Tumor Cells Growth and Survival Time with the Ketogenic Diet in Animal Models: A Systematic Review

Inhibition of Carbohydrate Metabolism Potentiated by the Therapeutic Effects of Oxidative Phosphorylation Inhibitors in Colon Cancer Cells

Cancer cells undergo a significant level of "metabolic reprogramming" or "remodeling" to ensure an adequate supply of ATP and "building blocks" for cell survival and to facilitate accelerated proliferation. Cancer cells preferentially use glycolysis for ATP production (the Warburg effect); however, cancer cells, including colorectal cancer (CRC) cells, also depend on oxidative phosphorylation (OXPHOS) for ATP production, a finding that suggests that both glycolysis and OXPHOS play significant roles in facilitating cancer progression and proliferation. Our prior studies identified a semisynthetic isoflavonoid, DBI-1, that served as an AMPK activator targeting mitochondrial complex I. Furthermore, DBI-1 and a glucose transporter 1 (GLUT1) inhibitor, BAY-876, synergistically inhibited CRC cell growth in vitro and in vivo. We now report a study of the structure-activity relationships (SARs) in the isoflavonoid family in which we identified a new DBI-1 analog, namely, DBI-2, with promising properties. Here, we aimed to explore the antitumor mechanisms of DBIs and to develop new combination strategies by targeting both glycolysis and OXPHOS. We identified DBI-2 as a novel AMPK activator using an AMPK phosphorylation assay as a readout. DBI-2 inhibited mitochondrial complex I in the Seahorse assays. We performed proliferation and Western blotting assays and conducted studies of apoptosis, necrosis, and autophagy to corroborate the synergistic effects of DBI-2 and BAY-876 on CRC cells in vitro. We hypothesized that restricting the carbohydrate uptake with a KD would mimic the effects of GLUT1 inhibitors, and we found that a ketogenic diet significantly enhanced the therapeutic efficacy of DBI-2 in CRC xenograft mouse models, an outcome that suggested a potentially new approach for combination cancer therapy.

A Preliminary Study Indicating Improvement in the Median Survival Time of Glioblastoma Multiforme Patients by the Application of Deuterium Depletion in Combination with Conventional Therapy

Glioblastoma multiforme (GBM) and malignant gliomas are the most common primary malignant brain tumors. Temozolomide (TMZ) chemotherapy plus radiation therapy (RT), admi-mistered after debulking surgery, increased the median survival time (MST) from 12.1 months with RT alone merely to 14.6 months, respectively. In this study, the actions of deuterium-depleted water (DDW) on the survival of GBM patients who also received conventional therapies was investigated. Without changing the conventional treatment, the daily fluid intake of the patients was wholly replaced with DDW in 1.5-2 L per day volume to reduce the D concentration in their bodies. The primary endpoint was the MST. The 55 patients involved in this study, who received conventional treatment and consumed DDW, showed a longer MST (30 months) compared to the historical control (12.1-14.6 months). There was a massive difference between the two genders in the calculated MST values; it was 25 months in the male subgroup (n = 33) and 42 months in the female subgroup (n = 22), respectively. The MST was 27 months without TMZ treatment (38 patients) and 42 months in the TMZ-treated group (17 patients), respectively. For the selected 31 patients, who consumed DDW in the correct way in addition to their conventional treatments, their MST was calculated as 30 months. Within this group, the 20 subjects who had relapsed before DDW treatment had 30 months of MST, but in those 10 subjects who were in remission when DDW treatment started, their MST was 47 months. In the subgroup of patients who began their DDW treatment parallel with radiotherapy, their MST was again 47 months, and it was 25 months when their DDW treatment was started at 8 weeks or later after the completion of radiotherapy. Altogether, these survival times were substantially prolonged compared to the prospective clinical data of patients with primary GBM. Consequently, if conventional therapies are supplemented with D depletion, better survival can be achieved in the advanced stage of GBM than with the known targeted or combination therapies. Application of DDW is recommended in all stages of the disease before surgery and in parallel with radiotherapy, and repeated DDW courses are advised when remission has been achieved.

