Caloric Restriction Research Articles

Fasting is required for many of the benefits of calorie restriction in the 3xTg mouse model of Alzheimer's disease.

Caloric restriction (CR) is a widely recognized geroprotective intervention that slows or prevents Alzheimer's disease (AD) in animal models. CR is typically implemented via feeding mice a single meal per day; as CR mice rapidly consume their food, they are subject to a prolonged fast between meals. While CR has been shown to improve metabolic and cognitive functions and suppress pathological markers in AD mouse models, the specific contributions of fasting versus calorie reduction remains unclear. Here, we investigated the contribution of fasting and energy restriction to the beneficial effects of CR on AD progression. To test this, we placed 6-month-old 3xTg mice on one of several diet regimens, allowing us to dissect the effects of calories and fasting on metabolism, AD pathology, and cognition. We find that energy restriction alone, without fasting, was sufficient to improve glucose tolerance and reduce adiposity in both sexes, and to reduce Aβ plaques and improve aspects of cognitive performance in females. However, we find that a prolonged fast between meals is necessary for many of the benefits of CR, including improved insulin sensitivity, reduced phosphorylation of tau, decreased neuroinflammation, inhibition of mTORC1 signaling, and activation of autophagy, as well as for the full cognitive benefits of CR. Finally, we find that fasting is essential for the benefits of CR on survival in male 3xTg mice. Overall, our results demonstrate that fasting is required for the full benefits of a CR diet on the development and progression of AD in 3xTg mice, and suggest that both when and how much we eat influences the development and progress of AD.

Caloric Restriction Diet Attenuates Systemic Bone Fragility after Radiotherapy.

Bone fragility is a well-documented long-term side effect of radiotherapy, which currently has no preventative treatments. In this study, we applied a caloric restriction (CR) diet to attenuate both local and systemic bone loss after irradiation (RTx) in an established female Balb/c mouse model (4 consecutive daily doses of 5 Gy to the right hindlimb only). CR mice were tapered down to a 30% reduced calorie diet (RTx/CR) one week before irradiation, while regular diet (RD) mice received food ad libitum (RTx/RD). Unirradiated (sham) mice received either a 30% CR diet (SH/CR) or received food ad libitum (SH/RD). Irradiated, contralateral, and unirradiated hindlimbs were evaluated at 2, 4, and 8 weeks postirradiation using micro-computed tomography (μCT) to assess bone morphology and 3-point bending to quantify femur strength. Histological analysis of irradiated and unirradiated tibiae was performed to examine general bone tissue cytology and serum biomarker analysis was performed using terminal blood draw samples. After treatment, femur strength and metaphyseal bone quantity was decreased in irradiated and contralateral femora of RTx/RD mice compared to SH/RD femurs; this finding is consistent with previous studies. RTx/CR mice had positive effects when compared to RTx/RD mice, including increased strength relative to body mass in both the irradiated and contralateral limb, increased trabecular bone mass, and decreased marrow adiposity. However, a number of adverse effects were also observed, including a significant decrease in body mass and decreased cortical bone. Overall, CR shows promise as a preventative treatment for postirradiated bone fragility, yet questions remain to be addressed in future studies. Ideal diet duration, impact to normal tissue, and mechanism of action must be explored to better understand the clinical implication of a CR diet.

Effects of Intermittent Fasting on Weight Loss and Metabolic Health

Introduction and Purpose: Intermittent fasting (IF) has become a popular strategy for combating obesity and improving metabolic health. This dietary regimen alternates between periods of fasting and eating, aiming to enhance cellular health and increase longevity. With obesity rates doubling globally since 1990 and metabolic diseases on the rise, IF offers a potential solution by promoting metabolic benefits and reducing obesity-related conditions. Material and Method: This review examines various IF methods, including alternate-day fasting, the 5:2 diet, and time-restricted eating. The analysis focuses on the impact of these fasting methods on body weight, insulin sensitivity, and lipid profiles, based on a compilation of studies that explore the physiological effects and health outcomes associated with IF. Results: IF has shown to be effective in reducing body weight and improving metabolic parameters. Studies indicate significant benefits in insulin sensitivity and lipid profiles, with some variations across different IF protocols. Physiological insights reveal that IF leads to a metabolic switch from glucose-based to ketone-based energy, which plays a critical role in its effectiveness. Conclusions: Intermittent fasting appears to be a viable alternative to continuous calorie restriction for weight loss and metabolic enhancement. It not only aids in weight management but also offers additional health benefits such as improved insulin sensitivity and better lipid profiles. However, more long-term studies are needed to fully understand its benefits and potential risks. Future research should focus on optimizing fasting protocols and exploring their long-term effects on health and disease.

