(NAFLD) has urged the development of new therapeutics. NAFLD is intimately linked to gut microbiota due to the hepatic portal system, and utilizing natural polysaccharides as prebiotics has become a prospective strategy for preventing NAFLD. Smilax china L. polysaccharide (SCP) possesses excellent hepatoprotective and anti-inflammatory activity. However, its protective effects on NAFLD remains unclear. PurposeThe goal of this study was to explore the protective effects of SCP on high-fat diet (HFD)-induced NAFLD mice by regulating hepatic fat metabolism and gut microbiota. MethodsExtraction and isolation from Smilax china L. rhizome to obtain SCP. C57BL/6J mice were distributed to six groups: Control (normal chow diet), HFD-fed mice were assigned to HFD, simvastatin (SVT), and low-, medium-, high-doses of SCP for 12 weeks. The body, liver, and different adipose tissues weights were detected, and lipids in serum and liver were assessed. RT-PCR and Western blot were used to detect the hepatic fat metabolism-related genes and proteins. Gut microbiota of cecum contents was profiled through 16S rRNA gene sequencing. ResultsSCP effectively reversed HFD-induced increase weights of body, liver, and different adipose tissues. Lipid levels of serum and liver were also significantly reduced after SCP intervention. According to the results of RT-PCR and western blot analysis, SCP treatment up-regulated the genes and proteins related to lipolysis were up-regulated, while lipogenesis-related genes and proteins were down-regulated. Furthermore, the HFD-induced dysbiosis of intestinal microbiota was similarly repaired by SCP intervention, including enriching beneficial bacteria and depleting harmful bacteria. ConclusionSCP could effectively prevent HFD-induced NAFLD, might be considered as a prebiotic agent due to its excellent effects on altering hepatic fat metabolism and maintaining gut microbiota homeostasis.

Skeletal Muscle Mitochondrial Response to Diet Differs by Genotype and Sex in an Alzheimer’s Disease Mouse Model

Introduction: Skeletal muscle mass is reduced in the early stages of cognitive decline. Apolipoprotein ε4 ( APOE4) is the most prevalent genetic risk factor for Alzheimer’s disease (AD) and is associated with faster motor decline in cognitively healthy individuals. APOE4 also increases the risk of insulin resistance and cardiovascular disease, conditions associated with altered bioenergetic function in muscle. However, no studies have examined the role of APOE4 in modulating muscle physiology and the impact this would have on cognitive function. We sought to determine if APOE4 affects skeletal muscle mitochondrial metabolism in response to a high-fat diet (HFD) and if this is reflected in whole-body metabolism. We also examined the role of sex since APOE4 carriers who are female are more likely to develop AD. Methods: Male and female APOE3 (n=32) and APOE4 (n= 29) targeted-replacement mice on a C57BL/6 background purchased from Taconic were fed a standard chow diet until 4 months old. Mice were then switched to a low-fat diet (LFD, 10% kcal fat) or HFD (45% kcal fat) until sacrifice. Glucose tolerance was tested at 7 months by administering an intraperitoneal glucose injection of 1g/kg lean mass. Blood glucose was measured before and 15, 30, 45, 60, 90 and 120 minutes after glucose injection. Resting respiratory exchange ratio (RER) was determined using the Promethion Indirect Calorimetry system at 8 months to determine the relative contribution of carbohydrates versus lipids to whole body metabolism. Mice were sacrificed at 9 months and carbohydrate-driven oxygen consumption was measured at basal, state 3 (ADP), state 3 + glutamate, state 3S (succinate) and uncoupled respiratory states in mitochondria isolated from quadriceps tissue on the Oroboros Oxygraph-2k system. Results: Mice fed a HFD had greater glucose area under the curve (p<0.0001) and reduced RER (p= <0.001) compared to mice fed a LFD, regardless of sex or genotype. At the level of skeletal muscle, APOE4 female mice had increased state 3 (p=0.027) and state 3 + glutamate oxygen consumption (p=0.037) on a HFD compared to a LFD while no diet effect was observed in APOE4 males or any APOE3 mice. Conclusion: We provide evidence that female APOE4 mice are susceptible to diet-induced increases in carbohydrate-driven mitochondrial oxygen consumption in muscle. Future studies are needed to determine the underlying mechanism and consequences of increased muscle mitochondrial activity, which could help identify treatment targets in female APOE4 carriers. BHTP T32 AG078114, P30 AG072973 (Chelsea Johnson). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Functional in vivo effects of an ENaC Na+ self inhibition-enhancing mutation