The Role of Ketogenic Diet in the Treatment of Neuroblastoma

The ketogenic diet (KD) was initially used in 1920 for drug-resistant epileptic patients. From this point onward, ketogenic diets became a pivotal part of nutritional therapy research. To date, KD has shown therapeutic potential in many pathologies such as Alzheimer's disease, Parkinson's disease, autism, brain cancers, and multiple sclerosis. Although KD is now an adjuvant therapy for certain diseases, its effectiveness as an antitumor nutritional therapy is still an ongoing debate, especially in Neuroblastoma. Neuroblastoma is the most common extra-cranial solid tumor in children and is metastatic at initial presentation in more than half of the cases. Although Neuroblastoma can be managed by surgery, chemotherapy, immunotherapy, and radiotherapy, its 5-year survival rate in children remains below 40%. Earlier studies have proposed the ketogenic diet as a possible adjuvant therapy for patients undergoing treatment for Neuroblastoma. In this study, we seek to review the possible roles of KD in the treatment of Neuroblastoma.

Deuterium Content of the Organic Compounds in Food Has an Impact on Tumor Growth in Mice

Research with deuterium-depleted water (DDW) in the last two decades proved that the deuterium/hydrogen ratio has a key role in cell cycle regulation and cellular metabolism. The present study aimed to investigate the possible effect of deuterium-depleted yolk (DDyolk) alone and in combination with DDW on cancer growth in two in vivo mouse models. To produce DDyolk, the drinking water of laying hens was replaced with DDW (25 ppm) for 6 weeks, resulting in a 60 ppm D level in dried egg yolk that was used as a deuterium-depleted food additive. In one model, 4T1, a cell line with a high metastatic capacity to the lung was inoculated in the mice's mammary pad. After three weeks of treatment with DDW and/or DDyolk, the tumor volume in the lungs was smaller in all treated groups vs. controls with natural D levels. Tumor growth and survival in mice transplanted with an MCF-7 breast cancer cell line showed that the anticancer effect of DDW was enhanced by food containing the deuterium-depleted yolk. The study confirmed the importance of the D/H ratio in consumed water and in metabolic water produced by the mitochondria while oxidizing nutrient molecules. This is in line with the concept that the initiation of cell growth requires the cells to generate a higher D/H ratio, but DDW, DDyolk, or the naturally low-D lipids in a ketogenic diet, have a significant effect on tumor growth by preventing the cells from raising the D/H ratio to the threshold.

Critical Review on Fatty Acid-Based Food and Nutraceuticals as Supporting Therapy in Cancer

Fatty acids have an important place in both biological and nutritional contexts and, from a clinical point of view, they have known consequences for diseases’ onset and development, including cancer. The use of fatty acid-based food and nutraceuticals to support cancer therapy is a multidisciplinary subject, involving molecular and clinical research. Knowledge regarding polyunsaturated fatty acids essentiality/oxidizability and the role of lipogenesis-desaturase pathways for cell growth, as well as oxidative reactivity in cancer cells, are discussed, since they can drive the choice of fatty acids using their multiple roles to support antitumoral drug activity. The central role of membrane fatty acid composition is highlighted for the application of membrane lipid therapy. As fatty acids are also known as biomarkers of cancer onset and progression, the personalization of the fatty acid-based therapy is also possible, taking into account other important factors such as formulation, bioavailability and the distribution of the supplementation. A holistic approach emerges combining nutra- and pharma-strategies in an appropriate manner, to develop further knowledge and applications in cancer therapy.

Ketogenesis Attenuates KLF5-Dependent Production of CXCL12 to Overcome the Immunosuppressive Tumor Microenvironment in Colorectal Cancer