Green Tea Kombucha Impacts Inflammation and Salivary Microbiota in Individuals with Excess Body Weight: A Randomized Controlled Trial.

Green tea kombucha (GTK) is a fermented beverage with promising health benefits, but few studies proved its impact on human health. Thus, we aimed to investigate the impact of GTK on weight loss, inflammation, and salivary microbiota in individuals with excess body weight. This is a randomized controlled clinical trial that lasted 10 weeks with two groups of individuals with excess body weight: control (CG; n = 29; caloric restriction) and kombucha (KG; n = 30; caloric restriction + 200 mL GTK). Body composition, anthropometry, saliva, and blood collection were performed in the beginning and end of the intervention. Plasma interleukins were determined by flow cytometry. Salivary microbiota was analyzed by 16S rRNA sequencing. Both groups decreased weight, BMI, and body fat (p < 0.001) after the intervention, but there were no differences between groups. The KG reduced lipid accumulation product (LAP) (p = 0.029). Both groups decreased IL-1β and IL-8, but IL-6 increased in the CG (p = 0.023) compared to the kombucha group. Alpha and beta diversity of salivary microbiota increased in the KG. Moreover, the KG presented lower Bacillota/Bacteroidota ratio (p = 0.028), and BMI was positively associated with the Bacillota phylum. GTK did not enhance weight loss, but it decreased the LAP. GTK helped in the inflammatory profile and induced positive changes in oral microbiota composition.

Calorie restriction and rapamycin distinctly restore non-canonical ORF translation in the muscles of aging mice

Loss of protein homeostasis is one of the hallmarks of aging. As such, interventions that restore proteostasis should slow down the aging process and improve healthspan. Two of the most broadly used anti-aging interventions that are effective in organisms from yeast to mammals are calorie restriction (CR) and rapamycin (RM) treatment. To identify the regulatory mechanisms by which these interventions improve the protein homeostasis, we carried out ribosome footprinting in the muscle of mice aged under standard conditions, or under long-term treatment with CR or RM. We found that the treatments distinctly impact the non-canonical translation, RM primarily remodeling the translation of upstream open reading frames (uORFs), while CR restores stop codon readthrough and the translation of downstream ORFs. Proteomics analysis revealed the expression of numerous non-canonical ORFs at the protein level. The corresponding peptides may provide entry points for therapies aiming to maintain muscle function and extend health span.

Exploring the internal medicine comorbidities associated with eating disorders: correlation between disease severity and cardiac abnormalities in adolescent patients with anorexia nervosa

ABSTRACT Anorexia Nervosa (AN) is a psychiatric disorder characterized by caloric restriction, weight loss, and fear of gaining weight. Cardiac complications are among the most severe medical consequences. Despite the importance of regular cardiac assessments, there is a lack of standardized protocols for timing and patient selection. This retrospective cohort study has aimed to assess the correlation between AN severity, Body Mass Index, weight loss percentage, and cardiac abnormalities in pediatric patients. A total of 123 patients admitted to a child and adolescent psychiatry unit between January 2019 and March 2022 were included. Data on demographics, clinical characteristics, cardiac evaluations were collected from electronic health records. The study revealed a prevalence of cardiac abnormalities in 57.7% of patients, with bradycardia being the most common (49.5%), followed by QTc prolongation (4%) and pericardial effusion (4%). However, no significant correlation was found between AN severity and cardiac alterations, suggesting that disease severity alone is not a reliable predictor of cardiac risk. The study highlights the need for individualized risk assessment and targeted cardiac evaluations based on specific risk factors rather than disease severity alone. Early diagnosis and comprehensive care contribute to better outcomes, emphasizing the importance of multidisciplinary approaches in managing AN.