Background: Epithelial Na+ channel (ENaC)-mediated Na+ reabsorption in the distal nephron is a critical regulator of extracellular fluid volume and K+ homeostasis. Physiologic concentrations of extracellular Na+ reduce channel activity (open probability; PO) via an allosteric mechanism termed “Na+ self-inhibition,” which involves Na+ ions binding to specific sites in the channel’s extracellular domains. Recent studies have identified human ENaC mutations that alter the Na+ self-inhibition response when assayed in vitro. Such mutations may confer sensitivity or resistance to salt-induced blood pressure changes. Using CRISPR-Cas9 technology, we generated mice carrying a mutation previously shown to enhance Na+ self-inhibition (αH282R) to assess the effects on ENaC-dependent Na+ transport in vivo. We predicted that ENaC activity would be reduced in these mice, leading to enhanced sensitivity to Na+ deprivation or K+ loading, along with accompanying compensatory changes to overcome the predicted loss of function. Methods: We measured urinary electrolyte handling in wild type (WT) and αH282R mice maintained on normal, low Na+, or high K+ diets using metabolic cages. We assessed ENaC activity ex vivo using patch clamp and Ussing chamber methods. We also measured blood chemistry and aldosterone levels in WT and αH282R mice under the dietary conditions described above. Results: When maintained on a normal chow diet (0.3% NaCl), αH2832R mice expressed ENaCs in the distal nephron with reduced PO compared to WT littermates (0.026 vs. 0.067; p<0.01), while ENaC subunit protein expression was unaltered. Amiloride-sensitive short-circuit currents were reduced in the distal colons of αH283R mice versus WT littermates (-12.6 vs. -3.9 μA/cm2; p<0.01). Plasma aldosterone levels were also higher in αH283R versus WT mice on a control diet (610 vs 288 pg/mL; p=0.02), while no other differences in baseline blood chemistry were observed. When challenged with either dietary Na+ restriction (<0.01% NaCl) or K+ loading (10% KCl), WT and αH283R mice responded similarly in terms of body weight maintenance, urinary Na+ and K+ excretion, and systemic electrolyte and metabolic parameters, with the exception of higher aldosterone levels in Na+-restricted αH282R mice compared to WT littermates (2,759 vs. 1271 pg/mL; p<0.01). Conclusions: The αH282R mutation, which enhances Na+ self-inhibition, confers reduced ENaC activity in mice. However, this loss of function may be compensated by ENaC-independent Na+/K+ handling mechanisms and/or increased aldosterone signaling during adaptation to dietary salt stressors. P30DK079307, T32DK061296. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Impact of Aging and High-Fat Diet on Adipose Tissue-Derived Extracellular Vesicle miRNA Profiles in Mice

Background: Middle-aged adults show the highest obesity rates, leading to significant health complications in later years. Obesity triggers the release of altered molecules including extracellular vesicles (EVs) from excess adipose tissue (AT), contributing to various health complications. In this study, we assessed the effects of age and high-fat diet (HFD) on white AT-derived EV miRNA profiles to understand their potential roles in aging and obesity. Hypothesis: Our hypothesis is that the white AT-derived EV miRNA profiles of middle-aged mice fed HFD will demonstrate deleterious features due to the potential synergistic effects of aging and long-term HFD consumption. Method: C57BL/6 male mice were subjected to a normal chow diet (NCD) or a HFD for either 10-12 weeks (young mice, n=10) or 50-61 weeks (middle-aged mice, n=12). After evaluating metabolic characteristics, white AT-derived EV miRNAs were profiled using a NanoString miRNA panel (n=599). Results: Middle-aged mice exhibited obesity regardless of diet. Young mice fed HFD showed similar metabolic traits to middle-aged mice. In NCD group, 131 differentially expressed miRNAs (DE-miRNAs) emerged in middle-aged mice compared to young mice, including miR-21, miR-148a, and miR-29a associated with cancer, neuro/psychological disorders and reproductive diseases. In HFD group, 55 DE-miRNAs were revealed in middle-aged mice compared to young mice. These miRNAs were associated with significantly suppressed IGF1R activity. Conclusion: This study has demonstrated the altered characteristics of WAT EV miRNAs by aging and diet. Aging and diet induce significant changes in EV miRNA profiles of AT. We suggest that there might be a selective sorting mechanism of miRNAs in AT EVs, contributing to the disease progress or pathogenesis related to aging and obesity. We also suggest that AT EVs in middle-aged mice fed HFD might play a protective role in aging and obesity by inhibiting IGF1R activity. University of Iowa College of Nursing. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Exercise Pressor Reflex Function Is Exacerbated in Decerebrate Adenine-Induced Chronic Kidney Disease Rats