The dynamic composition of the tumor microenvironment (TME) can markedly alter the response to targeted therapies for colorectal cancer. Cancer-associated fibroblasts (CAF) are major components of TMEs that can direct and induce infiltration of immunosuppressive cells through secreted cytokines such as CXCL12. Ketogenic diets (KD) can inhibit tumor growth and enhance the anticancer effects of immune checkpoint blockade. However, the role of ketogenesis on the immunosuppressive TME is not known. Here, we show that decreased ketogenesis is a signature of colorectal cancer and that an increase in ketogenesis using a KD decreases CXCL12 production in tumors, serum, liver, and lungs. Moreover, increasing ketogenesis by overexpression of the ketogenic enzyme 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) or treatment with the ketone body β-hydroxybutyrate markedly decreased expression of KLF5, which binds the CXCL12 promoter and induces CXCL12 expression in CAFs. KD decreased intratumoral accumulation of immunosuppressive cells, increased infiltration of natural killer and cytotoxic T cells, and enhanced the anticancer effects of PD-1 blockade in murine-derived colorectal cancer. Furthermore, increasing ketogenesis inhibited colorectal cancer migration, invasion, and metastasis in vitro and in vivo. Overall, ketogenesis is downregulated in the colorectal cancer TME, and increased ketogenesis represses KLF5-dependent CXCL12 expression to improve the immunosuppressive TME, which leads to the enhanced efficacy of immunotherapy and reduced metastasis. Importantly, this work demonstrates that downregulation of de novo ketogenesis in the TME is a critical step in colorectal cancer progression.

SIGNIFICANCE

This study identifies ketogenesis as a critical regulator of the tumor microenvironment in colorectal cancer and suggests the potential for ketogenic diets as a metabolic strategy to overcome immunosuppression and prolong survival. See related commentary by Montrose and Galluzzi, p. 1464.

Blocking the Increase of Intracellular Deuterium Concentration Prevents the Expression of Cancer-Related Genes, Tumor Development, and Tumor Recurrence in Cancer Patients

The possible role of the naturally occurring deuterium in the regulation of cell division was first described in the 1990s. To investigate the mechanism of influence of deuterium (D) on cell growth, expression of 236 cancer-related and 536 kinase genes were tested in deuterium-depleted (40 and 80 ppm) and deuterium-enriched (300 ppm) media compared to natural D level (150 ppm). Among genes with expression changes exceeding 30% and copy numbers over 30 (124 and 135 genes, respectively) 97.3% of them was upregulated at 300 ppm D-concentration. In mice exposed to chemical carcinogen, one-year survival data showed that deuterium-depleted water (DDW) with 30 ppm D as drinking water prevented tumor development. One quarter of the treated male mice survived 344 days, the females 334 days, while one quarter of the control mice survived only 188 and 156 days, respectively. In our human retrospective study 204 previously treated cancer patients with disease in remission, who consumed DDW, were followed. Cumulative follow-up time was 1024 years, and average follow-up time per patient, 5 years (median: 3.6 years). One hundred and fifty-six patients out of 204 (77.9%) did not relapse during their 803 years cumulative follow-up time. Median survival time (MST) was not calculable due to the extremely low death rate (11 cancer-related deaths, 5.4% of the study population). Importantly, 8 out of 11 deaths occurred several years after stopping DDW consumption, confirming that regular consumption of DDW can prevent recurrence of cancer. These findings point to the likely mechanism in which consumption of DDW keeps D-concentration below natural levels, preventing the D/H ratio from increasing to the threshold required for cell division. This in turn can serve as a key to reduce the relapse rate of cancer patients and/or to reduce cancer incidence in healthy populations.

The use of ketogenic diets in cancer patients: a systematic review

Ketogenic diets are a widely known, yet controversial treatment for cancer patients. In this review, we summarize the clinical evidence for anti-tumor effects, as well as the effects on anthropometry, quality of life, adverse events and adherence in cancer patients. In April 2019, a systematic search was conducted searching five electronic databases (EMBASE, Cochrane, PsychInfo, CINAHL and Medline) to find studies analyzing the use, effectiveness and potential harm of a ketogenic diet in cancer patients of any age as sole or complementary therapy. From all 19.211 search results, 46 publications concerning 39 studies with 770 patients were included in this systematic review. The therapy concepts included all forms of diets with reduced carbohydrate intake, that aimed to achieve ketosis for patients with different types of cancer. Most studies had a low quality, high risk of bias and were highly heterogeneous. There was no conclusive evidence for anti-tumor effects or improved OS. The majority of patients had significant weight loss and mild to moderate side effects. Adherence to the diet was rather low in most studies. Due to the very heterogeneous results and methodological limitations of the included studies, clinical evidence for the effectiveness of ketogenic diets in cancer patients is still lacking.

