Dose effects of modified alternate-day fasting regimens on in vivo cell proliferation and plasma insulin-like growth factor-1 in mice

Prolonged water-only fasting in the management of low-grade follicular lymphoma: a case series

BACKGROUND

Follicular lymphoma typically follows an indolent and relapsing course often requiring several treatment cycles to achieve remission. Some patients opt to use complementary and alternative therapies particularly when observation is a treatment option.

CASE PRESENTATION

Here we present a case series of three patients, a 50-year-old, White, Hispanic female, 56-year-old, White, non-Hispanic male, and 49-year-old, White, non-Hispanic male, who elected to undergo one or more prolonged water-only fasting and refeeding interventions to manage low to intermediate grade follicular lymphoma. Fasting was well tolerated in each patient. Each patient also experienced a reduction in the size and avidity of hypermetabolic lymph nodes as independently determined by their respective oncologists.

CONCLUSION

The reported cases demonstrate positive outcomes in low-grade follicular lymphoma coinciding with prolonged water-only fasting and exclusively whole-plant-food dietary interventions. These findings highlight the potential of such interventions and warrant further exploration through preliminary observational research.

Unlocking the Benefits of Fasting: A Review of its Impact on Various Biological Systems and Human Health

Fasting has gained significant attention in recent years for its potential health benefits in various body systems. This review aims to comprehensively examine the effects of fasting on human health, specifically focusing on its impact on different body's physiological systems. The cardiovascular system plays a vital role in maintaining overall health, and fasting has shown promising effects in improving cardiovascular health markers such as blood pressure, cholesterol levels, and triglyceride levels. Additionally, fasting has been suggested to enhance insulin sensitivity, promote weight loss, and improve metabolic health, thus offering potential benefits to individuals with diabetes and metabolic disorders. Furthermore, fasting can boost immune function, reduce inflammation, enhance autophagy, and support the body's defense against infections, cancer, and autoimmune diseases. Fasting has also demonstrated a positive effect on the brain and nervous system. It has been associated with neuroprotective properties, improving cognitive function, and reducing the risk of neurodegenerative diseases, besides the ability of increasing the lifespan. Hence, understanding the potential advantages of fasting can provide valuable insights for individuals and healthcare professionals alike in promoting health and wellbeing. The data presented here may have significant implications for the development of therapeutic approaches and interventions using fasting as a potential preventive and therapeutic strategy.

The Effect of Moderate-Intensity Physical Exercise on Some Serum Inflammation Markers and the Immune System in Rats Fed Intermittent Fasting with a High-Fat Diet

Background and Objectives: This study aimed to investigate the impact of moderate-intensity physical exercise on serum inflammation markers and the immune system in rats that were fed a high-fat diet (HFD) with intermittent fasting. Materials and Methods: A total of 48 Wistar albino male rats were included in the study and divided into eight groups, each consisting of six rats. Group 1 served as the control group (CG), receiving a standard diet. Group 2 followed the standard nutrition program with intermittent fasting (CG + IF). Group 3 underwent exercise with a standard diet (CG + E). Group 4 underwent both a standard diet with intermittent fasting and exercise (CG + IF + E). Group 5 was fed a high-fat diet (HFD). Group 6 received a high-fat diet with intermittent fasting (HFD + IF). Group 7 followed a high-fat diet with exercise (HFD + E). Group 8 underwent both a high-fat diet with intermittent fasting and exercise (HFD + IF + E). The study lasted for 8 weeks. Results: The results of the analysis show that lymphocyte cell levels in groups HFD + IF, HFD + IF, and HFD + IF + E were higher compared to groups CG-HFD (p < 0.05). Additionally, B lymphocyte and monocyte cell levels were higher in group HFD + IF + E compared to groups CG, CG + IF, and CG + IF + E, as well as CG, CG + IF, and CG + E, respectively. TNF-α levels were significantly higher in group HFD compared to the other groups. Furthermore, IL 10 levels were higher in group HFD + IF + E compared to the other groups. Conclusions: These findings indicate that moderate exercise and intermittent fasting, particularly in groups fed a high-fat diet, increased anti-inflammatory cytokine levels, and certain immune system cell counts, while decreasing pro-inflammatory cytokine levels.