Fueling the Heart: What Are the Optimal Dietary Strategies in Heart Failure?

Heart failure (HF) is a global health concern with rising incidence and poor prognosis. While the essential role of nutritional and dietary strategies in HF patients is acknowledged in the existing scientific guidelines and clinical practice, there are no comprehensive nutritional recommendations for optimal dietary management of HF. In this review, we discuss results from recent studies on the obesity paradox and the effects of calorie restriction and weight loss, intermittent fasting, the Western diet, the Mediterranean diet, the ketogenic diet, and the DASH diet on HF progression. Many of these strategies remain under clinical and basic investigation for their safety and efficacy, and there is considerable heterogeneity in the observed response, presumably because of heterogeneity in the pathogenesis of different types of HF. In addition, while specific aspects of cardiac metabolism, such as changes in ketone body utilization, might underlie the effects of certain dietary strategies on the heart, there is a critical divide between supplement strategies (i.e., with ketones) and dietary strategies that impact ketogenesis. This review aims to highlight this gap by exploring emerging evidence supporting the importance of personalized dietary strategies in preventing progression and improving outcomes in the context of HF.

Effects of intermittent fasting and caloric restriction on inflammatory biomarkers in individuals with obesity/overweight: A systematic review and meta-analysis of randomized controlled trials.

Obesity is characterized by chronic low-grade inflammation. This study presents an updated systematic review and meta-analysis on the effect of caloric restriction (CR) and intermittent fasting (IF) on plasma inflammatory biomarkers (C-reactive protein [CRP], tumor necrosis factor [TNF]-alpha, and interleukin [IL]-6) in individuals with obesity/overweight compared with unrestricted or ad libitum feeding. PubMed, Web of Science, and SCOPUS databases were searched for randomized controlled trials (RCTs) reporting inflammatory biomarkers after at least 8 weeks of intervention. Standardized mean differences (SMDs) were calculated using a fixed effect model. Heterogeneity was determined using I2 statistics. Sensitivity analysis was conducted using the "leave-one-out" approach. Relatively few RCTs have investigated the effect of IF on inflammatory biomarkers than with CR (6 vs. 15). Analysis of pooled data showed that CR was associated with a significant reduction in CRP with low heterogeneity (SMD -0.15 mg/L [95% CI -0.30 to -0.00], p = 0.04; I2= 0%, p = 0.69) and IL-6 with high heterogeneity (SMD -0.31 pg/mL [95% CI -0.51 to -0.10], p = 0.004; I2= 73%, p = 0.001). IF was associated with a significant decrease in TNF-alpha with moderate heterogeneity (SMD -0.32 pg/mL [95% CI -0.63 to -0.02], p = 0.04; I2= 44%, p = 0.13). No associations were detected between IF and CRP or IL-6 and CR and TNF-alpha. CR may be more effective in reducing chronic low-grade inflammation than IF. However, there were some concerns regarding the included studies' randomization and allocation sequence concealment process.

Calorie restriction increases the sensitivity of progeroid Ercc1Δ/- mice to acute (neuro)inflammation.

Hospitalized elderly patients frequently suffer from delirium, especially in the context of sepsis-associated encephalopathy. Current treatments of delirium are merely symptomatic. Calorie restriction (CR) is both a promising strategy to protect against sepsis and has beneficial effects on aging-induced neurodegeneration. In this study, we investigated whether six weeks of 30% CR had protective effects on lipopolysaccharide (LPS) induced (neuro)inflammation in wild-type (WT) and progeroid mice deficient in the DNA excision-repair gene Ercc1 (Ercc1Δ/-). While CR did not affect the LPS-induced inflammatory response in WT mice, CR exaggerated the peripheral inflammatory response in Ercc1Δ/- mice, as evidenced by an increase of pro-inflammatory serum cytokines (TNF-α, IL-1β, and IFN-γ) and kidney injury marker Ngal. Neuroinflammatory effects were assessed by RNA-sequencing of isolated microglia. Similarly, CR did not affect microglia gene expression in WT mice, but increased neuroinflammation-associated gene expression in Ercc1Δ/- mice. In conclusion, CR increases the peripheral and brain inflammatory response of Ercc1Δ/- mice to a systemic inflammatory stimulus.