Ketogenic Diets in Pancreatic Cancer and Associated Cachexia: Cellular Mechanisms and Clinical Perspectives

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and extremely therapy-resistant cancer. It is estimated that up to 80% of PDAC patients present with cachexia, a multifactorial disorder characterized by the involuntary and ongoing wasting of skeletal muscle that affects therapeutic response and survival. During the last decade, there has been an increased interest in exploring dietary interventions to complement the treatment of PDAC and associated cachexia. Ketogenic diets (KDs) have gained attention for their anti-tumor potential. Characterized by a very low carbohydrate, moderate protein, and high fat composition, this diet mimics the metabolic changes that occur in fasting. Numerous studies report that a KD reduces tumor growth and can act as an adjuvant therapy in various cancers, including pancreatic cancer. However, research on the effect and mechanisms of action of KDs on PDAC-associated cachexia is limited. In this narrative review, we summarize the evidence of the impact of KDs in PDAC treatment and cachexia mitigation. Furthermore, we discuss key cellular mechanisms that explain KDs’ potential anti-tumor and anti-cachexia effects, focusing primarily on reprogramming of cell metabolism, epigenome, and the gut microbiome. Finally, we provide a perspective on future research needed to advance KDs into clinical use.

Ketotherapy as an epigenetic modifier in cancer

Epigenetic alterations in cancer play a variety of roles. Aberrant DNA methylation, as one of the epigenetic mechanisms, has been widely studied in both tumor and liquid biopsies and provide a useful bench mark for treatment response in cancer. Recently, several studies have reported an association between the type of diet and epigenetic modifications. Whereby there is a growing interest in finding the "anti-cancer diet formula", if such a thing exists. In this sense, ketogenic diets (KD) have reported potentially beneficial effects, which were able to prevent malignancies and decrease tumor growth. Some studies have even shown increased survival in cancer patients, reduced side effects of cytotoxic treatments, and intensified efficacy of cancer therapies. Although the biological mechanisms of KD are not well understood, it has been reported that KD may affect DNA methylation by modulating the expression of crucial genes involved in tumor survival and proliferation. However, there are many considerations to take into account to use ketotherapy in cancer, such as epigenetic mark, type of cancer, immunological and metabolic state or microbiota profile. In this review, we argue about ketotherapy as a potential strategy to consider as coadjuvant of cancer therapy. We will focus on mainly epigenetic mechanisms and dietary approach that could be included in the current clinical practice guidelines.

Influence of a Low-Carbohydrate High-Fat Diet on Peritoneal Inflammation, Cancer-Associated Lymphocytes, and Survival in a Murine Carcinomatous Peritonitis Model

BACKGROUND

Low-carbohydrate high-fat diets (LCHFDs) are thought to be beneficial for metabolic support in patients with advanced cancer. However, whether LCHFDs affect the progression of carcinomatous peritonitis (CP) remains unclear. Our study examined the influence of a lard-based LCHFD on host immunity and survival in a murine CP model.

METHODS

Mice were fed either a normal diet (ND) or an LCHFD ad libitum. On day 7, Panc02 cancer cells were inoculated intraperitoneally. Mice were killed on days 7, 21, and 35, and cytokine levels in the peritoneal fluid, as well as the number and phenotypes of peritoneal, splenic, and tumor-infiltrating lymphocytes were measured. Survival studies were performed with both ad libitum and isocaloric feeding in other sets of mice.

RESULTS

The levels of all cytokines significantly increased in the LCHFD group compared with those in the ND group on day 21. The tumor necrosis factor α and interleukin-10 levels were higher in the LCHFD group than in the ND group on day 35. In the LCHFD group, the regulatory T-cell (Treg) number was significantly higher in the peritoneal cavity and tumor. The survival times were worse in the LCHFD group than in the ND group.

CONCLUSION

The ad libitum, lard-based LCHFD feeding of CP mice increases the peritoneal cytokine levels, which may reduce splenic, anticancer lymphocytes and increase the number of Tregs in the peritoneal cavity and tumor. The detrimental effects of LCHFD are linked to dietary composition rather than overfeeding.