Circadian clock synchrony and chronotherapy opportunities in cancer treatment

Cell-autonomous, tissue-specific circadian rhythms in gene expression and cellular processes have been observed throughout the human body. Disruption of daily rhythms by mistimed exposure to light, food intake, or genetic mutation has been linked to cancer development. Some medications are also more effective at certain times of day. However, a limited number of clinical studies have examined daily rhythms in the patient or drug timing as treatment strategies. This review highlights advances and challenges in cancer biology as a function of time of day. Recent evidence for daily rhythms and their entrainment in tumors indicate that personalized medicine should include understanding and accounting for daily rhythms in cancer patients.

Intermittent Fasting: Physiological Implications on Outcomes in Mice and Men

Intermittent fasting (IF) is a widely practiced dietary method that encompasses periodic restriction of food consumption. Due to its protective benefits against metabolic diseases, aging, and cardiovascular and neurodegenerative diseases, IF continues to gain attention as a preventative and therapeutic intervention to counteract these chronic diseases. Although numerous animal studies have reported positive health benefits of IF, its feasibility and efficacy in clinical settings remain controversial. Importantly, since dietary interventions such as IF have systemic effects, thoroughly investigating the tissue-specific changes in animal models is crucial to identify IF's mechanism and evaluate its potential adverse effects in humans. As such, we will review and compare the outcomes and underlying mechanisms of IF in both animal and human studies. Moreover, the limitations of IF and inconsistencies between preclinical and clinical studies will be discussed to provide insight into the gaps between translating research from bench to bedside.

Targeting Glucose Metabolism to Enhance Immunotherapy: Emerging Evidence on Intermittent Fasting and Calorie Restriction Mimetics

There is growing interest in harnessing lifestyle and pharmaceutical interventions to boost immune function, reduce tumor growth, and improve cancer treatment efficacy while reducing treatment toxicity. Interventions targeting glucose metabolism are particularly promising, as they have the potential to directly inhibit tumor cell proliferation. However, because anti-tumor immune effector cells also rely on glycolysis to sustain their clonal expansion and function, it remains unclear whether glucose-modulating therapies will support or hinder anti-tumor immunity. In this perspective, we summarize a growing body of literature that evaluates the effects of intermittent fasting, calorie restriction mimetics, and anti-hyperglycemic agents on anti-tumor immunity and immunotherapy outcomes. Based on the limited data currently available, we contend that additional pre-clinical studies and clinical trials are warranted to address the effects of co-administration of anti-hyperglycemic agents or glucose-lowering lifestyle modifications on anti-tumor immunity and cancer treatment outcomes. We stress that there is currently insufficient evidence to provide recommendations regarding these interventions to cancer patients undergoing immunotherapy. However, if found to be safe and effective in clinical trials, interventions targeting glucose metabolism could act as low-cost combinatorial adjuvants for cancer patients receiving immune checkpoint blockade or other immunotherapies.

Effects of timing of food intake and fat/carbohydrate ratio on insulin sensitivity and preconditioning against renal ischemia reperfusion injury by calorie restriction

BACKGROUND:

Dietary restriction (DR) improves lifespan, metabolic fitness and resilience in many organisms, but the role of dietary macronutrient composition and timing of food intake in specific benefits remains unclear.

OBJECTIVE:

We sought to compare the effects of two isocaloric DR regimes differing in the timing of food intake - every other day (EOD) fasting/feeding vs. daily calorie restriction (CR) – at two different fat/carbohydrate ratios on two well-established DR benefits, improved glucose homeostasis and protection from renal ischemia reperfusion injury in mice. We hypothesized that both EOD fasting and isocaloric CR would result in similar improvements in glucose homeostasis and stress resistance independent of macronutrient composition.

METHODS:

Six groups of mice were fed either semi-purified low-fat diet (LFD, 10% calories from fat) or high-fat diet (HFD, 60% calories from fat) and randomized into one of three dietary regimens: 1) ad libitum (AL), 2) EOD feeding/fasting, or 3) pair-fed daily to the average daily EOD intake within LFD or HFD feeding group resulting in daily CR. After 6 weeks, the following assessments were made: fasting blood glucose, glucose and insulin tolerance, and resistance to bilateral renal ischemia reperfusion injury using serum urea as a marker of renal function. Within the EOD group, the effects of prior day feeding (EOD^fed vs. EOD^fast) were also assessed.

RESULTS:

EOD mice ate ∼20–25% less food over time than AL mice on the corresponding LFD or HFD. EOD and CR mice displayed changes in body weight, fasting blood glucose levels and glucose tolerance commensurate with total calorie intake. No significant differences were observed in circulating IGF-1 levels. Insulin sensitivity improved independent of fat/carbohydrate ratio on daily CR and EOD^fast regimens, but not EOD^fed. HFD increased susceptibility to renal ischemia reperfusion in AL mice, while CR and EOD regimens gave significant protection independent of dietary fat content or fed or fasted day in the EOD group.