The Bone, Exercise, Alendronate, and Caloric Restriction (BEACON) trial design and methods

BackgroundAmong older adults living with obesity, intentional weight loss (WL) improves prognosis of many comorbidities. However, concomitant decline in bone mineral density (BMD) limits overall benefit of WL by increasing osteoporotic fracture risk. Identification of intervention strategies to maximize body fat loss, while minimizing harm to the musculoskeletal system, is an important area of clinical research. The main objective of the Bone, Exercise, Alendronate, and Caloric Restriction (BEACON) trial (NCT05764733) is to compare the independent and combined effects of a 12-month intervention of resistance training (RT) plus bone-loading exercises and bisphosphonate use on dietary WL-associated bone loss among 308 older (≥60 years) adults living with an indication for WL and bisphosphonate use. MethodsAll participants will receive the same group-mediated dietary intervention targeting 8–10 % WL and be randomized to one of four groups: no RT and placebo capsules (NoRT+PL); progressive RT plus bone-loading exercises and placebo capsules (RT++PL); no RT and oral bisphosphonate (70 mg weekly oral alendronate; NoRT+BIS); or progressive RT plus bone-loading exercises and oral bisphosphonate (RT++BIS). Total hip areal (a)BMD measured via dual-energy x-ray absorptiometry (DXA) is the primary, powered study outcome. Secondary skeletal outcome measures include femoral neck and lumbar spine aBMD, high resolution peripheral quantitative computed tomography (HRpQCT) bone assessments of the radius and tibia, and biomarkers of bone turnover. DiscussionBEACON will address an understudied, yet important, clinical research question by studying the independent and combined effects of two scalable intervention strategies aimed at optimizing skeletal integrity in older adults undergoing WL.Clinical Trials Registration: NCT05764733

An evidence-based assessment of the nutritional recommendations for thepreventionof diabetes mellitus.

Thissystematic review presents the most recent scientific knowledge concerningdietary recommendations for T2DM published in the English language by various scientific societies during the past 10years. The recommendations are herein presented and discussed in the light of a critical, evidence-based appraisal aiming to provide a comprehensive guide for the clinician in daily practice. In the case of overweight or obesity, the cornerstone of the primary prevention of T2DM is the combination of a healthy body weight (body mass index < 25kg/m2) or a reduction of fat byat least 7% and the implementation of at least 150min of moderate physical activity per week. Restriction of calories and of dietary fat is recommended, the latter as well as several dietary patterns providing a holistic approach to dieting andall havingbeen correlated with decreased risk of T2DM. Among these dietary patterns are the Mediterranean diet, the DASH diet (Dietary Approaches to Stop Hypertension), the low-glycemic diet, and the HEI-Healthy Eating Index and AHEI-Alternative Healthy Eating Index. Micronutrient deficiencies of, for example, vitamin D, chromium and magnesium, may be associated with insulin resistance in T2DM. Overall, the combination of nutrition through dietary patterns that are mainly plant-based and which emphasize wholegrains, legumes, nuts, fruits, and vegetables and that include only small percentages of refined and processed foods, together with physical activity, has been associated with decreased T2DM risk.

The Link between Salivary Amylase Activity, Overweight, and Glucose Homeostasis.