Cardiovascular disease is the leading cause of death in chronic kidney disease (CKD). While the underlying mechanisms are not completely understood, elevated sympathetic nerve activity (SNA) and exercise intolerance are thought to play an important role. In normal physiological conditions, sympathetic modulation of the cardiovascular system during physical activity is largely governed by a peripheral neural reflex originating in contracting skeletal muscle, known as the exercise pressor reflex (EPR). Pioneering work by Park et al. demonstrated that CKD patients exhibited abnormal SNA and blood pressure (BP) elevations during both static and rhythmic handgrip exercise, suggesting an overactive EPR. However, due to experimental design constraints inherent to humans, the contribution of the EPR to the augmented SNA and BP responses to exercise could not be fully addressed. Therefore, the purpose of this study was to specifically test EPR function in CKD using a reduced animal model. Sprague-Dawley rats were randomly assigned to receive either a powdered chow diet containing adenine (0.25%w/w in feed) to induce CKD or a powdered chow diet alone (control group) for 12 weeks. Subsequently, in decerbrate animals, we measured mean arterial pressure (MAP) and renal SNA (RSNA) in response to isolated EPR activation during hindlimb muscle contraction (i.e., simulated exercise). We further assessed cardiovascular and sympathetic responses to passive muscle stretch to stimulate the mechanoreflex (i.e., activation of the mechanically-sesnsitive component of the EPR), and intra-arterial capsaicin administratration to activate the metaboflex (i.e., stimulation of the metabolically-sensitive component of the EPR). After completion of the diet, levels of plasma creatinine were significantly increased in adenine-fed rats compared to control rats (2.57±1.05 vs. 0.34±0.05 mg/dL, P<0.01), suggesting impaired renal function (i.e., adenine-induced CKD). We found that CKD animals exhibited augmentations in RSNA (Δ=153±75 vs. 61±50 %, P<0.05) and MAP (Δ=35±18 vs. 17±8 mmHg, P<0.05) in response to muscle contraction when compared to control animals. Importantly, the muscle tension developed during contraction was similar between the two groups (Δ=0.9±0.2 vs. 1.0±0.3 kg, P>0.1, CKD vs. control). During stimulation of the mechanoreflex, CKD rats also exhibited significantly greater RSNA (Δ=100±54 vs. 32±26 %, P<0.05) and MAP responses (Δ=25±14 vs. 10±7 mmHg, P<0.05) than control rats. The developed muscle tension during passive stretch was similar between the two groups (Δ=0.9±0.2 vs. 1.0±0.4 kg, P>0.1, CKD vs. control). There was a tendency for the responses to metaboreflex activation to be heightened in the CKD group compared with the control group, but the difference did not reach statistical significance (ΔRSNA=212±68 vs. 107±105 %, P=0.06, ΔMAP=67±12 vs. 48±21 mmHg, P=0.06, CKD vs. control, respectively). Our findings suggest that EPR function, particularly muscle mechanoreflex function, is exaggerated in CKD, leading to sympathetic activation and hypertensive responses during exercise. P30 DK079307 Subaward to H.K. and R01HL-133179 to W.V. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Assessment of Mitochondrial Function in a Mouse Model of Mild Chronic Kidney Disease Induced by High-Fat and High-Salt Diet

Intro: Kidneys are known for high energy demands involved in active transport and are thus highly oxidative organs, consuming the second-highest amount of oxygen per gram of tissue at rest (only exceeded by the heart). Chronic kidney disease (CKD) is a complex disorder that presents substantial challenges in understanding its pathophysiological mechanisms, including mitochondrial alterations. However, there are no established mouse models that recapitulate the CKD phenotype observed in humans.Hypothesis: We hypothesized that a high-fat, high-salt diet would induce a mild CKD phenotype and mitochondrial dysfunction in mice. Methods: We subjected C57Bl/6 mice to a high-fat (42%) and high-salt (8% NaCl) diet (HF/HNaCl) or standard chow diet for 16 weeks (n=4 per group). Additionally, we conducted comprehensive investigations into mitochondrial function, focusing on state 3 mitochondrial oxygen consumption (Oroboros O2K) and adenosine triphosphate (ATP) production (Horiba Fluoromax). Differences between groups were determined using Student’s t-tests. Results: HF/HNaCl feeding resulted in polyurea indicated by an increase in 24-hour urine output (Chow: 1.5 ± 0.2 mL; HF/HNaCl: 3.7 ± 0.8 mL; p=0.05) and a 30% reduction in glomerular filtration rate compared to chow-fed animals (Chow: 911.2 ± 107.8 μL/min/100g; Hf/HNaCl: 639.5 ± 25.9 μL/min/100g; p=0.08), indicative of the development of mild kidney disease. Although subtle changes were observed in mitochondrial oxygen consumption and ATP production, the alterations were not statistically significant. Discussion: Our findings suggest that the induced mild CKD state via the dietary regimen led to moderate renal impairment without substantial impacts on mitochondrial respiratory capacity and ATP synthesis. The establishment of this mouse model provides a valuable platform for further investigations into the complex interplay between renal dysfunction and mitochondrial dynamics in the context of mild CKD, offering insights that may pave the way for the development of targeted therapeutic interventions for this prevalent and debilitating condition. This project was supported by grants from the National Institutes of Health. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