CONCLUSIONS:

Reduced food intake protects mice against renal ischemia reperfusion injury within 6 weeks independent of timing of food intake (CR, EOD^fast, EOD^fed) or fat content of diet (10% vs. 60%). Neither circulating IGF-1 levels (unchanged) nor whole-body insulin sensitivity (improved upon daily CR and EOD^fast but not EOD^fed) correlated with protection, so are unlikely to be involved mechanistically.

Employing proteomics to understand the effects of nutritional intervention in cancer treatment

Lifestyle optimizations are implementable changes that can have an impact on health and disease. Nutrition is a lifestyle optimization that has been shown to be of great importance in cancer initiation, progression, and metastasis. Dozens of clinical trials are currently in progress that focus on the nutritional modifications that cancer patients can make prior to and during medical care that increase the efficacy of treatment. In this review, we discuss various nutritional inventions for cancer patients and the analytical approaches to characterize the downstream molecular effects. We first begin by briefly explaining the many different forms of nutritional intervention currently being used in cancer treatment as well as their motivating biology. The forms of nutrient modulation described in this review include calorie restriction, the different practices of fasting, and carbohydrate restriction. The review then shifts to explain how proteomics is used to determine biomarkers of cancer and how it can be utilized in the future to determine the metabolic phenotype of a tumor, and inform physicians if nutritional intervention should be recommended for a cancer patient. Nutrigenomics aims to understand the relationship of nutrients and gene expression and can be used to understand the downstream molecular effects of nutrition restriction, partially through proteomic analysis. Proteomics is just beginning to be used as cancer diagnostic and predictive tools. However, these approaches have not been used to their full potential to understand nutritional intervention in cancer. Graphical abstract ᅟ.

Metabolic Effects of Intermittent Fasting

The objective of this review is to provide an overview of intermittent fasting regimens, summarize the evidence on the health benefits of intermittent fasting, and discuss physiological mechanisms by which intermittent fasting might lead to improved health outcomes. A MEDLINE search was performed using PubMed and the terms "intermittent fasting," "fasting," "time-restricted feeding," and "food timing." Modified fasting regimens appear to promote weight loss and may improve metabolic health. Several lines of evidence also support the hypothesis that eating patterns that reduce or eliminate nighttime eating and prolong nightly fasting intervals may result in sustained improvements in human health. Intermittent fasting regimens are hypothesized to influence metabolic regulation via effects on (a) circadian biology, (b) the gut microbiome, and (c) modifiable lifestyle behaviors, such as sleep. If proven to be efficacious, these eating regimens offer promising nonpharmacological approaches to improving health at the population level, with multiple public health benefits.

NutrimiRAging: Micromanaging Nutrient Sensing Pathways through Nutrition to Promote Healthy Aging

Current sociodemographic predictions point to a demographic shift in developed and developing countries that will result in an unprecedented increase of the elderly population. This will be accompanied by an increase in age-related conditions that will strongly impair human health and quality of life. For this reason, aging is a major concern worldwide. Healthy aging depends on a combination of individual genetic factors and external environmental factors. Diet has been proved to be a powerful tool to modulate aging and caloric restriction has emerged as a valuable intervention in this regard. However, many questions about how a controlled caloric restriction intervention affects aging-related processes are still unanswered. Nutrient sensing pathways become deregulated with age and lose effectiveness with age. These pathways are a link between diet and aging. Thus, fully understanding this link is a mandatory step before bringing caloric restriction into practice. MicroRNAs have emerged as important regulators of cellular functions and can be modified by diet. Some microRNAs target genes encoding proteins and enzymes belonging to the nutrient sensing pathways and, therefore, may play key roles in the modulation of the aging process. In this review, we aimed to show the relationship between diet, nutrient sensing pathways and microRNAs in the context of aging.