Butyrate, a short-chain fatty acid (SCFA) produced by the fermentation of dietary fibers in the colon, plays a pivotal role in regulating metabolic health, particularly by enhancing insulin sensitivity. Given the rising incidence of metabolic disorders, understanding the factors that influence butyrate production is of significant interest. This study explores the link between salivary amylase activity and butyrate levels in overweight women of reproductive age. Participants were categorized into low (LSA) and high (HSA) salivary amylase activity groups and further divided into two subgroups: one followed a low-starch diet (LS), and the other underwent caloric restriction (CR). We assessed salivary amylase activity and measured serum butyrate concentrations to examine their associations. Our findings showed a significant, though weak, positive correlation (ρ = 0.0486, p < 0.05), suggesting a link between salivary amylase activity and butyrate levels. The statistical significance, despite the weak correlation, implies that this relationship is not random. Moreover, higher baseline butyrate levels were observed in women with elevated salivary amylase activity. Also, women with low salivary amylase activity on a low-starch diet experienced a more pronounced increase in butyrate levels compared to those on caloric restriction. These results suggest that salivary amylase activity and dietary intake interact to influence butyrate production, with potential implications for improving insulin sensitivity and metabolic health. The study underscores the potential of butyrate in enhancing insulin sensitivity and promoting overall metabolic well-being. Further research is necessary to clarify the mechanisms involved and to understand the long-term effects of butyrate on metabolic health across different populations.

Lead-in calorie restriction enhances the weight-lowering efficacy of incretin hormone-based pharmacotherapies in mice

ObjectivesThe potential benefits of combining lifestyle changes with weight loss pharmacotherapies for obesity treatment are underexplored. Building on recent clinical observations, this study aimed to determine whether “lead-in” calorie restriction before administering clinically approved weight loss medications enhances the maximum achievable weight loss in preclinical models. MethodsDiet-induced obese mice (DIO) were exposed to 7 or 14 days of calorie restriction before initiating treatment with semaglutide (a glucagon-like peptide-1 receptor (GLP-1R) agonist), tirzepatide (a GLP-1R/glucose insulinotropic peptide receptor (GIPR) co-agonist), or setmelanotide (a melanocortin-4 receptor (MC4R) agonist). Follow-up assessments using indirect calorimetry determined the contributions of energy intake and expenditure linked to consecutive exposure to dieting followed by pharmacotherapy. ResultsCalorie restriction prior to treatment with semaglutide or tirzepatide enhanced the weight loss magnitude of both incretin-based therapies in DIO mice, reflected by a reduction in fat mass and linked to reduced energy intake and a less pronounced adaptive drop in energy expenditure. These benefits were not observed with the MC4R agonist, setmelanotide. ConclusionsOur findings provide compelling evidence that calorie restriction prior to incretin-based therapy enhances the achievable extent of weight loss, as reflected in a weight loss plateau at a lower level compared to that of treatment without prior calorie reduction. This work suggests that more intensive lifestyle interventions should be considered prior to pharmacological treatment, encouraging further exploration and discussion of the current standard of care.

Myths and facts of anti-ageing medicine

The anti-aging industry treats the body like a glass with evaporating liquid that needs replacement. We inject hormones to counteract hormonal deficiency. We forget that hormones must be in the optimal range to be functional. More is not better. Then we inject stem cells to replenish the body’s decline. We forget about immunorejection or tumorigenesis. We perform these treatments without longitudinal research that confirms the compatibility of specific individuals with the injected hormones or stem cells in their bodies. Marketing touts “virtually instant results” and “magically reversing aging,” but more often than not, truth and marketing are incompatible. Inflammation is generally considered to be one of the main reasons for ageing, along with increased toxicity and oxidative damage. Energy devices, stem cells or hormone injections must provide us with 10-15 years of longitudinal research that investigates the long-term results of these procedures by examining several inflammatory variables and other health factors, before touting their safety and efficacy. Anti-ageing should focus on cellular repair without interfering with or traumatising the body. We should capitalize on effective health-enhancing interventions like caloric restriction, novel exercise methods, nutrition, lifestyle and other alternative medicine modalities that can reduce age-accumulated toxicity and inflammation to reinforce immunity and delay aging.

Diabetic Kidney Disease: Contribution of Phenyl Sulfate Derived from Dietary Tyrosine upon Gut Microbiota Catabolism.