PNPLA3 I148M Promotes Fatty Liver Disease While Preserving Cardiac Health

Metabolic-associated fatty liver disease (MAFLD) and cardiovascular disease (CVD) are commonly associated comorbidities. A common genetic variant in the PNPLA3 gene, rs738409 (I148M), is the greatest genetic risk factor for development and progression of MAFLD; however, MAFLD patients expressing PNPLA3 I148M display modest protection against coronary artery disease (CAD) and adverse cardiovascular events relative to wildtype carriers. Currently, the exact mechanisms by which PNPLA3 I148M causes MAFLD and preserves cardiac health are not well understood. Previous work suggests that the variant increases susceptibility to fatty liver disease by altering hepatic lipid metabolism, which may explain a potential mechanism for its cardioprotective effects. In order to investigate how PNPLA3 I148M might increase susceptibility to MAFLD while reducing risk of CVD we expressed either human wildtype (WT) PNPLA3 or PNPLA3 I148M as well as a GFP control specifically in the livers of PNPLA3 knockout mice. Our data demonstrate that hepatic expression of PNPLA3 I148M reduces secretion of VLDL TAGs from adipose tissue derived fatty acids. In agreement with prior investigations, mice expressing PNPLA3 I148M and fed a chow diet demonstrated significant increases in hepatic accumulation of neutral lipids (triglycerides & cholesterol esters) relative to WT and GFP expressing mice. Similarly, when fed a fatty liver promoting diet (D009100310) high in fructose, cholesterol, and saturated fats there remained a strong trend for greater liver to body weight ratios and hepatic TAGs in mice expressing the variant when compared to WT expressing mice (p=0.052 and p=0.071 respectively). Changes in hepatic lipid accumulation were not due to any alterations in insulin sensitivity, daily food consumption, energy expenditure or oxygen consumption between WT and I148M groups. Echocardiography revealed that hearts of mice expressing WT PNPLA3 had increases in left ventricular thickness (p=0.051) and left ventricle weights following dietary treatment that was not apparent in the I148M expressing mice. Moreover, there was a reduction in E/A ratios, a sensitive measure of diastolic functioning, in GFP and WT expressing mice post-treatment, that was not seen in the I148M mice. Overall, these findings indicate that PNPLA3 I148M promotes fatty liver, yet protects against diet-induced effects on ventricular remodeling and diastolic functioning. Our next steps will be to assess measures of atherosclerotic plaque formation around major blood vessels and investigate the metabolic pathways altered by PNPLA3 I148M. NIH R00 DK114471 NIH R01 DK126743 USDA grant no. 2021-09425 Pilot feasibility grant from University of Michigan: P30DK020572 Detroit Cardiovascular Training grant NIH 2T32HL120822. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Definition of the metabolic pattern of ANGPTL3 deficient mice on a chow diet and under dysmetabolic conditions

Aim: ANGPTL3 controls lipid and lipoprotein metabolism through lipoprotein lipase and endothelial lipase inhibition and the prevention of lipoprotein-derived triglycerides hydrolyzation. Here we present the metabolic profile of ANGPTL3 deficient mice in physiology and during the development of metabolic disorders. Methods: Angptl3 KO mice (C57BL6/J background) and their littermate controls (wild-type, WT) were fed a chow and a High Fat Diet (HFD, 60%kcal from lipids) for 16 weeks. During the diet protocol, changes in lipids and lipoprotein profile, under fast, fed, and fast-refeed setting were assessed. The metabolic phenotype was assessed, with a Glucose Tolerance Test (GTT) and an Insulin Tolerance Test (ITT); the lipids absorption profile was assessed with an Oral Lipid Tolerance Test (OLTT). Results: ANGPTL3 KO mice fed ad libitum a chow diet are hypolipidemic (plasma triglycerides levels: 42,42±8,80 mg/dL in ANGPTL3 KO mice compared to 122,02±55,09 mg/dL in WT mice; plasma cholesterol levels: 44,00±9,11 mg/dL in ANGPTL3 KO mice compared to 76,51±15,87 mg/dL in WT mice). After 16h fasting, ANGPTL3 KO mice on a chow diet are hypolipidemic and display small lipoproteins less rich in cholesterol and triglycerides, as established in humans, and the same holds true for mice fed a HFD diet. On HFD, ANGPTL3 KO mice gain less body weight, suggesting an improved metabolic profile compared to WT animals. The hypolipidemia is conserved during all the timepoints of OLTT, both in mice on chow or HFD, suggesting a different lipid management; in spite, no significant differences in the circulating glycaemia has been proved with a GTT after 16h of fasting; likewise, a similar sensitivity to insulin has been outlined with an ITT after 4h of fasting. Conclusions: This metabolic profiling of ANGPTL3 KO mice on chow diet or HFD highlights that these mice are hypolipidemic and may have beneficial metabolic features compared to controls.