Could Intermittent Energy Restriction and Intermittent Fasting Reduce Rates of Cancer in Obese, Overweight, and Normal-Weight Subjects? A Summary of Evidence

Animal studies and human observational data link energy restriction (ER) to reduced rates of carcinogenesis. Most of these studies have involved continuous energy restriction (CER), but there is increasing public and scientific interest in the potential health and anticancer effects of intermittent energy restriction (IER) or intermittent fasting (IF), which comprise periods of marked ER or total fasting interspersed with periods of normal eating. This review summarizes animal studies that assessed tumor rates with IER and IF compared with CER or ad libitum feed consumption. The relevance of these animal data to human cancer is also considered by summarizing available human studies of the effects of IER or IF compared with CER on cancer biomarkers in obese, overweight, and normal-weight subjects. IER regimens that include periods of ER alternating with ad libitum feed consumption for 1, 2, or 3 wk have been reported to be superior to CER in reducing tumor rates in most spontaneous mice tumor models. Limited human data from short-term studies (≤6 mo) in overweight and obese subjects have shown that IER can lead to greater improvements in insulin sensitivity (homeostasis model assessment) than can CER, with comparable reductions in adipokines and inflammatory markers and minor changes in the insulin-like growth factor axis. There are currently no data comparing IER or IF with CER in normal-weight subjects. The benefits of IER in these short-term trials are of interest, but not sufficient evidence to recommend the use of IER above CER. Longer-term human studies of adherence to and efficacy and safety of IER are required in obese and overweight subjects, as well as normal-weight subjects.

Fasting for weight loss: an effective strategy or latest dieting trend?

With the increasing obesity epidemic comes the search for effective dietary approaches for calorie restriction and weight loss. Here I examine whether fasting is the latest 'fad diet' as portrayed in popular media and discuss whether it is a safe and effective approach or whether it is an idiosyncratic diet trend that promotes short-term weight loss, with no concern for long-term weight maintenance. Fasting has long been used under historical and experimental conditions and has recently been popularised by 'intermittent fasting' or 'modified fasting' regimes, in which a very low-calorie allowance is allowed, on alternate days (ADF) or 2 days a week (5:2 diet), where 'normal' eating is resumed on non-diet days. It is a simple concept, which makes it easy to follow with no difficult calorie counting every other day. This approach does seem to promote weight loss, but is linked to hunger, which can be a limiting factor for maintaining food restriction. The potential health benefits of fasting can be related to both the acute food restriction and chronic influence of weight loss; the long-term effect of chronic food restriction in humans is not yet clear, but may be a potentially interesting future dietary strategy for longevity, particularly given the overweight epidemic. One approach does not fit all in the quest to achieve body weight control, but this could be a dietary strategy for consideration. With the obesity epidemic comes the search for dietary strategies to (i) prevent weight gain, (ii) promote weight loss and (iii) prevent weight regain. With over half of the population of the United Kingdom and other developed countries being collectively overweight or obese, there is considerable pressure to achieve these goals, from both a public health and a clinical perspective. Certainly not one dietary approach will solve these complex problems. Although there is some long-term success with gastric surgical options for morbid obesity, there is still a requirement for dietary approaches for weight management for the overweight and obese population, particularly as invasive interventions carry post-operative risk of death due to complications. Effective dietary interventions are required that promote long-term adherence and sustained beneficial effects on metabolic and disease markers. In general, such interventions need to be palatable and satiating, meet minimal nutritional requirements, promote loss of fat and preserve lean body mass, ensure long-term safety, be simple to administer and monitor and have widespread public health utility. Intermittent fasting or alternate day fasting may be an option for achieving weight loss and maintenance.

Metabolic adaptations to short-term every-other-day feeding in long-living Ames dwarf mice

Restrictive dietary interventions exert significant beneficial physiological effects in terms of aging and age-related disease in many species. Every other day feeding (EOD) has been utilized in aging research and shown to mimic many of the positive outcomes consequent with dietary restriction. This study employed long living Ames dwarf mice subjected to EOD feeding to examine the adaptations of the oxidative phosphorylation and antioxidative defense systems to this feeding regimen. Every other day feeding lowered liver glutathione (GSH) concentrations in dwarf and wild type (WT) mice but altered GSH biosynthesis and degradation in WT mice only. The activities of liver OXPHOS enzymes and corresponding proteins declined in WT mice fed EOD while in dwarf animals, the levels were maintained or increased with this feeding regimen. Antioxidative enzymes were differentially affected depending on the tissue, whether proliferative or post-mitotic. Gene expression of components of liver methionine metabolism remained elevated in dwarf mice when compared to WT mice as previously reported however, enzymes responsible for recycling homocysteine to methionine were elevated in both genotypes in response to EOD feeding. The data suggest that the differences in anabolic hormone levels likely affect the sensitivity of long living and control mice to this dietary regimen, with dwarf mice exhibiting fewer responses in comparison to WT mice. These results provide further evidence that dwarf mice may be better protected against metabolic and environmental perturbations which may in turn, contribute to their extended longevity.