Deranged gut microbiota can release increased levels of uremic toxins leading to exacerbated kidney injury. In diabetic kidney disease (DKD), phenyl sulfate (PS) derived from tyrosine catabolism by gut microbiota has been demonstrated to be both an early diagnostic marker and a therapeutic target. In this perspective article, we summarize PS generation pathways and recent findings on PS and kidney injury in DKD. Increasing evidence has shown that the underlying mechanisms of PS-induced kidney injury mainly involve oxidative stress, redox imbalance, and mitochondrial dysfunction, which all may be targeted to attenuate PS-induced kidney injury. For future research directions, we think that a deeper understanding of the pathogenic role of PS in kidney injury using a variety of diabetic animal models should be investigated. Moreover, we also suggest beneficial approaches that could be used to mitigate the deleterious effect of PS on the kidney. These approaches include caloric restriction, tyrosine restriction, and administration of ketogenic drugs, ketogenic diets or natural products; all of which should be conducted under obese and diabetic conditions.

Mitigating the effects of time in the heart and liver: The variable effects of short- and long-term caloric restriction

Caloric restriction (CR) is known for its anti-aging benefits, partly due to reduced oxidative stress and enhanced antioxidant defense. However, CR outcomes vary based on its intensity, timing, and duration. This study explored CR's effects on antioxidant activity in the heart and liver of male Wistar rats during aging. We investigated two CR paradigms: long-term CR (LTCR), started early in life, and short-term CR (STCR), initiated in middle or old age for 3 months. Contrary to previous findings of short-term CR deleterious effects of on the nervous system, our results revealed increased levels of key antioxidants after STCR. More specifically, we found an increase in GSH-Px and GSH under STCR that was particularly pronounced in the liver, while an increase in CAT and GR activities was observed in the heart of the STCR groups. Catalase was characterized as an enzyme particularly responsive to CR, as its activity was also increased in both the liver and heart after long-term caloric restriction. Our results highlight a significant tissue-specific response to CR and contribute to our understanding of the dynamic effects of CR, which in turn has implications for refining its therapeutic potential in combating age-related decline.

The role of dietary modification in the prevention and management of metabolic dysfunction-associated fatty liver disease: An international multidisciplinary expert consensus

Metabolic dysfunction-associated fatty liver disease (MAFLD) or metabolic dysfunction-associated steatotic liver disease (MASLD), has become the leading cause of chronic liver disease worldwide. Optimal dietary intervention strategies for MAFLD are not standardized. This study aimed to achieve consensus on prevention of MAFLD through dietary modification. A multidisciplinary panel of 55 international experts, including specialists in hepatology, gastroenterology, dietetics, endocrinology and other medical specialties from six continents collaborated in a Delphi-based consensus development process. The consensus statements covered aspects ranging from epidemiology to mechanisms, management, and dietary recommendations for MAFLD. The recommended dietary strategies emphasize adherence to a balanced diet with controlled energy intake and personalized nutritional interventions, such as calorie restriction, high-protein, or low-carbohydrate diets. Specific dietary advice encouraged increasing the consumption of whole grains, plant-based proteins, fish, seafood, low-fat or fat-free dairy products, liquid plant oils, and deeply colored fruits and vegetables. Concurrently, it advised reducing the intake of red and processed meats, saturated and trans fats, ultra-processed foods, added sugars, and alcohol. Additionally, maintaining the Mediterranean or DASH diet, minimizing sedentary behavior, and engaging in regular physical activity are recommended. These consensus statements lay the foundation for customized dietary guidelines and proposing avenues for further research on nutrition and MAFLD.

Effects of Different Caloric Restriction Patterns on Blood Pressure and Other Cardiovascular Risk Factors: A Systematic Review and Network Meta-Analysis of Randomized Trials.