Hepatocyte-Specific Fads1 Overexpression Attenuates Western Diet-Induced Metabolic Phenotypes in a Rat Model.

Fatty acid desaturase 1 (FADS1) is a rate-limiting enzyme in long-chain polyunsaturated fatty acid (LCPUFA) synthesis. Reduced activity of FADS1 was observed in metabolic dysfunction-associated steatotic liver disease (MASLD). The aim of this study was to determine whether adeno-associated virus serotype 8 (AAV8) mediated hepatocyte-specific overexpression of Fads1 (AAV8-Fads1) attenuates western diet-induced metabolic phenotypes in a rat model. Male weanling Sprague-Dawley rats were fed with a chow diet, or low-fat high-fructose (LFHFr) or high-fat high-fructose diet (HFHFr) ad libitum for 8 weeks. Metabolic phenotypes were evaluated at the endpoint. AAV8-Fads1 injection restored hepatic FADS1 protein levels in both LFHFr and HFHFr-fed rats. While AAV8-Fads1 injection led to improved glucose tolerance and insulin signaling in LFHFr-fed rats, it significantly reduced plasma triglyceride (by ~50%) and hepatic cholesterol levels (by ~25%) in HFHFr-fed rats. Hepatic lipidomics analysis showed that FADS1 activity was rescued by AAV8-FADS1 in HFHFr-fed rats, as shown by the restored arachidonic acid (AA)/dihomo-γ-linolenic acid (DGLA) ratio, and that was associated with reduced monounsaturated fatty acid (MUFA). Our data suggest that the beneficial role of AAV8-Fads1 is likely mediated by the inhibition of fatty acid re-esterification. FADS1 is a promising therapeutic target for MASLD in a diet-dependent manner.

Obesity-induced skeletal muscle remodeling: A comparative analysis of exercise training and ACE-inhibitory drug in male mice.

Obesity over-activates the classical arm of the renin-angiotensin system (RAS), impairing skeletal muscle remodeling. We aimed to compare the effect of exercise training and enalapril, an angiotensin-converting enzyme inhibitor, on RAS modulation in the skeletal muscle of obese animals. Thus, we divided C57BL/6 mice into two groups: standard chow (SC) and high-fat (HF) diet for 16 weeks. At the eighth week, the HF-fed animals were divided into four subgroups-sedentary (HF), treated with enalapril (HF-E), exercise training protocol (HF-T), and combined interventions (HF-ET). After 8 weeks of treatment, we evaluated body mass and index (BMI), body composition, exercise capacity, muscle morphology, and skeletal muscle molecular markers. All interventions resulted in lower BMI and attenuation of overactivation in the classical arm, while favoring the B2R in the bradykinin receptors profile. This was associated with reduced apoptosis markers in obese skeletal muscles. The HF-T group showed an increase in muscle mass and expression of biosynthesis markers and a reduction in expression of degradation markers and muscle fiber atrophy due to obesity. These findings suggest that the combination intervention did not have a synergistic effect against obesity-induced muscle remodeling. Additionally, the use of enalapril impaired muscle's physiological adaptations to exercise training.

Deletion of Impdh2 in adipocyte precursors limits the expansion of white adipose tissue and enhances metabolic health with overnutrition

The equilibrium between the hypertrophic growth of existing adipocytes and adipogenesis is vital in managing metabolic stability in white adipocytes when faced with overnutrition. Adipogenesis has been established as a key player in combating metabolic irregularities caused by various factors. However, the benefits of increasing adipogenesis-mediated white adipose tissue (WAT) expansion for metabolic health regulation remain uncertain. Our findings reveal an increase in Impdh2 expression during the adipogenesis phase, both in vivo and in vitro. Xmp enhances adipogenic potential by fostering mitotic clonal expansion (MCE). The conditional knockout of Impdh2 in adipocyte progenitor cells(APCs) in adult and aged mice effectively curbs white adipose tissue expansion, ameliorates glucose tolerance, and augments energy expenditure under high-fat diet (HFD). However, no significant difference is observed under normal chow diet (NCD). Concurrently, the knockout of Impdh2 in APCs significantly reduces the count of new adipocytes induced by HFD, without affecting adipocyte size. Mechanistically, Impdh2 regulates the proliferation of APCs during the MCE phase via Xmp. Exogenous Xmp can significantly offset the reduction in adipogenic abilities of APCs due to Impdh2 deficiency. In summary, we discovered that adipogenesis-mediated WAT expansion, induced by overnutrition, also contributes to metabolic abnormalities. Moreover, the pivotal role of Impdh2 in regulating adipogenesis in APCs offers a novel therapeutic approach to combat obesity.