Caloric restriction augments radiation efficacy in breast cancer

Dietary modification such as caloric restriction (CR) has been shown to decrease tumor initiation and progression. We sought to determine if nutrient restriction could be used as a novel therapeutic intervention to enhance cytotoxic therapies such as radiation (IR) and alter the molecular profile of triple-negative breast cancer (TNBC), which displays a poor prognosis. In two murine models of TNBC, significant tumor regression is noted with IR or diet modification, and a greater regression is observed combining diet modification with IR. Two methods of diet modification were compared, and it was found that a daily 30% reduction in total calories provided more significant tumor regression than alternate day feeding. At the molecular level, tumors treated with CR and IR showed less proliferation and more apoptosis. cDNA array analysis demonstrated the IGF-1R pathway plays a key role in achieving this physiologic response, and multiple members of the IGF-1R pathway including IGF-1R, IRS, PIK3ca and mTOR were found to be downregulated. The innovative use of CR as a novel therapeutic option has the potential to change the biology of tumors and enhance the opportunity for clinical benefit in the treatment of patients with TNBC.

Novel combination of collagen dynamics analysis and transcriptional profiling reveals fibrosis-relevant genes and pathways

Collagen deposition is a key process during idiopathic pulmonary fibrosis; however, little is known about the dynamics of collagen formation during disease development. Tissue samples of early stages of human disease are not readily available and it is difficult to identify changes in collagen content, since standard collagen analyses do not distinguish between 'old' and 'new' collagen. Therefore, the current study aimed to (i) investigate the dynamics of new collagen formation in mice using bleomycin-induced lung fibrosis in which newly synthesized collagen was labeled with deuterated water and (ii) use this information to identify genes and processes correlated to new collagen formation. Lung fibrosis was induced in female C57Bl/6 mice by bleomycin instillation. Animals were sacrificed at 1 to 5 weeks after fibrosis induction. Collagen synthesized during the week before sacrifice was labeled with deuterium by providing mice with deuterated drinking water. After sacrifice, we collected lung tissue for microarray analysis, determination of new collagen formation, and histology. Furthermore, we measured in vitro the expression of selected genes after transforming growth factor (TGF) β₁-induced myofibroblast differentiation. Deuterated water labeling showed a strong increase in new collagen formation already during the first week after fibrosis induction and a complete return to baseline at five weeks. Correlation of new collagen formation data with gene expression data allowed us to create a gene expression signature of fibrosis within the lung and revealed fibrosis-specific processes, among which proliferation. This was confirmed by measuring cell proliferation and collagen synthesis simultaneously using deuterated water incorporation in a separate experiment. Furthermore, new collagen formation strongly correlated with gene expression of e.g. elastin, Wnt-1 inducible signaling pathway protein 1, tenascin C, lysyl oxidase, and type V collagen. Gene expression of these genes was upregulated in vitro in fibroblasts stimulated with TGFβ₁. Together, these data demonstrate, using a novel combination of technologies, that the core process of fibrosis, i.e. the formation of new collagen, correlates not only with a wide range of genes involved in general extracellular matrix production and modification but also with cell proliferation. The observation that the large majority of the genes which correlated with new collagen formation also were upregulated during TGFβ₁-induced myofibroblast differentiation provides further evidence for their involvement in fibrosis.

Dexamethasone-mediated changes in adipose triacylglycerol metabolism are exaggerated, not diminished, in the absence of a functional GR dimerization domain

The glucocorticoid (GC) receptor (GR) has multiple effector mechanisms, including dimerization-mediated transactivation of target genes via DNA binding and transcriptional repression mediated by protein-protein interactions. Much attention has been focused on developing selective GR modulators that would dissociate adverse effects from therapeutic anti-inflammatory effects. The GR(dim/dim) mouse has a mutation in the dimerization domain of GR and has been shown to have attenuated transactivation with intact repression. To understand the role of GR dimerization-dependent targets in multiple tissues, we measured metabolic fluxes through several disease-relevant GC target pathways using heavy water labeling and mass spectrometry in wild-type and GR(dim/dim) mice administered the potent GC dexamethasone (DEX). Absolute triglyceride synthesis was increased in both wild-type and GR(dim/dim) mice by DEX in the inguinal and epididymal fat depots. GR(dim/dim) mice showed an exaggerated response to DEX in both depots. De novo lipogenesis was also greatly increased in both depots in response to DEX in GR(dim/dim), but not wild-type mice. In contrast, the inhibitory effect of DEX on bone and skin collagen synthesis rates was greater in wild-type compared with GR(dim/dim) mice. Wild-type mice were more sensitive to DEX-dependent decreases in insulin sensitivity than GR(dim/dim) mice. Wild-type and GR(dim/dim) mice were equally sensitive to DEX-dependent decreases in muscle protein synthesis. Chronic elevation of GCs in GR(dim/dim) mice results in severe runting and lethality. In conclusion, some metabolic effects of GC treatment are exaggerated in adipose tissue of GR(dim/dim) mice, suggesting that selective GR modulators based on dissociating GR transactivation from repression should be evaluated carefully.

