A reason for intermittent fasting to suppress the awakening of dormant breast tumors

Maternal intermittent fasting deteriorates offspring metabolism via suppression of hepatic mTORC1 signaling

The metabolic benefits of intermittent fasting (IF) have been well recognized. However, limited studies have examined the relationship between long-term maternal IF before pregnancy and offspring health. In this study, a C57BL/6J mouse model of long-term IF before pregnancy was established: 4-week-old female mice were subjected to alternate-day fasting for 12 weeks and resumed normal diet after mating. Female mice in the control group were fed ad libitum. Offspring mice were weaned at 6 weeks of age and fed a normal chow diet or a 60% high-fat diet. The effects of long-term pre-pregnancy IF on offspring metabolism and its underlying mechanism were examined. We found that neonatal IF offspring weighted significantly less relevant to control mice. This difference gradually disappeared as a result of catch-up growth. In the IF offspring, adipose tissue mass was significantly increased. This alteration was associated with a considerable deterioration in glucose tolerance. No significant difference in food intake was observed. Further, lipid deposition as well as triglyceride contents in the liver were greatly increased. Maternal IF significantly decreased levels of DNA methyltransferase in the liver of offspring. DNA methylation modifications of molecules associated with the mTORC1 signaling pathway were significantly altered, leading to the significant inhibition of mTORC1 signaling. Overexpression of S6K1 activated hepatic mTORC1 signaling and reversed the metabolic dysfunction in IF offspring. In conclusion, long-term pre-pregnancy IF increases hepatic steatosis and adiposity, as well as impairs glucose metabolism in adult offspring. This occurs through DNA methylation-dependent suppression of hepatic mTORC1 signaling activity.

Effects of short-term fasting on cancer treatment

Growing preclinical evidence shows that short-term fasting (STF) protects from toxicity while enhancing the efficacy of a variety of chemotherapeutic agents in the treatment of various tumour types. STF reinforces stress resistance of healthy cells, while tumor cells become even more sensitive to toxins, perhaps through shortage of nutrients to satisfy their needs in the context of high proliferation rates and/or loss of flexibility to respond to extreme circumstances. In humans, STF may be a feasible approach to enhance the efficacy and tolerability of chemotherapy. Clinical research evaluating the potential of STF is in its infancy. This review focuses on the molecular background, current knowledge and clinical trials evaluating the effects of STF in cancer treatment. Preliminary data show that STF is safe, but challenging in cancer patients receiving chemotherapy. Ongoing clinical trials need to unravel if STF can also diminish toxicity and increase efficacy of chemotherapeutic regimes in daily practice.

A metabolic core model elucidates how enhanced utilization of glucose and glutamine, with enhanced glutamine-dependent lactate production, promotes cancer cell growth: The WarburQ effect

Cancer cells share several metabolic traits, including aerobic production of lactate from glucose (Warburg effect), extensive glutamine utilization and impaired mitochondrial electron flow. It is still unclear how these metabolic rearrangements, which may involve different molecular events in different cells, contribute to a selective advantage for cancer cell proliferation. To ascertain which metabolic pathways are used to convert glucose and glutamine to balanced energy and biomass production, we performed systematic constraint-based simulations of a model of human central metabolism. Sampling of the feasible flux space allowed us to obtain a large number of randomly mutated cells simulated at different glutamine and glucose uptake rates. We observed that, in the limited subset of proliferating cells, most displayed fermentation of glucose to lactate in the presence of oxygen. At high utilization rates of glutamine, oxidative utilization of glucose was decreased, while the production of lactate from glutamine was enhanced. This emergent phenotype was observed only when the available carbon exceeded the amount that could be fully oxidized by the available oxygen. Under the latter conditions, standard Flux Balance Analysis indicated that: this metabolic pattern is optimal to maximize biomass and ATP production; it requires the activity of a branched TCA cycle, in which glutamine-dependent reductive carboxylation cooperates to the production of lipids and proteins; it is sustained by a variety of redox-controlled metabolic reactions. In a K-ras transformed cell line we experimentally assessed glutamine-induced metabolic changes. We validated computational results through an extension of Flux Balance Analysis that allows prediction of metabolite variations. Taken together these findings offer new understanding of the logic of the metabolic reprogramming that underlies cancer cell growth.

Hallmarks describing common key events in initiation, maintenance and progression of cancer have been identified. One hallmark deals with rewiring of metabolic reactions required to sustain enhanced cell proliferation. The availability of molecular, mechanistic models of cancer hallmarks will mightily improve optimized personal treatment and new drug discovery. Metabolism is the only hallmark for which it is currently possible to derive large scale mathematical models, which have predictive ability. In this paper, we exploit a constraint-based model of the core metabolism required for biomass conversion of the most relevant nutrients—glucose and glutamine—to clarify the logic of control of cancer metabolism. We newly report that, when available oxygen is not sufficient to fully oxidize available glucose and glutamine carbons–a situation compatible with that observed under normal oxygen conditions in human and in cancer cells growing in vitro—utilization of glutamine by reductive carboxylation and conversion of glucose and glutamine to lactate confer advantage for biomass production. Redox homeostasis can be maintained through the use of different alternative pathways. In conclusion, this paper offers a logic interpretation to the link between metabolic rewiring and enhanced proliferation, which may offer new approaches to targeted drug discovery and utilization.

Ramadan Fasting and Patients with Cancer: State-of-the-Art and Future Prospects

Ramadan fasting represents one of the five pillars of the Islam creed. Even though some subjects (among which patients) are exempted from observing this religious duty, they may be eager to share this particular moment of the year with their family and peers. However, there are no guidelines or standardized protocols that can help physicians to properly address the issue of patients with cancer fasting in Ramadan and correctly advising them. Moreover, in a more interconnected and globalized society, in which more and more Muslim patients live in the Western countries, this topic is of high interest also for the general practitioner. For this purpose, we carried out a systematic review on the subject. Our main findings are that (1) very few studies have been carried out, addressing this issue, (2) evidence concerning quality of life and compliance to treatment is contrasting and scarce, and (3) generally speaking, few patients ask their physicians whether they can safely fast or not. For these reasons, further research should be performed, given the relevance and importance of this topic.