Hairless (Hr) Deficiency Mitigates High-Fat Diet-Induced Obesity and Insulin Resistance in Mice.

Obesity is a significant global health concern linked to excessive dietary energy intake. This research focuses on the mammalian hairless protein (HR), known for its role in skin and hair function, and its impact on metabolism. Examining male wild-type (Hr+/+) and Hr null (Hr-/-) mice over a 14-week normal chow diet (NCD) or high-fat diet (HFD) intervention. This study reveals that HR deficiency exhibited a protective effect against HFD-induced obesity and insulin resistance. This protective effect is attributed to increased energy expenditure in Hr-/- mice. Moreover, the brown adipose tissue (BAT) of Hr-/- mice displays elevated levels of the thermogenic protein, uncoupling protein 1 (Ucp1), and its key transcriptional regulators (PPARγ and PGC1α), compared to Hr+/+ mice. In summary, the findings underscore the protective role of HR deficiency in countering HFD-induced adiposity by enhancing insulin sensitivity, raising energy expenditure, and augmenting thermogenic factors in BAT. Further exploration of HR metabolic regulation holds promise for potential therapeutic targets in addressing obesity-related metabolic disorders.

Probucol mitigates high-fat diet-induced cognitive and social impairments by regulating brain redox and insulin resistance.

Probucol has been utilized as a cholesterol-lowering drug with antioxidative properties. However, the impact and fundamental mechanisms of probucol in obesity-related cognitive decline are unclear. In this study, male C57BL/6J mice were allocated to a normal chow diet (NCD) group or a high-fat diet (HFD) group, followed by administration of probucol to half of the mice on the HFD regimen. Subsequently, the mice were subjected to a series of behavioral assessments, alongside the measurement of metabolic and redox parameters. Notably, probucol treatment effectively alleviates cognitive and social impairments induced by HFD in mice, while exhibiting no discernible influence on mood-related behaviors. Notably, the beneficial effects of probucol arise independently of rectifying obesity or restoring systemic glucose and lipid homeostasis, as evidenced by the lack of changes in body weight, serum cholesterol levels, blood glucose, hyperinsulinemia, systemic insulin resistance, and oxidative stress. Instead, probucol could regulate the levels of nitric oxide and superoxide-generating proteins, and it could specifically alleviate HFD-induced hippocampal insulin resistance. These findings shed light on the potential role of probucol in modulating obesity-related cognitive decline and urge reevaluation of the underlying mechanisms by which probucol exerts its beneficial effects.

High-fat diet elicits sex-based differences in liver inflammatory cytokines and redox homeostasis.

Sex differences in metabolic dysfunction-associated steatotic liver disease (MASLD) have been reported. Oxidative stress and inflammation are involved in the progression of MASLD. Thus, we aimed to evaluate liver redox homeostasis and inflammation in male and female rats fed a high-fat diet (HFD). Male and female Wistar rats were divided into the following groups: standard chow diet (SCD) or HFD during 12 weeks. HFD groups of both sexes had higher hepatocyte injury, with no differences between the sexes. Portal space liver inflammation was higher in females-HFD compared to females-SCD, whereas no differences were observed in males. Lobular inflammation and overall liver inflammation were higher in HFD groups, regardless of sex. TNF-α, IL-6, and IL-1β levels were higher in males-HFD compared to males-SCD, but no differences were observed in females. Catalase activity was higher in males compared to females, with no differences between the SCD and HFD groups of both sexes. Glutathione peroxidase activity was higher in females compared to males, with no differences between the SCD and HFD groups in both sexes. Lipid peroxidation was higher in female-SCD when compared to male-SCD, and in both male- and female-HFD compared to SCD groups. Furthermore, both cytoplasmic and nuclear NRF2 staining were lower in the HFD group compared to the SCD group in males. However, female-HFD exhibited reduced nuclear NRF2 staining compared to the female-SCD group. In conclusion, our study demonstrated that while both male and female rats developed metabolic dysfunction-associated steatohepatitis after 12 weeks of HFD, the alterations in inflammatory cytokines and redox balance were sexually dimorphic.

A Four-Week High-Fat Diet Induces Anxiolytic-like Behaviors through Mature BDNF in the mPFC of Mice.