All types of caloric restriction are preventive against cardiovascular risk factors, but the best restriction method and most affected factors have not been identified. The objective of this study was to explore the effects of different caloric restriction methods on various cardiovascular risk factors by horizontally comparing program advantages and disadvantages via network meta-analysis. The PubMed, Web of Science, Cochrane Library, and Embase literature databases were searched (October 2013 to October 2023). Eligible randomized controlled trials involving participants who underwent caloric restriction and systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), and high-density lipoprotein (HDL) cholesterol level measurements were included. Thirty-six of 13 208 records (0.27%) were included. Two researchers reviewed the articles, extracted data, and assessed article quality. Alternate-day fasting (ADF) reduced SBP (4.88 mmHg; CI, 2.06-7.15) and DBP (5.10 mmHg; CI, 2.44-7.76). Time-restricted eating reduced SBP (2.46 mmHg; CI, 0.16-4.76) but not DBP. Continuous energy restriction (CER) significantly reduced BMI (1.11 kg/m2; CI = 0.16, 2.06) and waist circumference (3.28 cm; CI, 0.62-5.94). This meta-analysis confirmed the preventive effect of CER and ADF on various cardiovascular risk factors. Additionally, CER is more likely to reduce obesity, and ADF is more likely to reduce blood pressure (BP). Based on this meta-analysis, CER is recommended to control obesity only for people who are obese and do not have elevated BP or other abnormal indicators. Additionally, ADF for early control or prevention is recommended for patients who have abnormal BP or other cardiovascular risk factors. PROSPERO registration no. CRD42023455889.

The cell rejuvenation atlas: leveraging network biology to identify master regulators of rejuvenation strategies.

Current rejuvenation strategies, which range from calorie restriction to in vivo partial reprogramming, only improve a few specific cellular processes. In addition, the molecular mechanisms underlying these approaches are largely unknown, which hinders the design of more holistic cellular rejuvenation strategies. To address this issue, we developed SINGULAR (Single-cell RNA-seq Investigation of Rejuvenation Agents and Longevity), a cell rejuvenation atlas that provides a unified system biology analysis of diverse rejuvenation strategies across multiple organs at single-cell resolution. In particular, we leverage network biology approaches to characterize and compare the effects of each strategy at the level of intracellular signaling, cell-cell communication, and transcriptional regulation. As a result, we identified master regulators orchestrating the rejuvenation response and propose that targeting a combination of them leads to a more holistic improvement of age-dysregulated cellular processes. Thus, the interactive database accompanying SINGULAR is expected to facilitate the future design of synthetic rejuvenation interventions.

Calorie restriction exacerbates folic acid-induced kidney fibrosis by altering mitochondria metabolism

Calorie restriction (CR) is known to confer health benefits, including longevity and disease prevention. Although CR is promising in preventing chronic kidney disease (CKD), its potential impact on the progression of kidney fibrosis from acute kidney injury (AKI) to CKD remains unclear. Here, we present evidence that CR exacerbates renal damage in a mouse model of folic acid (FA)-induced renal fibrosis by altering mitochondrial metabolism and inflammation. Mice subjected to CR (60% of ad libitum) for three days were subjected to high dose of FA (250 mg/kg) injection and maintained under CR for an additional week before being sacrificed. Biochemical analyses showed that CR mice exhibited increased kidney injury and fibrosis. RNA sequencing analysis demonstrated decreased electron transport and oxidative phosphorylation (OXPHOS) in CR kidneys with injury, heightened inflammatory, and fibrotic responses. CR significantly decreased OXPHOS gene and protein levels and reduced β-oxidation-associated proteins in the kidney. To determine whether defects in mitochondrial metabolism is associated with inflammation in the kidney, further in vitro experiments were performed. NRK52E kidney epithelial cells were treated with antimycin A to induce mitochondrial damage. Antimycin A treatment significantly increased chemokine expression via a STING-dependent pathway. Serum restriction in NRK49F kidney fibroblasts was observed to enhance the fibrotic response induced by TGFβ under in vitro conditions. In summary, our results indicate that CR exacerbates fibrosis and inflammatory responses in the kidney by altering mitochondrial metabolism, highlighting the importance of adequate energy supply for an effective response to AKI and fibrosis development.