Alternate-day fasting diet improves fructose-induced insulin resistance in mice

Increased fructose consumption is linked to insulin resistance, weight gain, hyperlipidemia and hypertension. Although the advantages of several dietary restriction regimens have been demonstrated, the effects of alternate-day fasting (ADF) on fructose-induced insulin resistance have not yet been studied. This study is based on a new modification on ADF by combining the fructose-rich solution (10% w/v) and regular mice diet. Mice were randomly allocated into four groups: ADF50% (50% restriction in chow food intake but ad libitum fructose drink), ADF100% (100% restriction for chow food but ad libitum fructose drink), control (ad libitum chow food intake plus tap water) and daily food and fructose (DFF) (had free access to both chow and fructose solution). Biweekly fasting blood sugar (FBS), glucose tolerance test (GTT) and insulin tolerance test (ITT) were conducted. All groups gained weight during the study (p < 0.05). Body weights of DFF and control groups did not differ from that of ADF groups, but ADF50% gained more (p < 0.01) weights than ADF100% through the study. Total calorie intake (feed + fast days) of ADF50% was higher than that of ADF100% (p < 0.001) and control (p < 0.03). In addition, ADF groups consumed more energy than the control and DFF groups in feed (ad libitum) days (p < 0.05). At the end of the study, the mean FBS levels in the control and ADF100% groups were similar and significantly lower in relation to that of DFF and ADF50% groups (p < 0.01). Measurements of area under the curve in GTT and ITT revealed that the ADF100% group was more insulin-sensitive than the DFF and ADF50% groups. In conclusion, these data suggest that the ADF100% improves fructose-induced insulin resistance in mice.

Comprehensive modulation of tumor progression and regression with periodic fasting and refeeding circles via boosting IGFBP-3 loops and NK responses

Progressive tumor-bearing patients deserve to benefit from more realistic approaches. Here, a study revealed the impact of modified periodic fasting and refeeding regimen on tumor progression or regression with little or no loss of food intake and body weight. Human A549 lung, HepG-2 liver, and SKOV-3 ovary progressive tumor-bearing mice were established and subjected to 4 wk of periodic fasting/refeeding cycles (PFRC), including periodic 1-d fasting/6-d refeeding weekly (protocol 1) and periodic 2-d fasting/5-d refeeding weekly (P2DF/5DR, protocol 2), with ad libitum (AL)-fed hosts as controls. Afterwards, PFRC groups exhibited tumor growth arrest with some tendency towards regression; especially, complete regression of progressive tumors and metastases comprised between 43.75 and 56.25% of tumor-challenged hosts in P2DF/5DR group (P < 0.05). AL controls, in contrast, showed continuous tumor progression and metastasis. Finally, 100% hosts in P2DF/5DR and 62.5-68.75% in periodic 1-d fasting/6-d refeeding weekly groups survived a 4-month study period vs. only 31.25-37.5% in AL control group. Immunological assays and Luminex microarray revealed that tumor growth remission is mainly via natural killer cell (NK) reactivity and cross-regulation of IGF-binding protein-3, IGF/IGF-receptor, and megakaryocyte growth and development factor autocrine and paracrine loops. In vivo cellular and humoral assays indicated that tumor-regressive induction by PFRC protocols could be partly terminated by NK cell and IGF-binding protein-3 blockade or replenishment of IGF-I/-II and megakaryocyte growth and development factor. These findings offer a better understanding of comprehensive modulation of periodic fasting/refeeding strategy on the balance between tumor progression and regression.