The effect of a high-fat diet (HFD) on mood is a widely debated topic, with the underlying mechanisms being poorly understood. This study explores the anxiolytic effects of a four-week HFD in C57BL/6 mice. Five-week-old mice were exposed to either an HFD (60% calories from fat) or standard chow diet (CD) for four weeks, followed by cannula implantation, virus infusion, behavioral tests, and biochemical assays. Results revealed that four weeks of an HFD induced anxiolytic-like behaviors and increased the protein levels of mature brain-derived neurotrophic factor (mBDNF) and phosphorylated tyrosine kinase receptor B (p-TrkB) in the medial prefrontal cortex (mPFC). Administration of a BDNF-neutralizing antibody to the mPFC reversed HFD-induced anxiolytic-like behaviors. Elevated BDNF levels were observed in both neurons and astrocytes in the mPFC of HFD mice. Additionally, these mice exhibited a higher number of dendritic spines in the mPFC, as well as upregulation of postsynaptic density protein 95 (PSD95). Furthermore, mRNA levels of the N6-methyladenosine (m6A) demethylase, fat mass and obesity-associated protein (FTO), and the hydrolase matrix metalloproteinase-9 (MMP9), also increased in the mPFC. These findings suggest that an HFD may induce FTO and MMP9, which could potentially regulate BDNF processing, contributing to anxiolytic-like behaviors. This study proposes potential molecular mechanisms that may underlie HFD-induced anxiolytic behaviors.

Resveratrol relieves HFD-induced insulin resistance in skeletal muscle tissue through antioxidant capacity enhancement and the Nrf2-Keap1 signaling pathway.

Resveratrol has received much attention due to its beneficial effects including antioxidant activity. The purpose of this study was to investigate the therapeutic effects of resveratrol treatment on oxidative stress and insulin resistance in the skeletal muscle of high-fat diet (HFD)-fed animals. A total of 30 six-week-old C57BL/6J mice were randomly allocated to three groups (10 animals in each group): The control group in which mice were fed a normal chow diet (NCD); the HFD group in which mice were fed an HFD for 26 weeks; and the HFD-resveratrol group in which HFD was replaced by a resveratrol supplemented-HFD (400mg/kg diet) after 10 weeks of HFD feeding. At the end of this period, gastrocnemius muscle samples were examined to determine insulin resistance and the oxidative status in the presence of HFD and resveratrol. Resveratrol supplementation in HFD-fed mice reduced body and adipose tissue weight, improved insulin sensitivity, and decreased oxidative stress as indicated by lower malonaldehyde (MDA) levels and higher total antioxidant capacity. The supplement also increased the expression and activity of antioxidative enzymes in gastrocnemius muscle and modulated Nrf2 and Keap1 expression levels. These results suggest that resveratrol is effective in improving the antioxidant defense system of the skeletal muscle in HFD-fed mice, indicating its therapeutic potential to combat diseases associated with insulin resistance and oxidative stress.

Targeting Molecular Mechanisms of Obesity- and Type 2 Diabetes Mellitus-Induced Skeletal Muscle Atrophy with Nerve Growth Factor.

Skeletal muscle plays a critical role in metabolic diseases, such as obesity and type 2 diabetes mellitus (T2DM). Muscle atrophy, characterized by a decrease in muscle mass and function, occurs due to an imbalance between the rates of muscle protein synthesis and degradation. This study aimed to investigate the molecular mechanisms that lead to muscle atrophy in obese and T2DM mouse models. Additionally, the effect of nerve growth factor (NGF) on the protein synthesis and degradation pathways was examined. Male mice were divided into three groups: a control group that was fed a standard chow diet, and two experimental groups that were fed a Western diet. After 8 weeks, the diabetic group was injected with streptozotocin to induce T2DM. Each group was then further divided into NGF-treated or non-treated control group. In the gastrocnemius muscles of the Western diet group, increased expressions of myostatin, autophagy markers, and ubiquitin ligases were observed. Skeletal muscle tissue morphology indicated signs of muscle atrophy in both obese and diabetic mice. The NGF-treated group showed a prominent decrease in the protein levels of myostatin and autophagy markers. Furthermore, the NGF-treated group showed an increased Cyclin D1 level. Western diet-induced obesity and T2DM may be linked to muscle atrophy through upregulation of myostatin and subsequent increase in the ubiquitin and autophagy systems. Moreover, NGF treatment may improve muscle protein synthesis and cell cycling.