A review of nutrition and dietary interventions in oncology

The complex cellular mechanisms and inter-related pathways of cancer proliferation, evasion, and metastasis remain an emerging field of research. Over the last several decades, nutritional research has prominent role in identifying emerging adjuvant therapies in our fight against cancer. Nutritional and dietary interventions are being explored to improve the morbidity and mortality for cancer patients worldwide. In this review, we examine several dietary interventions and their proposed mechanisms against cancer as well as identifying limitations in the currently available literature. This review provides a comprehensive review of the cancer metabolism, dietary interventions used during cancer treatment, anti metabolic drugs, and their impact on nutritional deficiencies along with a critical review of the following diets: caloric restriction, intermittent fasting, ketogenic diet, Mediterranean diet, Japanese diet, and vegan diet.

Exploring the Feasibility and Effects of a Ketogenic Diet in Patients With CNS Malignancies: A Retrospective Case Series

Background: Recently, the ketogenic diet has been proposed as an adjunct treatment for a range of medical conditions including weight loss, diabetes, cancer, and neurodegenerative diseases. Because malignant CNS tumors are highly dependent on glucose, the use of a ketogenic diet as an adjunct therapy is currently being explored. This case series summarizes our experience implementing a ketogenic diet for patients with CNS malignancies.

Methods: Patients diagnosed with CNS malignancies following a ketogenic diet were identified between 2015 and 2017. Malignancies included confirmed diagnoses of glioblastoma (GBM), astrocytoma, or oligodendroglioma. With guidance from a registered dietitian, ketone levels, glucose levels, and weight were regularly collected for several patients along with patient-reported symptoms and adverse effects. Interested patients were asked to follow a 3:1 ketogenic diet for 120 days. The ketogenic diet is a high-fat, moderate protein, and very low carbohydrate diet, where patients limited carbohydrate intake to ≤20 g per day. Brain imaging was reviewed. A series of descriptive analyses were conducted.

Results: The ketogenic diet was initiated in 12 patients of which 8 patients contributed data on their blood glucose and ketone levels. The majority of patients were male (n = 10) with a median age of 45 (range 32–62). Diagnoses included GBM (n = 6), grade 2/3 astrocytomas (n = 5) and one patient with a grade 2 spinal cord astrocytoma. Ten of the 12 patients were receiving concurrent treatment; two received supportive care only. The majority of patients with evaluable data (n = 8) maintained ketone levels above 0.5 mM for the duration of 120-day period. Ketone levels generally increased from baseline while glucose levels and BMI decreased. Overall, patients reported improved symptoms over the course of the diet. Imaging also suggested improved disease control and reduction in vasogenic edema.

Conclusion: Taking advantage of a tumor’s metabolic inflexibility can have a positive impact on patients, particularly those with CNS malignancies. More structured and statistically planned clinical trials are needed to determine the margin of impact of a ketogenic diet.

Gut bacteria signaling to mitochondria in intestinal inflammation and cancer

The gastrointestinal microbiome plays a pivotal role in physiological homeostasis of the intestine as well as in the pathophysiology of diseases including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). Emerging evidence suggests that gut microbiota signal to the mitochondria of mucosal cells, including epithelial cells and immune cells. Gut microbiota signaling to mitochondria has been shown to alter mitochondrial metabolism, activate immune cells, induce inflammasome signaling, and alter epithelial barrier function. Both dysbiosis of the gut microbiota and mitochondrial dysfunction are associated with chronic intestinal inflammation and CRC. This review discusses mitochondrial metabolism of gut mucosal cells, mitochondrial dysfunction, and known gut microbiota-mediated mitochondrial alterations during IBD and CRC.