The effects of physiological adaptations to calorie restriction on global cell proliferation rates

Calorie restriction (CR) reduces the rate of cell proliferation in mitotic tissues. It has been suggested that this reduction in cell proliferation may mediate CR-induced increases in longevity. However, the mechanisms that lead to CR-induced reductions in cell proliferation rates remain unclear. To evaluate the CR-induced physiological adaptations that may mediate reductions in cell proliferation rates, we altered housing temperature and access to voluntary running wheels to determine the effects of food intake, energy expenditure, percent body fat, and body weight on proliferation rates of keratinocytes, liver cells, mammary epithelial cells, and splenic T-cells in C57BL/6 mice. We found that ∼20% CR led to a reduction in cell proliferation rates in all cell types. However, lower cell proliferation rates were not observed with reductions in 1) food intake and energy expenditure in female mice housed at 27°C, 2) percent body fat in female mice provided running wheels, or 3) body weight in male mice provided running wheels compared with ad libitum-fed controls. In contrast, reductions in insulin-like growth factor I were associated with decreased cell proliferation rates. Taken together, these data suggest that CR-induced reductions in food intake, energy expenditure, percent body fat, and body weight do not account for the reductions in global cell proliferation rates observed in CR. In addition, these data are consistent with the hypothesis that reduced cell proliferation rates could be useful as a biomarker of interventions that increase longevity.

The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women

BACKGROUND

The problems of adherence to energy restriction in humans are well known.

OBJECTIVE

To compare the feasibility and effectiveness of intermittent continuous energy (IER) with continuous energy restriction (CER) for weight loss, insulin sensitivity and other metabolic disease risk markers.

DESIGN

Randomized comparison of a 25% energy restriction as IER (∼ 2710 kJ/day for 2 days/week) or CER (∼ 6276 kJ/day for 7 days/week) in 107 overweight or obese (mean (± s.d.) body mass index 30.6 (± 5.1) kg m(-2)) premenopausal women observed over a period of 6 months. Weight, anthropometry, biomarkers for breast cancer, diabetes, cardiovascular disease and dementia risk; insulin resistance (HOMA), oxidative stress markers, leptin, adiponectin, insulin-like growth factor (IGF)-1 and IGF binding proteins 1 and 2, androgens, prolactin, inflammatory markers (high sensitivity C-reactive protein and sialic acid), lipids, blood pressure and brain-derived neurotrophic factor were assessed at baseline and after 1, 3 and 6 months.

RESULTS

Last observation carried forward analysis showed that IER and CER are equally effective for weight loss: mean (95% confidence interval ) weight change for IER was -6.4 (-7.9 to -4.8) kg vs -5.6 (-6.9 to -4.4) kg for CER (P-value for difference between groups = 0.4). Both groups experienced comparable reductions in leptin, free androgen index, high-sensitivity C-reactive protein, total and LDL cholesterol, triglycerides, blood pressure and increases in sex hormone binding globulin, IGF binding proteins 1 and 2. Reductions in fasting insulin and insulin resistance were modest in both groups, but greater with IER than with CER; difference between groups for fasting insulin was -1.2 (-1.4 to -1.0) μU ml(-1) and for insulin resistance was -1.2 (-1.5 to -1.0) μU mmol(-1) l(-1) (both P = 0.04).

CONCLUSION

IER is as effective as CER with regard to weight loss, insulin sensitivity and other health biomarkers, and may be offered as an alternative equivalent to CER for weight loss and reducing disease risk.

Immune deviation and alleviation of allergic reactions in mice subjected to dietary restriction

We examined cytokine production and allergic reactions in mice fed ad libitum (AL) and subjected to dietary restriction (DR). DR retarded the increase in body weight, and peripheral blood T cells in the DR mice produced less IFN-gamma and more IL-4 in response to immobilized anti-CD3 mAb. Systemic immunization and intranasal challenge with ovalbumin (OVA) induced accumulation of leukocytes into the lung, increase in IL-4 level in bronchoalveolar lavage fluid (BALF), and rise in serum IgE in the AL mice. In contrast, these allergic symptoms were alleviated in the DR mice. Furthermore, the relative proportion of IL-4-producing T cells responsive to OVA was less in the DR mice than the AL mice. DR tended to decrease the proportion and cytolytic activity of NK cells in the spleen, especially in younger mice. These results indicate that DR can prevent the expansion of allergen-specific IL-4-producing T cells followed by suppression of the allergic reaction, but might dampen NK cell activity.