Role of liver FGF21-KLB signaling in ketogenic diet-induced amelioration of hepatic steatosis

BackgroundThe effectiveness of ketogenic diet (KD) in ameliorating fatty liver has been established, although its mechanism is under investigation. Fibroblast growth factor 21 (FGF21) positively regulates obesity-associated metabolic disorders and is elevated by KD. FGF21 conventionally initiates its intracellular signaling via receptor β-klotho (KLB). However, the mechanistic role of FGF21-KLB signaling for KD-ameliorated fatty liver remains unknown. This study aimed to delineate the critical role of FGF21 signaling in the ameliorative effects of KD on hepatic steatosis.MethodsEight-week-old C57BL/6 J mice were fed a chow diet (CD), a high-fat diet (HFD), or a KD for 16 weeks. Adeno-associated virus-mediated liver-specific KLB knockdown mice and control mice were fed a KD for 16 weeks. Phenotypic assessments were conducted during and after the intervention. We investigated the mechanism underlying KD-alleviated hepatic steatosis using multi-omics and validated the expression of key genes.ResultsKD improved hepatic steatosis by upregulating fatty acid oxidation and downregulating lipogenesis. Transcriptional analysis revealed that KD dramatically activated FGF21 pathway, including KLB and fibroblast growth factor receptor 1 (FGFR1). Impairing liver FGF21 signaling via KLB knockdown diminished the beneficial effects of KD on ameliorating fatty liver, insulin resistance, and regulating lipid metabolism.ConclusionKD demonstrates beneficial effects on diet-induced metabolic disorders, particularly on hepatic steatosis. Liver FGF21-KLB signaling plays a critical role in the KD-induced amelioration of hepatic steatosis.

Multiple metabolic signals in the CeA regulate feeding: The role of AMPK

BackgroundThe central nucleus of the amygdala (CeA) is part of the dopaminergic reward system and controls energy balance. Recently, a cluster of neurons was identified as responsive to the orexigenic effect of ghrelin and fasting. However, the signaling pathway by which ghrelin and fasting induce feeding is unknown. AMP-activated protein kinase (AMPK) is a cellular energy sensor, and its Thr172 phosphorylation (AMPKThr172) in the mediobasal hypothalamus regulates food intake. However, whether the expression and activation of AMPK in CeA could be one of the intracellular signaling activated in response to ghrelin and fasting eliciting food intake is unknown. AimTo evaluate the activation of AMPK into CeA in response to ghrelin, fasting, and 2-deoxy-D-glucose (2DG) and whether feeding accompanied these changes. In addition, to investigate whether the inhibition of AMPK into CeA could decrease food intake. MethodsOn a chow diet, eight-week-old Wistar male rats were stereotaxically implanted with a cannula in the CeA to inject several modulators of AMPKα1/2Thr172 phosphorylation, and we performed physiological and molecular assays. Key findingsFasting increased, and refeeding reduced AMPKThr172 in the CeA. Intra-CeA glucose injection decreased feeding, whereas injection of 2DG, a glucoprivation inductor, in the CeA, increased food intake and blood glucose, despite faint increases in AMPKThr172. Intra-CeA ghrelin injection increased food intake and AMPKThr172. To further confirm the role of AMPK in the CeA, chronic injection of Melanotan II (MTII) in CeA reduced body mass and food intake over seven days together with a slight decrease in AMPKThr172. SignificanceOur findings identified that AMPK might be part of the signaling machinery in the CeA, which responds to nutrients and hormones contributing to feeding control. The results can contribute to understanding the pathophysiological mechanisms of altered feeding behavior/consumption, such as binge eating of caloric-dense, palatable food.

Role of HNF4α-cMyc Interaction in CDE Diet–Induced Liver Injury and Regeneration

Hepatocyte nuclear factor 4 alpha (HNF4α) is a nuclear factor essential for liver function that regulates the expression of cMyc and plays an important role during liver regeneration. This study investigated the role of the HNF4α-cMyc interaction in regulating liver injury and regeneration using the choline-deficient and ethionine-supplemented (CDE) diet model. Wild-type (WT), hepatocyte-specific HNF4α-knockout (KO), cMyc-KO, and HNF4α-cMyc double KO (DKO) mice were fed a CDE diet for 1 week to induce subacute liver injury. To study regeneration, normal chow diet was fed for 1 week after CDE diet. WT mice exhibited significant liver injury and decreased HNF4α mRNA and protein expression after CDE diet. HNF4α deletion resulted in significantly higher injury with increased inflammation, fibrosis, proliferation, and hepatic progenitor cell activation compared with WT mice after CDE diet but indicated similar recovery. Deletion of cMyc lowered liver injury with activation of inflammatory genes compared with WT and HNF4α-KO mice after CDE diet. DKO mice had a phenotype comparable to that of the HNF4α-KO mice after CDE diet and a complete recovery. DKO mice exhibited a significant increase in hepatic progenitor cell markers both after injury and recovery phase. Taken together, these data show that HNF4α protects against inflammatory and fibrotic changes after CDE diet-induced injury, which is driven by cMyc.