Modulation of Cellular Biochemistry, Epigenetics and Metabolomics by Ketone Bodies. Implications of the Ketogenic Diet in the Physiology of the Organism and Pathological States

Ketone bodies (KBs), comprising β-hydroxybutyrate, acetoacetate and acetone, are a set of fuel molecules serving as an alternative energy source to glucose. KBs are mainly produced by the liver from fatty acids during periods of fasting, and prolonged or intense physical activity. In diabetes, mainly type-1, ketoacidosis is the pathological response to glucose malabsorption. Endogenous production of ketone bodies is promoted by consumption of a ketogenic diet (KD), a diet virtually devoid of carbohydrates. Despite its recently widespread use, the systemic impact of KD is only partially understood, and ranges from physiologically beneficial outcomes in particular circumstances to potentially harmful effects. Here, we firstly review ketone body metabolism and molecular signaling, to then link the understanding of ketone bodies’ biochemistry to controversies regarding their putative or proven medical benefits. We overview the physiological consequences of ketone bodies’ consumption, focusing on (i) KB-induced histone post-translational modifications, particularly β-hydroxybutyrylation and acetylation, which appears to be the core epigenetic mechanisms of activity of β-hydroxybutyrate to modulate inflammation; (ii) inflammatory responses to a KD; (iii) proven benefits of the KD in the context of neuronal disease and cancer; and (iv) consequences of the KD’s application on cardiovascular health and on physical performance.

Potentially functional genetic variants in PLIN2, SULT2A1 and UGT1A9 genes of the ketone pathway and survival of nonsmall cell lung cancer

The ketone metabolism pathway is a principle procedure in physiological homeostasis and induces cancer cells to switch between glycolysis and oxidative phosphorylation for energy production. We conducted a two-phase analysis for associations between genetic variants in the ketone metabolism pathway genes and survival of nonsmall cell lung cancer (NSCLC) by analyzing genotyping data from two published genome-wide association studies (GWASs). In the discovery, we used a genotyping dataset from the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial in the multivariable Cox proportional hazards regression analysis. We used Bayesian false discovery probability (≤0.80) for multiple testing correction to evaluate associations between 25,819 (2,176 genotyped and 23,643 imputed) single-nucleotide polymorphisms (SNPs) in 162 genes and survival of 1,185 NSCLC patients. Subsequently, we validated the identified significant SNPs with an additional 984 NSCLC patients from the Harvard Lung Cancer Susceptibility GWAS study. Finally, we found that three independent and potentially functional SNPs in three different genes (i.e., PLIN2 rs7867814 G>A, SULT2A1 rs2547235 C>T and UGT1A9 rs2011404 C>T) were independently associated with risk of death from NSCLC, with a combined hazards ratio of 1.22 [95% confidence interval = 1.09-1.36 and p = 0.0003], 0.82 (0.74-0.91 and p = 0.0002) and 1.21 (1.10-1.33 and p = 0.0001), respectively. Additional expression quantitative trait loci analysis found that the survival-associated PLIN2 rs7867814 GA + AA genotypes, but not the genotypes of other two SNPs, were significantly associated with increased mRNA expression levels (p = 0.005). These results indicated that PLIN2 variants may be potential predictors of NSCLC survival through regulating the PLIN2 expression.

Keto microbiota: A powerful contributor to host disease recovery

Gut microbiota (GM) is a key contributor to host metabolism and physiology. Data generated on comparing diseased and healthy subjects have reported changes in the GM profile between both health states, suggesting certain bacterial composition could be involved in pathogenesis. Moreover, studies reported that reshaping of GM could contribute actively to disease recovery. Interestingly, ketogenic diets (KD) have emerged recently as new economic dietotherapeutic strategy to combat a myriad of diseases (refractory epilepsy, obesity, cancer, neurodegenerative diseases…). KD, understood in a broad sense, refers to whatever dietetic approximation, which causes physiological ketosis. Therefore, high fat-low carbs diets, fasting periods or caloric restriction constitute different strategies to produce an increase of main ketones bodies, acetoacetate and β-hydroxybutyrate, in blood. Involved biological mechanisms in ketotherapeutic effects are still to be unravelled. However, it has been pointed out that GM remodelling by KD, from now on "keto microbiota", may play a crucial role in patient response to KD treatment. In fact, germ-free animals were resistant to ketotherapeutic effects; reinforcing keto microbiota may be a powerful contributor to host disease recovery. In this review, we will comment the influence of gut microbiota on host, as well as, therapeutic potential of ketogenic diets and keto microbiota to restore health status. Current progress and limitations will be argued too. In spite of few studies have defined applicability and mechanisms of KD, in the light of results, keto microbiota might be a new useful therapeutic agent.