Modified alternate-day fasting and cardioprotection: relation to adipose tissue dynamics and dietary fat intake

The relation between alternate-day fasting (ADF) and cardioprotection remains uncertain. In the present study, we examined the ability of modified ADF, with a low-fat (LF) vs high-fat (HF) background diet, to modulate adipose tissue physiology in a way that may protect against coronary heart disease. In a 4-week study, male C57BL/6 mice were randomized to 1 of 3 groups: (1) ADF-85%-LF (85% energy restriction on fast day, ad libitum fed on feed day, on an LF diet), (2) ADF-85%-HF (same protocol but HF diet), and (3) control (ad libitum fed). Throughout the study, body weight did not differ between ADF and control animals. Proportion of subcutaneous fat increased (P < .01), whereas the proportion of visceral fat decreased (P < .01), in both ADF groups. Triglyceride (TG) synthesis was augmented (P < .05) in subcutaneous fat, but remained unchanged in visceral fat. Adiponectin concentrations were elevated (P < .05), whereas leptin and resistin levels decreased (P < .05). Aortic vascular smooth muscle cell proliferation was reduced (P < .05) by 60% and 76% on the LF and HF diets, respectively. Plasma total cholesterol, TG, and free fatty acid concentrations also decreased (P < .05). In summary, modified ADF regimens alter adipose tissue physiology (ie, body fat distribution, TG metabolism, and adipokines) in a way that may protect against coronary heart disease. These beneficial effects were noted over a wide range of fat intake, suggesting that ADF may be protective even in the presence of HF diets.

Do calorie restriction or alternate-day fasting regimens modulate adipose tissue physiology in a way that reduces chronic disease risk?

Adipose tissue physiology plays an important role in the development of several obesity-related disorders. Dietary restriction regimens, i.e., daily calorie restriction (CR) or alternate-day fasting (ADF), have been shown to decrease the risk of these disorders. Whether changes in adipose mass or physiology are required for the beneficial effects of CR or ADF is an important question. Accordingly, this review summarizes the effects of CR and ADF regimens on parameters of adipose physiology, i.e., adipose tissue morphology, triglyceride metabolism, and adipokine release, and attempts to link these changes to indicators of chronic disease risk.

Measurement of cell proliferation by heavy water labeling

DNA replication occurs almost exclusively during S-phase of the cell cycle and represents a simple biochemical metric of cell division. Previous methods for measuring cell proliferation rates have important limitations. Here, we describe experimental protocols for measuring cell proliferation and death rates based on the incorporation of deuterium ((2)H) from heavy water ((2)H(2)O) into the deoxyribose moiety of purine deoxyribonucleotides in DNA of dividing cells. Label incorporation is measured by gas chromatography/mass spectrometry. Modifications of the basic protocol permit analysis of small cell samples (down to 2,000 cells). The theoretical basis and operational requirements for effective use of these methods to measure proliferation and death rates of cells in vivo are described. These methods are safe for use in humans, have technical and interpretation advantages over alternative techniques and can be used on small numbers of cells. The protocols enable definitive in vivo studies of the fraction or absolute number of newly divided cells and their subsequent survival kinetics in animals and humans.

Modified alternate-day fasting regimens reduce cell proliferation rates to a similar extent as daily calorie restriction in mice

Calorie restriction (CR) and alternate-day fasting (ADF) reduce cancer risk and reduce cell proliferation rates. Whether modified ADF regimens (i.e., allowing a portion of energy needs to be consumed on the fast day) work, as well as true ADF or CR to reduce global cell proliferation rates, remains unresolved. Here, we measured the effects of true ADF, modified ADF, and daily CR on cell proliferation rates in mice. Thirty female C57BL/6J mice were randomized to one of five interventions for 4 wk: 1) CR-25% (25% reduction in daily energy intake), 2) ADF-75% (75% reduction on fast day), 3) ADF-85% (85% reduction on fast day), 4) ADF-100% (100% reduction on fast day), and 5) control (ad libitum intake). Body weights of the ADF groups did not differ from controls, whereas the CR-25% group weighed less than all other groups posttreatment. Epidermal cell proliferation decreased (P<0.01) by 29, 20, and 31% in the CR-25%, ADF-85% and ADF-100% groups, respectively, relative to controls. Proliferation rates of splenic T cells were reduced (P<0.01) by 37, 32, and 31% in the CR-25%, ADF-85%, and ADF-100% groups, respectively, and mammary epithelial cell proliferation was 70, 65, and 62% lower (P<0.01), compared with controls. Insulin-like growth factor-1 levels were reduced (P<0.05) in the CR-25% and ADF-100% groups only. In summary, modified ADF, allowing the consumption of 15% of energy needs on the restricted intake day, decreases global cell proliferation similarly as true ADF and daily CR without reducing body weight.