Research Evidence on High-Fat Diet-Induced Prostate Cancer Development and Progression

Although recent evidence has suggested that a high-fat diet (HFD) plays an important role in prostate carcinogenesis, the underlying mechanisms have largely remained unknown. This review thus summarizes previous preclinical studies that have used prostate cancer cells and animal models to assess the impact of dietary fat on prostate cancer development and progression. Large variations in the previous studies were found during the selection of preclinical models and types of dietary intervention. Subcutaneous human prostate cancer cell xenografts, such as LNCaP, LAPC-4, and PC-3 and genetic engineered mouse models, such as TRAMP and Pten knockout, were frequently used. The dietary interventions had not been standardized, and distinct variations in the phenotype were observed in different studies using distinct HFD components. The use of different dietary components in the research models is reported to influence the effect of diet-induced metabolic disorders. The proposed underlying mechanisms for HFD-induced prostate cancer were divided into (1) growth factor signaling, (2) lipid metabolism, (3) inflammation, (4) hormonal modulation, and others. A number of preclinical studies proposed that dietary fat and/or obesity enhanced prostate cancer development and progression. However, the relationship still remains controversial, and care should be taken when interpreting the results in a human context. Future studies using more sophisticated preclinical models are imperative in order to explore deeper understanding regarding the impact of dietary fat on the development and progression of prostate cancer.

Ketone-Based Metabolic Therapy: Is Increased NAD+ a Primary Mechanism?

The ketogenic diet’s (KD) anticonvulsant effects have been well-documented for nearly a century, including in randomized controlled trials. Some patients become seizure-free and some remain so after diet cessation. Many recent studies have explored its expanded therapeutic potential in diverse neurological disorders, yet no mechanism(s) of action have been established. The diet’s high fat, low carbohydrate composition reduces glucose utilization and promotes the production of ketone bodies. Ketone bodies are a more efficient energy source than glucose and improve mitochondrial function and biogenesis. Cellular energy production depends on the metabolic coenzyme nicotinamide adenine dinucleotide (NAD), a marker for mitochondrial and cellular health. Furthermore, NAD activates downstream signaling pathways (such as the sirtuin enzymes) associated with major benefits such as longevity and reduced inflammation; thus, increasing NAD is a coveted therapeutic endpoint. Based on differential NAD⁺ utilization during glucose- vs. ketone body-based acetyl-CoA generation for entry into the tricarboxylic cycle, we propose that a KD will increase the NAD⁺/NADH ratio. When rats were fed ad libitum KD, significant increases in hippocampal NAD⁺/NADH ratio and blood ketone bodies were detected already at 2 days and remained elevated at 3 weeks, indicating an early and persistent metabolic shift. Based on diverse published literature and these initial data we suggest that increased NAD during ketolytic metabolism may be a primary mechanism behind the beneficial effects of this metabolic therapy in a variety of brain disorders and in promoting health and longevity.

A ketogenic diet supplemented with medium-chain triglycerides enhances the anti-tumor and anti-angiogenic efficacy of chemotherapy on neuroblastoma xenografts in a CD1-nu mouse model

Neuroblastoma (NB) is a pediatric malignancy characterized by a marked reduction in aerobic energy metabolism. Recent preclinical data indicate that targeting this metabolic phenotype by a ketogenic diet (KD), especially in combination with calorie restriction, slows tumor growth and enhances metronomic cyclophosphamide (CP) therapy of NB xenografts. Because calorie restriction would be contraindicated in most cancer patients, the aim of the present study was to optimize the KD such that the tumors are sensitized to CP without the need of calorie restriction. In a NB xenograft model, metronomic CP was combined with KDs of different triglyceride compositions and fed to CD1-nu mice ad libitum. Metronomic CP in combination with a KD containing 8-carbon medium-chain triglycerides exerted a robust anti-tumor effect, suppressing growth and causing a significant reduction of tumor blood-vessel density and intratumoral hemorrhage, accompanied by activation of AMP-activated protein kinase in NB cells. Furthermore, the KDs caused a significant reduction in the serum levels of essential amino acids, but increased those of serine, glutamine and glycine. Our data suggest that targeting energy metabolism by a modified KD may be considered as part of a multimodal treatment regimen to improve the efficacy of classic anti-NB therapy.